- Email: [email protected]
The manifestation of the pyrogenic factor in the geosystem dynamics of the southwestern Baikal region
Geography and Natural Resources 29 (2008) 156–162
The manifestation of the pyrogenic factor in the geosystem dynamics of the southwestern Baikal region E. G. Suvorov *, N. I. Novitskaya, A. D. Kitov, and E. V. Maksyutova Institute of Geography SB RAS, Irkutsk Received 20 December 2006
Abstract The manifestation conditions for the pyrogenic factor in the geosystem dynamics of the southwestern Baikal region are outlined. The distribution of forest fires in the territory, and the conditions of their occurrence and spread are considered. The need to put territorially differentiated fire-control measures into effect is substantiated. Keywords: states of geosystems, forest fires, climatic conditions, fire-hazardous season, hotspots, classes of natural fire hazard.
Introduction
Formulation of the problem
The character of the natural conditions in the southwestern Baikal region (mountain relief, climate variation, and diversity of vegetation cover) are the cause of the differentiated (with a high degree of contrast) landscape structure. Local differences in the distribution of atmospheric precipitation and heat due to the complicated landforms on the territory immediately surrounding Lake Baikal are responsible for successions and co-existence of the steppe, meadow-bog, sub-taiga, mountain-taiga, sub-golets and golets geosystems with a different degree of resistance and stabilization of heir structure. Territorially, mountain-taiga geosystems are dominant. The altitudinal-zonal patterns are differentiated according to the conditions of optimal, limited and reduced development. The contrasts of natural diversity of the territory are enhanced by the mixed character of succession-dynamical states of geosystems arising as a consequence of different impact factors. The most important of them is the pyrogenic factor. The conditions of its manifestation are determined by physical-geographical characteristics of the territory as well as by the character of anthropogenic activity.
Forest fire spread in the Slyudyanka district forestry and Pribaikalsky National Park (PNP) is used here as an approach in assessing the manifestation of the pyrogenic factor depending on the properties of landscape structure, and on the state of its geosystems. The territory encompassed by these economic entities lies within the Southern and Western Baikal region, hereinafter referred to as the southwestern Baikal region, has rather varied natural conditions. Also, long-term statistical data on fire occurrence and spread are available for this region.
Corresponding author. E-mail addresses: [email protected] (E. G. Suvorov), [email protected] (A. D. Kitov) *
The objects of investigation According to small-scale [1] and more fractional [2, 3] physical-geographical regionalization, most of the study territory is represented by the Pre-Baikalian golets-mountain taiga and depression province of the Baikal-Dzhugdzhurskaya mountain-taiga physical-geographical region within which there are two identifiable landscape districts with a different territorial proportion of golets-mountain-taiga, mountain-taiga and sub-taiga geosystems. The sub-province of the Lake Baikal hollow is characterized by four coastal landscape districts with a different proportion of taiga submontane-plain, mountain-taiga, mountain-sub-taiga and submontane-steppe geosystems. The South-Siberian mountain country is represented by the Oka-Sayan golets-mountaintaiga province with the middle-mountain mountain-taiga district. The Upper-Angara bog-steppe and sub-taiga sub-
Copyright © 2008 IG SB, Siberian Branch of RAS. Published by Elsevier B.V. All rights reserved doi:10.1016/j.gnr.2008.06.010
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
montane region with submontane-plain sub-taiga district; and the Khamar-Daban mountain-taiga-depression province with five landscape districts with a different proportion of steppe-sub-taiga, mountain-taiga and golets-mountain-taiga geosystems. The aforementioned regional physical-geographical subdivisions correspond to large geological-geomorphological structures. Landscape districts are identified from a full set of physical-geographical factors taking into account the differentiating landscape-forming properties of all components sof geosystems and are characterized by a peculiar kind of territorial landscape structures. The existence on this territory of mosaics of successional-dynamical states of geosystems (from early stages of regeneration following external impacts with grassy pine and small-leaved plant communities to equifinal stages with dark-coniferous plant communities) is evidence of the varied and rather dynamical structure of geosystem states. Research results and discussion On the basis of the averaged estimates of the fire hazard, we can identify on the territory the South-Baikalian pyrological district with the number of fires per season ranging from 2.1 to 7.0 or larger for 100 thou ha, and the West-Baikalian district with the number of fires varying from 0.1 to 7.0. The general description of the pyrological districts included the estimated data on the relief (altitude, and ruggedness), climate (the seasonal dynamics of atmospheric precipitation, and the forest-fire index of dry periods), vegetation, and combustibility [4]. It is thought that the possibility of forest fires originating is influenced primarily by meteorological conditions [5-8]. They determine the potential hazard that combustible plant materials get ready for ignition. A critical index determining the formation of the climatic regime is the sunshine duration. In the southern and middle part of Lake Baikal, it is 2000-2400 hours/year [9]. The maximum values of total radiation under moderate conditions of cloudiness (439 (439.6 x 104 – 460.5 · 104 kJ/m2) also correspond to the middle and southern parts of the lake’s western coast, which is larger by 20% when compared with the areas in southern Siberia in the same latitudes. The positive vales of radiation balance for Baikal reach 167.5 x 104 kJ/m2. For the lake’s coast there is a very strong variation (from 30 to 70%) of the values of heat that goes into evaporation because of the large differences in humidification of the territory. The index of dryness in some areas along the coast of Middle Baikal is 1.5-2.5, in agreement with the index for the steppes of the temperate zone [10]. Since the climatic conditions are not uniform, the territory can be divided into areas that are distinguished by the regime and distribution of climatic elements, and by the character of seasonal weather conditions. Because of lack of weather stations, the boundaries of a physical-geographical classification are used to separate out the hierarchical units of climatic differentiation. According to N. P. Ladeishchik-
157
ov [11], the hollow and the lake itself are assigned to the Baikal lake-hollow sub-province of the Baikalian province. The sub-province is divided into three climatic districts: the Southern, Middle and Northern districts. Within the districts, climatic areas and smaller taxonomic units were identified, which correspond to the local meso- and micro-climatic regimes of the shores determined by local climate-formation factors. The special character of the correlations of numerical indices of heat and moisture with those for the nearby territory of southern East Siberia made it possible to identify for this territory the following types of climate [12]: dry climate with moderately warm summers, and moderately cold and moderately snowy (or snow-deficient on the coast) winters; moist climate with moderately warm summers, and moderately cold and snow-deficient winters on the coast, and moderately snowy (on the slopes) winters; excessively moist climate with cold summers, and cold, snow-deficient winters. According to the humidification conditions at the most fire-hazardous period, the territory under consideration is differentiated into types ranging from dry in the north to excessively moist in the south, in the Khamar-Daban mountains. The beginning of a fire-hazardous season is determined from long-term data on the onset time of first fires in the spring. Typically they are associated with natural-climatic conditions, and with the presence of a fire source in forest. According to the PNP report data [13], fires during 19781987 occurred from April to September. Over the course of a year, the amount of atmospheric solid precipitation makes up 4-7% and 6-14%, respectively, on the western and southern coast of Baikal (the Khuzhir and Sarma stations). The earliest snow cover (in early September – end of August, and in some years even in mid-August) is observed in the altitudinal zones of Khamar-Daban and persists for the longest period – till June, and sometimes till July. A total of about 250 days with snow cover are recorded within a year. On Middle Baikal and in the south, it appears in the first ten-day period of November and in mid-October, respectively, and it disappears in late April – early May [14]. In some winters there can occur significant deviations from the mean dates. The greatest of them reach 14-31 days. Fires can occur in May, immediately after the snow cover disappears. On the western coast of Baikal (the Khuzhir and Sarma stations) the air temperature in May is 5.2-5.5 °C, with its maxima corresponding to July (14.7-15.4 °C (Table 1); the sum of temperatures higher than 10 °C (biologically active) is 1227-1300°. The southern May air temperatures vary over a wide range: 4.9-6.3 °C, and in the mountainous areas (the Khamar-Daban station) they are the lowest, as low as 2.6°C. The air temperature in July reaches 15.3 °C. The sums of temperatures higher than 10 °C are 934-1263, and in the mountainous areas they are 839 [14]. The wind regime in the Baikal region has its distinctive features. The high mountain ranges surrounding the lake prevent, to some extent, the external air currents from penetrating into the lake’s hollow thus giving rise to local circula-
158
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
Table 1 Climatic indices in the fire-hazardous months for the southwestern Baikal region, according to [14]
June
July
August
September
May
Weather stations
April
Fire-hazardous months
11.2
14.7
14.0
8.4
Monthly man air temperature, оС Khuzhir
-1.4
5.2
Sarma
-0.8
5.5
11.5
15.4
14.4
8.9
Bol. Goloustnoye
-0.6
5.4
10.4
13.5
14.0
8.3
Angara source
-1.1
4.9
9.4
12.9
12.8
7.6
Slyudyanka
-0.3
6.0
11.8
15.3
14.2
7.8
Khamar-Daban
-4.0
2.6
10.0
12.7
10.7
3.5
Amount of precipitation, mm Khuzhir
7
13
28
50
60
17
Sarma
5
10
29
53
55
18
Bol. Goloustnoye
13
21
46
64
58
26
Angara source
12
29
64
84
77
40
Slyudyanka
16
37
83
127
106
52
Khamar-Daban
85
128
211
262
212
141
Number of days with relative air humidity less than 30% Bol. Goloustnoye
4.0
3.7
1.0
0.1
0.04
0.3
Slyudyanka
1.9
1.8
0.3
0.0
0.0
0.2
Khamar-Daban
7.0
6.8
2.4
0.4
0.5
1.6
tion processes in it. Thus, sharply pronounced breezes and mountain-valley winds are observed in the vicinity the lake’s shores nearly throughout a year [15]. On the western coast of Middle Baikal the yearly mean wind velocity reaches 3 m/s, and the highest velocity of 4 m/s is observed in April-May. In a fire-hazardous season, the wind velocity is different, but the highest velocity is recorded in May (4.3 m/s); at the Bolshoye Goloustnoye the highest velocity is observed in September (4.5 m/s). In the mountains (the Khamar-Daban station), the yearly mean wind velocity is lower, or 1.6 m/s, and the highest velocity of 1.6 m/s is observed in April-June [16]. High wind velocities larger than or equal to 15 m/s are observed everywhere. Thus, the maximum mean number of days with >15 m/s wind velocities at the Bolshoye Goloustnoye station is 4.1 days in May, with this number being twice as small in July-August. A total of about 18 such days correspond to the fire-hazardous months. The values of relative air humidity in April-May are lowest and constitute 54-56% in the middle part of Baikal’s western coast (the Khuzhir and Sarma stations), and they make up 59-65% in the southern part, and in the mountains. From July to August the relative air humidity increases to 74-80% and decreases to 65-77% in September [14].
The diurnal amplitudes of the value of relative air humidity on Baikal’s coast constitute 9-18%. From April to September the range of humidity fluctuation broadens to include the possible occurrence of lower values. The largest number of dry days (with 30% or lower humidity) is observed in April, while in July-August the number of dry days decreases (from 0 to 0.1), and in September it increases to 0.3 on the western coast of the Southern Baikal region, and to 1.6 in the mountains (see Table 1). In some years the number of dry days deviates considerably from the above values. A dry period can last for more tan ten days continuously or with a short break [14], which promotes the occurrence of fires. The regime of atmospheric precipitation is determined largely by the atmospheric circulation whose behavior in a warm season is governed by enhanced cyclonic activity, and by atmospheric precipitation amounting to 65-85% pr annum. For the territory under consideration the amount of precipitation varies over a rather wide range, from 182 to 1293 mm [14]. The least amounts are observed on Olkhon Island, and the largest amounts are recorded on the slopes of the Khamar-Daban Range facing Baikal, in the southwestern part of the lake. In a fire-hazardous season, the smallest amount of precipitation corresponds to April-May. A maximum is observed in August on the territory of the middle part of the Baikal region, 55-60 mm, and in July on the western coast in the Southern Baikal region, 64 mm, with 262 mm in the mountains. The amount of precipitation decreases in September throughout the territory involved. It is difficult to investigate the meteorological factors for local (across time and space) critical pyrogenic situations on the territory of the southwestern Baikal region because of the insufficient number of weather stations; the problem is compounded by a need for special-purpose meteorological observations. According to forestry data on the occurrence of fires within the PNP (before it was granted the status of a specially protected territory) [13], with the area of lands occupied by forest resources totaling 475.6 thou ha, the forested territory was 278.3 thou ha (58.5%) in area, including 224 thou ha (or 80.4%) occupied by coniferous species (pine, larch, and Siberian stone pine). Forbs, Mongolian tea and ledum types were dominant. The area occupied by the most fire-hazardous plant communities (undergrowth of conifers and other kinds of trees) was 35.8 thou ha, or 12.9% of forested lands. The naturally occurring fie hazard was estimated having regard to the typological structure of forests using a five-point scale due to I. S. Melekhov [17] at a level of a medium class, II, 4. In doing this, a forest management compartment was used as the taxonomic fire unit (Table 2). The scale that was refined and extended by I. V. Ovsyannikov [18] is currently used in anti-fire forest management. The categories of forests are distributed in it by classes of fire hazard with due regard for the priority of fire maturing, and for the possible occurrence of strong fires. Class II of hazard is the commonest. It includes cowberry pine forests, espe-
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
159
Table 2 Distribution of lands of the PNP forest resources in classes of natural fire hazard, thou ha /% Classes of natural fire hazard
Area of lands of the forest resources,
I
II
III
IV
V
Mean class
475.6/100
3.1/17.5
186.6/39.2
125.7/26.4
79.5/16.8
0.7/0.1
II, 4
cially with the inclusion of pine undergrowth or a layer consisting of juniper with density above moderate; larch forests with undergrowth of dwarf Siberian pine trees; cembretums with the inclusion of dense undergrowth, and uneven-aged forests with vertical closure [19]. The fire hazard is assigned one class higher for coniferous forests, the structure or other characteristics of which promotes a change of a forest fire into a crown fire (dense tall undergrowth of the conifers, debris-strewn forests, etc.); for small areas of forest along waterless valleys surrounded by localities with considerable combustibility; for forested areas adjacent to public roads, and to railroads (when steam locomotive traction is used) in the immediate vicinity of wood enterprises with fire-causing potential. Ground fires in this case are possible throughout a fire-hazardous season, while crown fires can occur at periods of fire maxima. The practical significance of this categorization notwithstanding, it is pointed out that class IV of hazard includes
not only poorly combustible sphagnum and long-moss pine forests but also all grassy forests, although disastrous fires in them are not uncommon in the spring and autumn in southern Siberia. The scale includes, in addition to the s of the vegetation, the attribute of proximity to roads, which gives no way of making particular numerical estimates. The development of other typologies is underway [8]. On the other hand, these scheme permits a more detailed differentiation of the territory with regards to the pyrogenic hazard when the conditions are assessed not in terms of forestry units but according to the types of homogeneous natural condition, and this is possible by use of landscape-typological mapping. For the purpose of making such an estimate, an analysis was made of the data on fire spread in the Pribaikalsky National Park. A total of 137 forest fires was recorded in the area of 2750.1 ha for a ten-year period (1978-1987), and the area of a single fire averaged 20.1 ha (Table 3). Table 3
Distribution of the number and area (ha) of forest fires during fire-hazardous seasons of 1978-1987, according to [13}
Year
April
1978
3 48.1
1979
-
1980
-
1981 1982
1 0.6 2 3.0
May 5 15.5 8 147.8
10 1047.9
3 3.4
-
-
-
-
-
-
-
1 1.0
1 0.3
1 2.0
-
-
-
-
-
-
-
-
4
1 5.0
-
-
-
-
-
-
-
-
-
3 1.0
1984
-
-
1985
-
1986
-
%
Number of fires with unac-counted -for area
1 1.6 3 5.2
3 3.0
Total
3 1068.0
3 121.2 5 5.5
September
August
-
-
4 3.5 10 55.2 7.3 2.0
5 4.2 3 1.7
July
-
1983
1987
June
5 99.3 3 2.5 19 161.3 60 1397.4 43.8 50.8
1 0.7 2 21.5 23 1109.6 16.8 40.3
3 0.4 19 134.9 13.9 4.9
Note. Numerator – number of fires, denominator – spread area.
16 41.0 11.7 1.5
1 10.0 2 12.0 1.4 0.4
1 2 7 5.1
Total 19 192.4 16 55
Mean area of one fire 10.1 3б.4 2.4
17 2119.8 2 3.0 8 4.6 4 10.2 5 99.3 9 14.2 30 186.7 137 2750.1 100 100
124.7 1.5 0.6 2.5 19.9 1.6 6.2 20.1
160
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
According to the relative fire incidence rate of this territory (in terms of years and the number of fires per million hectare), the territory corresponds to the gradations of the “Soyuzgiproleskhoz” scale [13] below average (from 6 to 50) and above average (from 0.5 to 1.0). The duration of a fire-hazardous season between the first and last fires is 154 days. According to the number and area of fires, the maxima of a fire-hazardous season correspond to May-June (respectively, 43.8 and 16.8% in May, and 50.8 and 40.3% in June). Typically they are ground fires, so that they mostly affect forest litter and do damage to the root system of trees with the result that the affected tree stands are doomed to die, and the problem is compounded by the fact that very thin layers of mountain soils are dominant. Forest fires are in most cases deliberately set (the proportion of “unnatural”, or man-made, fires constitute 80%), and the share of naturally occurring (cased by lightning) is 9%. Nearly every seventeenth fire (5.8%) occurs due to unknown reasons. Most of the territory is being monitored by the aircraftassisted forest fire control service. Aircraft detect 30.5% of fires, and 80% of them can be identified in an area as small as 0.5 ha (and 51% of these in an area as small as 0.1 ha), which indicates a reasonably high efficiency of this monitoring operations. Only 39.4% of fires and about one-sixth of fires with an area of about 0.5 ha, and several tens of hectares, respectively, are successfully eliminated. More than 77.9% of fires took more than 24 hours to be eliminated. For comparison, only 21 forest fires, with 16.1 ha the mean area of a single fire, were recorded on the territory of the Slyudyanka forestry district adjacent to the national park in the Southern Baikal region. The territory of the forestry district compares with the PNP – 352 thou ha; it should be noted, however, that the physical-geographical conditions, including the climatic conditions, the landscape structure, the structure of the states of geosystems [3, 12], and also the transport and residential infrastructure are different. Given the validity of the analysis of averaged estimates made for forestry districts in the case of small-scale pyrological zoning [4], it is of interest to examine the situational dynamics of fires, and the conditions o their localization. The individualities of forest fires are relatively many-sided; in this connection, an analysis was made of the database on forest fires in the Pribaikalsky National Park which we generated in electronic tables to take into account the forest fires on the park’s territory from 1995 to 2005. The database includes the place of fire occurrence (within a compartment), the date, the area, and the possible causes. Adjustment of fires to the topographic and forest-husbandry base makes it possible to analyze, in a more thorough manner and by taking into consideration the ambient properties of the territory, the favorable conditions for the occurrence and spread of fires. For analyzing the local conditions, the hotspots and the burned-over areas were superimposed on the raster layers of the topographic base, forest inventory data, and with thematic materials obtained by the Institute of Geography
SB RAS, and with space-acquired remotely sensed data for this territory from different years; the highest informational content corresponded to the Landsat ETM 2000 and 2002 images [2] which we synthesized and which were represented in seven spectral regions with a resolution of 15 m when synthesized with the eighth channel. The hotspots, which in the database correspond to a forest-husbandry compartment, were actually localized on the terrain, which is supported by field observations, and by the available remotely sensed data, with the burned-over areas are clearly interpretable – this is especially true for fresh data. For the period from 1995 to 2005, 256 fires were recorded on the territory of the PNP. Their total area was larger than 23 thou ha, and the area of a single fire averaged 90.0 ha. The number of small fires (with burned-over areas less than 0.5 ha) constituted 31% (68 events), while 69%, or 177 events, correspond to burned-out forests with an area larger than 0.5 ha; 112 events correspond to an area larger than 5 ha, and 29 events encompassed more than 200 ha. Burned-over areas measuring several thousand hectares were recorded in some years: 1117 ha in May 1996, 1400 and 1650 ha in late May and in August 1997, respectively, 1500 in May 1998, and 2 thou ha in May 2000. In subsequent years the individual territories affected by fires did not exceed 1 thou ha. The least number of fires was observed in 2001 – the area of burned-out forest was only 24.5 ha (seven events at the beginning of a fire-hazardous season). The largest territory that was affected by fires was recorded in 1997 – its area was 5709.5 ha (35 events throughout the fire-hazardous season). More than 5 thou ha underwent forest fires in 1998 and 2003. Noteworthy is the gross difference in the averaged statistical data on the number of forest fires on the same territory, with relatively identical natural conditions but at different periods: 1978-1987 and 19952005. This can be explained not only by the differences in the dynamics of climatic conditions but also by such factors and a change of the economic entity, and hence by the different attitude to the recording of forest fires as well as by the increased utilization of the territory as the touristic resource. The distribution of forest fires across the territory (see the figure) is uneven and does not show any obvious match of its differentiation by humidification in a warm season [12]. The most likely cause is the anthropogenic factor. As regards the concentration of the origins of fires, their largest number is observed near the residential zone of the settlement of Listvyanka as well as in the coastal zone adjacent to the settlements, the holiday camps as well as to the transport routes (the railroad, and motor roads of different purposes). The smallest number of fire events was recorded in 2001. The fires that were recorded only in May – early June, were creeping ground fires and seem to be associated with the anthropogenic factor, because they occurred in the neighborhoods of communities. The largest areas (in excess of 5 thou ha) were affected by fires in 1997, 1998, and 2003. The fire
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
161
The distribution of hotspots on the territory of the Pribaiklsky National Park during 1995-2005. A portion of the schematic map. 1 – stable-derivative and short-term-derivative states of geosystems with small-leaved forest; 2 – residential territories; 3 – roads of different purposes; 4 – PNP boundary. Functional zones of PNP: 5 – reserve zone, 6 – recreational utilization, 7 – services to visitors, 8 – other lands. Hotspots: 9 – large fires, 10 – small fires.
events and the fresh burned-over areas show a much more uniform distribution across the national park’s territory during the aforementioned years. The spread of large forest fires coincides with predominance of stable-derivative states of geosystems in the territorial structure. Such areas are characterized by small-leaved plant communities, as is the case with the Olkhinskoye upland. The areas of large fires in this case have their origins in the territories adjacent to the national park. The fact that there were no fires for a 10-year period in secondary structures of geosystems and that only small fires occurred is beneficial for a successful regeneration of coniferous forests, which is confirmed by the field descriptions of the states of geosystems, pointing out the regeneration of Siberian stone pine and spruce under the canopy of smallleaved trees. The strongest fires occurred in May-June. They are rather common in the presence of numerous smaller fires. The largest (strong creeping ground) fire embracing an area of 2000 ha was recorded in the last ten-day period of May 2000 along the right bank of the Cheremshanka river in the PrimorskoOnotsky mountain-taiga and sub-taiga district – it affected near-watershed and (southern exposure) slope geosystems represented by pine and small-leaved grassy forests. A natural obstacle to it in the southern part was the valley of the
Cheremshanka river; only the southern exposure slope was actually burned out. Another large fire that occurred in this same area in midMay 1998 encompassed 1150 ha. The burned-over area lies in the upper part of the Nikulikha creek valley. The fire occurred in the stable-derivative territorial structure of mountain-taiga geosystems with small-leaved grass plant communities. The fire that was recorded in May 1998 in an area of 1100 ha along the Raspopikha creek valley was localized along the path running from the Angara reservoir. An extensive burned-over locality in the Olkhinsky piedmont-elevated mountain-taiga area of the Kitoi-Angara district is clearly seen on the synthesized image from the year 2002. This area includes at least four fires that occurred in different years over the course of ten years. Specifically, a large burned-over area of 1100 ha was recorded here in May 1998. Territorially, the burned-over areas are associated with fires arriving at the boundaries of the national park from the north. The spread of fires in different years, and the secondary structure of the states of geosystems with pine and small-leaved forests indicates that fires occurred on multiple occasions. This area is bounded by valley complexes; yet, it encompasses the upper parts of the interfluves of several rivers.
162
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
In 2003, 62 fires were recorded (with the burned-over areas exceeding 5 thou ha), including nine large fires (over 200 ha each). All occurred in places visited by people on the slopes of the Yelovka, Kirpichnaya and Bolshiye Koty creek valleys, in the neighborhoods of the village of Talovka, and at 300-800 m from roads and ride swaths in middle-aged pine and small-leaved forests. The fire spread was proceeding according to the type of stable ground fire and crown fire of moderate intensity. Conclusion The distribution of fires confirms rather clearly the stable character of the structure of the states of geosystems with derivative vegetation, both immediately in the coastal zone of Lake Baikal and in the other part of the PNP. The factor of transport accessibility is also of important significance. Most of the fires correspond to May-June. Small fires are dominant in humid years, and the years of increased dryness determine a more uniform distribution of large fires. Analysis of the distribution of hotspots demonstrates that they are concentrated in secondary structures of the states of geosystems, which determines maintenance of such states over a long period of time. Thus the territory of the Pribaikalsky National Park is facing a strained fire-hazardous situation, and it can aggravate further because of the promotion of recreation. It is therefore necessary to improve anti-fire measures. The existing sitespecific diversity of conditions leading to forest fires calls for territorial differentiation of protection measures. This work was done with financial support from the Russian Foundation for Basic Research (04-05-65182, and 0505-97252). References 1. Mikheyev V. S. and Ryashchin V. A. Physical-geographical regionalization: Insert map of a scale of 1:8 000 000. In: The Landscapes in the South of East Siberia: the 1:1 500 000 Map. Moscow: GUGK, 1977. 2. Mikheyev V. S. Landscape structure. In: Nature Management and Environmental Protection in Baikal Watershed Basin. Novosibirsk: Nauka, 19990, pp. 7-29.
3. Suvorov E. G. General physical-geographical conditions of a territory. In: Ecologically Oriented Land Use Planning in the Baikal Region. The Slyudyanka District. Irkutsk: Institute of Geography SB RAS Publisher, 2002, pp. 53-58. 4. Sofronov M. A., Antropov V. F. and Volokitina A. V. The pyrological description of the vegetation within the Lake Baikal watershed basin. Geografiya i prirod. resursy, 1999, No. 2, pp. 52-58. 5. Valendik E. N. The synoptic situations that are responsible for large forest fires. In: Forest Fires and Their Consequences. Krasnoyarsk, 1985, pp. 5-12. 6. Valendik E. N. Large forest fires in Siberia. Geografiya i prirod. resursy, 1995, No. 1, pp. 85-92. 7. Kurbatsky N. P. The problem of forest fires. In: The Origination of Forest Fires. Moscow: Nauka, 1964, pp. 5-52. 8. Volokitina A. V. and Sofronov M. A. Classification and Mapping of Combustible Plant Materials. Novosibirsk: Izd-vo SO RAN, 2002, 306 p. 9. Bufal V. V. The radiation regime of the Lake Baikal hollow and its role in climate formation. In: The Climate of Lake Baikal and of the Baikal Region. Moscow, 1966, pp. 34-70. 10. The Structure and Resources of the Climate of Baikal and Neighboring Spaces. Novosibirsk: Nauka, 1977, 271 p. 11. Ladeishchikov N. P. Climate Characteristics of Large Lakes (Using Baikal as an Example). Moscow: Nauka, 1982, 135 p. 12. Trofimova I. E. Typization and mapping of the climates of the Baikal mountain-depression system. Geografiya i prirod. resursy, 2002, No. 2, pp. 53-61. 13. Anti-fire forest management: the framework master plan for the establishment of the Pribaikalsky state national park. 4695-3S. Forestry. Moscow, 1989, Book 2, vol. 4, 142 p. 14. Handbook on the USSR Climate. Leningrad: Gidrometeoizdat, 1966, 1968, issue 22, pt. 2, 359 p.; pt. 4 , 278 p. 15. Characteristics of the Hydrometeorological Regime of Lake Baikal and Its Influence on Fleet Operations. Irkutsk, 1967, 98 p. 16. Applied-Science Handbook on the USSR Climate. Long-term Data. Ser. 3. Leningrad: Gidrometeoizdat, 1991, pt. 1-6, issue 22, 604 p. 17. Melekhov I. S. Nature of Forests and Forest Fires. Arkhangelsk: OGIZ, 1947, 60 p. 18. Ovsyanikov I. V. Anti-fire Forest Management. Moscow: Lesnaya promyshlennost, 1978, 112 p. 19. Collection of Departmental Acts on Forestry for USSR Gosleskhoz for 1966-1976. Moscow: Gosleskhoz, 1979, 206 p. 20. http//www.landsat.org.
The manifestation of the pyrogenic factor in the geosystem dynamics of the southwestern Baikal region E. G. Suvorov *, N. I. Novitskaya, A. D. Kitov, and E. V. Maksyutova Institute of Geography SB RAS, Irkutsk Received 20 December 2006
Abstract The manifestation conditions for the pyrogenic factor in the geosystem dynamics of the southwestern Baikal region are outlined. The distribution of forest fires in the territory, and the conditions of their occurrence and spread are considered. The need to put territorially differentiated fire-control measures into effect is substantiated. Keywords: states of geosystems, forest fires, climatic conditions, fire-hazardous season, hotspots, classes of natural fire hazard.
Introduction
Formulation of the problem
The character of the natural conditions in the southwestern Baikal region (mountain relief, climate variation, and diversity of vegetation cover) are the cause of the differentiated (with a high degree of contrast) landscape structure. Local differences in the distribution of atmospheric precipitation and heat due to the complicated landforms on the territory immediately surrounding Lake Baikal are responsible for successions and co-existence of the steppe, meadow-bog, sub-taiga, mountain-taiga, sub-golets and golets geosystems with a different degree of resistance and stabilization of heir structure. Territorially, mountain-taiga geosystems are dominant. The altitudinal-zonal patterns are differentiated according to the conditions of optimal, limited and reduced development. The contrasts of natural diversity of the territory are enhanced by the mixed character of succession-dynamical states of geosystems arising as a consequence of different impact factors. The most important of them is the pyrogenic factor. The conditions of its manifestation are determined by physical-geographical characteristics of the territory as well as by the character of anthropogenic activity.
Forest fire spread in the Slyudyanka district forestry and Pribaikalsky National Park (PNP) is used here as an approach in assessing the manifestation of the pyrogenic factor depending on the properties of landscape structure, and on the state of its geosystems. The territory encompassed by these economic entities lies within the Southern and Western Baikal region, hereinafter referred to as the southwestern Baikal region, has rather varied natural conditions. Also, long-term statistical data on fire occurrence and spread are available for this region.
Corresponding author. E-mail addresses: [email protected] (E. G. Suvorov), [email protected] (A. D. Kitov) *
The objects of investigation According to small-scale [1] and more fractional [2, 3] physical-geographical regionalization, most of the study territory is represented by the Pre-Baikalian golets-mountain taiga and depression province of the Baikal-Dzhugdzhurskaya mountain-taiga physical-geographical region within which there are two identifiable landscape districts with a different territorial proportion of golets-mountain-taiga, mountain-taiga and sub-taiga geosystems. The sub-province of the Lake Baikal hollow is characterized by four coastal landscape districts with a different proportion of taiga submontane-plain, mountain-taiga, mountain-sub-taiga and submontane-steppe geosystems. The South-Siberian mountain country is represented by the Oka-Sayan golets-mountaintaiga province with the middle-mountain mountain-taiga district. The Upper-Angara bog-steppe and sub-taiga sub-
Copyright © 2008 IG SB, Siberian Branch of RAS. Published by Elsevier B.V. All rights reserved doi:10.1016/j.gnr.2008.06.010
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
montane region with submontane-plain sub-taiga district; and the Khamar-Daban mountain-taiga-depression province with five landscape districts with a different proportion of steppe-sub-taiga, mountain-taiga and golets-mountain-taiga geosystems. The aforementioned regional physical-geographical subdivisions correspond to large geological-geomorphological structures. Landscape districts are identified from a full set of physical-geographical factors taking into account the differentiating landscape-forming properties of all components sof geosystems and are characterized by a peculiar kind of territorial landscape structures. The existence on this territory of mosaics of successional-dynamical states of geosystems (from early stages of regeneration following external impacts with grassy pine and small-leaved plant communities to equifinal stages with dark-coniferous plant communities) is evidence of the varied and rather dynamical structure of geosystem states. Research results and discussion On the basis of the averaged estimates of the fire hazard, we can identify on the territory the South-Baikalian pyrological district with the number of fires per season ranging from 2.1 to 7.0 or larger for 100 thou ha, and the West-Baikalian district with the number of fires varying from 0.1 to 7.0. The general description of the pyrological districts included the estimated data on the relief (altitude, and ruggedness), climate (the seasonal dynamics of atmospheric precipitation, and the forest-fire index of dry periods), vegetation, and combustibility [4]. It is thought that the possibility of forest fires originating is influenced primarily by meteorological conditions [5-8]. They determine the potential hazard that combustible plant materials get ready for ignition. A critical index determining the formation of the climatic regime is the sunshine duration. In the southern and middle part of Lake Baikal, it is 2000-2400 hours/year [9]. The maximum values of total radiation under moderate conditions of cloudiness (439 (439.6 x 104 – 460.5 · 104 kJ/m2) also correspond to the middle and southern parts of the lake’s western coast, which is larger by 20% when compared with the areas in southern Siberia in the same latitudes. The positive vales of radiation balance for Baikal reach 167.5 x 104 kJ/m2. For the lake’s coast there is a very strong variation (from 30 to 70%) of the values of heat that goes into evaporation because of the large differences in humidification of the territory. The index of dryness in some areas along the coast of Middle Baikal is 1.5-2.5, in agreement with the index for the steppes of the temperate zone [10]. Since the climatic conditions are not uniform, the territory can be divided into areas that are distinguished by the regime and distribution of climatic elements, and by the character of seasonal weather conditions. Because of lack of weather stations, the boundaries of a physical-geographical classification are used to separate out the hierarchical units of climatic differentiation. According to N. P. Ladeishchik-
157
ov [11], the hollow and the lake itself are assigned to the Baikal lake-hollow sub-province of the Baikalian province. The sub-province is divided into three climatic districts: the Southern, Middle and Northern districts. Within the districts, climatic areas and smaller taxonomic units were identified, which correspond to the local meso- and micro-climatic regimes of the shores determined by local climate-formation factors. The special character of the correlations of numerical indices of heat and moisture with those for the nearby territory of southern East Siberia made it possible to identify for this territory the following types of climate [12]: dry climate with moderately warm summers, and moderately cold and moderately snowy (or snow-deficient on the coast) winters; moist climate with moderately warm summers, and moderately cold and snow-deficient winters on the coast, and moderately snowy (on the slopes) winters; excessively moist climate with cold summers, and cold, snow-deficient winters. According to the humidification conditions at the most fire-hazardous period, the territory under consideration is differentiated into types ranging from dry in the north to excessively moist in the south, in the Khamar-Daban mountains. The beginning of a fire-hazardous season is determined from long-term data on the onset time of first fires in the spring. Typically they are associated with natural-climatic conditions, and with the presence of a fire source in forest. According to the PNP report data [13], fires during 19781987 occurred from April to September. Over the course of a year, the amount of atmospheric solid precipitation makes up 4-7% and 6-14%, respectively, on the western and southern coast of Baikal (the Khuzhir and Sarma stations). The earliest snow cover (in early September – end of August, and in some years even in mid-August) is observed in the altitudinal zones of Khamar-Daban and persists for the longest period – till June, and sometimes till July. A total of about 250 days with snow cover are recorded within a year. On Middle Baikal and in the south, it appears in the first ten-day period of November and in mid-October, respectively, and it disappears in late April – early May [14]. In some winters there can occur significant deviations from the mean dates. The greatest of them reach 14-31 days. Fires can occur in May, immediately after the snow cover disappears. On the western coast of Baikal (the Khuzhir and Sarma stations) the air temperature in May is 5.2-5.5 °C, with its maxima corresponding to July (14.7-15.4 °C (Table 1); the sum of temperatures higher than 10 °C (biologically active) is 1227-1300°. The southern May air temperatures vary over a wide range: 4.9-6.3 °C, and in the mountainous areas (the Khamar-Daban station) they are the lowest, as low as 2.6°C. The air temperature in July reaches 15.3 °C. The sums of temperatures higher than 10 °C are 934-1263, and in the mountainous areas they are 839 [14]. The wind regime in the Baikal region has its distinctive features. The high mountain ranges surrounding the lake prevent, to some extent, the external air currents from penetrating into the lake’s hollow thus giving rise to local circula-
158
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
Table 1 Climatic indices in the fire-hazardous months for the southwestern Baikal region, according to [14]
June
July
August
September
May
Weather stations
April
Fire-hazardous months
11.2
14.7
14.0
8.4
Monthly man air temperature, оС Khuzhir
-1.4
5.2
Sarma
-0.8
5.5
11.5
15.4
14.4
8.9
Bol. Goloustnoye
-0.6
5.4
10.4
13.5
14.0
8.3
Angara source
-1.1
4.9
9.4
12.9
12.8
7.6
Slyudyanka
-0.3
6.0
11.8
15.3
14.2
7.8
Khamar-Daban
-4.0
2.6
10.0
12.7
10.7
3.5
Amount of precipitation, mm Khuzhir
7
13
28
50
60
17
Sarma
5
10
29
53
55
18
Bol. Goloustnoye
13
21
46
64
58
26
Angara source
12
29
64
84
77
40
Slyudyanka
16
37
83
127
106
52
Khamar-Daban
85
128
211
262
212
141
Number of days with relative air humidity less than 30% Bol. Goloustnoye
4.0
3.7
1.0
0.1
0.04
0.3
Slyudyanka
1.9
1.8
0.3
0.0
0.0
0.2
Khamar-Daban
7.0
6.8
2.4
0.4
0.5
1.6
tion processes in it. Thus, sharply pronounced breezes and mountain-valley winds are observed in the vicinity the lake’s shores nearly throughout a year [15]. On the western coast of Middle Baikal the yearly mean wind velocity reaches 3 m/s, and the highest velocity of 4 m/s is observed in April-May. In a fire-hazardous season, the wind velocity is different, but the highest velocity is recorded in May (4.3 m/s); at the Bolshoye Goloustnoye the highest velocity is observed in September (4.5 m/s). In the mountains (the Khamar-Daban station), the yearly mean wind velocity is lower, or 1.6 m/s, and the highest velocity of 1.6 m/s is observed in April-June [16]. High wind velocities larger than or equal to 15 m/s are observed everywhere. Thus, the maximum mean number of days with >15 m/s wind velocities at the Bolshoye Goloustnoye station is 4.1 days in May, with this number being twice as small in July-August. A total of about 18 such days correspond to the fire-hazardous months. The values of relative air humidity in April-May are lowest and constitute 54-56% in the middle part of Baikal’s western coast (the Khuzhir and Sarma stations), and they make up 59-65% in the southern part, and in the mountains. From July to August the relative air humidity increases to 74-80% and decreases to 65-77% in September [14].
The diurnal amplitudes of the value of relative air humidity on Baikal’s coast constitute 9-18%. From April to September the range of humidity fluctuation broadens to include the possible occurrence of lower values. The largest number of dry days (with 30% or lower humidity) is observed in April, while in July-August the number of dry days decreases (from 0 to 0.1), and in September it increases to 0.3 on the western coast of the Southern Baikal region, and to 1.6 in the mountains (see Table 1). In some years the number of dry days deviates considerably from the above values. A dry period can last for more tan ten days continuously or with a short break [14], which promotes the occurrence of fires. The regime of atmospheric precipitation is determined largely by the atmospheric circulation whose behavior in a warm season is governed by enhanced cyclonic activity, and by atmospheric precipitation amounting to 65-85% pr annum. For the territory under consideration the amount of precipitation varies over a rather wide range, from 182 to 1293 mm [14]. The least amounts are observed on Olkhon Island, and the largest amounts are recorded on the slopes of the Khamar-Daban Range facing Baikal, in the southwestern part of the lake. In a fire-hazardous season, the smallest amount of precipitation corresponds to April-May. A maximum is observed in August on the territory of the middle part of the Baikal region, 55-60 mm, and in July on the western coast in the Southern Baikal region, 64 mm, with 262 mm in the mountains. The amount of precipitation decreases in September throughout the territory involved. It is difficult to investigate the meteorological factors for local (across time and space) critical pyrogenic situations on the territory of the southwestern Baikal region because of the insufficient number of weather stations; the problem is compounded by a need for special-purpose meteorological observations. According to forestry data on the occurrence of fires within the PNP (before it was granted the status of a specially protected territory) [13], with the area of lands occupied by forest resources totaling 475.6 thou ha, the forested territory was 278.3 thou ha (58.5%) in area, including 224 thou ha (or 80.4%) occupied by coniferous species (pine, larch, and Siberian stone pine). Forbs, Mongolian tea and ledum types were dominant. The area occupied by the most fire-hazardous plant communities (undergrowth of conifers and other kinds of trees) was 35.8 thou ha, or 12.9% of forested lands. The naturally occurring fie hazard was estimated having regard to the typological structure of forests using a five-point scale due to I. S. Melekhov [17] at a level of a medium class, II, 4. In doing this, a forest management compartment was used as the taxonomic fire unit (Table 2). The scale that was refined and extended by I. V. Ovsyannikov [18] is currently used in anti-fire forest management. The categories of forests are distributed in it by classes of fire hazard with due regard for the priority of fire maturing, and for the possible occurrence of strong fires. Class II of hazard is the commonest. It includes cowberry pine forests, espe-
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
159
Table 2 Distribution of lands of the PNP forest resources in classes of natural fire hazard, thou ha /% Classes of natural fire hazard
Area of lands of the forest resources,
I
II
III
IV
V
Mean class
475.6/100
3.1/17.5
186.6/39.2
125.7/26.4
79.5/16.8
0.7/0.1
II, 4
cially with the inclusion of pine undergrowth or a layer consisting of juniper with density above moderate; larch forests with undergrowth of dwarf Siberian pine trees; cembretums with the inclusion of dense undergrowth, and uneven-aged forests with vertical closure [19]. The fire hazard is assigned one class higher for coniferous forests, the structure or other characteristics of which promotes a change of a forest fire into a crown fire (dense tall undergrowth of the conifers, debris-strewn forests, etc.); for small areas of forest along waterless valleys surrounded by localities with considerable combustibility; for forested areas adjacent to public roads, and to railroads (when steam locomotive traction is used) in the immediate vicinity of wood enterprises with fire-causing potential. Ground fires in this case are possible throughout a fire-hazardous season, while crown fires can occur at periods of fire maxima. The practical significance of this categorization notwithstanding, it is pointed out that class IV of hazard includes
not only poorly combustible sphagnum and long-moss pine forests but also all grassy forests, although disastrous fires in them are not uncommon in the spring and autumn in southern Siberia. The scale includes, in addition to the s of the vegetation, the attribute of proximity to roads, which gives no way of making particular numerical estimates. The development of other typologies is underway [8]. On the other hand, these scheme permits a more detailed differentiation of the territory with regards to the pyrogenic hazard when the conditions are assessed not in terms of forestry units but according to the types of homogeneous natural condition, and this is possible by use of landscape-typological mapping. For the purpose of making such an estimate, an analysis was made of the data on fire spread in the Pribaikalsky National Park. A total of 137 forest fires was recorded in the area of 2750.1 ha for a ten-year period (1978-1987), and the area of a single fire averaged 20.1 ha (Table 3). Table 3
Distribution of the number and area (ha) of forest fires during fire-hazardous seasons of 1978-1987, according to [13}
Year
April
1978
3 48.1
1979
-
1980
-
1981 1982
1 0.6 2 3.0
May 5 15.5 8 147.8
10 1047.9
3 3.4
-
-
-
-
-
-
-
1 1.0
1 0.3
1 2.0
-
-
-
-
-
-
-
-
4
1 5.0
-
-
-
-
-
-
-
-
-
3 1.0
1984
-
-
1985
-
1986
-
%
Number of fires with unac-counted -for area
1 1.6 3 5.2
3 3.0
Total
3 1068.0
3 121.2 5 5.5
September
August
-
-
4 3.5 10 55.2 7.3 2.0
5 4.2 3 1.7
July
-
1983
1987
June
5 99.3 3 2.5 19 161.3 60 1397.4 43.8 50.8
1 0.7 2 21.5 23 1109.6 16.8 40.3
3 0.4 19 134.9 13.9 4.9
Note. Numerator – number of fires, denominator – spread area.
16 41.0 11.7 1.5
1 10.0 2 12.0 1.4 0.4
1 2 7 5.1
Total 19 192.4 16 55
Mean area of one fire 10.1 3б.4 2.4
17 2119.8 2 3.0 8 4.6 4 10.2 5 99.3 9 14.2 30 186.7 137 2750.1 100 100
124.7 1.5 0.6 2.5 19.9 1.6 6.2 20.1
160
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
According to the relative fire incidence rate of this territory (in terms of years and the number of fires per million hectare), the territory corresponds to the gradations of the “Soyuzgiproleskhoz” scale [13] below average (from 6 to 50) and above average (from 0.5 to 1.0). The duration of a fire-hazardous season between the first and last fires is 154 days. According to the number and area of fires, the maxima of a fire-hazardous season correspond to May-June (respectively, 43.8 and 16.8% in May, and 50.8 and 40.3% in June). Typically they are ground fires, so that they mostly affect forest litter and do damage to the root system of trees with the result that the affected tree stands are doomed to die, and the problem is compounded by the fact that very thin layers of mountain soils are dominant. Forest fires are in most cases deliberately set (the proportion of “unnatural”, or man-made, fires constitute 80%), and the share of naturally occurring (cased by lightning) is 9%. Nearly every seventeenth fire (5.8%) occurs due to unknown reasons. Most of the territory is being monitored by the aircraftassisted forest fire control service. Aircraft detect 30.5% of fires, and 80% of them can be identified in an area as small as 0.5 ha (and 51% of these in an area as small as 0.1 ha), which indicates a reasonably high efficiency of this monitoring operations. Only 39.4% of fires and about one-sixth of fires with an area of about 0.5 ha, and several tens of hectares, respectively, are successfully eliminated. More than 77.9% of fires took more than 24 hours to be eliminated. For comparison, only 21 forest fires, with 16.1 ha the mean area of a single fire, were recorded on the territory of the Slyudyanka forestry district adjacent to the national park in the Southern Baikal region. The territory of the forestry district compares with the PNP – 352 thou ha; it should be noted, however, that the physical-geographical conditions, including the climatic conditions, the landscape structure, the structure of the states of geosystems [3, 12], and also the transport and residential infrastructure are different. Given the validity of the analysis of averaged estimates made for forestry districts in the case of small-scale pyrological zoning [4], it is of interest to examine the situational dynamics of fires, and the conditions o their localization. The individualities of forest fires are relatively many-sided; in this connection, an analysis was made of the database on forest fires in the Pribaikalsky National Park which we generated in electronic tables to take into account the forest fires on the park’s territory from 1995 to 2005. The database includes the place of fire occurrence (within a compartment), the date, the area, and the possible causes. Adjustment of fires to the topographic and forest-husbandry base makes it possible to analyze, in a more thorough manner and by taking into consideration the ambient properties of the territory, the favorable conditions for the occurrence and spread of fires. For analyzing the local conditions, the hotspots and the burned-over areas were superimposed on the raster layers of the topographic base, forest inventory data, and with thematic materials obtained by the Institute of Geography
SB RAS, and with space-acquired remotely sensed data for this territory from different years; the highest informational content corresponded to the Landsat ETM 2000 and 2002 images [2] which we synthesized and which were represented in seven spectral regions with a resolution of 15 m when synthesized with the eighth channel. The hotspots, which in the database correspond to a forest-husbandry compartment, were actually localized on the terrain, which is supported by field observations, and by the available remotely sensed data, with the burned-over areas are clearly interpretable – this is especially true for fresh data. For the period from 1995 to 2005, 256 fires were recorded on the territory of the PNP. Their total area was larger than 23 thou ha, and the area of a single fire averaged 90.0 ha. The number of small fires (with burned-over areas less than 0.5 ha) constituted 31% (68 events), while 69%, or 177 events, correspond to burned-out forests with an area larger than 0.5 ha; 112 events correspond to an area larger than 5 ha, and 29 events encompassed more than 200 ha. Burned-over areas measuring several thousand hectares were recorded in some years: 1117 ha in May 1996, 1400 and 1650 ha in late May and in August 1997, respectively, 1500 in May 1998, and 2 thou ha in May 2000. In subsequent years the individual territories affected by fires did not exceed 1 thou ha. The least number of fires was observed in 2001 – the area of burned-out forest was only 24.5 ha (seven events at the beginning of a fire-hazardous season). The largest territory that was affected by fires was recorded in 1997 – its area was 5709.5 ha (35 events throughout the fire-hazardous season). More than 5 thou ha underwent forest fires in 1998 and 2003. Noteworthy is the gross difference in the averaged statistical data on the number of forest fires on the same territory, with relatively identical natural conditions but at different periods: 1978-1987 and 19952005. This can be explained not only by the differences in the dynamics of climatic conditions but also by such factors and a change of the economic entity, and hence by the different attitude to the recording of forest fires as well as by the increased utilization of the territory as the touristic resource. The distribution of forest fires across the territory (see the figure) is uneven and does not show any obvious match of its differentiation by humidification in a warm season [12]. The most likely cause is the anthropogenic factor. As regards the concentration of the origins of fires, their largest number is observed near the residential zone of the settlement of Listvyanka as well as in the coastal zone adjacent to the settlements, the holiday camps as well as to the transport routes (the railroad, and motor roads of different purposes). The smallest number of fire events was recorded in 2001. The fires that were recorded only in May – early June, were creeping ground fires and seem to be associated with the anthropogenic factor, because they occurred in the neighborhoods of communities. The largest areas (in excess of 5 thou ha) were affected by fires in 1997, 1998, and 2003. The fire
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
161
The distribution of hotspots on the territory of the Pribaiklsky National Park during 1995-2005. A portion of the schematic map. 1 – stable-derivative and short-term-derivative states of geosystems with small-leaved forest; 2 – residential territories; 3 – roads of different purposes; 4 – PNP boundary. Functional zones of PNP: 5 – reserve zone, 6 – recreational utilization, 7 – services to visitors, 8 – other lands. Hotspots: 9 – large fires, 10 – small fires.
events and the fresh burned-over areas show a much more uniform distribution across the national park’s territory during the aforementioned years. The spread of large forest fires coincides with predominance of stable-derivative states of geosystems in the territorial structure. Such areas are characterized by small-leaved plant communities, as is the case with the Olkhinskoye upland. The areas of large fires in this case have their origins in the territories adjacent to the national park. The fact that there were no fires for a 10-year period in secondary structures of geosystems and that only small fires occurred is beneficial for a successful regeneration of coniferous forests, which is confirmed by the field descriptions of the states of geosystems, pointing out the regeneration of Siberian stone pine and spruce under the canopy of smallleaved trees. The strongest fires occurred in May-June. They are rather common in the presence of numerous smaller fires. The largest (strong creeping ground) fire embracing an area of 2000 ha was recorded in the last ten-day period of May 2000 along the right bank of the Cheremshanka river in the PrimorskoOnotsky mountain-taiga and sub-taiga district – it affected near-watershed and (southern exposure) slope geosystems represented by pine and small-leaved grassy forests. A natural obstacle to it in the southern part was the valley of the
Cheremshanka river; only the southern exposure slope was actually burned out. Another large fire that occurred in this same area in midMay 1998 encompassed 1150 ha. The burned-over area lies in the upper part of the Nikulikha creek valley. The fire occurred in the stable-derivative territorial structure of mountain-taiga geosystems with small-leaved grass plant communities. The fire that was recorded in May 1998 in an area of 1100 ha along the Raspopikha creek valley was localized along the path running from the Angara reservoir. An extensive burned-over locality in the Olkhinsky piedmont-elevated mountain-taiga area of the Kitoi-Angara district is clearly seen on the synthesized image from the year 2002. This area includes at least four fires that occurred in different years over the course of ten years. Specifically, a large burned-over area of 1100 ha was recorded here in May 1998. Territorially, the burned-over areas are associated with fires arriving at the boundaries of the national park from the north. The spread of fires in different years, and the secondary structure of the states of geosystems with pine and small-leaved forests indicates that fires occurred on multiple occasions. This area is bounded by valley complexes; yet, it encompasses the upper parts of the interfluves of several rivers.
162
E. G. Suvorov et al. / Geography and Natural Resources 29 (2008) 156–162
In 2003, 62 fires were recorded (with the burned-over areas exceeding 5 thou ha), including nine large fires (over 200 ha each). All occurred in places visited by people on the slopes of the Yelovka, Kirpichnaya and Bolshiye Koty creek valleys, in the neighborhoods of the village of Talovka, and at 300-800 m from roads and ride swaths in middle-aged pine and small-leaved forests. The fire spread was proceeding according to the type of stable ground fire and crown fire of moderate intensity. Conclusion The distribution of fires confirms rather clearly the stable character of the structure of the states of geosystems with derivative vegetation, both immediately in the coastal zone of Lake Baikal and in the other part of the PNP. The factor of transport accessibility is also of important significance. Most of the fires correspond to May-June. Small fires are dominant in humid years, and the years of increased dryness determine a more uniform distribution of large fires. Analysis of the distribution of hotspots demonstrates that they are concentrated in secondary structures of the states of geosystems, which determines maintenance of such states over a long period of time. Thus the territory of the Pribaikalsky National Park is facing a strained fire-hazardous situation, and it can aggravate further because of the promotion of recreation. It is therefore necessary to improve anti-fire measures. The existing sitespecific diversity of conditions leading to forest fires calls for territorial differentiation of protection measures. This work was done with financial support from the Russian Foundation for Basic Research (04-05-65182, and 0505-97252). References 1. Mikheyev V. S. and Ryashchin V. A. Physical-geographical regionalization: Insert map of a scale of 1:8 000 000. In: The Landscapes in the South of East Siberia: the 1:1 500 000 Map. Moscow: GUGK, 1977. 2. Mikheyev V. S. Landscape structure. In: Nature Management and Environmental Protection in Baikal Watershed Basin. Novosibirsk: Nauka, 19990, pp. 7-29.
3. Suvorov E. G. General physical-geographical conditions of a territory. In: Ecologically Oriented Land Use Planning in the Baikal Region. The Slyudyanka District. Irkutsk: Institute of Geography SB RAS Publisher, 2002, pp. 53-58. 4. Sofronov M. A., Antropov V. F. and Volokitina A. V. The pyrological description of the vegetation within the Lake Baikal watershed basin. Geografiya i prirod. resursy, 1999, No. 2, pp. 52-58. 5. Valendik E. N. The synoptic situations that are responsible for large forest fires. In: Forest Fires and Their Consequences. Krasnoyarsk, 1985, pp. 5-12. 6. Valendik E. N. Large forest fires in Siberia. Geografiya i prirod. resursy, 1995, No. 1, pp. 85-92. 7. Kurbatsky N. P. The problem of forest fires. In: The Origination of Forest Fires. Moscow: Nauka, 1964, pp. 5-52. 8. Volokitina A. V. and Sofronov M. A. Classification and Mapping of Combustible Plant Materials. Novosibirsk: Izd-vo SO RAN, 2002, 306 p. 9. Bufal V. V. The radiation regime of the Lake Baikal hollow and its role in climate formation. In: The Climate of Lake Baikal and of the Baikal Region. Moscow, 1966, pp. 34-70. 10. The Structure and Resources of the Climate of Baikal and Neighboring Spaces. Novosibirsk: Nauka, 1977, 271 p. 11. Ladeishchikov N. P. Climate Characteristics of Large Lakes (Using Baikal as an Example). Moscow: Nauka, 1982, 135 p. 12. Trofimova I. E. Typization and mapping of the climates of the Baikal mountain-depression system. Geografiya i prirod. resursy, 2002, No. 2, pp. 53-61. 13. Anti-fire forest management: the framework master plan for the establishment of the Pribaikalsky state national park. 4695-3S. Forestry. Moscow, 1989, Book 2, vol. 4, 142 p. 14. Handbook on the USSR Climate. Leningrad: Gidrometeoizdat, 1966, 1968, issue 22, pt. 2, 359 p.; pt. 4 , 278 p. 15. Characteristics of the Hydrometeorological Regime of Lake Baikal and Its Influence on Fleet Operations. Irkutsk, 1967, 98 p. 16. Applied-Science Handbook on the USSR Climate. Long-term Data. Ser. 3. Leningrad: Gidrometeoizdat, 1991, pt. 1-6, issue 22, 604 p. 17. Melekhov I. S. Nature of Forests and Forest Fires. Arkhangelsk: OGIZ, 1947, 60 p. 18. Ovsyanikov I. V. Anti-fire Forest Management. Moscow: Lesnaya promyshlennost, 1978, 112 p. 19. Collection of Departmental Acts on Forestry for USSR Gosleskhoz for 1966-1976. Moscow: Gosleskhoz, 1979, 206 p. 20. http//www.landsat.org.