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The effects of selection cutting on regeneration of Picea jezoensis and Abies sachalinensis in the sub-boreal forests of Hokkaido, northern Japan
Forest Ecology and Management 146 (2001) 15±23
The effects of selection cutting on regeneration of Picea jezoensis and Abies sachalinensis in the sub-boreal forests of Hokkaido, northern Japan Masahiko Nakagawaa,*, Akio Kurahashib, Mikio Kajib, Taizo Hogetsuc a
Okoppe Hokkaido Forest Management Center, 727-6 Aza-Okoppe, Okoppe-cho, Mombetsu-gun, Hokkaido, 098-1607, Japan b The Hokkaido Tokyo University Forest, Yamabe, Furano-city, Hokkaido, 079-1561, Japan c The Asian Natural Environmental Science Center, the University of Tokyo 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Received 22 June 1999; received in revised form 4 February 2000; accepted 13 March 2000
Abstract This study investigated the effects of selection cutting on seedling densities of Picea jezoensis and Abies sachalinensis in the sub-boreal forests of the Hokkaido Tokyo University Forest. Volumes of, and coverage with, fallen logs, broken stems and snags in a preserve stand were signi®cantly greater than those in a selection cutting stand. Regeneration substrates of P. jezoensis were limited to coarse woody debris and root mounds, whereas A. sachalinensis was found on coarse woody debris, root mounds, and soil. P. jezoensis seedling density on any regeneration substrate was not increased by selection cutting, whereas A. sachalinensis seedling densities on cut stumps and soil increased. An overall P. jezoensis seedling density in the preserve stand was signi®cantly greater than that in the selection cutting stand, but there was no statistically signi®cant difference in the densities of A. sachalinensis seedlings between the preserve and the selection cutting stands. The present study demonstrates that selection cutting in the sub-boreal forest of the Hokkaido Tokyo University Forest results in reduction of P. jezoensis seedling density because of reduction in coarse woody debris, the crucial regeneration substrate for P. jezoensis, and enhancement of A. sachalinensis regeneration on cut stumps and soil. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Picea jezoensis; Abies sachalinensis; Natural regeneration; Coarse woody debris; Selection cutting; Sub-boreal forest
1. Introduction The sub-boreal forests of Hokkaido, the northernmost island of Japan, are dominated by Yezo spruce (Picea jezoensis Carr.) and Sachalin ®r (Abies sachalinensis Masters), both of which are economically important species. In most of the sub-boreal forests, forest ¯oors are covered with several species of bamboo grass (Sasa Makino et Shibata). There are certain * Corresponding author. Tel.: 81-1588-2-4084. E-mail address: [email protected] (M. Nakagawa).
amounts of coarse woody debris in the primeval forest, which are the main regeneration sites for the two coniferous species in that region (Haruki et al., 1990; Kubota et al., 1994; Hiura et al., 1996). Large-scale clear cutting and arti®cial plantation establishment have been a common management style in the sub-boreal forests of Hokkaido. However, due to the outbreak of diseases and weather damages many arti®cial plantations were unsuccessful. Therefore, natural forest management based on selection cutting and natural regeneration which has been carried out in the Hokkaido Tokyo University Forest, named the
0378-1127/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 1 1 2 7 ( 0 0 ) 0 0 4 4 5 - X
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M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
Silvicultural Management System (SMS), was proposed as a sustainable management model for the subboreal forests of Hokkaido (Takahashi, 1971, 1993; Shibata, 1988; Watanabe and Sasaki, 1994). The SMS has several unique points. A permanent high density road network is maintained to maximize ef®ciency of harvesting operations by heavy machinery and minimize harvesting damages to standing trees. In sub-boreal forests, harvesting volumes are limited to 18±25% of the stocking volume, which is kept at 65±80% of that of the primeval forest to maintain high-volume growth and the forest environment which is similar to the primeval forests. Diseased, senescent, non-vigorous, un-wanted and deformed trees are removed by single-tree selection cutting to control a stand composition toward a desired one. The forests under the SMS also ful®l non-timber needs, such as wildlife habitats, protection of headwaters, recreation, and forestry education. Although the SMS is one of the ideal forest management style, there might be some points which still need improvements. Natural mortality of trees is minimized under the SMS by preferentially harvesting trees which would otherwise die (Yamamoto, 1994). Since minimized mortality reduces supplies of coarse woody debris, the forest ¯oor under the SMS would be covered with a less amount of coarse woody debris. Nagaike et al. (1999) pointed out a possibility that reduction of coarse woody debris by selection cutting results in reduced conifer seedling regeneration. Thus, it is necessary to review the SMS from the viewpoint of regeneration, because maintaining number of trees is essential for sustainable forest management. In the present study, we investigated the effects of selection cutting on natural regeneration by comparing seedling densities of coniferous species between a preserve and a selection cutting stands under the SMS in the Hokkaido Tokyo University Forest. 2. Study area The study was conducted in the Hokkaido Tokyo University Forest located between 438100 ±438200 N and 1428180 ±1428400 E, the elevation range being from 190 to 1459 m (asl). The sub-boreal forests dominated
by Yezo spruce and Sachalin ®r are found at the elevations of between 600 and 1100 m. A few hardwoods mixed in with two conifer species are: Japanese rowan (Sorbus commixta Hedl.), Erman's birch (Betula ermanii Cham.), ohyo elm (Ulmus laciniata (Trautv.) Mayr), Japan-linden (Tilia japonica (Miq.) Simonkai), shiuri cherry blossom (Prunus ssiori Fr. Schm.), etc. Forest ¯oors are mostly covered with kumaizasa bamboo grass (Sasa senanensis (Franchet et Savatier) Rehder). (Kato, 1952; Shibata, 1988). Meteorological information obtained by the Hokkaido Tokyo University Forest at the closest observatory point (at 730 m of elevation) to the study area are: mean annual temperature, 4.48C; minimum monthly temperature, 9.58C; and maximum monthly temperature, 19.48C. Annual precipitation measured near the University Forest was about 1200± 1500 mm. Maximum snow depth is about 2 m, and the ground is continuously covered with snow from November to April. (The University Forest in Hokkaido, 1977). The soil around 700 m elevation, the closest elevation at which the soil type has been reported, is classi®ed as brown forest soils (Japanese soil taxonomy). Decomposition of litter and humus is slow because of the cold temperature over half of the year. The A-horizon is generally thick, dark brown and granular in its structure. The B-horizon is generally brown-to-red brown, very hard and compact in its structure. Some leaching of iron is taking place in the upper horizon, but not to the degree where typical gray and red/yellow podsol horizons can be observed. The parent material is andesite. A lot of volcanic sand is mixed into the A-horizon. The topography is very gentle. (Asahi, 1963; Nakata et al., 1994). The Maeyama Forest Preserve of 1200 ha was established in 1972 in the sub-compartment No. 7a and b. Prior to 1937, selection cutting of 10% by volume had taken place for once. However, the harvest volume was relatively low in the Forest Preserve compared to the rest of the selection cutting stands in the Hokkaido Tokyo University Forest. After 1937, the Forest Preserve has received virtually no human impact except occasional measurements. There is no harvesting, planting, ground disturbance, or removal of fallen logs and snags in the Forest Preserve. Since there is no primeval sub-boreal forests left in the University Forest, no other forest in the Hokkaido
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
Tokyo University Forest is closer to the primeval sub-boreal forest than the Forest Preserve (Shibano et al., 1996). In the sub-compartment No. 7c selective cuttings were carried out several times from 1903 to 1957. After 1957, the SMS has been implemented. It was classi®ed into the category of the `selection cutting stand' where abundant seedlings are supposed to be present under overstory canopies. Selection cutting of 18±25% by volume is to be implemented with the cutting cycle of about 20 years. Diseased, senescent, un-vigorous, un-wanted, and deformed trees are removed and stand volume is kept at about 70± 80% of that of the primeval forests. In addition to the regular harvesting, trees which are dead or damaged by insects are removed to prevent the spread of diseases and insect damages. This area is close to the Forest Preserve, and environmental conditions such as meteorology, soil, vegetation type, topography are very similar to those of the Forest Preserve. 3. Methods Fourteen preserve plots with the size of 20 m20 m were established along the 680 m contour line within the sub-compartment Nos. 7a and b (the preserve stand). Fourteen selection cutting plots of 20 m20 m were established along the 660 m contour line within sub-compartment No. 7c (the selection cutting stand). Coarse woody debris were classi®ed into fallen logs, broken stems, cut stumps, and snags. Broken stems are tree trunks with <1 m height which originated from breaking of trunks, and snags are standing dead trees with >1m height. In each plot, fallen logs, broken stems, cut stumps, and snags except portions which were less than 10 cm in diameter were recorded as coarse woody debris. Diameter of both ends and length for each coarse woody debris piece were recorded. Regeneration substrates were classi®ed into six categories: fallen logs, broken stems, cut stumps, snags, root mounds, and soil. Root mounds are above ground portion of root stocks of live trees. Yezo spruce and Sachalin ®r seedlings, whose heights were 3± 130 cm, were counted and their regeneration sub-
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strates recorded. Student t-test (a0.05) was used for statistical analysis. 4. Results There were 263 and 90 m3 of total coarse woody debris in the preserve stand and the selection cutting stand, respectively (Fig. 1). A percentage of forest ¯oor covered with coarse woody debris was 7.0% in the preserve stand and 2.4% in the selection cutting stand (Fig. 2). Both of the differences were statistically signi®cant. Volumes of fallen logs, broken stems, and snags and areas occupied by them in the preserve stand were signi®cantly greater than those in the selection cutting stand. On the other hand, a volume of cut stumps and an area occupied by them in the selection cutting stand were signi®cantly greater than those in the preserve stand. Seedling densities of Yezo spruce per square meter of all regeneration substrates were not signi®cantly different between the preserve and the selection cutting stands (Fig. 3). On the other hand, those of Sachalin ®r per square meter of cut stumps and soil in the selection cutting stand were signi®cantly greater than those in the preserve stand (Fig. 4). Almost all Yezo spruce seedlings were found on coarse woody debris and none was found on soil (Fig. 5). Most Sachalin ®r seedlings were found on coarse woody debris in the preserve stand, but many of them were found also on soil in the selection cutting stand (Fig. 6). Seedling densities per hectare of forest ¯oor for both Yezo spruce and Sachalin ®r on fallen logs, and broken stems in the preserve stand were signi®cantly greater than those in the selection cutting stand. On the other hand, seedling densities per hectare of forest ¯oor for both species on cut stumps in the selection cutting stand were signi®cantly greater than those in the preserve stand. There were no Yezo spruce seedlings on soil in both stands, whereas a seedling density of Sachalin ®r on soil in the selection cutting stand was signi®cantly greater than that in the preserve stand. A total Yezo spruce seedling density per hectare of forest ¯oor in the preserve stand was signi®cantly greater than that in the selection cutting stand. On the other hand, the differences in total seedling densities of Sachalin ®r per hectare of forest ¯oor between the preserve and the selection cutting stands were not statistically signi®cant.
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Fig. 1. Average volumes of coarse woody debris in the preserve and the selection cutting stands.
Fig. 2. Average percentage of forest floor covered with coarse woody debris in the preserve and the selection cutting stands.
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
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Fig. 3. Average seedling density of Picea jezoensis per square meter of regeneration substrates in the preserve and the selection cutting stands.
Fig. 4. Average seedling density of Abies sachalinensis per square meter of regeneration substrates in the preserve and the selection cutting stands.
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M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
Fig. 5. Average seedling density and regeneration substrate of Picea jezoensis per hectare of forest floor in the preserve and the selection cutting stands.
Fig. 6. Average seedling density and regeneration substrate of Abies sachalinensis per hectare of forest floor in the preserve and the selection cutting stands.
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
5. Discussion The present study suggests that selection cutting in the sub-boreal forests of the Hokkaido Tokyo University Forest indeed leads to a signi®cant reduction of Yezo spruce seedlings, and no signi®cant change in Sachalin ®r seedlings. This is inconsistent with what Nagaike et al. (1999) reported, namely repeated selective harvesting will lead to a decrease in seedling regeneration of both species, because the main regeneration substrates for the two coniferous species in selectively harvested stands are fallen logs and cut stumps. Although the reason for the different effects of selection cutting on seedling densities between Yezo spruce and Sachalin ®r is not clear from the result of this study, it may be due to the different characteristics of regeneration between the two coniferous species. Yezo spruce seedlings regenerated only on coarse woody debris whereas many Sachalin ®r seedlings were found on soil (Figs. 5 and 6), being consistent with some previous ®ndings that Yezo spruce seedlings rarely regenerate on A horizon soil, whereas Sachalin ®r seedlings do (Takahashi et al., 1981, 1984; Iguchi et al., 1992). The difference in regeneration substrates might be explained by the difference in susceptibilities of the two conifers to Racodium snow blight (Racodium therryanum Thuem.). It is a serious disease which attacks seeds and seedlings of Yezo spruce and Sachalin ®r under snow during winter (Sato et al., 1960). The disease fungus is distributed where organic matters are abundant, but rarely was it found on fallen logs (Cheng and Igarashi, 1987; Cheng, 1989; Takahashi, 1991). Since seeds and seedlings of Sachalin ®r are more resistant to Racodium snow blight than those of Yezo spruce (Takahashi, 1979; Cheng and Igarashi, 1990; Takahashi and Ogasawara, 1990), the fungus might prevent regeneration of Yezo spruce on soil. A ground disturbance by harvesting could enhance regeneration of Sachalin ®r on soil. Litters are removed and soil is disturbed by harvesting with heavy machinery in some parts of the selection cutting stand, whereas there are virtually no human impacts in the preserve stand. Removal of litters, damaging bamboo grass, and raking of A horizons by heavy machinery are effective for regeneration of some woody species (Matsuda and Takikawa, 1985).
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The signi®cant increase of Sachalin ®r seedling density on soil in the selection cutting stand (Figs. 4 and 6) could be due to the soil disturbance by harvesting activities. Different reactions of the two coniferous species to improved light conditions after selection cutting could not be ignored, either. Fujimura et al. (1992) reported that arti®cial shading does not affect height growth of Yezo spruce, but that of Sachalin ®r seedlings is reduced. Fukuchi et al. (1979) reported that small seedlings of Sachalin ®r do not grow and gradually disappear in a dense plantation forest and an improved light condition by thinning is effective for natural regeneration of the species. The signi®cant increases of seedling densities of Sachalin ®r per square meter of soil and cut stumps (Fig. 4) may be due to the improved light conditions by selection cutting which reduces mortality of Sachalin ®r seedlings. Further research is needed to clarify to what extent each of the above three reasons contributes to the difference in effects of selection cutting on seedling densities between Yezo spruce and Sachalin ®r. Although present species composition of the seedlings does not precisely re¯ect the species composition in the future, results of the present study suggest a possibility that Sachalin ®r becomes more dominant and Yezo spruce less dominant under the SMS in the sub-boreal forests of the Hokkaido Tokyo University Forest. Especially, if no fallen log is supplied in the future, Yezo spruce seedling bank will diminish further as coarse woody debris which presently exists continues to decay. Thus, it might be dif®cult to maintain Yezo spruce resources under the SMS. Kubota (1996) pointed out that regeneration strategies are often ignored in natural forest management plans although ensuring regeneration is essential for sustainable forest management. The SMS might fail to meet a requirement for sustainable forest management, a regeneration strategy of Yezo spruce. To ensure natural regeneration of Yezo spruce caution must be taken so that heavy machinery used in harvesting does not damage coarse woody debris. In addition, forest management policy needs to be changed so that certain amounts of coarse woody debris, a crucial regeneration substrate for Yezo spruce, is supplied under the SMS.
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Acknowledgements The authors thank the staff of the Hokkaido Tokyo University Forest, especially Mr. Yasuo Takahashi and Mr. Shinsaku Shibano, for providing the management information of the forest. References Asahi, M., 1963. Studies on the classification of forest soils in the Tokyo University Forest, Hokkaido (in Japanese, with English Abstract. Bull. Tokyo Univ. For. 58, 1±132. Cheng, D., 1989. Studies on Racodium therryanum-caused in-soil seed rot with special reference to its impact on natural regeneration of Yezo spruce (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 46, 529±575. Cheng, D., Igarashi, T., 1987. Fungi associated with natural regeneration of Picea jezoensis Carr. in seed stage Ð their distribution on forest floors and pathogenicity to the seeds. Res. Bull. Exp. For. Hokkaido Univ. 44, 175±188. Cheng, D., Igarashi, T., 1990. Comparison of susceptibility to Racodium therryanum infection of seeds and seedlings of four coniferous species (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 47, 125±136. Fujimura, Y., Koike, T., Tabuchi, R., Takahashi, K., 1992. Effects of the artificial shading on the growth of Picea jezoensis (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 40, 98±100. Fukuchi, M., Kikuzawa, K., Asai, T., Mizutani, E., 1979. Todomatsu no rinnai koushin ni kansuru kenkyu Ð jittai chousa no kekka kara (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 28, 115±117. Haruki, M., Itagaki, T., Namikawa, K., Ishikawa, Y., 1990. Forest construction in the Tokachi River Watershed Wilderness Area, in the Daisetsuzan National Park, northern Japan (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 47, 83±123. Hiura, T., Sano, J., Konno, Y., 1996. Age structure and response to fine-scale disturbance of Abies sachalinensis, Picea jezoensis, Picea glehnii, and Betula ermanii growing under the influence of a dwarf bamboo understorey in northern Japan. Can. J. For. Res. 26, 289±297. Iguchi, K., Ogasawara, S., Kasahara, H., Satou, S., Watanabe, S., 1992. Disappearance and growth of seedlings on different seed beds of seven provenance of Picea jezoensis (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 40, 59±61. Kato, R., 1952. The vegetation of the Tokyo University Forest in Hokkaido (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 43, 1±18. Kubota, Y., 1996. Logging strategy of primary forest based on the regeneration process (in Japanese with English Abstract). J. Jpn. For. Soc. 78, 79±83. Kubota, Y., Konno, Y., Hiura, T., 1994. Stand structure and growth patterns of understorey trees in a coniferous forest,
Taisetsuzan National Park, northern Japan. Ecol. Res. 9, 333±341. Matsuda, K., Takikawa, S., 1985. Practical study on promotional treatment of natural regeneration (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 42, 909±940. Nakata, M., Tanaka, H., Yagi, H., 1994. Altitudinal changes in vegetation and soils on Mt. Dairoku, central Hokkaido, Japan (in Japanese, with English Abstract). Jpn. J. Ecol. 44, 33±47. Nagaike, T., Kubota, Y., Watanabe, N., 1999. The effects of selective logging on stand structure and the regeneration of subboreal forests in Hokkaido, northern Japan. J. For. Res. 4, 41±45. Sato, K., Shoji, T., Ota, N., 1960. Studies on the snow molding of coniferous seedlings. II Dark snow blight caused by Racodium therryanum Thuem (in Japanese, with English Abstract). Bull. Govt. For. Exp. Sta. 124, 21±100. Shibano, S., Okamura, K., Takahashi, Y., Watanabe, S., 1996. Techniques for establishing a large permanent research plot for studies of forest dynamics in a mixed forest zone (in Japanese, with English Abstract). Jpn. J. Ecol. 46, 155±168. Shibata, S., 1988. Studies on the management of natural forests Ð an experiment of natural forest management in the Tokyo University Forest in Hokkaido (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 80, 269±397. Takahashi, I., 1979. Studies on mycoflora and diseases of coniferous trees at the central part of Hokkaido, Japan Ð special reference to Ascomycetes, Fungi imperfecti and Uradinales (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 69, 1±143. Takahashi, I., 1991. Studies on the mycofloral succession on Yezo spruce (Picea jezoensis Carr.) in various stages of growth, with special reference to the role of fungi in the natural regeneration of the host (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 86, 201±273. Takahashi, I., Ogasawara, S., 1990. Preventive effect of dark snow blight on young seedlings of Todo fir and Yezo spruce by soil treatment with sterilization (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 38, 113±115. Takahashi, I., Miyamori, Y., Shibano, H., Hatano, K., 1981. Ezomatsu Todomatu no tennenkoushin ni kansuru kenkyu Ð kakushu hashudoko niokeru chibyou no hassei shoushitsu (2kanen no keika) (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 30, 79±81. Takahashi, I., Miyamori, Y., Hatano, K., 1984. Ezomatsu Todomatu no tennenkoushin ni kansuru kenkyu Ð rinchi niokeru kakushu hashudoko no seiiku joukyou. (3±5nen keika) (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 33, 62±64. Takahashi, N., 1971. Rinbun segyo ho Ð sono kangaekata to jissai. Zenkoku Ringyo Kairyo Fukyu Kyokai. Tokyo, 127 pp., (in Japanese). Takahashi, N., 1993. Rinbun segyo ho no riron to jissen (in Japanese). Gakujutsugeppo 46, 6±11. The University Forest in Hokkaido, 1977. Meteorological observations at different elevations of Mt. Dairoku, the Tokyo
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23 University Forest in Hokkaido. Records in the period 1972± 1975 and short discussion on them (in Japanese, with English Abstract.). The miscellaneous information (in Japanese, with English Abstract), Tokyo University Forests 21, pp. 22±47. Watanabe, S., Sasaki, S., 1994. The silvicultural management system in temperate and boreal forests: a case history of the
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Hokkaido Tokyo University Forest. Can. J. For. Res. 24, 1176±1185. Yamamoto, H., 1994. Natural forest management based on selection cutting and natural regeneration. Proceedings of IUFRO international workshop on sustainable forest managements. ISBN 4-9900381-O-X, pp. 10±22.
The effects of selection cutting on regeneration of Picea jezoensis and Abies sachalinensis in the sub-boreal forests of Hokkaido, northern Japan Masahiko Nakagawaa,*, Akio Kurahashib, Mikio Kajib, Taizo Hogetsuc a
Okoppe Hokkaido Forest Management Center, 727-6 Aza-Okoppe, Okoppe-cho, Mombetsu-gun, Hokkaido, 098-1607, Japan b The Hokkaido Tokyo University Forest, Yamabe, Furano-city, Hokkaido, 079-1561, Japan c The Asian Natural Environmental Science Center, the University of Tokyo 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Received 22 June 1999; received in revised form 4 February 2000; accepted 13 March 2000
Abstract This study investigated the effects of selection cutting on seedling densities of Picea jezoensis and Abies sachalinensis in the sub-boreal forests of the Hokkaido Tokyo University Forest. Volumes of, and coverage with, fallen logs, broken stems and snags in a preserve stand were signi®cantly greater than those in a selection cutting stand. Regeneration substrates of P. jezoensis were limited to coarse woody debris and root mounds, whereas A. sachalinensis was found on coarse woody debris, root mounds, and soil. P. jezoensis seedling density on any regeneration substrate was not increased by selection cutting, whereas A. sachalinensis seedling densities on cut stumps and soil increased. An overall P. jezoensis seedling density in the preserve stand was signi®cantly greater than that in the selection cutting stand, but there was no statistically signi®cant difference in the densities of A. sachalinensis seedlings between the preserve and the selection cutting stands. The present study demonstrates that selection cutting in the sub-boreal forest of the Hokkaido Tokyo University Forest results in reduction of P. jezoensis seedling density because of reduction in coarse woody debris, the crucial regeneration substrate for P. jezoensis, and enhancement of A. sachalinensis regeneration on cut stumps and soil. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Picea jezoensis; Abies sachalinensis; Natural regeneration; Coarse woody debris; Selection cutting; Sub-boreal forest
1. Introduction The sub-boreal forests of Hokkaido, the northernmost island of Japan, are dominated by Yezo spruce (Picea jezoensis Carr.) and Sachalin ®r (Abies sachalinensis Masters), both of which are economically important species. In most of the sub-boreal forests, forest ¯oors are covered with several species of bamboo grass (Sasa Makino et Shibata). There are certain * Corresponding author. Tel.: 81-1588-2-4084. E-mail address: [email protected] (M. Nakagawa).
amounts of coarse woody debris in the primeval forest, which are the main regeneration sites for the two coniferous species in that region (Haruki et al., 1990; Kubota et al., 1994; Hiura et al., 1996). Large-scale clear cutting and arti®cial plantation establishment have been a common management style in the sub-boreal forests of Hokkaido. However, due to the outbreak of diseases and weather damages many arti®cial plantations were unsuccessful. Therefore, natural forest management based on selection cutting and natural regeneration which has been carried out in the Hokkaido Tokyo University Forest, named the
0378-1127/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 1 1 2 7 ( 0 0 ) 0 0 4 4 5 - X
16
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
Silvicultural Management System (SMS), was proposed as a sustainable management model for the subboreal forests of Hokkaido (Takahashi, 1971, 1993; Shibata, 1988; Watanabe and Sasaki, 1994). The SMS has several unique points. A permanent high density road network is maintained to maximize ef®ciency of harvesting operations by heavy machinery and minimize harvesting damages to standing trees. In sub-boreal forests, harvesting volumes are limited to 18±25% of the stocking volume, which is kept at 65±80% of that of the primeval forest to maintain high-volume growth and the forest environment which is similar to the primeval forests. Diseased, senescent, non-vigorous, un-wanted and deformed trees are removed by single-tree selection cutting to control a stand composition toward a desired one. The forests under the SMS also ful®l non-timber needs, such as wildlife habitats, protection of headwaters, recreation, and forestry education. Although the SMS is one of the ideal forest management style, there might be some points which still need improvements. Natural mortality of trees is minimized under the SMS by preferentially harvesting trees which would otherwise die (Yamamoto, 1994). Since minimized mortality reduces supplies of coarse woody debris, the forest ¯oor under the SMS would be covered with a less amount of coarse woody debris. Nagaike et al. (1999) pointed out a possibility that reduction of coarse woody debris by selection cutting results in reduced conifer seedling regeneration. Thus, it is necessary to review the SMS from the viewpoint of regeneration, because maintaining number of trees is essential for sustainable forest management. In the present study, we investigated the effects of selection cutting on natural regeneration by comparing seedling densities of coniferous species between a preserve and a selection cutting stands under the SMS in the Hokkaido Tokyo University Forest. 2. Study area The study was conducted in the Hokkaido Tokyo University Forest located between 438100 ±438200 N and 1428180 ±1428400 E, the elevation range being from 190 to 1459 m (asl). The sub-boreal forests dominated
by Yezo spruce and Sachalin ®r are found at the elevations of between 600 and 1100 m. A few hardwoods mixed in with two conifer species are: Japanese rowan (Sorbus commixta Hedl.), Erman's birch (Betula ermanii Cham.), ohyo elm (Ulmus laciniata (Trautv.) Mayr), Japan-linden (Tilia japonica (Miq.) Simonkai), shiuri cherry blossom (Prunus ssiori Fr. Schm.), etc. Forest ¯oors are mostly covered with kumaizasa bamboo grass (Sasa senanensis (Franchet et Savatier) Rehder). (Kato, 1952; Shibata, 1988). Meteorological information obtained by the Hokkaido Tokyo University Forest at the closest observatory point (at 730 m of elevation) to the study area are: mean annual temperature, 4.48C; minimum monthly temperature, 9.58C; and maximum monthly temperature, 19.48C. Annual precipitation measured near the University Forest was about 1200± 1500 mm. Maximum snow depth is about 2 m, and the ground is continuously covered with snow from November to April. (The University Forest in Hokkaido, 1977). The soil around 700 m elevation, the closest elevation at which the soil type has been reported, is classi®ed as brown forest soils (Japanese soil taxonomy). Decomposition of litter and humus is slow because of the cold temperature over half of the year. The A-horizon is generally thick, dark brown and granular in its structure. The B-horizon is generally brown-to-red brown, very hard and compact in its structure. Some leaching of iron is taking place in the upper horizon, but not to the degree where typical gray and red/yellow podsol horizons can be observed. The parent material is andesite. A lot of volcanic sand is mixed into the A-horizon. The topography is very gentle. (Asahi, 1963; Nakata et al., 1994). The Maeyama Forest Preserve of 1200 ha was established in 1972 in the sub-compartment No. 7a and b. Prior to 1937, selection cutting of 10% by volume had taken place for once. However, the harvest volume was relatively low in the Forest Preserve compared to the rest of the selection cutting stands in the Hokkaido Tokyo University Forest. After 1937, the Forest Preserve has received virtually no human impact except occasional measurements. There is no harvesting, planting, ground disturbance, or removal of fallen logs and snags in the Forest Preserve. Since there is no primeval sub-boreal forests left in the University Forest, no other forest in the Hokkaido
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
Tokyo University Forest is closer to the primeval sub-boreal forest than the Forest Preserve (Shibano et al., 1996). In the sub-compartment No. 7c selective cuttings were carried out several times from 1903 to 1957. After 1957, the SMS has been implemented. It was classi®ed into the category of the `selection cutting stand' where abundant seedlings are supposed to be present under overstory canopies. Selection cutting of 18±25% by volume is to be implemented with the cutting cycle of about 20 years. Diseased, senescent, un-vigorous, un-wanted, and deformed trees are removed and stand volume is kept at about 70± 80% of that of the primeval forests. In addition to the regular harvesting, trees which are dead or damaged by insects are removed to prevent the spread of diseases and insect damages. This area is close to the Forest Preserve, and environmental conditions such as meteorology, soil, vegetation type, topography are very similar to those of the Forest Preserve. 3. Methods Fourteen preserve plots with the size of 20 m20 m were established along the 680 m contour line within the sub-compartment Nos. 7a and b (the preserve stand). Fourteen selection cutting plots of 20 m20 m were established along the 660 m contour line within sub-compartment No. 7c (the selection cutting stand). Coarse woody debris were classi®ed into fallen logs, broken stems, cut stumps, and snags. Broken stems are tree trunks with <1 m height which originated from breaking of trunks, and snags are standing dead trees with >1m height. In each plot, fallen logs, broken stems, cut stumps, and snags except portions which were less than 10 cm in diameter were recorded as coarse woody debris. Diameter of both ends and length for each coarse woody debris piece were recorded. Regeneration substrates were classi®ed into six categories: fallen logs, broken stems, cut stumps, snags, root mounds, and soil. Root mounds are above ground portion of root stocks of live trees. Yezo spruce and Sachalin ®r seedlings, whose heights were 3± 130 cm, were counted and their regeneration sub-
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strates recorded. Student t-test (a0.05) was used for statistical analysis. 4. Results There were 263 and 90 m3 of total coarse woody debris in the preserve stand and the selection cutting stand, respectively (Fig. 1). A percentage of forest ¯oor covered with coarse woody debris was 7.0% in the preserve stand and 2.4% in the selection cutting stand (Fig. 2). Both of the differences were statistically signi®cant. Volumes of fallen logs, broken stems, and snags and areas occupied by them in the preserve stand were signi®cantly greater than those in the selection cutting stand. On the other hand, a volume of cut stumps and an area occupied by them in the selection cutting stand were signi®cantly greater than those in the preserve stand. Seedling densities of Yezo spruce per square meter of all regeneration substrates were not signi®cantly different between the preserve and the selection cutting stands (Fig. 3). On the other hand, those of Sachalin ®r per square meter of cut stumps and soil in the selection cutting stand were signi®cantly greater than those in the preserve stand (Fig. 4). Almost all Yezo spruce seedlings were found on coarse woody debris and none was found on soil (Fig. 5). Most Sachalin ®r seedlings were found on coarse woody debris in the preserve stand, but many of them were found also on soil in the selection cutting stand (Fig. 6). Seedling densities per hectare of forest ¯oor for both Yezo spruce and Sachalin ®r on fallen logs, and broken stems in the preserve stand were signi®cantly greater than those in the selection cutting stand. On the other hand, seedling densities per hectare of forest ¯oor for both species on cut stumps in the selection cutting stand were signi®cantly greater than those in the preserve stand. There were no Yezo spruce seedlings on soil in both stands, whereas a seedling density of Sachalin ®r on soil in the selection cutting stand was signi®cantly greater than that in the preserve stand. A total Yezo spruce seedling density per hectare of forest ¯oor in the preserve stand was signi®cantly greater than that in the selection cutting stand. On the other hand, the differences in total seedling densities of Sachalin ®r per hectare of forest ¯oor between the preserve and the selection cutting stands were not statistically signi®cant.
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Fig. 1. Average volumes of coarse woody debris in the preserve and the selection cutting stands.
Fig. 2. Average percentage of forest floor covered with coarse woody debris in the preserve and the selection cutting stands.
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23
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Fig. 3. Average seedling density of Picea jezoensis per square meter of regeneration substrates in the preserve and the selection cutting stands.
Fig. 4. Average seedling density of Abies sachalinensis per square meter of regeneration substrates in the preserve and the selection cutting stands.
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Fig. 5. Average seedling density and regeneration substrate of Picea jezoensis per hectare of forest floor in the preserve and the selection cutting stands.
Fig. 6. Average seedling density and regeneration substrate of Abies sachalinensis per hectare of forest floor in the preserve and the selection cutting stands.
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5. Discussion The present study suggests that selection cutting in the sub-boreal forests of the Hokkaido Tokyo University Forest indeed leads to a signi®cant reduction of Yezo spruce seedlings, and no signi®cant change in Sachalin ®r seedlings. This is inconsistent with what Nagaike et al. (1999) reported, namely repeated selective harvesting will lead to a decrease in seedling regeneration of both species, because the main regeneration substrates for the two coniferous species in selectively harvested stands are fallen logs and cut stumps. Although the reason for the different effects of selection cutting on seedling densities between Yezo spruce and Sachalin ®r is not clear from the result of this study, it may be due to the different characteristics of regeneration between the two coniferous species. Yezo spruce seedlings regenerated only on coarse woody debris whereas many Sachalin ®r seedlings were found on soil (Figs. 5 and 6), being consistent with some previous ®ndings that Yezo spruce seedlings rarely regenerate on A horizon soil, whereas Sachalin ®r seedlings do (Takahashi et al., 1981, 1984; Iguchi et al., 1992). The difference in regeneration substrates might be explained by the difference in susceptibilities of the two conifers to Racodium snow blight (Racodium therryanum Thuem.). It is a serious disease which attacks seeds and seedlings of Yezo spruce and Sachalin ®r under snow during winter (Sato et al., 1960). The disease fungus is distributed where organic matters are abundant, but rarely was it found on fallen logs (Cheng and Igarashi, 1987; Cheng, 1989; Takahashi, 1991). Since seeds and seedlings of Sachalin ®r are more resistant to Racodium snow blight than those of Yezo spruce (Takahashi, 1979; Cheng and Igarashi, 1990; Takahashi and Ogasawara, 1990), the fungus might prevent regeneration of Yezo spruce on soil. A ground disturbance by harvesting could enhance regeneration of Sachalin ®r on soil. Litters are removed and soil is disturbed by harvesting with heavy machinery in some parts of the selection cutting stand, whereas there are virtually no human impacts in the preserve stand. Removal of litters, damaging bamboo grass, and raking of A horizons by heavy machinery are effective for regeneration of some woody species (Matsuda and Takikawa, 1985).
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The signi®cant increase of Sachalin ®r seedling density on soil in the selection cutting stand (Figs. 4 and 6) could be due to the soil disturbance by harvesting activities. Different reactions of the two coniferous species to improved light conditions after selection cutting could not be ignored, either. Fujimura et al. (1992) reported that arti®cial shading does not affect height growth of Yezo spruce, but that of Sachalin ®r seedlings is reduced. Fukuchi et al. (1979) reported that small seedlings of Sachalin ®r do not grow and gradually disappear in a dense plantation forest and an improved light condition by thinning is effective for natural regeneration of the species. The signi®cant increases of seedling densities of Sachalin ®r per square meter of soil and cut stumps (Fig. 4) may be due to the improved light conditions by selection cutting which reduces mortality of Sachalin ®r seedlings. Further research is needed to clarify to what extent each of the above three reasons contributes to the difference in effects of selection cutting on seedling densities between Yezo spruce and Sachalin ®r. Although present species composition of the seedlings does not precisely re¯ect the species composition in the future, results of the present study suggest a possibility that Sachalin ®r becomes more dominant and Yezo spruce less dominant under the SMS in the sub-boreal forests of the Hokkaido Tokyo University Forest. Especially, if no fallen log is supplied in the future, Yezo spruce seedling bank will diminish further as coarse woody debris which presently exists continues to decay. Thus, it might be dif®cult to maintain Yezo spruce resources under the SMS. Kubota (1996) pointed out that regeneration strategies are often ignored in natural forest management plans although ensuring regeneration is essential for sustainable forest management. The SMS might fail to meet a requirement for sustainable forest management, a regeneration strategy of Yezo spruce. To ensure natural regeneration of Yezo spruce caution must be taken so that heavy machinery used in harvesting does not damage coarse woody debris. In addition, forest management policy needs to be changed so that certain amounts of coarse woody debris, a crucial regeneration substrate for Yezo spruce, is supplied under the SMS.
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Acknowledgements The authors thank the staff of the Hokkaido Tokyo University Forest, especially Mr. Yasuo Takahashi and Mr. Shinsaku Shibano, for providing the management information of the forest. References Asahi, M., 1963. Studies on the classification of forest soils in the Tokyo University Forest, Hokkaido (in Japanese, with English Abstract. Bull. Tokyo Univ. For. 58, 1±132. Cheng, D., 1989. Studies on Racodium therryanum-caused in-soil seed rot with special reference to its impact on natural regeneration of Yezo spruce (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 46, 529±575. Cheng, D., Igarashi, T., 1987. Fungi associated with natural regeneration of Picea jezoensis Carr. in seed stage Ð their distribution on forest floors and pathogenicity to the seeds. Res. Bull. Exp. For. Hokkaido Univ. 44, 175±188. Cheng, D., Igarashi, T., 1990. Comparison of susceptibility to Racodium therryanum infection of seeds and seedlings of four coniferous species (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 47, 125±136. Fujimura, Y., Koike, T., Tabuchi, R., Takahashi, K., 1992. Effects of the artificial shading on the growth of Picea jezoensis (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 40, 98±100. Fukuchi, M., Kikuzawa, K., Asai, T., Mizutani, E., 1979. Todomatsu no rinnai koushin ni kansuru kenkyu Ð jittai chousa no kekka kara (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 28, 115±117. Haruki, M., Itagaki, T., Namikawa, K., Ishikawa, Y., 1990. Forest construction in the Tokachi River Watershed Wilderness Area, in the Daisetsuzan National Park, northern Japan (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 47, 83±123. Hiura, T., Sano, J., Konno, Y., 1996. Age structure and response to fine-scale disturbance of Abies sachalinensis, Picea jezoensis, Picea glehnii, and Betula ermanii growing under the influence of a dwarf bamboo understorey in northern Japan. Can. J. For. Res. 26, 289±297. Iguchi, K., Ogasawara, S., Kasahara, H., Satou, S., Watanabe, S., 1992. Disappearance and growth of seedlings on different seed beds of seven provenance of Picea jezoensis (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 40, 59±61. Kato, R., 1952. The vegetation of the Tokyo University Forest in Hokkaido (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 43, 1±18. Kubota, Y., 1996. Logging strategy of primary forest based on the regeneration process (in Japanese with English Abstract). J. Jpn. For. Soc. 78, 79±83. Kubota, Y., Konno, Y., Hiura, T., 1994. Stand structure and growth patterns of understorey trees in a coniferous forest,
Taisetsuzan National Park, northern Japan. Ecol. Res. 9, 333±341. Matsuda, K., Takikawa, S., 1985. Practical study on promotional treatment of natural regeneration (in Japanese, with English Abstract). Res. Bull. Exp. For. Hokkaido Univ. 42, 909±940. Nakata, M., Tanaka, H., Yagi, H., 1994. Altitudinal changes in vegetation and soils on Mt. Dairoku, central Hokkaido, Japan (in Japanese, with English Abstract). Jpn. J. Ecol. 44, 33±47. Nagaike, T., Kubota, Y., Watanabe, N., 1999. The effects of selective logging on stand structure and the regeneration of subboreal forests in Hokkaido, northern Japan. J. For. Res. 4, 41±45. Sato, K., Shoji, T., Ota, N., 1960. Studies on the snow molding of coniferous seedlings. II Dark snow blight caused by Racodium therryanum Thuem (in Japanese, with English Abstract). Bull. Govt. For. Exp. Sta. 124, 21±100. Shibano, S., Okamura, K., Takahashi, Y., Watanabe, S., 1996. Techniques for establishing a large permanent research plot for studies of forest dynamics in a mixed forest zone (in Japanese, with English Abstract). Jpn. J. Ecol. 46, 155±168. Shibata, S., 1988. Studies on the management of natural forests Ð an experiment of natural forest management in the Tokyo University Forest in Hokkaido (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 80, 269±397. Takahashi, I., 1979. Studies on mycoflora and diseases of coniferous trees at the central part of Hokkaido, Japan Ð special reference to Ascomycetes, Fungi imperfecti and Uradinales (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 69, 1±143. Takahashi, I., 1991. Studies on the mycofloral succession on Yezo spruce (Picea jezoensis Carr.) in various stages of growth, with special reference to the role of fungi in the natural regeneration of the host (in Japanese, with English Abstract). Bull. Tokyo Univ. For. 86, 201±273. Takahashi, I., Ogasawara, S., 1990. Preventive effect of dark snow blight on young seedlings of Todo fir and Yezo spruce by soil treatment with sterilization (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 38, 113±115. Takahashi, I., Miyamori, Y., Shibano, H., Hatano, K., 1981. Ezomatsu Todomatu no tennenkoushin ni kansuru kenkyu Ð kakushu hashudoko niokeru chibyou no hassei shoushitsu (2kanen no keika) (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 30, 79±81. Takahashi, I., Miyamori, Y., Hatano, K., 1984. Ezomatsu Todomatu no tennenkoushin ni kansuru kenkyu Ð rinchi niokeru kakushu hashudoko no seiiku joukyou. (3±5nen keika) (in Japanese). Trans. Meetings Hokkaido Branch Jpn. For. Soc. 33, 62±64. Takahashi, N., 1971. Rinbun segyo ho Ð sono kangaekata to jissai. Zenkoku Ringyo Kairyo Fukyu Kyokai. Tokyo, 127 pp., (in Japanese). Takahashi, N., 1993. Rinbun segyo ho no riron to jissen (in Japanese). Gakujutsugeppo 46, 6±11. The University Forest in Hokkaido, 1977. Meteorological observations at different elevations of Mt. Dairoku, the Tokyo
M. Nakagawa et al. / Forest Ecology and Management 146 (2001) 15±23 University Forest in Hokkaido. Records in the period 1972± 1975 and short discussion on them (in Japanese, with English Abstract.). The miscellaneous information (in Japanese, with English Abstract), Tokyo University Forests 21, pp. 22±47. Watanabe, S., Sasaki, S., 1994. The silvicultural management system in temperate and boreal forests: a case history of the
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Hokkaido Tokyo University Forest. Can. J. For. Res. 24, 1176±1185. Yamamoto, H., 1994. Natural forest management based on selection cutting and natural regeneration. Proceedings of IUFRO international workshop on sustainable forest managements. ISBN 4-9900381-O-X, pp. 10±22.