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The chemical composition of plant litter of black locust (Robinia pseudoacacia L.) and its ecological role in sandy ecosystems
Acta Ecologica Sinica 29 (2009) 237–243
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The chemical composition of plant litter of black locust (Robinia pseudoacacia L.) and its ecological role in sandy ecosystems Oimahmad Rahmonov * ´ ska 60, PL-41-200 Sosnowiec, Poland Department of Physical Geography, University of Silesia, Be˛dzin
a r t i c l e
i n f o
Keywords: Robinia pseudoacacia Canopy effect Plant development Soil formation Plant litter Plant chemical composition Nutrient compounds Site condition
a b s t r a c t Robinia pseudoacacia is a North American species and in Poland it is currently invasive in character. It is used to recultivate sand excavations and others, most often in order to make the process of plant and soil succession more advanced. It has been observed that in places were R. pseudoacacia dominated in plantations, the herbaceous vegetation under the trees is poor and sometimes other vascular plants are not appearing at all. Plants usually overgrow the space out of the canopy shade. The positive influence of R. pseudoacacia on a habitat is primarily connected with the chemical composition of plant litter, as well as with the biology of the species. Chemical composition of R. pseudoacacia litter has been researched. The greatest accumulation of elements has been observed in the following parts: green leaves (Ca > K > Mg > P > Si > Na > Fe > Zn > Al > Mn) and leaf litter (Ca > K > Mg > Si > Fe > P > Na > Al > Zn > Mn). Similar regularities are observed in the remaining litter of R. pseudoacacia. It must be emphasized that nitrogen occurs in similar quantities in particular samples and it varies from 1.01 to 2.65%. The plant litter reaction (pH) vary from acid to weakly acid. In a short period of time under the canopy of R. pseudoacacia a 10 cm organic and humus horizont (O/A) has developed. Ó 2009 Ecological Society of China. Published by Elsevier B.V.
1. Introduction In the majority of terrains degraded by open-cast mining in southern Poland and other areas of Europe Robinia pseudoacacia is applied to perform land reclamation. It belongs to the family of Fabaceae and it is commonly known as the black locust. This is the species of small ecological requirements and therefore it quickly adapts in areas characterised by extreme environmental conditions for example: without soil cover. Considering it, the species has habitat-forming character and therefore it is often planted at poor and loose sand to fix it and enrich it in biogens. R. pseudoacacia is an alien species in Poland and it has invasive character. Its seeds were brought to Europe at the beginning of the 17th century and it has been widely planted since that period [1]. Black locust has been planted in Poland since the mid-18th century and now it is present all over the country, although it is no frequent as in some other parts of Europe [2]. R. pseudoacacia can propagate in a generative and vegetative way, therefore it is widespread species within the zone of temperate and subtemperate climates [3]. It is used at formation of shelterbelts, as decorative element and at land reclamation of degraded terrains [4]. It often creates dense stands, which through shadowing larger and larger areas reduces * Tel.: +48 0323689306. E-mail address: [email protected]
the neighbouring vegetation. In the tree stand, where R. pseudoacacia predominates, the undergrowth is very poor or absent. R. pseudoacacia, similarly to other arborescent species, differently influences the initiation of soil forming process and its further development, especially through influence of phytogenic field [5–9]. Specific species influence of R. pseudoacacia is conditioned by the chemical composition of its plant litter and the richness in nutrients. Plants, producing different secondary metabolites, release them into the soil through secretion systems of living tissues and after decomposition of their debris enrich it. Some of these substances are the only source of nutrients for plants. Decomposing leaves and other parts of R. pseudoacacia enrich poor sands in organic colloids and nutrients every year. Especially important is nitrogen, which essentially influences the rate and development of ecosystem processes. The nutrient availability in forest ecosystems depends on the effective biogeochemical cycle within biogeocenosis. Through this cycle nutrients return to the soil in the form of plant litter and they create an organic level. In the result of decomposition and mineralization nutrients are released and then they are uptaken by plants again. The rate of humification and mineralization of organic matter depends on: temperature, humidity conditions, physical and chemical properties of plant material delivered to the soil, as well as on the richness of organisms which are responsible for decomposition of the organic matter [10–14]. The rate of
1872-2032/$ - see front matter Ó 2009 Ecological Society of China. Published by Elsevier B.V. doi:10.1016/j.chnaes.2009.08.006
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decomposition of plant litter and the rate of nutrients releasing essentially influence the heterogeneity of habitat and the further differentiation of ecosystems. Branches and leaves within the canopy are the main ‘‘tank” of nutrients retaining them in the place [15]. Therefore, investigation on chemical composition of plant litter (leaves, branches, bark and others) and its influence on the fertility of soil and their functioning in different ecosystems were performed many times [9,10,16– 21]. The aim of this study is (1) the attempt to present the influence of R. pseudoacacia on the rate of development of vegetationsoil cover in reclaimed sandy areas, and (2) the determination of chemical composition of the litter of R. pseudoacacia and the role of this species in potential enrichment of sandy habitat in nutrients and its further modification. 2. Materials and methods Research were performed in the eastern part of the Silesian Upland (S Poland) in the area of reclaimed sand excavation (50200 18, 800 N and 19280 57, 800 E). Main species used for this aim was R. pseudoacacia, which actually creates here one-species plantation and is of essential importance in the further shaping of ecological systems. The age of this plantation is estimated to be about 20 years. Within the plantation intentionally isolated singular clumps of this species were founded to determine the influence of single individual on the development of vegetation-soil cover. Under the canopy of R. pseudoacacia scrupulous plant mapping on the scale of 1:100 was made (Fig. 1A). Areas beyond the canopy were not mapped, they were mostly covered with nitrophylous species. Plant litter of R. pseudoacacia such as: bark, fine branches, fine roots, green leaves, fallen leaves which did not undergo the mineralization yet, and accumulated under their canopy was once collected in order to determine chemical composition of plant litter
Padus seroptina
A
C
3. Results
..............
3.1. Vegetation development
14
1
Canopy zone of Robinia pseudoacacia
plant litter
Calamagrostis epigejos
2m 1
2
3
4
5
6
7
8
9
10
11
12
13
Depth [cm]
0
14 Ol
5 10 15 20
and its role in the enrichment of sandy substratum with nutrients. Green leaves were sampled directly from the plant in September, whereas fallen leaves were collected in the period of the autumn maximum of vegetation litter. The content of the following elements: C, N, Ca, Mg, K, Na, P, Fe, Al, Zn and Si, Mn, Mo, Co, Cd, Pb and Sr were determined in the samples taken. The total content of elements in plant material was determined after mineralization ‘‘in wet conditions” in the mixture of HNO3 + HF + H2O2 in closed system (in microwave apparatus MLS-1200MEGA240 of Milestone firm). The determination of particular elements was carried out by means of absorption method of atom spectrometry, excluding Na and K (method of emission flame spectrometry), C (method of Alten) and N (method of Kjeldahl). Plant materials for laboratory analyses were prepared according to direction by MacNaeidhe [22], Markert [23], Clément [24] and Ostrowska et al. [25]. Soil analysis: transect method – on transect lined under canopy of black locust at 1 m intervals along the whole length of the transect the thickness of the organic horizon (O) and the humus horizon (A) under the canopy of R. pseudoacacia was measured and soil samples from the humus layer were taken for chemical analysis. Moreover, the following analyses were made according to standards used in Poland: loss ignition – in the temperature of 550 °C, pH-reaction by means of potentiometric method with applying of glass electrode (in H2O and 1-mole KCl), organic carbon (Corg) in organic horizons by means of Alten’s method and in mineral horizons by means of Tiurin’s method, total nitrogen (Nt) by means of Kjeldahl’s method, available phosphorus (Pavailab) by Egner–Riehm’s method, hydrolytic acidity (Hh) by Kappen’s method, exchangeable aluminium (Al3+) and exchangeable hydrogen (H+) by means of Sokolow’s method, the total content of P, Mg, Na, K after samples extraction by 1-mole CH3COONH4 of pH 7; the measurement by means of apparatus ASA (firm Solar): Ca and Mg – in absorption version, whereas Na and K – in emission version.
Of - horizon
B A - horizon
Fig. 1. The investigation transect in the zone of influence Robinia pseudoacacia: (A) scheme of plant distribution under canopy; (B) differentiation of organic horizons (O with subhorizons Ol and Of) and humus (A) horizon. The number of points (1– 14) in transect corresponding with numbers of Figs. 2–4.
R. pseudoacacia, covering the investigation area, creates biogroups composed of three trunks, which are 11 m high. The biogroup has two-layer vertical structure: top and undergrowth. In the first case most of all R. pseudoacacia occurs, whereas in the second one – Padus serotina. The oldest individuals of R. pseudoacacia are accompanied by young generation of this species. The oldest specimen from among of all individuals studied is about 20 years old. Singular small individuals of Betula pendula, Caragana arborescens and Crataegus monogyna are met within the clump, but they are not of large biocenotic importance at this stage. In the shadow made by canopy zone the occurrence of seedlings and mature individuals of P. serotina has mass character. Whereas under the canopy of R. pseudacacia, the development of the following generations of this species both on vegetative and generative way is observed. Calamagrostis epigejos – a tall grass, representing herbaceous plants within the canopy zone – occurred in the form of small patches (Fig. 1A). Large patches of C. epigejos occur when R. pseudoacacia is only 2 m high, i.e. at the initial stage. These were observed in the neighbourhood of the clump investigated. Actually, the singular clumps of this species also occur at the edge of plantation. Apart from the influence of the canopy zone, the following singular species: Poa compressa, Holcus mollis, Euphorbia esula, Epipactis atrorubens, Festuca ovina and Linaria vulgaris were noted on isolated localities. Under R. pseudoacacia its dead parts such as:
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branches, leaves, bark occurred at the majority of plots studied. They hindered the access of other plant seeds to the soil bank of seeds. 3.2. Soil morphology The soil forming processes under the canopy of R. pseudoacacia presents the differentiation in relation to morphology on: organic (O) and humus (A) horizons. Organic and humus horizons of the largest thickness occur in the central part of the canopy, on contrary to the edge or the zone beyond the canopy (Fig. 1B). Organic horizon (O) is divided into subhorizons Ol, Of and rarely – Oh. Subhorizon Ol – is made by undecomposed litter (branches, leaves and other) of R. pseudoacacia, as well as by leaves and acorns of Quercus rubra occurring about 50 m from species investigated. Chemical indices which characterize this subhorizon have the following values: ignition losses – 36%, content of Corg – 20%, nitrogen Nt – 1%, ratio C/N – 26, Ptot. – 629 mg/kg, Pavailab.– 51 mg/kg, Mg – 230 mg/kg and pH – 4.8 in water and 4.5 in KCl. Subhorizon Of – is made by partially decomposed above-mentioned litter, debris is still recognised, it is overgrown with mycelium, there are also insect excrements. Chemical indices in this subhorizon have slightly other values: ignition losses – 86%, content of Corg – 42%, nitrogen Nt – 2.47%, ratio C/N – 17 Ptot. – 961 mg/kg, Pavailab.– 164 mg/kg, Mg – 335 mg/kg and pH – 5.4 in water and 4.5 in KCl. Subhorizon Oh – very thin, is composed of already not recognised plant remains with humus lens settled by fine roots, this substratum is dark brown, it is mellow and humid. Horizon A – medium- and fine-grained sand, loose, of aeolian origin, dark grey (10Y/R). Initial soils creating under this species are characterised by profile structure of Ol–Of–Oh–A–A/C–C type. Name of soil according to Systematics of Soil of Poland [26]: lithogenic soils, mineral without carbonates initial and weakly developed, loose initial soils (regosols), according to FAO [27]: Haplic Arenosols, WRB [28]: Protic Arenosols. Chemical properties of humus horizons under canopy of R. pseudoacacia The soil forming under the canopy of R. pseudacacia is characterised by acid and weakly acid pH-reaction, which fluctuates within the range 4.6–5.2 in water and 4.2–4.8 in KCl. Hydrolythic and exchangeable acidity (H+, Al3+) indicates a certain similarity in some areas of canopy and beyond canopy zones (Fig. 2). Losses ignition and contents of organic carbon, nitrogen along the transect is differentiated. The largest values of them were stated in the point No 5. Ratio C/N is in general narrow along the whole transect (Fig. 3) and it betokens the rapid process of mineralization and biological activity of the soil. Contents of available forms of P, Mg, K, Na (Fig. 4) for plants in humus horizon are low and the lowest amount among them is typical for phosphorus. The highest values of elements investigated and were most often stated near trunks and in central part of the canopy zone (Figs. 2–4). 3.3. Chemical composition of plant litter of R. pseudoacacia Results of analysis in relation to chemical composition of macroelements (C, N, P, Mg, K, Ca, Na) and microelements (Mn, Mo, Co, Fe, Al, Zn, Si, Cd, Sr) of black locust’s selected parts (green leaves, leaf litter, bark, branches and roots) are presented in Table 1. The plant litter reaction (pH) varies from acid (bark and fine twigs – 3.6) to weakly acid (green leaves and litter – 5.3). It must be emphasized, that nitrogen occurs in similar quantities in particular samples and it varies from 1.01 to 2.65%. The greatest accumulation of elements has been observed in the following parts: green leaves (Ca > K > Mg > P > Si > Na > Fe >
5.5
pH
5
H2 O
KCl
4.5
4
4.5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
13
14
hydrolitic acidity (Hh)
[cmol(+)*kg-1]
3.5 2.5 1.5
0.5 0
4.5
1
2
3
4
5
6
[cmol(+)*kg-1]
7
8
9
10
11
12
H
exchange acidity
+
Al
3+
3.5 2.5 1.5
0.5 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Fig. 2. Soil reaction and exchange acidity of humus horizon (A) under canopy of Robinia pseudoacacia.
Zn > Al > Mn), leaf litter (Ca > K > Mg > Si > Fe > P > Na > Al > Zn > Mn). Similar regularities are observed in the remaining litter of R. pseudoacacia. The particular contents of elements investigated in plant material assume the shape of the following series: green leaves: Ca > K > Mg > P > Si > Na > Fe > Zn > Al > Mn > Sr > Pb > Mo > Co > Cd leaf litter: Ca > K > Mg > Si > Fe > P > Na > Al > Zn > Mn > Pb > Sr > Mo > Co > Cd bark: Ca > Fe > Si > Al > K > Mg > Na > P > Zn > Pb > Sr > Mn > Mo > Co > Cd branches: Ca > Fe > K > Si > Na > Al > Mg > Zn > P > Pb > Sr > Mn > Mo > Co > Cd roots: Si > Ca > K > Al > Fe > Na > Mg > P > Zn > Mg > Pb > Sr > Mo > Co > Cd Among elements investigated almost everywhere the first place in the series is occupied by Ca, whereas the last positions are typical for Mo, Co and Cd. High contents of Ca are of essential importance in the development of vegetation in sandy areas through partial deacidification and regulation of soil pHreaction.
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3.5
[%]
loss ignition
3 2.5 2 1.5 1 0.5 1 1.8
2
3
4
5
6
7
[%]
8
9
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11
12
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14
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11
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14
Corg
1.4
1 0.6 0.2 0 0.14
1
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7
[%]
8
9
Ntot
0.1
0.06
0.02 0
1
2
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7
8
9
70
C/N 50
30
10 0
1
2
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4
5
6
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9
Fig. 3. Some chemical properties of humus horizon (A) under canopy of Robinia pseudoacacia.
4. Discussion Black locust is a deciduous tree of variable form ranging from small suckering clumps to tall individuals growing up to 8–24 m in height and 0.3–0.8 m in diameter. The short trunk usually divides not far above the ground forming multiple-stem crown. Black locust is a legume plant and has the ability to fix nitrogen from the air with the aid of nitrogen fixing bacteria on its roots. As a result of this ability, it grows readily in poor infertile soils. R. pseudoacacia can also act as a natural supplier of nitrogen to other plants in the whole landscape [3]. It grows very fast when young and, as a result, even in young black locust woods the nitrogen content of
soil can be considerably higher than in woods of other species at the same age [29]. Symbiotic nitrogen-fixation and the fast growth of black locust contributed to the increase in soil NH4–N. Differences in nitrogen availability and light conditions appeared to cause the strong divergence in the development of different types of young woods [30]. In the undergrowth of the tree stands, where R. pseudoacacia predominates, herbaceous plants rarely occur [4]. In the case of sandy areas, the essential role is also played by shading and elimination of photophilous species. The occurrence of psammophilous species exclusively at the edge of the canopy in sun-heated places is evident. This causes the floristic poorness in brushwood with contribution of this species, especially under the canopy. Under the R. pseudoacacia most of all nitrophilous species occur. In sandy areas there are most often not similar species, and the occurrence of Calamagrostis epigejos under the canopy of R. pseudoacacia is not accidental and is here of important significance in the process of biomass accumulation [14]. This species together with other nitrophilous species and also with R. pseudoacacia creates plant communities of synanthropic-ruderal character at wastelands and along railway tracks [31]. The group of species creating communities together with R. pseudacacia consists mostly of species adapted for substratum with very high content of nitrogen. They are as follows: Acer negundo, Sambucus nigra, Padus serotina, Tanacetum vulgare, Chelidonium majus, Urtica dioica, Humulus lupulus (if the terrain is slightly humid), Rubus fruticosus, Rubus idaeus, Arctium tomentosum, A. lappa, A. minus, Calamagrostis epigejos, Solidago canadensis, S. virga-aurea [4], and sporadically Lupinus polyphyllus. It can even create brushwood with Reynoutria japonica and R. sachalinensis. Pines can sow under the canopy of R. pseudoacacia, but they extinct very quickly. Such specific species composition can be caused by high content of nitrogen in upper soil horizons. The lack of vegetation under the canopy has also the connection with potential allelopathic abilities of R. pseudoacacia. Researches performed by Nasiri [32] proved, that the lack of vegetation, especially herbaceous one, under the canopy of R. pseudoacacia is associated with alleopathic activity of the substance releasing during its litter decomposition. These authors proved – by means of chromatographic method – the occurrence of alleopathic substances such as: robinetin, myricetin and quercetin in leaves and other parts of this species. The phenomenon of allelopathy plays the essential role at this species invasion on larger and larger areas. The second reason of floristic poorness in sandy areas can be the lack of plant species properly adapted to such surfaces. Under the canopy of black locust in very short time as for the pedogenesis, the formation of humus and organic horizons (O), dividing into subhorizons (Ol–Of–Oh), creating raw humus (above ground litter) are observed. The above ground litter is the only source of nutrients in forming communities at poor loose sands. The basic biogens, which were released during the above ground litter mineralization are taken by plants and that way they continue the biological cycle. Therefore the intensity of plant remains mineralization influences the amount of potential nutrients available for plants. Bogatyrev [33] considers the formation of organic horizon in ecosystems for one of the most important biogeocenotic processes. Humus and organic horizons in sandy areas play very essential role in functioning of poor ecosystems [9]. Well-developed horizons are observed near trunks and they should be considered as the oldest within the canopy. Such rapid development undoubtedly has connection with ecology and biology of species and its different chemical composition. The formation of soil mosaic in short period of time was observed by other authors in sandy areas of primary succession [8,34], as well as in forest communities of climax character [5–7,35,36]. The soil developing under the canopy of R. pseudoacacia is characterised by spatial variety (even on small scales) and it reveals the dependence on
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[mg/kg]
Mg
30
20
10
0 25
1
2
3
4
5
6
7
8
9
10
11
12
13
14 110
[mg/kg]
K
20
90
15
70
5
50
0
1
2
3
4
5
6
7
25 [mg/kg]
8
9
10
11
12
13
14
30
7
Na
[mg/kg]
1
2
Pt
3
4
5
6
8
7
[mg/kg]
9
10
11
12
13
14
10
11
12
13
14
Pavailable
5
3
20
1 0 15
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
4
5
6
8
7
9
14
Fig. 4. The contents of available forms of Mg, K, Na, P and total Ptot. of humus horizon (A) under canopy of Robinia pseudoacacia.
Table 1 The chemical composition of plant litter of Robinia pseuodacacia. Samples
C
N
C/N
P
Si
Mn
Mg
Na
K
Ca
Mo
Co
Fe
Al
Zn
Cd
Pb
Sr
pH
n=6 % Green leaves Leaf litter Bark Branches Root
53 56 59.2 57.4 46.4
(mg/kg) 2.65 2.13 1.84 1.01 2.19
20 26 32 56 21
948 708 236 76 512
668 1686 1980 638 8242
110 44 30 16 98
1618 2270 462 338 798
464 592 408 460 846
6554 3312 810 640 3972
the distance from the trunk. The variety in soil properties is the reflection of size and architecture of the canopy of predominating species in the clump and undergrowth. Plants, uptaking elements from the soil and delivering organic remains instead, significantly influence the content of different elements. The majority of researches proved that specific influence of species on the ecosystem results just from chemical composition of different fractions of its litter, especially from leaves [37,38]. The content of nutrients in leaves is commonly known as the effect of food status in plants [39,40]. The leaves contain the majority of nutrients circulated in forest and brushwood ecosystems [41,42]. Both endogenous and exogenous factors cause the temporal and spatial changes in nutrient content in leaves [43–45]. Spatial variety can be primarily caused by the variety of the very soil [46,47], terrain topography, vertical and horizontal structure of
19116 25574 13478 9398 5976
10 16 22 12 4
2 4 0.2 4 2
258 942 2276 932 2786
141 478 1814 360 3104
200 180 96 116 278
0.0 0.2 0 0 1.4
12 42 84 68 68
22.2 31.6 37.4 39.6 35.2
H2O
KCl
5.4 5.3 4.0 4.0 4.8
5.2 5.1 3.7 3.7 4.5
phytocenoses and human impact [9]. The litter of R. pseudoacacia is relatively rich in nutrients in relation to some tree species [48] and it weakly removes nutrients from dead remains before its falling. Thus they enrich the soil after decomposition. For the element return, the most important components of litter were leaves. It is because together with this fraction more than a half of biogens is delivered. It mostly results from their predominating contribution in the litter. In the case of nitrogen the important role is played by leaves and roots, where it is accumulated in the largest amount. Nitrogen accelerates the process of succession in this area although it is considered to be deficit element, especially in poor sands. Enrichment of soil nitrogen by black locust may therefore favour the appearance of specific combinations of associated species even in young woodland, and induce considerable local divergence in the composition of secondary wood communities compared with
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those under non-symbiotic tree species [49]. As suggested the authors [49], the indirect effect of black locust on the species composition of the field layer is likely to be strongest on poor sandy soil where nitrogen is the main limiting soil resource. 5. Conclusion R. pseudoacacia plays positive role in the process of sand fixing and soil formation in areas undergoing land reclamation by means this species. Sandy areas reclaimed by R. pseudoacacia are fixed enough and they are not threatened by wind erosion. Annual production of leaves and their rapid decomposition makes the main source of organic matter causing the formation of raw humus and after mineralization it delivers macro- and microelements into poor sandy ecosystems. It is important moment during the development process of initial soils. Relatively rapid processes of soil formation were observed under the canopy in the neighbourhood of trunks of R. pseudoacacia. This species has the ability to fix free atmospheric nitrogen as the additional source of soil enrichment. Results from performed researches indicate that its role in regeneration of poor ecosystems is mostly connected with the formation of forest. However, the species negatively influences the biological diversity. The flora is most often very poor in areas where this species occurs. Therefore, before land reclamation we should answer the question: do we want plantation with R. pseudoacacia or ecosystem which is typical for sandy areas? If we choose the second option, then these areas should be kept to regeneration in a way of natural succession. Acknowledgements The author gratefully acknowledge Kamil and Małgorzata Rahmonovs for help with field works. The author thank an anonymous reviewer for their critical and constructive comments. I also thank Prof. Alicji MacBarc for her kind help in improving the language of this paper. References [1] H. Ellenberg, Vegetation Ecology of Central Europe, Cambridge University Press, Cambridge, UK, 1988. pp. 1–753. [2] C. Pacyniak, Locust tree (Robinia pseudoacacia L.) in conditions of Polish forest environment, Roczniki Akademii Rolniczej w Poznaniu 111 (1981) 1–85. [3] H.S. Moon, S.Y. Jung, S.C. Hong, Rate of soil respiration at black locust (Robinia pseudoacacia) stands in Jinju area, Korean Journal of Ecology 24 (2001) 371– 376. [4] W. Oles´, O. Rahmonov, M. Rzetala, I. Malik, S. Pytel, The ways of industrial wastelands management in the landscape of Silesian Region, Ekológia (Bratislava) 23 (1) (2004) 244–251. [5] P.J. Zinke, The pattern of influence of individual forest trees on soil properties, Ecology 43 (1962) 130–133. [6] D. Binkley, The influence of tree species on forest soils: processes and patterns, in: Proceedings of the Tree and Soil Workshop 1994, Agronomy Society of New Zealand Special Publications, New Zealand, Lincoln University Press, 1996, vol. 10, pp. 7–33. [7] R. Bednarek, H. Dziadowiec, U. Pokojska, Pedological aspect of variability, Ecological Questions 1 (2002) 35–41. [8] O. Rahmonov, M. Rzetala, I. Malik, W. Oles´, S. Pytel, Possibilities of applying Salix acutifolia in revitalizing areas transformed by anthropogenic activity, Ekológia (Bratislava) 23 (2004) 280–290. [9] O. Rahmonov, Relations Between Vegetation and Soil in Initial Phase of Succession in Sandy Areas (in Polish), University of Silesia Press, Katowice, 2007. pp. 1–200. [10] H. Dziadowiec, Decomposition of litters in selected forest ecosystems (mineralization, nutrient release, humification) (in Polish), Rozprawy, Torun´, 1990, pp. 1–137. [11] H. Dziadowiec, A. Kwiatkowska, Mineralization and humification of plant fail in mixed forest stand of the reserve ‘‘Las Piwnicki” near Torun´, Ekologia Polska 28 (1) (1980) 111–128. [12] J.M. Facelli, S.T.A. Pickett, Plant litter: its dynamics and effect on plant community structure, Botanical Review 57 (1) (1991) 1–33. [13] M.-M. Coûteaux, P. Bottner, B. Berg, Litter decomposition, climate and litter quality, Tree 10 (2) (1995) 63–66.
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Acta Ecologica Sinica journal homepage: www.elsevier.com/locate/chnaes
The chemical composition of plant litter of black locust (Robinia pseudoacacia L.) and its ecological role in sandy ecosystems Oimahmad Rahmonov * ´ ska 60, PL-41-200 Sosnowiec, Poland Department of Physical Geography, University of Silesia, Be˛dzin
a r t i c l e
i n f o
Keywords: Robinia pseudoacacia Canopy effect Plant development Soil formation Plant litter Plant chemical composition Nutrient compounds Site condition
a b s t r a c t Robinia pseudoacacia is a North American species and in Poland it is currently invasive in character. It is used to recultivate sand excavations and others, most often in order to make the process of plant and soil succession more advanced. It has been observed that in places were R. pseudoacacia dominated in plantations, the herbaceous vegetation under the trees is poor and sometimes other vascular plants are not appearing at all. Plants usually overgrow the space out of the canopy shade. The positive influence of R. pseudoacacia on a habitat is primarily connected with the chemical composition of plant litter, as well as with the biology of the species. Chemical composition of R. pseudoacacia litter has been researched. The greatest accumulation of elements has been observed in the following parts: green leaves (Ca > K > Mg > P > Si > Na > Fe > Zn > Al > Mn) and leaf litter (Ca > K > Mg > Si > Fe > P > Na > Al > Zn > Mn). Similar regularities are observed in the remaining litter of R. pseudoacacia. It must be emphasized that nitrogen occurs in similar quantities in particular samples and it varies from 1.01 to 2.65%. The plant litter reaction (pH) vary from acid to weakly acid. In a short period of time under the canopy of R. pseudoacacia a 10 cm organic and humus horizont (O/A) has developed. Ó 2009 Ecological Society of China. Published by Elsevier B.V.
1. Introduction In the majority of terrains degraded by open-cast mining in southern Poland and other areas of Europe Robinia pseudoacacia is applied to perform land reclamation. It belongs to the family of Fabaceae and it is commonly known as the black locust. This is the species of small ecological requirements and therefore it quickly adapts in areas characterised by extreme environmental conditions for example: without soil cover. Considering it, the species has habitat-forming character and therefore it is often planted at poor and loose sand to fix it and enrich it in biogens. R. pseudoacacia is an alien species in Poland and it has invasive character. Its seeds were brought to Europe at the beginning of the 17th century and it has been widely planted since that period [1]. Black locust has been planted in Poland since the mid-18th century and now it is present all over the country, although it is no frequent as in some other parts of Europe [2]. R. pseudoacacia can propagate in a generative and vegetative way, therefore it is widespread species within the zone of temperate and subtemperate climates [3]. It is used at formation of shelterbelts, as decorative element and at land reclamation of degraded terrains [4]. It often creates dense stands, which through shadowing larger and larger areas reduces * Tel.: +48 0323689306. E-mail address: [email protected]
the neighbouring vegetation. In the tree stand, where R. pseudoacacia predominates, the undergrowth is very poor or absent. R. pseudoacacia, similarly to other arborescent species, differently influences the initiation of soil forming process and its further development, especially through influence of phytogenic field [5–9]. Specific species influence of R. pseudoacacia is conditioned by the chemical composition of its plant litter and the richness in nutrients. Plants, producing different secondary metabolites, release them into the soil through secretion systems of living tissues and after decomposition of their debris enrich it. Some of these substances are the only source of nutrients for plants. Decomposing leaves and other parts of R. pseudoacacia enrich poor sands in organic colloids and nutrients every year. Especially important is nitrogen, which essentially influences the rate and development of ecosystem processes. The nutrient availability in forest ecosystems depends on the effective biogeochemical cycle within biogeocenosis. Through this cycle nutrients return to the soil in the form of plant litter and they create an organic level. In the result of decomposition and mineralization nutrients are released and then they are uptaken by plants again. The rate of humification and mineralization of organic matter depends on: temperature, humidity conditions, physical and chemical properties of plant material delivered to the soil, as well as on the richness of organisms which are responsible for decomposition of the organic matter [10–14]. The rate of
1872-2032/$ - see front matter Ó 2009 Ecological Society of China. Published by Elsevier B.V. doi:10.1016/j.chnaes.2009.08.006
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decomposition of plant litter and the rate of nutrients releasing essentially influence the heterogeneity of habitat and the further differentiation of ecosystems. Branches and leaves within the canopy are the main ‘‘tank” of nutrients retaining them in the place [15]. Therefore, investigation on chemical composition of plant litter (leaves, branches, bark and others) and its influence on the fertility of soil and their functioning in different ecosystems were performed many times [9,10,16– 21]. The aim of this study is (1) the attempt to present the influence of R. pseudoacacia on the rate of development of vegetationsoil cover in reclaimed sandy areas, and (2) the determination of chemical composition of the litter of R. pseudoacacia and the role of this species in potential enrichment of sandy habitat in nutrients and its further modification. 2. Materials and methods Research were performed in the eastern part of the Silesian Upland (S Poland) in the area of reclaimed sand excavation (50200 18, 800 N and 19280 57, 800 E). Main species used for this aim was R. pseudoacacia, which actually creates here one-species plantation and is of essential importance in the further shaping of ecological systems. The age of this plantation is estimated to be about 20 years. Within the plantation intentionally isolated singular clumps of this species were founded to determine the influence of single individual on the development of vegetation-soil cover. Under the canopy of R. pseudoacacia scrupulous plant mapping on the scale of 1:100 was made (Fig. 1A). Areas beyond the canopy were not mapped, they were mostly covered with nitrophylous species. Plant litter of R. pseudoacacia such as: bark, fine branches, fine roots, green leaves, fallen leaves which did not undergo the mineralization yet, and accumulated under their canopy was once collected in order to determine chemical composition of plant litter
Padus seroptina
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and its role in the enrichment of sandy substratum with nutrients. Green leaves were sampled directly from the plant in September, whereas fallen leaves were collected in the period of the autumn maximum of vegetation litter. The content of the following elements: C, N, Ca, Mg, K, Na, P, Fe, Al, Zn and Si, Mn, Mo, Co, Cd, Pb and Sr were determined in the samples taken. The total content of elements in plant material was determined after mineralization ‘‘in wet conditions” in the mixture of HNO3 + HF + H2O2 in closed system (in microwave apparatus MLS-1200MEGA240 of Milestone firm). The determination of particular elements was carried out by means of absorption method of atom spectrometry, excluding Na and K (method of emission flame spectrometry), C (method of Alten) and N (method of Kjeldahl). Plant materials for laboratory analyses were prepared according to direction by MacNaeidhe [22], Markert [23], Clément [24] and Ostrowska et al. [25]. Soil analysis: transect method – on transect lined under canopy of black locust at 1 m intervals along the whole length of the transect the thickness of the organic horizon (O) and the humus horizon (A) under the canopy of R. pseudoacacia was measured and soil samples from the humus layer were taken for chemical analysis. Moreover, the following analyses were made according to standards used in Poland: loss ignition – in the temperature of 550 °C, pH-reaction by means of potentiometric method with applying of glass electrode (in H2O and 1-mole KCl), organic carbon (Corg) in organic horizons by means of Alten’s method and in mineral horizons by means of Tiurin’s method, total nitrogen (Nt) by means of Kjeldahl’s method, available phosphorus (Pavailab) by Egner–Riehm’s method, hydrolytic acidity (Hh) by Kappen’s method, exchangeable aluminium (Al3+) and exchangeable hydrogen (H+) by means of Sokolow’s method, the total content of P, Mg, Na, K after samples extraction by 1-mole CH3COONH4 of pH 7; the measurement by means of apparatus ASA (firm Solar): Ca and Mg – in absorption version, whereas Na and K – in emission version.
Of - horizon
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Fig. 1. The investigation transect in the zone of influence Robinia pseudoacacia: (A) scheme of plant distribution under canopy; (B) differentiation of organic horizons (O with subhorizons Ol and Of) and humus (A) horizon. The number of points (1– 14) in transect corresponding with numbers of Figs. 2–4.
R. pseudoacacia, covering the investigation area, creates biogroups composed of three trunks, which are 11 m high. The biogroup has two-layer vertical structure: top and undergrowth. In the first case most of all R. pseudoacacia occurs, whereas in the second one – Padus serotina. The oldest individuals of R. pseudoacacia are accompanied by young generation of this species. The oldest specimen from among of all individuals studied is about 20 years old. Singular small individuals of Betula pendula, Caragana arborescens and Crataegus monogyna are met within the clump, but they are not of large biocenotic importance at this stage. In the shadow made by canopy zone the occurrence of seedlings and mature individuals of P. serotina has mass character. Whereas under the canopy of R. pseudacacia, the development of the following generations of this species both on vegetative and generative way is observed. Calamagrostis epigejos – a tall grass, representing herbaceous plants within the canopy zone – occurred in the form of small patches (Fig. 1A). Large patches of C. epigejos occur when R. pseudoacacia is only 2 m high, i.e. at the initial stage. These were observed in the neighbourhood of the clump investigated. Actually, the singular clumps of this species also occur at the edge of plantation. Apart from the influence of the canopy zone, the following singular species: Poa compressa, Holcus mollis, Euphorbia esula, Epipactis atrorubens, Festuca ovina and Linaria vulgaris were noted on isolated localities. Under R. pseudoacacia its dead parts such as:
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branches, leaves, bark occurred at the majority of plots studied. They hindered the access of other plant seeds to the soil bank of seeds. 3.2. Soil morphology The soil forming processes under the canopy of R. pseudoacacia presents the differentiation in relation to morphology on: organic (O) and humus (A) horizons. Organic and humus horizons of the largest thickness occur in the central part of the canopy, on contrary to the edge or the zone beyond the canopy (Fig. 1B). Organic horizon (O) is divided into subhorizons Ol, Of and rarely – Oh. Subhorizon Ol – is made by undecomposed litter (branches, leaves and other) of R. pseudoacacia, as well as by leaves and acorns of Quercus rubra occurring about 50 m from species investigated. Chemical indices which characterize this subhorizon have the following values: ignition losses – 36%, content of Corg – 20%, nitrogen Nt – 1%, ratio C/N – 26, Ptot. – 629 mg/kg, Pavailab.– 51 mg/kg, Mg – 230 mg/kg and pH – 4.8 in water and 4.5 in KCl. Subhorizon Of – is made by partially decomposed above-mentioned litter, debris is still recognised, it is overgrown with mycelium, there are also insect excrements. Chemical indices in this subhorizon have slightly other values: ignition losses – 86%, content of Corg – 42%, nitrogen Nt – 2.47%, ratio C/N – 17 Ptot. – 961 mg/kg, Pavailab.– 164 mg/kg, Mg – 335 mg/kg and pH – 5.4 in water and 4.5 in KCl. Subhorizon Oh – very thin, is composed of already not recognised plant remains with humus lens settled by fine roots, this substratum is dark brown, it is mellow and humid. Horizon A – medium- and fine-grained sand, loose, of aeolian origin, dark grey (10Y/R). Initial soils creating under this species are characterised by profile structure of Ol–Of–Oh–A–A/C–C type. Name of soil according to Systematics of Soil of Poland [26]: lithogenic soils, mineral without carbonates initial and weakly developed, loose initial soils (regosols), according to FAO [27]: Haplic Arenosols, WRB [28]: Protic Arenosols. Chemical properties of humus horizons under canopy of R. pseudoacacia The soil forming under the canopy of R. pseudacacia is characterised by acid and weakly acid pH-reaction, which fluctuates within the range 4.6–5.2 in water and 4.2–4.8 in KCl. Hydrolythic and exchangeable acidity (H+, Al3+) indicates a certain similarity in some areas of canopy and beyond canopy zones (Fig. 2). Losses ignition and contents of organic carbon, nitrogen along the transect is differentiated. The largest values of them were stated in the point No 5. Ratio C/N is in general narrow along the whole transect (Fig. 3) and it betokens the rapid process of mineralization and biological activity of the soil. Contents of available forms of P, Mg, K, Na (Fig. 4) for plants in humus horizon are low and the lowest amount among them is typical for phosphorus. The highest values of elements investigated and were most often stated near trunks and in central part of the canopy zone (Figs. 2–4). 3.3. Chemical composition of plant litter of R. pseudoacacia Results of analysis in relation to chemical composition of macroelements (C, N, P, Mg, K, Ca, Na) and microelements (Mn, Mo, Co, Fe, Al, Zn, Si, Cd, Sr) of black locust’s selected parts (green leaves, leaf litter, bark, branches and roots) are presented in Table 1. The plant litter reaction (pH) varies from acid (bark and fine twigs – 3.6) to weakly acid (green leaves and litter – 5.3). It must be emphasized, that nitrogen occurs in similar quantities in particular samples and it varies from 1.01 to 2.65%. The greatest accumulation of elements has been observed in the following parts: green leaves (Ca > K > Mg > P > Si > Na > Fe >
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Zn > Al > Mn), leaf litter (Ca > K > Mg > Si > Fe > P > Na > Al > Zn > Mn). Similar regularities are observed in the remaining litter of R. pseudoacacia. The particular contents of elements investigated in plant material assume the shape of the following series: green leaves: Ca > K > Mg > P > Si > Na > Fe > Zn > Al > Mn > Sr > Pb > Mo > Co > Cd leaf litter: Ca > K > Mg > Si > Fe > P > Na > Al > Zn > Mn > Pb > Sr > Mo > Co > Cd bark: Ca > Fe > Si > Al > K > Mg > Na > P > Zn > Pb > Sr > Mn > Mo > Co > Cd branches: Ca > Fe > K > Si > Na > Al > Mg > Zn > P > Pb > Sr > Mn > Mo > Co > Cd roots: Si > Ca > K > Al > Fe > Na > Mg > P > Zn > Mg > Pb > Sr > Mo > Co > Cd Among elements investigated almost everywhere the first place in the series is occupied by Ca, whereas the last positions are typical for Mo, Co and Cd. High contents of Ca are of essential importance in the development of vegetation in sandy areas through partial deacidification and regulation of soil pHreaction.
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Fig. 3. Some chemical properties of humus horizon (A) under canopy of Robinia pseudoacacia.
4. Discussion Black locust is a deciduous tree of variable form ranging from small suckering clumps to tall individuals growing up to 8–24 m in height and 0.3–0.8 m in diameter. The short trunk usually divides not far above the ground forming multiple-stem crown. Black locust is a legume plant and has the ability to fix nitrogen from the air with the aid of nitrogen fixing bacteria on its roots. As a result of this ability, it grows readily in poor infertile soils. R. pseudoacacia can also act as a natural supplier of nitrogen to other plants in the whole landscape [3]. It grows very fast when young and, as a result, even in young black locust woods the nitrogen content of
soil can be considerably higher than in woods of other species at the same age [29]. Symbiotic nitrogen-fixation and the fast growth of black locust contributed to the increase in soil NH4–N. Differences in nitrogen availability and light conditions appeared to cause the strong divergence in the development of different types of young woods [30]. In the undergrowth of the tree stands, where R. pseudoacacia predominates, herbaceous plants rarely occur [4]. In the case of sandy areas, the essential role is also played by shading and elimination of photophilous species. The occurrence of psammophilous species exclusively at the edge of the canopy in sun-heated places is evident. This causes the floristic poorness in brushwood with contribution of this species, especially under the canopy. Under the R. pseudoacacia most of all nitrophilous species occur. In sandy areas there are most often not similar species, and the occurrence of Calamagrostis epigejos under the canopy of R. pseudoacacia is not accidental and is here of important significance in the process of biomass accumulation [14]. This species together with other nitrophilous species and also with R. pseudoacacia creates plant communities of synanthropic-ruderal character at wastelands and along railway tracks [31]. The group of species creating communities together with R. pseudacacia consists mostly of species adapted for substratum with very high content of nitrogen. They are as follows: Acer negundo, Sambucus nigra, Padus serotina, Tanacetum vulgare, Chelidonium majus, Urtica dioica, Humulus lupulus (if the terrain is slightly humid), Rubus fruticosus, Rubus idaeus, Arctium tomentosum, A. lappa, A. minus, Calamagrostis epigejos, Solidago canadensis, S. virga-aurea [4], and sporadically Lupinus polyphyllus. It can even create brushwood with Reynoutria japonica and R. sachalinensis. Pines can sow under the canopy of R. pseudoacacia, but they extinct very quickly. Such specific species composition can be caused by high content of nitrogen in upper soil horizons. The lack of vegetation under the canopy has also the connection with potential allelopathic abilities of R. pseudoacacia. Researches performed by Nasiri [32] proved, that the lack of vegetation, especially herbaceous one, under the canopy of R. pseudoacacia is associated with alleopathic activity of the substance releasing during its litter decomposition. These authors proved – by means of chromatographic method – the occurrence of alleopathic substances such as: robinetin, myricetin and quercetin in leaves and other parts of this species. The phenomenon of allelopathy plays the essential role at this species invasion on larger and larger areas. The second reason of floristic poorness in sandy areas can be the lack of plant species properly adapted to such surfaces. Under the canopy of black locust in very short time as for the pedogenesis, the formation of humus and organic horizons (O), dividing into subhorizons (Ol–Of–Oh), creating raw humus (above ground litter) are observed. The above ground litter is the only source of nutrients in forming communities at poor loose sands. The basic biogens, which were released during the above ground litter mineralization are taken by plants and that way they continue the biological cycle. Therefore the intensity of plant remains mineralization influences the amount of potential nutrients available for plants. Bogatyrev [33] considers the formation of organic horizon in ecosystems for one of the most important biogeocenotic processes. Humus and organic horizons in sandy areas play very essential role in functioning of poor ecosystems [9]. Well-developed horizons are observed near trunks and they should be considered as the oldest within the canopy. Such rapid development undoubtedly has connection with ecology and biology of species and its different chemical composition. The formation of soil mosaic in short period of time was observed by other authors in sandy areas of primary succession [8,34], as well as in forest communities of climax character [5–7,35,36]. The soil developing under the canopy of R. pseudoacacia is characterised by spatial variety (even on small scales) and it reveals the dependence on
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O. Rahmonov / Acta Ecologica Sinica 29 (2009) 237–243 40
[mg/kg]
Mg
30
20
10
0 25
1
2
3
4
5
6
7
8
9
10
11
12
13
14 110
[mg/kg]
K
20
90
15
70
5
50
0
1
2
3
4
5
6
7
25 [mg/kg]
8
9
10
11
12
13
14
30
7
Na
[mg/kg]
1
2
Pt
3
4
5
6
8
7
[mg/kg]
9
10
11
12
13
14
10
11
12
13
14
Pavailable
5
3
20
1 0 15
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
4
5
6
8
7
9
14
Fig. 4. The contents of available forms of Mg, K, Na, P and total Ptot. of humus horizon (A) under canopy of Robinia pseudoacacia.
Table 1 The chemical composition of plant litter of Robinia pseuodacacia. Samples
C
N
C/N
P
Si
Mn
Mg
Na
K
Ca
Mo
Co
Fe
Al
Zn
Cd
Pb
Sr
pH
n=6 % Green leaves Leaf litter Bark Branches Root
53 56 59.2 57.4 46.4
(mg/kg) 2.65 2.13 1.84 1.01 2.19
20 26 32 56 21
948 708 236 76 512
668 1686 1980 638 8242
110 44 30 16 98
1618 2270 462 338 798
464 592 408 460 846
6554 3312 810 640 3972
the distance from the trunk. The variety in soil properties is the reflection of size and architecture of the canopy of predominating species in the clump and undergrowth. Plants, uptaking elements from the soil and delivering organic remains instead, significantly influence the content of different elements. The majority of researches proved that specific influence of species on the ecosystem results just from chemical composition of different fractions of its litter, especially from leaves [37,38]. The content of nutrients in leaves is commonly known as the effect of food status in plants [39,40]. The leaves contain the majority of nutrients circulated in forest and brushwood ecosystems [41,42]. Both endogenous and exogenous factors cause the temporal and spatial changes in nutrient content in leaves [43–45]. Spatial variety can be primarily caused by the variety of the very soil [46,47], terrain topography, vertical and horizontal structure of
19116 25574 13478 9398 5976
10 16 22 12 4
2 4 0.2 4 2
258 942 2276 932 2786
141 478 1814 360 3104
200 180 96 116 278
0.0 0.2 0 0 1.4
12 42 84 68 68
22.2 31.6 37.4 39.6 35.2
H2O
KCl
5.4 5.3 4.0 4.0 4.8
5.2 5.1 3.7 3.7 4.5
phytocenoses and human impact [9]. The litter of R. pseudoacacia is relatively rich in nutrients in relation to some tree species [48] and it weakly removes nutrients from dead remains before its falling. Thus they enrich the soil after decomposition. For the element return, the most important components of litter were leaves. It is because together with this fraction more than a half of biogens is delivered. It mostly results from their predominating contribution in the litter. In the case of nitrogen the important role is played by leaves and roots, where it is accumulated in the largest amount. Nitrogen accelerates the process of succession in this area although it is considered to be deficit element, especially in poor sands. Enrichment of soil nitrogen by black locust may therefore favour the appearance of specific combinations of associated species even in young woodland, and induce considerable local divergence in the composition of secondary wood communities compared with
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those under non-symbiotic tree species [49]. As suggested the authors [49], the indirect effect of black locust on the species composition of the field layer is likely to be strongest on poor sandy soil where nitrogen is the main limiting soil resource. 5. Conclusion R. pseudoacacia plays positive role in the process of sand fixing and soil formation in areas undergoing land reclamation by means this species. Sandy areas reclaimed by R. pseudoacacia are fixed enough and they are not threatened by wind erosion. Annual production of leaves and their rapid decomposition makes the main source of organic matter causing the formation of raw humus and after mineralization it delivers macro- and microelements into poor sandy ecosystems. It is important moment during the development process of initial soils. Relatively rapid processes of soil formation were observed under the canopy in the neighbourhood of trunks of R. pseudoacacia. This species has the ability to fix free atmospheric nitrogen as the additional source of soil enrichment. Results from performed researches indicate that its role in regeneration of poor ecosystems is mostly connected with the formation of forest. However, the species negatively influences the biological diversity. The flora is most often very poor in areas where this species occurs. Therefore, before land reclamation we should answer the question: do we want plantation with R. pseudoacacia or ecosystem which is typical for sandy areas? If we choose the second option, then these areas should be kept to regeneration in a way of natural succession. Acknowledgements The author gratefully acknowledge Kamil and Małgorzata Rahmonovs for help with field works. The author thank an anonymous reviewer for their critical and constructive comments. I also thank Prof. Alicji MacBarc for her kind help in improving the language of this paper. References [1] H. Ellenberg, Vegetation Ecology of Central Europe, Cambridge University Press, Cambridge, UK, 1988. pp. 1–753. [2] C. Pacyniak, Locust tree (Robinia pseudoacacia L.) in conditions of Polish forest environment, Roczniki Akademii Rolniczej w Poznaniu 111 (1981) 1–85. [3] H.S. Moon, S.Y. Jung, S.C. Hong, Rate of soil respiration at black locust (Robinia pseudoacacia) stands in Jinju area, Korean Journal of Ecology 24 (2001) 371– 376. [4] W. Oles´, O. Rahmonov, M. Rzetala, I. Malik, S. Pytel, The ways of industrial wastelands management in the landscape of Silesian Region, Ekológia (Bratislava) 23 (1) (2004) 244–251. [5] P.J. Zinke, The pattern of influence of individual forest trees on soil properties, Ecology 43 (1962) 130–133. [6] D. Binkley, The influence of tree species on forest soils: processes and patterns, in: Proceedings of the Tree and Soil Workshop 1994, Agronomy Society of New Zealand Special Publications, New Zealand, Lincoln University Press, 1996, vol. 10, pp. 7–33. [7] R. Bednarek, H. Dziadowiec, U. Pokojska, Pedological aspect of variability, Ecological Questions 1 (2002) 35–41. [8] O. Rahmonov, M. Rzetala, I. Malik, W. Oles´, S. Pytel, Possibilities of applying Salix acutifolia in revitalizing areas transformed by anthropogenic activity, Ekológia (Bratislava) 23 (2004) 280–290. [9] O. Rahmonov, Relations Between Vegetation and Soil in Initial Phase of Succession in Sandy Areas (in Polish), University of Silesia Press, Katowice, 2007. pp. 1–200. [10] H. Dziadowiec, Decomposition of litters in selected forest ecosystems (mineralization, nutrient release, humification) (in Polish), Rozprawy, Torun´, 1990, pp. 1–137. [11] H. Dziadowiec, A. Kwiatkowska, Mineralization and humification of plant fail in mixed forest stand of the reserve ‘‘Las Piwnicki” near Torun´, Ekologia Polska 28 (1) (1980) 111–128. [12] J.M. Facelli, S.T.A. Pickett, Plant litter: its dynamics and effect on plant community structure, Botanical Review 57 (1) (1991) 1–33. [13] M.-M. Coûteaux, P. Bottner, B. Berg, Litter decomposition, climate and litter quality, Tree 10 (2) (1995) 63–66.
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