ECOLOGICAL SERIES OF SOIL ANIMALS IN DARLIDAI MOUNTAIN

The ecological series of soil animals under the broad-leaved and pine mixed forest in Darlidai Mountainwas studied. Seven sample plots were selected according to different altitude gradients, which belong to different vegeta-tion types. By investigating and analyzing soil animals in every sample plot it is found that there are 45 groups and 1956individuals, which axe involved in 3 phylums, 7 classes, 16 orders, respectively. The altitude is a key factor which af-fects ecological series of soil animals. Both the groups and individuals of soil animals increase with altitude increasingunder certain conditions, which contrastes with ordinary cases, resulting from special micro-climate in studied area. Thegroups and individuls of soil animals are the most under the broad-leaved and pine forest on the top of the mountain, andthe least under Picea-Abies forest in the foot of the mountain.     

Effects of experimental warming on soil microbial communities in two contrasting subalpine forest ecosystems,eastern Tibetan Plateau,China

Soil microbial communities are primarily regulated by environmental temperature. Our study investigated the effects of global warming on soil microbial community composition as measured via phospholipid fatty acid (PLFA) analysis and soil chemical characteristics in relation to soil depth in a dragon spruce plantation and a spruce-fir-dominated natural forestin the Eastern Tibetan Plateau. Open-top chambers were utilized to increase the soil and air temperature. Soil samples were collected from the 0-10 cm, 10-20 cm, and 20-30 cm layers after a 4-year warming. Our results showed that the soil microbial community and the contents of TC (Total carbon), TN (Total nitrogen), NO ₃ ^- , and NH ₄ ⁺ responded differently to warming in the two contrasting forests, especially at the 0-10 cm soil depth. Warming increased soil microbial biomass at the 0-20 cm depth of soil in natural forest but reduced it at the 0-10 cm depth ofsoil in the plantation. In contrast, the TC and TN contents were reduced in most soil layers of a natural forest but increased in all of the soil layers of the plantation under warming conditions. This result suggested that the effects of warming on soil microbial community and soil C and N pools would differ according to soil depth and forest types; thus, the two contrasting forests would under go differing changes following the future climate warming in this region.     

Quantitative simulation on soil moisture contents of two typical vegetation communities in Sanjiang Plain,China

Different types of vegetation occupy different geomorphology and water gradient environments in the San-jiang Plain,indicating that the soil moisture dynamics and water balance patterns of the different vegetation communi-ties might differ from each other.In this paper,a lowland system,perpendicular to the Nongjiang River in the Honghe National Nature Reserve(HNNR),was selected as the study area.The area was occupied by the non-wetland plant forest and the typical wetland plant meadow.The Microsoft Windows-based finite element analysis software package for simulating water,heat,and solute transport in variably saturated porous media(HYDRUS),which can quantita-tively simulate water,heat,and/or solute movement in variably-saturated porous media,was used to simulate soil moisture dynamics in the root zone(20-40 cm) of those two plant communities during the growing season in 2005.The simulation results for soil moisture were in a good agreement with measured data,with the coefficient of determi-nation(R2) of 0.44-0.69 and root mean square error(RMSE) ranging between 0.0291 cm3/cm3 and 0.0457 cm3/cm3,and index of agreement(d) being from 0.612 to 0.968.During the study period,the volumetric soil moisture content of meadow increased with the depth and its coefficient of variation decreased with the depth(from 20 cm to 40 cm),while under the forest the soil moisture content at different depths varied irregularly.The calculated result of water budget showed that the water budget deficit of the meadow was higher than that of the forest,suggesting that the meadow is more likely to suffer from water stress than the forest.The quantitative simulation by HYDRUS in this study did not take surface runoff and plant growth processes into account.Improved root water uptake and surface runoff models will be needed for higher accuracy in further researches.     

Soil organic carbon pools in particle-size fractions as affected by slope gradient and land use change in hilly regions, western Iran

This study was conducted to explore the effects of topography and land use changes on particulate organic carbon(POC),particulate total nitrogen(PTN),organic carbon(OC) and total nitrogen(TN) associated with different size primary particle fractions in hilly regions of western Iran.Three popular land uses in the selected site including natural forest(NF),disturbed forest(DF) and cultivated land(CL) and three slope gradients(0-10 %,S1,10-30 %,S2,and 30-50%,S3) were employed as the basis of soil sampling.A total of 99 soil samples were taken from the 0-10 cm surface layer in the whole studied hilly region studied.The results showed that the POC in the forest land use in all slope gradients was considerably more than the deforested and cultivated lands and the highest value was observed at NF-S1 treatment with 9.13%.The values of PTN were significantly higher in the forest land use and in the down slopes(0.5%) than in the deforested and cultivated counterparts and steep slopes(0.09%) except for the CL land use.The C:N ratios in POC fraction were around 17-18 in the forest land and around 23 in the cultivated land.In forest land,the silt-associated OC was highest among the primary particles.The enrichment factor of SOC,EC,was the highest for POC.For the primary particles,EC of both primary fractions of silt and clay showed following trend for selected land uses and slope gradients:CL> DF> NF and S3 > S2> S1.Slope gradient of landscape significantly affected the OC and TN contents associated with the silt and clay particles,whereas higher OC and TN contents were observed in lower positions and the lowest value was measured in the steep slopes.Overall,the results showed that native forest land improves soil organic carbon storage and can reduce the carbon emission and soil erosion especially in the mountainous regions with high rainfall in west of Iran.     

Micromorphology and quality attributes of the loess derived soils affected by land use change: A case study in Ghapan watershed, Northern Iran

In order to study the effects of different land vegetative covers on soil quality attributes, a loess hill slope was selected in eastern Golestan Province, Ghapan watershed, Iran. Four profiles in four land uses, including Quercus natural forest; Pinus artificial forest; Cupressus artificial forest and a cultivated land, were studied. Results showed that MWD was significantly different in the studied land uses, and it varied between 1.6 mm in Quercus natural forest and o.31 mm in cultivated land use. The lowest CEC, microbial respiration rate and organic carbon were 28.4 cmol·kg^1, 177 μgCO2·g^-1·day^-1 and 1.32 % found in cultivated land use, respectively. The organic matter was considerably higher content in the forest areas than that of cultivated land use. The studies on soil profile development revealed that the natural forest soils were highly developed. The soils of the Quercus natural forest were classified as Calcic Haploxeralfs with a well developed argillie horizon unlike the cultivated soils which showed the minimum development and classified as Typic Xerorthents. The soils of the artificial forests had both mollic epipedons and were classified as Typic Calcixerolls with moderate profile development. Micromorphological studies revealed that argillic horizons had speckled and partly crystallitic b-fabric in the natural forest indicating the high landscape stability. In contrast, the crystallitic b-fabric of other land uses shows the absence of enough leaching of carbonate and the subsequent migration of clay particles indicating the unstable conditions and high soil erosion. Intense erosion of the surface horizons of cultivated land use has resulted in the outcropping of the subsurface carbonate rich horizons preventing soil development.     

Regional variation in carbon sequestration potential of forest ecosystems in China

Enhancing forest carbon(C) storage is recognized as one of the most economic and green approaches to offsetting anthropogenic CO_2 emissions. However, experimental evidence for C sequestration potential(C_(sp)) in China's forest ecosystems and its spatial patterns remain unclear, although a deep understanding is essential for policy-makers making decisions on reforestation. Here, we surveyed the literature from 2004 to 2014 to obtain C density data on forest ecosystems in China and used mature forests as a reference to explore C_(sp). The results showed that the C densities of vegetation and soil(0–100 cm) in China's forest ecosystems were about 69.23 Mg C/ha and 116.52 Mg C/ha, respectively. In mature forests, the C_(sp) of vegetation and soil are expected to increase to 129.26 Mg C/ha(87.1%) and 154.39 Mg C/ha(32.4%) in the coming decades, respectively. Moreover, the potential increase of C storage in vegetation(10.81 Pg C) is estimated at approximately twice that of soil(5.01 Pg C). Higher C_(sp) may occur in the subtropical humid regions and policy-makers should pay particular attention to the development of new reforestation strategies for these areas. In addition to soil nutrients and environment, climate was an important factor influencing the spatial patterns of C density in forest ecosystems in China. Interestingly, climate influenced the spatial patterns of vegetation and soil C density via different routes, having a positive effect on vegetation C density and a negative effect on soil C density. This estimation of the potential for increasing forest C storage provided new insights into the vital roles of China's forest ecosystems in future C sequestration. More importantly, our findings emphasize that climate constraints on forest C sequestration should be considered in reforestation strategies in China because the effects of climate were the opposite for spatial patterns of C density in vegetation and soil.Enhancing forest carbon(C) storage is recognized as one of the most economic and green approaches to offsetting anthropogenic CO2 emissions. However, experimental evidence for C sequestration potential(Csp) in China's forest ecosystems and its spatial patterns remain unclear, although a deep understanding is essential for policy-makers making decisions on reforestation. Here, we surveyed the literature from 2004 to 2014 to obtain C density data on forest ecosystems in China and used mature forests as a reference to explore Csp. The results showed that the C densities of vegetation and soil(0–100 cm) in China's forest ecosystems were about 69.23 Mg C/ha and 116.52 Mg C/ha, respectively. In mature forests, the Csp of vegetation and soil are expected to increase to 129.26 Mg C/ha(87.1%) and 154.39 Mg C/ha(32.4%) in the coming decades, respectively. Moreover, the potential increase of C storage in vegetation(10.81 Pg C) is estimated at approximately twice that of soil(5.01 Pg C). Higher Csp may occur in the subtropical humid regions and policy-makers should pay particular attention to the development of new reforestation strategies for these areas. In addition to soil nutrients and environment, climate was an important factor influencing the spatial patterns of C density in forest ecosystems in China. Interestingly, climate influenced the spatial patterns of vegetation and soil C density via different routes, having a positive effect on vegetation C density and a negative effect on soil C density. This estimation of the potential for increasing forest C storage provided new insights into the vital roles of China's forest ecosystems in future C sequestration. More importantly, our findings emphasize that climate constraints on forest C sequestration should be considered in reforestation strategies in China because the effects of climate were the opposite for spatial patterns of C density in vegetation and soil.     

Soil carbon stock and flux in plantation forest and grassland ecosystems in Loess Plateau,China

Carbon sequestration occurs when cultivated soils are re-vegetated. In the hilly area of the Loess Plateau, China, black locust(Robinia pseudoacacia) plantation forest and grassland were the two main vegetation types used to mitigate soil and water loss after cultivation abandonment. The purpose of this study was to compare the soil carbon stock and flux of these two types of vegetation which restored for 25 years. The experiment was conducted in Yangjuangou catchment in Yan′an City, Shaanxi Province, China. Two adjacent slopes were chosen for this study. Six sample sites were spaced every 35–45 m from summit to toe slope along the hill slope, and each sample site contained three sampling plots. Soil organic carbon and related physicochemical properties in the surface soil layer(0–10 cm and 10–20 cm) were measured based on soil sampling and laboratory analysis, and the soil carbon dioxide(CO2) emissions and environmental factors were measured in the same sample sites simultaneously. Results indicated that in general, a higher soil carbon stock was found in the black locust plantation forest than that in grassland throughout the hill slope. Meanwhile, significant differences in the soil carbon stock were observed between these two vegetation types in the upper slope at soil depth 0–10 cm and lower slope at soil depth 10–20 cm. The average daily values of the soil CO2 emissions were 1.27 μmol/(m2·s) and 1.39 μmol/(m2·s) for forest and grassland, respectively. The soil carbon flux in forest covered areas was higher in spring and less variation was detected between different seasons, while the highest carbon flux was found in grassland in summer, which was about three times higher than that in autumn and spring. From the carbon sequestration point of view, black locust plantation forest on hill slopes might be better than grassland because of a higher soil carbon stock and lower carbon flux.     

Age-related changes of carbon accumulation and allocation in plants and soil of black locust forest on Loess Plateau in Ansai County,Shaanxi Province of China

The effects of reforestation on carbon(C) sequestration in China′s Loess Plateau ecosystem have attracted much research attention in recent years. Black locust trees(Robinia pseudoacacia L.) are valued for their important use in reforestation and water and soil conservation efforts. This forest type is widespread across the Loess Plateau, and must be an essential component of any planning for C sequestration efforts in this fragile ecological region. The long-term effects of stand age on C accumulation and allocation after reforestation remains uncertain. We examined an age-sequence of black locust forest(5, 9, 20, 30, 38, and 56 yr since planting) on the Loess Plateau to evaluate C accumulation and allocation in plants(trees, shrubs, herbages, and leaf litter) and soil(0–100 cm). Allometric equations were developed for estimating the biomass of tree components(leaf, branch, stem without bark, bark and root) with a destructive sampling method. Our results demonstrated that black locust forest ecosystem accumulated C constantly, from 31.42 Mg C/ ha(1 Mg = 10~6 g) at 5 yr to 79.44 Mg C/ha at 38 yr. At the ′old forest′ stage(38 to 56 yr), the amount of C in plant biomass significantly decreased(from 45.32 to 34.52 Mg C/ha) due to the high mortality of trees. However, old forest was able to accumulate C continuously in soil(from 33.66 to 41.00 Mg C/ha). The C in shrub biomass increased with stand age, while the C stock in the herbage layer and leaf litter was age-independent. Reforestation resulted in C re-allocation in the forest soil. The topsoil(0–20 cm) C stock increased constantly with stand age. However, C storage in sub-top soil, in the 20–30, 30–50, 50–100, and 20–100 cm layers, was age-independent. These results suggest that succession, as a temporal factor, plays a key role in C accumulation and re-allocation in black locust forests and also in regional C dynamics in vegetation.     

Effects of aluminum toxicity induced by acid deposition on pine forest ecosystem in Longli of Guizhou Province,Southwestern China

The effects of acid deposition on pine forest ecosystems in Longli of Guizhou Province, southwestern China are studied using indoor experiments and model simulations. Indoor experiments are designed to explore the aluminum toxicity on pine seedlings, and the long-term soil acidification model（LTSAM） and a terrestrial biogeochemistry model（CENTURY） are used to simulate the influences of acid deposition on pine forest ecosystems. The indoor experiment results of aluminum toxicity show that aluminum ions in solution limit plant growth and acid deposition enhances this effect by facilitating the release of aluminum ions from the soil. Pine seedling biomass and root elongation decrease as the aluminum concentration increases. The results of model simulations show that the soil chemistry varies significantly with different changes in acid deposition. When the acid deposition increases, the pH value in the soil solution decreases and the soil Al³⁺ concentration increases. The increased acid deposition also has negative impacts on the forest ecosystem, i.e., decreases plant biomass, net primary productivity（NPP） and net CO₂ uptake. As a result, the soil organic carbon（SOC） decreases because of the limited supply of decomposition material. Thus acid deposition need be reduced to help protect the forest ecosystems.     

Effects of temperature,soil moisture,soil type and their interactions on soil carbon mineralization in Zoigê alpine wetland,Qinghai-Tibet Plateau

Wetland stores substantial amount of carbon and may contribute greatly to global climate change debate. However, few researches have focused on the effects of global climate change on carbon mineralization in Zoigê al-pine wetland, Qinghai-Tibet Plateau, which is one of the most important peatlands in China. Through incubation ex-periment, this paper studied the effects of temperature, soil moisture, soil type (marsh soil and peat soil) and their in-teractions on CO2 and CH4 emission rates in Zoigê alpine wetland. Results show that when the temperature rises from 5℃ to 35℃, CO2 emission rates increase by 3.3-3.7 times and 2.4-2.6 times under non-inundation treatment, and by 2.2-2.3 times and 4.1-4.3 times under inundation treatment in marsh soil and peat soil, respectively. Compared with non-inundation treatment, CO2 emission rates decrease by 6%-44%, 20%-60% in marsh soil and peat soil, respec-tively, under inundation treatment. CO2 emission rate is significantly affected by the combined effects of the tempera-ture and soil type (p < 0.001), and soil moisture and soil type (p < 0.001), and CH4 emission rate was significantly af-fected by the interaction of the temperature and soil moisture (p < 0.001). Q10 values for CO2 emission rate are higher at the range of 5℃-25℃ than 25℃-35℃, indicating that carbon mineralization is more sensitive at low temperature in Zoigê alpine wetland.     

Effects of land cover on soil organic carbon stock in a karst landscape with discontinuous soil distribution

Land cover type is critical for soil organic carbon(SOC) stocks in territorial ecosystems. However, impacts of land cover on SOC stocks in a karst landscape are not fully understood due to discontinuous soil distribution. In this study, considering soil distribution, SOC content and density were investigated along positive successional stages(cropland, plantation, grassland, scrubland, secondary forest, and primary forest) to determine the effects of land cover type on SOC stocks in a subtropical karst area. The proportion of continuous soil on the ground surface under different land cover types ranged between 0.0% and 79.8%. As land cover types changed across the positive successional stages, SOC content in both the 0–20 cm and 20–50 cm soil layers increased significantly. SOC density(SOCD) within 0–100 cm soil depth ranged from 1.45 to 8.72 kg m-2, and increased from secondary forest to primary forest, plantation, grassland, scrubland, and cropland, due to discontinuous soil distribution. Discontinuous soil distribution had a negative effect on SOC stocks, highlighting the necessity for accurate determination of soil distribution in karst areas. Generally, ecological restoration had positive impacts on SOC accumulation in karst areas, but this is a slow process. In the short term, the conversion of croplandto grassland was found to be the most efficient way for SOC sequestration.     

Dynamics and relationships of Ca, Mg, Fe in litter, soil fauna and soil in Pinus koraiensis-broadleaf mixed forest

The Liangshui Natural Reserve in Heilongjiang Province of China was selected as the study area. The authors collected the samples of forest litter （Tilia amurensis, Fraxinus mandshurica, Pinus koraiensis, Acer mono, Betula costata, and mixed litter）, soil in humus horizon （0--5cm） and soil horizon （5-20cm）, and soil macrofauna （Oligochaeta, Geophiloporpha and Juliformia） from 2001 to 2002. The role of soil macrofauna in the material cycle was analyzed through comparing the macro-element contents among various parts of the subsystems and using enrichment index （El）. The results indicate that dynamic changes of various litters are very complicated. The contents of Fe in each kind of litter increase firstly, and then decrease in the study period. The changes of macro-element contents are greater in the broad-leaf litter than in the coniferous litter, and the mixed litter is in the middle level, but the differences among them are not significant. The contents of Mg and Fe in humus are higher than those in soil, but the contents of Ca in soil are higher than that in humus. The dynamic changes of macro-element contents in soil and soil fauna are not consistent with those in litter. The diplopod presented obvious enrichment of Ca and Mg （E1〉1）, but it does not significantly enrich Fe. Earthworm has a stronger enrichment ability of Fe than diplopod and scolopendra, but E1〈1. Soil fauna can make great influences on the material cycle of the subsystems.     

Structure and regeneration dynamics of three forest types at different succession stages of spruce – fir mixed forest in Changbai Mountain,northeastern China

Analyzing and understanding the structure and growth dynamics of forests at different stages is helpful to promote forest succession, restoration and management. Three spots representing three succession stages of spruce-fir mixed forest(SF: polar-birch secondary forest, MF: spruce-fir mixed forest and PF: spruce-fir near primary forest) were established. Structure, growth dynamics during two growth seasons for dominant tree species, regeneration were examined, and a univariate O-ring function statistic was used to analyze the spatial patterns of main regeneration tree species. Results showed that,(1) composition of tree species, periodic annual increment(PAI) of the diameter at breast height(DBH), basal area for overstory trees and of ground diameter(DGH) for saplings, were significantly different with the succession;(2) the current species composition and regeneration dynamics of SF suggested a development towards spruce-fir mixed forests. Pioneer species like Betula platyphyllaa will gradually disappear while climax species, such as Abies nephrolepis, Pinus koraiensis, Picea koraiensis and Tilia amurensis will dominate forest stands;(3) Despite the highest volume occurring in PF, and saplings in it grew better than in the others, this forest type is unstable because of its unsustainable structure of DBH class and insufficient regeneration; and(4) MF had the most reasonable distribution of DBH class for adult trees(DBH 5.0 cm) and DGH class for saplings(H ≥30 cm and DBH ≤5 cm), as well as an optimal volume increment. Limiting canopy opening size can lessen the physiological stress and promote the growth and competitive status of regeneration. Management implications for increasing the gaps and thus creating better growth conditions for understory saplings and facilitating forest succession were discussed.     

Spatial and seasonal variation in soil respiration along a slope in a rubber plantation and a natural forest in Xishuangbanna,Southwest China

Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO₂ levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO₂ budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest (SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements. Research was conducted over one year in Xishuangbanna during May, June, July and October 2015 (wet season) and January and March 2016 (dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^-1 yr^-1 in natural forest and 11.7 and 5.7 Mg C ha^-1 yr^-1 in rubber plantation. Using a linear mixed effects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.     

The influence of environmental variables on distribution patterns of Irano-Turanian forests in Alborz Mountains,Iran

Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot (1000 m2) and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure J. excelsa. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA (Canonical Correspondence Analysis) results indicated that the altitude, precipitation, pH, EC, SP, clay and CaCO₃ are the most important factors determine the distribution of trees and shrub in central Alborz     

Effects of disturbance intensities on vegetation patterns in oak forests of Kumaun, west Himalaya

In order to realize the significance of oak forests for ecology and economy of the Himalayan region,the present study attempts to objectively characterize disturbance intensities and their impacts on compositional features of identified Oak forests, i.e.Banj-oak(Quercus leucotrichophora A.Camus), Tilonj-oak(Q.floribunda Lindley)and Kharsu-oak(Q. semecarpifolia J.E.Smith)in west Himalaya. Amongst studied forests,Q.leucotrichophora and Q. semecarpifolia forests exhibited high sensitivity towards disturbance intensities.In both forests, increasing level of disturbance significantly lowered tree density,dominance and natural recruitment (seedling and sapling density).Q.floribunda forests, however,appeared relatively more resilient to anthropogenic disturbances.Amongst studied oak forests,Q.semecarpifolia forests with overall poor natural regeneration are in a most critically endangered demographic state.However,a slightly improved regeneration(i.e.,seedling density)in moderately disturbed plots is indicative that such plots may be utilized most suitably for in situ revival of these forests.Effect of disturbance intensities on tree population is an important subject for forest ecology and management and the present study highlights a need for adopting different management strategies across disturbance intensities in diverse oak forests of west Himalaya.     

Quantitative division of succession and spatial patterns among different stand developmental stages in Changbai Mountains

Broadleaf-Korean pine forests exhibit high species richness and distinctive species composition, which are currently becoming more dominant among natural forests in Changbai Mountains of northeastern China. Understanding the ecological process of restored vegetation is quite important for ecosystem reconstruction. Distinguishing stand development stages and analyzing the dynamic spatial patterns could provide insights into significant community coexistence mechanisms. In the present study, eight permanent study areas were established according to the substituting space for time method in Changbai Mountains of north-eastern China. The optimal division method was used to quantify the successional series into different stand development stages, and the point pattern analysis method(L(r) function) was used to analyse the dynamic changes in spatial patterns and interspecific associations. Our results suggested that:(1) The stand development process was divided into five stages: the first three stages were poplar-birch secondary forests in different stages of recovery, the fourth stage was thespruce-fir mixed forest, and the last stage was the primary broadleaf-Korean pine forest;(2) The spatial pattern showed an aggregated distribution at a small scale and changed to a random distribution as the scale increased in poplar-birch secondary forests, but the spatial pattern appeared to be randomly distributed in spruce-fir mixed forest and broadleafKorean pine forest;(3) The interspecific associations between pioneer species and climax species changed from negative to positive among the different stand stages, and environmental resources were shared among these species. Interspecific differences in shade tolerance among the tree species were key determinants of forest dynamics and structure. Our study is vital to the understanding of the forest development; thus, the spatial change features should receive greater attention when forest management is being planned and restoration strategies are being developed for the Changbai Mountains.     

Effects of topographical and edaphic factors on the distribution of plant communities in two subtropical karst forests, southwestern China

Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwestern China.Surveys of two 1-ha permanent plots at each forest,and measurements of four topographic and thirteen edaphic factors on the slopes were performed.Twoway Indicator Species Analysis(TWINSPAN) and Detrended Canonical Correspondence Analysis(DCCA) were used for the classification of plant communities and for vegetation ordination with environmental variables.One hundred 10m×10m quadrats in each plot were classified into four plant community types.A clear altitudinal gradient suggested that elevation was important in community differentiation.The topography and soil explained 51.06% and 54.69% of the variability of the distribution of plant species in the two forest plots,respectively,indicating both topographic factors(eg.elevation,slope and rock-bareness rate) and edaphic factors(e.g.total P,K and exchangeable Ca) were the important drivers of the distribution of woody plant species in subtropical karst forest.However,our results suggested that topographical factors were more important than edaphic ones in affecting local plant distribution on steep slopes with extensive rock outcrops,while edaphic factors were more influential on gentle slope and relatively thick soil over rock in subtropical karst forest.Understanding relationships between vegetation and environmental factors in karst forest ecosystems would enable us to apply these findings in vegetation management strategies and restoration of forest communities.     

Composition,diversity and distribution of tree species in response to changing soil properties with increasing distance from water source – a case study of Gobind Sagar Reservoir in India

Construction of big dams on rivers develops artificial lakes or water reservoirs which conceive alterations in soil properties of the upstream catchment area. An undulating topography and freckly soil properties cause ups and downs in tree diversity, composition and distribution. The study aimed to evaluate the effect of Gobind Sagar reservoir on soil properties relative to the distance from it and assess its effect on tree diversity, evenness and their distribution in tropical and subtropical forests. Based on data analysis it was found that the soil moisture and organic carbon decreased along with increasing distance from the reservoir. It played a significant role in varying tree diversity. The sites distributed within0-2 km showed significantly higher α and β-diversity indices. Tree species richness and diversity indices showed a strong correlation(p 0.05) with soil moisture and organic carbon content. Simpson's and Mc Intosh evenness indices showed a strong negative correlation with soil bulk density. Indirect Detrended Correspondence Analysis(DCA) identified soil moisture and soil organic carbon as two major environmental gradients that influenced tree diversity and their distribution in five tropical and four subtropical forests in an upstream catchment of the reservoir. Mixed forests inhabited moist sites andAcacia-Pinus forests showed an inclination to dry areas. Canonical Correspondence Analysis(CCA)revealed that the tree species in tropical forests were mainly affected by driving forces such as soil moisture,organic carbon and bulk density whereas, in subtropical forest tree species were influenced by elevation, soil p H, EC and clay content.     

Crown fuel characteristics and carbon emission from Japanese red pine stands burned by crown fire in Mt. Palgong, South Korea

Carbon emissions from forest fires are considered an important factor of ecosystem carbon balance and global climate change. Carbon emissions from Japanese red pine stands (Pinus densiflora S. et Z.) burned by crown fire were estimated at Mt. Palgong in Daegu Metropolitan City, and crown fuel characteristics, including crown bulk density, crown base height, and fuel moisture content of Japanese red pine, were analyzed. Total biomass combusted was calculated by subtracting the biomass of burned stands from that of unburned stands exhibiting similar stand structures and site environments. Ten trees in the unburned area and five trees in the burned area were cut by using direct harvesting techniques to estimate crown layer biomass. All biomass sampled was oven-dried and weighed. The dry weight ratios of stems, branches, and needles were 70%, 21%, and 9%, respectively. The available fuel load susceptible to combustion during the crown fire spread was equivalent to 55% of the crown layer biomass. The crown bulk density was 0.24 kg/ m 3 on average. The estimated amount of CO 2 was 23,454 kg CO 2 /ha for the crown layer. These results will be useful for calculating the amount of CO 2 emitted from forest fires and for developing a forest carbon model in P. densiflora forests.