Effects of afforestation on carbon storage in Boyang Lake Basin, China

By using field survey data from the sixth forest inventory of Jiangxi Province in 2003, the biomass and carbon storage for three studied species （Pinus massoniana, Cunninghamia lanceolata, and Pinus elliottii） were estimated in Taihe and Xingguo counties of Boyang Lake Basin, Jiangxi Province, China. The relationship between carbon density and forest age was analyzed by logistic equations. Spatio-temporal dynamics of forest biomass and carbon storage in 1985-2003 were also described. The results show that total stand area of the three forest species was 3.10 × 10^5 ha, total biomass 22.20 Tg, vegetation carbon storage 13.07 Tg C, and average carbon density 42.36 Mg C/ha in the study area in 2003. Carbon storage by forest type in descending order was： P. massoniana, C. lanceolata and P. elliottii. Carbon storage by forest age group in descending order was： middle stand, young stand, near-mature stand and mature stand. Carbon storage by plantation forests was 1.89 times higher than that by natural forests. Carbon density of the three species increased 8.58 Mg C/ha during the study period. The carbon density of Taihe County was higher in the east and west, and lower in the middle. The carbon density of Xingguo County was higher in the northeast and lower in the middle. In general, the carbon density increased with altitude and gradient. Afforestation projects contribute significantly to increasing stand area and carbon storage. Appropriate forest management may improve the carbon sequestration capacity of forest ecosystems.     

1990-2050年间贵州省东南部森林植被碳蓄积及固碳潜力分析

本文以贵州省东南部三州为研究区,运用连续生物量转换因子法和平均生物量法,通过2010年森林清查小班数据,建立了24类优势树种的森林植被碳密度与林龄之间的关系。同时,估算了1990-2010年间贵州省东南部森林植被生物量及其碳蓄积量,分析了碳蓄积量的时空变化特征,并预测出2050年该区域森林植被的固碳潜力。结果显示：（1）2010年贵州省东南部森林植被碳蓄积量为106.22 TgC,占贵州省森林植被碳蓄积量的63.01%,占全国森林植被碳蓄积量的1.36%;平均碳密度32.44 MgC/hm²,是贵州省森林植被平均碳密度的93%,全国森林植被平均碳密度的76%,碳密度空间分布呈现由西部向东部增加趋势且东部高于平均水平。（2）1990-2000年间森林植被碳蓄积量增加了30.67 TgC;2000-2010年间森林植被碳蓄积量增加了49.55 TgC,其中,退耕还林导致森林植被碳蓄积量增加了31.09 TgC。（3）以2010年为基准年,假设40 a后贵州省东南部森林面积保持稳定,且不考虑轮伐期的未来情景下,至2050年该区域森林植被碳蓄积量将达到153.38 TgC,其增量可达47.16 TgC,表明贵州省东南部森林具有较大的碳增汇潜力。     

Labile and stabile soil organic carbon fractions in surface horizons of mountain soils–relationships with vegetation and altitude

Global and local climate changes could disturb carbon sequestration and carbon stocks in forest soils. Thus, it is important to characterize the stability of soil organic matter and the dynamics of soil organic carbon (SOC) fractions in forest ecosystems. This study had two aims: (1) to evaluate the effects of altitude and vegetation on the content of labile and stabile forms of organic carbon in the mountain soils; and (2) to assess the impact of the properties of soil organic matter on the SOC pools under changing environmental conditions. The studies were conducted in the Karkonosze Mountains (SW Poland, Central Europe). The content of the most labile fraction of carbon (dissolved organic carbon, DOC) decreases with altitude, but the content of fulvic acids (FA), clearly increases in the zone above 1000 m asl, while the stabile fraction (humins, non-hydrolyzing carbon) significantly decreases. A higher contribution of stabile forms was found in soils under coniferous forests (Norway spruce), while a smaller - under deciduous forests (European beech) and on grasslands. The expected climate change and the ongoing land use transformations in the zone above 1000 m asl may lead to a substantial increase in the stable humus fraction (mainly of a non-hydrolyzing carbon) and an increase in the SOC pools, even if humus acids are characterized by a lower maturity and greater mobility favorable to soil podzolization. In the lower zone (below 1000 m asl), a decrease in the most stable humus forms can be expected, accompanied by an increase of DOC contribution, which will result in a reduction in SOC pools. Overall, the expected prevailing (spatial) effect is a decreasing contribution of the most stable humus fractions, which will be associated with a reduction in the SOC pools in medium-high mountains of temperate zone of Central Europe.     

Carbon dynamics in woody biomass of forest ecosystem in China with forest management practices under future climate change and rising CO2 concentration

It is critical to study how different forest management practices affect forest carbon sequestration under global climate change regime. Previous researches focused on the stand-level forest carbon sequestration with rare investigation of forest carbon stocks influ- enced by forest management practices and climate change at regional scale. In this study, a general integrative approach was used to simulate spatial and temporal variations of woody biomass and harvested biomass of forest in China during the 21st century under dif- ferent scenarios of climate and CO2 concentration changes and management tasks by coupling Integrated Terrestrial Ecosystem Carbon budget （InTEC） model with Global Forest Model （G4M）. The results showed that forest management practices have more predominant effects on forest stem stocking biomass than climate and CO2 concentration change. Meanwhile, the concurrent future changes in cli- mate and CO2 concentration will enhance the amounts of stem stocking biomass in forests of China by 12%-23% during 2001-2100 relative to that with climate change only. The task for maximizing stem stocking biomass will dramatically enhance the stem stocking biomass from 2001~100, while the task for maximum average increment will result in an increment of stem stocking biomass before 2050 then decline. The difference of woody biomass responding to forest management tasks was owing to the current age structure of forests in China. Meanwhile, the sensitivity of long-term woody biomass to management practices for different forest types （coniferous forest, mixed forest and deciduous forest） under changing climate and CO2 concentration was also analyzed. In addition, longer rotation length under future climate change and rising CO2 concentration scenario will dramatically increase the woody biomass of China during 2001~100. Therefore, our estimation indicated that taking the role of forest management in the carbon cycle into the consideration at regional or national level is very important to project the forest carbon sequestration under future climate change and rising atmospheric CO2 concentration.     

Soil organic carbon pool along different altitudinal level in the Sygera Mountains,Tibetan Plateau

Labile organic carbon (LOC) is one of the most important indicators of soil organic matter quality and dynamics elevation and plays important function in the Tibetan Plateau climate. However, it is unknown what the sources and causes of LOC contamination are. In this study, soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and LOC were analyzed based on different soil horizons and elevations using turnover time in an experimental site (3700 m to 4300 m area) in Sygera. SOC and LOC in higher-elevation vegetation types were higher than that of in lower-elevation vegetation types. Our results presented that the soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN) were positively correlated with SOC. The content of easily oxidized carbon (EOC), particulate organic carbon (POC) and light fraction organic carbon (LFOC) decreased with depth increasing and the content were the lowest in the 60 cm to 100 cm depth. The total SOC, ROC and POC contents decreased with increasing soil horizons. The SOC, TN, MBC and MBN contents increased with increasing altitude in the Sygera Mountains. The MBC and MBN contents were different with the changes of SOC (p<0.05), meanwhile, both LFOC and POC were related to total SOC (p<0.05). The physical and chemical properties of soil, including temperature, humidity, and altitude, were involved in the regulation of SOC, TN, MBC, MBN and LFOC contents in the Sygera Mountains, Tibetan Plateau.     

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.     

Contrasting changes in above- and below-ground biomass allocation across treeline ecotones in southeast Tibet

Under conditions of a warmer climate, the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems. However, the above- and below-ground live biomass allocations among different vegetation types within the treeline ecotones are not well investigated. To determine the altitudinal patterns of above-/below-ground carbon allocation, we measured the root biomass and estimated the above-ground biomass (AGB) in a subalpine forest, treeline forest, alpine shrub, and alpine grassland along two elevational transects towards the alpine tundra in southeast Tibet. The AGB strongly declined with increasing elevation, which was associated with a decrease in the leaf area index and a consequent reduction in carbon gain. The fine root biomass (FRB) increased significantly more in the alpine shrub and grassland than in the treeline forest, whereas the coarse root biomass changed little with increasing altitudes, which led to a stable below-ground biomass (BGB) value across altitudes. Warm and infertile soil conditions might explain the large amount of FRB in alpine shrub and grassland. Consequently, the root to shoot biomass ratio increased sharply with altitude, which suggested a remarkable shift of biomass allocation to root systems near the alpine tundra. Our findings demonstrate contrasting changes in AGB and BGB allocations across treeline ecotones, which should be considered when estimating carbon dynamics with shifting treelines.     

Effects of land-use types on soil organic carbon stocks: a case study across an altitudinal gradient within a farm-pastoral area on the eastern Qinghai-Tibetan Plateau,China

A crucial region for China's ‘Grain-forGreen Policy' is located within a traditional farmpastoral area, between 2000 to 3000 m above sea level, on the eastern Qinghai-Tibetan Plateau.However, the responses of soil organic carbon(SOC) to different land-use patterns in this region are unclear. Here, we determined the SOC(0–20 cm) content of grasslands and forests that are being converted from farmlands, as well as in abandoned arable land and arable land in this region. The factors influencing the reclaimed lands were analyzed along altitudes from 2030 to 3132 m. Our results showed that SOC content was higher for grassland and abandoned arable land than forest and arable land. The SOC content increased with the increase in altitude for total land-use patterns. Further, the grassland and abandoned arable land had higher SOC content than the forest with almost parallel trends along the increase in altitude. However, the proportion of regulated factors of altitude and species richness varied among forest, grassland, and abandoned arable land. Our results indicated that the land-use pattern of returning farmland to grassland and abandoned arable land was more effective in terms of the SOC storage in the superficial layer in this altitude range in the Qinghai-Tibetan Plateau, thereby being beneficial to optimizing land management in this region.     

城市绿量的遥感估算与热岛效应的相关分析——以北京市五环区域为例

 本研究以遥感分析北京城市绿地对地表温度的影响,研究包括绿地提取、绿量估算、地表温度反演,地表温度和绿量相关分析。并以高精度Rapid Eye遥感影像,提取了五环内的绿地面积(197.3km²,占城区总面积的29.6%),且估算绿量总值为2450.7km²。同时用2009年7月20日的Landsat5 TM 6波段数据进行地表温度反演,低温区、中温区、次热岛和热岛区域所占的五环内城区面积的比例分别为12.3%,34.7%,40.4%和12.6%。绿量和地表温度呈负相关关系:y=-1278.7x+60650,城市绿地可以使城区平均温度降低2.6℃。     

Land cover change in different altitudes of Guizhou-Guangxi karst mountain area,China: patterns and drivers

Topography, especially altitude, will influence the way, process and characteristics of land cover changes in mountainous area, simultaneously, the vertical difference of land cover changes will affect soil quality and regional ecological environment. Therefore, the gradient relationship analysis between land cover changes and altitude is very important for regional sustainability. This study investigated land cover dynamics based on land cover data from a typical mountainous area in the Guizhou-Guangxi karst mountain area, China, in 2000 and 2010, then explored the relationship between altitude and land cover change and analyzed different drivers of land cover change at different altitudes. Our findings are as follows. 1) From 2000 to 2010, the total area of land cover transition was 7167.04 km~2 or 2.8% of the region. The increasing area of build-up land(926.23 km~2) was larger than that of forest(859.38 km~2), suggesting that the urban construction speed was higher than that of reforestation. 2) Intensity of land cover transition in northwestern Guizhou-Guangxi karst mountain area was much larger than that of southeast part and their transition trend was also significantly different, which was consistent with regional population and economy. 3) Human activity was the most dramatic at altitudes between 0–500 m. For 500–1000 m, grassland mainly converted to forest and build-up land. Area of land cover transition was the greatest between 1000–1500 m, while above 1500 m, the transition of grassland was the most obvious. 4) The drivers of land cover change varied. Land cover change was positively correlated with gross domestic product and population density but was inversely related to relief amplitude. There were correlations between land cover change and distance to roads and rivers, and their correlations varied with altitude. By revealing patterns and causes of land cover changes in different altitudes, we hope to understand the vertical dependence of land cover changes, so as to improve land productivity and protect land ecological environment scientifically.     

Re-assessing Vegetation Carbon Storage and Emissions from Land Use Change in China Using Surface Area

Land surface area estimation can provide basic information for accurately estimating vegetation carbon storage under complex terrain. This study selected China, a country dominated by mountains, as an example, and calculated terrestrial vegetation carbon storage(VCS) for 2000 and 2015 using land surface area and traditional ellipsoid area. The land surface area is estimated by a triangular network on the high precision digital elevation model.The results showed that: 1) The VCS estimated by the surface area measurement in 2000 and 2015 were 0.676 and0.692 Pg C(1 Pg = 10~(15) g) higher than the VCS calculated using the ellipsoid area, respectively. 2) As the elevation increases, the differences between VCS estimated by surface area measurement and ellipsoid area measurement are expanding. Specially, a clear gap was present starting from an elevation of 500 m, with the relative error exceeds8.99%. 3) The total amount of carbon emitted due to land use change reached 0.114 Pg C. The conversions of forestland and grassland to other land use type are the main reasons of the loss of vegetation carbon storage, resulting in a total amount of biomass carbon storage decreased by 0.942 and 0.111 Pg C, respectively. This study was a preliminary exploration of incorporating land surface area as a factor in resource estimation, which can help more accurately understand the status of resources and the environment in the region.     

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.     

基于自组织映射法的时间序列土地利用变化的时空可视化

精细尺度下多时间序列土地利用时空演变分析是当前研究的一个趋势,本研究基于2005、2007、2009、2011、2013年5期土地利用数据采用自组织映射方法分析了北京市乡镇级多时间序列土地利用的时空演变规律,实现了乡镇尺度下多时间序列土地利用数据的时空一体化表达和对比分析。通过构建自组织映射神经网络,利用其聚类和降维可视化功能对5个监测时期的土地利用数据同时进行训练,在其输出面板可以发现不同土地利用类型的分布聚集模式以及相互之间的结构比例关系,并对输出神经元进行二次聚类以及土地利用变化轨迹分析,展示出北京市乡镇级5个监测时相的土地利用时空演变规律。结果揭示出北京市平原区、山区及二者过渡的山前结合带的各自不同的土地利用时空变化轨迹与模式：北京市平原区向高建设用地比例的土地利用结构方向演变,山区向高林地比例的土地利用结构方向演变,而山前结合带的土地利用时空演变较为复杂。     

Carbon storage of the forest and its spatial pattern in Tibet,China

The raising concentration of atmospheric CO_2 resulted in global warming. The forest ecosystem in Tibet played an irreplaceable role in maintaining global carbon balance and mitigating climate change for its abundant original forest resources with powerful action of carbon sink. In the present study, the samples of soil and vegetation were collected at a total of 137 sites from 2001 to 2018 in Tibet. Based on the field survey of Tibet's forest resources and 8~(th) forest inventory data, we estimated the carbon storage and carbon density of forest vegetation(tree layer, shrub, grass, litter and dead wood) and soil(0-50 cm) in Tibet. Geostatistical methods combined with Kriging spatial interpolation and Moran's I were applied to reveal their spatial distribution patterns and variation characteristics. The carbon density of forest vegetation and soil in Tibet were 74.57 t ha~(-1) and 96.24 t ha~(-1), respectively. The carbon storage of forest vegetation and soil in Tibet were 344.35 Tg C and 440.53 Tg C, respectively. Carbon density of fir(Abies forest) was 144.80 t ha~(-1) with the highest value among all the forest types. Carbon storage of spruce(Picea forest) was the highest with 99.09 Tg C compared with other forest types. The carbon density of fir forest and spruce forest both increased with the rising temperature and precipitation. Temperature was the main influential factor. The spatial distribution of carbon density of forest vegetation, soil, and ecosystem in Tibet generally showed declining trends from western Tibet to eastern Tibet. Our results facilitated the understanding of the carbon sequestration role of forest ecosystem in the Tibet. It also implied that as the carbon storage potential of Tibet's forests are expected to increase, these forests are likely to serve as huge carbon sinks in the current era of global warming and climate change.     

Mapping deciduous broad-leaved forested swamps using ALOS/Palsar data

Accurate, updated information on the distribution of wetlands is essential for estimating net fluxes of greenhouse gases and for effectively protecting and managing wetlands. Because of their complex community structure and rich surface vegetation, deciduous broad-leaved forested swamps are considered to be one of the most difficult types of wetland to classify. In this research, with the support of remote sensing and geographic information system, multi-temporal radar images L-Palsar were used initially to extract the forest hydrological layer and phenology phase change layer as two variables through image analysis. Second, based on the environmental characteristics of forested swamps, three decision tree classifiers derived from the two variables were constructed to explore effective methods to identify deciduous broad-leaved forested swamps. Third, this study focused on analyzing the classification process between flat-forests, which are the most severely disturbed elements, and forested swamps. Finally, the application of the decision tree model will be discussed. The results showed that: 1) L-HH band(a L band with wavelength of 0–235 m in HH polarization mode; HH means Synthetic Aperture Radars transmit pulses in horizontal polarization and receive in horizontal polarization) in the leaf-off season is shown to be capable of detecting hydrologic conditions beneath the forest; 2) the accuracy of the classification(forested swamp and forest plat) was 81.5% based on hydrologic features, and 83.5% was achieved by combining hydrologic features and phenology response features, which indicated that hydrological characteristics under the forest played a key role. The HHOJ(refers to the band created by the subtraction with HH band in October and HH band in July) achieved by multi-temporal radar images did improve the classification accuracy, but not significantly, and more leaf-off radar images may be more efficient than multi-seasonal radar images for inland forested swamp mapping; 3) the lower separability between forested swamps dominated by vegetated surfaces and forest plat covered with litter was the main cause of the uncertainty in classification, which led to misleading interpretations of the pixel-based classification. Finally, through the analysis with kappa coefficients, it was shown that the value of the intersection point was an ideal choice for the variable.     

A STUDY ON THE FLORISTIC PLANT GEOGRAPHY OF XISHA ISLANDS, SOUTH CHINA

邢福武，李泽贤，叶华谷，陈炳辉，吴德邻ＡＳＴＵＤＹＯＮＴＨＥＦＬＯＲＩＳＴＩＣＰＬＡＮＴＧＥＯＧＲＡＰＨＹＯＦＸＩＳＨＡＩＳＬＡＮＤＳ，ＳＯＵＴＨＣＨＩＮＡ￥ＸｉｎｇＦｕｗｕ；ＬｉＺｅｘｉａｎ；ＹｅＨｕａｇｕ；ＣｈｅｎＢｉｎｇｈｕｉ；ＷｕＤｅｌｉｎ（...     

SPATIAL AND TEMPORAL DYNAMICS OF SOIL ORGANIC CARBON IN RESERVED DESERTIFICATION AREA——A Case Study in Yulin City, Shaanxi Province, China

1INTRODUCTIONDesertification is one of the most serious land degrada-tion, which results in the deterioration of physical, che-mical, and biological characteristics of soils (UNEP, 1992). Soil organic carbon (SOC) was considered to be a key index in evaluation of soil quality, soil degradation and soil C sequestration(SCHLENGSINGER etal., 1990; FENG etal., 2002; WANG etal., 2003). Many researchers have reported the correlations among desertification restoration, soil C s…     

Biomass carbon storage and its sequestration potential of afforestation under natural forest protection program in China

Based on the data from China′s Seventh Forest Inventory for the period of 2004–2008, area and stand volume of different types and age-classes of plantation were used to establish the relationship between biomass density and age of planted forests in different regions of the country. Combined with the plantation area in the first-stage of the Natural Forest Protection(NFP) program(1998–2010), this study calculated the biomass carbon storage of the afforestation in the first-stage of the program. On this basis, the carbon sequestration potential of these forests was estimated for the second stage of the program(2011–2020). Biomass carbon storage of plantation established in the first stage of the program was 33.67 Tg C, which was majority accounted by protection forests(30.26 Tg C). There was a significant difference among carbon storage in different regions, which depended on the relationship of biomass carbon density, forest age and plantation area. Under the natural growth, the carbon storage was forecasted to increase annually from 2011 to 2020, reaching 96.03 Tg C at the end of the second-stage of the program in 2020. The annual growth of the carbon storage was forecasted to be 6.24 Tg C/yr, which suggested that NFP program has a significant potential for enhancing carbon sequestration in plantation forests under its domain.     

Rebirth after death: forest succession dynamics in response to climate change on Gongga Mountain,Southwest China

Global climate change is having long-term impacts on the geographic distribution of forest species. However, the response of vertical belts of mountain forests to climate change is still little known. The vertical distribution of forest vegetation(vertical vegetation belt) on Gongga Mountain in Southwest China has been monitored for 30 years. The forest alternation of the vertical vegetation belt under different climate conditions was simulated by using a mathematical model GFSM(the Gongga Forest Succession Model). Three possible Intergovernmental Panel on Climate Change(IPCC) climate scenarios(increase of air temperature and precipitation by 1.8℃/5%, 2.8℃/10% and 3.4℃/15% for B_1, A_1B and A_2 scenarios, respectively) were chosen to reflect lower, medium and higher changes of global climate. The vertical belts of mountainous vegetation will shift upward by approximately 300 m, 500 m and 600 m in the B_1, A_1B and A_2 scenarios, respectively, according to the simulated results. Thus, the alpine tree-line will move to a higher altitude. The simulation also demonstrated that, in a changing climate, the shift in the vegetation community will be a slow and extended process characterized by two main phases. During the initial phase, trees of the forest community degrade or die, owing to an inability to adapt to a warmer climate. This results in modest environment for the introduction of opportunistic species, consequently, the vegetation with new dominant tree species becomes predominant in the space vacated by the dead trees at the expense of previously dominated original trees as the succession succeed and climate change advance. Hence, the global climate change would dramatically change forest communities and tree species in mountainous regions because that the new forest community can grow only through the death of the original tree. Results indicated that climate change will cause the change of distribution and composition of forest communities on Gongga Mountain, and this change may enhance as the intensity of climate change increases. As a result, the alternation of death and rebirth would finally result in intensive landscape changes, and may strongly affect the eco-environment of mountainous regions.     

Ecological status and uses of juniper species in the cold desert environment of the Lahaul valley, North-western Himalaya, India

The juniper species Juniperus polycarpos C. Koch, J. indica Bertol. and J. communis L. var. saxatilis (Pallas) are important elements of the forest vegetation in Lahaul valley in the north-western Himalaya. Their ability to grow under the barren and xeric conditions of cold deserts makes them particularly suited for afforestation programmes under these ecological conditions. In the Lahaul valley, juniper species are used as subsistence resources and for religious purposes. Excessive removal of juniper wood and leaves by the local population, overgrazing, habitat fragmentation and low regeneration potential are the main obstacles to conservation of juniper forests in this region. The present study was carried out to assess density, basal area and importance value index (IVI) of the local vegetation as well as uses and amounts of juniper wood and leaves removed from the local forests. Pressure on relict juniper forests due to grazing animals and intensive removal of wood and leaves by the local population was found to be greater at an altitude above 3,000 m. The results of the study demonstrated that the different juniper species were adapted to specific altitude ranges. A higher species density was recorded at lower altitude except for J. indica which was only present at high altitude (>3,200 m) on south-facing slopes. Density, basal area and IVI of J. polycarpos were higher at Hinsa (2,700 m) than at Jahlma (3,000 m). The rapid loss of vegetation due to overuse and habitat degradation has made the conservation of juniper forests an important priority in the Lahaul valley. J. polycarpos at lower altitude and J. indica at higher altitude are ecologically the more suitable species for the successful implementation of conservation programmes. The support of rehabilitation programmes by regional authorities is essential for the reestablishment of the local juniper forests.