Hydraulic properties and drought response of a tropical bamboo (Cephalostachyum pergracile)

Bamboo plants are an essential component of tropical ecosystems,yet their vulnerability to climate extremes,such as drought,is poorly understood due to limited knowledge of their hydraulic properties.Cephalostachyum pergracile,a commonly used tropical bamboo species,exhibited a substantially higher mortality rate than other co-occurring bamboos during a severe drought event in 2019,but the underlying mechanisms remain unclear.This study investigated the leaf and stem hydraulic traits related to drought responses,including leaf-stem embolism resistance(P50leaf;P50stem) estimated using optical and X-ray microtomography methods,leaf pressure-volume and water-releasing curves.Additionally,we investigated the seasonal water potentials,native embolism level(PLC) and xylem water source using stable isotope.We found that C.pergracile exhibited strong resistance to embolism,showing low P50leaf,P50stem,and turgor loss point,despite its rapid leaf water loss.Interestingly,its leaves displayed greater resistance to embolism than its stem,suggesting a lack of effective hydraulic vulnerability segmentation(HVS) to protect the stem from excessive xylem tension.During the dry season,approximately 49% of the water was absorbed from the upper 20-cm-deep soil layer.Consequently,significant diurnal variation in leaf water potentials and an increase in midday PLC from 5.87±2.33% in the wet season to 12.87±4.09%in the dry season were observed.In summary,this study demonstrated that the rapid leaf water loss,high reliance on surface water,and a lack of effective HVS in C.pergracile accelerated water depletion and increased xylem embolism even in the typical dry season,which may explain its high mortality rate during extreme drought events in 2019.

Leaf thermal tolerance and sensitivity of temperate tree species are correlated with leaf physiological and functional drought resistance traits

Climate change is causing more frequent and severe climatic events,such as extreme heat and co-occurring drought,potentially accelerating tree mortality.Which tree species will cope better with those extreme events is still being researched.This study focuses on heat as a physiological stress factor and interspecifi c variation of thermal tolerance and sensitivity traits in 15 temperate coniferous and broad-leaved tree species.We investigate(1)whether thermal tolerance and sensitivity traits correlate with a droughtrelated physiological trait,particularly the leaf turgor loss point(πtlp,wilting point),and(2)how thermal tolerance and sensitivity traits co-vary within diff erent tree-functional types classifi ed by morphological and physiological traits of the leaf,i.e.,leaf mass per area(LMA)and percentage loss of area(PLA).The study was carried out in the Traunstein Forest Dynamics Plot of the ForestGEO network in Germany.The temperature response of the maximum quantum yield of photosystem II(F_(v)/F_(m))on leaf discs was determined,from which various physiological leaf traits were estimated,one of which is the breaking point temperature(T_(5)),the temperature at which F_(v)/F_(m)declines by 5%.Additionally,the temperature of 50%(T_(50))and 95%(T_(95))decline in F_(v)/F_(m)was evaluated.The decline width between T_(50)and T 5(DW T_(50)−T_(5))was taken as an indicator of the species’thermal sensitivity.The breaking point temperature ranged from 35.4±3.0 to 47.9±3.9℃among the investigated tree species and T 50 ranged between 46.1±0.4 and 53.6±0.7℃.A large interspecifi c variation of thermal tolerance and sensitivity was found.European ash(Fraxinus excelsior L.)was the most heat-sensitive species,while Wild cherry(Prunus avium L.)was the least heat-sensitive species.Species with a more negativeπtlp tended to have a higher breaking point temperature than species with a less negativeπtlp.A lower thermal sensitivity characterized species with a higher LMA,and high PLA was found in species with low thermal sensitivity.Accordingly,species with thicker and tougher leaves have lower thermal sensitivity which coincides with a lower wilting point.We conclude that species that develop drought-adapted foliage can cope better with heat stress.Further,they might be able to maintain transpirational cooling during combined heat and drought stress,which could lessen their mortality risk during climatic extremes.

Forest characteristics,population structure and growth trends of threatened relict Pseudotsuga forrestii in China

Pseudotsuga forrestii is a relict evergreen coniferous tree species in Pinaceae endemic to China.P.forrestii tree numbers have greatly decreased due to deforestation,over-utilization and habitat degradation.Here we clarify P.forrestii community types,structure,species diversity,seedling recruitments and growth trends.We identified four P.forrestii community types:(1)Pseudotsuga forrestii-Quercus guyavifolia-Acer davidii evergreen coniferous and broad-leaved mixed forest;(2)Pseudotsuga forrestii-Pinus yunnanensis-Quercus guyavifolia evergreen coniferous and broad-leaved mixed forest;(3)Pseudotsuga forrestii evergreen coniferous forest;(4)Pseudotsuga forrestii-Abies georgei var.smithii evergreen coniferous forest.P.forrestii forests are characterized by both warm temperate and temperate affinities.Simpson diversity,Pielou evenness,Shannon-Wiener diversity indices ranged from 0.75 to 0.76,0.74-0.81,and 1.62-1.93,respectively,with no significant differences among the four forest types.The forest stratification was multilayered.The canopy layer was generally 10-25 m tall,with the emergent layer reached 25-42 m.DBH and age structures of P.forrestii showed multimodal distributions.Its maximum age P.forrestii was 570 years with a DBH of 143 cm.The growth of annual ring width of P.forrestii was slow,and generally decreased with age,whereas the basal area at the breast height increased with age.Established seedlings/saplings were mainly found in unstable micro-habitats.Regeneration of P.forrestii depends on moderate natural disturbances.Finally,we provide recommendations for P.forrestii conservation.

雪被对川西高山植被坡向性分异的影响

在青藏高原东缘的松潘地区海拔4000m的高山地带设置5条宽1m、长40～70m的跨山脊南北样带,相邻样带间距为50m。按1m×1m面积划分为251个调查样方,于2004～2005年分别进行了地植物学调查、土壤理化性质分析和冬季雪被厚度监测。以物种的相对频度为群落指标,以雪被厚度、土壤厚度、有机质含量、土壤湿度(0.25mm及2mm)、全磷、全钾、铵态氮、水解性酸、pH及坡度等参数为环境指标,运用PC-ORD软件的TWINSPAN对植物群落进行分类、CCA进行排序。结果表明,由南坡向北坡可以划分为亚菊——金露梅高山灌丛草甸、细柄茅——苔草高山草甸、细柄茅、苔草——矮柳高山灌丛草甸群落和杜鹃高山灌丛群落等4种群落类型。由南坡向北坡草本植物盖度由75%下降为39%,灌木盖度由25%增加到54%,在山脊附近50m左右的局地范围内植被类型表现为明显的南北坡向分异格局。2005年冬季南坡平均雪厚度21cm,山脊处为26cm,北坡34cm,由南坡向北坡雪被厚度逐渐增加;雪被厚度与灌木盖度呈正相关(r=+0.40,p<0.01,n=248),与草本植物盖度呈负相关(r=-0.45,p<0.01,n=248)。ANOVA的分析结果显示,土层厚度、风干土含水量、土壤酸度、有机质含量和全磷含量的南北坡向分异明显,由南坡向北坡逐渐增加,与雪被平均厚度存在显著的相关关系,相关系数分别为0.267、0.286、0.199和-0.183(n=119,p<0.05);土壤全钾和铵态氮含量的坡向差异不明显,与雪被厚度的相关性也不显著,相关系数分别为-0.068和0.104(n=119,p>0.05)。显示土壤特征的坡向分异规律在某种程度上与雪被的梯度变化存在着共轭关系。群落CCA排序及排序轴与环境指标的相关性分析也表明,坡度、雪被厚度、有机质含量和土壤湿度是导致植物群落坡向分异的主要环境因子,土壤铵态氮和全钾含量对植被坡向分异的影响不明显。

策勒沙漠-绿洲过渡带土壤种子库的基本特征

通过室外萌发法对策勒沙漠-绿洲过渡带土壤种子库的研究发现:该区域土壤中活性种子从总储量上来看较为丰富,其中有12种植物,分属8科,但各植物种的种子数量分配极不均匀,仅有多枝柽柳的种子数量丰富,其它植物种的土壤种子储量相对匮乏,甚至严重匮乏;种子库的生活型组成以多年生草本占优(53.85%),一年生草本植物次之(30.77%);不同群落与地貌类型的种子库间保持着较高的相似性。

Perception and Attitudes of Local Communities Towards Wild Elephant-related Problems and Conservation in Xishuangbanna,Southwestern China

The problem of wild elephants, or human-elephant conflict (HEC), influences the daily life of local communities and hinders the conservation of wild elephants.The perception and attitudes of local communities who inhabited the frontiers between human activities and wild elephant movement are important to the mitigation of the HEC and conservation of wild elephants. To analyze the perception and attitudes of local communities, the Participatory Rural Appraisal (PRA) was used in the investigation of 423 interviewees from 22 villages in Xishuangbanna from July 2009 to February 2010. The results indicated that local communities had their views on the elephant-related problems. In field survey, we found that 66.5% of interviewees were willing to support, participate in, and assist in the conservation of wild elephants;33.5% of interviewees were opposed or indifferent to such conservation, because their livelihoods and even their lives were endangered by wild elephants. These views and attitudes were influenced by local communities′perception of HEC, education level, gender and self-interest. Therefore, it is necessary to analyze the diverse views among local communities and balance profits and costs in addressing HEC.

Influence of groundwater depth on species composition and community structure in the transition zone of Cele oasis

The paper analyzes the hypothesis that the distribution of dominant plant species and characteristics of plant communities are related to groundwater depth. The results showed that variations of groundwater depth impacted distributions and characteristics of dominant plant communities. However, besides groundwater depth, the community composition and species diversity were also influenced by physiognomy of the habitat. Based on the similarity coefficient, the differences between dominant plant communities were significant at different groundwater depths. Compared with other results relating to desert vegetation and groundwater depth, variations of community distribution were similar at the large spatial scale. However, in this extremely arid region, there were significant differences in community type and community succession when compared with other arid regions, especially in relationship to deep groundwater depth. With groundwater depth from deep to shallow, communities transformed with the sequence of Alhagi communities, Tamarix spp. communities, Populus communities, Phragmites communities, and Sophora communities. At groundwater depth of less than 6.0 m, the community type and composition changed, and the species diversity increased. Among these dominant species, Tamarix exhibited the biggest efficiency in resource utilization according to niche breadth, which means it possessed the best adaptability to environmental conditions at the oasis margins.

植被和气候对阿拉斯加和加拿大北部北极苔原地区多年冻土活动层厚度的影响(英文)

The active layer is the top layer of permafrost soils that thaws during the summer season due to increased ambient temperatures and solar radiation inputs. This layer is important because almost all biological activity takes place there during the summer. The depth of active layer thaw is influenced by climatic conditions. Vegetation has also been found to have a strong impact on active layer thaw, because it can intercept incoming radiation, thereby insulating the soil from ambient conditions. In order to look at the role of vegetation and climate on active layer thaw, we measured thaw depth and the Normalized Difference Vegetation Index (NDVI; a proxy for aboveground plant biomass) along a latitudinal temperature gradient in arctic Alaska and Canada. At each site several measurements of thaw and NDVIwere taken in areas with high amounts of vegetation and areas with little to no vegetation. Results show that the warmest regions, which had the greatest levels of NDVI, had relatively shallow thaw depths, and the coldest regions, which had the lowest levels of NDVI, also had relatively shallow thaw depths. The intermediate regions, which had moderate levels of NDVIand air temperature, had the greatest depth of thaw. These results indicate that temperature and vegetation interact to control the depth of the active layer across a range of arctic ecosystems. By developing a relationship to explain thaw depth through NDVIand temperature or latitude, the possibility exists to extrapolate thaw depth over large scales via remote sensing applications.

Measuring Tourist’s Water Footprint in a Mountain Destination of Northwest Yunnan, China

Monitoring and minimizing tourist’s water consumption is essential for the sustainable development of mountain destinations in the world. However, available data and a generally accepted protocol on such measurement are still limited. This study uses water footprint accounting to quantify tourist’s water demand in the Liming valley, a World Heritage site and a rapidly growing tourism destination in Northwest Yunnan, China. Both the water for direct and indirect use is taken into account based on the consumptive behavior of the tourists in the valley. Data were collected through guesthouse monitoring and a tourist survey in the 2005 tourist season. The results indicate that an average tourist leaves behind a footprint of 5.2 m3 on local water resources per day. Food production and waste dilution are the two most important water consumption factors. The results also show tourists consume more water than the local residents on per capita basis. This suggests more commitment is necessary to cope with this stress by individual tourists. Management implications to make water use more sustainable in mountain destinations are derived from this study.

Epiphytic orchids and their ecological niche under anthropogenic influence in central Himalayas,Nepal

The survival chance of epiphytic orchids today not only depends on the natural site conditions required by the orchids but also on anthropogenic changes in site conditions.This study answers two questions:(1) What is the ecological niche of the different epiphytic orchid species?(2) What are the ecological factors that threaten epiphytic orchid's population under anthropogenic disturbances? Our study area was the Kathmandu valley,Nepal,with its subtropical forest.We established 156 systematically selected sampling points in the Kathmandu area covering different types of ecosystems under human impacts such as densely populated area,agricultural land,mixed agricultural and settled area,old tree patches,and a natural forest in a national park.The ecological niche of the orchid species was analyzed with a principal component analysis(PCA).The correlations between the different site factors were statistically significant.Spearman's rank correlation matrices showed that the variables land-use intensities with altitude,and height with diameter in breast height(dbh) of host had the highest significant positive correlation coefficient(0.67 and 0.64 respectively).On the other hand,host bark p H and altitude as well as land use had a significantly strong negative correlation coefficient(-0.80 and-0.61,respectively).Different epiphytic orchid species interact differently with the given set ofenvironmental factors:for occurrence of Vanda cristata there is no single environmental factor of special influence,while for Rhynchostylis retusa high bark p H and high light availability are important.First two axis of the PCA explained more than 50% of the total variance.Most orchid species occupy a specific,narrow niche in this ecological space.The main causes of anthropogenic influence of orchid population in the Kathmandu Valley are loss of adequate host trees(species and size) and increasing air pollution,resulting in increasing host bark p H.

Effects of climate change on potential habitats of the cold temperate coniferous forest in Yunnan province, southwestern China

We built a classification tree(CT) model to estimate climatic factors controlling the cold temperate coniferous forest(CTCF) distributions in Yunnan province and to predict its potential habitats under the current and future climates, using seven climate change scenarios, projected over the years of 2070-2099. The accurate CT model on CTCFs showed that minimum temperature of coldest month(TMW) was the overwhelmingly potent factor among the six climate variables. The areas of TMW<-4.05 were suitable habitats of CTCF, and the areas of -1.35 < TMW were non-habitats, where temperate conifer and broad-leaved mixed forests(TCBLFs) were distribute in lower elevation, bordering on the CTCF. Dominant species of Abies, Picea, and Larix in the CTCFs, are more tolerant to winter coldness than Tsuga and broad-leaved trees including deciduous broad-leaved Acer and Betula, evergreen broadleaved Cyclobalanopsis and Lithocarpus in TCBLFs. Winter coldness may actually limit the cool-side distributions of TCBLFs in the areas between -1.35°C and -4.05°C, and the warm-side distributions of CTCFs may be controlled by competition to the species of TCBLFs. Under future climate scenarios, the vulnerable area, where current potential(suitable + marginal) habitats(80,749 km^2) shift to nonhabitats, was predicted to decrease to 55.91%(45,053 km^2) of the current area. Inferring from the current vegetation distribution pattern, TCBLFs will replace declining CTCFs. Vulnerable areas predicted by models are important in determining priority of ecosystem conservation.

Bird diversity and waterbird habitat preferences in relation to wetland restoration at Dianchi Lake, south-west China

Background:Restoration projects have been implemented worldwide to mitigate the adverse effects of the loss and degradation of wetland habitats.Much research has been carried out on the impacts on birds of wetland restoration and management projects in China. Studies have mainly investigated central or coastal wetlands,while inland wetlands in remote areas have been much less studied. We focused on examining the response of wild birds to wetland restoration in Dianchi Lake,south-west China. Methods: The line transect method was performed at 26 sampling plots.Three of these were in the city,and to acquire all wild bird data 23 plots were located every 2-8 km along the shore of Dianchi Lake, between December 2011 and November 2013.We collected all related bird records by searching the available literature, articles, newspapers and records of birdwatchers to compare species variation before and after implementation of wetland restoration.To measure the relationships between waterbird assemblages and habitat structures, we used canonical correspondence analysis (CCA) to pair the main matrix of bird assemblages with a second matrix of habitat variables. Results: We recorded 182 bird species belonging to 51 families and 17 orders. Of the species, 42 were new records for Kunming City and 20 were new records for Yunnan Province. Ten waterbird species were found to have disappeared from the shore of Dianchi Lake.CCA results indicated that waterbirds could be divided into four categories based on their habitat preference:synanthropic (wintering gulls), special habitat (shorebirds),semi-natural (wintering coots and ducks) and disturbance-tolerant (resident) species.Conclusions:Our study is the first to consider the entire wild bird community throughout the year and discuss the species variation before and after wetland restoration projects launched for Dianchi Lake.Distinct habitat requirements of different waterbird groups were detected in our study,suggesting different types of restoration and management should be implemented.

Nature Conservation versus Scenic Quality:A GIS Approach towards Optimized Tourist Tracks in a Protected Area of Northwest Yunnan,China

Development of appropriate tourism infrastructure is important for protected areas that allow public access for tourism use.This is meant to avoid or minimize unfavourable impacts on natural resources through guiding tourists for proper use.In this paper,a GIS-based method,the least-cost path(LCP) modelling,is explored for planning tourist tracks in a World Heritage site in Northwest Yunnan(China),where tourism is increasing rapidly while appropriate infrastructure is almost absent.The modelling process contains three steps:1) selection of evaluation criteria(physical,biological and landscape scenic) that are relevant to track decision; 2) translation of evluation criteria into spatially explicit cost surfaces with GIS,and 3) use of Dijkstra's algorithm to determine the least-cost tracks.Four tracks that link main entrances and scenic spots of the study area are proposed after optimizing all evaluation criteria.These tracks feature lowenvironmental impacts and high landscape qualities,which represent a reasonable solution to balance tourist use and nature conservation in the study area.In addtion,the study proves that the LCP modelling can not only offer a structured framwork for track planning but also allow for different stakeholders to participate in the planning process.It therefore enhances the effectivenss of tourism planning and managemnt in protected areas.

Importance of overstorey attributes for understorey litter production and nutrient cycling in European forests

Background:In contrast with the negligible contribution of the forest understorey to the total aboveground phytobiomass of a forest,its share in annual litter production and nutrient cycling may be more important.Whether and how this functional role of the understorey differs across forest types and depends upon overstorey characteristics remains to be investigated.Methods:We sampled 209 plots of the FunDivEUROPE Exploratory Platform,a network of study plots covering local gradients of tree diversity spread over six contrasting forest types in Europe.To estimate the relative contribution of the understorey to carbon and nutrient cycling,we sampled non-lignified aboveground understorey biomass and overstorey leaf litterfall in all plots.Understorey samples were analysed for C,N and P concentrations,overstorey leaf litterfall for C and N concentrations.We additionally quantified a set of overstorey attributes,including species richness,proportion of evergreen species,light availability(representing crown density)and litter quality,and investigated whether they drive the understorey’s contribution to carbon and nutrient cycling.Results and conclusions:Overstorey litter production and nutrient stocks in litterfall clearly exceeded the contribution of the understorey for all forest types,and the share of the understorey was higher in forests at the extremes of the climatic gradient.In most of the investigated forest types,it was mainly light availability that determined the contribution of the understorey to yearly carbon and nutrient cycling.Overstorey species richness did not affect the contribution of the understorey to carbon and nutrient cycling in any of the investigated forest types.

Species richness, forest types and regeneration of Schima in the subtropical forest ecosystem of Yunnan, southwestern China

Background: Schima genus of Theaceae is confined to subtropics and tropics of South, East and Southeast Asia.Thirteen species of Schima are distributed in subtropical China. Many of them appear as dominant canopy species in the subtropical forests. To date, Schima species richness distribution patterns of China have remained unknown.Meanwhile, there has been a longtime debate as to whether forests dominated by Schima species are early or late successional forests. We aim to clarify Schima species richness patterns and these species' roles in the forest succession and regeneration dynamics of the subtropical ecosystem in Yunnan Province, China.Method: We mapped Schima species richness distribution patterns in China. Based on 71 vegetation plots, we analyzed forest characteristics, population structure, and regeneration dynamics of Schima species in Yunnan.Results: Yunnan was found to harbor the greatest richness and the highest rarity-weighted richness of Schima species in the subtropical regions of China. We classified five primary and six secondary forest types containing Schima species as one of dominants. Yunnan had the high floristic diversity and varying stand structure of forests containing Schima species. The Schima species studied generally had a sporadic regeneration type and a long lifespan. Four species(Schima argentea, Schima villosa, Schima sinensis, Schima sericans) were shade-intolerant. But three species(Schima noronhae, Schima khasiana and Schima wallichii) were considered as bi-modal type species having shade-intolerant and shade-tolerant traits. Schima noronhae was seen to be a top dominant in late successional forests, while S. wallichii was found as a top-dominant in early or middle or late successional forests. S.khasiana, Schima villosa, Schima sinensis usually appeared as a top dominant in early or middle successional secondary forests, though they also presented as a second dominant in late-successional forests. Schima argentea and Schima sericans dominated only in the early or middle/seral successional forests. Schima species' regeneration establishment depended mainly on forest canopy gap formation through moderate human and natural disturbances.Conclusions: Yunnan has high species richness and rarity-weighted richness of Schima. Both moderate human and natural disturbances have provided regeneration niches for Schima species. Some of the Schima species studied as a second dominant(rare as the top-dominant) present in the late-successional forests. Some of them are more often as the top-dominant in early or middle successional forests, where as time goes by the dominance of Schima species would be replaced by their associated dominant taxa such as Castanopsis species.

Micro-site Conditions of Epiphytic Orchids in a Human Impact Gradient in Kathmandu Valley, Nepal

We studied distribution and site conditions of epiphytic orchids in a gradient of human interference in Kathmandu valley, central Nepal. The aim was to understand the recent distribution pattern of epiphytic orchids, with respect to (i) the micro-site conditions and (ii) the type and intensity of land use. The occurrence of epiphytic orchids was recorded for a grid with 1.5 km cell size. The cells represent different types and intensities of human impact. Site factors such as bark rugosity, bark pH, diameter at breast height (dbh; 1.3 m) of host trees, exposure to wind and sunlight intensity were recorded. With regard to the species richness and abundance of epiphytic orchids, we compared different human impact categories from very strong human impact (settlement area) to very low human impact (national park). Remote sensing was used for a supervised classification of land cover. Ficus religiosa turned out to be the most important host species for orchids in urban areas, while Schima wallichii and Alnus nepalensis significantly host orchids in the other categories. Both species richness and abundance of epiphytic orchids were significantly higher under very low human impact (forest in national park) and also some remaining patches of primary forest than the other regions. Micro-climate is crucial for orchid populations. Host bark pH, bark rugosity, sunlight intensity and host exposure were significantly different for all human impact categories in order to harbour epiphytic orchid species. Habitats with a mixture of mature trees are suitable and essential for the conservation of viable populations of epiphytic orchids in settled areas. The study reveals that to improve the population size of orchids it is essential for future urban forestry to: (i) Protect old trees as carriers of existing epiphytic orchid diversity, (ii) protect medium old trees to ensure that they may become old trees, (iii) plant new host trees for the future, (iv) plant in groups instead of single isolate trees. Trees should especially be planted in areas where orchids still exist to provide more trees for orchid population enlargement (e.g. along riparian system). Native species should be favoured; the pool of such native host species is wide.

Stabilization versus decomposition in alpine ecosystems of the Northwestern Caucasus:The results of a tea bag burial experiment

Mountainous areas exhibit highly variable decomposition rates as a result of strong local differences in climate and vegetation type. This paper describes the effect of these factors on two major determinants of the local carbon cycle: litter decomposition and carbon stabilization. In order to adequately reflect local heterogeneity, we have sampled 12 typical plant communities of the Russian Caucasus. In order to minimize confounding effects and encourage comparative studies, we have adapted the widely used tea bag index(TBI) that is typically used in areas with low decomposition. By incubating standardized tea litter for a year, we investigated whether(1) initial litter decomposition rate(k) is negatively correlated with litter stabilization(S) and(2) whether k or S exhibit correlations with altitude and other environmental conditions. Our results show that S and k are not correlated. Altitude, p H, and water content significantly influenced the stabilization factor S, while soil-freezing had no influence. In contrast, none of these factors predicted the decomposition rate k. Based on our data, we argue that collection of decomposition rates alone, as is now common practice, is not sufficient to understand carbon input to soils and can potentially lead to misleading results. Our data on community-specific decomposition and stabilization rates further constrain estimates of litter accumulation in subalpine communities and the potential effects of climate change.

Effects of tree sapling diversity and nutrient addition on herb-layer invasibility in communities of subtropical species

Exotic species are assumed to alter ecosystem functioning. However, little is known of the relationships within vertically structured plant communities such as forests, where tree saplings interact with herbaceous species, especially in the early phases of succession. This relationship was tested in a common garden experiment which assessed the impacts on tree saplings and herbaceous species following nutrient addition and the introduction of exotic herb species. The experiment was established in South- East China using four broad-leaved tree species (Elaeocarpus decipiens, Schima superba, Castanea henryi and Quercus serrata) to study the relationships between tree sapling diversity, herb-layer productivity and invasibility. Tree saplings were planted in monoculture and in mixtures of two and four species. A full factorial design was applied, within which species composition was crossed with nutrient and exotic seed-addition treatments. The seed-addition treatment included mixtures of seeds from eight exotic herb species, and herb community attributes were assessed after a four month growing season. Results indicate that certain tree species negatively affect native as well as exotic herbs;however, the high productivity of native herbs had a stronger negative impact on exotic species than tree saplings. Nutrient addition increased the productivity of exotic herbs but had no effect on native herbs. Remarkably, exotic species introduction had a negative feedback effect on the growth of tree saplings, which highlights the potential of exotic herbs to diminish tree recruitment. Although tree saplings reduced invasive effects on the herb-layer during the earliest phase of forest succession, nutrient addition had a more profound and opposite effect on these invaders.

Diversity, composition and host-species relationships of epiphytic orchids and ferns in two forests in Nepal

Epiphytic plant species are an important part of biological diversity. It is therefore essential to understand the distribution pattern and the factors influencing such patterns. The present study is aimed at observing the patterns of species richness, abundances and species composition of epiphytic orchids and ferns in two subtropical forests in Nepal. We also studied the relationship of host plants(Schima wallichii and Quercus lanata) and epiphyte species. Data were collected in Naudhara community forest(CF) and the national forest(NF) in Shivapuri Nagarjun National Park. The data were analyzed using univariate and multivariate tests. In total, we recorded 41 species of epiphytes(33 orchid and 8 fern species). Orchid species abundance is significantlyhigher in CF compared to NF. Orchid species richness and abundance increased with increasing southern aspect whereas it decreased with increasing canopy cover, and fern species richness increased with host bark roughness. Orchid abundance was positively correlated with increasing bark p H, stem size, tree age and tree height and negatively correlated with increasing steepness of the area. Likewise, fern abundances were high in places with high canopy cover, trees that were tall and big, but decreased with increasing altitude and southern aspect. The composition of the orchid and fern species was affected by altitude, aspect, canopy cover, DBH, number of forks and forest management types. We showed that the diversity of orchid and fern epiphytes is influenced by host characteristics as well as host types. The most important pre-requisite for a high epiphyte biodiversity is the presence of oldrespectively tall trees, independent of the recent protection status. This means:(i) for protection, e.g.in the frame of the national park declaration, such areas should be used which host such old tall trees;and(ii) also in managed forests and even in intensively used landscapes epiphytes can be protected by letting a certain number of trees be and by giving them space to grow old and tall.

Study on Control Scheme for Nonpoint Source Pollution in Dahe Reservoir Water Source Protection Area of Dianchi Lake Basin

[ Objective] The research aimed to study control scheme for nonpoint source pollution in Dahe Reservoir water source protection area of Dianchi Lake basin.[ Method] On the basis of the SPOT5 satellite remote sensing imagery in 2010 and field investigation of GPS record, ecological design for nonpoint source pollution control in Dahe Reservoir water source protection area of Dianchi Lake basin was conducted. Then, the effects of optimization measures were evaluated by the reductions of N and P outputs on different land-use types. E Resultl Control functions of the water source protection area on soil erosion and the emissions of N, P and other pollutants would be promoted after optimization. The optimization meas- ures had a significant effect for prevention and control of the non-point source pollution in the water source protection area. [ Conclusion] The re- search provided scientific basis for promoting ecological construction of the small green basin in Dahe Reservoir water source protection area of Di- anchi Lake basin.