Spatial patterns of leaf nitrogen and phosphorus stoichiometry across southeast to central Tibet

Leaf N and P stoichiometry in terrestrial ecosystems has been widely investigated in recent years owing to the importance of these elements in improving the predicted vegetation responses to global changes.The vertical distribution of leaf N and P stoichiometry has attracted increasing attention because of the dramatic changes in environmental factors at regional scales.However,the characteristics of leaf N and P stoichiometry in the southeast Qinghai–Tibet plateau(SET)are not clear,although this area is sensitive to global change.Here,we analyzed the leaf N and P concentrations in dominant plant species on natural altitudinal gradients on the Duoxiongla(DXL),Sejila(SJL),Mila(ML),and Gangbala(GBL)mountains across the SET all the way to central Tibet.Our results showed that the leaf N concentrations were comparable among the regions,whereas the leaf P concentrations dramatically decreased from SET to central Tibet(CT).The leaf N concentrations were 23.6,21.3,20.8,and 22.4 g kg^(-1),and the leaf P concentrations were 2.40,2.49,1.94,and 1.59 g kg^(-1) on the SJL,DXL,ML and GBL mountains,respectively.The leaf N/P ratios on the DXL,SJL,ML,and GBL mountains were 8.81,10.3,11.2,and 14.2,respectively.Considering the increasing trend of the leaf N/P ratio from southeast Qinghai–Tibet plateau to central Tibet,N limitation might widely exist in well vegetated ecosystems in the Qinghai–Tibet plateau.

Research Progress on Extraction Technology of Polysaccharides from Polygonatum spp.

In this paper,the extraction methods of polysaccharides from Polygonatum spp.in recent years are reviewed to provide reference for further development and utilization of Polygonatum spp.In addition,the prospects of the extraction process of polygonatum polysaccharides are explored.

Effects of Different Land Use Patterns on Soil Properties in the Lower Reaches of Niyang River of Tibet

[Objectives]This study was conducted to provide scientific basis for rational utilization and sustainable management of agricultural and forestry land resources in southeast Tibet.[Methods]Soil samples were stratified by standard sampling method(0-10,10-20,20-40,40-60 and 60-100 cm)in the lower reaches of Niyang River Basin under three different types of land cover of forest,grassland and farmland.The effects of different land use on soil properties were studied.[Results]Soil temperature and humidity affected soil properties together.The pH value and bulk density increased with the increase of soil depth for farmland,grassland and forest soil.Natural forest had the highest soil nutrient contents,followed by farmland,and grassland had the lowest soil nutrient contents.Soil organic carbon and organic nitrogen contents decreased with the increase of soil depth in the three land use patterns,and the surface aggregation of soil organic carbon and organic nitrogen was more obvious.Compared with natural vegetation,the organic carbon content of farmland was significantly reduced by 8.5%-15.3%and the organic nitrogen content by 11.1%-11.7%.[Conclusions]The change of land use is a proper way to benefit the development of soil properties and improve soil properties and quality in Niyang River Basin.

Climate change has more adverse impacts on the higher mountain communities than the lower ones: people’s perception from the northern Himalayas

The Himalayas are assumed to experience rapid climate change,with serious environmental,social and economic consequences for people living in and around the mountain area.However,the extent of climate change and its impact on the region are underexplored,especially on northern slope of the mountains.Based on local knowledge,we report perceived changes in climate and consequences of such changes for natural andsocial systems.The respondents in this study were distributed at a continuous elevation gradient of 3570-4646 m above sea level in the northern Himalayas.Therefore,it is possible to analyze the process of the shift of bioclimate zones under climate change and the differences in climate change effects cross altitudes.Among those in the pastoral area(Zhegu town)with an altitude of 4600 m,91.2%(n=114)of the respondents believe that the climate is obviously changing;the ratio of reporting rainfall decreasing is 77.2%(n=114);those who perceive delayed rainy season,and increased climate change-related natural disasters account for 38.9%(n=113),72.8%(n=103),respectively;more than two thirds(70.3%)(n=111)view drought as the biggest challenge to address climate change,and more than half(59.3%)(n=113)of the respondents believe that the impact of climate change is mainly negative.All these data rank first among the four survey areas(Zhegu town/pastoral region,Nedong County/crop growing regions,Zhanang County/crop growing region and Nagarze County/farming-pastoral region).Due to climate warming,Labidura riparia spreads to a higher altitude in the basins in Nedong County(Shannan City,Tibet)and Zhanang County(Shannan City,Tibet)at the rate of 31.1±6.4 m/a and 46.7±8.8 m/a,respectively in elevation.Most of the respondents view the natural variability as the main cause of climate changes,only 10.7%-29.0%among them view human activities as the main reason.Key challenges for local people to address climate change include droughts and economic hardship.Most local perceptions conform to scientific data.Comparative analysis of people’s perception of climate change impacts in different regions of the Himalayas will enhance the understanding of climate change effects on the whole region.