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.

Improving tree health assessment accuracy at low temperatures:considering the effect of trunk ice content on electrical resistance and stress wave tomography

Accurate decay detection and health assessment of trees at low temperatures is an important issue for forest management and ecology in cold areas.Low temperature ice formation on tree health assessment is unknown.Because electric resistance tomography and stress wave tomography are two widely used methods for the detection of tree decay,this study investigated the effect of ice content on trunk electrical resistance and stress wave velocity to improve tree health assessment accuracy.Moisture content,trunk electrical resistance and stress wave velocity using time domain reflectometry were carried out on Larix gmelinii and Populus simonii.Ice content is based on moisture content data.The ice content of both species showed a trend of increasing and then decreasing.This was opposite with ambient temperatures.With the decrease of temperatures,daily average ice content increased,but the range narrowed gradually and both electrical resistance and stress wave velocity increased.Both increased rapidly near 0℃,mainly caused by ice formation(phase change and freezing of free water)in live trees.In addition,both are positively correlated with ice content.The results suggest that ice content should be considered for improving the accuracy of tree decay detection and health evaluation using electric resistance tomography and stress wave velocity methods under low temperatures.

Late Pleistocene glaciation of the Hulifang Massif of Gongwang mountains in Yunnan Province

Late Pleistocene glaciation was restricted to only a few high mountains in eastern China. The Gongwang mountains constitute one of the typical places once glaciated. Geomorphic mapping of the area and the TL dating provides evidence for at least four distinct glaciations. YJT-Ⅰ glacial advance occurred about 100 ka BP and two TL absolute ages （101,100 ± 7780 a BP; 104,000± 8300 a BP） indicate this advance happened during the Penultimale Glaciation. The early stage glacial advance （YJT-Ⅱ advance） during the last glaciation occurred about 40,920 ± 3400 a BP. The last glacial maximum advance （YJT-Ⅲ advance） about 18-25 ka BP, which sustained by two TL ages （18,230 ±1420 a BP; 25,420 ± 2110 a BP）. The Penultimale and the early stage glaciations were more extensive and the last glacial maximum （LGM） and the late-glacial period （YJT-Ⅳ advance, 10 ka BP） were progressively less extensive. Correlated with the other mountains in eastern China, these glacial advances in the Gongwang mountains just like the advances in the western part such as Diancang mountains, Yulong mountains of Yunnan Province and the glacier series are more complete than the adjacent mid-latitude regions such as Taibai mountain and Taiwan mountains and are roughly representative of climate changes during the last glacial cycle in Yunnan Province.

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.