Unveiling evapotranspiration patterns and energy balance in a subalpine forest of the Qinghai-Tibet Plateau:observations and analysis from an eddy covariance system

Evapotranspiration is an important parameter used to characterize the water cycle of ecosystems.To under-stand the properties of the evapotranspiration and energy balance of a subalpine forest in the southeastern Qinghai-Tibet Plateau,an open-path eddy covariance system was set up to monitor the forest from November 2020 to October 2021 in a core area of the Three Parallel Rivers in the Qing-hai-Tibet Plateau.The results show that the evapotranspira-tion peaked daily,the maximum occurring between 11:00 and 15:00.Environmental factors had significant effects on evapotranspiration,among them,net radiation the greatest(R^(2)=0.487),and relative humidity the least(R^(2)=0.001).The energy flux varied considerably in different seasons and sensible heat flux accounted for the main part of turbulent energy.The energy balance ratio in the dormant season was less than that in the growing season,and there is an energy imbalance at the site on an annual time scale.

Reconsidering the efficiency of grazing exclusion using fences on the Tibetan Plateau

Grazing exclusion using fences is a key policy being applied by the Chinese government to rehabilitate degraded grasslands on the Tibetan Plateau(TP)and elsewhere.However,there is a limited understanding of the effects of grazing exclusion on alpine ecosystem functions and services and its impacts on herders’livelihoods.Our meta-analyses and questionnaire-based surveys revealed that grazing exclusion with fences was effective in promoting aboveground vegetation growth for up to four years in degraded alpine meadows and for up to eight years in the alpine steppes of the TP.Longer-term fencing did not bring any ecological and economic benefits.We also found that fencing hindered wildlife movement,increased grazing pressure in unfenced areas,lowered the satisfaction of herders,and rendered substantial financial costs to both regional and national governments.We recommend that traditional free grazing should be encouraged if applicable,short-term fencing(for 4-8 years)should be adopted in severely degraded grasslands,and fencing should be avoided in key wildlife habitat areas,especially the protected large mammal species.

Divergent biomass partitioning to aboveground and belowground across forests in China

Aims Belowground to aboveground biomass(BGB/AGB)ratio is a highly valued parameter of the terrestrial carbon cycle and productivity.However,it remains far from clear whether plant biomass partition-ing to aboveground and belowground is isometric(equal partition-ing)or allometric(unequal partitioning)at community levels and what factors are necessary in order to regulate the partitioning.This study aimed to comprehensively find out the patterns of biomass partitioning and their regulatory factors across forests in China.Methods The data of AGB and BGB were compiled from 1542 samples for communities across forests in China.Standardized major axis regression was conducted to examine whether AGB and BGB were allocated isometrically or allometrically at a community level.Redundancy analysis was used to analyze the relationships of BGB/AGB ratio with climatic factors and soil properties.Important Findings We found that the slopes of the relationship between logAGB and logBGB were not always comparable to 1.0(isometric allocation)at community levels,including primary forest,secondary forest,and planted forest.Meanwhile,samples in clay,loam,and sand soil types also presented the same phenomenon.Furthermore,the radically different allocations of AGB and BGB were found in northern and southern China.Environmental factors totally explained 3.86%of the variations in the BGB/AGB ratio at the community level,which include the mean annual precipitation,mean annual temperature,potential water deficit index,soil car-bon content,soil nitrogen content,soil clay,soil loam,soil sand,soil pH,and soil bulk density.In addition,the environmental fac-tors also have effects on the BGB/AGB ratio in other categories.The patterns revealed in this study are helpful for better under-standing biomass partitioning and spreading the carbon circle models.