An Assessment of Storage Terms in the Surface Energy Balance of a Subalpine Meadow in Northwest China

The heat storage terms in the soil-vegetation-atmosphere system may play an important role in the surface energy budget.In this paper,we evaluate the heat storage terms of a subalpine meadow based on a ficld experiment conducted in the complex terrain of the eastern Qilian Mountains of Northwest China and their impact on the closure of the surface energy balance under such non-ideal conditions.During the night, the average sum of the storage terms was -5.5 W m,which corresponded to 10.4%of net radiation.The sum of the terms became positive at 0730 LST and negative again at about 1500 LST,with a maximum value of 19 W mobserved at approximately 0830 LST.During the day,the average of the sum of the storage terms was 6.5 W m,which corresponded to 4.0%of net radiation.According to the slopes obtained when linear regression of the net radiation and partitioned fluxes was forced through the origin,there is an imbalance of 14.0%in the subalpine meadow when the storage terms are not considered in the surface energy balance.This imbalance was improved by 3.4%by calculating the sum of the storage terms.The soil heat storage flux gave the highest contribution(1.59%),while the vegetation enthalpy change and the rest of the storage terms were responsible for improvements of 1.04%and 0.77%,respectively.

Warming Stimulated Soil Respiration in a Subalpine Meadow in North China

In order to explore the response of soil respiration in grassland to global warming,we carried out a warming experiment with open top chambers(OTCs)in the subalpine meadow,Mount Wutai in north China.Our results showed in the subalpine meadow across 2500-2700 m above the sea level(ASL),with OTCs,soil respiration increased by 2.00μmol·m^(-2)·s^(-1)as soil temperature increased by 1.25℃on average.Warming decreased soil moisture over the experiment periods except in October 2019 when snow melted in OTCs.Warming effect on soil respiration peaked at 178.31%in October 2019.In control and warming treatment,based on exponential regression equations,soil temperature alone accounted for 85.3%and 61.2%of soil respiration variation,respectively.In control treatment soil moisture alone explained 23.2%of soil respiration variation based on the power regression equation while in warming treatment they were not significantly correlated with each other.The response of soil respiration to warming relied on altitudes as well as the time of the year,but was not inhibited by soil moisture,labile carbon pool,and available nitrogen.We concluded soil temperature was the main factor influencing soil respiration,and global warming would stimulate soil respiration in the subalpine meadows of Mount Wutai in the future.Our analysis provided new data on characteristics and mechanisms of the response of soil respiration to warming,and helped to further understand the relationship between carbon cycle and climate change.

Functional diversity and redundancy of subalpine meadows subjected to anthropogenic disturbances

Aims The aims of this study were to assess how functional diversity(FD)and functional redundancy respond to subalpine meadow ecosystem degradation under anthropogenic disturbance and how species contribute to functional redundancy along the disturbance gradient.Methods The study was carried out in the subalpine meadow in Mount Jade Dragon,which is located at the southeastern edge of the Tibetan Plateau.Four disturbance intensities[no disturbance(ND),weak disturbance(WD),moderate disturbance(MD)and severe disturbance(SD)]were identified.Species richness,soil properties and five key plant functional traits were assessed along the disturbance gradient.Simpson’s diversity index,FD based on the Rao algorithm,functional redundancy,community-weighted mean of each functional trait and species-level functional redundancy were determined.Important Findings Unimodal change pattern of FD and functional redundancy along the disturbance gradient were found in the present study,with their maximum in MD and WD,respectively.Species diversity showed a decreasing trend with increasing disturbance intensity.As disturbance intensified,species with traits related to conservative growth strategies,such as low specific leaf area(SLA)and high leaf dry matter content(LDMC),decreased,whereas species with resource acquisitive strategies,such as small plant,high SLA and low LDMC,increased in the community.At the species level,species showed species-specific roles in functional redundancy.Notably,some species were important in the community in terms of their unique function.For instance,Ligularia dictyoneura in ND and Potentilla delavayi in MD and SD.