氮和硫在人为扰动的青藏高原高寒森林中的分布特征OA北大核心CSTPCD

The Tibetan Plateau is characterized by high elevation,low precipitation,low temperatures,and fragile ecosystems.The alpine forests of the Tibetan Plateau constitute 12.1%of the total plateau area,making it a representative ecosystem in the region.Alpine forests are characterized by high elevation,low precipitation and low rate of nitrogen and sulfur biochemical reaction.Therefore,they have a lower critical load for nitrogen and sulfur deposition than tropical and subtropical forests,and they are more sensitive to increasing atmospheric nitrogen and sulfur deposition.The increasing nitrogen and sulfur deposition may pose negative influences on soil and surface water chemistry in alpine forests,causing damages to ecological balance and health of the forest ecosystem.Focusing on the alpine forests of the Tibetan Plateau located in regions affected by anthropogenic disturbances(Datong and Huangyuan),this study aimed to analyze the distribution characteristics of nitrogen and sulfur between throughfall,surface soil water,and surface water.The findings of this research can serve as a regional example for developing comprehensive air pollution control policies and ecological protection policies in the Tibetan Plateau.The pH values of throughfall,surface soil water,and surface water in both Datong and Huangyuan alpine forests fell within the range of 6 to 8.Calcium ions are the main base cations found in throughfall,surface soil water,and surface water,while sulfate and nitrate are the main anions.The sulfur deposition in the Huangyuan alpine forest site(0.48 keq·hm-2·a-1)exceeded the least critical load for alpine forests(0.22 keq·hm-2·a-1).The nitrogen deposition in the anthropogenic disturbed Tibetan Plateau alpine forests(0.22 keq·hm-2·a-1 for Datong and 0.30 keq·hm-2·a-1 for Huangyuan)exceeded the average nitrogen deposition of the Tibetan Plateau(0.21 keq·hm-2·a-1).Still,it remained below the least critical load for the alpine forests(0.71 keq·hm-2·a-1).Consequently,nitrogen deposition is less of a concern for the region's forests than sulfur deposition.The nitrogen and sulfur flux in both alpine forests'throughfall were higher than that in surface soil water(nitrogen:0.16 keq·hm-2·a-1,sulfur:0.21 keq·hm-2·a-1)and surface water(nitrogen:8.37×10-3 keq·hm-2·a-1,sulfur:0.13 keq·hm-2·a-1).As a result,alpine forests are manifested as the nitrogen and sulfur sinks in the litter layer and alpine forest small watershed.Although little nitrogen and sulfur leach in the alpine forests,increasing nitrogen and sulfur deposition will increase nitrogen and sulfur flux in surface soil and surface water.As a result,the rising emissions of nitrogen and sulfur pollution pose an increasing ecological threat to the alpine forests in the Tibetan Plateau.