Impacts of permafrost on above- and belowground biomass on the northern Qinghai-Tibetan Plateau

Because permafrost is extremely sensitive to climate change, it is of great importance to understand the relationship between permafrost and vegetation biomass. This study aims to reveal the impacts of permafrost on above- and belowground vegetation biomass on the northern Qinghai-Tibetan Plateau. Soil temperature, moisture, active-layer thickness, vegetation coverage, aboveground biomass (AGB), belowground biomass (BGB), and soil organic carbon were investigated in the growing seasons during 2014–2016. The average AGB and BGB in the growing seasons were 0.036 and 0.83 g cm−2, respectively. The AGB was significantly positively correlated with BGB, soil moisture, and soil organic carbon content, but was significantly negatively correlated with mean annual ground temperature and active-layer thickness, suggesting that permafrost degradation can potentially decrease vegetation growth. The BGB was positively correlated with active-layer thickness and was negatively correlated with soil moisture. This study suggests that permafrost degradation can decrease the soil moisture on the northern Qinghai-Tibetan Plateau and thus decrease AGB. The decreased soil moisture can also lead to lower BGB, while the vegetation in drier soils tends to have higher BGB to access more water resources for plant growth.

由于多年冻土对气候变化极为敏感，厘清多年冻土与植被生物量之间的关联至关重要。本研究旨在揭示青藏高原北部多年冻土对地上植被生物量（aboveground biomass, AGB）和地下植被生物量（belowground biomass, BGB）的影响。本研究于2014—2016年的生长季内，对土壤温度、土壤湿度、活动层厚度、植被覆盖度、地上生物量、地下生物量以及土壤有机碳开展了实地调查。生长季内地上生物量与地下生物量的平均值分别为0.036 g·cm⁻²和0.83 g·cm⁻²。地上生物量与地下生物量、土壤湿度及土壤有机碳含量呈显著正相关，而与年平均地温及活动层厚度呈显著负相关，这表明多年冻土退化或可抑制植被生长。地下生物量与活动层厚度呈正相关，与土壤湿度呈负相关。本研究表明，青藏高原北部的多年冻土退化可降低区域土壤湿度，进而减少地上生物量。土壤湿度降低同样会导致地下生物量下降，而生长于较干燥土壤中的植被往往会分配更多生物量至地下，以获取更多水分供植株生长。