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具有重要科学意义。本研究旨在揭示青藏高原北部多年冻土对植被地上、地下生物量的影响。研究于2014-2016年的生长季开展了相关调查，测定指标包括土壤温度、土壤含水率、活动层厚度（active-layer thickness）、植被覆盖度、地上生物量（aboveground biomass, AGB）、地下生物量（belowground biomass, BGB）以及土壤有机碳含量。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。分析结果显示，地上生物量与地下生物量、土壤含水率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可能会抑制植被生长。地下生物量与活动层厚度呈正相关，与土壤含水率呈负相关。本研究表明，青藏高原北部多年冻土退化会降低土壤含水率，进而导致地上生物量下降。土壤含水率降低同样会引起地下生物量减少，但干旱生境中的植被往往会通过提升地下生物量来获取更多水分以支持自身生长。