Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China.
Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2021 Mar 20;761:143282. doi: 10.1016/j.scitotenv.2020.143282. Epub 2020 Oct 29.
Assessment of the global terrestrial carbon (C) sink remains uncertain, and the uncertainty is largely derived from dryland ecosystems. Here we investigated the uncertainty and dynamics of gross primary productivity (GPP) by distinguishing the contributions of soil microbial primary producers and plants to CO fixation during four sequential growing seasons in a fragile dry grassland on the Tibetan Plateau. The results demonstrated that soil microbial GPP consistently accounted for a high proportion of plant GPP (18.2%), and both exhibited similar seasonal patterns during the four-year observation. Soil microbial GPP demonstrated a much greater interannual variation (76.1%) than plant GPP (15.1%), indicating that the interannual GPP uncertainty could be largely from microbial primary producers. Regression analysis indicated that plant GPP had higher sensitivity (demonstrated by slope) than soil microbial GPP to both soil water content and temperature. The GPP ratio of soil microbes to plants also demonstrated a clear seasonal change, and peaked in July in the four-year observation, with a minimum interannual variation (6.8%). The GPP ratio enhanced with increasing soil water content (P < 0.001), but did not correlate with soil temperature. Our findings suggest the great potential of soil microbial GPP, and challenge the plant-oriented models of terrestrial C estimation, which account for plant GPP but ignore soil microbial GPP. Thus, a more robust framework needs to incorporate both soil microbial and plant GPPs for accurately assessing C balance.
全球陆地碳（C）汇的评估仍然不确定，而这种不确定性主要来自于旱地生态系统。在这里，我们通过区分土壤微生物初级生产者和植物对 CO 在青藏高原脆弱干旱草原上四个连续生长季节的固定作用，研究了总初级生产力（GPP）的不确定性及其动态。结果表明，土壤微生物 GPP 始终占植物 GPP 的很大比例（18.2%），并且在四年的观测期间表现出相似的季节性模式。土壤微生物 GPP 的年际变化（76.1%）明显大于植物 GPP（15.1%），这表明年际 GPP 不确定性可能主要来自微生物初级生产者。回归分析表明，与土壤微生物 GPP 相比，植物 GPP 对土壤水分含量和温度的敏感性更高（表现为斜率）。土壤微生物与植物的 GPP 比值也表现出明显的季节性变化，在四年观测中 7 月达到峰值，年际变化最小（6.8%）。GPP 比值随土壤水分含量的增加而增强（P < 0.001），但与土壤温度无关。我们的研究结果表明了土壤微生物 GPP 的巨大潜力，这对以植物为导向的陆地 C 估算模型提出了挑战，这些模型只考虑了植物 GPP 而忽略了土壤微生物 GPP。因此，需要更稳健的框架来同时纳入土壤微生物和植物 GPP，以准确评估 C 平衡。
