State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shannxi, China.
University of Chinese Academy of Sciences, Beijing, China.
PLoS One. 2018 Apr 6;13(4):e0195400. doi: 10.1371/journal.pone.0195400. eCollection 2018.
The spatial heterogeneity of soil respiration and its temperature sensitivity pose a great challenge to accurately estimate the carbon flux in global carbon cycling, which has primarily been researched in flatlands versus hillslope ecosystems. On an eroded slope (35°) of the semiarid Loess Plateau, soil respiration, soil moisture and soil temperature were measured in situ at upper and lower slope positions in triplicate from 2014 until 2016, and the soil biochemical and microbial properties were determined. The results showed that soil respiration was significantly greater (by 44.2%) at the lower slope position (2.6 μmol m-2 s-1) than at the upper slope position, as were soil moisture, carbon, nitrogen fractions and root biomass. However, the temperature sensitivity was 13.2% greater at the upper slope position than at the lower slope position (P < 0.05). The soil fungal community changed from being Basidiomycota-dominant at the upper slope position to being Zygomycota-dominant at the lower slope position, corresponding with increased β-D-glucosidase activity at the upper slope position than at the lower slope position. We concluded that soil respiration was enhanced by the greater soil moisture, root biomass, carbon and nitrogen contents at the lower slope position than at the upper slope position. Moreover, the increased soil respiration and decreased temperature sensitivity at the lower slope position were partially due to copiotrophs replacing oligotrophs. Such spatial variations along slopes must be properly accounted for when estimating the carbon budget and feedback of future climate change on hillslope ecosystems.
土壤呼吸的空间异质性及其对温度的敏感性极大地挑战了全球碳循环中碳通量的准确估算，而这主要是在平原与山坡生态系统之间展开的研究。在半干旱黄土高原的一个侵蚀性斜坡（35°）上，我们于 2014 年至 2016 年在上下坡位置重复进行了 3 次原位测量，以获取土壤呼吸、土壤湿度和土壤温度，并测定了土壤生化和微生物特性。结果表明，下坡位置（2.6 μmol m-2 s-1）的土壤呼吸显著高于上坡位置（高 44.2%），下坡位置的土壤湿度、碳、氮分数和根生物量也更高。然而，上坡位置的温度敏感性比下坡位置高 13.2%（P < 0.05）。土壤真菌群落从上坡位置的担子菌为主变为下坡位置的接合菌为主，与上坡位置的β-D-葡萄糖苷酶活性高于下坡位置相对应。我们的结论是，下坡位置的土壤水分、根生物量、碳和氮含量高于上坡位置，从而增强了土壤呼吸。此外，下坡位置土壤呼吸增加和温度敏感性降低部分归因于富养生物取代了贫养生物。在估计山坡生态系统的碳预算和未来气候变化的反馈时，必须充分考虑这种沿坡度的空间变化。
