Shapotou Desert Research and Experimental Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, Gansu, China.
University of Chinese Academy of Sciences, Beijing, China.
PLoS One. 2018 Apr 6;13(4):e0195606. doi: 10.1371/journal.pone.0195606. eCollection 2018.
Soil respiration induced by biological soil crusts (BSCs) is an important process in the carbon (C) cycle in arid and semi-arid ecosystems, where vascular plants are restricted by the harsh environment, particularly the limited soil moisture. However, the interaction between temperature and soil respiration remains uncertain because of the number of factors that control soil respiration, including temperature and soil moisture, especially in BSC-dominated areas. In this study, the soil respiration in moss-dominated crusts and lichen-dominated crusts was continuously measured using an automated soil respiration system over a one-year period from November 2015 to October 2016 in the Shapotou region of the Tengger Desert, northern China. The results indicated that over daily cycles, the half-hourly soil respiration rates in both types of BSC-covered areas were commonly related to the soil temperature. The observed diel hysteresis between the half-hourly soil respiration rates and soil temperature in the BSC-covered areas was limited by nonlinearity loops with semielliptical shapes, and soil temperature often peaked later than the half-hourly soil respiration rates in the BSC-covered areas. The average lag times between the half-hourly soil respiration rates and soil temperature for both types of BSC-covered areas were two hours over the diel cycles, and they were negatively and linearly related to the volumetric soil water content. Our results highlight the diel hysteresis phenomenon that occurs between soil respiration rates and soil temperatures in BSC-covered areas and the negative response of this phenomenon to soil moisture, which may influence total C budget evaluations. Therefore, the interactive effects of soil temperature and moisture on soil respiration in BSC-covered areas should be considered in global carbon cycle models of desert ecosystems.
生物土壤结皮（BSC）引起的土壤呼吸是干旱和半干旱生态系统碳（C）循环中的一个重要过程，在这些生态系统中，维管植物受到恶劣环境的限制，特别是土壤水分有限。然而，由于控制土壤呼吸的因素众多，包括温度和土壤水分，特别是在 BSC 占主导地位的地区，温度和土壤呼吸之间的相互作用仍然不确定。本研究在中国北方腾格里沙漠的沙坡头地区，使用自动土壤呼吸系统连续测量了 2015 年 11 月至 2016 年 10 月一年中苔藓结皮和地衣结皮覆盖区的土壤呼吸。结果表明，在日周期内，两种 BSC 覆盖区的半小时土壤呼吸速率通常与土壤温度有关。BSC 覆盖区土壤呼吸速率与土壤温度之间的日滞环被具有半椭圆形的非线性环所限制，并且土壤温度通常在 BSC 覆盖区的半小时土壤呼吸速率之后达到峰值。两种 BSC 覆盖区的土壤呼吸速率与土壤温度之间的平均滞后时间在日周期内为两小时，与体积土壤水分含量呈负线性关系。我们的研究结果突出了 BSC 覆盖区土壤呼吸速率与土壤温度之间存在的日滞环现象，以及该现象对土壤水分的负响应，这可能会影响总 C 预算评估。因此，在沙漠生态系统的全球碳循环模型中，应该考虑 BSC 覆盖区土壤温度和水分对土壤呼吸的相互作用影响。
