生物结皮-土壤呼吸对冬季低温及模拟增温的响应

以腾格里沙漠东南缘天然植被区藓类结皮和藻-地衣结皮-土壤为研究对象,利用开顶式生长室(OTC),采用Li-8150系统连续测定了冬季(2015年11月—2016年1月)低温环境下两类结皮-土壤呼吸的变化,分析了低温及模拟增温对两类结皮-土壤呼吸的影响.结果表明: 观测期内,藓类结皮、藻-地衣结皮-土壤呼吸速率分别为-0.052～0.418、-0.032～0.493 μmol·m^-2·s^-1,且藓类结皮显著高于藻-地衣结皮-土壤系统.不同类型结皮-土壤呼吸速率与5 cm土壤温度和土壤体积含水量均呈显著线性正相关,增温主要是通过加速土壤水分蒸散而抑制生物结皮-土壤呼吸速率.在整个观测期,藓类结皮-土壤系统累计排放9.90 g C·m^-2,显著高于藻-地衣结皮-土壤系统的7.00 g C·m^-2.研究区生物结皮-土壤系统冬季累计排放7.40 g C·m^-2,是该荒漠生态系统全年碳收支的重要组成部分.

Response of biocrust-soil system respiration to winter low temperature and simulated warming

To study the effects of low temperature and simulated warming on respiration of biocrust-soil systems, intact soil columns covered by two dominant types of biocrusts (moss and algae-lichen crusts), were collected in a natural vegetation area in the southeast fringe of the Tengger Desert. Automated soil respiration system (Li-8150) was used to measure respiration rates in biocrust-soil systems under warming (by placing them in an open top chamber) and non-warming treatments in winter (from November 2015 to January 2016). During the whole observation period, soil respiration rates covered by moss crusts were significantly higher than those covered by algae-lichen crusts, which were -0.052 to 0.418 and -0.032 to 0.493 μmol·m^-2·s^-1, respectively. The respiration rates of the two types of biocrust-soil systems showed significant positive linear correlations with soil temperature and volumetric soil water content at 5 cm depth. Through speeding-up the evaporation rates of soil moisture, imitated warming in winter impeded respiration rates of the two biocrust-soil systems. During the whole observation period, the cumulative carbon (C) release by moss crust-soil system (9.90 g C·m^-2) was dramatically higher than that of algae-lichen crust-soil system (7.00 g C·m^-2). The cumulative C release by the biocrust-soil systems in this region in winter was 7.40 g C·m^-2, thus comprising an important part of annual C budget in the desert ecosystems.