温带干旱、半干旱区生物结皮对土壤有机碳稳定性的影响

Studies on soil carbon flux in biologically crusted soil in Gurbantunggut desert have shown temperature sensitivity of soil carbon flux differed between crust types, and moreover, significant difference of soil carbon flux between crust types was dependent on precipitation size. These results suggest that physiological activities and soil organic carbon stability in crusted soil may be related with the development of biological soil crusts, and are responsible for variation in soil carbon flux. In this project, firstly, we will investigate soil carbon stability and its dependence on regional precipitation, temperature and soil texture, as well as biotic parameters of biological crusts in typical crusted soil of five chosen sites in northern China, and expect to elucidate the variability of soil carbon stability and its potential direct and indirect relations with the above parameters. Secondly, we will examine the soil organic carbon decomposition responses of a group of four soil particle sizes to a gradient of soil moistures and temperatures, and expect to know the dependence of soil organic carbon stability related with soil particle size on soil moisture and temperature in biologically crusted soil. At last, specifically taking biologically crusted soil in Gurbantunggut desert as an example, we will measure soil organic carbon decomposition after simulated precipitation in field and after additions of microbial selective inhibitors, glucose, starch, NH4NO3 in lab, and expect to elucidate effects of microbial functional type and microbial organic carbon utilization type in crust organisms on soil organic carbon stability. Through the above studies, we will elucidate the effects of biological soil crusts on soil organic carbon stability in arid and semiarid regions.

对我国古尔班通古特沙漠生物结皮发育土壤碳通量的研究发现，土壤碳通量的温度敏感性因结皮类型而异，并且，碳通量在结皮类型间的显著差异与降水量有关。这暗示，结皮生理活动和土壤有机碳稳定性可能与结皮发育有关，并且结皮发育和碳素稳定性特征是土壤碳通量变异的主要原因。本项目首先以我国北方5个不同生境中典型结皮发育土壤为例，研究土壤碳素稳定性及其与区域降水、气温、土壤质地和结皮生物学参数的关系，阐明结皮发育土壤的碳素稳定性特征及在区域尺度上变异的原因；其次，研究不同粒径土壤碳素分解与土壤含水量和温度的关系，阐明水、温对不同稳定性有机碳分解的影响；最后，以古尔班通古特沙漠典型结皮发育土壤为例，野外自然降水后和室内添加微生物选择性抑制剂、碳源和氮源，测定土壤碳通量，阐明微生物功能型和碳素利用型对土壤有机碳稳定性的影响；通过以上研究，综合分析我国干旱、半干旱区生物结皮对土壤有机碳稳定性的影响。

荒漠面积约占全球陆地面积的20%，这一区域不仅对气候变化较为敏感，而且具有很大碳截存潜力。生物土壤结皮作为干旱、半干旱区土壤表层的主要生物覆被物,它们的光合碳固定已经得到了广泛的证实,然而,我们前期的研究发现,结皮发育区土壤表现出碳释放,这与结皮光合碳固定是土壤有机碳储量提高的主要贡献者这一研究结论不一致。本项目以我国北方干旱、半干旱区为样带，选择生物结皮发育良好的区域为研究样点，通过一系列的野外取样和观测以及室内测试分析，研究了生物结皮发育区土壤有机碳的稳定性特征，主要包括如下几个方面：一，沿我国北方干旱-半干旱-半湿润区这一样带，选择生物土壤结皮主要分布区为关键研究样点（古尔班通古特沙漠阜康站，腾格里沙漠沙坡头站，安塞县，吴起县，盐池县和科尔沁沙地奈曼站），观测并量化了生物结皮发育区土壤呼吸及其对温度的敏感性特征（Q10值）；二，以生物结皮发育良好的古尔班通古特沙漠为典型样点，研究生物结皮发育区土壤碳通量特征，发现在高温低湿的季节（4-10月），土壤以碳释放为主导，而在春季积雪消融期，土壤表现出碳吸收；三，以古尔班通古特沙漠为研究点，选择不同生物土壤结皮发育土壤和优势灌木生长点，调查研究了土壤有机碳在土壤剖面和土壤粒径间的分布特征，并给出了土壤有机碳稳定性与土壤覆被和区域降水之间的关系；四，测定我国北方17个样点上生物结皮层土壤微生物主要生物学指标，包括微生物生物量和多样性，分析了结皮发育土壤有机碳稳定性维持的微生物学机制；五，通过模拟北方降雨增加和氮沉降加剧的背景，观测结皮发育土壤碳通量和暗呼吸，并同步观测生物结皮群落结构特征和物种组成变化，量化降水增加和氮沉降对生物结皮发育土壤表层有机碳稳定性影响的强度和趋势。.