高寒沙区生物土壤结皮覆盖土壤碳释放动态

The dynamics of soil carbon release covered with biological soil crusts in Alpine sand area

生物土壤结皮广泛分布于荒漠生态系统,能够通过自身的呼吸作用影响土壤碳释放以及区域碳循环过程。在具有典型高寒沙区气候特征的青藏高原东北部(青海共和盆地),以广泛分布于人工植被恢复区的藻类和藓类结皮为研究对象,裸地为对照,观测了裸地与两种类型生物土壤结皮去除和覆盖土壤碳释放速率的日动态和生长季动态规律,探讨生物土壤结皮对土壤碳释放量的影响。结果表明:生物土壤结皮去除和覆盖土壤碳释放速率日动态和生长季动态特征与裸地一致,均呈"单峰"曲线。生物土壤结皮覆盖土壤的日最大碳释放速率出现于13:00左右,裸地与去除结皮土壤的日峰值均出现于15:00左右,生物土壤结皮的存在使土壤碳释放速率的日峰值出现时间提前2h左右,各观测类型生长季内碳释放速率最大值均出现在8月。在相对干旱年份(2017),藻类和苔藓结皮覆盖导致土壤碳释放量分别增加了22.07%和85.61%,其中,藻类和苔藓结皮层碳释放量占增加量的67.60%和25.76%;而在相对湿润年份(2018),藻类和苔藓结皮覆盖导致土壤碳释放量分别增加了139.37%和290.53%,二者结皮层碳释放量分别占增加量的69.09%和45.59%,生物土壤结皮发育促进了土壤的碳释放。温度对土壤碳释放变化的贡献率为48.89%,是高寒沙区土壤碳释放日动态变化的关键驱动因子。因此,在核算荒漠生态系统碳交换过程中,应充分考虑各区域不同类型生物土壤结皮对土壤碳释放产生的影响。

Biological soil crusts were widely distributed in desert ecosystems, which could affect soil carbon release and regional carbon cycle through their own respiration. In this study, we took the algae and moss crusts as the research object, which were widely distributed in artificial vegetation area in the northeast of Qinghai-Tibet Plateau(Gonghe basin, Qinghai). We observed the diurnal and growth seasonal dynamics of soil carbon release rate in bare land and two types of biological soil crusts covered soil. The results showed that the diurnal and growth seasonal dynamic characteristics of soil carbon release rate with and without covered biological soil crusts were consistent with that of bare land, showing a "single peak" curve. The maximum daily carbon release rate of covered biological soil crusts appeared at about 13:00, and the daily peak value of the bare land and the removal of soil crusts appeared at about 15:00. The existence of biological soil crusts advanced the daily peak value of soil carbon release rate appear about 2 hours, and the daily peak value of carbon release rate of each observation types all appeared in August. In the relative dry year(2017), the soil carbon emission of covered algae and moss crusts was increased by 22.07% and 85.61%, and the carbon emission of the algae and moss crusts could account for 67.60% and 25.76% of the increased amount. And in the relative wet year(2018), the soil carbon emission of covered algae and moss crusts was increased by 139.37% and 290.53%, and the surface carbon emission of the algae and moss crusts could account for 69.09% and 45.59% of the increased amount. The development of biological soil crusts promoted the carbon release of soil. Temperature was the key driving factor for the diurnal dynamic change of soil carbon release in this area. Temperature drive the contribution rate of soil carbon release reached 48.89%. Therefore, in the process of calculating carbon exchange in desert ecosystems, the effects of different biological soil crusts on soil carbon release should be fully considered.