Zhang Peng, Li Xin-Rong, Zhang Zhi-Shan, Pan Yan-Xia, Liu Yan-Mei, Su Jie-Qiong
Shapotou Desert Experimental Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou 730000, China.
Ying Yong Sheng Tai Xue Bao. 2012 Aug;23(8):2157-64.
Taking three typical types of biological soil crusts (BSCs), i.e., cyanobacterial-algal crust, lichen crust, and moss crust, in the southeast fringe of Tengger Desert as test objects, this paper studied their nitrogen fixation potential, seasonal fluctuation, and responses to the environmental factors from June 2010 to May 2011. During the whole study period, the nitrogenase activity (NA) of the cyanobacterial-algal, lichen, and moss crusts had significant difference, being 14-133, 20-101, and 4-28 micromol x m(-2) x h(-1), respectively, which indicated the critical role of the species composition of BSCs in nitrogen fixation. The NA of the three crust types had similar response characteristics to environmental factors. The NA had less correlation with the precipitation during the study period, but was positively correlated to the < 3 mm precipitation in the former 3 days of the experiment, indicating that the three types of BSCs could reach the maximum rate of nitrogen fixation under 3 mm precipitation. The NA of the three crust types had a significant quadratic functional relationship with air temperature, i.e., decreased after an initial increase. The NA of cyanobacterial-algal and lichen crusts declined rapidly when the temperature exceeded 30 degrees C, while the NA of moss crust began to decline when the temperature exceeded 25 degrees C, suggesting that different types of BSCs had different optimal temperature range of nitrogen fixation. The seasonal change of the NA of the three crust types was in the order of autumn > spring > summer > winter. The high air temperature in summer and the low air temperature (< 0 degrees C) in winter inhibited the NA of the crusts, while the suitable water and heat conditions in late spring and early autumn promoted the NA, which implied that the seasonal fluctuation of the NA was mainly controlled by the joint effect of the water and heat conditions. Under humid condition, the BSCs in the temperate desert zone had nitrogen fixation capacity throughout the year, and the controlling effects of environmental factors on the nitrogen fixation were hierarchical. Water condition was the key factor affecting the nitrogen fixation rate and duration of the crusts, while under the conditions of sufficient water supply and carbon storage, heat condition dominated the crusts nitrogen fixation rate.
本文以腾格里沙漠东南边缘的三种典型生物土壤结皮（BSCs），即蓝藻-藻类结皮、地衣结皮和苔藓结皮为研究对象，研究了它们在2010年6月至2011年5月期间的固氮潜力、季节波动以及对环境因子的响应。在整个研究期间，蓝藻-藻类、地衣和苔藓结皮的固氮酶活性（NA）存在显著差异，分别为14 - 133、20 - 101和4 - 28微摩尔·米⁻²·小时⁻¹，这表明生物土壤结皮的物种组成在固氮过程中起着关键作用。三种结皮类型的NA对环境因子具有相似的响应特征。研究期间，NA与降水量的相关性较小，但与实验前3天内小于3毫米的降水量呈正相关，这表明三种类型的生物土壤结皮在3毫米降水量下可达到最大固氮率。三种结皮类型的NA与气温呈显著的二次函数关系，即先升高后降低。当温度超过30℃时，蓝藻-藻类和地衣结皮的NA迅速下降，而当温度超过25℃时，苔藓结皮的NA开始下降，这表明不同类型的生物土壤结皮具有不同的固氮最佳温度范围。三种结皮类型的NA季节变化顺序为秋季＞春季＞夏季＞冬季。夏季的高温和冬季的低温（＜0℃）抑制了结皮的NA，而晚春和初秋适宜的水热条件促进了NA，这意味着NA的季节波动主要受水热条件的共同影响。在湿润条件下，温带沙漠区的生物土壤结皮全年都有固氮能力，环境因子对固氮的控制作用具有层次性。水分条件是影响结皮固氮速率和持续时间的关键因素，而在水分供应充足和碳储存充足的条件下，热量条件主导了结皮的固氮速率。
