干旱过程中荒漠生物土壤结皮-土壤系统的硝化作用对温度和湿度的响应——以沙坡头地区为例

以腾格里沙漠东南缘天然植被区由藻类、藓类结皮所覆盖的土壤和流沙为研究对象，采用原状土室内培养法，在15和20 ℃两个温度、10%和25%两个湿度下连续培养20 d，分别在培养后的第1、2、5、8、12、20天连续测定土壤样品中的NO₃^--N含量，探讨不同温度和湿度条件下荒漠土壤的净硝化速率在干旱过程中的变化规律.结果表明： 藓类结皮的NO₃^--N含量（2.29 mg·kg^-1）高于藻类结皮（1.84 mg·kg^-1）和流沙（1.59 mg·kg^-1），3种类型的土壤净硝化速率介于-3.47～2.97 mg·kg^-1·d^-1之间.10%湿度条件下，藻类和藓类结皮在25 ℃下的净硝化速率比15 ℃分别减少75.1%和0.7%；25%湿度条件下，分别减少99.1%和21.3%；15 ℃、10%湿度条件下藻类和藓类结皮的净硝化速率比25 ℃、25%湿度条件下增加193.4%和107.3%.表明在全球变暖背景下，无论土壤湿度增加或减少，干旱过程中的荒漠生物土壤结皮-土壤系统净硝化速率在一定程度上都会受到抑制.

Nitrification of biological soil crusts and soil system during drought process and its response to temperature and moisture: A case study in the Shapotou region,Northwest China.

Two types of soil covered by biological soil crusts (BSCs), i.e. moss and algae, and moving sand in the natural vegetation area at the southeast fringe of the Tengger Desert were collected intactly. They were incubated continuously for 20 days under two different temperatures (15 ℃ and 25 ℃) and moistures (10% and 25%) condition in the laboratory, and soil NO₃^--N contents were measured after 1, 2, 5, 8, 12, 20 days of incubation and net nitrification rate was evaluated during dehydration. The results showed that NO₃^- -N content of the moss covered soil (2.29 mg·kg^-1) was higher than that of the algae covered soil (1.84 mg·kg^-1) and sand (1.59 mg·kg^-1). Net nitrification rate of the three soil types ranged from -3.47 to 2.97 mg·kg^-1·d^-1. For the moss covered soil and algae covered soil at 10% and 25% moisture levels, the net nitrification rates at 15 ℃ were 75.1%, 0.7% and 99.1%, 21.3% higher than those at 25 ℃, respectively. Also, the net nitrification rates at 15 ℃ and 10% moisture levels were 193.4% and 107.3% higher than those at 25 ℃ and 25% moisture levels, respectively. The results suggested that regardless of soil moisture increasing or decreasing under the global warming senior, the net nitrification rate of BSCs soil system in the desert would probably be limited to some extent during drought process.