不同封育年限荒漠草原土壤呼吸日、季动态变化及其影响因子

Diurnal and Seasonal Dynamic Variation of Soil Respiration and Its Influencing Factors of Different Fenced Enclosure Years in Desert Steppec

围封禁牧措施可以改善退化草地生态环境,是我国退化草地植被恢复的主要措施.为探讨干旱区荒漠草原不同围封禁牧年限的土壤呼吸作用特征及影响因子,在生长季连续观测围封禁牧11a、7a、放牧不封育（CK）荒漠草原土壤呼吸速率及环境因子,结果表明：①在日、季尺度上,封育11a、7a和CK荒漠草原土壤呼吸速率均具有明显的单峰曲线变化规律,在日尺度上,最大、最小值分别出现在12：00-16：00和00：00-06：00;在季节变化尺度上,最大值出现在降水较多温度适宜的8月,土壤呼吸均值表现为11 a[0.143 g·（m^2·h）^-1]〉7a[0.138 g·（m^2·h）^-1]〉CK[0.106 g·（m^2·h）^-1].②封育与未封育荒漠草原的土壤呼吸速率与空气、土壤温度均呈极显著的指数关系（P〈0.001）,相关性大小为：地表温度（R^2：0.408-0.413）〉空气温度（R^2：0.355-0.376）〉5-20 cm土壤温度（R^2：0.263-0.394）;温度敏感性系数Q10随着土层的加深逐渐变大,不同封育年限Q10表现为11a（2.728）〉7a（2.436）〉CK（2.086）.③封育11a、7a和CK荒漠草原土壤呼吸速率与空气湿度、土壤含水量一元二次模型达到显著水平（P〈0.05）,与空气二氧化碳呈极显著线性负相关（P〈0.01）,与风速呈显著线性正相关（P〈0.05）,与光照强度呈极显著线性正相关（P〈0.01）.④干旱区荒漠草原土壤呼吸作用随着围封禁牧年限的增加而增加,温度敏感性系数亦随之增加,0-20 cm土壤温度和水分是其土壤呼吸的主要影响因子.

The fenced measures could improve the ecological environment of degraded grassland,it＇s a main measure for restoration of degraded grassland vegetation in China. Soil respiration（ Rs） is an important component of an ecosystem＇s carbon cycle and the main pathway for carbon moving from the ecosystem to the atmosphere. In order to explore soil respiration characteristics and influencing factors of the different fenced years in arid desert grassland,we continuously observed Rsrate and environmental factors in the growing season of fenced enclosure 11 a,7 a and no fenced（ CK） desert steppe in Ningxia. The results showed that： ① Both the diurnal and seasonal variations of Rsrate showed a single asymmetric peak changing in fenced enclosure of 11 years,7 years,CK desert steppe. On the daily scale,the maximum and minimum values of Rsrate were found in the periods of 12： 00-16： 00 and 00： 00-06： 00,respectively. On the seasonal variation scale,the maximum value of Rsrate occurred in August with suitable precipitation and temperature conditions. And the Rsrate of the growing season of different fenced enclosure years was in the order of 11 a[0. 143g·（m^2·h）^-1] 〉7 a [0. 138 g·（m^2·h）^-1] 〉CK[0. 106 g·（m^2·h）^-1].② According to statistical analysis,it indicated that Rsrate had a significant exponential positive relationship with air and soil temperature in fenced enclosure of 11 years,7 years,CK desert steppe（ P〈0. 01）. The order of the correlation of Rsrate and temperature was shown as soil surface temperature（ R^2： 0. 408-0. 413） air temperature（ R^2： 0. 355-0. 376） 〉5-20 cm soil temperature（ R^2： 0. 263-0. 394）. The temperature sensitivity coefficient Q10 increased gradually with the soil depth,and Q10 of different fenced enclosure years was showed as 11 a（ 2. 728） 〉7 a（ 2. 436） 〉CK（ 2. 086）.③A significant quadratic function model（ P〈0. 05） was observed for the relationship between Rsrate and relative air humidity,soil moisture content of fenced enclosure 11 a,7 a and CK desert steppe in the whole growing season. Rsrate had a significant linear negative correlation with air carbon dioxide concentration（ P〈0. 01）,a linear positive correlation with the wind speed（ P〈0. 05）,and a significant weak linear positive correlation with light intensity（ P〈0. 01）. ④It showed that Rsincreased with increasing fenced closure years in arid desert steppe,and temperature sensitivity coefficient Q10 also increased with increasing fenced enclosure years. To sum up,0-20 cm soil temperature and moisture were the main influencing factors of soil respiration of ariddesert steppe. This study has important implications to understand the role that different fenced enclosure years play in carbon emission. Such information will lay a foundation for assessing carbon source or carbon sequestration of different fenced enclosure years in desert steppe. Therefore,our research results have important function for better managing grassland in desert steppe in Ningxia and other arid and semiarid areas of North China.