title: [Diurnal and Seasonal Dynamic Variation of Soil Respiration and Its Influencing Factors of Different Fenced Enclosure Years in Desert Steppec].
abstract: 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 Rs rate and environmental factors in the growing season of fenced enclosure 11a, 7a and no fenced (CK) desert steppe in Ningxia. The results showed that: (1) Both the diurnal andseasonal variations of Rs rate 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 Rs rate 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 Rs rate occurred in August with suitable precipitation and temperature conditions. And the Rs rate of the growing season of different fenced enclosure years was in the order of 11a [0.143 g · (m² · h)⁻¹] > 7a [0.138 g · (m² · h)⁻¹] > CK [0.106 g · (m2 - h)⁻¹]. (2) According to statistical analysis, it indicated that R² rate 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 Rs rate and temperature was shown as soil surface temperature (R²: 0.408-0.413) > air temperature (R2: 0.355-0.376) > 5-20 cm soil temperature (R2: 0.263-0.394). The temperature sensitivity coefficient Q, increased gradually with the soil depth, and Q1, of different fenced enclosure years was showed as 11 a (2.728) > 7a (2.436) > CK (2.086). (3) A significant quadratic function model (P < 0.05) was observed for the relationship between Rs rate and relative air humidity, soil moisture content of fenced enclosure 11a, 7a and CK desert steppe in the whole growing season. Rs rate had a significant linear negative correlation with air carbon dioxide concentration (P < 0.01), a linear positive correlation with the windspeed (P < 0.05), and a significant weak linear positive correlation with light intensity (P < 0.01). (4) It showed that Rs increasedwith 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 desert 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.
authors.forename: Hai
authors.initials: H
authors.lastname: Cui
authors.forename: Ya-hong
authors.initials: YH
authors.lastname: Zhang
mesh_terms: D002244:Carbon / Q000032:analysis; D057486:Carbon Cycle; D002681:China; D002980:Climate; D052918:Environmental Restoration and Remediation; D065948:Grassland; D006109:Poaceae / Q000254:growth & development; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D013696:Temperature
chemical_list: D012987:Soil; D002244:Carbon