Net ecosystem production in the arid land in northwest China from1982 to 2001

摘要

This study constructs a soil respiration model, which includes three variables: air temperature, precipitation and soil character using a semi-mechanistic-empirically statistical model by James W. Raich. The soil characteristics are variables introduced into the model in the study, including soil texture, soil depth, PH and soil organic carbon. Then the model was used to estimate the gross and illustrate spatial-temporal patterns of soil respiration based on the data obtained monthly across the arid land in northwest China from 1961 to 2001. The solar energy efficiency model was used to survey NPP, and the NEP on 20 years scale from 1982 to 2001. Thus, the following conclusions can be come up with: (1) from 1961 to 2001, the temperature and wetness had an increasing trend in the arid land in northwest China, while the range of precipitation variation was greater than before. Such climate change accelerated NPP and soil respiration, and declined NEP on a total level. The carbon sink function of arid land of Northwest China was weakening. (2) Under the background of increasing temperature and wetness, human cultivation accelerated soil respiration of the oasis. Thus, NEP of the oasis was declined. Thereby, the carbon sink function of oasis was weakening and soil degradation happened. 3) Moisture is a more important factor than temperature in the main processes of terrestrial carbon cycle in the arid areas in Northwest China. More attention should be paid to the precipitation in modeling dominant processes of the carbon cycle process in the arid areas.