Interactive effects of hydrological conditions on soil respiration in China's Horqin sandy land: An example of dune-meadow cascade ecosystem

摘要

Soil moisture (M-s) strongly influences dynamic changes in soil respiration (R-s) and is thus an important factor when predicting soil carbon emissions. However, the various sources of M-s (rainfall, groundwater, and condensation) exert complicated and uncertain effects on R-s This study examined the growth seasonal variation (from April to October) of R-s and the diurnal variation in a cascade ecosystem consisting of sandy bare ground, a transitional artificial Populus forest, and a meadow Phragmites communis community in China's Horqin sandy land. Simultaneous measurements of the 0-10 cm depth soil temperature (T-s) and M-s , rainfall, the surface air relative humidity and the groundwater depth were collected. The results revealed that in sandy bare ground with M-s below field capacity, M-s had a greater impact on R-s than T-s, and rainfall could increase R-s The effect of condensation on it R-s during periods of continuous drought could not be ignored. In the meadowlands with M-s above field capacity, the groundwater affected R-s indirectly by regulating M-s and the relationship with T-s, and rainfall had an adverse effect on R-s. The effects of rainfall. M-s and T-s on R-s were minimum as M-s approached the saturation water content In the transitional forest, M-s and T-s were the main factors controlling R-s. The most favorable M-s for it R-s was close to the field capacity. The results emphasize that field capacity and saturation water content are the demarcation points of a soil carbon emissions prediction model, and the effect of different hydrological conditions and T-s on R-s at each segment are reconsidered accordingly. Ultimately, the carbon emission patterns of the cascade ecosystems in arid and semi-arid areas are extremely complicated and have to be considered specially for estimating terrestrial carbon emissions. (C) 2018 Elsevier B.V. All rights reserved.