干旱区生态环境知识资源中心

Pattern of plant biomass and net primary production was investigated in two localities (Minqin and Linze) of oasis-desert ecotone (ODE) in Northwest China, in order to recognize the spatial and temporal variability of vegetation under same regional climate with different groundwater depth. The average depth to groundwater was over 14.02 m at Minqin - marked further as DG (deep groundwater) and about 4.96 m at Linze - marked further as SG (shallow groundwater).

We have measured plant biomass and net primary productivity (NPP) across species, three times per year for three consecutive years, in six plots along Minqin and Linze oasis-desert ecotone (further marked as DG and SG ODE), respectively. Our results showed that DG and SG ODEs had different growth responses to different groundwater depths. DG ODE exhibited higher inter-annual variation in annual NPP (ranged from 0.18 to 9.30 g m(-2)) than did SG ODE (ranged from 0.42 to 17.99 g m(-2)). Decrease of groundwater depth had apparently altered the seasonality of productivity in DG ODE systems, where precipitation in summer maintained plant growth, while ODE with high groundwater depth tended to have higher spring NPP in SG ODE. Spatial and temporal heterogeneity of NPP at the scale of our measurements was significantly greater in DG ODE than in SG ODE. SG ODE tended to support higher NPP than did DG ODE. In addition, the groundwater depth strongly influenced spatial and temporal heterogeneity of NPP in the desert ecosystems. Clearly, the desert ecosystem with higher groundwater depth is more stable and more resistant to long-term drought or climate shifts in arid regions. These investigations and quantitatively analysis are very significant for the execution of conservation and restoration in arid ecosystems.