Effects of grassland cultivation on ecosystem water use efficiency in a grazed temperate grassland area

doi:10.11686/cyxb2019259

Abstract

Abstract: Water use efficiency (WUE) is an indicator of coupling between ecosystem carbon and water cycles, so it is an important reference for the measurement of regional resource transformation efficiency. The purpose of this study was to determine the effects of cultivation on the WUE of a grazed grassland ecosystem. On the basis of the vorticity-related system monitoring data in adjacent grazed and cultivated areas and combined community investigations and sampling measurements, this study analyzed the dynamic difference and effects of two different management patterns on the WUE of the ecosystem (gross primary productivity; GPP) (WUE_GPP). The results indicated that: 1) WUE_GPP reached its peak each year in summer; in June, the daily average WUE_GPP of the cultivated sites (3.61 g C·kg^-1 H₂O) was 58% higher than that of the grazed sites, and the annual WUE_GPP of the former (3.07 g C·kg^-1 H₂O) was 50% higher than that of the latter. 2) The higher WUE_GPP of the cultivated sites was due to the higher GPP during the growing season and lower evapotranspiration (ET) during the non-growing season. 3) The ET explained the change in the WUE_GPP of the grazed sites (26%, P<0.001), while GPP explained the change in WUE_GPP of the cultivated sites (45%, P<0.001) better than did ET. 4) Among the environmental factors, soil moisture had the strongest effect on the change in WUE_GPP and the negative correlation between them was extremely significant both for the cultivated and grazed sites (P<0.001). These results show that different land management practices and utilization types can significantly affect ecosystem WUE on the temperate steppe. Among the various environmental factors, soil water content explained the changes in WUE_GPP at both the grazed and cultivated sites, and so soil water supply may be the most important factor regulating WUE in regional ecosystems. These results provide a useful reference for scientific planning of regional land use and for the reinforcement of more efficient use of key resources in arid areas.

Key words: grassland cultivation, grazing ecosystem, steppe management/use change, temperate steppe, water use efficiency

LI Yu-zhe, SHAO Quan-qin, FAN Jiang-wen, CHEN Yi, CHEN Zhi, GUAN Hui-lin, ZHANG Xin-yuan. Effects of grassland cultivation on ecosystem water use efficiency in a grazed temperate grassland area[J]. Acta Prataculturae Sinica, 2019, 28(10): 110-121.

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