Abstract
Abstract. The response of vegetation systems to the long-term changes in climate, hydrology, and social–economic conditions in river basins is critical for sustainable river basin management. This study aims to investigate the evolution of natural and crop vegetation systems in the Heihe River basin (HRB) over the past 2000 years. Archived Landsat images, historical land use maps and hydrological records were introduced to derive the long-term spatial distribution of natural and crop vegetation and the corresponding biomass levels. The major findings are that (1) both natural and crop vegetation experienced three development stages: a pre-development stage (before the Republic of China), a rapid development stage (Republic of China – 2000), and a post-development stage (after 2000). Climate and hydrological conditions did not show significant impacts over crop vegetation, while streamflow presented synchronous changes with natural vegetation in the first stage. For the second stage, warmer temperature and increasing streamflow were found to be important factors for the increase in both natural and crop vegetation in the middle reaches of the HRB. For the third stage, positive climate and hydrological conditions, together with policy interventions, supported the overall vegetation increase in both the middle and lower HRB; (2) there was a significantly faster increase in crop biomass than that of native vegetation since 1949, which could be explained by the technological development; and (3) the ratio of natural vegetation to crop vegetation decreased from 16 during the Yuan Dynasty to about 2.2 since 2005. This ratio reflects the reaction of land and water development to a changing climate and altering social–economic conditions at the river basin level; therefore, it could be used as an indicator of water and land management at river basins.
Highlights
Natural vegetation plays a key role in maintaining functions of catchment ecosystems, including contributions to goods, services, and ecosystem biodiversity at arid and semiarid river basins (Ahlström et al, 2015; Feng et al, 2013; Kefi et al, 2007)
Since the establishment of the Peoples’ Republic of China (PRC), the crop vegetation has increased at a high rate, especially in the midstream
This paper presented an empirical study of the evolution of vegetation systems in the Heihe River basin (HRB) over the past 2000 years
Summary
Natural vegetation plays a key role in maintaining functions of catchment ecosystems, including contributions to goods, services, and ecosystem biodiversity at arid and semiarid river basins (Ahlström et al, 2015; Feng et al, 2013; Kefi et al, 2007). With the rapid population growth, an increasing amount of water has been allocated worldwide to support human activities, for agricultural irrigation, whereas water for natural vegetation, wetlands, and other catchment ecosystems might have been compromised. An understanding of the development of natural vegetation under different water availability conditions, and its interactions with the human crop system, is vital for sustainable river basin management. There are an overwhelming number of studies on the impact of land use and land cover changes driven by either human activities or climate changes, on the catchment hydrological regime and on the water cycle (Esteban and Albiac, 2011; Ian and Reed, 2012; Leggett et al, 2003; Xue et al, 2015).
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