Evolution of the vegetation system in the Heihe River basin in the last 2000 years

Abstract

Abstract. The response of vegetation systems to the longterm 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.

Cultivated oasis evolution in the Heihe River Basin over the past 2,000 years

“…The reconstruction method Xie introduced has been adopted in many studies for other regions and is considered to be more reliable (Yuan, Ye, & Fang, ; Yuan, Ye, Li, Wei, & Fang, ). The long‐term cultivated oasis series Xie reconstructed has been widely used for examining historical agricultural activities and hydrological processes in the HRB (Hu & Li, ; Li, Zhao, Wei, & Zheng, ; Lu et al, ). Thus, we used Xie's results to present cultivated oasis evolution during the study period.…”

Alignment of social and ecological structures increased the ability of river management

“…To test the alignment framework, we analyzed data from a large river basin. The Heihe River Basin (HRB) is the second-largest endorheic (closed or inward flowing) basin in the arid region of northwestern China, with a total area of approximately 143 Â 10 3 km 2 [17]. Its special geomorphic structure determines the hydrologic characteristics of the basin [18].…”