Spatial-temporal trade-offs of land multi-functionality and function zoning at finer township scale in the middle reaches of the Heihe River

Trade-off occurs when two or more land use functions compete with each other, and high degree of trade-off tends to impede the maximization of land resource utility. Identifying the pattern of trade-offs among multiple land functions is an essential way to achieve sustainable land management. However, effective governance depends heavily on the trade-off information at finer scales which is difficult to acquire due to the challenges in collecting social and economic data at these scales. To overcome this limitation, we developed a framework to reveal the spatio-temporal pattern of land multi-functionality in the middle reaches of the Heihe River in 2006 and 2016 at the township scale by assimilating datasets from multiple sources especially including remote sensing and Internet-based geospatial data. Then we examined the trade-offs and synergy among different land functions by correlation analysis and bivariate spatial autocorrelation analysis. Finally, we conducted land function zoning analysis using the k-means clustering method to get different zones for the purpose of land management. The results showed that land multi-functionality in the middle reaches of the Heihe River showed highly temporal and spatial variations, which was characterized by the strongest economic and social functions around town centers, the strongest environmental functions at the mountainous areas, and the prominent social functions in the ethnic towns. The quantified value of land multi-functionality increased rapidly by 35.0% from 2006 to 2016 with economic, social and environmental function increasing by 61.4%, 47.8% and 6.4% respectively. The trade-offs and synergies among land functions were complex. The synergy between economic function and social function was at a high level and stable, while the trade-off between environmental function and economic function was high but slightly weakened. We identified three hotspots of trade-offs and synergies among multiple land functions, which corresponded to low-intensity development, high-intensity development, and restrictive development for restoration and protection. Based on the trade-offs and synergies among land functions, we classified the study area into four zones, which were useful for land management. Our research highlights the use of Internet-based geospatial and remote sensing data to get fine-scale information about land multi-functionality, and provides scientific guidelines for sustainable land use.