Research progress in the impact of land use on water nutrients

Increasingly severe water pollution is a threat to human health and survival, and eutrophication is one of the main challenges faced by pollution governance. Because land use is closely related to water nutrients, quantifying the relationship would be an effective way to support the optimization of land use to improve water quality. Based on international and domestic researches, this study reviewed four methods, e.g., plot experiments, statistical analysis, empirical models, and mechanism models, for studying the effects of land use on water nutrients. The advantages and disadvantages of the application of each method were examined. Until now, studies have been conducted mainly to characterize the quantitative structures of land use. However, there is a limitation in the quantification of the intensity and spatial distribution of land use, and a model of the relationship between land use information and water nutrients is lacking. Research progress has found that multiple land use information was loosely studied from an individual or a partial perspective. This easily led to a significant difference in the explanatory power of land use on water nutrients in different case studies. Thus, research progress was particularly summarized on how three aspects of land use information (land use type, use intensity, and spatial distribution) influence water nutrients. The controversy and uncertainty about the scale effect of the quantitative relationship between land use and water eutrophication have been discussed. The main shortcomings of recent studies were concluded, which included the inadequate capability of approaches for correlating land use to water nutrients, unclear mechanism underlying multiple land use information related to water nutrients, and uncertainty about the abovementioned scale effect. To resolve these issues, this study proposed a breakthrough framework of comprehensive expression and quantification of multiple land use information space that was based on the ecohydrological processes affecting the export, migration, and transformation of water nutrients. Using this proposed multiple land use information space, future studies could focus on integrating process mechanism and empirical statistical methods, comprehensively quantifying multiple land use indicators related to eutrophication, and constructing multiscale structures of land use affecting water nutrients. This study can provide a guide for deep investigation of the relationship between land use and water nutrients.