Spatial heterogeneity and driving factors of land use change in the middle and upper reaches of Ganjiang River, southern China

The middle and upper reaches of Ganjiang River is an important functional area for soil and water conservation in the southeastern hills of China. It is important to analyze the land use change and their driving forces at different spatial and temporal scales to maintain and optimize the local ecological functions. We analyzed the land use structure and land use dynamics in the middle and upper reaches of Ganjiang River from 1980-2018 based on 1 km spatial resolution land use data, and analyzed the spatial heterogeneity and driving factors of land use change using principal component analysis (PCA), ordinary least squares (OLS) and geographically weighted regression (GWR). From 1980-2018, the main land use types in the study area were forests (proportion 69.4%-71%) and cultivated land (proportion 20.8%-20.9%). Land use dynamic degree of build-up land and unused land were larger, and the comprehensive land use dynamic degree gradually increased, especially in 2010-2018. The GWR model had a better fitting effect on the analysis of land use change drivers, which was better in 98.6% of the area. Among the influencing factors of the spatial heterogeneity of land use change in the study area, the natural environment factors were the most obvious, with a restrictive role. The socio-economic factors were the secondary in importance, with a promoting role. The comprehensive influence of natural and social factors were weak and complex.

[Evaluation of comprehensive potential productivity and resource utilization efficiency of Camellia oleifera in Jiangxi Province, China]

As an area suitable for the plantation of Camellia oleifera, Jiangxi had a low degree of development and utilization. Evaluating its potential productivity and resource utilization efficiency could provide reference for optimizing C. oleifera planting division, increasing yield and rationally utilizing land resources. Natural production potential of C. oleifera in Jiangxi was estimated by stepwise revised potential attenuation method. The comprehensive potential productivity was estimated by combined with social efficiency coefficient, with the resource utilization efficiency being evaluated. There were three main results. 1) Potential productivity of C. oleifera in Jiangxi varied from 10229 to 17724 kg·km^-2, which decreased from the south to the northwest, with an average potential of 12550 kg·km^-2. After classification, the area with higher and highest potential productivity reached 51656 km², accounting for 31.1% of the total area. Among the cities, Ganzhou had the highest potential productivity. 2) The changes of potential productivity of C. oleifera ranged from 2223 to 3857 kg·km^-2, with small regional difference for various levels. The resource satisfaction rate ranged from 69.3% to 122.7%, with small regional difference. The resource utilization efficiency varied from 49.1% to 85%. Regional utilization rate at all levels differed obviously. 3) The estimated comprehensive potential productivity was in line with the real production of C. oleifera in Jiangxi, and the assessed resource utilization efficiency was consistent with natural and social conditions. These results could be used as a reference for related research and policy making.