Use of Geographically Weighted Regression (GWR) to Reveal Spatially Varying Relationships between Cd Accumulation and Soil Properties at Field Scale

Coupling coordination and influencing factors of urban spatial accessibility and economic spatial pattern in the New Western Land-Sea Corridor

The construction of the New Western Land-Sea Corridor is crucial to the economic development of western China and even Southeast Asia. Research analyzes the evolution of urban economic spatial pattern of the New Western Land-Sea Corridor in different years and discusses the coordinated development between economic connection and accessibility and its influencing factors. The research results show that: First, the influence of labor force on the urban centrality of the New Western Land-Sea Corridor is gradually increasing, and the spatial pattern of the urban network has gradually shifted from a unipolar attraction type to a spatial pattern of "one main and multiple subordinates." Second, urban accessibility presents a "core-periphery" spatial pattern, and the coupling coordination degree presents the spatial characteristics of "centro-periphery." The economic correlation strength, spatial accessibility, and the coordinated distribution of the two all have obvious spatial agglomeration characteristics. Third, there are spatial differences in the influencing factors of the coupling coordination degree. Based on this, the research puts forward the development mode of "growth pole," "area," and "axis," attaches importance to the problems of labor force in urban development, and strengthens the level of coupling coordination between regional transportation and economy, to promote the integration of regional transportation, logistics, and economy.

A New Sight of Influencing Effects of Major Factors on Cd Transfer from Soil to Wheat (Triticum aestivum L.): Based on Threshold Regression Model

Due to the high toxicity and potential health risk of cadmium (Cd), the influencing effects of major factors (like pH, OM, and clay, etc.) on Cd bioaccumulation and transfer from soil to crop grains are highly concerned. Multiple linear regression models were usually applied in previous literature, but these linear models could not reflect the threshold effects of major factors on Cd transfer under different soil environmental conditions. Soil pH and other factors on Cd transfer in a soil-plant system might pose different or even contrary effects under different soil Cd exposure levels. For this purpose, we try to apply a threshold regression model to analyze the effects of key soil parameters on Cd bioaccumulation and transfer from soil to wheat. The results showed that under different soil pH or Cd levels, several factors, including soil pH, organic matter, exchangeable Cd, clay, P, Zn, and Ca showed obvious threshold effects, and caused different or even contrary impacts on Cd bioaccumulation in wheat grains. Notably, the increase of soil pH inhibited Cd accumulation when pH > 7.98, but had a promotional effect when pH ≤ 7.98. Thus, threshold regression analysis could provide a new insight that can lead to a more integrated understanding of the relevant factors on Cd accumulation and transfer from soil to wheat. In addition, it might give us a new thought on setting regulatory limits on Cd contents in wheat grains, or the inhibitory factors of Cd transfer.