Drivers of Robinia pseudoacacia L. growth during stand development on the Loess Plateau, China

Although climate variables have been shown to strongly affect plantation growth processes, little is known about the roles of tree size and nutrient element in radial growth processes during stand development on the Loess Plateau (LP), China. Total 98 tree-ring cores of Robinia pseudoacacia L. were collected from four stand age-class on LP. We redefined the growth period of R. pseudoacacia based on all combined tree rings and analyzed the influencing factors of each growth period based on the detrending tree ring width chronologies. The effects of climate, tree size, element concentrations, and their interaction effects on tree growth were investigated using linear model and variation partitioning analysis. The results showed that radial growth of R. pseudoacacia was redefined as two growth periods: Decreased Growth Period (1-20 years) and Stable Growth Period (21-40 years). Climate factors mainly controlled tree radial growth in the Stable Growth Period rather than the Decreased Growth Period. The radial growth in the Stable Growth Period was primarily promoted by summer drought, which has 34.1 % of the variables effect percentage. Tree radial growth of R. pseudoacacia in the Decreased Growth Period was mainly promoted by phosphorus (P) concentration, which explained 41.1 % of the variables effect percentage. Contrary to expectations, tree size and the interaction effect of all variables hardly impact on tree radial growth in the two growth periods. Our research illustrated that appropriate nutrient supplementation, such as P elements, occurred during the Decreased Growth Period, followed by thinning practice and tree composition to alleviate climate effects. Overall, our results provide valuable information for formulating appropriate management strategies for R. pseudoacacia plantations on the LP in changing climate.