Intraspecific variations in fine root N and P and factors affecting their concentrations in Masson pine plantations across subtropical China

Fine roots (< 2 mm) play vital roles in water and nutrient uptake. However, intraspecific variations in their chemical traits and their controlling mechanisms remain poorly understood at a regional scale. This study examined these intraspecific variations in fine roots in Masson pine ( Pinus massoniana Lamb.) plantations across subtropical China and their responses to environmental factors. Root nitrogen (N) and phosphorus (P) concentrations and their mass ratios (N:P) ranged from 3.5 to 11.7 g kg −1 , 0.2 to 0.9 g kg −1 , and 7.8 to 51.6 g kg −1 , respectively. These three chemical traits were significantly different between sites and in longitudinal patterns across subtropical China. Mean annual temperature was positively related to root N concentration but negatively related to root P concentration. There were significant, negative relationships between clay content and root P concentration and between pH and root N concentration. Available N had no significant relationship with root N concentration, while available P was a significantly positive relationship with root P concentration. The combined effects of altitude, climate (temperature and precipitation) and soil properties (pH, clay content, available N and P) explained 26% and 36% of the root N and P concentrations variations, respectively. These environmental variables had direct and indirect effects and exhibited disproportionate levels of total effects on root N and P concentrations. Root N and P concentrations explained 35% and 65% variations in their mass ratios, respectively. The results highlight different spatial patterns of chemical traits and various environmental controls on root N and P concentrations in these ecosystems. More cause-effect relationships of root chemical traits with abiotic and biotic factors are needed to understand nutrient uptake strategies and the mechanisms controlling intraspecific variations in plant traits.