Nutrient utilization strategies and age-related changes in Larix principis-rupprechtii forests

Aims Investigations into the nutrient contents and changes in the stoichiometry and nutrient resorption strategies of different original forests during their development are of great significance toward the establishment of healthy, high-quality forest ecosystems. Methods A total of 24 sample plots with age gradients were established in natural Larix principis-rupprechtii forests and plantations, from which mature and senescent leaves, new branches, fine roots, and soil were collected and analyzed. The carbon (C), nitrogen (N), and phosphorus (P) contents were determined, and the stoichiometric ratios and resorption efficiencies were calculated. Results and conclusions The soil organic carbon and total nitrogen of the forests accumulated with advancing age, whereas the total phosphorus decreased because of higher consumption. Plantation trees tended to reduce the storage of nutrients in inactive plant structures to prevent nutrient loss, whereas natural forest trees maintained a stable nutrient concentration within their active organs. Plantation and natural forest trees adopted highly conservative N and P utilization strategies through improved resorption efficiencies. However, plantation forests were more conservative than their natural counterparts. The mature leaves, litter, branches, and fine roots of natural forests were influenced to a greater degree by the soil P, whereas those of plantation forests were more affected by the soil N. Nutrient concentrations within the active organs of plantation trees were more strongly dependent on soil than natural forests. We considered that natural forests likely possessed a more extensive range of strategies to deal with the variable compositions and concentrations of soil nutrients, which might strengthen their resilience against the effects of aging.