Distribution and cycling of elements in a Pinus resinosa plantation ecosystem, Wisconsin

Abstract

Biomass in 34-year-old planted red pine (Pinusresinosa Ait.) on a Typic Udipsamment soil was 127 t ha−1. Aboveground net primary production was 10.2 t ha−1 year−1. Nutrient concentrations in the trees varied by (i) tissue, (ii) position in tree, and (iii) age of foliage. In the aboveground tree concentrations of N, P, K, Mg, and S were greatest in foliage followed by bolebark, live branches, and bolewood. Concentrations of N and S in foliage, bolebark, and live branches and concentrations of K, Mg, and P in the bolebark and live branches increased toward the apex of the tree. Whereas concentrations of Ca, Mg, and S increased with foliar age, concentrations of K and P decreased with foliar age. Total elements in the aboveground and belowground biomass were ranked: N > Ca > K > Mg > S > P. The forest floor contained greater quantities of N (254 kg ha−1) than the vegetation (222 kg ha−1). The upper 100 cm of mineral soil contained from 8.2% (N) to 89% (Mg) of the readily available nutrients in the ecosystem: Atmospheric inputs were the major source of N and S. Output of a given element by leaching beyond the rooting zone (55 cm) was less than 7 kg ha−1 year−1, except for S which was 12 kg ha−1 year−1. Litterfall returned the greatest amounts of each of the elements to the soil surface, followed by throughfall and stemflow. Because of foliar leaching, the net loading of each of the elements exceeded that of the precipitation. With the exception of [Formula: see text], [Formula: see text], and H, loading of elements in the forest floor leachate exceeded that of the throughfall + stemflow. Nitrogen mineralization was estimated to be 44 kg ha−1 year−1. Whereas N, S, and P in the forest floor required approximately 10 years to turn over, Ca, Mg, and K turned over in about 5 years. Mineral weathering provided 22, 6.9, and 5.0 kg ha−1 year−1 of Ca, K, and Mg, respectively. These estimates, determined from the mass balance approach, are considered to be too high. Elements were taken up by the vegetation in the following order: Ca (56 kg ha−1 year−1), N (54), K (18), S (13), and Mg (10 kg ha−1 year−1). Elemental retention, which ranged from 30% for S to 50% for K, was lower than for comparable ecosystems.