Litter fall, decomposition and nutrient release in three semi-arid forests of the Duero basin, Spain

Abstract

Summary The production of litter, the weight loss dynamic of forest litter decomposition, and the dynamics of bioelement loss during leaf litter decomposition were determined in three forest ecosystems located in a semi-arid zone of the Duero basin, Province of Zamora, Spain, over 2 years. The three ecosystems were a climax evergreen oak (Quercus rotundifolia Lam.) woodland, a paraclimax stone pine (Pinus pinea L.) forest, and a disclimax maritime pine (Pinus pinaster Sol.) forest. The mean total production of litter in the oak forest was 2320 kg ha ‐1 year ‐1 , quite similar to the P. pinea pine forest, at 2400 kg ha ‐1 year ‐1 and higher than that of the P. pinaster pine forest at 1728 kg ha ‐1 year ‐1 . Leaves and needles accounted for most of this total production (78, 89 and 96 per cent, respectively). No significant differences were found among the different leaf decomposition processes, except for the oak leaves introduced in the pine ecosystems. A relationship between time (independent variable) and the remaining leaf weight was found, which followed a negative exponential curve, DM (dry matter) = A + B exp(‐Ct). About 30 per cent of the weight was lost during the first 4 months. This indicates that climate (semi-arid conditions) speeds decomposition in the short term. The decomposition indices were determined for leaves only and for total litter. Considering total litter and leaves separately, several relations were established for K, Ko and Kd decomposition indices. K and Ko in natural conditions decrease in the following order: evergreen oak > stone pine > maritime pine. The Q. rotundifolia woodland potentially returns a greater amount of N and Ca than both Pinus forests. A litter-bag method was used for the determination of the dynamics of the decomposing leaves. A progressive loss of P and Mg in the decomposing oak leaves and pine needles, and a sharp loss of K were observed: in contrast, a tendency to retain N and Ca was also seen. Pinus pinaster forest had the lowest annual N and P returns.