Schrodt Franziska, Domingues Tomas F, Feldpausch Ted R, Saiz Gustavo, Quesada Carlos Alberto, Schwarz Michael, Ishida F Yoko, Compaore Halidou, Diallo Adamo, Djagbletey Gloria, Hien Fidele, Sonké Bonaventure, Toedoumg Herman, Zapfack Loius, Hiernaux Pierre, Mougin Eric, Bird Michael I, Grace John, Lewis Simon L, Veenendaal Elmar M, Lloyd Jon
School of Geography, University of Leeds, LS2 9JT, UK.
School of Geosciences, University of Edinburgh, EH8 9XP-, Scotland, UK.
Funct Plant Biol. 2014 Feb;42(1):63-83. doi: 10.1071/FP14040.
Variations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca were determined for 365 trees growing in 23 plots along a West African precipitation gradient ranging from 0.29 to 1.62m a-1. Contrary to previous studies, no marked increase in Ma with declining precipitation was observed, but savanna tree foliar [N] tended to be higher at the drier sites (mass basis). Generally, Ma was slightly higher and [N] slightly lower for forest vs savanna trees with most of this difference attributable to differences in soil chemistry. No systematic variations in [P], [Mg] and [Ca] with precipitation or between trees of forest vs savanna stands were observed. We did, however, find a marked increase in foliar [K] of savanna trees as precipitation declined, with savanna trees also having a significantly lower [K] than those of nearby forest. These differences were not related to differences in soil nutrient status and were accompanied by systematic changes in [C] of opposite sign. We suggest an important but as yet unidentified role for K in the adaption of savanna species to periods of limited water availability; with foliar [K] being also an important factor differentiating tree species adapted to forest vs savanna soils within the 'zone of transition' of Western Africa.
对生长在沿西非降水梯度（从0.29至1.62米/年）的23个样地中的365棵树，测定了单位面积叶质量（Ma）以及叶片中氮、磷、碳、钾、镁和钙的浓度。与之前的研究相反，未观察到随着降水量下降Ma显著增加，但稀树草原树木叶片的[氮]（质量基准）在较干旱地点往往更高。总体而言，森林树木的Ma略高于稀树草原树木，[氮]略低于稀树草原树木，这种差异大部分归因于土壤化学性质的不同。未观察到[磷]、[镁]和[钙]随降水量或森林与稀树草原林分树木之间的系统变化。然而，我们确实发现随着降水量下降，稀树草原树木叶片的[钾]显著增加，稀树草原树木的[钾]也显著低于附近森林树木的[钾]。这些差异与土壤养分状况的差异无关，并且伴随着[碳]的相反符号的系统变化。我们认为钾在稀树草原物种适应水分供应有限时期方面起着重要但尚未确定的作用；叶片[钾]也是区分适应西非“过渡带”内森林与稀树草原土壤的树种的一个重要因素。
