格氏栲天然林与人工林凋落叶分解过程中养分动态

摘要

通过对中亚热带格氏栲天然林 (natural forest of Castanopsis kawakamii, 约150a)、格氏栲和杉木人工林 (monoculture plantations of C. Kawakamii and Cunninghamia lanceolata,33年生) 凋落叶分解过程中养分动态的研究表明,各凋落叶分解过程中N初始浓度均发生不同程度的增加后下降;除格氏栲天然林中其它树种叶和杉木叶P浓度先增加后下降外,其它均随分解过程而下降;除杉木叶外,其它类型凋落叶的Ca和Mg浓度呈上升趋势;凋落叶K浓度均随分解过程不断下降.养分残留率与分解时间之间存在着指数函数关系xt=x0e-kt.凋落叶分解过程中各养分释放常数分别为:N(kN) 0.678～4.088;P (kP) 0.621～4.308;K(kK) 1.408～4.421;Ca (kCa) 0.799～3.756;Mg (kMg) 0.837 ～ 3.894.除杉木叶外,其它凋落叶分解过程中均呈kK>kP>kN>kMg>kCa的顺序变化.各林分凋落叶的年养分释放量分别为N 10.73～48.19kg/(hm2·a),P 0.61～3.70kg/(hm2·a),K 6.66～39.61kg/(hm2·a),Ca 17.90～20.91kg/(hm2·a),Mg 3.21～9.85kg/(hm2·a).与针叶树人工林相比,天然阔叶林凋落叶分解过程中较快的养分释放和较高的养分释放量有利于促进养分再循环,这对地力维持有重要作用.%Nutrient dynamics of decomposing leaf litter was studied in two 33-year-old plantations, Chinese fir (Cunninghamia lanceolata, CF) and Castanopsis kawakamii (CK), and compared with that of an adjacent natural forest of Castanopsis kawakamii (NF, ～150 year old) in Sanming, Fujian, China. During the decomposition, varying degree of initial increase followed by decrease of N concentrations was observed in leaf litter, while initial increase and then decrease of P concentration was only found in leaves of other tree species in the NF and Chinese fir needle. The concentrations of Ca and Mg increased in all leaves except for Chinese fir needle, whereas that of K decreased consistently. Using the model xt=x0e-kt, the decay constants of nutrients ranged from 0.678 to 4.088 for N (kN), from 0.621 to 4.308 for P (kP), from 1.408 to 4.421 for K (kK), from 0.799 to 3.756 for Ca (kCa) and from 0.837 to 3.894 for Mg (kMg) respectively. The decay constants of nutrients during leaf-litter decomposition can be arranged in the sequence of kK>kP>kN>kMg>kCa, except for leaf litter of Chinese fir where kK>kMg>kCa>kN>kP. Annual nutrient release from decaying leaf litters in the three forests was N, 10.73～48.19 kg/(hm2·a); P, 0.61～3.70 kg/(hm2·a); K, 6.66～39.61 kg/(hm2·a); Ca, 17.90～20.91 kg/(hm2·a) and Mg, 3.21～9.85 kg/(hm2·a) respectively. It was concluded that faster nutrient release of leaf litter and its greater amount in the natural broadleaved forest were beneficial to nutrient recycling and soil fertility maintenance than monoculture coniferous plantations.