海岸沙地主要森林的凋落物分解及生态化学计量特征

Characteristics of Litter Decomposition and Ecological Stoichiometry of Different Forests on Coastal Sandy Land in Fujian Province

为探讨不同森林类型对滨海风沙土肥力质量影响的差异及机制,采用分解袋法研究了福建省海岸沙地防护林5种主要森林类型的凋落物生物量动态、分解动态,分析了不同凋落物的初始质量特征,分解过程的失重率、碳氮比、碳磷比、氮磷比特征及分解速率等。结果表明:5种森林类型凋落物生物量为10.08~12.99 t/(hm 2·a),月动态差异不大。不同凋落物的初始质量指标差异显著;5种凋落物分解过程的失重率变化均符合Olson模型规律,预测分解95%需要时长分别为:天然次生林3.31 a,尾巨桉4.92 a,厚荚相思5.38 a,木麻黄8.18 a,湿地松13.80 a。分解指数k与凋落物全磷、全氮含量极显著正相关,与碳氮比、纤维素含量极显著负相关;与土壤pH值、有效磷含量极显著正相关。随着分解时间的延长,5种凋落物的碳氮比均呈指数型下降趋势,碳磷比变化规律各异,氮磷比在分解进程中相对稳定。凋落物分解受凋落物初始质量特征、沙土酸性强、养分贫瘠、干燥度高、风速大等因素的综合影响。在防护林经营过程中,应增加混交树种类型,以丰富凋落物种类,还可考虑通过施肥调节土壤碳氮磷比例、pH值等,以达到调控凋落物分解速率、提高沙土“自肥”能力的目的。

To explore the effect of difference and mechanism of different forests on coastal sandy soil,a decomposition experiment was carried out by using the litterbag method.Litter biomass and decomposition dynamics of five main forest types of shelterbelt on coastal sandy land of Fujian Province were studied.Initial characteristics,weight loss rate,CN ratio,CP ratio and NP ratio during decomposition were analyzed.The results show that litter biomass of different forests ranged from 10.08 t/(hm 2·a)to 12.99 t/(hm 2·a),and monthly dynamics showed slight difference.There were significant differences in the initial quality properties,such as TC,TN,CN ratio,CP ratio,CP ratio,cellulose and lignin contents.Weight loss rate during decomposition period conformed to Olson exponential attenuation model,and the estimated time of decomposition to 95%was 3.31 years for secondary forest,4.92 years for Eucalyptus grandis×E.urophylla plantation,5.38 years for Acacia crassicarpa plantation,8.18 years for Casuarina equisetifolia plantation,and 13.80 years for Pinus elliottii plantation.Decomposition index(k)was positively correlated with the contents of TP and TN of litter,negatively correlated with TC,CN ratio and cellulose content,and also positively correlated with soil pH and AP.With the extension of decomposition time,CN ratio decreased exponentially,while CP ratio showed different tendency,NP ratios were relatively stable.The decomposition of litter was subject to the comprehensive influence of initial quality characteristics of litter,strong acidity of sandy soil,poor nutrition,high dryness,high wind speed and other factors,which could be adjusted by certain forest management,such as planting multiple tree species,fertilizing,as so as to regulate the decomposition rate of litter,improve the ability of self-fertilizing.