南京近郊人工林地表枯落物的累积量及持水性

Water-holding characteristics and accumulation of litter in different man-made forests in the suburb of Nanjing

通过外业调查,结合实验室分析法对南京近郊8种人工林地表枯落物累积量及持水性进行研究。结果表明:森林枯落物特性受林分组成的影响大,不同群落枯落物厚度、累积量呈现显著差异(P<0.05)。枯落物厚度变化区间为2.10~5.24 cm,大小顺序依次为香樟林(Ⅰ)、乐昌含笑林(Ⅱ)、女贞林(Ⅲ)、马褂木林(Ⅳ)、淡竹林(Ⅷ)、朴树林(Ⅴ)、榉树林(Ⅶ)、槭树林(Ⅵ),总累积量也呈现类似的变化趋势。相关分析表明:1)枯落物累积量(M)和其厚度(d)存在显著的正相关关系,其线性方程为M=1.405 4d+0.665 4(R^2=0.823 4,P<0.05)。2)不同群落枯落物的持水量随浸水时间的变化动态一致,即随着浸水时间的延长,持水量依次增加,并呈现出倒"J"型曲线,持水量(W)与浸泡时间(t)的拟合方程为W=alnt+b。不同群落枯落物吸水速率(v)呈现出"L"型递减变化,即随着浸水时间(t)的延长,吸水速率(v)依次减小,并符合如下关系式:v=at^b。3)榉树林(Ⅶ)、槭树林(Ⅵ)、朴树林(Ⅴ)3种人工林群落的持水能力较高,其最大持水率(R_(max))均值分别为667.56%、462.90%、341.18%;相对的,马褂木林(Ⅳ)、香樟林群落(Ⅰ)群落的持水能力较低,其R_(max)均值分别为191.38%、271.99%;其余几种群落的R_(max)均值中等。4)比较不同群落的有效拦蓄量(W_(SV))以榉树林群落(Ⅶ)最大,达26.32 t/hm^2;槭树林(Ⅵ)、女贞林(Ⅲ)群落的W_(SV)较大,分别为16.64 t/hm^2、16.44 t/hm^2;马褂木群落(Ⅳ)的W_(SV)较小,仅为9.55 t/hm^2。不同人工林群落水分拦蓄能力有明显差别,城市人工林建设中树种组成及群落类型的选择对成林后林地的持水拦蓄和水源涵养能力有重要影响。榉树林表现为较强的水分拦蓄能力,是当前南京城市森林建设较为合理的发展方向。

[Background] Many researchers have studied natural forest litter and obtained a lot of achievements. The litter plays a major role in forest soil and water conservation,this is beyond doubt.However,it is lack of study on the litter characteristics of man-made forests,especially in the suburbs of cities. [Methods]Water-holding characteristics and accumulated amount of litter in 8 species city manmade forests was studied in the suburb of Nanjing. Litter thickness（ d） and accumulation（ M） of litterwere measured by sampling,natural water content（ R0）,water holding rate（ Rt）,maximum water holding rate（ Rmax） and water absorption rate（ V） were analyzed in laboratory,maximum retain rate（ R拦）,maximum retain capacity（ W拦） were calculated and effective retain deepness was calculated.[Results]1） The effect of forest composition on litter characteristics was significant,litter thickness and accumulated amount showed significant difference in different communities（ P 〈 0. 05）. 2） The change of litter thickness ranged from 2. 10 to 5. 24 cm, the descending order of litter thickness was as Cinnamomum camphora forest（ Ⅰ）,Michelia chapensis forest（ Ⅱ）,Ligustrum lucidum forest（ Ⅲ）,Liriodendron chinense forest（ Ⅳ）,Phyllostachys glauca forest（ Ⅷ）,Celtis sinensis forest（ Ⅴ）,Zelkova serrata forest（ Ⅶ）,Acer palmatum forest（ Ⅵ）,and the change of accumulated amount was the similar.The correlation analysis showed it was positive between litter accumulation（ M） and its thickness（ N）,the linear equation was M = 1. 405 4 d ＋ 0. 665 4（ R2= 0. 823 4,P 〈 0. 05）. The change of water-holding capacity of litter in different forests was consistent,i. e.,the water-holding capacity（ W） increased sequentially with the increase of immersion time（ t）,and showing as an inverted ＂J ＂curve with the equation W = alnt ＋ b. The water absorption rate of all litter showed another change,that was,the water absorption rate decreased successively with the increase of immersion time,showing as a ＂L ＂curve and the equation was fitted as v = atb. 3） The Rmaxof the 8 plantations were 667. 56%（ Ⅶ）,462. 90%（ Ⅵ）,341. 18%（ Ⅴ）,292. 19%（ Ⅱ）,298. 01%（ Ⅲ）,290. 76%（ Ⅷ）,191. 38%（ Ⅳ）,and 271. 99%（ Ⅰ）. 4） The water-holding capacity of litter varied among different forests types,Z. serrata forest（ Ⅶ）was the strongest by by comparing the Wsv,which was 26. 32 t/hm^2,A. palmatum forest（ Ⅵ）,and L.lucidum forest（ Ⅲ） were more strong,that of which were 16. 64 t/hm^2,16. 44 t/hm^2. The Wsvof the L.chinense forest（ Ⅳ） was only 9. 55 t/hm^2,which was the weakest on the effective retain deepness.[Conclusions]The water-holding capacity of different plantation communities was significantly different,and the selection of tree species and community types in urban plantation construction had an important effect on the water-holding capacity and water conservation ability of forest land. Cultivating Z. elkova forest is more reasonable development direction of urban forest construction in Nanjing at present because of its strong ability of the effective retain deepness to water and soil.