陆地森林土壤是重要的大气甲烷(CH4)汇,大气氮(N)沉降增加对森林土壤CH4吸收速率影响突出。运用静态箱-气相色谱法对中亚热带天然林土壤CH4吸收速率对模拟N沉降的响应进行连续3a的观测;试验作3种N处理,分别为对照(CK,0 kg N·hm-2·a-1)、低氮(LN,50 kg N·hm-2·a-1)和高氮(HN,100 kg N·hm-2·a-1),每种处理重复3次,每个月采集气体1次,同时测定0—5 cm土壤温度和0—12 cm土壤含水量;分析不同N沉降水平土壤CH4吸收速率的差异、动态变化以及对土壤含水量和土壤温度响应,并探讨N沉降对土壤理化性质的影响。结果显示:天然林土壤(CK)平均CH4吸收速率为(-62.78±14.39)μg·m-2·h-1,LN和HN土壤平均CH4吸收速率分别下降了30.21%、7.24%,CK、LN和HN处理土壤CH4吸收速率季节变化趋势相似;观测期间土壤CH4吸收速率对LN响应达到显著水平(P<0.05),对HN响应则不显著(P>0.05);LN、HN处理前两年对土壤CH4吸收速率抑制作用均不显著(P>0.05),但在第3年LN极显著降低了土壤CH4吸收速率(P<0.01),HN处理对土壤CH4吸收速率的影响则在第3年表现为显著抑制作用(P<0.05),表明土壤CH4吸收速率对N沉降的响应随着N沉降时间的持续呈抑制效应加剧的趋势。相关分析表明:CK与HN土壤CH4吸收速率与土壤温度和土壤含水量均有显著相关性(P<0.05),但LN土壤CH4吸收速率仅与土壤含水量显著相关(P<0.05),表明土壤含水量是控制各N沉降处理土壤CH4吸收速率动态的主要环境因子。此外,LN、HN处理下土壤pH均极显著降低(P<0.01),但LN土壤pH极显著低于HN(P<0.01);LN处理极显著提高了土壤C/N比(P<0.01),HN处理则相反;LN和HN处理对土壤NH+4-N、NO-3-N、可溶性总N(TDN)、可溶性有机碳(DOC)、地面凋落物量、地下0—10 cm细根生物量影响均不显著(P>0.05),表明一定时期内N沉降首先引起了土壤pH和土壤C/N比的显著变化。
Understanding the spatial interactions among multiple ecosystem services is crucial for ecosystem services management. Ecosystem services, including crop production, freshwater supply, aquatic production, net primary production, soil conservation, water conservation, flood regulation, forest recreation, were measured at 1-km grid scale covering the Taihu Lake Basin(TLB) of China. Our objective is to get a comprehensive understanding of the spatial distributions, trade-offs, synergies of multiple ecosystem services across the TLB. Our results found that: 1) majority of ecosystem services were clustered in space and had a similar spatial distribution pattern with the geographical resource endowment. Most of the landscape contributed a high supply of no services, one or two, and a low supply of three to seven services. 2) There were high correlation between forest recreation and freshwater supply and regulating services. Aquatic production had low correlation with other services. 3) The changes of provisioning services led to trade-offs between regulating services and cultural services in the TLB, while synergies mainly occurred among the provisioning service. 4) The spatial relationships of multiple services are consistent at 1-km spatial scale, counties and provinces. This research could help integrate multiple ecosystem services across scales and serve as a reference for decision making.
