猫儿山自然保护区沿海拔分布植被带土壤硝化-反硝化和呼吸作用分析

Soil nitrification denitrification respiration and their influence factor analysis in different vegetation zones along elevationnal gradient in Mao’er Mountain of China

【目的】揭示环境因子对猫儿山自然保护区不同海拔植被带土壤呼吸和硝化-反硝化作用的影响。【方法】以广西猫儿山自然保护区不同植被带为研究对象,应用气压过程分离系统BaPS(barometric process separation system)研究了不同海拔植被带的土壤呼吸速率(SRR,soil respiration rate)、总硝化速率(GNR,gross nitrification rate)、反硝化速率(DR,denitrification rate),及其对土壤温度等环境因子的响应规律。【结果】在自然土壤温度下,土壤呼吸速率杉木人工林(Chinese fir plantation,CFP)>常绿、落叶阔叶混交林(evergreen and deciduous broad-leaved forest,EDBF)>毛竹人工林(bamboo plantation,BP)>山顶灌丛(mountaintop shrub,MS)>南方铁杉林(southern hemlock forest,SHF)>水青冈天然林(beech natural forest,BNF),CFP最高为361.6μg/(kg·h);总硝化速率SHF最高为275.3μg/(kg·h),BP最低为58.3μg/(kg·h);反硝化速率为BP>CFP>EDBF>BNF>SHF>MS,BP最高为172.2μg/(kg·h)。土壤温度在5~20℃变化时,6种植被带的土壤呼吸速率、总硝化速率、反硝化速率均随着温度的上升而增加。相关性分析表明,海拔、土壤温度、含水量、pH、有机质、全氮、全钾、速效氮磷钾是影响土壤硝化-反硝化和呼吸作用的重要因子。【结论】低海拔人工林在自然温度下具有比高海拔天然林更高的土壤呼吸速率和反硝化速率,但是高海拔植被带土壤硝化-反硝化和呼吸作用对温度变化具有更高的敏感性,在气候变暖过程中,高海拔植被带土壤可能会释放更多的温室气体增量。

【Objective】To study the effects of soil respiration,nitrification,and denitrification and the influence of various environmental factors in vegetation zones at different altitudes in the Mao'er Mountain.【Method】Different forest types at a National Nature Reserve in Mao'er Mmountain were the experimental sites.Soil respiration rate(SRR),gross nitrification rate(GNR)and denitrification rate(DR)in different vegetation zones at different altitudes were investigated based on the Barometric Process Separation system,and the response of SRR,GNR or DR to soil temperature and other environmental factors was studied.【Result】Under normal temperature,the SRR was in the order of Chinese fir plantation(CFP)>evergreen and deciduous broad-leaved forest(EDBF)>bamboo plantation(BP)>mountaintop shrub(MS)>(Southern hemlock forest(SHF)>Beech natural forest(BNF),and the highest rate was 361.6μg/(kg·h)at CPF.The GNR in the SHF was 275.3μg/(kg·h),and the lowest GNR was 58.3μg/(kg·h)in the BP.In addition,the DRs were in the order BP>CFP>EDBF>BNF>SHF>MS,and the highest was 172.2μg/(kg·h)at BP.SRR,GNR and DR in the six vegetation zones increased with an increase of temperature when the temperature was between 5℃ and 20℃.Correlation analysis results revealed that altitude,soil temperature,water content,pH,organic matter concentration,total nitrogen,total potassium,available N,available P and available K were the key factors influencing SRR,GNR and DR.【Conclusion】Low altitude plantations had higher SRRs and DRs than high altitude natural forests.However,soil nitrification,denitrification and respiration were more sensitive to temperature changes in high altitude vegetation.In the wake of climate change and the ensuing warming,soils in high altitude vegetation zones could release higher amounts of greenhouse gases.