黄土台塬不同土地利用方式土壤CH_4通量特征及主控因子分析

CH_4 flux characteristics and influencing factors in six land use patterns in the Loess Plateau

土地利用转变会导致土壤微环境及生理生化过程发生改变,继而影响土壤温室气体的产生和排放。目前关于土地利用转变对温室气体通量的研究主要集中于CO_2,而对CH_4研究甚少。本文以黄土台塬为研究区,重点分析不同土地利用方式的土壤CH_4通量特征与其影响因素的关系,并明确其关键影响因子,为预测整个黄土台塬土地利用方式转变对温室效应的贡献提供基础数据。以陕西省永寿县马莲滩林场为研究对象,于2015年4月—2016年3月,采用静态箱-气相色谱法,对耕地、天然草地、灌木林地、乔灌混交林地、乔木林地和果园的CH_4通量特征进行研究,并分析土壤CH_4通量与土壤温度、地表温度、含水量及全氮的关系。不同土地利用方式土壤CH_4平均通量差异显著(P<0.05),但表现相似的季节变化,呈现夏秋季高于冬春季特征。林地、园地、耕地土壤均为CH_4吸收汇,其吸收能力(平均值)为乔灌混交林(51.24μg·m^(-2)·h^(-1))>乔木林(44.80μg·m^(-2)·h^(-1))>灌木林(31.52μg·m^(-2)·h^(-1))>草地(25.89μg·m^(-2)·h^(-1))>果园(18.97μg·m^(-2)·h^(-1))>耕地(14.89μg·m^(-2)·h^(-1))。不同土地利用方式土壤CH_4吸收与土壤温度、全氮和地表大气温度均呈正相关;与土壤含水量呈负相关。其土壤表层(0~20 cm)温度是6种土地利用方式土壤CH_4吸收的主要影响因素。总之,自然条件下的土壤CH_4吸收率明显高于农业土壤CH_4吸收率,耕地转变为林地后土壤的CH_4吸收能力增强,土壤对减缓温室效应的贡献增大。

Change in land use can influence soil micro-environment along with microbial, physiological and biochemical processes, significantly affecting the generation and emission of greenhouse gases. At present, researches on greenhouse gas flux from land use transformation have mainly focused on carbon dioxide （CO2）, largely neglecting methane （CH4） generation and emission. This study determined the characteristics of soil CH4 fluxes and the influencing factors, also highlighting the critical factors of different land use patterns （cultivated land, natural grassland, shrub land, arbor and shrub land, arbor land and orchard）. The study laid the basis for predicting the contribution of land-use-driven transformation to greenhouse effects in the Loess Plateau region. The study was conducted in Malian Forest Farm of Yongshou County, Shaanxi Province. In the study, soil CH4 fluxes in different land use types were measured during the period from April 2015 to March 2016 using static chamber chromatograph techniques. The related environmental factors were recorded, including soil temperature, soil moisture, surface temperature and soil total nitrogen content. The results indicated that soils were CH4 sink under different land use types. There were significant differences （P ＜ 0.05） in CH4 uptake fluxes in different land use types. Soil CH4 fluxes in six land use types had similar seasonal variations, higher in summer and autumn than in winter and spring. Average soil CH4 uptake was in the order of arbor and shrub land （51.24 μg·m-2·h-1） ＞ arbor land （44.80 μg·m-2·h-1） ＞ shrub land （31.52 μg·m-2·h-1） ＞ natural grassland （25.89 μg·m-2·h-1） ＞ orchard （18.97 μg·m-2·h-1） ＞ cultivated land （14.89 μg·m-2·h-1）. Soil CH4 uptake fluxes in different land use types were positively correlated with soil temperature, surface temperature and total nitrogen, and negatively correlated with soil moisture. Soil temperature at the 0-20 cm soil layer was the main layer of production of soil CH4 fluxes in six land use types. The uptake CH4 under natural soil conditions was significantly higher than that in agricultural soils. The transformation of cultivated land to forest land increased CH4 uptake, enhancing the mitigation of greenhouse effect of soil.