Dynamic characteristics of soil respiration of Savanna ecosystem in dry hot valley of Yuanjiang

[Objective] Soil respiration plays an important role in regulating CO_2 concentration in the atmosphere.Soil respiration in the Savanna ecosystem is one of the main sources of global greenhouse gas emissions,but its emission characteristics and main influencing factors are not clear.[Method] Taking the Savanna ecosystem in dry hot valley of Yuanjiang inYunnan Province as an example,the soil respiration was measured from June 2014 to June 2015 by static chamber method,and the dynamic characteristics and its influencing factors in the Savanna ecosystem in Yuanjiang were studied.[Result] Soil temperature,soil moisture and soil respiration had obvious seasonal variations,and as expected,they were significantly(P<0.01)higher in rainy season than in dry season.The relationship between soil respiration and soil temperature and soil moisture are exponential and parabola.The temperature Q_(10) at 5 and 10 cm of soil was 1.73 and 1.98 respectively,which was less than the global average of 2.0.Therefore,using 10 cm soil temperature could better simulate soil respiration.Fitting analysis of soil temperature,water content and soil respiration showed that the soil respiration of Savanna ecosystem in Yuanjiang was mainly restricted by water condition.The annual emission of soil respiration in the ecosystem was 4.20 t·hm~(-2)·a~(-1),including 2.71 t·hm~(-2) in rainy season,accounting for 64.5% of the total annual carbon emission,and 1.49 t·hm~(-2) in dry season,accounting for 35.5% of the total annual carbon emission.The average value of soil respiration in global Savanna ecosystem is 8.16 t·hm~(-2)·a~(-1).[Conclusion] Compared with the global Savanna ecosystem,the total amount of soil respiration in Yuanjiang was in a lower position,which could be attributed to the lower rainfall in the Savanna ecosystem in Yuanjiang.There exists a significant positive correlation between rainfall and soil respiration in the Savanna region(R~2=0.61,P<0.001)

元江干热河谷稀树灌草丛生态系统土壤呼吸动态特征

【目的】土壤呼吸对大气中二氧化碳浓度有重要的调节作用。萨王纳生态系统土壤呼吸是全球温室气体主要排放源之一,但是其排放特征与主要影响因子尚不清楚。【方法】以元江干热河谷(萨王纳)稀树灌草丛生态系统为对象,利用静态箱法,从2014年6月到2015年6月对元江土壤呼吸进行测量,研究了元江干热河谷稀树灌草丛生态系统土壤呼吸动态特征及其影响因子。【结果】元江干热河谷稀树灌草丛生态系统土壤温度、水分和呼吸速率具有明显的季节变化,雨季高于干季。土壤呼吸速率与土壤温度和土壤湿度分别呈指数和抛物线关系,土壤5和10cm处温度Q_(10)分别为1.73和1.98,小于全球均值2.0,采用10cm土壤温度能更好地模拟土壤呼吸。通过土壤温度、湿度与土壤呼吸双因子拟合分析得出元江萨王纳生态系统的土壤呼吸主要受到水分条件的制约;生态系统土壤呼吸年排放量为4.20t·hm~(–2)·a~(–1),其中雨季2.71t·hm~(–2),占全年碳排放总量的64.5%,干季的二氧化碳排放量为1.49t·hm~(–2),占全年碳排放总量的35.5%。全球萨王纳生态系统土壤呼吸均值为8.16t·hm~(–2)·a~(–1)。【结论】元江土壤呼吸总量在全球萨王纳生态系统中处于较低位置,主要是因为元江萨王纳生态系统降水量较全球萨王纳低,而降水量与萨王纳地区土壤呼吸呈极显著正相关关系(R~2=0.61,P<0.001)