陆地表面辐射温度对土壤呼吸的影响机理及其模型构建

Soil respiration influences global carbon cycle. Temperature and precipitation are often used to simulate soil respiration in the soil respiration estimation model at regional scale. The air temperature used in the model is from the thermometer screen which located at a height of 1.5 m above the ground and it has some difference with vegetation temperature. When we scale up soil respiration stimulation from a plot scale to a larger region, the representative of regional temperature distribution data which come from limited observation stations by inserting method have some errors. Those errors of air temperature will have probability of passing the errors and accumulating them to the calculated results of soil respiration estimation. .Aiming at those problems, an idea of substituting land surface temperature for the air temperature is put forward. The satellite remote sensing exploration can get continuous distribution radiation temperature. Compared with air temperature, radiation temperature can better represent the temperature of plant and soil. The purpose of the project is to use field observation data of both surface infrared temperature and soil respiration, at daily and seasonal scales, to establish their relationship and to futher analyse the influence mechanism of infrared temperature on soil respiration as well as to construct the correlation model of infrared temperature and soil respiration. Furthermore, using both the soil respiration dataset of different vegetation types which we have measured from 2005 to 2011 in Luliang mountain area and the dataset of infrared temperature from remote sensing to evaluate the accuracy of the soil respiration model gained from remote sensing models. In brief, the aim of the project is about to provide a new method for soil respiration exploration at spacial scales.

土壤呼吸影响着全球碳循环。区域尺度的土壤呼吸估算模型通常利用气温和降水量来模拟土壤呼吸量。模型中所用的气温是近地面1.5m高处百叶箱内的温度。利用气温把土壤呼吸的科学模拟从点尺度外推到更大空间时，必须进行气温的空间插值，这将会把差值引起的误差传递到区域呼吸量的估算中，从而增加了估算的不确定性。.针对利用气温估算土壤呼吸量时存在的客观问题，项目提出用地表辐射温度来替代气温进行土壤呼吸模拟。与气温相比，卫星遥感探测可以获得连续分布的地表辐射温度。课题拟通过对日、季节尺度不同生态系统地表辐射温度和土壤呼吸速率同步进行的观测实验，分析探讨地表辐射温度对土壤呼吸的影响机理，构建地表辐射温度与土壤呼吸的关系模型。并利用前期观测的7年土壤呼吸的数据集，对基于卫星遥感的辐射温度模型估算的土壤呼吸的精度进行检验。为全球碳平衡估算和全球变化潜在效应估计提供最为基本的数据，为土壤呼吸的空间尺度扩展提供新的思路。

土壤呼吸（Rs）影响着全球碳循环。区域尺度的Rs估算模型通常利用气温和降水量来模拟Rs量。利用气温把Rs的科学模拟从点尺度外推到更大空间时，必须进行气温的空间插值，这将会把差值引起的误差传递到区域Rs量的估算中，从而增加了估算的不确定性。针对利用气温估算Rs量时存在的客观问题，项目提出用地表辐射温度（LST）来替代气温进行Rs模拟。课题组通过对时空尺度不同生态系统LST和Rs同步进行的观测实验，分析探讨了LST对Rs的影响机理，构建了LST与Rs的关系模型。研究结果如下：. 1. 庞泉沟自然保护区7个样地Rs的季节变化与MODIS的Terra和Aqua卫星白天和夜间过境时的LST（LSTtd和LSTtn、LSTad和LSTan）都呈极显著的指数函数关系，决定系数从小到大依次是LSTtd﹤LSTad﹤LSTtn﹤LSTan。除人工林样地包含LST和植被指数（VI）的Rs = a ebLST VIc和Rs= a ebLST+cVI模型的R2略低于包括土壤温度和水分的双因素模型的R2外，其他6个样地的R2都有不同程度的提高（4个样地）或者相等（2个样地）。有6个样地用LSTan和归一化植被指数（NDVI） 做自变量Rs = a ebLST VIc和Rs= a ebLST+cVI模型的R2高于用LSTtn和NDVI 做自变量的同一模型的R2，表明在本研究中，用LSTan和NDVI做自变量的双变量模型更适于预测Rs。.2. 季节尺度上，天龙山自然保护区的灌木群落5个LST和3个与T5、T10和T15（5、10、15 cm深度的土壤温度）Rs都呈极显著正相关，相关系数从小到大依次是LSTtd﹤LSTad﹤LSTav﹤T5﹤T15﹤T10﹤LSTtn﹤LSTan。.3. 亚高山草甸的Rs的日变化与冠层温度（Tc）、T5、T10、T15指数方程的决定系数R2值依次为0.78、0.86、0.59、0.17。Tc与Rs的关系仅次于T5与呼吸的关系，明显好于T10和T15与呼吸的关系。.4. 空间尺度上，庞泉沟自然保护区3个时期测定的Rs与平均LST（LSTav）的关系好于与两个卫星过境时的四个瞬时温度的，与NDVI的关系好于与增强植被指数（EVI）的。6个复合模型中，包含LSTav和NDVI的双变量线性模型的R2最高、RMSE和AIC最低。.本研究可为土壤呼吸的空间尺度扩展提供新的思路