基于能量平衡原理的栓皮栎幼苗土壤水分胁迫指数下基线研究

Study on base line of CWSI for Quercus variabilis seedlings based on energy balance principle

旨为精准确定在充分供水状态下栓皮栎幼苗的叶气温差与大气饱和水汽压差(VPD)的线性回归关系,从而对前人得出的CWSI(crop water stress index)经验模型进行优化。在河南农业大学林学院科研基地盆栽栓皮栎幼苗,用干湿参考面法,测定气温、太阳辐射、叶气温差、大气饱和水汽压差,通过能量平衡原理理论分析和计算,确定栓皮栎幼苗的CWSI模型合理的上、下基线。结果表明:1)干参考面条件下,栓皮栎幼苗的叶气温差同太阳辐射为显著正相关关系,可以确定CWSI经验模型中的上基线为一直线:Δt_(干)=0.007 Q+1.621;2)在湿参考面下,栓皮栎幼苗的叶气温差Δt_(湿)同大气饱和水汽压差(VPD)V为负相关关系,直线回归关系显著,得到CWSI经验模型中优化后的下基线:Δt_(湿)=-1.218 V+1.987;3)用所得上下基线优化CWSI模型计算栓皮栎幼苗CWSI值,与土壤水分的线性关系显著;4)能量平衡方程的热量收支计算方法可以更准确确定叶气温差与VPD的关系,进而优化CWSI模型。

[Background]In order to accurately determine the linear regression relationship between leaf temperature difference and atmospheric vapor pressure difference(VPD)of Quercus variabilis seedlings under the condition of adequate water supply,and to optimize the crop water stress index(CWSI)empirical model established by predecessors,Zhengzhou city in Henan province,where plant drought is a significant problem,was selected as the main research area,aiming to analyze and understand the dynamic change of soil water and the response degree of plants in a more representative way,so as to build a more applicable CWSI model and soil water diagnosis model.[Methods]The temperature,solar radiation,leaf temperature difference and atmospheric vapor pressure difference of Q.variabilis seedlings in the pot experiment were measured by dry-wet reference surface method in research base of College of Forestry,Henan Agricultural University.The reasonable upper and lower baselines of CWSI model of Q.variabilis seedlings were determined by theoretical analysis and calculation of energy balance principle.[Results]Under dry reference plane condition,the leaf temperature differenceΔt_(干)of Q.variabilis seedlings was significantly positively correlated with solar radiation Q,and the upper baseline of CWSI empirical model was determined as a straight line:Δt_(干)=0.007 Q+1.621.Under the wet reference plane,there was a negative correlation between leaf temperature differenceΔt_(湿)and V(VPD)of atmospheric saturated water vapor pressure difference,and the linear regression relationship was significant.The optimized lower baseline of CWSI empirical model was obtained:Δt_(湿)=-1.218 V+1.987.Thus,the CWSI empirical model after optimizing the lower baseline is I=t_(ca)-(-1.218V+1.987)/(0.007Q+1.621)-(-1.218V+1.987)[SX)],t_(ca)is the measured leaf-air temperature difference.The CWSI value of Q.variabilis seedlings was calculated by using the optimized CWSI model with the obtained upper and lower baseline.The linear relationship between CWSI value I and soil moistureθwas significant.The diagnostic formula isθ=-24.65I+27.91.The relationship between CWSI and soil moisture content was as follows:12%soil moisture corresponded to mild drought,and CWSI was about 0.65.The soil moisture of 8%-10%corresponded to moderate drought,and the CWSI was 0.75-0.8.Soil moisture of 5%-8%corresponds to severe drought and CWSI is 0.8-0.95.When soil moisture was lower than 5%and CWSI was greater than 0.95,the seedling stress was fatal.[Conclusions]The relationship between leaf temperature difference and VPD can be more accurately determined by the heat budget calculation method of energy balance equation,so as to optimize the CWSI model,and then calculate the linear relationship between CWSI of different crops and soil moisture according to this model,and obtain the soil moisture diagnosis model.The soil moisture of different crops or forest plants can be diagnosed according to the solar radiation and air temperature and humidity of remote sensing leaves and weather stations.