Vegetation indices, CO2 flux, and biomass for Northern Plains Grasslands
Vegetation indices, CO2 flux, and biomass for Northern Plains Grasslands
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DOI：
10.2307/4004043
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发表时间：
2003-07-01
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影响因子：
--
通讯作者：
Karn, JF
中科院分区：
文献类型：
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作者：
Frank, AB;Karn, JF
原生草原是大气CO2封存的汇，但缺乏将特定地点的CO2通量测量扩展到区域尺度的方法。本研究的目的是确定利用冠层辐射反射率估算半干旱草原CO2通量的效用。比较了由手持辐射计获得的光谱反射率数据计算的归一化植被指数（NDVI）与鲍文比/能量平衡测量计算的CO2通量之间的关系。在北北州Mandan附近的非放牧草原、放牧草原和灌木为主的草原上测量了植物生长季节的二氧化碳通量，并测量了蒸散发（ET）、绿色生物量和绿叶面积指数（LAI）。1999年、2000年和2001年NDVI与植被参数生物量和LAI的相关系数分别超过0.84、0.74和0.91；与CO2通量相关性在1999年、2000年和2001年分别超过0.63、0.68和0.69；与ET的相关性在1999年、2000年和2001年分别超过0.91、0.92和0.90。回归分析表明，NDVI与生物量（R-2 = 0.83）和LAI （R-2 = 0.77）呈非线性关系，与CO2通量（R-2 = 0.51）和ET （R-2 = 0.81）呈线性关系。NDVI与生物量、LAI、CO2通量和ET之间的关系大致相似，表明NDVI可用于预测北部大平原半干旱草地的冠层CO2通量率。
Native grasslands are a sink for atmospheric CO2 sequestration, but ways for extending site-specific CO2 flux measurements to a regional scale are lacking. Objectives of this study were to determine the utility of using canopy radiometric reflectance for estimating CO2 fluxes for semiarid grasslands. The relationship between the normalized difference vegetation index (NDVI) calculated from spectral reflectance data obtained with hand-held radiometers was compared to CO2 flux calculated from Bowen ratio/energy balance measurements. Carbon dioxide flux was measured during the plant growing season over a nongrazed prairie, grazed prairie, and a shrub dominated prairie site near Mandan, N.D. Measurements were also made of evapotranspiration (ET), green biomass, and green leaf area index (LAI). Correlation coefficients of NDVI with vegetation parameters of biomass and LAI for each site and year exceeded 0.84 in 1999, 0.74 in 2000, and 0.91 in 2001; with CO2 flux correlations exceeded 0.63 in 1999, 0.68 in 2000, and 0.69 in 2001; with ET correlations exceeded 0.91 in 1999, 0.92 in 2000, and 0.90 in 2001. Regression analysis over all years and sites produced a nonlinear relation between NDVI and both biomass (R-2 = 0.83) and LAI (R-2 = 0.77) and a linear relationship between NDVI and both CO2 flux (R-2 = 0.51) and ET (R-2 = 0.81). The relationships between NDVI and biomass, LAI, CO2 flux, and ET for the 3 grassland sites, which differed in management and vegetation, were generally quite similar suggesting that NDVI has potential for use in predicting canopy CO2 flux rates for semiarid grasslands in the Northern Great Plains.