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冠层光合参数的准确定量遥感反演是生态系统遥感模型的核心与关键。基于2011年玉米(Zea mays)整个生长发育期的冠层光谱反射率、生态系统CO2通量、微气象因子以及玉米光合生理生态指标的观测数据,开展了玉米农田生态系统冠层光合能力(Pmax,最大光合速率)与光合效率(εN,净CO2通量交换/吸收光合有效辐射(NEECO2/APAR);εG,总初级生产力/吸收光合有效辐射(GPP/APAR);α,表观量子效率)参数的多光谱遥感反演能力评估研究。结果表明,Pmax和α在整个生长季呈现单峰型变化趋势,分别于7月底、8月初达到峰值,而光合效率参数εN和εG在玉米营养生长早期数值较高,随着玉米生长发育迅速降低,而后呈现单峰型的变化趋势,峰值出现时间基本与Pmax最大值发生时间一致。基于两波段任意组合的遥感植被指数NDVI(normalized difference vegetation index)、RVI(ratio vegetation index)、WDRVI(wide dynamic range vegetation index)、EVI2(2-band enhanced vegetation index)和CI(chlorophyll index)与玉米冠层4个光合参数的统计分析表明,EVI2对冠层光合效率与光合能力参数的反演与表征效果最佳。研究表明,多光谱遥感信息对玉米生态系统冠层光合参数的变异具有较强的敏感性,可以用来监测玉米冠层光合作用的季节动态变化以及准确定量评估作物生产力和生态系统CO2交换能力。
Accurate quantitative remote sensing inversion of canopy photosynthesis parameters is the core and key of ecosystem remote sensing model. Based on the observational data of canopy spectral reflectance, ecosystem CO2 flux, micro-meteorological factors and photosynthetic physiological and ecological indicators of corn (Zea mays) in the whole growth and development period, the photosynthetic capacity of maize agroecosystem (Pmax , Maximum photosynthetic rate and photosynthetic efficiency (εN, net CO2 flux exchange / photosynthetically active radiation (NEECO2 / APAR); εG, total primary productivity / GPP / Research on Multi - spectral Retrieval Capability Evaluation of Parameters. The results showed that Pmax and α showed a monomodal trend throughout the growing season, reaching the peak at the end of July and the beginning of August, respectively. However, the photosynthetic efficiency parameters εN and εG were higher in the early vegetative stage of maize and decreased rapidly with the growth of maize , And then showed a unimodal type of change trend, the peak appearance time basically coincides with the maximum value of Pmax. Based on normalized difference vegetation index (NDVI), ratio vegetation index (RVI), wide dynamic range vegetation index (WDRVI), 2-band enhanced vegetation index (EVI2) and chlorophyll index (CI) Statistical analysis of four photosynthetic parameters of canopy showed that EVI2 had the best inversion and characterization of canopy photosynthetic efficiency and photosynthetic capacity. Studies have shown that multispectral remote sensing information is sensitive to variations of canopy photosynthesis parameters in maize ecosystem. It can be used to monitor the seasonal dynamics of photosynthesis in maize canopies and to quantitatively assess crop productivity and ecosystem CO2 exchange capacity.