Relationships between soil respiration and photosynthesis-related spectral vegetation indices in two cropland ecosystems
2012
Huang, Ni | Niu, Zheng | Zhan, Yulin | Xu, Shiguang | Tappert, Michelle C. | Wu, Chaoyang | Huang, Wenjiang | Gao, Shuai | Hou, Xuehui | Cai, Dewen
Empirical evidence for the link between vegetation photosynthesis and soil respiration (Râ) is reported for most ecosystems, but the quantification of photosynthesis parameters seldom use remote sensing data. In an attempt to clarify this issue, we focused on the growing season and examined direct relationships between Râ and photosynthesis-related vegetation indices (VIs) in maize and winter wheat agroecosystems. At seasonal time scale, crop biophysical parameters, such as leaf chlorophyll content (Chlâââf) and green leaf area index (GLAI), explained most Râ variation in the maize and winter wheat fields. Among the selected VIs, enhanced vegetation index (EVI) and red edge chlorophyll index (CIáµ£âd âdgâ) showed stronger correlations with Chlâââf for maize or GLAI for winter wheat than normalized difference vegetation index (NDVI). Moreover, for both fields, the relationship between daily mean Râ and either EVI or CIáµ£âd âdgâ was consistently stronger than the relationship between daily mean Râ and NDVI. The reason may be attributed to the saturate of NDVI at high vegetation densities and sensitivity of NDVI to background reflectance. Our results demonstrated that simple VIs (i.e. EVI and CIáµ£âd âdgâ) based entirely on remote-sensing data can provide better correlations with Râ than a number of variables which are more frequently correlated with Râ in field studies for both maize and winter wheat over the growing season. These results will be helpful for the development of future Râ model over a large spatial scale.
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