Spectral vegetation indices as the indicator of canopy photosynthetic productivity in a deciduous broadleaf forest
Spectral vegetation indices as the indicator of canopy photosynthetic productivity in a deciduous broadleaf forest
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DOI：
10.1093/jpe/rts037
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发表时间：
2013-10
影响因子：
2.7
通讯作者：
H. Muraoka;H. Noda;S. Nagai;T. Motohka;T. Saitoh;K. Nasahara;N. Saigusa
中科院分区：
文献类型：
--
作者：
H. Muraoka;H. Noda;S. Nagai;T. Motohka;T. Saitoh;K. Nasahara;N. Saigusa
目的了解森林冠层光合作用的生态生理动态及其时空尺度对于揭示生态对气候变化的响应至关重要。结合对植物生态生理学和光学遥感的观察和分析，将使我们能够实现这些研究。为了检验光谱植被指数(VIS)在评估生态系统水平光合作用方面的实用性，我们在日本中部高山超级立地的一片凉爽温带落叶阔叶林中，连续5年研究了冠层尺度的光合作用生产力与冠层光谱反射率的关系。方法用原位冠层叶面积指数(LAI)和单叶光合能力(LAI×Vcmax)估算日净光合能力，用生态系统碳循环模型估算日最大初级生产力(GPPmax)。通过对冠层光谱反射率的现场测量，得到归一化差异植被指数(NDVI)、增强植被指数(EVI)、绿红植被指数(GRVI)、叶绿素指数(CI)和冠层叶绿素指数(CCI)等5种植被指数。我们对叶片和冠层特征的现场观测，并用生态系统碳循环模型进行了分析，发现它们的物候变化是冠层光合作用的季节和年际变化的原因。5个VIS与冠层光合作用能力随季节和年际呈显著相关，其中4个VIS呈滞后型关系，仅CCI呈较好的线性关系。在所考察的VIS中，我们将EVI-GPPmax关系应用于中分辨率成像光谱仪获得的EVI数据，以估计日本中部地区GPPmax的时间和空间变化。我们的发现将提高基于卫星的森林光合作用生产力精细空间和时间分辨率估计的准确性，这是检测陆地生态系统对气象波动的任何响应所必需的。
Aims Understanding of the ecophysiological dynamics of forest canopy photosynthesis and its spatial and temporal scaling is crucial for revealing ecological response to climate change. Combined observations and analyses of plant ecophysiology and optical remote sensing would enable us to achieve these studies. In order to examine the utility of spectral vegetation indices (VIs) for assessing ecosystem-level photosynthesis, we investigated the relationships between canopy-scale photosynthetic productivity and canopy spectral reflectance over seasons for 5 years in a cool, temperate deciduous broadleaf forest at ‘Takayama’ super site in central Japan. Methods Daily photosynthetic capacity was assessed by in situ canopy leaf area index (LAI), (LAI × Vcmax [single-leaf photosynthetic capacity]), and the daily maximum rate of gross primary production (GPPmax) was estimated by an ecosystem carbon cycle model. We examined five VIs: normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), green–red vegetation index (GRVI), chlorophyll index (CI) and canopy chlorophyll index (CCI), which were obtained by the in situ measurements of canopy spectral reflectance. Important Findings Our in situ observation of leaf and canopy characteristics, which were analyzed by an ecosystem carbon cycling model, revealed that their phenological changes are responsible for seasonal and interannual variations in canopy photosynthesis. Significant correlations were found between the five VIs and canopy photosynthetic capacity over the seasons and years; four of the VIs showed hysteresis-type relationships and only CCI showed rather linear relationship. Among the VIs examined, we applied EVI–GPPmax relationship to EVI data obtained by Moderate Resolution Imaging Spectroradiometer to estimate the temporal and spatial variation in GPPmax over central Japan. Our findings would improve the accuracy of satellite-based estimate of forest photosynthetic productivity in fine spatial and temporal resolutions, which are necessary for detecting any response of terrestrial ecosystem to meteorological fluctuations.