## 5 Conclusions  
In this study, a series of narrowband bio-indicators derived from EO-1 Hyperion were employed to monitor C fluxes in a Korean pine and broad-leaved mixed forest landscape on the northern slope of Changbai Mountain in northeast China for the first time. Three categories of bio-indicators, red edge indices, chlorophyll content indices, and indices based on LUE principles, demonstrated improvements for capturing the variation of GPP and Re. The scaled photochemical reflectance index (SPRI)*NDVI had the best goodness of fit for GPP and Re. The bio-indicators used for inversing regional C fluxes were SPRI*NDVI, a function of NDVI (related to canopy \(f_{\mathrm{APAR}}\)) and narrowband SPRI (a dynamic efficiency factor related to canopy light use efficiency). We found a significant relationship between SPRI*NDVI and GPP and Re, R\({}^{2}=0.86\) and 0.89, \(p<0.0001\), respectively. The MCARI/OSAVI[705, 750], Vogelmann Index, Chlorophyll Index RedEdge 710, and SPRI*EVI had potential for utilization as bio-indicators for monitoring the variation of regional ecosystem productivity. The inversed regional average GPP was 6.22 gC\(\cdot\)m\({}^{-2}\cdot\)day\({}^{-1}\); the average Re was 5.78 gC\(\cdot\)m\({}^{-2}\cdot\)day\({}^{-1}\); and the average NEE was 0.44 gC\(\cdot\)m\({}^{-2}\cdot\)day\({}^{-1}\) on DOY 166 in 2008. These values indicate that the study area is a carbon sink region in the growing season. The inversed daily GPP spatial patterns were consistent with corresponding results from the VPM Model.  
The NDNI had a significant correlation with the NEE, with R = 0.805, \(p<0.01\). This correlation has not been previously described in the literature. The relationships between other narrowband bioindicators and average NEE5 were significant with \(p<0.05\). We believe the methodology needs additional validation with additional forest land cover types, however, the direct correlation between NEE and narrowband bio-indicators described in our study provides a simple and effective approach to monitor C fluxes variation and map the spatial patterns of regional NEE.  
Some limitations still exist when bio-indicators and models are used for routine mapping of C fluxes in different vegetable types. We predict that the method will become more useful with the accumulation of matched spectral and C flux data. For example, with the wide application of MODIS, SPRI*NDVI could be evaluated at large spatial scales. We believe that, in the near future, more narrowband bio-indicators could be identified as an alternative method for monitoring and modeling of vegetation ecosystems at large spatial scales.  
The project was funded by the National Basic Research Program of China on Global Change (Grant No. 2010 CB950701, 2010 CB833503) and the Chinese Academy of Sciences for Strategic Priority Research Program (Grant No. XDA05050602).  
[PERSON] was the principle investigator and was responsible for the research design, field and laboratory research, data analysis, and manuscript preparation. [PERSON] and [PERSON] were responsible for the research design, review of all research finding and analyses, and manuscript preparation. [PERSON] assisted in conducting fieldwork, data processing, and manuscript preparation. [PERSON], [PERSON], [PERSON], and [PERSON] supported the Hyperion and model validation input data preparation, interpretation of the results, and manuscript preparation.  
The authors declare no conflict of interest.