Canopy foliar Nitrogen Concentration （CNC） is one of the most important parameters influencing vegetation productivity in forest ecosystems. In this study, we explored the potential of imaging spectrometry （hyperspectral） remote sensing of CNC in conifer plantations in China’s subtropical red soil hilly region. Our analysis included data from 57 field plots scattered across two transects covered by Hyperion images. Single regression and partial least squares regression （PLSR） were used to explore the relationships between CNC and hyperspectral data. The correlations between CNC and nearinfrared relfectance （NIR） were consistent in three data subsets （subsets A-C）. For all subsets, CNC was signiifcantly positively correlated with NIR in the two transects （R2=0.29, 0.33 and 0.36, P＆lt;0.05 or P＆lt;0.01, respectively）. It suggested that the NIR-CNC relationship exist despite a weak one, and the relationship may be weakened by the single canopy structure. Besides, we also applied a shortwave infrared （SWIR） index - Normalized Difference Nitrogen Index （NDNI） to estimate CNC variation. NDNI presented a signiifcant positive correlation with CNC in different subsets, but like NIR, it was also with low coefifcient of determination （R2=0.38, 0.20 and 0.17, P＆lt;0.01, respectively）. Also, the correlations between CNC and the entire spectrum reflectance （or its derivative and logarithmic transformation） by PLSR owned different signiifcance in various subsets. We did not ifnd the very robust relationship like previous literatures, so the data we used were checked again. The paired T-test was applied to estimate the inlfuence of inter-annual variability of FNC on the relationships between CNC and Hyperion data. The inter-annual mismatch between period of ifeldwork and Hyperion acquisition had no inlfuence on the correlations of CNC-Hyperion data. Meanwhile, we pointed out that the lack of the canopy structure variation in conifer plantation area may lead to these weak relationsh
Soil dissolved organic carbon （DOC） is an active fraction of the soil organic carbon （SOC） pool and links terrestrial and aquatic systems. The degradation of DOC can affect carbon cycling, nutrient dynamics and energy supply to microorganism, and consequently change biogeochemical processes. This study investigated the vertical and seasonal variability of soil DOC concentrations and its controls in a 23-year-old planted slash pine （Pinus elliottii） forest at Qianyanzhou Forest Experimental Station （QFES） in Southern China. Soil solutions were collected at bimonthly intervals at depths of 10, 20 and 30 cm by a mechanical-vacuum extractor from November 2007 to March 2009, and at monthly intervals at depths of 10, 30 and 50cm from April 2009 to October 2010. The DOC concentrations were determined with a total organic carbon （TOC） analyzer. Mean （±standard deviation） DOC concentrations at depths of 10cm, 20cm, 30cm and 50cm were 12.4±4.4, 10.6±6.3, 8.7±2.6, and 8.0±5.9 mg L^-1, respectively. Both seasonal and spring means of DOC concentration showed a decreasing trend with increasing depth, while there was no clear trend for the summer, autumn, or winter seasons. DOC concentrations during spring, summer, autumn and winter ranged from 4.8 to 21.5, 4.9 to 26.2, 5.4 to 17.1, 4.9 to 14.6 mg L-1, respectively, their mean DOC concentrations were 10.2, 10.5, 10.8 and 8.3 mg L 1, respectively. No consistent pattern of seasonal variability of DOC concentrations at different depths was observed. No obvious relationship between organic carbon content of forest litter and DOC concentration was found. There was a positive linear relationship between SOC and DOC concentration （R2=0.19, p〈0.01）, which showed that SOC was one of the main controls of DOC. A positive exponential relationship existed between soil temperature at 5 cm and DOC concentrations at 10 cm depth in slash pine, masson pine （Pinus massoniana） and Chinese fir （Cunninghamia lanceolata） planted forests （R2=0.12, p〈0.01�
