Linking physiological responses, chlorophyll fluorescence and hyperspectral imagery to detect salinity stress using the physiological reflectance index in the coastal shrub, Myrica cerifera

Department of Biology, Virginia Commonwealth University, Richmond, Virginia 23284, USA
Remote Sensing of Environment (Impact Factor: 6.39). 06/2008; 112(10):3865-3875. DOI: 10.1016/j.rse.2008.06.004


Measurements of physiology, chlorophyll fluorescence and hyperspectral reflectance were used to detect salinity stress in the evergreen coastal shrub, Myrica cerifera on Hog Island, Virginia. Two experimental sites were used in our study, the oceanside of a M. cerifera thicket, which is exposed to sea spray, and the protected, leeside of the thicket. Using the physiological reflectance index (PRI), we were able to detect stress at both the canopy and landscape level. Monthly variations in stomatal conductance, photosynthesis, and relative water content indicated a strong summer drought response that was not apparent in chlorophyll fluorescence or in the water band index (WBI) derived from canopy and airborne reflectance measurements. In contrast, there were significant differences in both physiological measurements and tissue chlorides between the two sites used in the study, indicating salinity stress. This was reflected in measurements of PRI. There was a positive relationship between PRI measured at the canopy-level and light-adapted fluorescence (ΔF/F′m; r2 = 0.69). PRI was significantly lower on the oceanside of the Myrica cerifera thicket. PRI was not significantly related to NDVI (r2 = 0.01) at the canopy-level and only weakly related (r2 = 0.04) at the landscape-level, suggesting that the indices are independent. The chlorophyll index (CI) did not show any significant changes between the two sites. Frequency histograms of pixels sampled from airborne hyperspectral imagery revealed that the distribution of PRI was shifted to the right on the backside of the thicket relative to the oceanside and there was a significant difference between sites. These results suggest that PRI may be used for early identification of salt-stress and to identify areas across the landscape where community structure may change due to sea-level rise.

Download full-text


Available from: Donald Young, Jan 23, 2014
  • Source
    • "11 & 13). Other studies have suggested various biophysical relationships with plant spectral response such as LAI and NEP (Campbell et al., 2013; Naumann, Anderson & Young, 2008). Furthermore , studies have also suggested the link between subsurface water chemistry and spectral response with plant stress (Batelaan, De Smedt, De Becker, & Huybrechts, 1998; Song, White & Heumann, 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Coastal mangrove ecosystems are under duress worldwide because of urban development, sea-level rise, and cli-mate change, processes that are capable of changing the salinity and nutrient concentration of the water utilized by the mangroves. This study correlates long-term water chemistry in mangrove environments, located in Ever-glades National Park, with mangrove spectral reflectance measurements made at both the leaf and canopy scales. Spectral reflectance measurements were collected using a handheld spectrometer for leaf-level measurements and Landsat 5TM data for regional coverage. Leaf-level reflectance data were collected from three mangrove spe-cies (i.e., red, black and white mangroves) across two regions; a tall mangrove (~18 m) and dwarf mangrove (1– 2 m) region. The reflectance data were then used to calculate a wide variety of biophysical reflectance indices (e.g., NDVI, EVI, SAVI) to determine signs of stress. Discrete, quarterly water samples from the surface water, groundwater, and pore water (20 and 85 cm depths) and daily autonomous surface water samples were collect-ed at each site and analyzed for major anions (Cl − and SO 4 2−), cations (Na + , K + , Mg 2+ , and Ca 2+), total nitrogen (TN) and total phosphorus (TP). Mangrove sites that exhibited the highest salinity and ionic concentrations in the surface and subsurface water also had the lowest near-infrared reflectance at both the leaf and satellite levels. Seasonal reflectance responses were measured in the near-infrared (NIR) wavelengths at both the leaf and can-opy scales and were strongly correlated with nutrient and ionic concentrations in the surface and subsurface water, even though there was no significant separability between the three mangrove species. Study sites that experienced the greatest variability in surface and subsurface water ionic concentrations also exhibited the greatest fluctuations in NIR spectral reflectance. Landsat 5TM images were able to detect tall and dwarf man-groves by the differences in spectral indices (e.g., NDVI, NDWI, and EVI) because of the variability in the back-ground conditions amongst the environments. In addition, Landsat 5TM images spanning 16 years (1993– 2009) were successfully used to estimate the seasonal variability in ionic concentrations in the surface water across the Florida Coastal mangrove ecotone. This study has shown that water chemistry can be estimated indi-rectly by measuring the change in spectral response at the leaf-or satellite-scale. Furthermore, the results of this research may be extrapolated to similar coastal mangrove systems throughout the Caribbean and world-wide wherever red, black, and white mangroves occur.
    Full-text · Article · Nov 2014 · Remote Sensing of Environment
  • Source
    • "Between 1999 and 2011, 14 projects on soil salinization monitoring, forecasting and visualization were funded by National Natural Science Foundation of China (NNSF). The projects were conducted by different means and using different data sources, mainly including EM38, radar remote sensing, MODIS, microwave imaging radiometry, hyperspectral data, geostatistics interpolation, and computer mapping (Kerr et al., 2001; Naumann et al., 2008; Slavich and Petterson, 1990; Swift and Mcintosh, 1983; Walter et al., 2001; Yao et al., 2007). The assessment techniques mainly included field-scale soil salinity migration and simulation research, as well as soil salinization detection and assessment techniques such as GIS and EM38 combined rapid soil salinization degree assessment system , saline soil fertility and soil adaptability assessment system, soil salinization risk assessment system, and soil quality grade assessment system (Chen et al., 1993; Ellsworth et al., 1996; Yang and Yao, 2009; Yang et al., 2011; Yao et al., 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: With the environmental deterioration caused by the advance of climate change, soil salinization is a serious and growing global problem. Currently about 7% of the world’s land surface is threatened by salinization. China is a country whose soils are severely affected by this problem, which, due to its extensive area, and wide distribution poses a serious threat to regional agricultural development. In this review, we summarize the framework for soil salinization research in China over the past 70 years, assess the weaknesses of existing research in both a domestic and international context, highlight the trends and key findings of global research about saline soils over the past 30 years, and propose six major fields and directions for future research on saline soil.
    Full-text · Article · Oct 2014 · Journal of Geographical Sciences
  • Source
    • "Both the range of available light and utilization of strong light were reduced for two species. This finding is consistent with previous results (Naumann et al., 2008a, 2008b; Wu et al., 2010). The R d value also increased, which is another reason for the decrease in P n (Hajek and Adamec, 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hibiscus hamabo, a native tidal woody species, and Myrica cerifera, an exotic tidal woody species, have been widely planted on coastal beaches in subtropical China. However, whether there are differences in physiological response and tolerance to immersion between the two tidal species is still unknown. Our objectives were to evaluate differences in the photosynthetic and physiological responses to tidal immersion for the two species in the context of sea level rise. With increasing immersion, net photosynthesis, stomatal conductance, intercellular CO2 concentration, and light saturation point declined progressively for both species, whereas dark respiration and light compensation point showed the reverse trend. Lower variation was observed in H. hamabo than in M. cerifera for each index in the same treatment. Photosynthetic ability and utilization of light, especially under high light intensity, decreased for both species. Leaf soluble sugar and protein contents, and glycolate oxidase activity first increased and then decreased with increasing of immersion degree, with the higher values observed in the W4 (4 h duration, 15 cm depth) and W6 (6 h duration, 25 cm depth) treatments for H. hamabo, and W2 (2 h duration, 5 cm depth) and W4 treatments for M. cerifera. These findings indicate that H. hamabo has a better ability to keep the reduction of photosynthesis at a minimum through soluble substance regulated osmotic potential and avoiding excess light damage to the photosynthetic system through increased photorespiration, heat dissipation, chlorophyll fluorescence. Our results suggest that H. hamabo is more tolerant to tidal immersion than M. cerifera, and therefore it is better adapted to the anticipated sea level rise in future.
    Full-text · Article · Dec 2013 · Estuarine Coastal and Shelf Science
Show more