A Hybrid Model for Mapping Relative Differences in Belowground Biomass and Root:Shoot Ratios Using Spectral Reflectance, Foliar N and Plant Biophysical Data within Coastal Marsh

Remote Sensing

Jessica L. O𠆜onnell¹  Kristin B. Byrd²  Maggi Kelly¹  Richard W. Gould³  Yoshio Inoue³ 

[1] Department of Environmental Sciences Policy and Management, University of California, Berkeley, Berkeley, CA 94720, USA;U.S. Geological Survey, Western Geographic Science Center, Menlo Park, CA 94025, USA;;Department of Environmental Sciences Policy and Management, University of California, Berkeley, Berkeley, CA 94720, USA

关键词: belowground biomass;    carbon cycling;    coastal tidal freshwater wetlands;    eutrophication;    Landsat;    nitrogen cycling;    productivity;    root:shoot ratio;    remote-sensing;    sea level rise;   

DOI  :  10.3390/rs71215837

来源: mdpi

【 摘 要 】

Broad-scale estimates of belowground biomass are needed to understand wetland resiliency and C and N cycling, but these estimates are difficult to obtain because root:shoot ratios vary considerably both within and between species. We used remotely-sensed estimates of two aboveground plant characteristics, aboveground biomass and % foliar N to explore biomass allocation in low diversity freshwater impounded peatlands (Sacramento-San Joaquin River Delta, CA, USA). We developed a hybrid modeling approach to relate remotely-sensed estimates of % foliar N (a surrogate for environmental N and plant available nutrients) and aboveground biomass to field-measured belowground biomass for species specific and mixed species models. We estimated up to 90% of variation in foliar N concentration using partial least squares (PLS) regression of full-spectrum field spectrometer reflectance data. Landsat 7 reflectance data explained up to 70% of % foliar N and 67% of aboveground biomass. Spectrally estimated foliar N or aboveground biomass had negative relationships with belowground biomass and root:shoot ratio in both Schoenoplectus acutus and Typha, consistent with a balanced growth model, which suggests plants only allocate growth belowground when additional nutrients are necessary to support shoot development. Hybrid models explained up to 76% of variation in belowground biomass and 86% of variation in root:shoot ratio. Our modeling approach provides a method for developing maps of spatial variation in wetland belowground biomass.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.