BIOMASS DISTRIBUTION MAPPING USING AIRBORNE DIGITAL VIDEO IMAGERY ANDSPATIAL STATISTICS IN A SEMIARID ENVIRONMENT

High resolution airborne digital video image data, biomass measurement s and spatial statistics were used to map above-ground biomass for the five major semi-arid plant communities in the Jornada Long Term Ecolo gical Research (LTER) site (southern New Mexico). The two principal ob jectives were to determine: (1) spatial characteristics of arid shrub versus semi-arid grassland vegetation; and (2) a suitable image spatia l resolution and ground sampling interval to map above-ground biomass spatial distribution for these vegetation types. The spatial character istics of each plant community were established by analyzing digital i mages at varying pixel sizes using semi-variograms. As pixel size incr eased from 0.5 m to 16 m, little information on vegetation pattern and abundance was lost in grassland and playa grassland sites. In compari son, the pattern and abundance of vegetation became indistinct in shru bland sites once pixel size exceeded mean shrub diameter. This work il lustrates the utility of variograms from remotely sensed data for two applications: (1) determining a suitable scale to examine an ecosystem 's spatial structure; and (2) providing information on the spatial pat tern of vegetation as an indicator of ecosystem condition in the conte xt of a model for desertification. (C) 1996 Academic Press Limited