Using Remotely Sensed Imagery for Forest Resource Assessment and Inventory

Forests are complex ecosystems that develop over centuries through the interactions between organisms and biogeochemical cycles of elements occurring in the soil-atmosphere continuum. The biomass and structure of a forest stand is involved in several ecosystem processes and has been used as an indicator of forest health and productivity. The forest biomass is a key component of the carbon cycle, as forests represent large carbon sources and sinks (Skole & Tucker, 1993). Tree canopy height and area are highly correlated with biomass and are important inputs in forest productivity models (Drake, 2001). The variation of forest biomass production has been related to variations in canopy light absorption since the amount and spatial distribution of vegetation, directly affects light availability in forests. Forest stand factors that determine light absorption include: amount of leaf area, crown and canopy structure, phenology, and leaf optical properties (Jarvis and Leverenz, 1983). The amount of leaf area, measured through the leaf area index (LAI), is considered a key parameter of ecosystem processes (Asner and Wessman, 1997). Several forest ecosystem processes are strongly controlled by LAI including interception of light (Machado & Reich, 1999) and precipitation (Van Dijk & Bruijnzeel, 2001), gross primary productivity (Jarvis & Leverenz, 1983), transpiration (Granier et al., 2000), and soil respiration (Davidson et al., 2002). LAI is also related to other important ecological processes such as evapotranspiration, CO2 and water exchange with the atmosphere, nutrient cycling and nutrient storage in plants (Dougherty et al. 1995). Therefore, measurements of forest biomass and structure are critical in the study of ecosystems for many applications including management of forest plantations, wildlife and biodiversity, fire modeling, and carbon sequestration among others.