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Summary: 200 WESSMAN, ARCHER, JOHNSON AND ASNER
A conceptual model illustrating the challenges to assessingregional woody
plant cover and dynamics in the context of brush managementis presentedin Figure 4.
Line I represents woody stand development that might occur in the absence of
disturbance (e.g. elimination of fire due to grazing or active suppression) or
managementintervention. Line II representsa standwhose developmentis intemrpted
by natural (e.g.drought (Archer et a1.,1988;Allen andBreshears,1998),wildfire (Kurz
andApps, 1999),pathogenic(McArthur et a1.,1990;Ewing andDobrowolski, 1992)or
anthropogenic(e.g.brushmanagement(Scifres1980,Bovey 2001) eventsthat 'reset'
the carbon accumulation process. The magnitude of these setbacks and rates of
recovery vary dependingupon the type, intensity and spatial extent ofdisturbance, soil
type, environmental conditions immediately preceding and following the disturbance,
and the growth form (evergreenvs. deciduous)and regenerativehaits involved. Some
stands regenerating from these setbacksmight receive follow-up brush management
treatments (Line III), but others may not due to financial constraints, availability of
subsidies,and many other factors. Thus, remote sensingobservationsover large areas
and limited temporal resolution show net changes(A), whereby increasesin woody
cover on some landscapesor managementunits (B and C) are offset by decreasesin
others(D).
Regional
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