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LC-21 Abstract

Regional Effects of Selective Logging on Canopy Damage and Nutrient Dynamics in Amazonia: Linking Landsat ETM+ and Field Biogeochemical Studies

Gregory Paul Asner — Carnegie Institution (US-PI)
Mercedes Bustamante — UnB - Universidade de Brasília (SA-PI)
Jose Natalino Macedo Silva — Brazilian Forest Service (SA-PI)

Selective logging is a

dominant form of land use in the Brazilian Amazon.  Several LBA studies

are quantifying the effects of logging on carbon dynamics, including the role

of fire as an agent of continued change following timber harvest. 

Despite ongoing efforts, surprisingly little is known about the extent,

intensity or biogeochemical effects of logging in Amazon forests.  At the

scale of the entire Basin, the extent of logging is hotly contested, with

current estimates ranging from 2,000-15,000 km2 yr-1.  Even less is known

about the intensity of logging, where intensity is defined here as canopy

structural damage caused by the harvest operation.  Moreover, there

exists almost no information on changes in nutrient stocks and dynamics in

selectively logged forests.  The fate of nutrients could be central to

determining rates of regrowth and the long-term sustainability of timber

harvesting in Amazonia.



During the past two years,

we have tested a method to quantify both the extent and intensity of selective

logging using Landsat ETM+ data with a Monte Carlo spectral mixture model. 

The method produces coverages of fractional canopy, bare soil and surface

necromass (slash) cover, along with statistical uncertainty maps for each

cover fraction.  The canopy fractional cover results have proven highly

correlated with field-measured forest gap fraction, which in turn, is

spatially correlated with the volume (and biomass) of wood removed from the

forest and the coarse woody debris remaining in the harvest sites.  This

approach opens the door to regional-scale studies of logging extent and

intensity as well as the resulting changes in carbon and nutrient stocks. 

Before considering the method viable for basin-wide logging studies,

additional testing is needed across a wider range of forest structural types,

logging regimes and in areas subjected to fire following harvest. 

Additional studies are also needed to determine the functional, quantitative

linkages between satellite-observed changes in forest canopy cover and exposed

surface slash, carbon stock changes in vegetation and soils, and nutrient

cycling.



We propose to extend our

remote sensing approach to a much larger region of the Amazon, and to further

develop linkages between our satellite analyses and measured carbon and

nutrient changes.  The satellite studies will take place primarily in

Para and Mato Grosso states, and will cover the period 1999-2004.  We

will use the fractional cover maps to direct field studies and continued

canopy gap fraction validation efforts across a range of forest types. 

The field sites will include low- and high-damage logging blocks with and

without fire, and additional areas containing forest structural variation

under study by groups led by Dan Nepstad, Foster Brown, Emilio Moran, and

other LBA collaborators.  At a subset of sites within the imagery, we

will quantify changes in vegetation and soil nitrogen, phosphorus, and base

cation stocks.  Using established logging chronosequences, we will

measure changes in nutrient pools, mineralization rates and other key nutrient

cycling processes to determine the short-term and the potential long-term

effects of harvest on nutrient availability.  We will use the canopy

damage information derived from Landsat ETM+ to spatially integrate nutrient

and carbon data, and to predict regional-scale changes in nutrient stocks and

their partitioning in vegetation and soils.  Our results will be compared

to studies of intact forest underway by other LBA teams.  We will also

use the Landsat analyses of logging extent and intensity to assess linkages

between logging practices and the spatial and temporal patterns of fire

occurrence over large regions of the eastern Amazon.  Fire occurrence

data have been and will be provided by the Tropical Rainfall Mapping Mission (TRMM)

satellite, and will be validated during our (and Nepstad’s) proposed field

studies.



The project will produce a

set of tangible products to be freely shared by LBA investigators and

Brazilian agencies such as EMBRAPA and INPE.  These include: (1) regional

maps of selective logging extent and canopy damage for 1999-2004; (2) nutrient

stock and flux data partitioned by forest and soil types, and by landscape

units such as logging decks, roads, skid trails, and tree-falls; (3) spatially

integrated nutrient budgets showing how nutrients are altered by logging; and

(4) regional maps of canopy damage from logging in relation to fire occurrence

from field and TRMM satellite data. This project will have a strong

educational component, including: (a) training a Brazilian and an American

post-doc, including exchange between the co-PIs labs; (b) training students

from the Universidade de Brasilia in remote sensing studies and field methods;

(c) training of EMBRAPA personnel in the use and validation of the satellite

results; and (d) outreach to Brazilian land managers interested in the use of

satellite data for logging operations (technology transfer).



The project will directly

address LBA questions LC-Q3, CD-Q3b, CD-Q3c, and ND-Q1.   In doing

so, we will contribute to answering the overall LBA question: “How do

tropical forest conversion, re-growth and selective logging influence carbon

storage, nutrient dynamics, trace gas fluxes, and the prospect for sustainable

land use in Amazonia?”

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