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ND-11 Abstract

Carbon and Nutrient Stocks and Regrowth in Reduced Impact and Conventionally Logged Forests and Settlements in NW Mato Grosso, Brazil

Eduardo Guimarães Couto — UFMT - Universidade Federal do Mato Grosso (SA-PI)
Johannes Lehmann — Cornell University (US-PI)
Carlos Alberto Moraes Passos — UFMT - Universidade Federal do Mato Grosso (SA-PI)

Research Approach





Our major focus will be on the questions “What are the

impacts of conventional and reduced impact logging on above and belowground

carbon and nutrient stocks and water and nutrient fluxes and how do these

impacts change over time following the logging?” Answering these carbon and

nutrient dynamics science questions will require ground-based biogeochemical

studies and the enhancement and use of currently available GIS techniques.





The specific goals of our

project are to: (1) Measure existing forest biomass (carbon) and nutrient stocks

and validate available models for estimating forest biomass. (2) Quantify the

impact of soil texture and fertility gradients on above and belowground C and

nutrient stocks in local forests, and (3) Measure the impact of conventional

(CL) versus reduced impact logging (RIL) on C dynamics. If time and funds

permit, we will also obtain measurements on the quantity and composition of

sediment, nutrients, water and organic matter entering first order streams.





We will estimate aboveground live biomass in primary forest

using four alternative allometric equations that were calculated for moist

tropical forest trees and fine-tune these estimates with destructive sampling

and direct measurements of trees in similar forests and soils at settlement

sites adjacent to primary forest on our site. Because settlers completely clear

the forest for agriculture on 20-30% of their land, we will be able to use

destructive harvests for all DBH size classes and then estimate the biomass

contribution of bole extensions belowground. We will also use the plots on

settlements to directly measure vine and epiphyte biomass and relate this to

aboveground tree biomass.





We propose to quantify the

impact of soil texture and fertility gradients on above and belowground C and

nutrient stocks in local forests. We will use an empirical and a modeling

approach to examine the relationship of soil texture, especially clay content,

to patterns in above and belowground C and nutrient pools. Our site is

characterized by an Oxisol-Ultisol-Entisol association that is commonly found

across the Amazon basin. To examine the role of texture in greater detail, and

to test mechanisms by which texture influences the biogeochemistry of moist

lowland tropical forests, we will use the Century model to simulate the forest

on the different soil textural classes at our site. Our data will contribute

significantly to the robustness and reliability of existing allometric equations

for forest biomass across the Amazon.





In

addition, our site has a 10 year chronosequence of selective, conventional (CL)

and reduced impact logging (RIL). We propose to evaluate the We will use the

data from the studies mentioned above to measure the impact of CL and RIL on

above and belowground C and nutrient dynamics. The removal of trees inevitably

leads to nutrient export from the forest ecosystem. It is unclear to what extent

nutrients are distributed among topsoil, subsoil, litter layer, standing biomass

and streams by selective logging. We will collaborate with Richey et al. (CD-06)

to link our measurements of C and nutrient flows to first order streams with

local rivers. We are collaborating with Asner et al (LC-13) to evaluate canopy

damage and the hyperspectral signatures of various stages in the selective

logging chronosequence – from primary forest to the logging event to regrowth.

Our links with work in CD-06 and LC 13 will contribute to the assessments of the

impacts of selective logging on carbon management at the basin scale.

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