Landscape-scale lidar analysis of aboveground biomass distribution in secondary Brazilian Atlantic Forest

Author(s)

Becknell, Justin M. ^{[1, 2]} ; Keller, Michael ^{[3, 4, 5]} ; Piotto, Daniel ^[6] ; Longo, Marcos ^[4] ; dos-Santos, Maiza Nara ^[4] ; Scaranello, Marcos A. ^[4] ; de Oliveira Cavalcante, Rodrigo Bruno ^[6] ; Porder, Stephen ^[1]

Affiliation

^[1] Brown Univ, Inst Brown Environm & Soc, Box 1951, Providence, RI 02912 - USA

^[2] Colby Coll, Environm Studies Program, 5352 Mayflower Hill, Waterville, ME 04901 - USA

^[3] CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 - USA

^[4] EMBRAPA CNPTIA, Campinas, SP - Brazil

^[5] US Forest Serv, Int Inst Trop Forestry, Rio Piedras, PR 00926 - USA

^[6] Univ Fed Sul Bahia, Ctr Formacao Ciencias Agroflorestais, Ilheus, BA - Brazil

• Document type: Journal article
• Source: Biotropica; v. 50, n. 3, p. 520-530, MAY 2018.
• Web of Science Citations: 1

Abstract

Secondary forests account for more than half of tropical forests and represent a growing carbon sink, but rates of biomass accumulation vary by a factor of two or more even among plots in the same landscape. To better understand the drivers of this variability, we used airborne lidar to measure forest canopy height and estimate biomass over 4529ha at Serra do Conduru Park in Southern Bahia, Brazil. We measured trees in 30 georeferenced field plots (0.25-ha each) to estimate biomass using allometry. Then we estimated aboveground biomass density (ABD) across the lidar study area using a statistical model developed from our field plots. This model related the 95th percentile of the distribution of lidar return heights to ABD. We overlaid this map of ABD on a Landsat-derived forest age map to determine rates of biomass accumulation. We found rapid initial biomass regeneration (similar to 6Mg/ha yr), which slowed as forests aged. We also observed high variability in both height and biomass across the landscape within forests of similar age. Nevertheless, a regression model that accounted for spatial autocorrelation and included forest age, slope, and distance to roads or open areas explained 62 and 77 percent of the landscape variation in ABD and canopy height, respectively. Thus, while there is high spatial heterogeneity in forest recovery, and the drivers of this heterogeneity warrant further investigation, we suggest that a relatively simple set of predictor variables is sufficient to explain the majority of variance in both height and ABD in this landscape. RESUMO Florestas secundarias constituem mais da metade das florestas tropicais e representam um importante sumidouro de carbono; entretanto taxas de acumulo de biomassa variam por fator superior a dois mesmo entre parcelas numa mesma paisagem. Para compreender quais fatores controlam esta variabilidade, utilizamos lidar aerotransportado para medir altura de dossel florestal e estimar biomassa em 4529ha no Parque Estadual da Serra do Conduru, Bahia, Brasil. Nos medimos arvores em 30 parcelas georreferenciadas (0.25-ha cada) para estimar biomassa com equacoes alometricas. Posteriormente, estimamos densidade de biomassa acima do solo (ABD) na area sobrevoada utilizando um modelo estatistico desenvolvido a partir das parcelas de campo. Este modelo relacionou o 95 degrees percentil da distribuicAo de alturas de retorno do lidar a ADB. Este mapa de ABD foi sobreposto a um mapa de idades de floresta baseado no Landsat, para determinar taxas de acumulo de biomassa. Verificaram-se taxas de regeneracAo inicialmente rapidas (similar to 6 Mg/ha ano), que diminuiram conforme as florestas envelheceram. Observamos tambem grande variabilidade em altura e biomassa ao longo da paisagem entre florestas de idade semelhantes. Apesar disto, um modelo de regressAo considerando autocorrelacAo espacial e incluindo idade da floresta, declividade e distancia ate estradas ou areas abertas explicou 62% e 77% da variacAo em escala de paisagem para ABD e altura do dossel, respectivamente. Embora haja grande heterogeneidade espacial em recuperacAo florestal, e determinantes desta heterogeneidade requeiram investigacoes adicionais, nossos resultados sugerem que conjuntos relativamente simples de variaveis preditoras sAo suficientes para explicar grande parte da variancia de altura e ABD nesta paisagem. (AU)

• FAPESP's process: 15/07227-6 - Long term effects of forest degradation on carbon cycling in Amazonia
• Grantee: Marcos Longo
• Support type: Scholarships in Brazil - Post-Doctorate