Reframing tropical savannization: linking changes in canopy structure to energy balance alterations that impact climate

Ecosphere

Rafael Leandro deAssis¹  José Luis Camargo¹  Susan Aragón²  Abigail L. S. Swann³  Scott R. Saleska⁴  Danilo Roberti Alves deAlmeida⁵  Scott C. Stark⁶  Marielle N. Smith⁶  David M. Minor⁶  Gabriel deOliveira⁷  R. Cosme Oliveira⁸  José Mauro S. Moura⁹  Rodrigo daSilva^1,10  Luiz E. O. C. Aragão^1,11  David D. Breshears^1,12  Juan Camilo Villegas^1,12  Darin J. Law^1,12 

[1] Biological Dynamics of Forest Fragments Project, PDBFF Instituto Nacional de Pesquisas da Amazônia Av. André Araujo, 2936 ‐ Petrópolis Manaus Amazonas69067‐375Brazil;Center of Integrated Studies of Amazonian Biodiversity (CENBAM) National Institute of Amazonian Research (INPA) Manaus Amazonas69067‐375Brazil;Department of Atmospheric Sciences and Department of Biology University of Washington Seattle Washington98195USA;Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona85721USA;Department of Forest Sciences “Luiz de Queiroz” College of Agriculture University of São Paulo (USP/ESALQ Piracicaba São Paulo Brazil;Department of Forestry Michigan State University East Lansing Michigan48824USA;Department of Geography and Planning University of Toronto Toronto OntarioM5S 3G3Canada;Embrapa Amazonia Oriental Santarem Pará68020‐640Brazil;Interdisciplinary Training Center Federal University of Western Para Santarém Pará68040‐255Brazil;Laboratório de Física e Química da Atmosfera ‐ Bloco 29 Rua Vera Paz Santarém Pará68040‐260Brazil;Remote Sensing Division National Institute for Space Research (INPE) São José dos Campos Brazil;School of Natural Resources and the Environment University of Arizona Tucson Arizona85721USA;

关键词: Amazon;    climate change;    Earth System Models;    energy balance;    forest transitions;    lidar;   

DOI  :  10.1002/ecs2.3231

来源: DOAJ

【 摘 要 】

Abstract Tropical ecosystems are undergoing unprecedented rates of degradation from deforestation, fire, and drought disturbances. The collective effects of these disturbances threaten to shift large portions of tropical ecosystems such as Amazon forests into savanna‐like structure via tree loss, functional changes, and the emergence of fire (savannization). Changes from forest states to a more open savanna‐like structure can affect local microclimates, surface energy fluxes, and biosphere–atmosphere interactions. A predominant type of ecosystem state change is the loss of tree cover and structural complexity in disturbed forest. Although important advances have been made contrasting energy fluxes between historically distinct old‐growth forest and savanna systems, the emergence of secondary forests and savanna‐like ecosystems necessitates a reframing to consider gradients of tree structure that span forest to savanna‐like states at multiple scales. In this Innovative Viewpoint, we draw from the literature on forest–grassland continua to develop a framework to assess the consequences of tropical forest degradation on surface energy fluxes and canopy structure. We illustrate this framework for forest sites with contrasting canopy structure that ranges from simple, open, and savanna‐like to complex and closed, representative of tropical wet forest, within two climatically distinct regions in the Amazon. Using a recently developed rapid field assessment approach, we quantify differences in cover, leaf area vertical profiles, surface roughness, albedo, and energy balance partitioning between adjacent sites and compare canopy structure with adjacent old‐growth forest; more structurally simple forests displayed lower net radiation. To address forest–atmosphere feedback, we also consider the effects of canopy structure change on susceptibility to additional future disturbance. We illustrate a converse transition—recovery in structure following disturbance—measuring forest canopy structure 10 yr after the imposition of a 5‐yr drought in the ground‐breaking Seca Floresta experiment. Our approach strategically enables rapid characterization of surface properties relevant to vegetation models following degradation, and advances links between surface properties and canopy structure variables, increasingly available from remote sensing. Concluding, we hypothesize that understanding surface energy balance and microclimate change across degraded tropical forest states not only reveals critical atmospheric forcing, but also critical local‐scale feedbacks from forest sensitivity to additional climate‐linked disturbance.

【 授权许可】

Unknown