title: Drivers of aboveground wood production in a lowland tropical forest of West Africa: teasing apart the roles of tree density, tree diversity, soil phosphorus, and historical logging.
abstract: Tropical forests currently play a key role in regulating the terrestrial carbon cycle and abating climate change by storing carbon in wood. However, there remains considerable uncertainty as to whether tropical forests will continue to act as carbon sinks in the face of increased pressure from expanding human activities. Consequently, understanding what drives productivity in tropical forests is critical. We used permanent forest plot data from the Gola Rainforest National Park (Sierra Leone) - one of the largest tracts of intact tropical moist forest in West Africa - to explore how (1) stand basal area and tree diversity, (2) past disturbance associated with past logging, and (3) underlying soil nutrient gradients interact to determine rates of aboveground wood production (AWP). We started by statistically modeling the diameter growth of individual trees and used these models to estimate AWP for 142 permanent forest plots. We then used structural equation modeling to explore the direct and indirect pathways which shape rates of AWP. Across the plot network, stand basal area emerged as the strongest determinant of AWP, with densely packed stands exhibiting the fastest rates of AWP. In addition to stand packing density, both tree diversity and soil phosphorus content were also positively related to productivity. By contrast, historical logging activities negatively impacted AWP through the removal of large trees, which contributed disproportionately to productivity. Understanding what determines variation in wood production across tropical forest landscapes requires accounting for multiple interacting drivers - with stand structure, tree diversity, and soil nutrients all playing a key role. Importantly, our results also indicate that logging activities can have a long-lasting impact on a forest's ability to sequester and store carbon, emphasizing the importance of safeguarding old-growth tropical forests.
authors: Forest Ecology and Conservation Group Department of Plant Sciences University of Cambridge Downing Street Cambridge CB2 3EA UK.
authors: Tommaso
authors: T
authors: Jucker
authors: RSPB Centre for Conservation Science The Lodge Sandy Bedfordshire SG19 2DL UK; Department of Biology Center for Macroecology, Evolution and Climate University of Copenhagen Universitetsparken 15DK-2100 Copenhagen Denmark.
authors: Aida Cuni
authors: AC
authors: Sanchez
authors: RSPB Centre for Conservation Science The Lodge Sandy Bedfordshire SG19 2DL UK; A Rocha International 89 Worship Street London EC2A 2BF UK.
authors: Jeremy A
authors: JA
authors: Lindsell
authors: Department of Geography University of Cambridge Downing Place Cambridge CB2 3EN UK.
authors: Harriet D
authors: HD
authors: Allen
authors: Department of Geography University of Cambridge Downing Place Cambridge CB2 3EN UK.
authors: Gabriel S
authors: GS
authors: Amable
authors: Forest Ecology and Conservation Group Department of Plant Sciences University of Cambridge Downing Street Cambridge CB2 3EA UK.
authors: David A
authors: DA
authors: Coomes
keywords: Determinants of plant community diversity and structure; Sierra Leone; effective number of species; forest productivity; packing density; selective logging; soil nutrients; structural equation modeling