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.

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.This study was funded through a grant from the Cambridge Conservation Initiative Collaborative Fund entitled “Applications of airborne remote sensing to the conservation management of a West African National Park”. T.J. was funded in part through NERC grant NE/K016377/1. A.C.S. was funded in part through a grant from the Percy Sladen Memorial Fund.This is the final version of the article. It first appeared from Wiley via https://doi.org/10.1002/ece3.217

Contributions of a global network of tree diversity experiments to sustainable forest plantations

status: publishe

Data from: Beyond shading: litter production by neighbours contributes to overyielding in tropical trees

The influence of biodiversity on ecosystem functioning is now well established. However, our ability to predict the ecological consequences of biodiversity changes remains limited by our poor understanding of the mechanisms underlying biodiversity effects. We disentangled the contributions of light competition and residual neighbourhood interactions in a ten-year-old biodiversity experiment with tropical trees that display overyielding, i.e., higher community-level yields in mixtures compared with monocultures. We developed models of individual tree growth that partition the effects of neighbouring trees into shading and residual effects assumed to reflect primarily belowground interactions. These models reject the hypothesis that reduced light competition in mixtures is the only mechanism driving overyielding. After factoring out the effects of shading, litter production by neighbours was a far better predictor of tree growth than traditional crowding indices and contributed to overyielding by producing pairwise interactions that ranged from competitive to facilitative, but which on average concentrated competition within species. Consistent with litter-mediated biodiversity effects, the magnitude of overyielding increased over time. Our results provide evidence for diversity effects extending beyond that of light and reveal the neglected role of litter-mediated interactions among trees

Niche and fitness differences relate the maintenance of diversity to ecosystem function: comment.

The relationship between biodiversity and ecosystem functioning (BEF) has been one of the most vibrant research fields in ecology and environmental sciences over the past two decades. Hundreds of experiments have now manipulated species diversity to test its effects on a wide range of ecosystem properties. Methods that partition the effect of functional complementarity between species from that of selection for species with particular traits have been instrumental in clarifying the results of these experiments and in resolving debates about potential underlying mechanisms (Loreau and Hector 2001, Cardinale et al. 2007). Relatively few studies, however, have sought to disentangle the actual biological mechanisms at work in the effects of biodiversity on ecosystem functioning. Yet theory shows that different coexistence mechanisms can lead to different BEF relationships (Mouquet et al. 2002). Understanding the mechanisms that drive the functional consequences of biodiversity and their connections with those that determine the maintenance of biodiversity is key to making BEF research more predictive and more relevant to natural, non-experimentally manipulated ecosystems (Loreau 2010). The recent theoretical study by Carroll, Cardinale, and Nisbet (2011; hereafter CCN) makes a valuable contribution toward the goal of linking the maintenance of diversity and its functional consequences. CCN use MacArthur’s (1972) classical consume

Tree census data

These data are yearly measurements of status, height and diameter on individual trees from the experimental plantation of the Sardinilla project. The Sardinilla project is a biodiversity experiment with tropical trees, that is a replacement series experiment with plots containing either 1, 3 or 6 species. The Sardinilla Project is part of Treedivnet (http://www.treedivnet.ugent.be) a global network of nine similar biodiversity tree plantations including boreal, temperate and tropical forest experiments. See: http://biology.mcgill.ca/faculty/potvin/sardinilla_obj.html. Data from years 2002 to 2006 are provided. Seedlings were planted in July 2001. Measurements were made late December (of the previous year indicated in the columns), in January or in February (of the year indicated in the columns). Metadata are included in a readme file and in a separate sheet in the xls file

La diversité de perceptions des sols par les gestionnaires

La diversité de perceptions des sols par les gestionnaires. 12. Journées d'Etude des Sol