Bio


My work assesses sustainability of afforestation and plantation forestry as part of the Jackson lab. I am interested in the interactions of plants, soils, and people, and in answering ecological questions to understand how humans can participate in and contribute to healthy ecosystems.

Current Research and Scholarly Interests


I am interested in ecosystem responses to disturbance and the interactions between vegetation, soils, and people. My general research goal is to address ecological questions related to land use to help humans participate in healthy ecosystems. Currently, I study the long-term effects of tree-planting and plantation forestry on soil nutrients and plant productivity. My research focuses on the extreme case of eucalyptus plantations in Southeastern Brazil, where rapid tree growth yields efficient pulp and paper production and potential bioenergy feedstock, as well as concerns about depletion of water and nutrients from the soil. I combine remote sensing, soil chemistry, and statistical techniques to assess aspects of plantation sustainability from the plot scale to an entire region.

Lab Affiliations


All Publications


  • Management intensification maintains wood production over multiple harvests in tropical Eucalyptus plantations. Ecological applications : a publication of the Ecological Society of America McMahon, D. E., Jackson, R. B. 2019: e01879

    Abstract

    Plantation forestry, in which trees are grown as a crop, must maintain wood production over repeated harvest cycles (rotations) to meet global wood demands on a limited land area. We analyze 33 years of Landsat observations across the world's most productive forestry system, Eucalyptus plantations in southeastern Brazil, to assess long-term regional trends in wood production. We apply a simple algorithm to time series of the vegetation index NIRv in thousands of Eucalyptus stands to detect the starts and ends of rotations. We then estimate wood production in each identified stand and rotation, based on a statistical relationship between NIRv trajectories and inventory data from three plantation companies. We also compare Eucalyptus NIRv with that of surrounding native vegetation to assess the relative influence of management and environment on plantation productivity trends. Across more than 3500 stands with three complete rotations between 1984 and 2016, modeled wood volume decreased significantly between the first and second rotation, but recovered at least partially in the third; mean wood volumes for the three rotations were 262, 228, and 247 m3 ha-1 . This nonlinear trend reflects intensifying plantation management, as rotation length decreased by an average of 15% (decreasing wood volume per rotation) and NIRv proxies of tree growth rates increased (increasing volume) between the first and third rotation. However, NIRv also increased significantly over time in unmanaged vegetation around the plantations, suggesting that environmental trends affecting all vegetation also contribute to sustaining wood production. Management inputs will likely continue to be important for maintaining wood production in future harvests. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/eap.1879

    View details for PubMedID 30838713

  • A global meta-analysis of soil phosphorus dynamics after afforestation NEW PHYTOLOGIST Deng, Q., McMahon, D. E., Xiang, Y., Yu, C., Jackson, R. B., Hui, D. 2017; 213 (1): 181-192

    Abstract

    Afforestation significantly affects soil chemistry and biota, but its effects on the potentially growth-limiting nutrient phosphorus (P) had not to our knowledge been analyzed globally. We conducted a comprehensive meta-analysis of 220 independent sampling sites from 108 articles to evaluate global patterns and controls of soil P change following afforestation. Overall, total P concentration decreased by 11% and total P stock by 12% in the top 20 cm of mineral soil following afforestation, with no change in available P. Time since afforestation had no consistent effect on total P, while available P tended to increase with time. Prior land cover was the most influential factor for soil P change after afforestation, with available P increasing on native vegetation but decreasing on cropland. Afforestation increased available P by 22% without decreasing total P on formerly 'degraded' land, but depleted total P by 15% at nondegraded sites. Climate also influenced soil P response to afforestation, with larger P loss in the tropics. Afforestation did not appear to directly induce P limitation, as available P only decreased on cropland. However, substantial declines in total P may drive tropical plantations toward greater P limitation as the capacity to replenish available P decreases.

    View details for DOI 10.1111/nph.14119

    View details for Web of Science ID 000389184600020

    View details for PubMedID 27477387

  • Tree community shifts and Acorn Woodpecker population increases over three decades in a Californian oak woodland CANADIAN JOURNAL OF FOREST RESEARCH McMahon, D. E., Pearse, I. S., Koenig, W. D., Walters, E. L. 2015; 45 (8): 1113-1120