Predictive models of forest dynamics

Computational Ecology and Environmental Science Group, Microsoft Research, Cambridge, UK.
Science (Impact Factor: 31.48). 07/2008; 320(5882):1452-3. DOI: 10.1126/science.1155359
Source: PubMed

ABSTRACT Dynamic global vegetation models (DGVMs) have shown that forest dynamics could dramatically alter the response of the global climate system to increased atmospheric carbon dioxide over the next century. But there is little agreement between different DGVMs, making forest dynamics one of the greatest sources of uncertainty in predicting future climate. DGVM predictions could be strengthened by integrating the ecological realities of biodiversity and height-structured competition for light, facilitated by recent advances in the mathematics of forest modeling, ecological understanding of diverse forest communities, and the availability of forest inventory data.

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    ABSTRACT: Human activities are driving climatic warming and more frequent extreme weather, persistent throughout the recent warming hiatus. The effects of these changes on vegetation phenology remains poorly understood. Forest phenology studies typically focus on the length of the growing season and related changes in carbon uptake. Changes to tree regeneration remain uncertain, yet carry multiple climate feedback pathways. Dominant tree species drive forest biogeochemistry, with species varying in nutrient cycling, soil biota, biogenic volatile organic compound emissions, and productivity under drought, while drought conditions are likely to increase in severity. Regeneration processes underlie forest dynamics, the largest source of biosphere model uncertainty. We applied a process-based tree germination and establishment model to a study area in western Canada in order to estimate the effects of 20th and 21st century climatic change on regeneration in northern forests. We parameterized the model for 21 major tree species using biophysical parameters derived from the literature. We classified daily weather station and soils data for fourteen biogeoclimatic regions within the study area for three historical 30-year periods and the most recent decade: 1923-1952, 1953-1982, 1983-2012, and 2003-2012. We simulated the effects of changing temperature and precipitation conditions on germination and establishment processes for 21 tree species, fourteen regions, and four time periods. We found that regeneration conditions diminished across the 1923 to 2012 period, driven by soil water limitations. While regeneration conditions improved during the recent warming hiatus, a downward trend persists at a multi-decadal scale. In contrast to studies indicating regenerational improvements in higher latitudes and elevations, with disequilibrium in lowland forests due to a higher velocity of climatic change, we found that a soil water balance shift drove species downhill, supporting a recent study. As the climate continues to warm, we anticipate that changes to disturbance regimes will unlock the lagged regenerational response of northern forests currently in climatic disequilibrium, producing a complex network of climatic feedbacks.
    AGU Fall Meeting, San Francisco, CA, USA; 12/2014
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    ABSTRACT: Allometry and growth rates of 8 forest species in the UK. The data were collected from two United Kingdom woodlands - Wytham Woods and Alice Holt. Here we present data from 582 individual trees of eight taxa in the form of summary variables. In addition the raw data files containing the variables from which the summary data were obtained. Large sample sizes with longitudinal data spanning 22 years make these datasets useful for future studies concerned with the way trees change in size and shape over their life-span. The allometric relationships include (1) trunk diameter, (2) height, (3) crown height, (4) crown radius and (5) trunk radial growth rate to (A) the light environment of each tree and (B) diameter at breast height.
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    ABSTRACT: Forest landscape models are effective tools for exploring the effects of long-term and large-scale landscape processes such as seed dispersal, fire, and timber harvest. These models have been widely used for about a decade, and although significant advances in theory and technology have been incorporated into their development, evaluating the veracity of simulated results from forest landscape models remains challenging. In this study, we evaluated simulated forest succession and the effects of simulated fire and harvest by a spatially explicit forest landscape model (LANDIS PRO), initialized using forest inventory data (second and third tier data from years 2000 and 2010). Our results suggested that the initialized forest landscape constructed from the year 2000 forest inventory data adequately represented the forest composition and structure from that year. The simulated density and basal area from year 2010 adequately represented the forest inventory data from that year at landscape scales. Our results indicated that the simulated fire and harvest effects were comparable to the field data (measured density and basal area). Results in this study quantified the near-term reliability and confidence of the model as well as prediction uncertainties.
    Ecological Modelling 11/2014; 297. DOI:10.1016/j.ecolmodel.2014.10.040 · 2.33 Impact Factor


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