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Archive for the ‘Forests’ Category
Wednesday, January 30th, 2008
In June 2006 the China Natural Science Foundation and the International Association of Landscape Ecology sponsored an international workshop of forest landscape modelling. The aim of the workshop was to facilitate a discussion on the progress made in the theory and application of forest landscape models. A special issue of Forest Ecology and Management, entitled Forest Landscape Modeling – Approaches and Appplications [Vol. 253, Iss. 3], presents 12 papers resulting from that meeting. In their editorial, He et al. summarise the papers, organising them into three sections that describe current activities in forest landscape modelling: (1) effects of climate change on forest vegetation, (2) forest landscape model applications, and (3) model research and development.
The LANDIS model is used in several of the papers on climate and human management of forest systems. Advances in the representation of processes that propagate spatially, including fire and seed dispersal, are discussed in several of the papers examining model research and development. He et al. conclude their editorial by reiterating why landscape models are a vital tool for better understanding and managing forested regions of the world:
The papers represented in the special issue of forest landscape modeling highlight the advances and applications of forest landscape models. They show that forest landscape models are irreplaceable tools to conduct landscape-scale experiments while physical, financial, and human constraints make real-world experiments impossible. Most of the results presented in this issue would not have been possible without the use of forest landscape models. Forest landscape modeling is a rapidly developing field. Its development and application will continually be driven by the actual problems in forest management planning and landscape-scale research. We hope that the papers contained in this special issue will serve both researchers and managers who are struggling to incorporate large-scale and long-term landscape processes into their management planning or research.
This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Ecological, Forests, Landscapes, Modelling | Comments Off
Sunday, October 28th, 2007
A few pictures from our trip to the UP study area this past week.
 The fall was almost over. We were out on a recce to find sites for an experiment we’re setting up over the next couple of weeks to examine the impact of deer browse on seedlings of various conifer species.
 We want to locate our seedling planting on both state and commercial lands – cutting had recently finished at this commercial site.
 We also visited a deer exclosure set up to examine tree regeneration in the absence of deer browse (similar in many ways to our experiment). It’s not the best picture, but the effects of 12 years of protection can be seen – very little regeneration on the left of the fence but evidence of green juveniles on the right. These effects haven’t been quantified at this site but by sight alone there’s clearly difference outside s inside the exclosure.
 Finally, not all the leaves had fallen. We were a couple of weeks late for the real colours, but some remained down on the Lake Michigan coastline.
This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Ecological, Forests, MichiganUP, Photography | Comments Off
Friday, August 3rd, 2007
We plan to use the Forest Vegetation Simulator (FVS), developed by the USFS over the previous couple of decades, in our ecological-economic model of a managed forest landscape. This week I’ve been thinking a lot about how best to link a representation of white-tailed deer browse with the FVS.
Two good examples I’ve found of the modelling of forest disturbance using FVS are the Fire and Fuels Extension (FFE) developed at the USFS Rocky Mountain Research Station in collaboration with other parties, and the Westwide Pine Beetle Model developed by the Forest Health Technology Enterprise Team (FHTET).
The Fire and Fuels Extension to the Forest Vegetation Simulator (FFE-FVS) links the existing FVS, models that represent fire and fire-effects, and fuel dynamics and crowning submodels. The overall model is currently calibrated for northern Idaho, western Montana, and northeastern Washington. More details on the FFE-FVS can be found here, where you can also download this video about the extension:
[youtube=http://www.youtube.com/watch?v=w9oEW7rQgZM]
The Westwide Pine Beetle Model simulates impacts of mountain beetle (Dendroctonus ponderosae Hokpins), western pine beetle (D. brevicomis Leconte), and Ips species for which western pines are a host. The model simulates the movement of beetles between the forest stands in the landscape using the Parallel Processor Extension (PPE) to represent multiple forest stands in FVS.
A recent paper by Ager and colleagues in Landscape and Urban Planning presents work that links both the FFE and the WPBM to FVS using the PPE:
We simulated management scenarios with and without thinning over 60 years, coupled with a mountain pine beetle outbreak (at 30 years) to examine how thinning might affect bark beetle impacts, potential fire behavior, and their interactions on a 16,000-ha landscape in northeastern Oregon. We employed the Forest Vegetation Simulator, along with sub-models including the Parallel Processing Extension, Fire and Fuels Extension, and Westwide Pine Beetle Model (WPBM). We also compared responses to treatment scenarios of two bark beetle-caused tree mortality susceptibility rating systems. As hypothesized, thinning treatments led to substantial reduction in potential wildfire severity over time. However, contrary to expectations, the WPBM predicted higher bark beetle-caused mortality from an outbreak in thinned versus unthinned scenarios. Likewise, susceptibility ratings were also higher for thinned stands. Thinning treatments favored retention of early seral species such as ponderosa pine, leading to increases in proportion and average diameter of host trees. Increased surface fuel loadings and incidence of potential crown fire behavior were predicted post-outbreak; however, these effects on potential wildfire behavior were minor relative to effects of thinning. We discuss apparent inconsistencies between simulation outputs and literature, and identify improvements needed in the modeling framework to better address bark beetle-wildfire interactions.
Whilst I’m still in the early stages of working out how our model will all fit together, it seems like an approach that takes a similar approach will be suitable for our purposes. We’ll need to develop a model that is able to represent the spatial distribution of the deer population across the landscape and that can specify the impact of those deer densities on the vegetation for given age-height classes (for each veg species). This model would likely then be linked with FVS via the the PPE. So concurrently over the next few months I’m going to be working on developing a model of deer density and browse impacts, coding this model into a structure that will link with FVS-PPE, and acquiring and developing data for model initialization.
Reference
Ager, A.A., McMahan, A., Hayes, J.L. and Smith, E.L. (2007) Modeling the effects of thinning on bark beetle impacts and wildfire potential in the Blue Mountains of eastern Oregon Landscape and Urban Planning 80:3 p.301-311
This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Ecological, Forests, MichiganUP, Modelling, Wildfire | Comments Off
Monday, July 30th, 2007
An email sitting in my inbox this morning directed me toward an article in the latest issue of Landscape Ecology that directly addresses one of the issues I touched on in Saturday’s post; the ‘Maple-ization’ of the western UP Northern Hardwood forests via selective forest harvest and the resulting feedbacks with whitetailed deer populations.
Lisa Schulte and colleagues examined the regional-scale impacts of human land use in the northern U.S. Great Lakes region. They found an overall loss of forestland, lower forest species diversity, functional diversity, and structural complexity compared to pre-Euro-American settlement forests.
Generally, they found evidence of shifts from evergreen conifer (-27.0%) to deciduous hardwood (+22.8%) species between pre-Euro-American settlement and the present time. Specifically, they found marked increases in Aspen (+12.8%) and Maple (+10.1%) and decreases in Pine (-17.5%) and Hemlock (-11.3%) across the area as a whole. However, increases in northern hardwood species were not uniform, and Beech and Birch have decreased (~4% each).
A figure from their paper (above) maps the change in ecoregion characteristics for (A) the extent of open vegetation, (B) dominance of conifers, (C) dominance of aspen (combined Populus tremuloides and P. grandidentata), and (D) dominance of maple (combined Acer saccharum and A. rubrum).
In their discussion the authors (p.1100-01) go on to describe the issues present in our study area;
“Although forests have largely been reestablished across northern portions of the region [following destructive logging in the late 19th century], these forests are on a new trajectory of change rather than recovery toward pre-Euro-American conditions . We attribute lack of recovery to legacies associated with the initial, severe land use conversion, the persistent over-abundance of a keystone herbivore (white-tailed deer), and related management practices that are inattentive to processes that historically promoted vegetation diversity within the region.
…
The excessive deer abundance at present is a feedback of regional forest management; whitetailed deer at high densities are now regarded as a major threat to forest biodiversity and regeneration in the region and elsewhere (Rooney et al. 2004). The commercial logging that is now the most frequent and widespread forest disturbance across the region largely fails to mimic either the local or landscape effects of the historically prevalent disturbances of windthrow and fire (Mladenoff et al. 1993; Scheller and Mladenoff 2002). Rather, current practices of aspen clearcutting and single-tree selection in maple stands continues to foster this divergence and simplification of the forests by largely favoring their regeneration over a greater diversity of tree species (Crow et al. 2002).”
As I discussed just the other day, we’ll be using the model we’re currently developing to examine spatial scenarios directly related to this issue. For example one aim is to examine scenarios of forest management that allow the recreation of historical herbivore disturbance via spatial patterns of vegetation whilst ensuring the future economic sustainability of the forests.
Reference
Schulte, L.A., Mladenoff, D.J., Crow, T.R., Merrick, L.C., and Cleland, D.T. (2007) Homogenization of northern U.S. Great Lakes forests due to land use Landscape Ecology 22:7 1089-1103
This work by James D.A. Millington is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.
Posted in Academic, Ecological, Forests, Landscapes, MichiganUP | Comments Off
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