Forest Investment Account (FIA) - Forest Science Program
FIA Project Y102120

    Future vegetation structure and vertebrate distributions based on changes in moisture balance and temperature.
Project lead: Fred Bunnell (University of British Columbia)
Contributing Authors: Bunnell, Fred L.; Wells, Ralph W.; Moy, Arnold; Kremsater, Laurie L.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Climate change will have profound effects on the flora and fauna of British Columbia (Hebda 1997; Bunnell et al. 2005; Hamann and Wang 2006, Austin et al. 2008). This project anticipates those effects and describes them well enough that forestry and other land uses can respond and potentially mitigate and adapt to them. It builds on existing work (e.g., ibid., by improving our ability to project both vegetation and vertebrate response to changes in climate and by describing management responses most likely to reduce impacts. The project addresses two major forest management issues: 1) how are the broad patterns of community structure likely to change and how should silvicultural planning and practice respond, and 2) how is the capacity of the environment to sustain biodiversity likely to change and how should management practices respond. This latter issue is of direct interest to First Nations and the Province of B.C. This proposal covers Year 2 of a 3 year project. Year 1 emphasized acquiring, compiling and analyzing data sets. Year 2 develops, evaluates and refines models.

This project improves the projection of climate change impacts for BC by incorporating influences of evapotranspiration and moisture stress more effectively through collaboration with D. Spittlehouse (F090115: Improving access to high spatial-resolution climate data for climate change studies). Trevor Murdock (Pacific Climate Impacts Consortium =PCIC) is a partner in both this proposal and F090115 thus consolidating linkages into existing models. The proposed work calibrates biodiversity attributes such as vegetation structure, distribution of modern wetlands and vertebrate species to moisture balance values and other climatic parameters. The patterns are then projected into the future using climate model data. Plant community structure (physiognomy) rather than composition is a key focus, because structure is well linked to climate (Stephenson 1990) and vertebrate distribution (Bunnell et al. 1999). Moreover, physiognomy as reflected in BEC variant structure and composition is a useful predictor of vertebrate presence and absence (Bunnell et al. 2008). Greater confidence can be developed around changes in vegetation form (i.e. proportion of deciduous to coniferous species, coniferous vs deciduous dominants etc) than for each of the many species comprising the vegetation.

To more accurately predict vegetation responses we will project a moisture balance model (currently Summer Heat Moisture index, but in future likely Spitllehouse’s modification of Hargreaves & Samani 1982 and other climate parameters) to create maps with particular focus on intensity and length of the summer dry season. Moisture balance data will be related to vegetation (eco-plot) data available from Ministry of Forests, including, for selected regions, wetland types (see Mackenzie and Moran 2004) plus data documenting presence/absence of bird species collected within Y061014 to Y083014 and previous NSERC support to Bunnell. Using data of future climatic conditions from climate models available through PCIC, a range of future vegetation structure and wetland distribution patterns will be developed, and using GIS, displayed on maps.
By integrating of the projected climate changes, vegetation and vertebrates we examine two broadly related issues: 1) simple responses to landform at local scales, and 2) responses to vegetative structure more broadly. Two broad geometric responses are evident locally. The first results from the broadly conical shape of mountains: a linear shift in temperature boundary reduces the amount of alpine habitat proportional to the square of the linear change (Hebda 1997). Little can be done to reduce this impact, though its consequences can be broadly described. The second geometric impact results from the convex shape of ponds, lakes and wetlands. Again, a linear increase in evaporation reduces the area of suitable habitat at a rate more rapid than linear. That is particularly true of species reliant on emergent plants that have a narrow rooting zone. In this case, some mitigation may be possible by water management targeted to areas where effects are anticipated to be most profound or management efforts most likely to succeed.

Broad changes in vegetation structure have complex interactions with migratory species particularly birds. Birds, however, constitute the richest group of vertebrates and must be considered. The general model of bird response proposed by Bunnell et al. (2005) uses migratory categories as its major feature, and predicted the direction of response accurately in about 70% of cases for the few species that could then be tested. We will refine that model to allow prediction of changes in arrival and departure dates, changes in numbers over-wintering, range expansion, shifts in relative density within the province, and dates of clutch initiation. A major goal is to refine the model of general response and to test it over a broad range of bird species. That model makes predictions based largely on temperature. An obvious extension facilitated within this project is to include moisture more directly and to incorporate anticipated changes in vegetation structure in relation to moisture. Moisture availability is a strong determinant of vegetation structure and clearly influences wetlands.

As the richest group of vertebrates, birds provide the most fertile opportunities for testing: some species are strongly associated with hardwoods, others with conifers, some are near-obligate shrub nesters, others strongly associated with grasslands or with wetlands of different structural form and composition. The links between climate, the vegetation data base and vertebrates are strong. Although the first tests among vertebrates will be made using bird species, similar approaches will be explored for amphibians, some reptiles and mammals. The approach provides the potential to relate response of biota to changes in moisture and temperature resulting from climate change in general.

The future distribution and abundance of vegetation types and selected vertebrate species (initially birds) will be derived from projected climate derived from models and displayed on maps. The maps will show the character and extent of likely changes and help reveal potential impacts on silvicultural practices (e.g., shifts in the hardwood:conifer ratio), and provide insight into adaptations to these for sustaining efficient forestry, and fostering biodiversity. The magnitude, rate and location of change can help guide the choice and location of proactive measures to help sustain biodiversity.
Related projects:  FSP_Y091120FSP_Y113120


Executive Summary (62Kb)
Technical report: Testing bird relations with community structure (88Kb)
Vulnerability of wetlands to climate change in the Southern Interior Ecoprovince: a preliminary assessment (0.5Mb)

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Updated April 29, 2011 

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