Forest Investment Account (FIA) - Forest Science Program
FIA Project Y102045

    Measurement and Modelling of Disturbance Impacts on Site Hydrology and Productivity in British Columbia's Southern Interior
 
Project lead: Darryl Carlyle-Moses (Thompson Rivers University)
Contributing Authors: Sanders, P.W.; Carlyle-Moses, Darryl E.; Pillar, Andrew; McKee, Adam J.
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Description:
As of 2006, Provincial Aerial Overview of Forest Health surveys indicated that approximately 42 % of all merchantable pine in British Columbia had been killed as a consequence of the current mountain pine beetle (MPB) epidemic (Walton et al., 2007). Large-scale stand mortality is expected to continue due not only to the MPB infestation, with 77 % of all merchantable pine projected to be lost to this infestation by 2014 (Walton et al., 2007), but also commercial harvesting activities, and wildfires - which are predicted to increase in frequency in the region as a result of global climatic change (BC Ministry of Water, Land and Air Protection, 2004). The magnitude and geographic extent of forest disturbance in the province has raised important socio-economic and natural resources management concerns, including the impact of disturbance regimes will have on site hydrology and productivity.

Water and energy partitioning by forested landscapes is influenced in no small part by the biophysical characteristics exhibited by that cover, including, for example, canopy cover fraction, canopy volume and stand height (Oke, 1987). Removal of forest canopy generally leads to increased soil moisture and soil temperatures and extends growing season lengths (Bhatti et al., 2000). However, the magnitude and duration of impacts on soil moisture and temperature are dependent on the type and degree of soil disturbance, residual ground cover, and the time required for vegetation to become established and the characteristics of that re-growth (Mahendrappa and Kingston, 1994; Spittlehouse, 2007).
Intuitively, these post-disturbance site characteristics are, in large part, not only a function of the magnitude of disturbance, but also on the type of disturbance itself. For example, although the casual observer may view stands affected by wildfire and by MPB similarly, in that both disturbances kill trees that comprise the overstorey, the post-disturbance understorey plant composition and the biophysical character of the forest floor and soil matrix will differ appreciably between the two stands.

The dissimilarities in site characteristics under different disturbance scenarios may result in important contrasts in the manner water and energy are partitioned and thus on the productivity and future growing conditions of tree species. Currently, any predictions about how hydrologic and ecosystem processes will differ under different disturbance regimes is largely speculative. The ability to predict such impacts is, however, not only of academic interest. Research is needed to provide forest and watershed managers, policy makers, First Nations groups and research scientists with the quantitative information necessary to evaluate the impact different disturbance regimes have on site water availability and temperature regimes and thus the establishment, growth and health of regenerating stands. In addition, little is known about the hydrological effects of partial versus complete stand mortality or of the time to reach hydrologic recovery in these areas once regeneration begins.

A comprehensive field campaign near Mayson Lake on the Bonaparte Plateau in south-central British Columbia has been established in order to address key gaps in our understanding of disturbance impacts on site hydrology and productivity. Specific research questions to be addressed include: i) how do canopy, forest floor and soil rooting zone hydrologic and heat balances differ under different disturbance regimes and stages of re-growth; ii) how do these differences impact soil moisture, soil temperature and related site productivity; and iii) how well can these ecohydrological processes be simulated using forest hydrology models and how can the results of such simulation exercises be extrapolated in both space and time?

Growing-season water and heat balances will be derived within grey-attack MPB stands, stands affected by the 2003 McClure wildfire, and stands at various stages of regeneration after harvesting. Mayson Lake is also the site of a long-term snow hydrology research program and a study examining the impact of MPB on the annual forest water balance (see Redding et al., 2007). The approach to be used in order to determine disturbance related changes in site hydrology and productivity includes field measurements of growing-season water and heat fluxes over a two-year period and the use and evaluation of water and heat balance models in simulating soil moisture contents and temperature in the rooting zone. Future forest deterioration and re-growth of the study stands will be simulated and, coupled with the results of the proposed study, will be used to determine the time for stands to recover hydrologically.

It is anticipated that the results of the project will be used to guide future policy and practice regarding the planning of forest operations so that optimum timber harvests coupled with minimal environmental impacts can be realized on areas once affected by disturbance. Project-derived results will also help researchers interested in addressing the impacts of disturbance and subsequent re-growth on nitrification (e.g., Powers, 1990), soil biota (e.g., Berch et al., 2007) and ground water and streamflow chemistry (e.g., McEachern et al., 2005). The proposed research also addresses three of the research priorities outlined by Hélie et al. (2005): i) MPB impacts on soil moisture storage; ii) the impacts on interception loss; and iii) the impacts on evapotranspiration. The project will involve the participation of graduate and senior undergraduate students.
Related projects:  FSP_Y091045

    Deliverables:

Final technical report (1.0Mb)
Poster - Western Div. Can. Assoc. Geog., March 2010 (1.4Mb)
TRU Undergraduate Research Conference Presentation (0.6Mb)
Western Div. Can. Assoc. Geog. Presentation, March 2010: Throughfall variability at Mayson Lake Forest stands (1.9Mb)
Stemflow article in Link vol. 11(2) (0.2Mb)

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Updated August 16, 2010 

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