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My current research involves characterizing the disturbance regime of the mountain pine beetle in Colorado forests, and I am also a spatial analyst in a project that seeks to characterize spatial patterns of willingness to pay for marine mammals in the US.

 

Jarvis, D. Kulakowski, D., Rogan, J. Sub-stand spatial and temporal synchrony and fuel consequences of mountain pine beetle outbreak in northern Colorado

In the years during and immediately following outbreak, any increase in fire hazard will most likely be associated with the presence of dead needles, whose foliar moisture content, known to be a key factor in the propagation of crown fire (Van Wagner 1977), is lower than that of live needles. However, once trees begin losing needles and entering the grey stage, canopy fire hazard decreases due to needle drop. The effects of reduced canopy bulk density in reducing canopy fuels are thought to outweigh the effects of reduced foliar moisture content in increasing fire hazard (Simard et al. 2010). Thus, theoretically the overall effect of an outbreak on fire hazard at the stand scale should be a function of the relative proportions of trees in the green- and red-attack stages versus the grey attack stage. It logically follows that this proportion, in turn, should be a function the spatial synchrony of an outbreak. In this study, we use fine-spatial resolution aerial imagery to classify lodgepole pine forest into green trees, red-attack, and grey-attack. This information is then used in spatial analysis to determine spatial and temporal synchrony and hence fire hazard variability at the sub-stand scale.

 

Jarvis, D. Kulakowski, D. Long-term fuel consequences of mountain pine beetle outbreak on surface fuel hazard

This project seeks to characterize the surface fuel complex in stands affected by historic mountain pine beetle outbreak and compare this to similar stands not affected by previous mountain pine beetle outbreak.   

 

Gill, N.S., Jarvis, D., Veblen, T.T., Pickett, S.T.A., Kulakowski, D.  Is initial post-disturbance regeneration indicative of longer-term trajectories?

The ability to estimate and model future vegetation dynamics is a central focus of contemporary ecology and is essential for understanding future ecological trajectories. It is therefore critical to understand when the influence of initial post-disturbance regeneration versus stochastic processes dominate long-term post-disturbance ecological processes.  Often, conclusions about post-disturbance dynamics are based upon initial regeneration in the years immediately after disturbances.  However, the degree to which initial post-disturbance regeneration indicates longer-term trends is likely to be contingent on the types, intensities, and combinations of disturbance as well as pre-disturbance ecosystem structure and composition.  Our relatively limited understanding of why initial post-disturbance regeneration is sometimes a poor predictor of future ecosystem trajectories represents a critical gap in post-disturbance ecological forecasting. Here we studied the composition and density of regeneration of tree species following wind blowdown in 1997, wildfire in 2002, and compounded disturbances by blowdown and wildfire in subalpine forests of Colorado from 2003-2015.  We examined regeneration in 180 permanent plots across 12 sites in 2003, 2010, and 2015. At sites that were blown down but not burned, regeneration was dense and dominated by Picea and Abies. At these sites, regeneration observed from 2003-2005 (hereafter initial regeneration) was also highly predictive of regeneration 5-10 years later. In contrast, at sites that were burned and especially sites that were blown down and burned, regeneration was less dense and dominated by a mix of species.  At these sites, initial regeneration was a poor predictor of longer-term trends as species dominance and overall density fluctuated over the 13 year period.  These findings call into question our ability to confidently make predictions of ecosystem trajectories based upon observations made in the years immediately after large, severe disturbances such as severe wildfires, and especially after compounded disturbances.  As compounded disturbances become more common under climatically-driven changes in disturbance regimes, post-disturbance ecosystem trajectories may become increasingly stochastic and unpredictable.