PARENT SESSION
Oral Session #62: Vegetation change: Succession, recovery, facilitation. Presiding: S. Franklin.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.
Spatial heterogeneity and long-term forest stand development: Do fire-created landscape legacies persist?
Kashian, Daniel1, Turner, Monica1, 1
ABSTRACT- Understanding the factors controlling landscape pattern is crucial for predicting ecosystem dynamics and vegetation development in disturbance-prone landscapes. Although landscape pattern has strong implications for ecological processes, the spatio-temporal dynamics of post-disturbance landscape pattern are poorly understood. We examined the development of stands within a forested landscape to understand the degree to which a post-disturbance landscape pattern changes over time. Synthesizing empirical measurements of tree density and age structure for a chronosequence of lodgepole pine (Pinus contorta var. latifolia) stands, simulation modeling, and landscape pattern analyses, we examined the legacies of large, infrequent fires in Yellowstone National Park. Variation in stand density significantly decreased with stand age (p=0.03) and was highest in the youngest age class (p=0.02), likely due to self-thinning in initially dense stands and continuous seedling establishment in initially sparse stands. Using the post-1988 Yellowstone landscape to initiate our simulation model, we noted the coalescence of dissimilar patches with age as evidenced by a decrease in the number of patches and an increase in dominance, connectivity, and mean patch size for a given density class. Dynamics of post-fire landscape pattern thus depend on magnitudes and rates of change in stand structure, the initial relative proportions of stand density across the landscape, and the initial spatial arrangement of patches produced by the disturbance. In general, landscape heterogeneity decreases with time since disturbance, and post-disturbance landscape legacies become less apparent.
KEY WORDS: landscape legacies, lodgepole pine, forest stand dynamics, landscape heterogeneity