FORTY YEARS OF CHANGE ALONG THE FRONT RANGE

We plan to resample the plots measured by Bob Peet in 1972-1973. The Peet data consist of tenth hectare quadrats randomly stratified throughout the Colorado Front Range. For each plot, a 50 meter tape was placed along the center line and the edges of the plot were located 10 m to either side. Within the resulting 50 X 20 m rectangle all woody stems greater than 10 cm high were counted and recorded by species. Diameters (dbh; 1.37 m above base) were recorded by 2.5 cm (1 inch) classes, with an additional size-class for individuals less than 1 m high and one for individuals greater than 1 m high but less than 2.5 cm dbh. The herb stratum (leaf area between the ground surface and 1 m) was sampled using a transect of 25contiguous 0.5 X 2 m subplots running the length of the 50 m center line. Within each subplot the percentage cover of each species was visually estimated to the nearest 1%, or above 20% cover to the nearest 5% (maximum of 100% for one species). All additional herbaceous species occurring within the 0.1 ha quadrat, but not encountered within the subplots were recorded as present. Basic site data were recorded for a typical point near the center of each plot. Included were location, elevation, slope, aspect and soil conditions (based on a 10 cm soil pit). The total data set for the vegetation analyses consisted of 305 0.1 ha plots representing 29 community types. Included were 545 species of vascular plants, 7 575 0.5 X 2 m herb plots and approximately 42 000 trees (>2.5 cm dbh). Of these, 96 contained aspen in one of the strata and 89 of these were rellocated and sampled during the summers of 2012 and 2013.

Objectives and Hypotheses:
The objective of the proposed study is to examine the changes in Colorado Front Range forest communities over an approximately forty year period; 1972/3 to 2011/12. Since the 1970s, Colorado forests have been affected by fires (both prescribed and natural), thinning management practices, drought, and a bark beetle epidemic. Because fire, bark beetle outbreaks, and drought are all climate-related phenomena, studying the change in vegetation in response to these drivers will help understand their interactions and impacts (Sibold et al. 2007). We hypothesize that forests have changed drastically since the early 1970s, and that changes will be greatest where multiple disturbances occurred. We further hypothesize that changes will be greatest in the mixed forest zone (includes bark beetle epidemic, sudden aspen decline syndrome, and fires – all potentially climate-driven), as opposed to the Ponderosa Pine communities or the subalpine spruce-fir communities. Chance and species-specific responses will be magnified with higher diversity communities.

 

Front Range forests of Colorado.

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