Understory response to restoration treatments in pine/fir forests of the Intermountain West varies with temporal and spatial scale.
Metlen, Kerry*,1, Fiedler, Carl1, 1 University of Montana, Missoula, MT, USA
ABSTRACT- Forest restoration/fuel reduction projects underway or proposed for millions of hectares of pine/fir forests in the Intermountain West will impact the composition and abundance of understory plant communities. Treatment impacts vary depending on site history, environmental conditions, treatment intensity, and propagule pressure. Detection of response is influenced by time since treatment, sampling scale, and the use of pretreatment measurements and controls. Our objective in this study was to evaluate understory community response to treatment at multiple temporal and spatial scales. We implemented a study of operational restoration treatments in a Montana ponderosa pine (Pinus ponderosa)/Douglas-fir (Pseudotsuga menziesii) forest typical of the intermountain west. Treatments included thinning-from-below combined with improvement/selection cutting (thin), the thin treatment followed by spring burning (thin/burn), spring burning only (burn), and a no-treatment control. All treatments were replicated three times in a randomized block design. Pretreatment measurements were taken in the summers of 2000 and 2001. Thinning was completed in the winter of 2001 and burning was conducted in the spring of 2002. Here, we present data from pretreatment, 2002, 2003, and 2004. Nonmetric multidimensional scaling was used to visualize the response of the understory vascular plant community for each treatment over time at two spatial scales: 1-m2 and 1000-m2. In an attempt to isolate community shifts associated with species groups of interest, additional ordinations were run with only native species and only exotic species. The native community response mirrored the overall community response at 1-m2. The influence of the exotic community on the overall species ordination was more noticeable at 1000-m2. Exotic response was more dependent on treatment than either the native or overall community response. Community trajectories suggest a future understory in the thin/burn treatment different from pretreatment and from future communities in the control and burn-only treatments.
Key words: restoration, fuel reduction, exotic species, ponderosa pine
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