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Full-Text Articles in Physical Sciences and Mathematics

Species Richness And Soil Properties In Pinus Ponderosa Forests: A Structural Equation Modeling Analysis, Daniel C. Laughlin, Scott R. Abella, W. Wallace Covington, James B. Grace Jan 2007

Species Richness And Soil Properties In Pinus Ponderosa Forests: A Structural Equation Modeling Analysis, Daniel C. Laughlin, Scott R. Abella, W. Wallace Covington, James B. Grace

Public Policy and Leadership Faculty Publications

Question: How are the effects of mineral soil properties on understory plant species richness propagated through a network of processes involving the forest overstory, soil organic matter, soil nitrogen, and understory plant abundance? Location: North-central Arizona, USA. Methods: We sampled 75 0.05-ha plots across a broad soil gradient in a Pinus ponderosa (ponderosa pine) forest ecosystem. We evaluated multivariate models of plant species richness using structural equation modeling. Results: Richness was highest at intermediate levels of understory plant cover, suggesting that both colonization success and competitive exclusion can limit richness in this system. We did not detect a reciprocal positive …


Forest-Floor Treatments In Arizona Ponderosa Pine Restoration Ecosystems: No Short-Term Effects On Plant Communities, Scott R. Abella, W. Wallace Covington Jan 2007

Forest-Floor Treatments In Arizona Ponderosa Pine Restoration Ecosystems: No Short-Term Effects On Plant Communities, Scott R. Abella, W. Wallace Covington

Public Policy and Leadership Faculty Publications

Leaf litter accumulation during fire exclusion and increases in tree density in postsettlement southwestern Pinus ponderosa forests may limit the establishment of understory vegetation. We performed an experiment in P. ponderosa forests of northern Arizona to ascertain plant community responses to forest-floor scarification and Oi removal on thirty-six 100-m2 plots overlaid on an existing ecological restoration experiment that involved tree thinning and prescribed burning. Constrasting with findings from many other forest types, forest-floor treatments had no effect on community diversity or composition during the 2-year experiment. Sørensen similarities were as high as 97% between posttreatment years within treatments; and successional …


Past, Present, And Future Old Growth In Frequent-Fire Conifer Forests Of The Western United States, Scott R. Abella, W. Wallace Covington, Peter Z. Fule, Leigh B. Lentile, Andrew J. Sanchez Meador, Penelope Morgan Jan 2007

Past, Present, And Future Old Growth In Frequent-Fire Conifer Forests Of The Western United States, Scott R. Abella, W. Wallace Covington, Peter Z. Fule, Leigh B. Lentile, Andrew J. Sanchez Meador, Penelope Morgan

Public Policy and Leadership Faculty Publications

Old growth in the frequent-fire conifer forests of the western United States, such as those containing ponderosa pine (Pinus ponderosa), Jeffrey pine (P. jeffreyi), giant sequoia (Sequioa giganteum) and other species, has undergone major changes since Euro-American settlement. Understanding past changes and anticipating future changes under different potential management scenarios are fundamental to developing ecologically based fuel reduction or ecological restoration treatments. Some of the many changes that have occurred in these forests include shifts from historically frequent surface fire to no fire or to stand-replacing fire regimes, increases in tree density, increased abundance of fire-intolerant trees, decreases in understory …