Intertree competition in uneven-aged ponderosa pine stands

Abstract

Intertree competition indices and effects were examined in 14 uneven-aged ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) stands in eastern Montana. Location, height, diameter at breast height (DBH), basal area increment, crown ratio, and sapwood area were determined for each tree (DBH >3.8 cm) on one stem-mapped plot (0.2-0.4 ha) in each sample stand. Based on tree locations, various competition indices were derived for each sample tree and correlated with its growth efficiency by diameter class. In addition, trends in individual tree attributes by diameter class and level of surrounding competition were determined. For trees with a DBH <10 cm, growth efficiency was most strongly correlated with the sum of surrounding tree heights within 10.6 m. The index most highly correlated for larger trees was the sum of surrounding basal area within 6.1 m. Regardless of tree size, individual tree growth efficiency, basal area increment, and crown ratio all decreased under increasing levels of competition, with the effect more pronounced in smaller trees. These results suggest that individual trees in uneven-aged stands experience competition from differing sources at varying scales based on their size, with response to competition diminishing as tree size increases.

Past, Present, and Future Old Growth in Frequent-fire Conifer Forests of the Western United States

“…Old, large trees have been selectively harvested. The mortality of old trees has probably increased above that of natural attrition in many areas because of high densities of competing young trees, escalating insect or disease outbreaks, or increased stress due to climate change (Woodall et al 2003, Breshears et al 2005.…”

Competitive effect is a linear function of neighbour biomass in experimental populations of Kochia scoparia

“…Foresters and plant ecologists have made numerous attempts to model the performance (e.g. size, growth or reproductive output) of individual 'target' plants as a function of measures of local crowding (Stoll & Weiner 2000) such as the number, distances and sizes of neighbouring trees (Aaltonen 1926;Opie 1968;Bella 1971;Weiner 1984;Woodall et al . 2003;D'Amato & Puettmann 2004).…”

Spatially explicit competition in a mixed planting of Araucaria cunninghamii and Flindersia brayleyana

“…Many variants of forest competition indices have been proposed and tested (e.g., Strub et al 1975;Martin and Ek 1984;Daniels et al 1986;Pukkala and Kolstrom 1987;Tome and Burkhart 1989;Biging and Dobbertin 1995;Soares and Tome 1999;Ledermann and Stage 2001;Miina and Pukkala 2002;Radtke et al 2003;Woodall et al 2003;Stadt et al 2007;Oheimb et al 2011). A recent classification and review offered by Weiskittel et al (2011) illustrates the utility of Hegyi-type indices (Hegyi 1974;Holmes and Reed 1991;Mailly et al 2003;Vanhellemont et al 2010) that rely on the relative size of potential competitors and the distance between them.…”