Category: Ecological Research
Title: Reference conditions and historical changes in an unharvested ponderosa pine stand on sedimentary soil
Author: Schneider, E.E., * Sanchez-Meador, A.J. , * Covington, W.W.
Subject: Natural Range of Variability, Ponderosa pine (Pinus ponderosa)
Abstract: Much of the previous research on spatial reference conditions in dry frequent fire pine forests have come from stand-level patterns under regionally average ecosystem conditions (e.g. soil type and precipitation). We evaluated the 1883 reference conditions of an uncut ponderosa pine stand representing a far end of the range of variability in terms of regionally unusual environmental conditions. Using a forest reconstruction model, univariate and bivariate Ripley’s K functions, and regression analysis, we determined 1883 structural and spatial reference conditions, and compared those to the contemporary (2010) stand. Historical stand density was 77 trees/ha with a basal area of 8.0m2/ha. Reference spatial patterns were significantly aggregated from 1 to 2m and randomly distributed at distances greater than 2 m. Nearly 40% of the reconstructed trees were individuals, the average patch size was 2.9 trees, and the largest patch had 7 members. The contemporary stand had considerably greater densities and basal area than historical conditions and showed aggregation at all distances. Bivariate spatial analysis indicated attraction of post-settlement recruitment to live pre-settlement trees from 1 to 6mand no association at distances greater than 6 m. We speculate that the historically random tree pattern is the product of a variety of factors including soil parent material, climate, and more homogeneous resource partitioning.
Source: Restoration Ecology
Identifier: doi: 10.1111/rec.12296
Publisher: Restoration Ecology