Abstract
The long-term decline of longleaf pine-dominated forests has received considerable attention among land managers and conservation professionals in the last few decades. The objective of this study was to investigate the change in and the variation of the proportion, density, growth, and dominance of longleaf pine across the longleaf pine ecosystems for the 1997-2018 period. We used two sets of measurements of 1,432 plots from the Forest Inventory and Analysis (FIA) dataset covering the entire current longleaf pine range. The relationship between disturbances and longleaf pine basal area ratio and basal area growth were analyzed using linear mixed modeling. Change detection maps were produced using the Inverse Distance Weighted (IDW) interpolation method. The total basal area and aboveground biomass per hectare increased in 64% and 72%, but decreased in 30% and 28% of the study area, respectively, between the first and last inventory intervals. Species richness and diversity generally decreased across the studied plots. Longleaf pine tree density and importance value percent increased during the period. However, longleaf basal area ratio and aboveground biomass ratio in the stands decreased on average by 5% during the period, although these ratios increased in some locations in southwest Georgia and near the west coast of Florida. The longleaf pine basal area ratio and aboveground biomass ratio decreased equally in 37%, and increased in 19% and 21% of the study area, respectively. There was about 79% variation in the ratio of longleaf pine basal area among plots. When compared to the natural control of no disturbance, fire disturbance was significantly associated with greater longleaf pine basal area ratio and basal area growth. Understanding the change in growth and distribution patterns of longleaf pine across its range over time is vital to restore these critical ecosystems.
Highlights
Longleaf pine (Pinus palustris Mill.) is an ecologically and economically valuable, and a highpriority conservation tree species of the southeastern United States [1]
In addition to the results provided by the model 3, output reveals if there is a relationship between ‘plot condition’ and longleaf pine ‘basal area’ or ‘basal area ratio’
We found a significant change in the stand structure and species composition across the plots between 2004 and 2011(centroid-year of last inventory interval 2003–2018), as described in more detail below
Summary
Longleaf pine (Pinus palustris Mill.) is an ecologically and economically valuable, and a highpriority conservation tree species of the southeastern United States [1]. The longleaf pine ecosystems once occupied around 24–36 million hectares of the South, of which roughly 1.3 million hectares remained by 2006, including about 4,856 hectares of fragmented old-growth forests with a high-diversity understory [1, 3, 4]. Longleaf pine ecosystems consist of widely spaced overstory trees over a predominantly herbaceous ground layer of grasses and forbs. The varied micro-environmental conditions across longleaf pine ecosystems make sites favorable for a great diversity of flora and fauna. Longleaf pine ecosystems provide refuge for at least 122 endangered or threatened plant species, and they give shelter to about 60 percent of the amphibian and reptile species in the southeast, many of them being endemic [4]
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