Life cycle and masting of a recovering keystone indicator species under climate fluctuation

Abstract

Ecosystem health and sustainability, to a large degree, depend on the performance of keystone or dominant species. The role of climate on population dynamics of such species has been extensively examined, especially for health indicator species. Yet the life‐cycle processes and response lags for many species could complicate efforts to detect clear climate signals. Longleaf pine (Pinus palustris Mill.) is such a keystone tree species in the southeastern United States that has declined in both abundance and distribution during the past century. Despite research efforts on multiple fronts, the mechanisms behind the large spatial and temporal fluctuations in cone production that affects its regeneration are largely unknown. On the basis of long‐term (15–56 yr) monitoring data at 10 sites across the species' native range, we examine the spatial and temporal patterns in cone production and possible climatic effects on those patterns using the information‐theoretic approach. Cone production exhibited great variation across sites and years, and long‐term data revealed a weak, ca. 3 yr cycle (4 in one case) across the native range. The effects of climate were rather complex, most likely due to a mismatch between the prolonged cone‐production life‐cycle process and climatic fluctuation. Spatially, sites close to each other generally showed similar physical conditions and temporal trends in cone production. Across sites within longleaf pine's range, moderate climate conditions appear to promote cone production. At most sites, there was an increasing trend in cone production, but how such a trend might be linked to climate change requires further investigation.

Power Laws in Cone Production of Longleaf Pine across Its Native Range in the United States

“…If stewardship programs are to be successful in the future, then, adaptive management needs to understand this source of uncertainty and make suitable accommodation for it. The limitations of short-term and single site studies (e.g., incompleteness and bias) were revealed in a long-term and multi-site study by Guo et al (2016). Results from one site, based on a short period of observation, were not consistent with results from a larger number of sites, observed through a longer time period.…”

“…Although previous studies considered climate factors (e.g., temperature and precipitation) as possible determinants of cone production (Pederson, Kush, & Meldahl, 1998;Pederson, Kush, Meldahl, & Boyer, 2000), later work found that the relationships between climate and cone production were not strong (Guo, Zarnoch, Chen, & Brockway, 2016;Patterson, 2017). Since the quantity of seed produced directly affects longleaf pine forest regeneration, timber supply, wildlife habitat and food chains, it is important to further study the spatial and temporal variance of cone production from different perspectives.…”

“…Scientists and managers still lack a general model for predicting cone production at individual longleaf pine sites across the region or overall cone production relative to the spatial and temporal heterogeneity inherent across its native range. Comparisons of complexity, such as cone production entropy at regional and local levels and through time (Chen, Guo, & Brockway, 2016;Chen, Brockway, & Guo, 2016), may provide new insights about cone production from a perspective not previously explored. Toward the ends of developing useful models and sustainable management strategies for longleaf pine forests at the regional and local scales, new knowledge about the emergent behavior of cone production (e.g., regime shift) needs to be developed.…”

Seed depredation negates the benefits of midstory hardwood removal on longleaf pine seedling establishment

“…Naturally regenerating longleaf pine is a complex process. Seed production requires almost 3 years and varies spatially and temporally in response to temperature and moisture (Guo et al ; Chen et al ). Seed availability often limits regeneration, as good seed years (2,500 cones/ha) occur once every 5–7 years (Wahlenberg ).…”

Simulating groundcover community assembly in a frequently burned ecosystem using a simple neutral model

“…The study sites were within the Southern Pine Hills District of the Coastal Plain Physiographic Province with deep, well-drained sandy soils (Overing et al 1995). The climate of the area is subtropical with mean annual temperatures of 19.7°C and mean annual precipitation of 1580 mm (Guo et al 2016).…”