Correction to: Revealing historical fire regimes of the Cumberland Plateau, USA, through remnant fire-scarred shortleaf pines (Pinus echinata Mill.)

An amendment to this paper has been published and can be accessed via the original article.

Population genomics in two cave-obligate invertebrates confirms extremely limited dispersal between caves

Caves offer selective pressures that are distinct from the surface. Organisms that have evolved to exist under these pressures typically exhibit a suite of convergent characteristics, including a loss or reduction of eyes and pigmentation. As a result, cave-obligate taxa, termed troglobionts, are no longer viable on the surface. This circumstance has led to an understanding of highly constrained dispersal capabilities, and the prediction that, in the absence of subterranean connections, extreme genetic divergence between cave populations. An effective test of this model would involve (1) common troglobionts from (2) nearby caves in a cave-dense region, (3) good sample sizes per cave, (4) multiple taxa, and (5) genome-wide characterization. With these criteria in mind, we used RAD-seq to genotype an average of ten individuals of the troglobiotic spider Nesticus barri and the troglobiotic beetle Ptomaphagus hatchi, each from four closely located caves (ranging from 3 to 13 km apart) in the cave-rich southern Cumberland Plateau of Tennessee, USA. Consistent with the hypothesis of highly restricted dispersal, we find that populations from separate caves are indeed highly genetically isolated. Our results support the idea of caves as natural laboratories for the study of parallel evolutionary processes.

Revealing historical fire regimes of the Cumberland Plateau, USA, through remnant fire-scarred shortleaf pines (Pinus echinata Mill.)

Background Vegetation of the Cumberland Plateau (USA) has undergone dramatic transitions since the last glaciation and particularly since the onset of widespread logging and twentieth century fire exclusion. Shortleaf pine (Pinus echinata Mill.), one of the most fire-dependent conifers in the US, occurs throughout the Cumberland Plateau, but its abundance has declined dramatically since Euro-American settlement and continues to decline. To better understand the historical ecology of fire within the natural range of shortleaf pine, we reconstructed fire regimes at three new sites throughout the central and southern Cumberland Plateau region based on fire scars on shortleaf pine trees. Results Fire event chronologies extended back to the seventeenth century and revealed historical fire regimes that were frequent and dominated by dormant-season and low-severity events. Fires occurred on average every 4.4 to 5.3 years at the study sites before widespread Euro-American settlement, and were more frequent (2.3 to 3.8 years) following settlement. Cumberland Plateau fires may be linked to adjacent ecoregions such as the Eastern Highland Rim to the west. Among all sites, we found that long-term trends in fire activity were similar and fit into a regional waveform pattern of fire activity likely driven by humans (i.e., Native American depopulation, European settlement, and twentieth century fire exclusion). Conclusions The decline in shortleaf pine and other fire-dependent ecosystems across the Cumberland Plateau is due to multiple interacting factors and, based on these data, frequent fire should be considered a historically important ecological driver of these systems.

The effects of oak (Quercus) restoration on forest trajectory and small mammal use in the southern Cumberland Plateau, USA

Background Thinning and prescribed fire are increasingly used to promote oak (Quercus L. spp.) regeneration in forest restoration projects across the eastern United States. In addition to monitoring the response of vegetation to these reductions in basal area, the research and land management community has become focused on the response of wildlife to these treatments. In a landscape in which forest ownership is fragmented and dominated by non-industrial private landowners, predicting the range of wildlife and vegetation response to treatments will be necessary to facilitate adoption of a landscape-scale approach to oak restoration. The goal of this study was to examine the efficacy of restoring privately owned, mixed forest stands that were partially planted in loblolly pine (Pinus taeda L.) and eastern white pine (Pinus strobus L.) to oak-dominated communities through the use of thinning and prescribed fire. Additionally, the study documented implications of these treatments on small mammal activity in the southern Cumberland Plateau. Results Following basal area reductions ranging from 30 to 60% and three prescribed fires across three sites, mean oak seedling densities rose from 10 200 ha−1 to 17 900 ha−1. Post-treatment oak seedling densities were related to pre-treatment densities (R2 = 0.55, P < 0.0001) and the number of oak trees >20 cm diameter within 10 m of plot center (R2 = 0.15, P = 0.01). Three years after the last prescribed fire, bat activity (mean passes per night) was significantly higher in the treated stands compared to adjacent undisturbed forest. We did not detect any significant differences in rodent activity between our treated stands and forest controls for two of the three years studied. Conclusions The results of this study highlighted the within-stand variation that drives post-harvest vegetation trajectories. Three years after the last prescribed fire, bats exhibited higher foraging activity in the treated sites that had lower basal area and very little midstory clutter. Our three-year summer monitoring of rodent activity following the last of the three prescribed fires revealed differences in rodent activity between our treated sites and adjacent forest controls only during 2018 (P = 0.001). These results will assist private landowners in the region as they consider the costs and benefits of oak forest restoration.

Predicting and mapping Plethodontid salamander abundance using LiDAR-derived terrain and vegetation characteristics

Aim of the study: Use LiDAR-derived vegetation and terrain characteristics to develop abundance and occupancy predictions for two terrestrial salamander species, Plethodon glutinosus and P. kentucki, and map abundance to identify vegetation and terrain characteristics affecting their distribution.Area of study: The 1,550-ha Clemons Fork watershed, part of the University of Kentucky’s Robinson Forest in southeastern Kentucky, USA.Materials and methods: We quantified the abundance of salamanders using 45 field transects, which were visited three times, placed across varying soil moisture and canopy cover conditions. We created several LiDAR-derived vegetation and terrain layers and used these layers as covariates in zero-inflated Poisson models to predict salamander abundance. Model output was used to map abundance for each species across the study area.Main results: From the184 salamanders observed, 63 and 99 were identifdied as P. glutinosus and P. kentucki, respectively. LiDAR-derived vegetation height variation and flow accumulation were best predictors of P. glutinosus abundance while canopy cover predicted better the abundance of P. kentucki. Plethodon glutinosus was predicted to be more abundant in sites under dense, closed-canopy cover near streams (2.9 individuals per m2) while P. kentucki was predicted to be found across the study sites except in areas with no vegetation (0.58 individuals per m2).Research highlight: Although models estimates are within the range of values reported by other studies, we envision their application to map abundance across the landscape to help understand vegetation and terrain characteristics influencing salamander distribution and aid future sampling and management efforts.Keywords: Zero-inflated Poisson model; Kentucky; Cumberland plateau; Plethodon glutinosus; Plethodon kentucki.