Pinus Palustris Mill Research Articles

Tradeoffs in longleaf pine conservation: Prescribed fire management increases exotic ambrosia beetle abundance in pine-hardwood forests

Exotic woodboring insects, including some ambrosia beetles (Coleoptera: Curculionidae, Scolytinae, and Platypodidae), are threatening native forests worldwide. Longleaf pine (Pinus palustris Mill.) forest is an endangered habitat in the southeastern United States. One of the most important actions necessary for its conservation is prescribed fire, which maintains its savanna structure. However, prescribed fire is a forest disturbance, possibly creating new niches for colonization by exotic insects. The interaction between prescribed fire and exotic ambrosia species is understudied, especially in highly fire-dependent ecosystems. We carried out a two-year experiment in mixed longleaf pine forests in Alabama, USA. We compared ambrosia beetle communities in recently burned and unburned sites. We found that more than 66 % of total individuals in longleaf pine forests, regardless of fire management, were exotic species. Moreover, exotic ambrosia beetles were more abundant in burned stands, whereas native species showed no difference between burned or unburned stands. Fire management influenced stand species composition for native but not exotic ambrosia beetles. These results indicate that trade-offs exist in managing fire-dependent ecosystems, especially in the Anthropocene era, which is associated with rampant biological invasions. Fire is important to preserve the longleaf pine habitat, but it simultaneously acts as a disturbance, increasing the population density of those exotic species taking advantage of the presence of stressed or dying trees.

Fire exclusion alters forest evapotranspiration: A comprehensive water budget analysis in longleaf pine woodlands

AbstractForests are critical to water resources, but high evapotranspiration (ET) can reduce water yield. Thinning and prescribed fire reduce forest density and often reduce ET, promoting higher water yield. However, results from such treatments have been inconsistent, possibly because of unknown interactions among individual ET components. We compare water budget components of longleaf pine (Pinus palustris Mill.) woodlands with frequent prescribed fire to the water budget components of fire‐excluded stands. We hypothesized that fire exclusion would result in higher ET due to increased midstory transpiration (Et) and interception (Ei), and higher evaporation from litter (Ilitter). Reference plots were burned every two years while treatment plots had fire excluded for 15–20 years. Fire treatments were repeated in two sites representing a soil moisture gradient, noted as mesic and xeric. We measured woody Et using sap flux, and we modeled groundcover Et using physiological models. We measured Ei of canopy and groundcover layers, modeled Es litter biomass, and constructed a total component‐based water budget for each site and treatment. Compared with reference plots, midstory Et was 300%–800% higher in fire exclusion plots. Groundcover Et was ~80% less than reference treatments, countering the effects of midstory growth on total ET. Stand Ei followed similar trends, with groundcover Ei in reference plots countering the effects of midstory and litter Ei in fire exclusion plots. As expected, total ET in the xeric site was 18% higher in fire exclusion plots. However, ET in the mesic site was 16% lower in the fire exclusion plots due to high groundcover Et and Ei in reference plots. Thus, our results show that fire exclusion changes total forest ET, but the size and direction of the effect vary depending on the balance between midstory and groundcover transpiration and interception. These results highlight the importance of groundcover in ecosystem function in low‐density forests and may help explain inconsistent results from studies of water yields following thinning and fire. While prescribed fire is a valuable tool in forest management, we suggest that the effects of fire on ET are complex and require careful accounting of all water fluxes within a forest ecosystem.

Range-Wide Assessment of Recent Longleaf Pine (Pinus palustris Mill.) Area and Regeneration Trends

Longleaf pine (Pinus palustris Mill.) is a conifer historically associated with an open forest ecosystem that extended across much of the coastal plain of the Southeastern United States. It now exists mainly in isolated fragments following the conversion of forests and the long-term disruption of the low-intensity fire regime upon which the species depends. Recent decades have seen efforts to restore longleaf pine forests by government and private landowners. This was reflected in analyses of national forest inventory data during two time periods, ca. 2009–2015 and 2016–2021, that showed increases in the estimated number of longleaf pine trees, the area of the longleaf pine forest type, and the number and area of planted longleaf pine, along with growth in mean plot-level longleaf pine carbon and importance value. At the same time, we found a decrease in the overall forest area containing longleaf pine, manifested across a variety of other forest types. These results point to a dynamic through which forests dominated by longleaf pine are becoming more widespread via restoration, while forests in which the species is a less important component are transitioning to other forest types or land uses. We also detected a decrease over time in the estimated number of longleaf seedlings across most states and forest types and a decline in naturally regenerated longleaf pine. To further assess regeneration trends in longleaf pine, we calculated the estimated proportion of small trees (seedlings and saplings) for the entire species and for seed zone sub-populations. We found a species-wide decrease in the proportion of small trees, from 82.1 percent to 75.1 percent. This reduction was most pronounced along the edges of the species distribution and could indicate less sustainable levels of regeneration in some areas. These results underscore the challenges of facilitating natural regeneration in this important species.

Damage prediction for planted longleaf pine in extreme winds

Severe wind disturbances are forecast to increase in frequency and intensity with climate change putting forest trees at greater risk of wind damage. Of particular concern are mature and old-growth forests of wind-prone regions which host considerable biodiversity. Landscape configuration, stand structure, and tree characteristics affect susceptibility to wind damage. In managed forests and restoration contexts, these factors could be manipulated to enhance resistance to severe wind events. We measured landscape, stand, and tree characteristics, and damage in longleaf pine (Pinus palustris Mill.) forests in southwest Georgia and Northwest Florida affected by Hurricane Michael (2018) and used these data to model wind damage. We hypothesized that wind damage would increase with wind exposure and decrease with diameter-to-height ratio (taper). We found that lower wind exposure and higher taper resulted in substantially lower wind damage. We conclude that maintaining lower stand density during stand development could reduce wind damage by increasing individual tree resistance to wind. Management and restoration activities that increase resilience to threats from extreme weather can help maintain persistence and landscape restoration of global biodiversity hotspots in wind-prone regions.

The effects of a moderate severity hurricane on gap characteristics in a longleaf pine (Pinus palustris Mill.) woodland

Modern forestry research emphasizes infusing management practices with an understanding of natural disturbance regimes—often called ecological forestry. Forestry practices that emulate aspects of natural disturbance regimes are considered an effective approach to balance silvicultural and ecological objectives. Silvicultural research is often available to guide successful regeneration in many forest types, but little information is available about gap patterns from common disturbances in the eastern U.S. like hurricanes. We examined the size, shape, and spatial distribution of canopy gaps formed in a longleaf pine woodland by Hurricane Michael across multiple landscape factors including stand size, composition, and soil types. We found high variation in many gap characteristics but no significant differences in gap size or shape among landscape factors. However, spatial distribution of gaps differed among landscape types in nuanced ways. We also found that stand size complexity may prevent the formation of very large gaps that can disrupt fire continuity in systems managed with frequent fire. The results highlight the ecological importance of hurricane events and provide insight into hurricane gap formation at the landscape scale. The implementation of silviculture practices that emulate a large, rapid, single disturbance event may be more practically applied than management based on disturbances such as lightning or insects which occur over longer timeframes.

Differential effects of fire regime and site conditions on bark beetles (Coleoptera: Curculionidae) in a longleaf pine (Pinus palustris Mill.) ecosystem

Longleaf pine (Pinus palustris Mill.) ecosystems in the southeastern U.S. are fire-driven. Frequent prescribed fire or lack thereof through shifts in fire regimes may have consequences for tree health and associated herbivorous subcortical beetles (Coleoptera: Curculionidae). Yet, interactions between these ecologically and economically important beetles and prescribed fire in the southeastern U.S. are not well documented. We assessed the effects of various fire regimes, specifically of frequent fire, fire exclusion, and fire reintroduction, on bark and root-feeding beetles in mature longleaf pine stands in two edaphic types (mesic and xeric) in southwestern Georgia. We employed an information theoretic statistical approach to determine the effects of site conditions, as defined by both soil properties and stand structure, and prescribed burning on trap catches of subcortical beetles by species. We trapped a total of 141,611 beetles, indicating that subcortical beetles are abundant in this ecosystem. While the highest trap catches for three Ips beetle species were in the xeric fire-exclusion treatment, catches of I. grandicollis (Eichhoff) were similar at both sites for the fire-exclusion treatment. For the fire-exclusion treatment, I. avulsus (Eichhoff) and I. calligraphus (Germar) catches were 2–10 times higher at the xeric than mesic sites. Orthotomicus caelatus (Eichhoff) and Dendroctonus terebrans (Olivier) catches were 1.1–2.4 times higher in frequent-fire than fire-exclusion treatments. Root-feeding weevils, Pachylobius picivorus (Germar) and Hylobius pales (Herbst), exhibited opposite trends with catches higher and lower in burned treatments, respectively. Ips calligraphus were positively associated with percent basal area of understory trees, indicating this species may benefit from fire exclusion. Ips avulsus catches were negatively correlated with total basal area, suggesting this species may benefit from more open habitats like those facilitated by frequent fire. We conclude that both soil properties and stand conditions interact with the fire regime to differentially affect the catches of southeastern bark and root-feeding beetle species in a longleaf pine ecosystem.

Modeling spatial patterns of longleaf pine needle dispersal using long-term data

BackgroundPredicting patterns of fire behavior and effects in frequent fire forests relies on an understanding of fine-scale spatial patterns of available fuels. Leaf litter is a significant canopy-derived fine fuel in fire-maintained forests. Litter dispersal is dependent on foliage production, stand structure, and wind direction, but the relative importance of these factors is unknown.ResultsUsing a 10-year litterfall dataset collected within eighteen 4-ha longleaf pine (Pinus palustris Mill.) plots varying in canopy spatial pattern, we compared four spatially explicit models of annual needle litter dispersal: a model based only on basal area, an overstory abundance index (OAI) model, both isotropic and anisotropic litter kernel models, and a null model that assumed no spatial relationship. The best model was the anisotropic model (R2 = 0.656) that incorporated tree size, location, and prevailing wind direction, followed by the isotropic model (R2 = 0.612), basal area model (R2 = 0.488), OAI model (R2 = 0.416), and the null model (R2 = 0.08).ConclusionsAs with previous studies, the predictive capability of the litter models was robust when internally validated with a subset of the original dataset (R2 = 0.196–0.549); however, the models were less robust when challenged with an independent dataset (R2 = 0.122–0.319) from novel forest stands. Our model validation underscores the need for rigorous tests with independent, external datasets to confirm the validity of litter dispersal models. These models can be used in the application of prescribed fire to estimate fuel distribution and loading, as well as aid in the fine tuning of fire behavior models to better understand fire outcomes across a range of forest canopy structures.

Spatial Multi-Criteria Decision Modeling for Pinus palustris Mill. (Longleaf Pine) Restoration in the South Carolina Sandhills Wiregrass Gap

Spatial Multi-Criteria Decision Modeling for Pinus palustris Mill. (Longleaf Pine) Restoration in the South Carolina Sandhills Wiregrass Gap

Impacts of longleaf pine (Pinus palustris Mill.) on long-term hydrology at the watershed scale

Threats from climate change and growing populations require innovative solutions for restoring streamflow in many regions. In the arid western U.S., attempts to increase streamflow (Q) through forest management have had mixed results, but these approaches may be more successful in the eastern U.S. where greater precipitation (P) and lower evapotranspiration (ET) offer greater potential to increase Q by reducing ET. Longleaf pine (Pinus palustris Mill.) (LLP) woodlands, once the dominant land cover in the southeastern United States, often have lower ET than other forest types but it is unclear how longleaf pine cover impacts watershed-scale hydrology. To address this question, we analyzed 21 gaged rural watersheds. We estimated annual water balance ET (ETwb) as the difference between precipitation (P) and streamflow (Q) between 1989 and 2021 and quantified low flow rates (7Q10) among watersheds with high and low LLP cover. To control for climate variability among watersheds, we compared variation in hydrology metrics with biotic and abiotic variables using the Budyko equation (ETBudyko) to understand the differences between the two ET estimates (∆ET). Watersheds with 15–72 % LLP cover had 17 % greater mean annual Q, 7 % lower annual ETwb, and 92 % greater 7Q10 low flow rates than watersheds with <3 % LLP. LLP cover decreased ET and increased Q by 2.4 mm or 0.15 % Q/P per 1 % of watershed area, but only when LLP was managed as open woodlands. Our results demonstrate that ecological forest restoration in these systems, which entails mechanical thinning and re-introduction of low-intensity prescribed fire to maintain open woodlands, and enhance understory diversity, can contribute to decreases in ET and increases in Q in eastern forests.

Upland forest community composition and structure by ecoregion in 73 Florida state parks – Insights for ongoing management

Plot based forest/vegetation data is used to establish current conditions and inform natural resources management decisions. The Florida Department of Environmental Protection – Division of Recreation and Parks (DRP) manages 175 state parks. As part of its mission, DRP strives to restore landscapes and natural communities by reintroducing dynamic natural processes such as fire. DRP also uses other methods of active management to achieve desired future conditions (DFCs) in multiple communities including those characterized by longleaf pine (Pinus palustris Mill.) and native groundcover (GC) species. To meet the challenge of managing natural resources across the State, DRP initiated an objective and repeatable forest/vegetation inventory system. The primary objective of this paper was to analyze and summarize the resultant data and compare current community type (ComType) vegetation conditions. Current conditions were quantified using nested plots distributed within sample areas across 73 state parks and 15 ecoregions via the line-plot method. Over 37,000 plots were inventoried; 36% were in pine flatwoods. Ten actively managed and dominant ComTypes were central to this paper and when aggregated by ecoregion, 76 ComType by ecoregion (CTER) groups were examined. Descriptive statistics for various measurements, e.g., diameter at breast height, height, and density, were calculated for overstory, midstory and understory (vegetation layer) separately per CTER. Mean importance value index (IVI) was calculated by species or species-group per vegetation layer and CTER. Community classification was conducted via hierarchical clustering of CTERs per vegetation layer using mean IVI scores. Across CTERs, pine overstory and midstory abundance/stocking levels were generally low, non-pine overstory and midstory stocking levels were high, pine regeneration was sparse, and GC was dominated by leaf litter, pine straw, and non-pine woody seedlings. Results strongly suggest that some ComTypes were similar within certain ecoregions. Various pine species are considered dominant or one of the prominent overstory species for eight of the ten ComTypes. The ability to manage upland pine ComTypes using natural regeneration systems will become increasingly challenging in the near- to medium-term given relatively low overstory pine stocking for most CTERs, and the virtual lack of young pines within midstory and understory layers. Further investigations could help identify potential causal agents concerning low young pine stocking levels, e.g., timing and frequency of prescribed fires, frequency of logging, and/or increased competition from high densities of midstory non-pines and appropriate natural regeneration systems, e.g., seed tree, shelterwood, or group selection, or underplanting longleaf pine, that would accelerate understory pine recruitment.

The Relationships between Climate, Tree-Ring Growth, and Cone Production in Longleaf Pine

Historically abundant longleaf pine (Pinus palustris Mill.) trees were once a leading source of profit and ecosystem services across the southeastern United States. The widespread decline in longleaf numbers following European colonization has prompted substantial restoration efforts, though much is still not understood about longleaf growth and reproductive processes. In this study, we used Pearson and regression correlation analysis to quantify the relationship between cone production, radial growth, and climate signals in longleaf pine trees at three sites across their range. We documented a high amount of intersite variability; trees at all three sites experienced significant relationships between reproduction, radial growth, and climate, though in different and sometimes contrasting ways. We found a roughly equivalent number of significant cone growth and climate correlations with extreme climate events (e.g., heat stress, hurricane frequency) as with average climate conditions, and highlight the need to consider both over multiple spans of time. This study provides a new understanding of how climate variables relate to the relationship between growth and reproduction in longleaf pine trees.

Opportunities for Research on Carbon Management in Longleaf Pine Ecosystems

Longleaf pine (Pinus palustris Mill.) savannas and woodlands are known for providing numerous ecosystem services such as promoting biodiversity, reducing risk of wildfire and insect outbreaks, and increasing water yields. In these open pine systems, there is also interest in managing carbon (C) in ways that do not diminish other ecosystem services. Additionally, there may be management strategies for accomplishing these same objectives in plantations and degraded stands that developed from natural regeneration. For example, C accumulation in live trees and C storage in harvested wood products could be increased by extending rotations and converting plantations to multi-aged stands. Belowground C storage could be enhanced by incorporating pyrogenic C into the mineral soil before planting longleaf pines in clearcut areas, but this may be contrary to findings that indicate that minimizing soil disturbance is important for long-term soil C storage. We suggest examining approaches to reduce total ecosystem C emissions that include using targeted browsing or grazing with domesticated livestock to supplement prescribed burning, thereby reducing C emissions from burning. The mastication of woody vegetation followed by a program of frequent prescribed burning could be used to reduce the risk of substantial C emissions from wildfires and to restore function to savannas and woodlands with hardwood encroachment and altered fire regimes. Many of these approaches need to be validated with field studies or model simulations. There is also a need to improve the estimates of dead wood C stocks and C storage in harvested wood products. Finally, eddy covariance techniques have improved our understanding of how disturbances influence longleaf pine C dynamics over multiple time scales. However, there is a need to determine the degree to which different silvicultural approaches, especially those for adapting ecosystems to climate change, influence C accumulation. Overall, our review suggests that there are numerous opportunities for research on C dynamics in longleaf pine ecosystems, and these systems are likely well-positioned to accomplish C objectives while offering other ecosystem services.

Experimental translocation for restoration of an ecosystem engineer

The longleaf pine (Pinus palustris Mill.) savanna ecosystem in North America has declined by 97% from its historic range and its restoration is a conservation priority. The southeastern pocket gopher (Geomys pinetis), an ecosystem engineer in longleaf pine savannas, is absent from most of its historic range. Translocation of pocket gophers may be needed to reestablish ecosystem services of restored longleaf savannas. To determine translocation feasibility, we quantified survival, site fidelity, and homing of pocket gophers translocated using soft releases (with a starter burrow system; n = 13), hard releases (without a starter burrow system; n = 17), or released into their own burrows (control; n = 10). Naïve survival was 46 and 35% for soft‐ and hard‐released individuals, respectively, and 80% for controls. Most mortalities of translocated individuals (75.0%) occurred within 12 days. Including all radiotagged pocket gophers, daily survival of soft‐released animals ( = 0.990) was intermediate between hard‐released ( = 0.986) and controls ( = 0.993), and only hard‐released was lower than controls. Using only individuals that survived greater than 14 days, we found no difference in daily survival. Site fidelity was low, with 70% of translocated pocket gophers making aboveground movements away from release point. However, soft‐released individuals stayed at the release point three times longer than hard‐released animals. No pocket gopher exhibited homing. Our results suggest translocation has potential for establishing pocket gopher populations into restored longleaf pine savannas and that mitigating mortality during establishment will increase the likelihood of success.

Individuals’ Behaviors of Cone Production in Longleaf Pine Trees

The sporadic cone production of longleaf pine (Pinus palustris Mill.) challenges the restoration of the longleaf pine ecosystem. While much has been learned about longleaf pine cone production at the stand level, little information exists at the tree level regarding cone production and energy allocational strategy. This study aims to analyze cone production and diameter growth of approximately ten sampled longleaf pine trees at seven sites across the southeastern USA over the past twenty years. The results indicate that three-year cycles dominated the cone production dynamics, but longer cycles (four years and more) also occurred. The dynamics of entropy in cone production varied among trees. Taylor’s law, which describes the correlation between average and variance, existed in cone production for the majority of trees. Lagged cone production at one and two years was not autocorrelated among trees across sites. No significant relationships existed between tree diameter (or basal area) growth and cone production among trees across sites. This study provides new information on cone production at the individual tree level and narrows down the possible mechanisms. The results will be helpful in developing strategies for the management and modeling of longleaf pine cone production.

Crown-Level Structure and Fuel Load Characterization from Airborne and Terrestrial Laser Scanning in a Longleaf Pine (Pinus palustris Mill.) Forest Ecosystem

Airborne Laser Scanners (ALS) and Terrestrial Laser Scanners (TLS) are two lidar systems frequently used for remote sensing forested ecosystems. The aim of this study was to compare crown metrics derived from TLS, ALS, and a combination of both for describing the crown structure and fuel attributes of longleaf pine (Pinus palustris Mill.) dominated forest located at Eglin Air Force Base (AFB), Florida, USA. The study landscape was characterized by an ALS and TLS data collection along with field measurements within three large (1963 m2 each) plots in total, each one representing a distinct stand condition at Eglin AFB. Tree-level measurements included bole diameter at breast height (DBH), total height (HT), crown base height (CBH), and crown width (CW). In addition, the crown structure and fuel metrics foliage biomass (FB), stem branches biomass (SB), crown biomass (CB), and crown bulk density (CBD) were calculated using allometric equations. Canopy Height Models (CHM) were created from ALS and TLS point clouds separately and by combining them (ALS + TLS). Individual trees were extracted, and crown-level metrics were computed from the three lidar-derived datasets and used to train random forest (RF) models. The results of the individual tree detection showed successful estimation of tree count from all lidar-derived datasets, with marginal errors ranging from −4 to 3%. For all three lidar-derived datasets, the RF models accurately predicted all tree-level attributes. Overall, we found strong positive correlations between model predictions and observed values (R2 between 0.80 and 0.98), low to moderate errors (RMSE% between 4.56 and 50.99%), and low biases (between 0.03% and −2.86%). The highest R2 using ALS data was achieved predicting CBH (R2 = 0.98), while for TLS and ALS + TLS, the highest R2 was observed predicting HT, CW, and CBD (R2 = 0.94) and HT (R2 = 0.98), respectively. Relative RMSE was lowest for HT using three lidar datasets (ALS = 4.83%, TLS = 7.22%, and ALS + TLS = 4.56%). All models and datasets had similar accuracies in terms of bias (&lt;2.0%), except for CB in ALS (−2.53%) and ALS + TLS (−2.86%), and SB in ALS + TLS data (−2.22%). These results demonstrate the usefulness of all three lidar-related methodologies and lidar modeling overall, along with lidar applicability in the estimation of crown structure and fuel attributes of longleaf pine forest ecosystems. Given that TLS measurements are less practical and more expensive, our comparison suggests that ALS measurements are still reasonable for many applications, and its usefulness is justified. This novel tree-level analysis and its respective results contribute to lidar-based planning of forest structure and fuel management.

Optimal Forest Management of Even-Aged Longleaf Pine Stands with Nontimber Benefits

AbstractWe present an optimal control model to simultaneously determine the optimal planting density, thinning schedules, harvest age, and revenues of an even-aged longleaf pine (Pinus palustris Mill) stand, an iconic species in the Southeastern United States. We assume that the forest stand is managed for timber production and carbon sequestration under different site indexes—a measurement of potential forest productivity. Our simulation results show that the optimal planting density tends to increase when longleaf pine is managed in medium and high site indexes. Furthermore, the optimal harvest age tends to be extended with payments for carbon sequestration.

Xerophytic hardwood retention promotes competition over facilitation in longleaf pine woodlands in the absence of fire

Recent reports of xerophytic hardwood facilitation of longleaf pine seedlings challenge the traditional paradigm that co-occurring hardwood tree species constrain longleaf pine (Pinus palustris Mill.) regeneration. To better understand this dynamic, we established an experiment examining the effects of hardwood retention duration (no retention, one-year retention, four-year retention), overstory basal area (2-to-41 m2 ha−1), and understory vegetation cover on microclimatic conditions and longleaf pine seedling survival, development, physiological performance, and brownspot needle blight (Mycosphaerella dearnessii) infection in the Sandhills Ecoregion of North Carolina, USA. Light availability (μmol m−2 s−1) at the forest floor (∼20 cm) was reduced by 27% in the four-year retention treatment which significantly exceeded reductions found in the one-year (<1%) and no retention (<1%) treatments, respectively, post midstory removal. However, midstory treatment had little effect on soil moisture and temperature at 15 and 30 cm depth. Longleaf pine seedling survival (85%), aboveground biomass (7.51 g dry weight), and root collar size (1.53 cm) were significantly highest in the no retention treatment compared to the four-year retention treatment. Between treatments with midstory retention (one-year vs. four-year retention), longleaf pine seedlings were statistically larger in the one-year retention treatment (5.37 g dry weight) compared to the four-year retention treatment (4.84 g dry weight). Seedling brownspot infection did not statistically vary among midstory retention treatments. Across all midstory treatments, overstory basal area had a stronger negative effect on longleaf pine seedling aboveground biomass development, root collar development and brownspot infection compared to midstory hardwood stem density or understory vegetation cover. Moreover, for most measured metrics, overstory basal area had a stronger negative effect on longleaf pine physiological performance compared to midstory hardwood stem density. Collectively, these results indicate that hardwood retention did not facilitate longleaf pine survival and development in the grass stage and that asymmetric competition from the overstory represents a stronger impediment to longleaf pine sapling recruitment than midstory hardwoods.

The Longleaf Tree-Ring Network: Reviewing and expanding the utility of Pinus palustris Mill. Dendrochronological data

The longleaf pine ( Pinus palustris Mill.) and related ecosystem is an icon of the southeastern United States (US). Once covering an estimated 37 million ha from Texas to Florida to Virginia, the near-extirpation of, and subsequent restoration efforts for, the species has been well-documented over the past ca. 100 years. Although longleaf pine is one of the longest-lived tree species in the southeastern US—with documented ages of over 400 years—its use has not been reviewed in the field of dendrochronology. In this paper, we review the utility of longleaf pine tree-ring data within the applications of four primary, topical research areas: climatology and paleoclimate reconstruction, fire history, ecology, and archeology/cultural studies. Further, we highlight knowledge gaps in these topical areas, for which we introduce the Longleaf Tree-Ring Network (LTRN). The overarching purpose of the LTRN is to coalesce partners and data to expand the scientific use of longleaf pine tree-ring data across the southeastern US. As a first example of LTRN analytics, we show that the development of seasonwood chronologies (earlywood width, latewood width, and total width) enhances the utility of longleaf pine tree-ring data, indicating the value of these seasonwood metrics for future studies. We find that at 21 sites distributed across the species’ range, latewood width chronologies outperform both their earlywood and total width counterparts in mean correlation coefficient (RBAR = 0.55, 0.46, 0.52, respectively). Strategic plans for increasing the utility of longleaf pine dendrochronology in the southeastern US include [1] saving remnant material ( e.g., stumps, logs, and building construction timbers) from decay, extraction, and fire consumption to help extend tree-ring records, and [2] developing new chronologies in LTRN spatial gaps to facilitate broad-scale analyses of longleaf pine ecosystems within the context of the topical groups presented.

Influence of climate fluctuations on Pinus palustris growth and drought resilience

The longleaf pine (Pinus palustris Mill.) ecosystem is an endangered ecosystem in the southeastern USA, and efforts to restore the species are ongoing. However, in recent decades, the region has experienced drastic fluctuations between wet and dry growing season conditions from year to year, and it is not fully understood how these fluctuations have influenced the growth of P. palustris. To address this topic, we cored P. palustris trees in woodlands of southwest Georgia and used dendrochronology techniques to determine how climate fluctuations have influenced the growth and drought resilience of P. palustris. We also cored slash pine (Pinus elliottii Engelm.) trees in the same woodlands to compare growth between species. While P. palustris growth was less impacted by adverse climate conditions compared to P. elliottii, the strength of correlations between P. palustris growth and temperature, precipitation, and Palmer Drought Severity Index (PDSI) changed over time. In recent decades, climate conditions during the growing season became more influential on P. palustris growth than the previous year's conditions. This is concerning given that drought severity during the growing season has been increasing. Our results also indicate that P. palustris was less resilient to droughts during the 2000s and 2010s than to those of the 1950s. Under this new climate paradigm, our results suggest that P. palustris might be more susceptible to growth reductions and less resistant to droughts than once expected. This work highlights the importance of understanding the impact of novel climate conditions on P. palustris and has implications for restoration efforts, such as using silvicultural treatments that reduce tree vulnerability to drought (e.g., thinning) and promote other climate-adapted species in mixture with P. palustris.

Assessing productivity and cost of timber harvesting during longleaf pine ecosystem restoration

ABSTRACT Timber harvesting operations are increasingly used to restore sensitive habitats such as longleaf pine (Pinus palustris Mill.) ecosystems. However, logging companies are often functionally limited by operational costs and site-specific productivity potential. By employing a time study, this project quantified the cost and productivity of a two-person logging crew using conventional equipment in a South Carolina southern pine timber harvest used to restore a longleaf pine savanna ecosystem. Our study found that the feller-buncher, grapple skidder, and knuckle-boom loader produced, on average, 60.7, 23.6, and 45.2 tonnes per Productive Machine Hour (PMH), respectively. When the knuckle-boom loader was exclusively loading log trucks, productivity increased to 48.4 tonnes per PMH. Additionally, a machine rate analysis found that the total cost for each machine was 108.83 USD, 122.92 USD, and 121.25 USD per PMH, respectively, with a total per tonne cost of cutting, skidding, and loading amounting to 9.68 USD. Our findings indicate that restoration harvesting conducted in this manner under similar environmental conditions and price points may remain profitable for both landowners and logging companies. Moreover, the limitations of operating with a two-person crew resulted in minimal negative effects for both profitability and productivity, making it a viable option for similar restoration operations.