Longleaf Pine Research Articles

92 Health and Performance of Ewes in Woodland and Silvopasture Systems

Abstract The health and performance of small ruminants can be influenced by the type of vegetation available in the grazing lands, which are evolving from conventional sole pastures to other systems containing browse species, such as pastures incorporated with browse, silvopastures, and woodlands. However, how the type of grazing lands would impact animal performance and health is not documented well. The objective of this study was to determine the health and performance of ewe lambs in southern-pine silvopastures and woodlands. The study site consisted of pine silvopastures (3 plots, 0.4-ha each) planted with different cool- and warm-season forages, and woodlands (3 plots, 0.4-ha each) having numerous understory shrubs and herbaceous species. Katahdin-St. Croix-cross ewe lambs (n = 20; live weight – 29.4±1.03 kg., 5–6 months old) were rotationally stocked in study plots (10 animals/system) from May to August 2019. Both silvopasture and woodland systems consisted of 14-year-old longleaf (Pinus palustris Mill.) and loblolly pine (Pinus taeda L.) trees. Animal performance data [live weight (LW), body condition score (BCS), FAMACHA score, and fecal egg count] were collected every 14 days and blood samples collected at the beginning and on day 80 after they were stocked in the study plots. Blood samples were analyzed for PVC using centrifuge machine and other parameters in IDEXX. Data were analyzed using the multivariate analysis of variance in SAS 9.4. The silvopasture ewes gained more weight versus the woodland ewes (P < 0.0001). Fecal egg count was correlated negatively with live weight and BCS and positively with FAMACHA score in both groups (P < 0.05). Woodland ewes showed greater levels of RBC, hemoglobin, and lymphocyte, but less blood urea nitrogen (BUN), monocyte, and basophil than silvopasture ewes (P < 0.05). Results indicate that woodland ewes may need some supplement to improve their weight gain and BUN.

Temporal patterns of pollen shedding for longleaf pine (Pinus palustris) at the Escambia Experimental Forest in Alabama, USA

Longleaf pine is an important tree species in the southeastern United States and studying the temporal patterns of pollen shedding is crucial to a better understanding of its phenology and seed production. In this study, field observation data on the timing of pollen shedding from 1958 to 2013 were analyzed with reference to local weather conditions. Our results indicated that the time of peak pollen shedding after January 1 (TPPS) ranged from 53 days (about February 22) to 95 days (around April 5). There was no significant trend of decreasing TPPS. The number of days with the maximum air temperature above 0 °C was close to the TPPS. The accumulated maximum daily air temperature for the TPPS approximated an average of 1,342 °C. The TPPS declined with an increase in the average air temperature during winters. The time of 80% accumulated pollen density (TAPD) varied from 5 to 32 days, with an average of 13 days. Taylor’s power-law was evident in the TAPD data, with the time group of 10–15 days having an interval time of 2 years. Winter weather was not correlated with the TAPD. These results provide new information concerning the pollen phenology for longleaf pine trees.

Occurrence, density, and distribution of longleaf pine regeneration in southeastern forests: An assessment by forest type, disturbance and site quality

Regenerating longleaf pine is essential for the long-term sustainability of longleaf pine forest ecosystems and the important services those forests provide, particularly for endangered organisms. The objective of this study was to investigate the occurrence, density, and distribution of longleaf regeneration across a range of site quality, forest type, and disturbance regimes within the longleaf pine range from 1995 to 2019. We used 6,128 plots from multiple inventory cycles of the USDA Forest Service Forest Inventory and Analysis (FIA) dataset covering the entire longleaf pine range. The methods of analysis included logistic regression and the Inverse Distance Weighted (IDW) interpolation method. Two sets of measurements of 2,092 plots were used for change detection analysis. Longleaf regeneration was abundant in longleaf and loblolly pine-dominated stands. For a one-unit increase in the basal area ratio of longleaf pine trees in the plots, the probability of occurrence of longleaf pine seedlings and saplings increased up to 239% and 362%, respectively. The density and occurrence of longleaf regeneration were significantly greater on low-quality sites than on high-quality sites. Longleaf seedlings occurred with less frequency on disturbed sites, particularly by insects, diseases, and animals, than on undisturbed sites. Similarly, longleaf saplings were found with less frequency on sites disturbed by harvesting, weather, insects, diseases, and animals. We found a declining geographic range of longleaf pine trees, saplings, and seedlings during the 1995–2019 period. The density and ratio of longleaf seedlings decreased in about 25.2% and 14.0%, and increased in around 13.5% and 6.2% of the study area, respectively. Likewise, the density and ratio of longleaf saplings decreased in nearly 36.1% and 24.8% and increased in approximately 14.4% and 11.5% of the study area, respectively. Understanding the regeneration dynamics of longleaf pine is essential to restore and effectively regenerate longleaf pine forest ecosystems.

Ground flora cover, diversity, and life‐history trait representation after wind disturbance, salvage logging, and prescribed fire in a Pinus palustris woodland

AbstractQuestionSalvage logging and prescribed fire are commonly applied in forests worldwide, yet little is known about the combined impacts of these management actions on early‐successional ecosystems. We questioned how operational‐scale prescribed fire would affect ground flora cover, species diversity, and life‐history trait expression in Pinus palustris woodlands differentially impacted by an Enhanced Fujita scale 3 (EF3) tornado and salvage logging.LocationFall Line Hills, Alabama, USA (32°55ʹ30ʺ N, 87°24ʹ00ʺ W).MethodsThe composition and foliar cover of woody and herbaceous plants ≤1 m height were monitored before and after prescribed fire in 600 1‐m2 quadrats distributed throughout mature, wind‐disturbed, and salvage‐logged Pinus palustris woodlands. Plant taxa were categorized by growth habit and life form to aid interpretation of multivariate analyses used to illustrate differences in ground flora assemblages between disturbance categories.ResultsPrescribed fire reduced ground flora cover, but not diversity, which remained greatest in wind‐disturbed sites that were not salvage‐logged. Though ground flora assemblages remained disparate between disturbance categories, prescribed fire imposed some consistent selective pressures on plants with common life‐history strategies. Post‐fire understorey tree cover reductions coincided with increased shrub cover throughout the treatment area. Nonetheless, differences in graminoid cover were exaggerated after prescribed fire, and representation of the geophyte life form was relatively constant across space and time.ConclusionsPrescribed fire did not counteract salvage‐mediated reductions in ground flora diversity. Retention of downed deadwood maximized early‐successional plant diversity in wind‐disturbed sites. Trait‐based ground flora analyses enabled a more detailed understanding of disturbance effects than aggregate metrics of foliar cover and diversity. In ecosystems with high floristic diversity, grouping plants by common life‐history traits can provide a simple and effective means to monitor impacts of management actions on ecosystem recovery.

Leaf traits and canopy structure together explain canopy functional diversity: an airborne remote sensing approach.

Plant functional diversity is strongly connected to photosynthetic carbon assimilation in terrestrial ecosystems. However, many of the plant functional traits that regulate photosynthetic capacity, including foliar nitrogen concentration and leaf mass per area, vary significantly between and within plant functional types and vertically through forest canopies, resulting in considerable landscape-scale heterogeneity in three dimensions. Hyperspectral imagery has been used extensively to quantify functional traits across a range of ecosystems but is generally limited to providing information for top of canopy leaves only. On the other hand, lidar data can be used to retrieve the vertical structure of forest canopies. Because these data are rarely collected at the same time, there are unanswered questions about the effect of forest structure on the three -dimensional spatial patterns of functional traits across ecosystems. In the United States, the National Ecological Observatory Network's Airborne Observation Platform (NEON AOP) provides an opportunity to address this structure-function relationship by collecting lidar and hyperspectral data together across a variety of ecoregions. With a fusion of hyperspectral and lidar data from the NEON AOP and field-collected foliar trait data, we assessed the impacts of forest structure on spatial patterns of N. In addition, we examine the influence of abiotic gradients and management regimes on top-of-canopy percent N and total canopy N (i.e., the total amount of N [g/m2 ] within a forest canopy) at a NEON site consisting of a mosaic of open longleaf pine and dense broadleaf deciduous forests. Our resulting maps suggest that, in contrast to top of canopy values, total canopy N variation is dampened across this landscape resulting in relatively homogeneous spatial patterns. At the same time, we found that leaf functional diversity and canopy structural diversity showed distinct dendritic patterns related to the spatial distribution of plant functional types.

Fungal community structure and seasonal trajectories respond similarly to fire across pyrophilic ecosystems.

Fire alters microbial community composition, and is expected to increase in frequency due to climate change. Testing whether microbes in different ecosystems will respond similarly to increased fire disturbance is difficult though, because fires are often unpredictable and hard to manage. Fire recurrent or pyrophilic ecosystems, however, may be useful models for testing the effects of frequent disturbance on microbes. We hypothesized that across pyrophilic ecosystems, fire would drive similar alterations to fungal communities, including altering seasonal community dynamics. We tested fire's effects on fungal communities in two pyrophilic ecosystems, a longleaf pine savanna and tallgrass prairie. Fire caused similar fungal community shifts, including (i) driving immediate changes that favored taxa able to survive fire and take advantage of post-fire environments and (ii) altering seasonal trajectories due to fire-associated changes to soil nutrient availability. This suggests that fire has predictable effects on fungal community structure and intra-annual community dynamics in pyrophilic ecosystems, and that these changes could significantly alter fungal function. Parallel fire responses in these key microbes may also suggest that recurrent fires drive convergent changes across ecosystems, including less fire-frequented systems that may start burning more often due to climate change.

Tree, stand, and landscape factors contributing to hurricane damage in a coastal plain forest: Post-hurricane assessment in a longleaf pine landscape

Hurricanes occur regularly along the Atlantic and Gulf Coasts of the southern United States and can have intense ecological and economic impacts on forests. Frequent low-intensity fire plays a well-known role in many coastal plain upland forests, including longleaf pine (Pinus palustris). Hurricanes may also play a critical role in shaping these communities. Field studies investigating wind susceptibility of coastal tree species often rank longleaf pine among the most wind-resistant species. This assertion is usually based on analyses that evaluate whether the fraction of downed trees is greater than expected by chance. However, tree species’ associations with different soil types and landforms, and differences in tree size and spatial distribution can confound inferences. Accounting for tree, stand, and landscape factors can improve estimates of species differences in probability of wind damage. Following Hurricane Michael in 2018, we used observations from more than 3000 trees and generalized linear mixed models to investigate how tree-level factors (species and DBH), stand-level factors (stand density and soil type), and landscape-level factors (wind exposure and landscape configuration) affect tree vulnerability to hurricane winds in a longleaf pine-dominated landscape. Probability of damage varied between species, was dependent on soil type, and increased with increasing diameter for all species. Longleaf pine was in the lower range of treefall probability for all soil types and showed the lowest variability in wind susceptibility, confirming findings from other studies. However, we observed important interactions between species and soil types. Oak (Quercus spp.) species were more susceptible to treefall on drier soils, while pine (Pinus spp.) species were more resistant, suggesting that hurricanes, along with frequent fire, may play a role in shaping the landscape-scale structure of southeastern pine systems. Understanding the role of hurricanes in disturbance-prone forests can provide insight on the ecological processes structuring diverse coastal forest systems while informing activities critical for their management and conservation. Additionally, multi-aged silvicultural approaches may serve to increase the hurricane resilience of forests.

Association of Recent Incidence of Foliar Disease in Pine Species in the Southeastern United States with Tree and Climate Variables

Pine forests in the southern United States are a major contributor to the global economy. Through the last three decades, however, there have been concerns about the decline of pine forests attributed mostly to pests and pathogens. A combination of biotic agents and environmental factors and their interaction often influences outbreaks and the resultant damage in the forests. Southern pines experience periodic mortality from bark beetles and root rot fungi and losses from fusiform rust and pitch canker have long been important for management. In recent years, there is also growing evidence of increasing damage from foliar disease in southern pines. Early detection of diseases following changes in foliar characteristics and assessment of potential risks will help us better utilize our resources and manage these forests sustainably. In this study, we used Forest Inventory and Analysis (FIA) data to explore the intensity of foliar disease in three common pines: loblolly (Pinus taeda L.), longleaf (Pinus palustris Mill.), and slash (Pinus elliottii Engelm.) in spatial and temporal terms using tree-level and climatic variables. Results from a tree-level model suggests that crown ratio may be an important factor in pine foliar disease (p < 0.1). We applied the MaxEnt model, a presence-only species distribution model (SDM), to explore any association of foliar disease incidences with the climatic variables at a landscape level. Results indicate that mean dew point temperature, maximum vapor pressure deficit, and precipitation during cold months had more influence over disease incidences than other climatic variables. While the sample size is limited as this is an emerging disease in the region, our study provides a basis for further exploration of disease detection methods, disease etiology studies, and hazard mapping.

The influence of prescribed fire on site selection in snakes in the longleaf pine ecosystem

Prescribed fire is an essential tool for the restoration and maintenance of the longleaf pine (Pinus palustris) ecosystem. This type of management benefits wildlife species that are frequently associated with open canopy pine forests in the Southeastern U.S., including upland snakes. But few studies have examined the long term effects of prescribed fire (i.e., fire frequency over time) on snake occurrences at local and landscape scales. Likewise, comprehensive data are lacking on the response of snakes to individual prescribed burns (i.e., how long after a fire does a snake occupy a location). To investigate snake responses to these two factors, we used radio-telemetry data for five species of snakes, including three species of open-canopied forest specialists and two species that occur more broadly in upland forests (i.e., generalists), on a large site managed with prescribed fire. We hypothesized that open-canopied forest specialists, eastern diamondback rattlesnake (Crotalus adamanteus), Florida pine snake (Pituophis melanoleucus), and eastern coachwhip (Coluber flagellum) would select more frequently burned locations over less frequently burned locations and would occupy locations sooner after a fire than generalist species, eastern kingsnake (Lampropeltis getula) and gray ratsnake (Pantherophis allegheniensis). We used spatial data collected from previous snake radio-telemetry studies conducted over a nine year period (2003–2012) and annual burn data from 1994 to 2012. We used compositional analysis to evaluate snake use (selection) versus availability of locations based on fire frequency at different spatial scales (home range and landscape). As predicted, open-canopied forest specialists selected locations with more frequent fire (≤2.5 y return interval) significantly more often than locations with less frequent fire (≥3.3 y return interval; F7, 18 = 9.06, p < 0.0001). Whereas habitat generalists selected locations with fires across a broader spectrum of frequencies (every 2–10 y) significantly more often than locations that were not burned in 10 years (no burn) or those burned most frequently (1.4 y return interval; F7, 21 = 5.94, p < 0.001). The three open-canopied forest specialists, as well as the generalist, eastern kingsnake, predominantly used locations within two years after a burn (eastern diamondback rattlesnake, 81% of locations; Florida pine snake, 91% of locations; eastern coachwhip, 98% of locations; and eastern kingsnake, 91% of locations. The generalist, grayrat snake, selected locations where time since burn was less than two years (53.8% of locations), as well as, locations that had not been burned in 10 years (23.5%). Our data suggest that forest management programs that include prescribed fire with short burn return intervals (<3 y) over long time periods would benefit both open-canopied forest specialists and generalist snake species that use open-canopied forests.

Changes in Tree Canopy, Groundcover, and Avian Community Following Restoration of a Montane Longleaf Pine Woodland

Fire suppression and hardwood encroachment are two of the most significant threats to the imperiled, fire-dependent montane longleaf pine ecosystem. We examined the effects of restoration of a montane longleaf pine forest in Paulding County, Georgia, U.S.A. on tree canopy, groundcover and bird communities over a decade. The restoration included a program of prescribed fire and selective thinning to reduce tree canopy density and reduce or remove offsite species. Several conservation goals were met including the recovery of characteristic tree composition and groundcover. Birds responded with sharp increases in richness and abundance, with many shrub and woodland dependent species of high conservation value detected post-restoration. Our research demonstrates these sites are easily restorable and such projects will likely yield significant gains for conservation.

Factors affecting the spatial density of longleaf pine plantations under the Conservation Reserve Program in Georgia, United States

Several initiatives are promoting longleaf pine (Pinus palustris) restoration in the Southern United States for conserving biodiversity and mitigating climate change. Under the Conservation Reserve Program (CRP), landowners plant longleaf pine on farmlands and pasturelands in exchange for annual payments and other financial incentives. While the introduction of this program was an important step towards longleaf pine restoration, there exists a necessity to understand how the decisions of landowners to enroll in CRP are manifested over space. An understanding about the role of a range of factors on the spatial density of longleaf pine plantations enrolled under CRP would help in prioritizing locations for longleaf pine plantations, thereby increasing the efficacy of conservation-related resources. We evaluate the effects of socioeconomic, topographic, and distance variables on the spatial density of longleaf plantations enrolled under CRP using clustered point process model in Georgia, a state with 47% of the total acreage under CRP-supported longleaf plantations. Only 30% of the current longleaf pine locations under CRP were within the Significant Geographic Area. About 86% of current longleaf plantations under CRP are present on former croplands and pasturelands. The spatial density of longleaf pine plantations is negatively associated with the distance from cropland and pastureland and positively associated with land capability classes, and distance from the sawmills. Longleaf pine restoration efforts should focus on those croplands or pasturelands which are closer to existing CRP-supported plantations, located on lower soil capability classes, and are far from wood consuming mills. Our study would support current programs that are supporting longleaf pine restoration in the Southern United States.

Adsorption of Chromium from Aqueous Solution by Lignocellulosic Biomass (Pinus palustris): Studies on Equilibrium Isotherm, and Kinetics

Different methods to convert biomass into useful materials and products without generating pollutants will be useful for global environmental protection. The present study deals with the preparation of adsorbent from a suitable lignocellulosic biomass, Pinus palustris seeds. The adsorbent thus prepared will be used for the removal of heavy metals from aqueous solutions. Factors influencing the adsorption characteristics under batch conditions were studied for chromium concentrations in range of 30 – 150 ppm. The studies were conducted to optimize the size of the adsorbent, temperature and contact time. The maximum adsorption is attained at a pH of 6.5 and a dosage of 3g. The effective temperature for the reaction was at 37oC. The removal percentage increase when the optimized condition of different parameters such as size, temperature, contact time, concentration, pH and dosage. The adsorption isotherms showed that the Freundlich Isotherm is a better adsorption model and the characteristic parameters were determined. The results of the kinetic models showed that the pseudo second order kinetics was found to correlate with the experimental data. The present analysis, the absorbent that is produced from Pinus palustris seed has an efficient adsorption for chromium.

An Eddy Covariance Mesonet For Measuring Greenhouse Gas Fluxes in Coastal South Carolina

Coastal ecosystems are vulnerable to climate change and have been identified as sources of uncertainty in the global carbon budget. Here we introduce a recently established mesonet of eddy covariance towers in South Carolina and describe the sensor arrays and data workflow used to produce three site-years of flux observations in coastal ecosystems. The tower sites represent tidal salt marsh (US-HB1), mature longleaf pine forest (US-HB2), and longleaf pine restoration (replanted clearcut; US-HB3). Coastal ecosystems remain less represented in climate studies despite their potential to sequester large amounts of carbon. Our goal in publishing this open access dataset is to contribute observations in understudied coastal ecosystems to facilitate synthesis and modeling analyses that advance carbon cycle science.

Intraspecific trait variability shapes leaf trait response to altered fire regimes.

Understanding impacts of altered disturbance regimes on community structure and function is a key goal for community ecology. Functional traits link species composition to ecosystem functioning. Changes in the distribution of functional traits at community scales in response to disturbance can be driven not only by shifts in species composition, but also by shifts in intraspecific trait values. Understanding the relative importance of these two processes has important implications for predicting community responses to altered disturbance regimes. We experimentally manipulated fire return intervals in replicated blocks of a fire-adapted, longleaf pine (Pinus palustris) ecosystem in North Carolina, USA and measured specific leaf area (SLA), leaf dry matter content (LDMC) and compositional responses along a lowland to upland gradient over a 4 year period. Plots were burned between zero and four times. Using a trait-based approach, we simulate hypothetical scenarios which allow species presence, abundance or trait values to vary over time and compare these with observed traits to understand the relative contributions of each of these three processes to observed trait patterns at the study site. We addressed the following questions. (1) How do changes in the fire regime affect community composition, structure and community-level trait responses? (2) Are these effects consistent across a gradient of fire intensity? (3) What are the relative contributions of species turnover, changes in abundance and changes in intraspecific trait values to observed changes in community-weighted mean (CWM) traits in response to altered fire regime? We found strong evidence that altered fire return interval impacted understorey plant communities. The number of fires a plot experienced significantly affected the magnitude of its compositional change and shifted the ecotone boundary separating shrub-dominated lowland areas from grass-dominated upland areas, with suppression sites (0 burns) experiencing an upland shift and annual burn sites a lowland shift. We found significant effects of burn regimes on the CWM of SLA, and that observed shifts in both SLA and LDMC were driven primarily by intraspecific changes in trait values. In a fire-adapted ecosystem, increased fire frequency altered community composition and structure of the ecosystem through changes in the position of the shrub line. We also found that plant traits responded directionally to increased fire frequency, with SLA decreasing in response to fire frequency across the environmental gradient. For both SLA and LDMC, nearly all of the observed changes in CWM traits were driven by intraspecific variation.

Fledgling Bachman’s Sparrows in a longleaf pine ecosystem: survival, movements, and habitat selection

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Diurnal Pine Bark Structure Dynamics Affect Properties Relevant to Firebrand Generation

Firebrands are an important agent of wildfire spread and structure fire ignitions at the wildland urban interface. Bark flake morphology has been highlighted as an important yet poorly characterized factor in firebrand generation, transport, deposition, and ignition of unburned material. Using pine species where bark flakes are the documented source of embers, we conducted experiments to investigate how bark structure changes in response to diurnal drying. Over a three-day period in a longleaf pine (Pinus palustris Mill.) stand in Florida, we recorded changes in temperature, moisture content, and structure of bark across different facing aspects of mature pine trees to examine the effects of varying solar exposure on bark moisture. We further compared results to bark drying in a pitch pine (Pinus rigida Mill.) plantation in New Jersey. Under all conditions, bark peeled and lifted away from the tree trunk over the study periods. Tree bole aspect and the time of day interacted to significantly affect bark peeling. General temperature increases and moisture content decreases were significantly different between east and west aspects in pitch pine, and with time of day and aspect in longleaf pine. These results illustrate that bark moisture and flakiness is highly dynamic on short time scales, driven largely by solar exposure. These diurnal changes likely influence the probability of firebrand production during fire events via controls on moisture (ignition) and peeling (lofting).

Xeric Tree Populations Exhibit Delayed Summer Depletion of Root Starch Relative to Mesic Counterparts

Research linking soil moisture availability to nonstructural carbohydrate (NSC) storage suggests greater NSC reserves promote survival under acute water stress, but little is known about how NSC allocation responds to long-term differences in water availabilty. We hypothesized populations experiencing chronic or frequent water stress shift carbon allocation to build greater NSC reserves for increased survival probability during drought relative to populations rarely experiencing water stress. Over a year, we measured soluble sugar and starch concentrations from branches, stems, and coarse roots of mature Pinus palustris trees at two sites differing in long-term soil moisture availability. Xeric and mesic populations exhibited a cycle of summer depletion-winter accumulation in root starch. Xeric populations reached a maximum root starch concentration approximately 1–2 months later than mesic populations, indicating delayed summer depletion. Xeric and mesic populations reached the same minimum root starch at similar times, suggesting extended winter accumulation for xeric populations. These results suggest seasonal mobilization from root starch is compressed into a shorter interval for xeric populations instead of consistently greater reserves as hypothesized. Seasonal trends differed little between xeric and mesic populations for starch and sugars, suggesting the importance of roots in seasonal carbon dynamics and the primacy of starch for storage. If roots are the primary organ for longterm storage, then our results suggest that whole-plant mobilization and allocation respond to chronic differences in water availability.

Rainfall interception and redistribution by a common North American understory and pasture forb, &amp;lt;i&amp;gt;Eupatorium capillifolium&amp;lt;/i&amp;gt; (Lam. dogfennel)

Abstract. In vegetated landscapes, rain must pass through plant canopies and litter to enter soils. As a result, some rainwater is returned to the atmosphere (i.e., interception, I) and the remainder is partitioned into a canopy (and gap) drip flux (i.e., throughfall) or drained down the stem (i.e., stemflow). Current theoretical and numerical modeling frameworks for this process are almost exclusively based on data from woody overstory plants. However, herbaceous plants often populate the understory and are the primary cover for important ecosystems (e.g., grasslands and croplands). This study investigates how overstory throughfall (PT,o) is partitioned into understory I, throughfall (PT) and stemflow (PS) by a dominant forb in disturbed urban forests (as well as grasslands and pasturelands), Eupatorium capillifolium (Lam., dogfennel). Dogfennel density at the site was 56 770 stems ha−1, enabling water storage capacities for leaves and stems of 0.90±0.04 and 0.43±0.02 mm, respectively. As direct measurement of PT,o (using methods such as tipping buckets or bottles) would remove PT,o or disturb the understory partitioning of PT,o, overstory throughfall was modeled (PT,o′) using on-site observations of PT,o from a previous field campaign. Relying on modeled PT,o′, rather than on observations of PT,o directly above individual plants means that significant uncertainty remains with respect to (i) small-scale relative values of PT and PS and (ii) factors driving PS variability among individual dogfennel plants. Indeed, PS data from individual plants were highly skewed, where the mean PS:PT,o′ per plant was 36.8 %, but the median was 7.6 % (2.8 %–27.2 % interquartile range) and the total over the study period was 7.9 %. PS variability (n=30 plants) was high (CV &gt; 200 %) and may hypothetically be explained by fine-scale spatiotemporal patterns in actual overstory throughfall (as no plant structural factors explained the variability). The total PT:PT,o′ was 71 % (median PT:PT,o′ per gauge was 72 %, with a 59 %–91 % interquartile range). Occult precipitation (mixed dew and light rain events) occurred during the study period, revealing that dogfennel can capture and drain dew to their stem base as PS. Dew-induced PS may help explain dogfennel's improved invasion efficacy during droughts (as it tends to be one of the most problematic weeds in the improved grazing systems in the southeastern US). Overall, dogfennel's precipitation partitioning differed markedly from the site's overstory trees (Pinus palustris), and a discussion of the limited literature suggests that these differences may exist across vegetated ecosystems. Thus, more research on herbaceous plant canopy interactions with precipitation is merited.

The relationship between upland hardwood distribution and avian occupancy in fire-maintained longleaf pine forests

Prescribed fire and other forest management practices aimed at restoring longleaf pine (Pinus palustris) communities often focus on the reduction, or removal, of upland hardwoods with the goal of providing habitat for threatened and endangered plant and animal species, including the federally endangered red-cockaded woodpecker (Leuconotopicus borealis), and restoring forests to pre-settlement conditions. Although contemporary restoration and management practices benefit species dependent on the resulting conditions, recent research has called attention to the ecological value of retaining upland hardwoods, especially for mast-dependent wildlife (e.g., fox squirrels [Sciurus niger]). Moreover, retention of indigenous hardwoods in upland longleaf pine communities may benefit a variety of birds. We used fixed-radius, breeding season point counts to sample the presence-absence of 15 avian species and assessed forest composition and structure around each point. We developed single-season single-species occupancy models with an emphasis on the influence of overstory hardwood cover on occupancy. Due to issues with model fit, we were unable to model occupancy for 3 of the 15 focal species. Occupancy probabilities for 6 out of the 12 focal species were positively influenced by overstory hardwood cover or stem density, whereas occupancy probabilities of 4 out of 12 of the focal species was negatively influenced by hardwood cover or stem density. Overstory hardwood cover between 5 and 15% resulted in high occupancy probabilities for the species that were positively influenced but did not result in substantially low occupancy probabilities for the species that were negatively influenced. Longleaf pine uplands with lower and upper bounds of 5% to 15% hardwood overstory cover with hardwood stem densities of ≤250 stems/ha could be targeted to provide habitat for the greatest diversity of birds while avoiding negative impact to species associated with upland longleaf pine communities.

Apparent Resilience to Fire of Native Bee (Hymenoptera: Apoidea) Communities from Upland Longleaf Pine Forests in Louisiana and Mississippi

Controlled burning is an essential tool for restoration and management of Pinus palustris (Longleaf Pine) habitats, yet effects of controlled burning on insect species, including pollinators, are rarely considered in conservation planning. We used blue vane traps to sample native bees (Hymenoptera: Apoidea) at recently burned and unburned sites in 2 Longleaf Pine upland forests in Mississippi and Louisiana. Our objective was to quantify short-term effects of controlled burns given fire-return intervals of 1–2 years are now regularly employed to manage Longleaf Pine woodlands. We sampled during 2016 and 2017 and collected 1777 native bees, representing 43 species. Recent fire was found to have no clear effect on species composition, richness, or community structure. Overall, bee communities from burned and unburned sites were similar. Even the community collected from a site that had remained unburned for 8 years was only marginally different from the others. These results suggest that native bee communities may be resilient to low intensity burns.