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31 pages, 3850 KiB

Open AccessArticle

Physiological Mechanisms of Foliage Recovery after Spring or Fall Crown Scorch in Young Longleaf Pine (Pinus palustris Mill.)

by Mary Anne S. Sayer, Michael C. Tyree, Eric A. Kuehler, John K. Jackson and Dylan N. Dillaway

Forests 2020, 11(2), 208; https://doi.org/10.3390/f11020208 - 12 Feb 2020

Cited by 11 | Viewed by 2333

Abstract

We hypothesized that physiological and morphological responses to prescribed fire support the post-scorch foliage recovery and growth of young longleaf pine. Two studies conducted in central Louisiana identified three means of foliage regrowth after fire that included an increase in the gas exchange [...] Read more.

We hypothesized that physiological and morphological responses to prescribed fire support the post-scorch foliage recovery and growth of young longleaf pine. Two studies conducted in central Louisiana identified three means of foliage regrowth after fire that included an increase in the gas exchange rate of surviving foliage for 3 to 4 months after fire. Saplings also exhibited crown developmental responses to repeated fire that reduced the risk of future crown scorch. Starch reserves were a source of carbon for post-scorch foliage regrowth when fire was applied in the early growing season. However, the annual dynamics of starch accumulation and mobilization restricted its effectiveness for foliage regrowth when fire was applied late in the growing season. As such, post-scorch foliage regrowth became increasingly dependent on photosynthesis as the growing season progressed. Additionally, the loss of foliage by fire late in the growing season interrupted annual starch dynamics and created a starch void between the time of late growing season fire and mid-summer of the next year. The occurrence of drought during both studies revealed barriers to foliage reestablishment and normal stem growth among large saplings. In study 1, spring water deficit at the time of May fire was associated with high crown scorch and poor foliage and stem growth among large saplings. We attribute this lag in stem growth to three factors: little surviving foliage mass, low fascicle gas exchange rates, and poor post-scorch foliage recovery. In study 2, May fire during a short window of favorable burning conditions in the tenth month of a 20-month drought also reduced stem growth among large saplings but this growth loss was not due to poor post-scorch foliage recovery. Application of this information to prescribed fire guidelines will benefit young longleaf pine responses to fire and advance efforts to restore longleaf pine ecosystems. Full article

(This article belongs to the Special Issue Longleaf Pine)

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14 pages, 2301 KiB

Open AccessArticle

Intra-Annual Variation in Soil C, N and Nutrients Pools after Prescribed Fire in a Mississippi Longleaf Pine (Pinus palustris Mill.) Plantation

by John R. Butnor, Kurt H. Johnsen, Christopher A. Maier and C. Dana Nelson

Forests 2020, 11(2), 181; https://doi.org/10.3390/f11020181 - 6 Feb 2020

Cited by 11 | Viewed by 2671

Abstract

Prescribed fire is an essential tool that is widely used for longleaf pine (Pinus palustris Mill.) stand management; periodic burning serves to reduce competition from woody shrubs and fire-intolerant trees and enhance herbaceous diversity. Low-intensity, prescribed burning is thought to have minimal [...] Read more.

Prescribed fire is an essential tool that is widely used for longleaf pine (Pinus palustris Mill.) stand management; periodic burning serves to reduce competition from woody shrubs and fire-intolerant trees and enhance herbaceous diversity. Low-intensity, prescribed burning is thought to have minimal long-term impact on soil chemistry in southern pine forests, although few studies report the intra-annual variation in soil chemistry after burning. We monitored changes in C, N, oxidation resistant C (C_R), pH and elemental nutrients in the forest floor and soil (0–5, 5–10 cm depths) before and after burning (1, 3, 6, 12 months) in a mature longleaf pine plantation at the Harrison Experimental Forest, near Saucier, Mississippi. Prescribed fire consumed much of the forest floor (11.3 Mg ha⁻¹; −69%), increased soil pH and caused a pulse of C, N and elemental nutrients to flow to the near surface soils. In the initial one to three months post-burn coinciding with the start of the growing season, retention of nutrients by soil peaked. Most of the N (93%), Ca (88%), K (96%) and Mg (101%), roughly half of the P (48%) and Mn (52%) and 25% of the C lost from the forest floor were detected in the soil and apparently not lost to volatilization. By month 12, soil C and N pools were not different at depths of 0–5 cm but declined significantly below pre-burn levels at depths of 5–10 cm, C −36% (p < 0.0001), N −26% (p = 0.003), contrary to other examples in southern pine ecosystems. In the upper 5 cm of soil, only Cu (−49%) remained significantly lower than pre-burn contents by month 12, at depths of 5–10 cm, Cu (−76%), Fe (−22%), K (−51%), Mg (−57%), Mn (−82%) and P (−52%) remain lower at month 12 than pre-burn contents. Burning did not increase soil C_R content, conversely significant declines in C_R occurred. It appears that recovery of soil C and N pools post-burn will require more time on this site than other southern pine forests. Full article

(This article belongs to the Special Issue Longleaf Pine)

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24 pages, 1946 KiB

Open AccessArticle

The Persistence of Container Nursery Treatments on the Field Performance and Root System Morphology of Longleaf Pine Seedlings

by Shi-Jean S. Sung, R. Kasten Dumroese, Jeremiah R. Pinto and Mary Anne S. Sayer

Forests 2019, 10(9), 807; https://doi.org/10.3390/f10090807 - 17 Sep 2019

Cited by 11 | Viewed by 3140

Abstract

In recent decades, container stock has become the preferred plant material to regenerate longleaf pine (Pinus palustris Mill.) forests in the southeastern United States. We evaluated the effects of container nursery treatments on early and long-term field performance in central Louisiana. Seedlings [...] Read more.

In recent decades, container stock has become the preferred plant material to regenerate longleaf pine (Pinus palustris Mill.) forests in the southeastern United States. We evaluated the effects of container nursery treatments on early and long-term field performance in central Louisiana. Seedlings were grown in four cavity volumes (60–336 mL) with or without copper oxychloride root pruning (Cu or no-Cu) and fertilized at three nitrogen (N) rates. Across treatments, 91% of the seedlings emerged from the grass stage by the second field season, and 88% of the seedlings survived eight years after outplanting (Year 8). Seedlings grown in the largest cavities had greater total heights and stem diameters than those cultured in the 60- and 95-mL cavities through Year 8. Seedlings receiving the least amount of N in the nursery were consistently smaller in stature through Year 8 than seedlings receiving more N. Field growth was unaffected by copper root pruning through Year 8. Foliar mineral nutrient concentrations and seedling nutrient contents of Year 2 seedlings did not respond to nursery treatments. Independent of nursery treatments, seedlings excavated in Year 2 had at least 60% of their first-order lateral roots (FOLRs) originating from the top 4.0 cm of the taproots. The Cu-root-pruned seedlings had twofold the percentage of FOLRs egressed from the top 8.0 cm of the root plug when compared with the no-Cu seedlings. Moreover, the Cu root pruning treatment decreased the percentage of root plug biomass allocated to FOLRs, total within root plug FOLR lengths, and FOLR deformity index. The effects of increasing cavity volume or N rate on the root plug FOLR variables were opposite those of the Cu root pruning treatment. Our results suggest that a tradeoff may exist between seedling stature and a more natural FOLR morphology in outplanted container longleaf pine seedlings. Full article

(This article belongs to the Special Issue Longleaf Pine)

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20 pages, 3254 KiB

Open AccessArticle

Longleaf Pine Patch Dynamics Influence Ground-Layer Vegetation in Old-Growth Pine Savanna

by Maria Paula Mugnani, Kevin M. Robertson, Deborah L. Miller and William J. Platt

Forests 2019, 10(5), 389; https://doi.org/10.3390/f10050389 - 30 Apr 2019

Cited by 12 | Viewed by 3727

Abstract

Old-growth longleaf pine savannas are characterized by diverse ground-layer plant communities comprised of graminoids, forbs, and woody plants. These communities co-exist with variable-aged patches containing similar-aged trees of longleaf pine (Pinus palustris Mill.). We tested the conceptual model that physical conditions related [...] Read more.

Old-growth longleaf pine savannas are characterized by diverse ground-layer plant communities comprised of graminoids, forbs, and woody plants. These communities co-exist with variable-aged patches containing similar-aged trees of longleaf pine (Pinus palustris Mill.). We tested the conceptual model that physical conditions related to the cycle of longleaf pine regeneration (stand structure, soil attributes, fire effects, and light) influence plant species’ composition and spatial heterogeneity of ground-layer vegetation. We used a chrono-sequence approach in which local patches represented six stages of the regeneration cycle, from open areas without trees (gaps) to trees several centuries old, based on a 40-year population study and increment cores of trees. We measured soil characteristics, patch stand structure, fuel loads and consumption during fires, plant productivity, and ground-layer plant species composition. Patch characteristics (e.g., tree density, basal diameter, soil carbon, and fire heat release) indicated a cyclical pattern that corresponded to the establishment, growth, and mortality of trees over a period of approximately three centuries. We found that plants in the families Fabaceae and Asteraceae and certain genera were significantly associated with a particular patch stage or ranges of patch stages, presumably responding to changes in physical conditions of patches over time. However, whole-community-level analyses did not indicate associations between the patch stage and distinct plant communities. Our study indicates that changes in composition and the structure of pine patches contribute to patterns in spatial and temporal heterogeneity in physical characteristics, fire regimes, and species composition of the ground-layer vegetation in old-growth pine savanna. Full article

(This article belongs to the Special Issue Longleaf Pine)

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16 pages, 2754 KiB

Open AccessArticle

Patchy Fires Promote Regeneration of Longleaf Pine (Pinus palustris Mill.) in Pine Savannas

by Kevin M. Robertson, William J. Platt and Charles E. Faires

Forests 2019, 10(5), 367; https://doi.org/10.3390/f10050367 - 28 Apr 2019

Cited by 35 | Viewed by 5078

Abstract

Research Highlights: Spatial patterns of fire spread and severity influence survival of juvenile pines in longleaf pine savannas. Small areas that do not burn during frequent fires facilitate formation of patches of even-aged longleaf pine juveniles. These regeneration patches are especially associated [...] Read more.

Research Highlights: Spatial patterns of fire spread and severity influence survival of juvenile pines in longleaf pine savannas. Small areas that do not burn during frequent fires facilitate formation of patches of even-aged longleaf pine juveniles. These regeneration patches are especially associated with inner portions of openings (gaps) and where canopy trees have died in recent decades. Patterns of prescribed fire can thus have an important influence on stand dynamics of the dominant tree in pine savannas. Background and Objectives: Savannas are characterized by bottlenecks to tree regeneration. In pine savannas, longleaf pine is noted for recruitment in discrete clusters located within gaps away from canopy trees. Various mechanisms promoting this pattern have been hypothesized: light limitations, soil moisture, soil nutrients, pine needle mulching, competition with canopy tree roots, and fire severity associated with pine needle litter. We tested the hypothesis that regeneration patches are associated with areas that remain unburned during some prescribed fires, as mediated by gaps in the canopy, especially inner portions of gaps, and areas re-opened by death of canopy trees. Materials and Methods: We mapped areas that were unburned during prescribed fires applied at 1–2 year intervals from 2005–2018 in an old-growth pine savanna in Georgia, USA. We compared the maps to locations of longleaf pine juveniles (<1.5 m height) measured in 2018 and canopy cover and canopy tree deaths using a long-term (40 year) tree census. Results: Logistic regression analysis showed juveniles to be associated with unburned areas, gaps, inner gaps, and areas where canopy trees died. Conclusions: Patterns of fire spread and severity limit survival of longleaf pine juveniles to patches away from canopy trees, especially where canopy trees have died in recent decades. These processes contribute to a buffering mechanism that maintains the savanna structure and prevents transition to closed canopy forest or open grassland communities. Full article

(This article belongs to the Special Issue Longleaf Pine)

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11 pages, 1892 KiB

Open AccessArticle

Genetic Variation in Water-Use Efficiency (WUE) and Growth in Mature Longleaf Pine

by Ana C. Castillo, Barry Goldfarb, Kurt H. Johnsen, James H. Roberds and C. Dana Nelson

Forests 2018, 9(11), 727; https://doi.org/10.3390/f9110727 - 21 Nov 2018

Cited by 7 | Viewed by 3959

Abstract

The genetic and physiological quality of seedlings is a critical component for longleaf pine (Pinus palustris Mill.) restoration, because planting genetic material that is adapted to environmental stress is required for long-term restoration success. Planting trees that exhibit high water-use efficiency (WUE) [...] Read more.

The genetic and physiological quality of seedlings is a critical component for longleaf pine (Pinus palustris Mill.) restoration, because planting genetic material that is adapted to environmental stress is required for long-term restoration success. Planting trees that exhibit high water-use efficiency (WUE) is a practice that could maximize this species’ survival and growth in a changing climate. Our study evaluates genetic variation in WUE and growth, as well as WUE-growth relationships, a key step to determine potential for breeding and planting trees with high WUE. We measured carbon isotope discrimination (∆)—a proxy for WUE—in 106 longleaf pine increment cores extracted from trees belonging to nine full-sib families. Tree diameter and total tree height were also measured at ages 7, 17, 30 and 40 years. Each increment core was divided into segments corresponding to ages 7–17, 18–30 and 31–40, representing early, intermediate and mature growth of the trees. We identified significant genetic variation in DBH and WUE among families that merit further exploration for identifying trees that can potentially withstand drought stress. Mean family growth rates were not associated with mean family values for carbon isotope discrimination. Family variation in both diameter growth and WUE but no relationship between family values for these traits, suggests it is possible to improve longleaf pines in both diameter growth and WUE through appropriate breeding. Full article

(This article belongs to the Special Issue Longleaf Pine)

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12 pages, 2640 KiB

Open AccessArticle

Belowground Carbohydrate Reserves of Mature Southern Pines Reflect Seedling Strategy to Evolutionary History of Disturbance

by Joshua T. Mims, Joseph J. O’Brien and Doug P. Aubrey

Forests 2018, 9(10), 653; https://doi.org/10.3390/f9100653 - 19 Oct 2018

Cited by 7 | Viewed by 3067

Abstract

Carbohydrate reserves provide advantages for mature trees experiencing frequent disturbances; however, it is unclear if selective pressures operate on this characteristic at the seedling or mature life history stage. We hypothesized that natural selection has favored carbohydrate reserves in species that have an [...] Read more.

Carbohydrate reserves provide advantages for mature trees experiencing frequent disturbances; however, it is unclear if selective pressures operate on this characteristic at the seedling or mature life history stage. We hypothesized that natural selection has favored carbohydrate reserves in species that have an evolutionary history of frequent disturbance and tested this using three southern pine species that have evolved across a continuum of fire frequencies. Longleaf pine (Pinus palustris) roots exhibited higher maximum starch concentrations than slash (P. elliottii) and loblolly (P. taeda), which were similar. Longleaf also relied on starch reserves in roots more than slash or loblolly, depleting 64, 41, and 23 mg g⁻¹ of starch, respectively, between seasonal maximum and minimum, which represented 52%, 45%, and 26% of reserves, respectively. Starch reserves in stems did not differ among species or exhibit temporal dynamics. Our results suggest that an evolutionary history of disturbance partly explains patterns of carbohydrate reserves observed in southern pines. However, similarities between slash and loblolly indicate that carbohydrate reserves do not strictly follow the continuum of disturbance frequencies among southern pine, but rather reflect the different seedling strategies exhibited by longleaf compared to those shared by slash and loblolly. We propose that the increased carbohydrate reserves in mature longleaf may simply be a relic of selective pressures imposed at the juvenile stage that are maintained through development, thus allowing mature trees to be more resilient and to recover from chronic disturbances such as frequent fire. Full article

(This article belongs to the Special Issue Longleaf Pine)

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13 pages, 1849 KiB

Open AccessArticle

Provenance Variation in Pinus palustris Foliar δ¹³C

by Lisa Samuelson, Kurt Johnsen, Tom Stokes, Peter Anderson and C. Dana Nelson

Forests 2018, 9(8), 466; https://doi.org/10.3390/f9080466 - 1 Aug 2018

Cited by 3 | Viewed by 3257

Abstract

Longleaf pine forests are currently being restored in the southern U.S. To aid in the deployment of longleaf pine under current and future climate conditions, we tested the hypothesis that genetic variability in foliar carbon isotope composition (δ¹³C) exists in this [...] Read more.

Longleaf pine forests are currently being restored in the southern U.S. To aid in the deployment of longleaf pine under current and future climate conditions, we tested the hypothesis that genetic variability in foliar carbon isotope composition (δ¹³C) exists in this species. Foliar δ¹³C, height and diameter were measured at ages of 5 and 6 years, and needle length, specific leaf weight (SLW) and foliar N concentration were measured at an age of 6 years in 16 longleaf pine families representing a large portion of the species’ range. Families were grown in common garden tests in North Carolina and Mississippi and grouped for analysis into six provenances based on climate, soils, and discontinuities in the species’ range. No genetic by environment interactions were observed. Greater foliar δ¹³C was observed in trees from the provenance consisting of the Piedmont and Montane Uplands than from the provenances representing the western and eastern Gulf Coastal Plains. Foliar δ¹³C was not significantly correlated to height at age 6, suggesting that it may be possible to select for improved foliar δ¹³C without sacrificing growth. These results represent a first step in identifying potential genetic variation in leaf water use efficiency and drought tolerance of longleaf pine. Full article

(This article belongs to the Special Issue Longleaf Pine)

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16 pages, 1973 KiB

Open AccessArticle

Fire Season, Overstory Density and Groundcover Composition Affect Understory Hardwood Sprout Demography in Longleaf Pine Woodlands

by Andrew W. Whelan, Seth W. Bigelow, Mary Frances Nieminen and Steven B. Jack

Forests 2018, 9(7), 423; https://doi.org/10.3390/f9070423 - 14 Jul 2018

Cited by 15 | Viewed by 4758

Abstract

Seasonal timing of prescribed fire and alterations to the structure and composition of fuels in savannas and woodlands can release understory hardwoods, potentially resulting in a global increase of closed-canopy forest and a loss of biodiversity. We hypothesized that growing-season fire, high overstory [...] Read more.

Seasonal timing of prescribed fire and alterations to the structure and composition of fuels in savannas and woodlands can release understory hardwoods, potentially resulting in a global increase of closed-canopy forest and a loss of biodiversity. We hypothesized that growing-season fire, high overstory density, and wiregrass presence in longleaf pine woodlands would reduce the number and stature of understory hardwoods, and that because evergreen hardwoods retain live leaves, dormant-season fire would reduce performance and survival of evergreen more than deciduous hardwoods. Understory hardwood survival and height were monitored over seven years in longleaf pine woodlands in southwest Georgia with a range of overstory density, groundcover composition, and season of application of prescribed fire. Hardwood stem survival decreased with increasing overstory density, and deciduous hardwoods were more abundant in the absence of wiregrass. Contrary to expectations, evergreen hardwood growth increased following dormant-season fire. Differences in hardwood stem survival and height suggest that low fire intensity in areas with low overstory density increase the risk that hardwoods will grow out of the understory. These results indicate a need for focused research into the effects of groundcover composition on hardwood stem dynamics and emphasize that adequate overstory density is important in longleaf ecosystem management. Full article

(This article belongs to the Special Issue Longleaf Pine)

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17 pages, 2147 KiB

Open AccessFeature PaperArticle

Local and General Above-Ground Biomass Functions for Pinus palustris Trees

by Carlos A. Gonzalez-Benecke, Dehai Zhao, Lisa J. Samuelson, Timothy A. Martin, Daniel J. Leduc and Steven B. Jack

Forests 2018, 9(6), 310; https://doi.org/10.3390/f9060310 - 1 Jun 2018

Cited by 19 | Viewed by 4101

Abstract

There is an increasing interest in estimating biomass for longleaf pine (Pinus palustris Mill.), an important tree species in the southeastern U.S. Most of the individual-tree allometric models available for the species are local, relying on stem diameter outside bark at breast [...] Read more.

There is an increasing interest in estimating biomass for longleaf pine (Pinus palustris Mill.), an important tree species in the southeastern U.S. Most of the individual-tree allometric models available for the species are local, relying on stem diameter outside bark at breast height (DBH) and total tree height (HT), but seldom include stand-level variables such as stand age, basal area or stand density. Using the biomass dataset of 296 longleaf pine trees sampled in the southeastern U.S. by different forestry research institutions, we developed a set of local and general systems of tree biomass equations to predict total tree total above-stump biomass, bole biomass outside bark, live branch biomass and live foliage biomass. The local systems were based on DBH or DBH and HT, and the general systems included in addition to DBH and HT, stand-level variables such as age, basal area and stand density. This paper reports the first set of general allometric equations reported for longleaf pine trees. These systems of biomass equations provide tools to support managers in making management decisions for the species in a variety of ecological, silvicultural and economics applications. The systems can be applied to trees growing over a large geographical area and having a wide range of ages and stand characteristics. Full article

(This article belongs to the Special Issue Longleaf Pine)

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