Population viability analyses are useful tools to predict abundance and extinction risk for imper... more Population viability analyses are useful tools to predict abundance and extinction risk for imperiled species. In southeastern North America, the federally threatened gopher tortoise (Gopherus polyphemus) is a keystone species in the diverse and imperiled longleaf pine (Pinus palustris) ecosystem, and researchers have suggested that tortoise populations are declining and characterized by high extinction risk. We report results from a 30-year demographic study of gopher tortoises in southern Alabama (1991-2020), where 3 populations have been stable and 3 others have declined. To better understand the demographic vital rates associated with stable and declining tortoise populations, we used a multi-state hierarchical markrecapture model to estimate sex-and stage-specific patterns of demographic vital rates at each population. We then built a predictive population model to project population dynamics and evaluate extinction risk in a population viability context. Population structure did not change significantly in stable populations, but juveniles became less abundant in declining populations over 30 years. Apparent survival varied by age, sex, and site; adults had higher survival than juveniles, but female survival was substantially lower in declining populations than in stable ones. Using simulations, we predicted that stable populations with high female survival would persist over the next 100 years but sites with lower female survival would decline, become male-biased, and be at high risk of extirpation. Stable populations were most sensitive to changes in apparent survival of adult females. Because local populations varied greatly in vital rates, our analysis improves upon previous demographic models for northern populations of gopher tortoises by accounting for population-level variation in demographic patterns and, counter to previous model predictions, suggests that small tortoise populations can persist when habitat is managed effectively.
... Ecology 56: 92-104. ROBERT WILLIAM CRUDEN AND SHARON MARIE HERMANN-PARKER, Department of Bota... more ... Ecology 56: 92-104. ROBERT WILLIAM CRUDEN AND SHARON MARIE HERMANN-PARKER, Department of Botany, Univer-sity of Iowa, Iowa City, Iowa 52242. ... 3, Norwood, Massachusetts, Norwood Press), White (1941, Brit. Birds 34: 179), Williamson (1941, Brit. ...
Although private properties are predicted to play an increasingly significant role in conservatio... more Although private properties are predicted to play an increasingly significant role in conservation, surveys of species of special concern are rare on these lands. We created a template for a multi-county survey of randomly selected sites and sampled for burrows of the gopher tortoise (Gopherus polyphemus) in south-central Georgia, USA. Current land use was strongly correlated with tortoise population condition.
Abstract Much attention has been given to the biology, ecology, and restoration of wiregrass beca... more Abstract Much attention has been given to the biology, ecology, and restoration of wiregrass because of the essential role it plays in the longleaf-slash pine ecosystem of the southeastern United States. A previous morphological study separated wiregrass into two ...
Young longleaf pine (Pinus palustris Mill.) plantations provide an important starting point for r... more Young longleaf pine (Pinus palustris Mill.) plantations provide an important starting point for restoration of longleaf pine ecosystems in the southeastern United States, with management goals often emphasizing restoration of vegetation composition and structure, as well as reestablishment of important ecological processes such as fire. We evaluated the influence of seasonal prescribed fire and overstory density on vegetation structure across overstory, midstory, and understory vegetation strata of a 23-year-old longleaf pine plantation in west-central Georgia. After three prescribed fire cycles through 8 years, we found significantly fewer broad-leaved woody stems in the midstory on both winter-and summer-burned plots compared to unburned plots, as well as fourfold greater herbaceous vegetation cover on burned plots compared to unburned plots. While we predicted that summer burning may be more important in controlling woody plants on low-density overstory plots compared to high-density plots, we found no meaningful interactions between fire seasonality and overstory density. Reductions in litter cover via prescribed fire appeared to be an important mechanism regulating herbaceous vegetation, suggesting that restoration should emphasize management of the forest floor to reduce litter cover and enhance opportunities for herbaceous plant establishment.
Anthropogenic inputs to cultivated sites were evident based on higher base saturation, pH, exchan... more Anthropogenic inputs to cultivated sites were evident based on higher base saturation, pH, exchangeable Ca, Mg, and K, bulk density, and P relative to uncultivated sites. • Soils in uncultivated sites had higher levels of C (biomass C, TOC, and POM C) compared to cultivated sites. • On average, Longleaf was 42% higher in biomass C and 59% higher in TOC than row cropping, and row cropping was 20% higher in bulk density and 33% higher in both TON and POM N relative to Longleaf. • More C and N stratification in Longleaf relative to cultivated sites based on larger stratification ratios of C and N pools.
Background/Question/Methods At Horseshoe Bend National Military Park in Alabama, the National Par... more Background/Question/Methods At Horseshoe Bend National Military Park in Alabama, the National Park Service (NPS) is pursuing ecological restoration. Fire was excluded for 75+ years and past agriculture occurred on a portion of the ~800 ha site. Historical records suggest that uplands were once open-canopied forests dominated by longleaf pine (Pinus palustris). Most longleaf were removed prior to 1930 and fire exclusion resulted in loblolly pine and native hardwoods encroaching from down-slope, moist areas. Ongoing efforts include reintroducing fire, minimizing encroaching hardwood species, and decreasing accumulated duff and litter. There is also a need to plant longleaf pine because the site lacks a sufficient seed source. The NPS hopes to reintroduce longleaf without dramatic, sudden visual changes to the landscape that surrounds a historically significant battleground. Traditional approaches to re-establishing most pine species include mechanical and/or chemical treatments to cle...
Background/Question/Methods Longleaf pine (Pinus palustris) ecosystems once dominated 60-90 milli... more Background/Question/Methods Longleaf pine (Pinus palustris) ecosystems once dominated 60-90 million acres and it is suggested that some remnant stands continue to support one of the most diverse floras in North America. It is well-known that longleaf pine ecosystems must burn frequently to maintain natural structure and function. This vegetation type ranks as one of the most fire-dependent ones in the country and must burn frequently (multiple times a decade) for natural structure and function to be maintained. Frequent fires maintain relatively low fuel loads and so many burns do not directly affect adult longleaf trees. However, other species are immediately affected by each fire that burns through a stand. Because many resident species are perennials that re-sprout after fires, it likely takes multiple burns to change the plant assemblage of the ground layer. There is a need is for better insight into fire effects on small woody stems in the ground layer. How and when fire is app...
Background/Question/Methods The first European settlers in what is now the southeastern United St... more Background/Question/Methods The first European settlers in what is now the southeastern United States were confronted with an upland forest that was dominated by longleaf pine (Pinus palustris Mill.). The pre-historical fire regime, both lightning and Native American-ignition, in the longleaf pine ecosystem was characterized by frequent burning, producing fire of low-moderate intensity. These fires were usually non-lethal to the dominant vegetation and maintained the forest structure of a herbaceous understory with scattered shrubs and an open-canopy. These fire-maintained forest ecosystems were essentially two-layered, consisting of a high canopy dominated by mature longleaf pine and an understory of grasses and herbs. While much is known about the longleaf pine overstory, less is known about the understory which develops under different overstory densities. In the early 1970's, a study was initiated in south Alabama, USA to examine the understory that develops with a dormant, ...
Background/Question/Methods In 2005, Van Lear and others highlighted the ecological significance ... more Background/Question/Methods In 2005, Van Lear and others highlighted the ecological significance of longleaf pine (Pinus palustris) forests for at-risk species dependent on this declining ecosystem. This paper reviewed losses of more than 97 percent acreage prior to 1700, championed restoration efforts for this once-common ecosystem, and called for increased attention to habitat requirements of associated at-risk species. In the current presentation, we explore habitat requirements of sixteen southeastern terrestrial vertebrates categorized as special concern, candidate, threatened, or endangered species. We also estimate ranges of factors in forest structure that are most relevant to some of the species. Results/Conclusions We determine that almost 90 percent of at-risk terrestrial vertebrates in this region share a general habitat requirement for grassland and/or open-canopied forest, during some or all of their lives. Open-canopied species include 4 birds, 2 mammals, 2 amphibians...
Background/Question/Methods Longleaf pine (Pinus palustris Mill.) was the dominant tree and ecosy... more Background/Question/Methods Longleaf pine (Pinus palustris Mill.) was the dominant tree and ecosystem on 20-30 million hectares across the southeastern US at the time of European settlement. Today, longleaf occupies less than 1 million hectares and a majority of these ecosystems are owned by non-industrial private landowners. Numerous efforts are underway to more than double the forested acreage in longleaf pine. This includes the assumption that natural stands will not be lost, which is currently NOT a reality. Naturally-regenerated longleaf pine stands, those quite often in the best ecological shape are lost at the rate of several thousand hectares/year. No efforts or programs exist to help those landowners that have these stands to retain them or to educate landowners about naturally regenerating their planted stands. Quite often, the advice they get is that longleaf is too difficult to manage that way and they clearcut their longleaf pine stand only to plant it back to longleaf....
Background/Question/Methods: In forests dependent on frequent burns, fire exclusion alters struct... more Background/Question/Methods: In forests dependent on frequent burns, fire exclusion alters structure and species composition as well as fuel loads. Duff accumulation makes re-introduction of fire especially challenging when retention of trees is important. Duff can smolder and kill individuals so a burn objective is to consume duff in ways that minimize tree damage. In upland forests, small-scale distribution of duff and associated moisture is heterogeneous making no one set of burn parameters ideal. Better understanding of distribution and condition of duff may facilitate effective re-introduction of fire in many forest ecosystems. This is true in longleaf pine (Pinus palustris) forests where 40-50% of existing stands suffer from some degree of fire exclusion. Consequently there is on-going discussion about the utility of altering ignition pattern to decrease duff smoldering. Objectives are to evaluate patterns in litter/duff biomass and moisture associated with different micro-sit...
Background/Question/Methods Ecological restoration spans a wide range of activities from planting... more Background/Question/Methods Ecological restoration spans a wide range of activities from planting dominant plant species on prepared ground to improving degraded sites that support residual ecological values. No matter where a site falls along that continuum, assessment and establishment of goals to guide restoration activities are important initial steps. Recovery of moderately degraded sites may provide critical habitat for vertebrate species of conservation concern much sooner than areas in need of traditional and extensive restoration. However such sites are not always targeted for restoration, perhaps because it is assumed that they fall within the range of natural variability and/or there is a lack of knowledge to determine what action is needed when a site is close to the desired ecological condition. This may be the case for many second-growth stands of longleaf pine (Pinus palustris), a frequent-fire maintained ecosystem. However there is concern that small differences in h...
Background/Question/Methods It is well understood that frequent prescribed fire is necessary to c... more Background/Question/Methods It is well understood that frequent prescribed fire is necessary to control hardwood encroachment and promote ecological integrity of longleaf pine (Pinus palustris Mill.) forests. However, there has long been concern that this management tool might also lessen growth and overall volume of young pine trees. Results of some short-term studies, including one that applied biennial fires for over a decade, showed a decrease in growth of young longleaf pines on burned plots compared to unburned ones. That information prompted establishment of the current research effort in 1984 to look at effects of fire frequency (2, 3, and 5-year) and season (dormant versus growing season) as well as unburned plots. This long-term study is located near Brewton, AL, on the Escambia Experimental Forest, a privately own facility managed by the U.S. Forest Service. The naturally regenerated longleaf pines were 15 years old and had been frequently burned prior to initiation of th...
Population viability analyses are useful tools to predict abundance and extinction risk for imper... more Population viability analyses are useful tools to predict abundance and extinction risk for imperiled species. In southeastern North America, the federally threatened gopher tortoise (Gopherus polyphemus) is a keystone species in the diverse and imperiled longleaf pine (Pinus palustris) ecosystem, and researchers have suggested that tortoise populations are declining and characterized by high extinction risk. We report results from a 30-year demographic study of gopher tortoises in southern Alabama (1991-2020), where 3 populations have been stable and 3 others have declined. To better understand the demographic vital rates associated with stable and declining tortoise populations, we used a multi-state hierarchical markrecapture model to estimate sex-and stage-specific patterns of demographic vital rates at each population. We then built a predictive population model to project population dynamics and evaluate extinction risk in a population viability context. Population structure did not change significantly in stable populations, but juveniles became less abundant in declining populations over 30 years. Apparent survival varied by age, sex, and site; adults had higher survival than juveniles, but female survival was substantially lower in declining populations than in stable ones. Using simulations, we predicted that stable populations with high female survival would persist over the next 100 years but sites with lower female survival would decline, become male-biased, and be at high risk of extirpation. Stable populations were most sensitive to changes in apparent survival of adult females. Because local populations varied greatly in vital rates, our analysis improves upon previous demographic models for northern populations of gopher tortoises by accounting for population-level variation in demographic patterns and, counter to previous model predictions, suggests that small tortoise populations can persist when habitat is managed effectively.
... Ecology 56: 92-104. ROBERT WILLIAM CRUDEN AND SHARON MARIE HERMANN-PARKER, Department of Bota... more ... Ecology 56: 92-104. ROBERT WILLIAM CRUDEN AND SHARON MARIE HERMANN-PARKER, Department of Botany, Univer-sity of Iowa, Iowa City, Iowa 52242. ... 3, Norwood, Massachusetts, Norwood Press), White (1941, Brit. Birds 34: 179), Williamson (1941, Brit. ...
Although private properties are predicted to play an increasingly significant role in conservatio... more Although private properties are predicted to play an increasingly significant role in conservation, surveys of species of special concern are rare on these lands. We created a template for a multi-county survey of randomly selected sites and sampled for burrows of the gopher tortoise (Gopherus polyphemus) in south-central Georgia, USA. Current land use was strongly correlated with tortoise population condition.
Abstract Much attention has been given to the biology, ecology, and restoration of wiregrass beca... more Abstract Much attention has been given to the biology, ecology, and restoration of wiregrass because of the essential role it plays in the longleaf-slash pine ecosystem of the southeastern United States. A previous morphological study separated wiregrass into two ...
Young longleaf pine (Pinus palustris Mill.) plantations provide an important starting point for r... more Young longleaf pine (Pinus palustris Mill.) plantations provide an important starting point for restoration of longleaf pine ecosystems in the southeastern United States, with management goals often emphasizing restoration of vegetation composition and structure, as well as reestablishment of important ecological processes such as fire. We evaluated the influence of seasonal prescribed fire and overstory density on vegetation structure across overstory, midstory, and understory vegetation strata of a 23-year-old longleaf pine plantation in west-central Georgia. After three prescribed fire cycles through 8 years, we found significantly fewer broad-leaved woody stems in the midstory on both winter-and summer-burned plots compared to unburned plots, as well as fourfold greater herbaceous vegetation cover on burned plots compared to unburned plots. While we predicted that summer burning may be more important in controlling woody plants on low-density overstory plots compared to high-density plots, we found no meaningful interactions between fire seasonality and overstory density. Reductions in litter cover via prescribed fire appeared to be an important mechanism regulating herbaceous vegetation, suggesting that restoration should emphasize management of the forest floor to reduce litter cover and enhance opportunities for herbaceous plant establishment.
Anthropogenic inputs to cultivated sites were evident based on higher base saturation, pH, exchan... more Anthropogenic inputs to cultivated sites were evident based on higher base saturation, pH, exchangeable Ca, Mg, and K, bulk density, and P relative to uncultivated sites. • Soils in uncultivated sites had higher levels of C (biomass C, TOC, and POM C) compared to cultivated sites. • On average, Longleaf was 42% higher in biomass C and 59% higher in TOC than row cropping, and row cropping was 20% higher in bulk density and 33% higher in both TON and POM N relative to Longleaf. • More C and N stratification in Longleaf relative to cultivated sites based on larger stratification ratios of C and N pools.
Background/Question/Methods At Horseshoe Bend National Military Park in Alabama, the National Par... more Background/Question/Methods At Horseshoe Bend National Military Park in Alabama, the National Park Service (NPS) is pursuing ecological restoration. Fire was excluded for 75+ years and past agriculture occurred on a portion of the ~800 ha site. Historical records suggest that uplands were once open-canopied forests dominated by longleaf pine (Pinus palustris). Most longleaf were removed prior to 1930 and fire exclusion resulted in loblolly pine and native hardwoods encroaching from down-slope, moist areas. Ongoing efforts include reintroducing fire, minimizing encroaching hardwood species, and decreasing accumulated duff and litter. There is also a need to plant longleaf pine because the site lacks a sufficient seed source. The NPS hopes to reintroduce longleaf without dramatic, sudden visual changes to the landscape that surrounds a historically significant battleground. Traditional approaches to re-establishing most pine species include mechanical and/or chemical treatments to cle...
Background/Question/Methods Longleaf pine (Pinus palustris) ecosystems once dominated 60-90 milli... more Background/Question/Methods Longleaf pine (Pinus palustris) ecosystems once dominated 60-90 million acres and it is suggested that some remnant stands continue to support one of the most diverse floras in North America. It is well-known that longleaf pine ecosystems must burn frequently to maintain natural structure and function. This vegetation type ranks as one of the most fire-dependent ones in the country and must burn frequently (multiple times a decade) for natural structure and function to be maintained. Frequent fires maintain relatively low fuel loads and so many burns do not directly affect adult longleaf trees. However, other species are immediately affected by each fire that burns through a stand. Because many resident species are perennials that re-sprout after fires, it likely takes multiple burns to change the plant assemblage of the ground layer. There is a need is for better insight into fire effects on small woody stems in the ground layer. How and when fire is app...
Background/Question/Methods The first European settlers in what is now the southeastern United St... more Background/Question/Methods The first European settlers in what is now the southeastern United States were confronted with an upland forest that was dominated by longleaf pine (Pinus palustris Mill.). The pre-historical fire regime, both lightning and Native American-ignition, in the longleaf pine ecosystem was characterized by frequent burning, producing fire of low-moderate intensity. These fires were usually non-lethal to the dominant vegetation and maintained the forest structure of a herbaceous understory with scattered shrubs and an open-canopy. These fire-maintained forest ecosystems were essentially two-layered, consisting of a high canopy dominated by mature longleaf pine and an understory of grasses and herbs. While much is known about the longleaf pine overstory, less is known about the understory which develops under different overstory densities. In the early 1970's, a study was initiated in south Alabama, USA to examine the understory that develops with a dormant, ...
Background/Question/Methods In 2005, Van Lear and others highlighted the ecological significance ... more Background/Question/Methods In 2005, Van Lear and others highlighted the ecological significance of longleaf pine (Pinus palustris) forests for at-risk species dependent on this declining ecosystem. This paper reviewed losses of more than 97 percent acreage prior to 1700, championed restoration efforts for this once-common ecosystem, and called for increased attention to habitat requirements of associated at-risk species. In the current presentation, we explore habitat requirements of sixteen southeastern terrestrial vertebrates categorized as special concern, candidate, threatened, or endangered species. We also estimate ranges of factors in forest structure that are most relevant to some of the species. Results/Conclusions We determine that almost 90 percent of at-risk terrestrial vertebrates in this region share a general habitat requirement for grassland and/or open-canopied forest, during some or all of their lives. Open-canopied species include 4 birds, 2 mammals, 2 amphibians...
Background/Question/Methods Longleaf pine (Pinus palustris Mill.) was the dominant tree and ecosy... more Background/Question/Methods Longleaf pine (Pinus palustris Mill.) was the dominant tree and ecosystem on 20-30 million hectares across the southeastern US at the time of European settlement. Today, longleaf occupies less than 1 million hectares and a majority of these ecosystems are owned by non-industrial private landowners. Numerous efforts are underway to more than double the forested acreage in longleaf pine. This includes the assumption that natural stands will not be lost, which is currently NOT a reality. Naturally-regenerated longleaf pine stands, those quite often in the best ecological shape are lost at the rate of several thousand hectares/year. No efforts or programs exist to help those landowners that have these stands to retain them or to educate landowners about naturally regenerating their planted stands. Quite often, the advice they get is that longleaf is too difficult to manage that way and they clearcut their longleaf pine stand only to plant it back to longleaf....
Background/Question/Methods: In forests dependent on frequent burns, fire exclusion alters struct... more Background/Question/Methods: In forests dependent on frequent burns, fire exclusion alters structure and species composition as well as fuel loads. Duff accumulation makes re-introduction of fire especially challenging when retention of trees is important. Duff can smolder and kill individuals so a burn objective is to consume duff in ways that minimize tree damage. In upland forests, small-scale distribution of duff and associated moisture is heterogeneous making no one set of burn parameters ideal. Better understanding of distribution and condition of duff may facilitate effective re-introduction of fire in many forest ecosystems. This is true in longleaf pine (Pinus palustris) forests where 40-50% of existing stands suffer from some degree of fire exclusion. Consequently there is on-going discussion about the utility of altering ignition pattern to decrease duff smoldering. Objectives are to evaluate patterns in litter/duff biomass and moisture associated with different micro-sit...
Background/Question/Methods Ecological restoration spans a wide range of activities from planting... more Background/Question/Methods Ecological restoration spans a wide range of activities from planting dominant plant species on prepared ground to improving degraded sites that support residual ecological values. No matter where a site falls along that continuum, assessment and establishment of goals to guide restoration activities are important initial steps. Recovery of moderately degraded sites may provide critical habitat for vertebrate species of conservation concern much sooner than areas in need of traditional and extensive restoration. However such sites are not always targeted for restoration, perhaps because it is assumed that they fall within the range of natural variability and/or there is a lack of knowledge to determine what action is needed when a site is close to the desired ecological condition. This may be the case for many second-growth stands of longleaf pine (Pinus palustris), a frequent-fire maintained ecosystem. However there is concern that small differences in h...
Background/Question/Methods It is well understood that frequent prescribed fire is necessary to c... more Background/Question/Methods It is well understood that frequent prescribed fire is necessary to control hardwood encroachment and promote ecological integrity of longleaf pine (Pinus palustris Mill.) forests. However, there has long been concern that this management tool might also lessen growth and overall volume of young pine trees. Results of some short-term studies, including one that applied biennial fires for over a decade, showed a decrease in growth of young longleaf pines on burned plots compared to unburned ones. That information prompted establishment of the current research effort in 1984 to look at effects of fire frequency (2, 3, and 5-year) and season (dormant versus growing season) as well as unburned plots. This long-term study is located near Brewton, AL, on the Escambia Experimental Forest, a privately own facility managed by the U.S. Forest Service. The naturally regenerated longleaf pines were 15 years old and had been frequently burned prior to initiation of th...
Uploads
Papers by Sharon Hermann