P. Charles Goebel

USING LANDSCAPE HIERARCHIES TO GUIDE RESTORATION OF DISTURBED ECOSYSTEMS

Reestablishing native plant communities is an important focus of ecosystem restoration. In complex landscapes containing a diversity of ecosystem types, restoration requires a set of reference vegetation conditions for the ecosystems of concern, and a predictive model to relate plant community composition to physical variables. Restoration also requires an approach for prioritizing efforts, to facilitate allocation of limited institutional resources. Hierarchy theory provides a conceptual approach for predicting plant communities of disturbed ecosystems and, ultimately, for prioritizing restoration efforts. We demonstrate this approach using a landscape in southwestern Georgia, USA. Specifically, we used an existing hierarchical ecosystem classification, based on geomorphology, soil, and vegetation, to identify reference plant communities for each type of ecosystem in the landscape. We demonstrate that ecosystem identity is highly predictable using: only geomorphic and soil variables, because these upper hierarchical levels control the development of vegetation, a lower hierarchical level. We mapped the potential distribution of reference ecosystems in the landscape and used GIS (geographic information systems) to determine relative abundance of each ecosystem, as a measure of its historical rarity. We joined the reference ecosystem map with a current cover map to determine current abundance of each reference ecosystem, and percentage conversion to different disturbance classes. We show that over half of the landscape supports something other than reference plant communities, but degree of rarity varies widely among ecosystems. Finally, we present an index that integrates information on historical and current rarity of ecosystems, and disturbance levels of individual polygons, to prioritize restoration efforts. The premise of the index is that highest priority be given to restoring (1) currently rare ecosystems that were also historically rare and (2) the least disturbed examples of these ecosystems, as these will require the least effort to restore. We found that 80% of high-priority sites occur within just three (of 21) ecosystems. Moreover, the high-priority ecosystems all occur within stream valleys. Our approach provides managers with a straightforward methodology for determining potential distribution of reference ecosystems and for allocating efforts and resources for restoration in complex landscapes. Development of a priority index for a specific landscape requires an understanding of the hierarchical relationships among geomorphology, soil characteristics, and plant communities, in addition to well-defined restoration objectives.

Development of mixed-oak forests in southeastern Ohio: a comparison of second-growth and old-growth forests

Abstract Traditionally, studies of forest development have independently focused on the compositional and structural differences of second-growth and old-growth forests. However, few studies have attempted to use current old-growth forest ecosystems as a benchmark with which to compare the composition, structure, and dynamics of a surrounding matrix of sequentially aged second-growth forests. In order to examine the development of mixed-oak forests we compared the composition, structure, and stand dynamics of seventeen relatively undisturbed second-growth forests (70–149 years old) with four old-growth forests (at least 150 years old) on south-facing ecological landtypes (ELTs) in southeastern Ohio. All living and dead trees over 10.0 cm dbh and coarse woody debris over 10.0 cm mid-diameter were inventoried on 500-m 2 plots. Saplings and seedlings were sampled on nested 100-m 2 and 2-m 2 subplots, respectively. Principal components analysis (PCA) was used to support the assumption that study sites had similar soils and physiography. Overstory species richness was greatest in the younger second-growth stands, and significantly differed among age classes. Five species of oaks ( Quercus spp.) dominated the overstories of all stands. However, white oak ( Quercus alba L.) canopy importance value (IV) ((relative dominance + relative density)/2) significantly differed among stands; it ranged from 35.5% in stands 70–89 years old to 86.1% in stands 130–149 years old, while it comprised 46.5% of the old-growth canopies. Pignut hickory ( Carya glabra (Mill.) Sweet.) canopy IV tended to be less in the second-growth than in the old-growth stands. Whereas oaks dominated the overstories of the second-growth and old-growth stands, they were almost absent from the sapling layer of all stands (less than 5% of the total densities). The sapling layers of all age classes were comprised of shade-tolerant species. For example, American beech ( Fagus grandifolia Ehrh.) sapling relative density significantly differed between the 70–89 year old stands (6.3%) and the stands at least 150 years old (23.9%). Even though densities of oak saplings were low, the relative densities of oak seedlings were much greater, suggesting adequate oak advance regeneration. Few significant differences in stand structure (e.g. basal area, density, mean diameter, canopy closure) or standing and fallen coarse woody debris were detected between the second-growth and old-growth forests. Detrended correspondence analyses (DCA) appeared to represent a gradient of increasing white oak IV with age. Although indices of old-growth attributes have proven successful in discriminating between second-growth and old-growth ecosystems in other regions of North America, our results suggest that such an index would not work well in mixed-oak forests. Canopies dominated by a mixture of oaks, in conjunction with a majority of canopy individuals at least 150 years old, may be the best indicators of old-growth conditions on south-facing landtypes in southeastern Ohio.

DEPRESSIONAL WETLAND VEGETATION TYPES: A QUESTION OF PLANT COMMUNITY DEVELOPMENT

When wetland restoration includes re-establishing native plant taxa as an objective, an understanding of the variables driving the development of plant communities is necessary. With this in mind, we examined soil and physiographic characterstics of depressional wetlands of three vegetation types (cypressgum swamps, cypress savannas, and grass-sedge marshes) located in a fire-maintained longleaf pine ecosystem in southwestern Georgia, USA. Our objective was to establish wether plant community development in these wetlands is controlled primarily by hydrogeomorphic features or by different disturbance histories. We did not identify physical features that uniquely separate the wetland vegetation types. Instead, we observed a range of topo-edaphic conditions that likely drive variations in hydrologic regimes, which in turn, are probable influences on fire regime. We propose that several long-term successional trajectories may be initiated in the prolonged absence of fire, altered hydrology, or both, which link the distinctive vegetation types. Thus, a range of vegetation types may be suitable as potential restoration goals for these depressional wetlands. We suggest that the opportunities or constraints for use of prescribed fire in the long-term management of restored wetlands and adjacent uplands should be a significant consideration in the development of restoration strategies targeting specific plant communities.

Predicting plant species diversity in a longleaf pine landscape

Abstract: In this study, we used a hierarchical, multifactor ecological classification system to examine how spatial patterns of biodiversity develop in one of the most species-rich ecosystems in North America, the fire-maintained longleaf pine-wiregrass ecosystem and associated depressional wetlands and riparian forests. Our goal was to determine which landscape features are important controls on species richness, to establish how these constraints are expressed at different levels of organization, and to identify hotspots of biological diversity for a particular locality. We examine the following questions: 1) How is the variance in patterns of plant species richness and diversity partitioned at different scales, or classification units, of the hierarchical ecosystem classification developed for the study area? 2) What are the compositional similarities among ecosystem types? 3) For our study area, what are the sites expected to harbour highest species richness? We used a spatially explicit map of biodiversity to project abundance of species-rich communities in the landscape based on a previously developed ecological classification system for a lower Gulf Coastal Plain landscape. The data indicate that high species richness in this ecosystem was found in sites with frequent fire and high soil moisture. Sites in fire-maintained landscapes with lower frequency of fire were associated with geomorphological characteristics, suggesting a dependence of the diversity-disturbance relationship with soil type. With more frequent fire on some sites, high diversity shifts from canopy component to ground flora, with an overall increase in total species richness. Our approach demonstrates how potential species richness can be identified as a restoration goal and that multiple vegetation endpoints may be appropriate vegetation objectives. We identify basic management needs for the maintenance of biodiversity in this ecosystem that can be derived from an understanding of the combination of factors that most strongly predict diverse plant communities.

FOREST ECOSYSTEMS OF A LOWER GULF COASTAL PLAIN LANDSCAPE: MULTIFACTOR CLASSIFICATION AND ANALYSIS

The most common forestland classification techniques applied in the southeastern United States are vegetation-based. While not completely ignored, the application of multifactor, hierarchical ecosystem classifications are limited despite their widespread use in other regions of the eastern United States. We present one of the few truly integrated ecosystem classifications for the southeastern Coastal Plain. Our approach is iterative, including reconnaissance, plot sampling, and multivariate analysis. Each ecosystem is distinguished by differences in physiographic setting, landform, topographic relief, soils, and vegetation. The ecosystem classification is ground-based, incorporating easily observed and measured factors of landform, soil texture, and vegetative cover associated into ecological species groups identified by two-way indicator species analysis. Canonical conrespondence analyses (CCA) that measure the degree of distinctness among ecosystems using different combinations of physiographic, soil, and vegetation datasets are used to verify the classification. The hierarchical ecosystem classification provides a framework for sustainable resource management of our study landscape as an alternative to traditional cover-type or vegetation-based classifications in the southeastern Coastal Plain. This ecosystem classification provides a structural framework that mimics biological organization, by physical drivers, ensuring that information on various ecosystem components are available to assist management decisions made at the ecosystem level.

Pre- and post-European settlement fire history of red pine dominated forest ecosystems of Seney National Wildlife Refuge, Upper Michigan

To understand the dynamics of fire in red pine (Pinus resinosa Ait.) forest ecosystems that once dominated areas of the northern Lake States, we dendrochronologically reconstructed the fire regime prior to European settlement (pre-1860), after European settlement (1860-1935), and postrefuge establishment (post-1935) for different portions (wilder- ness and nonwilderness) and landforms (sand ridges and outwash channels) of the Seney National Wildlife Refuge (SNWR) in eastern Upper Michigan. Using data from 50 sites, we found that the cumulative number of fires showed a slow rate of accumulation from the 1700s to 1859, a steeper pattern suggesting higher fire occurrence from 1860 to 1935, and a return to fewer fires after 1935. Prior to European settlement, the fire cycle (FC) of sand ridge landforms inter- spersed within a poorly drained lacustrine plain in the Seney Wilderness Area was 91-144 years. This was longer than on glacial outwash channel landforms (53 years) and on sand ridge landforms interspersed within lacustrine plains located outside of the wilderness (47 years). The FC was also shorter (30 years) during this period and has subsequently increased (149-1090 years) after SNWR establishment. Differences in fire regimes among landform types were minor relative to the temporal variation in fire regimes among the three time periods.

PLANT DIVERSITY CONTRIBUTIONS OF RIPARIAN AREAS IN WATERSHEDS OF THE NORTHERN LAKE STATES, USA

In most forested watersheds, riparian areas constitute a small proportion of the total land area, yet their contributions to overall plant diversity can be significant. However, little information is available on which portion of riparian areas (defined as functional ecotones comprising all fluvial landforms, including floodplains, terraces, and connecting hillslopes) contribute the most to plant species richness and at what scale these contributions are most evident. In order to better understand the contributions riparian areas provide to plant species richness in forested watersheds, we examined herbaceous ground-flora richness and similarity from 56 reaches in eight different valley types (defined as unique combinations of stream order, surficial geology, and stream-valley constraint) across the northern Lake States, USA. We analyzed these data at two scales: (1) at the individual reach scale; and (2) at the watershed scale by pooling individual reaches by valley type. At the reach scale and regardless of valley type, there is not significant (

Changes in the composition and structure of mixed-oak, second-growth forest ecosystems during the understory reinitiation stage of stand development

Abstract:The composition and structure of the living and dead woody vegetation in seventeen relatively undisturbed, second-growth forests in the understory reinitiation stage of stand development (70 to 149 years old) were examined using a chronosequence on a single south-facing ecological landtype phase in southeastern Ohio. Principal components analysis (PCA), in conjunction with historical information, was used to support the assumption that plots had similar physiography, soils, and disturbance histories. The first axes of canonical correspondence analyses (CCA) based on canopy species importance values, as well as sapling and seedling relative densities, represented a successional continuum of increasing Quercus alba L. Canonical correspondence analysis (CCA) relating canopy composition with the density of dead snags and fallen logs suggested that during understory reinitiation there may be several species-specific waves of density-independent mortality, such as scarlet oak (Q. coccinea Muenchh.) dec...

Geomorphic variation in riparian tree mortality and stream coarse woody debris recruitment from record flooding in a coastal plain stream

Large floods are an important process controlling the structure and function of stream ecosystems. One of the ways floods affect streams is through the recruitment of coarse woody debris from stream-side forests. Stream valley geomorphology may mediate this interaction by altering flood velocity, depth, and duration. Little research has examined how floods and geomorphic features interact to control debris recruitment from riparian forests. With this in mind, we examined debris recruitment resulting from tree mortality during a record flood in a Georgia (U.S.A.) stream. We quantified debris characteristics as related to riparian geomorphology, and we examined the influence of floods on the structure of stream-side forests. The flood killed, and recruited into the stream debris pool, an average of 22 trees/km. Variation in recruitment was related to geomorphology; mortality was highest in reaches having narrow valleys and high elevations of riparian landforms, while it was lowest in reaches having wide valleys and low landform elevations. Species differed in probability of mortality; three taxa, out of 47, contributed 75% of new debris to the stream. The structure of stream-side forests reflected the influence of floods on tree mortality; forests along constrained reaches lack small individuals. Our results suggest that constrained reaches are the primary sources of debris during large floods, while unconstrained reaches function as debris sinks. Debris characteristics may be linked to floods through tree demography. Specifically, large floods have the potential to limit future recruitment of larger-sized susceptible species into the stream, by limiting the number of small trees that grow into the canopy.

Failure to Phytosanitize Ash Firewood Infested with Emerald Ash Borer in a Small Dry Kiln Using ISPM-15 Standards

ABSTRACT Although current USDA-APHIS standards suggest that a core temperature of 71.1°C (160°F) for 75 min is needed to adequately sanitize emerald ash borer, Agrilus planipennis Fairmaireinfested firewood, it is unclear whether more moderate (and economical) treatment regimes will adequately eradicate emerald ash borer larvae and prepupae from ash firewood. We constructed a small dry kiln in an effort to emulate the type of technology a small- to medium-sized firewood producer might use to examine whether treatments with lower temperature and time regimes successfully eliminate emerald ash borer from both spilt and roundwood firewood. Using white ash (Fraxinus americana L.) firewood collected from a stand with a heavy infestation of emerald ash borer in Delaware, OH, we treated the firewood using the following temperature and time regime: 46°C (114.8°F) for 30 min, 46°C (114.8°F) for 60 min, 56°C (132.8°F) for 30 min, and 56°C (132.8°F) for 60 min, Temperatures were recorded for the outer 2.54-cm (1-in.) of firewood. After treatment, all firewood was placed under mesh netting and emerald ash borer were allowed to develop and emerge under natural conditions. No treatments seemed to be successful at eliminating emerald ash borer larvae and perpupae as all treatments (including two nontreated controls) experienced some emerald ash borer emergence. However, the 56°C (132.8 F) treatments did result in considerably less emerald ash borer emergence than the 46°C (114.8°F) treatments. Further investigation is needed to determine whether longer exposure to the higher temperature (56°C) will successfully sanitize emerald ash borer-infested firewood.