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Since European settlement, changes in the fire regime of eastern deciduous forests of North America have led to changes in biological diversity and stand structure. These changes may be attenuated in xeric forests at the western limit of the eastern deciduous forest where woody plant species richness is low, and dominance high, due to the rigorous biotic and physical environment. Effects of fire frequency on woody plant species richness and stand structure were studied in a xeric, oak-dominated (Quereus spp.) old-growth forest in eastern Oklahoma where prescribed burning had been conducted over 20 years at frequencies ranging from zero to five fires per decade. Regeneration (stem height < 1.4 m) cover was not affected by fire frequency. Increasing fire frequency had a strong negative effect on species richness of saplings and shrubs (stem dbh < 5 cm) but no significant effect on small tree (stems 5 cm < dbh < 10 cm) and large tree (stems dbh > 10 cm) species richness. While oak sapling density was not affected by fire frequency, the density of non-oak saplings and shrubs was very high at zero and one fire per decade and strongly reduced by fire frequencies of two or more per decade. Although 20 years of treatment may not have been sufficient to show fire frequency effects on canopy trees, the effect on species composition of saplings was strong and may have long-term consequences for forest canopy composition. These results suggest that, without at least two fires per decade, tree species richness of these forests will increase and oak dominance will diminish.
Socio-economically important plant species that are used in wetland restoration projects can act as economic incentives for conservation and restoration. We examined the suitability of a medicinal plant, Acorus calamus L. (sweetflag, Acoraceae), for use in wetland restoration. We subjected rhizomes of A. calamus to different levels of light (full light and shade), moisture (400 ml and 200 ml water biweekly), and nitrogen (10 µg ml-1 and 4 µg ml-1 nitrogen biweekly) in a greenhouse study mimicking different stages of wetland restoration. At the end of the experiment, the biomass and length of each rhizome, and number of mature buds, leaves, and roots, were recorded. Multivariate analysis of variance indicated that light (λ = 0.762), nitrogen (λ = 0.449), and moisture (λ = 0.508) had significant effects on rhizome growth. Our results indicate that A. calamus displays a high degree of morphological plasticity in biomass allocation patterns in response to environmental parameters. Furthermore, most of its biomass is sequestered in roots and rhizomes, which are economically important. The rhizome of A. calamus can persist in nitrogen-limited soil though it fares better in soils with greater nitrogen content. It is also adapted to grow in both light and moderate shade and can grow in both flooded and drawdown areas. These characteristics make A. calamus suitable for planting at both the beginning and later stages of wetland restoration. Acorus calamus can be harvested as a low input crop from both nitrogen-poor and nitrogen-rich wetlands to help local communities benefit from wetland restoration.
Wiregrass (Aristida stricta Michx.) is a keystone species in fire dependent pine ecosystems throughout the southeastern United States and is often re-introduced into sites via broadcast seeding. Using seed lots of high quality may enhance these restoration efforts. However, parameters that determine seed lot quality, such as viability, have not been studied in detail. Moreover, methods for determining wiregrass seed viability have not been reported. Here we describe a new method for determining wiregrass seed viability using forceps and a microscope. This method is relatively rapid, requires no specialized training in seed biology or chemical viability assay analysis, and is as accurate and precise as chemical viability assay methods. The new forceps press test approach can be exploited by wiregrass propagators and practitioners to gain a better understanding of seed lot quality that may augment their restoration efforts.
Golf course conservation easements represent a controversial type of protected area which may qualify for federal and some state tax reduction incentives under certain conditions defined by the Internal Revenue Service Tax Code and respective state departments of revenue. Tax benefits are often the primary motivation for a landowner to terminate certain rights on a property through deed restrictions under a permanent conservation easement. One easement category within the Internal Revenue Service Tax Code requires protection of one or more natural habitats; however, few golf courses offered for conservation by this criterion actually possess meaningful environmental or biodiversity values, nor serve a real public interest. A general evaluation methodology is presented for objective consideration of such golf course conservation easements to ensure that only qualified sites are accepted. Not only is there a basic responsibility to comply with the intent of the tax code, but natural habitat quality must be maintained.
Because old trees contain centuries of environmental history, investigators are increasingly turning to dendrochronology to create context for current environmental change. While a suite of characteristics to identify old trees has been developed, most of these characteristics are for conifers or trees growing in low-density forests. Given that the diverse Eastern Deciduous Forest (EDF) is dominated by a species-rich, angiosperm-dominated woody flora, old-growth forests are scarce in the EDF, and research permits in natural areas often limit the number of trees that can be sampled, having a suite of characteristics that identify old trees for a wider range of species increases the likelihood of efficiently creating longer depths of ecological history. The common indicators of old (> 250 year old) EDF angiosperms are presented to aid in the recovery and preservation of these living sources of information. Six common external characteristics of old angiosperm trees include: (1) smooth or “balding” bark; (2) low stem taper; (3) high stem sinuosity; (4) crowns comprised of few, large-diameter, twisting limbs; (5) low crown volume; and (6) a low ratio of leaf area to trunk volume. The existence of old trees in the landscape can also be related to life-history traits or land-use histories. Both professionals and lay folk can be trained to identify these traits and environmental conditions. While these characteristics and settings generally signal the potential for old trees, there is no guarantee that they represent old ages. However, these characteristics should aid in the discovery of old trees throughout the EDF.
Non-native plant invasions can lead to staggering ecological and economic costs. Thus, land managers are concerned about vectors of seed and propagule introduction onto public lands. Because horses are one of several potential vectors of non-native seed dispersal, we summarize and interpret existing literature and identify potential impacts of horse use on non-native plant spread in natural areas. Several studies indicate non-native seeds can germinate after digestion by horses. In addition to their ability to carry viable non-native seeds in their feces, the literature indicates horses can trample native vegetation, cause soil disturbance, and increase soil nitrogen availability in some habitats. The combination of disturbance, which is known to increase invasibility, and introduction of seeds in horse feces could promote non-native plant invasions in wildlands. However, in situ studies have not demonstrated direct causal links between horses and plant invasions. More research is required to determine where, and to what extent, establishment and spread of non-natives occurs in situ as a direct result of disturbances and seed introduction by horses. Guidelines or regulations regarding horse use already exist in some recreational areas. Where none exist, we recommend development of best management practices, such as weed education programs for equestrians, use of Certified Weed Free Feed, and placement of manure bunkers at horse camps and trailheads.
Sphagnum bogs, in the southern Appalachian Mountains of eastern North America are rare and diverse ecosystems; the unique climate range they occupy allows for a mixture of northern and southern species to thrive, creating isolated biodiversity hotspots. Research on northern bogs in Europe and North America has found that climate change and atmospheric nitrogen deposition can shift species composition of bog communities and release carbon; however, research on southern bogs has not begun to answer questions about their fate. We reviewed research conducted in northern bogs and applied this information to southern Appalachian bogs to explore the potential impacts that climate change may have on southern Sphagnum bogs. The projected increase in evapotranspiration coupled with nitrogen deposition may lead to the drying up of southern bogs causing: (1) increased decomposition rates, which can lead to the system becoming a carbon source rather than a sink; and (2) local extinction of many bog species, allowing alternative ecosystems to replace the bogs. Because of these threats, we suggest a call to action for scientists and managers to begin investigating the specific impacts that climate change will have on bogs in the southeastern United States so we may better protect and conserve these unique and diverse habitats.