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We employed a multi-scale approach to examine the evolving spatial patterns of avian diversity following rewatering (1991–1999) of the Owens River Gorge in eastern California. We based our analysis on three independent data sets representing 18 canyon locations (4 reference and 14 rewatered) consisting of bird counts, measures of landscape variation (canyon dimensions), and vegetation structure and composition (foliage height diversity, total vegetation volume, and plant species diversity). We analyzed our data by grouping sites according to bird diversity and environmental factors using Sørenson's similarity index and cluster analysis and by employing correlation (Spearman rank) and regression (multiple and backward stepwise) procedures to determine the relative importance of environmental factors on avian diversity at different spatial scales. Our results revealed: (1) that valley bottom width determines the extent of riparian vegetation (rs = .73, P < 0.01) and, indirectly, bird species diversity (rs = .52, P < 0.05) at the landscape scale; and (2) that avian diversity at the habitat scale is most strongly correlated with plant species diversity (rs = .57, P < 0.05). These results indicate avian diversity is responding to habitat restoration resulting from the rewatering of the Owens River Gorge but is spatially constrained by canyon dimensions that limit the area of riparian habitat and, indirectly, plant species diversity. We suggest future evaluations of stream restoration and its role on animal communities consider the merits of a multi-scale analysis.
The federally endangered crenulate leadplant, Amorpha herbacea Walter var. crenulata (Rydb.) Isely, is an endemic shrub of the globally imperiled pine rocklands of southern Florida. Crenulate leadplant is near extinction in the wild due to heavy habitat loss, fire suppression, altered hydrology, and invasion by non-native species. This study examined the floral biology and breeding system of the leadplant and factors that may help explain its decline and provide direction for conservation. Protogynous flowers and a high pollen/ovule ratio suggest a reproductive strategy of outcrossing, while a binucleate pollen grain indicates possible gametophytic self-incompatibility. Hand pollinations show that while the leadplant is capable of some self-fertilization, it is significantly more successful in setting fruit when cross-pollinated, and produces a greater percentage of seed when outcrossed. This predominantly self-incompatible species may, therefore, suffer decreased reproductive fitness in its few remnant localities.
Grazing by large herbivores has the potential to facilitate invasion of natural grasslands by non-native plant species. Often, both herbivore identity and plant community type modulate this effect. The objective of this study was to evaluate the impact of grazing on non-native plant species richness and cover in montane grasslands of central Argentina as related to herbivore identity (horse or cattle) and plant community type. The study was conducted in piedmont valleys of the Ventania Mountains. The area is occupied by two major types of plant communities: short-needlegrass and tall-tussock grasslands. Short-needlegrass grasslands occupy poor soils and have higher plant species diversity compared to tall-tussock grasslands which typically grow on rich soils. Part of the study area is devoted to cattle husbandry, part is inhabited by feral horses, and part has been free of grazing by large herbivores for the last 15 years. We compared non-native species richness and cover at three levels of grazing (horse grazing, cattle grazing, grazing exclusion) and two levels of plant community type (short-needlegrass grassland and tall-tussock grassland) at the end of the growing season in 2006 and 2007. Thirty-one nonnative plant species were found growing in the study area. Grazing increased non-native species richness and cover and was highest under horse grazing and in communities on resource-rich soils. Our results are consistent with the hypothesis that grazing by large non-native herbivores can facilitate non-native plant species invasion of natural grasslands. They also suggest that herbivore identity and community type modulate the effect of large herbivore grazing on grassland invasion by non-native plant species.
Montane cloud forests that occur along protected ravines have a fragmented distribution in western Mexico. These forests contain high species richness, and a number of endemic species and relict species. We identify montane cloud forests in western Mexico that deserve priority for conservation and in situ preservation. We rank the montane cloud forests based on tree species richness, the number of endemic vascular plants, the number of species with protection status, and the presence of relict tree species. We place tree species richness and floristic composition of montane cloud forests from western Mexico in a world context, comparing them with 110 forests throughout the world. Then, using Ward's dendrogram, we identify similarities in the floristic composition. Also, we determine which species in the montane cloud forests of western Mexico are protected by the Mexican Species Act, CITES, or IUCN Red List. Our results indicate that the montane cloud forest at Ojo de Agua del Cuervo in the state of Jalisco is unique in that it contains larger numbers of tree species, endemic vascular plants, and endangered plants than similar Asian forests containing ancient species. Ojo de Agua del Cuervo is floristically related at the generic level to forests in Asia, as well as those in Mexico containing Tertiary relict tree species. We propose a 56,395 ha biosphere reserve that includes Ojo de Agua del Cuervo and its surroundings. This proposed reserve would increase the number of preserved montane cloud forests, which are currently underrepresented among Mexican protected natural areas.
Intensive management of jack pine (Pinus banksiana Lamb.) plantations has led to a population increase and breeding range expansion of the endangered Kirtland's Warbler (Dedroica kirtlandii Baird). However, no study has quantified the different bird communities that are associated with Kirtland's Warbler habitat management. We examined bird species conservation scenarios of warbler habitat management by addressing the following: (1) how do bird community structure and conservation scenarios differ among jack pine habitats of three discrete age classes (YOUNG, < 5 years; KW, 5–23 years; and OLD, > 23 years)?; (2) what functional groups (e.g., nest placement groups, foraging groups) of bird species are represented among these three habitat types?; and (3) what are the relationships between bird communities and the composition and structure of these habitat types? Sixty bird species were observed in 37 habitat patches across the three habitat types. Conservation metrics based upon the pooled species lists for each of the habitat types indicated no difference (P > 0.05) among them. Five bird species of U.S. Fish and Wildlife Service Regional Conservation Priority were found among the habitat types, with all but Kirtland's Warbler most common in the YOUNG habitat. Five indicator species associated with the YOUNG and KW habitat types were observed, while nine species were associated with the OLD habitat. A functional group analysis indicated that stand structure was important for breeding species across habitat types. We believe our results support increased ecologically-based planning and management across jack pine habitats for more than just Kirtland's Warbler.
KEYWORDS: avian community changes, bird surveys, Bureau of Land Management, Colorado Plateau, Intermountain West, mechanical fuels reduction, pinyon-juniper woodlands, Utah
Natural area managers in regions of the semi-arid west, particularly on the Colorado Plateau, are presently dealing with expanding pinyon (Pinus spp. Engelm.) — juniper (Juniperus spp. Engelm.) woodlands on rangelands. Increased equipment costs associated with ‘chaining’, and dangers associated with prescribed fires, have resulted in more instances where mechanical thinning of woodlands is being used. Our 2005 to 2006 study within Grand Staircase Escalante National Monument, Utah, examined responses of breeding birds to the mechanical reduction of pinyon-juniper woodlands within a randomized 4-block design that incorporated 11 control and nine treatment bird count stations. We surveyed birds within 3.1-ha bird-count stations (n = 20) prior to, and following, pinyon-juniper mechanical reduction treatments. Thinning in April 2006 removed a mean of 92% ( 6.4% SE) of live trees from treatment blocks. The avian guild most greatly influenced by mechanical thinning included pinyon-juniper obligate species. Species eliminated following mechanical thinning were Gray Vireo (Vireo vicinior) and Brown-headed Cowbird (Molothrus ater), while Chipping Sparrow (Spizella passerine) numbers were significantly reduced. Birds in the shrub-nesting guild, including the sagebrush specialist Brewer's Sparrow (Spizella breweri), and habitat generalists such as the Bushtit (Psaltriparius minimus), increased in relative abundance following treatment. We conclude that mechanical thinning within the Intermountain West has the potential for natural area managers to design treatments that can influence numbers of both pinyon-juniper and sagebrush (Artemisia tridentata Nutt.) steppe avian species.
Thirty natural populations of American ginseng (Panax quinquefolius L.) were censused twice annually for five to 11 years to monitor the rate, frequency, and intensity of root harvest. Over this period, 43% of populations were harvested and ca.10% of plants was removed by harvesters. On an annual basis, 15% of populations were harvested and 1.3% of individuals were confirmed harvested. Both rates are likely underestimates of actual rates since we used conservative criteria to recognize harvest. Nearly half of the harvested populations were harvested more than once. Harvesters removed a small proportion of plants from populations; however, they frequently took non-reproductive and small plants, making the effect of harvest more destructive. In addition, violations of regulations regarding season, location, and plant size were common (20%, 65%, and 82% of events, respectively). Only 6% of harvest events were legal and 1.4% of plants were legally harvested in all three respects at the study sites. Two illegal harvests were documented carefully because they occurred at or near census points. These harvests highlighted the proximal factors that result in unsustainable harvest practices: (1) removal of adult plants prior to ripening of seeds, thus precluding the proper planting of propagules for population recovery; (2) removal of plants that are under the legal size limit, with no ability of dealers or buyers to detect this violation; and (3) removal of plants from land in which harvest is strictly prohibited, and the associated difficulty of enforcing such rules. We discuss policy options that could contribute to addressing these problems.
The Mountain Longleaf National Wildlife Refuge (MLNWR), located in northeastern Alabama, is unique in that it holds significant acreages of young and old-growth montane longleaf pine forest (Pinus palustris Mill.). We conducted a study to aid in the management and restoration of longleaf pine communities on the MLNWR. Our objectives were to: (1) establish permanent forest monitoring plots; (2) document herbaceous and woody vegetation; and (3) measure forest diversity, structure, and fuel loads in montane longleaf pine communities with varying fire and management histories. We established 48 plots, 0.04 ha in area, in winter 2008 and measured all plots in summer 2008. The MLNWR has recently incorporated prescribed burning in their management plans and each plot was categorized by the year it was burned (2008, 2006, 2004, no-burn) and whether hardwood control treatments were applied. We identified 18, 19, and 22 different woody plant species in the overstory, mid-story, and understory, respectively, across plots. Longleaf pine basal area ranged from 5 to 10 m2 ha-1 and represented as much as 80% of basal area across plots. Mid-story basal area and woody plant species diversity were lower in plots receiving fire or hardwood control. Longleaf pine regeneration was found in only 17 plots and was highest in burned plots or plots receiving hardwood control. Burning also increased grass and herbaceous ground cover. Fuel loads were high with an average humus layer accumulation of 35 Mg ha-1. Regular fire intervals are needed to reduce fuels and mid-story density and aid in the regeneration of longleaf pine.
If fire affects spread of cogongrass (Imperata cylindrica), a non-native grass that displaces native plants, managers can determine best use of resources to restore and maintain the diverse herbaceous groundcovers of longleaf pine-bluestem (Pinus palustris - Andropogon spp. and Schizachyrium spp.) forests of the southeastern United States. In 2003 and 2004, we measured rates of vegetative encroachment of cogongrass into burned and unburned pine-bluestem and pine-shrub forests one and two years post-burning on Camp Shelby Training Site, Mississippi. Linear growth and tiller production were significantly greater in pine-bluestem forests compared to pine-shrub forests for both time periods. Cogongrass growth was not affected by burning in either forest type one-year post-burning, but was significantly greater in burned forests after two years of growth. Two-years post-burning, mean linear growth of cogongrass was 235 cm in burned pine-bluestem, 139 cm in unburned pine-bluestem, 177 cm in burned pine-shrub, and 92 cm in unburned pine- shrub. Tiller production/m2 for 2004 was greatest in pine-bluestem burned plots and least in pine-shrub unburned plots. Linear growth of cogongrass was significantly and positively correlated to percent cover of adjacent herbaceous vegetation but tiller numbers were significantly and negatively correlated to percent cover of adjacent shrubs. Efforts to restore pine-shrub forests to pine-bluestem forest conditions should implement control of cogongrass before and after use of Are. Vigilant control efforts are needed as restoration shifts conditions to those of pine-bluestem forests and increases susceptibility to cogongrass invasion.
The Natural Areas Training Academy (NATA) has been in operation in Florida since June of 2000. The program was founded and managed by The Nature Conservancy in partnership with the University of Florida. NATA offers the Certificate in Natural Areas Management as a continuing education experience. Land management professionals earn this certificate following completion of a series of five workshops that cover the basic skills of natural areas management. NATA works with experienced professionals from a variety of agencies who serve as faculty; an advisory committee provides guidance to ensure that workshops are timely and relevant. NATA offers training that is specifically designed for professionals who manage natural areas. It assists these professionals to define what they do on a daily basis and adds to the traditional training that most have had in one or more biological sciences. Natural areas management is a profession that lacks a well accepted, codified set of skills. NATA offers a sequence of training opportunities that provides its participants with a clear sense of the skill set needed to be a successful manager of conservation lands.
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