Fire Management,Managed Relocation,and Land Conservation Options for Long‐Lived Obligate Seeding Plants under Global Changes in Climate,Urbanization, and Fire Regime

Most species face multiple anthropogenic disruptions. Few studies have quantified the cumulative influence of multiple threats on species of conservation concern, and far fewer have quantified the potential relative value of multiple conservation interventions in light of these threats. We linked spatial distribution and population viability models to explore conservation interventions under projected climate change, urbanization, and changes in fire regime on a long‐lived obligate seeding plant species sensitive to high fire frequencies, a dominant plant functional type in many fire‐prone ecosystems, including the biodiversity hotspots of Mediterranean‐type ecosystems. First, we investigated the relative risk of population decline for plant populations in landscapes with and without land protection under an existing habitat conservation plan. Second, we modeled the effectiveness of relocating both seedlings and seeds from a large patch with predicted declines in habitat area to 2 unoccupied recipient patches with increasing habitat area under 2 projected climate change scenarios. Finally, we modeled 8 fire return intervals (FRIs) approximating the outcomes of different management strategies that effectively control fire frequency. Invariably, long‐lived obligate seeding populations remained viable only when FRIs were maintained at or above a minimum level. Land conservation and seedling relocation efforts lessened the impact of climate change and land‐use change on obligate seeding populations to differing degrees depending on the climate change scenario, but neither of these efforts was as generally effective as frequent translocation of seeds. While none of the modeled strategies fully compensated for the effects of land‐use and climate change, an integrative approach managing multiple threats may diminish population declines for species in complex landscapes. Conservation plans designed to mitigate the impacts of a single threat are likely to fail if additional threats are ignored. Manejo de Incendios, Reubicación Administrada y Opciones de Conservación de Suelo para Plantas de Vida Larga con Sembrado Obligado bajo los Cambios Globales en el Clima, la Urbanización y el Régimen de Incendios     

Reproductive Success in Reestablished versus Natural Populations of a Threatened Grassland Daisy (Rutidosis leptorrhynchoides)

Abstract: Populations of the endangered Rutidosis leptorrhynchoides (Asteraceae) have been reestablished in conservation reserves to reduce their risk of extinction in the wild. The reproductive success (number of seeds per inflorescence, percent seed set, germinability) of five small reestablished populations (at 5–10 years after establishment) was compared to that of two large natural remnant populations from which they were derived. Initial growth rates under glasshouse conditions were compared for seedlings derived from seed from remnant and reestablished populations. Seed set per inflorescence in all five reestablished populations was equal to or greater than seed set in remnant population plants. The resulting seed was as germinable, and in some cases more germinable, than seed derived from remnant populations; the seedlings then grew as large or larger than remnant population seedlings grown under glasshouse conditions. Fitness reductions in small reestablished populations of R. leptorrhynchoides are not evident at the reproductive stage. Hence, these populations have some potential to maintain natural regeneration processes and might therefore positively contribute to the conservation of this species.     

Effect of Vertebrate Grazing on Plant and Insect Community Structure

Abstract: We compared species diversity of plants and insects among grazed and ungrazed areas of Ponderosa pine–grassland communities in Arizona. Plant species richness was higher in two of three grassland communities that were grazed by native elk and deer and domestic cattle than in ungrazed areas inside a series of three large (approximately 40-ha) grazing exclosures. Similarly, plant species richness was higher in grazed areas relative to ungrazed areas at one of two series of smaller (approximately 25-m²) and short-term exclosure sites. Evenness of plant distribution, however, was greater inside ungrazed long-term exclosures but was reduced inside ungrazed short-term exclosures relative to grazed areas. Relative abundances of forbs, grasses, trees, and shrubs, and native and introduced plants did not differ between the long- and short-term grazing exclosures and their grazed counterparts. Relative abundances of some plant species changed when grazers were excluded, however. In contrast, insect species richness was not different between grazed and ungrazed habitats, although insect abundance increased 4- to 10-fold in ungrazed vegetation. Our results suggest that vertebrate grazing may increase plant richness, even in nutrient-poor, semi-arid grasslands, but may decrease insect abundances.     

Conservation or Commercial Management of Temperate Forests of Baja California Sur, Mexico

The current status of the oak and oak-pine forests in the Sierra de La Laguna range of the Baja California peninsula is examined from four perspectives: (1) the structural analysis of the woodlands; (2) the natural regeneration of hurricane windfall clearings and its effect on the oak-pine community; (3) the density, mortality, size, and commercial potential of the only pine species Pinus lagunae; and (4) the possible destruction of this endemic species by attack from moths. These factors were evaluated to make recommendations regarding the management and/or commercialization of the forest resources of this proposed Biosphere Reserve. Results show that the oak woodlands occurring at low elevations contain many tropical plants from the tropical dry forest that surrounds these woodlands, and that the tropical elements decrease at higher altitudes. In forest gaps, oaks were more abundant than pines. Gaps contained a lower diversity of perennial plants than mature oak-pine forest. P. lagunae has a high adult mortality, which can be attributed to the joint effect of fire and insect attack. Results indicate that the forest in this region does not have timber-yielding potential because of the small area it covers and because of the low tree diameters and volume, which are insufficient to carry out a continuous and income-producing extraction of the pine resource of Baja California Sur. Finally, options for management are discussed and future studies are proposed to determine the life cycle and extent of the moth populations.     

Effects of past and present livestock grazing on herpetofauna in a landscape‐scale experiment

Livestock grazing is the most widespread land use on Earth and can have negative effects on biodiversity. Yet, many of the mechanisms by which grazing leads to changes in biodiversity remain unresolved. One reason is that conventional grazing studies often target broad treatments rather than specific parameters of grazing (e.g., intensity, duration, and frequency) or fail to account for historical grazing effects. We conducted a landscape‐scale replicated grazing experiment (15,000 km², 97 sites) to examine the impact of past grazing management and current grazing regimes (intensity, duration, and frequency) on a community of ground‐dwelling herpetofauna (39 species). We analyzed community variables (species richness and composition) for all species and built multiseason patch‐occupancy models to predict local colonization and extinction for the 7 most abundant species. Past grazing practices did not influence community richness but did affect community composition and patch colonization and extinction for 4 of 7 species. Present grazing parameters did not influence community richness or composition, but 6 of the 7 target species were affected by at least one grazing parameter. Grazing frequency had the most consistent influence, positively affecting 3 of 7 species (increased colonization or decreased extinction). Past grazing practice affected community composition and population dynamics in some species in different ways, which suggests that conservation planners should examine the different grazing histories of an area. Species responded differently to specific current grazing practices; thus, incentive programs that apply a diversity of approaches rather than focusing on a change such as reduced grazing intensity should be considered. Based on our findings, we suggest that determining fine‐scale grazing attributes is essential for advancing grazing as a conservation strategy.     

Ecological‐Niche Modeling and Prioritization of Conservation‐Area Networks for Mexican Herpetofauna

Abstract: One of the most important tools in conservation biology is information on the geographic distribution of species and the variables determining those patterns. We used maximum‐entropy niche modeling to run distribution models for 222 amphibian and 371 reptile species (49% endemics and 27% threatened) for which we had 34,619 single geographic records. The planning region is in southeastern Mexico, is 20% of the country's area, includes 80% of the country's herpetofauna, and lacks an adequate protected‐area system. We used probabilistic data to build distribution models of herpetofauna for use in prioritizing conservation areas for three target groups (all species and threatened and endemic species). The accuracy of species‐distribution models was better for endemic and threatened species than it was for all species. Forty‐seven percent of the region has been deforested and additional conservation areas with 13.7% to 88.6% more native vegetation (76% to 96% of the areas are outside the current protected‐area system) are needed. There was overlap in 26 of the main selected areas in the conservation‐area network prioritized to preserve the target groups, and for all three target groups the proportion of vegetation types needed for their conservation was constant: 30% pine and oak forests, 22% tropical evergreen forest, 17% low deciduous forest, and 8% montane cloud forests. The fact that different groups of species require the same proportion of habitat types suggests that the pine and oak forests support the highest proportion of endemic and threatened species and should therefore be given priority over other types of vegetation for inclusion in the protected areas of southeastern Mexico.     

Global Warming, Human Population Pressure, and Viability of the World's Smallest Butterfly

Abstract:  The effects of climate change and habitat destruction and their interaction are likely to be the greatest challenge to animal and plant conservation in the twenty-first century. We used the world's smallest butterfly, the Sinai baton blue ( Pseudophilotes sinaicus ), as an exemplar of how global warming and human population pressures may act together to cause species extinctions. We mapped the entire global range of this butterfly and obtained extensive data on the intensity of livestock grazing. As with an increasing number of species, it is confined to a network of small habitat patches and is threatened both by indirect human-induced factors (global warming) and by the direct activities of humans (in this case, livestock grazing and collection of medicinal plants). In the absence of global warming, grazing, and plant collection, our model suggested that the butterfly will persist for at least 200 years. Above a threshold intensity of global warming, the chance of extinction accelerated rapidly, implying that there may be an annual average temperature, specific to each endangered species, above which extinction becomes very much more likely. By contrast, there was no such threshold of grazing pressure—the chance of extinction increased steadily with increasing grazing. The impact of grazing, however, decreased with higher levels of year-to-year variation in habitat quality. The effect of global warming did not depend on the future level of grazing, suggesting that the impacts of global warming and grazing are additive. If the areas of habitat patches individually fall below certain prescribed levels, the butterfly is likely to go extinct. Two patches were very important for persistence: if either were lost the species would probably go extinct. Our results have implications for the conservation management of all species whose habitats are at risk because of the direct activities of humans and in the longer term because of climate change.     

Bird Conservation in Brazil

Abstract:  Brazil has one of the richest avifaunas in the world, with recent estimates varying from 1696 to 1731 species. About 10% (193 taxa) of these are threatened. The Amazon has the highest number of species, followed by the Atlantic Forest and the Cerrado; most of Brazil's endemic birds, however, are in the Atlantic Forest. Brazil's threatened species occur mostly in the Atlantic Forest, especially in the southeast lowlands and the northeast. The Cerrado has the second highest number of threatened species. The two major threats to Brazilian birds are habitat loss, degradation, and fragmentation and hunting, most especially for illegal commerce. A number of conservation and research initiatives over the last 20 years have significantly improved our capacity to address and resolve major issues for bird conservation. Brazil requires a National Bird Conservation Plan to draw up priorities for research and conservation over the next decade.     

Accelerating Forest Succession in a Fragmented Landscape: The Role of Birds and Perches

Previous research suggests that in highly fragmented forest landscapes ecological succession can be arrested by lack of seeds, but that seed deposition abundance and diversity of bird-dispersed plants can be enhanced by bird-attracting structures such as snags. Consequently, bird perches remain a potential tool for accelerating ecological succession and reforesting disturbed land. Consequently, in order to determine the effectiveness of bird perches in reclaiming forested landscapes, seed dispersal, seedbank storage, and recruitment of bird-dispersed plants was studied on a central Florida mined site with clay-rich soil undergoing primary succession over a seven-year period. Data collection included 20 continuous months of seed dispersal data, an analysis of the total and germinable seedbanks, and plant recruitment at one and two years after a fire destroyed perches and burnt vegetation. Seed dispersal to perches reached a peak seedfall by weight in August, which was attributable to nonmigratory birds. Myrica cerifera, the most abundant species dispersed to the sites, was the only species dispersed during the winter and spring months, and it may be a keystone species for the frugivorous bird guild in central Florida. Seedfall beneath perches had a higher diversity of seed genera, and seed numbers (340 seeds m⁻² yr⁻¹) were 150 times greater than in sites without perches. Seeds of bird-dispersed plants in the seedbank under perches numbered 77 ± 33 (m⁻²) in total and 17 ± 5 for the viable seedbank. The population density of bird-dispersed plants was 1.4 and 2.0 plants m⁻² at one and two years afler the fire. Less than 0.06% of the dispersed seeds survived to become seedlings. Species composition shifted from seedfall to seedlings, with small-seeded, early-successional (r-selected) shrubs and herbs becoming relatively more common than the desired large-seeded, late-successional (K-selected) tree species. Perches attracted birds and associated seeds, but the physically harsh conditions created by primary succession and/or high predation on seeds appeared to reduce the success of the desired late-successional plant species. Nonetheless, there was a higher abundance and diversity of bird-dispersed plants under perches, suggesting that perch structures have a limited ability to enhance plant diversity under conditions of primary succession.     

Neighborhood phylodiversity affects plant performance

Facilitation and competition are ecological interactions that are crucial for the organization of plant communities. Facilitative interactions tend to occur among distantly related species, while the strength of competition tends to decrease with phylogenetic distance. The balance between both types of interactions will ultimately determine the specific composition of multispecies associations. Although multispecies patches are the arena in which coexistence develops among different phylogenetic groups within communities, the specific processes that occur across life stages have not been explored. Here we study how different species, in composing discrete patches in central Mexico, exert competitive or facilitative effects on seeds and seedlings. We relate these interactions to phylogenetic relationships among nurse species and beneficiary species, and among members of the patches. Survivorship and growth rates of the columnar cactus Neobuxbaumia mezcalaensis were highly positively related to increasing phylogenetic distance to different nurse species, to the presence of related species in patches, and to mean phylogenetic distances to the rest of the species in the patch. Each of these three elements influenced N. mezcalaensis differently, with different nurse species varying substantially in their early effects on emergence, and the nearest relatives and species composition of patches varying in their late effects on survival and growth. Our results emphasize that evolutionary relationships among co-occurring species in vegetation clumps exert direct and indirect effects on plants, affecting individual performance and species coexistence.     

Impacts of Livestock Grazing and Tree Clearing on Birds of Woodland and Riparian Habitats

Abstract:  We investigated the impact of pastoral management on birds in subtropical grassy eucalypt woodland in southeastern Queensland, Australia, where the patterns of land management have made it possible to disentangle the effects of livestock grazing from those of tree clearing. We recorded changes in bird species composition, density, and relative abundance across two woodland habitat types (riparian and nonriparian) and two levels of clearing (wooded and nonwooded) and three levels of livestock grazing (low, moderate, and high) replicated over space (1000 km²) and time (2001–2002). We predicted that species that depend on understory vegetation would be most negatively affected by livestock grazing. A Bayesian generalized linear model showed that the level of grazing had the greatest effect when trees were present. When trees were absent, the impact of grazing was overshadowed by the effects of a lack of trees. Over 65% of species responded to different levels of grazing, and the abundance of 42% of species varied markedly with habitat and grazing. The most common response to grazing was high species relative abundance under low levels of grazing (28% of species), species absence at high levels of grazing (20%), and an increase in abundance with increasing grazing (18%). Despite having similar bird assemblages, the effect of grazing was stronger in riparian habitat than in adjacent woodland habitat. Our results suggest that any level of commercial livestock grazing is detrimental to some woodland birds, particularly the understory-dependant species, as predicted. Nevertheless, provided trees are not cleared, a rich and abundant bird fauna can coexist with moderate levels of grazing. Habitats with high levels of grazing, on the other hand, resulted in a species-poor bird assemblage dominated by birds that are increasing in abundance nationally .     

Cars, Cows, and Checkerspot Butterflies: Nitrogen Deposition and Management of Nutrient-Poor Grasslands for a Threatened Species

Abstract: Nutrient-poor, serpentinitic soils in the San Francisco Bay area sustain a native grassland that supports many rare species, including the Bay checkerspot butterfly ( Euphydryas editha bayensis ). Nitrogen (N) deposition from air pollution threatens biodiversity in these grasslands because N is the primary limiting nutrient for plant growth on serpentinitic soils. I investigated the role of N deposition through surveys of butterfly and plant populations across different grazing regimes, by literature review, and with estimates of N deposition in the region. Several populations of the butterfly in south San Jose crashed following the cessation of cattle grazing. Nearby populations under continued grazing did not suffer similar declines. The immediate cause of the population crashes was rapid invasion by introduced annual grasses that crowded out the larval host plants of the butterfly. Ungrazed serpentinitic grasslands on the San Francisco Peninsula have largely resisted grass invasions for nearly four decades. Several lines of evidence indicate that dry N deposition from smog is responsible for the observed grass invasion. Fertilization experiments have shown that soil N limits grass invasion in serpentinitic soils. Estimated N deposition rates in south San Jose grasslands are 10–15 kg  N/ha/year; Peninsula sites have lower deposition, 4–6 kg N/ha/year. Grazing cattle select grasses over forbs, and grazing leads to a net export of N as cattle are removed for slaughter. Although poorly managed cattle grazing can significantly disrupt native ecosystems, in this case moderate, well-managed grazing is essential for maintaining native biodiversity in the face of invasive species and exogenous inputs of N from nearby urban areas.     

The Silent Mass Extinction of Insect Herbivores in Biodiversity Hotspots

Abstract: Habitat loss is silently leading numerous insects to extinction. Conservation efforts, however, have not been designed specifically to protect these organisms, despite their ecological and evolutionary significance. On the basis of species–host area equations, parameterized with data from the literature and interviews with botanical experts, I estimated the number of specialized plant‐feeding insects (i.e., monophages) that live in 34 biodiversity hotspots and the number committed to extinction because of habitat loss. I estimated that 795,971–1,602,423 monophagous insect species live in biodiversity hotspots on 150,371 endemic plant species, which is 5.3–10.6 monophages per plant species. I calculated that 213,830–547,500 monophagous species are committed to extinction in biodiversity hotspots because of reduction of the geographic range size of their endemic hosts. I provided rankings of biodiversity hotspots on the basis of estimated richness of monophagous insects and on estimated number of extinctions of monophagous species. Extinction rates were predicted to be higher in biodiversity hotspots located along strong environmental gradients and on archipelagos, where high spatial turnover of monophagous species along the geographic distribution of their endemic plants is likely. The results strongly support the overall strategy of selecting priority conservation areas worldwide primarily on the basis of richness of endemic plants. To face the global decline of insect herbivores, one must expand the coverage of the network of protected areas and improve the richness of native plants on private lands.     

Pastoral Politics: Gaddi Grazing, Degradation, and Biodiversity Conservation in Himachal Pradesh, India

Two assumptions underlie the current conservation focus worldwide. The first is that democratic governments can restrict human resource use within protected areas, and the second is that human land use for subsistence leads to degradation and is incompatible with the maintenance of high levels of biological diversity. An examination of official policy documents over the past century indicates that Gaddi herders of Himachal Pradesh, northwestern Indian Himalaya, have used political influence to circumvent bureaucratic policies of exclusion and that there is an absence of scientific evidence to support the notion that Gaddi grazing leads to land degradation. Although grazing intensity has profoundly shaped the structure and composition of the Siwalik forests (the Gaddi winter grazing grounds), as demonstrated by transect-based data presented here, deviations from a supposed "climax" community need not constitute degradation. A growing rather than declining cattle population attests to the regenerative capacities of these forests. Within the alpine meadows grazed by the Gaddi in summer, mean plant species richness increased along transects originating at herder camps and extending 250 m north of border camp sites. Intense grazing pressure or heavy manuring by livestock bedded at night are likely to be responsible for the observed low species diversity adjacent to the campsite, but the effect is insignificant at the level of the overall landscape. Interviews with borders also suggest the presence of a sizable, though hunted, mammalian fauna in these high altitude meadows. Recognition of the difficulties associated with implementing restrictive policies, and the fact that human land-use practices need not lead to degradation or to a decline in biological diversity, should lead to more inclusive conservation policies within protected areas as well as an expansion of the conservation focus beyond protected-area boundaries.     

Interacting Effects of Landownership, Land Use, and Endangered Species on Conservation of Southwestern U.S. Rangelands

Abstract:  The contemporary southwestern United States is characterized by fire-adapted ecosystems; large numbers of federally listed threatened and endangered species; a patchwork of federal, state, and private landownership; and a long history of livestock grazing as the predominant land use. I compared eight sites in southern Arizona and New Mexico to assess the interacting effects of these characteristics on conservation practices and outcomes. There was widespread interest and private-sector leadership in restoring fire to southwestern rangelands, and there is a shortage of predictive scientific knowledge about the effects of fire and livestock grazing on threatened and endangered species. It was easier to restore fire to lands that were either privately owned or not grazed, in part because of obstacles created by threatened and endangered species on grazed public lands. Collaborative management facilitated conservation practices and outcomes, and periodic removal of livestock may be necessary for conservation, but permanent livestock exclusion may be counterproductive because of interactions with land-use and landownership patterns.     

Urban Plants as Genetic Reservoirs or Threats to the Integrity of Bushland Plant Populations

Abstract:  Remnant plants in urban fringes and native plants in gardens have the potential to contribute to the conservation of threatened plants by increasing genetic diversity, effective size of populations, and levels of genetic connectedness. But they also pose a threat through the disruption of locally adapted gene pools. At Hyams Beach, New South Wales, Australia, four bushland stands of the rare shrub, Grevillea macleayana McGillivray, surround an urban area containing remnant and cultivated specimens of this species. Numbers of inflorescences per plant, fruits per plant, and visits by pollinators were similar for plants in urban gardens and bushland. Urban plants represented a substantial but complex genetic resource, displaying more genetic diversity than bushland plants judged by H_e , numbers of alleles per locus, and number of private alleles. Of 27 private alleles in urban plants, 17 occurred in a set of 19 exotic plants. Excluding the exotic plants, all five stands displayed a moderate differentiation ( F_ST = 0.14 ± 0.02), although the urban remnants clustered with two of the bushland stands. These patterns may be explained by high levels of selfing and inbreeding in this species and by long-distance dispersal (several seeds in the urban stand were fathered by plants in other stands). Genetic leakage (gene flow) from exotic plants to 321 seeds on surrounding remnant or bushland plants has not occurred. Our results demonstrate the conservation value of this group of urban plants, which are viable, productive, genetically diverse, and interconnected with bushland plants. Gene flow has apparently not yet led to genetic contamination of bushland populations, but high levels of inbreeding would make this a rare event and difficult to detect. Remnant plants in urban gardens could successfully contribute to recovery plans for endangered and vulnerable species.     

Availability and Extraction of Forest Products in Managed and Primary Forest around a Dayak Village in West Kalimantan, Indonesia

We examined the density and abundance of marketable products in managed forest (rubber gardens, fruit gardens, and dry rice fallows) and in primary forest surrounding the Dayak village of Kembera, near Gunung Palung National Park, West Kalimantan, Indonesia. We calculated the proportion of trees that were marketable and useful for local consumption by counting and identifying trees in each managed forest type, and we documented extraction of products through interviews. Villagers harvested four marketable tree products: tengkawang seeds ( Shorea stenoptera ), durian fruits (various Durio spp.), rubber ( Hevea brasiliensis ), and timber, especially Bornean ironwood ( Eusideroxylon zwageri ). We inventoried trees at least 20 cm diameter at breast height (dbh) of marketed species from 0.4-ha plots in primary forest ( n = 8) and from 0.1-ha plots in each managed forest type ( n = 10–11). With the exception of timber, the density of trees producing a marketable product was significantly higher in the forest type managed for that product than the density of the marketed species, or of similar wild species, in primary forest. Total abundance (product of density and available area) of durian and tengkawang was greater in primary forest; however, villagers gathered these products only from managed forest. We infer from this choice a greater efficiency of harvesting from trees in dense stands near the village. Historically, this choice resulted in deliberate development of fruit gardens in preference or in addition to gathering from the more distant, primary forest. Because of low product density in primary forest, extractive forest reserves or buffer zones designed to encourage the production of fruits such as tengkawang or durian may not provide a sufficient incentive for the protection of primary forest around Kembera and other Dayak villages near Gunung Palung National Park.     

The Effectiveness of Iberian Protected Areas in Conserving Terrestrial Biodiversity

Abstract:  The Iberian Peninsula harbors about 50% of European plant and terrestrial vertebrate species and more than 30% of European endemic species. Despite the global recognition of its importance, the selection of protected areas has been ad hoc and the effectiveness of such choices has rarely been assessed. We compiled the most comprehensive distributional data set of Iberian terrestrial plant and vertebrate species available to date and used it to assess the degree of species representation within existing protected areas. Existing protected areas in Spain and Portugal reasonably represented the plant and animal species we considered (73–98%). Nevertheless, species of some groups (amphibians, reptiles, birds, and gymnosperms) did not accumulate in protected areas at a rate higher than expected by chance ( p > 0.05). We determined that to conserve all vertebrate and plant species in the Iberian Peninsula, at least 36 additional areas are needed. Selection of additional areas for conservation would be facilitated if such areas coincided with sites of community importance (SCI) designated under the European Commission Habitats Directive. Additional areas required for full representation of the selected plant and animal species all coincide with SCI in Spain. Nevertheless, the degree of coincidence varies between 0.3% and 74.6%, and there is a possibility that important areas for conservation occur outside the SCI. Our results support the view that current SCI can be used for prioritization of areas for conservation, but a systematic reevaluation of conservation priorities in Spain and Portugal would be necessary to ensure that effective conservation of one of European's most important biodiversity regions is achieved.     

Challenges to Introducing and Managing Disturbance Regimes for Holocarpha macradenia, an Endangered Annual Grassland Forb

Abstract:  Introducing rare plants to new sites for conservation to offset effects of habitat destruction requires detailed knowledge of habitat requirements, plant demography, and management needs. We conducted a factorial experiment replicated at three coastal prairie sites to test the effects of clipping frequency and litter accumulation on seed germination, seedling survival, reproduction, and seedling recruitment of introduced populations of the endangered, tall-stature, annual forb, Holocarpha macradenia (DC.) E. Greene. Clipping favored H. macradenia , primarily by enhancing seed germination and flower production. Litter accumulation had no effect on seed germination, even after 5 years of treatments. Seedling recruitment was highly site specific with large numbers of recruits recorded at only one of three sites. Although recruitment of seedlings was higher in clipped plots for 2–3 years, by 4–5 years after introduction very few seedlings survived to reproduction in any treatment. We attribute this result to a combination of poor habitat quality, small population size, and lack of a seed bank. We were unsuccessful in introducing this relatively well-studied species of concern to apparently suitable habitat at multiple sites in multiple years, which suggests that translocating rare plant populations to mitigate for habitat destruction is an expensive and highly uncertain endeavor.