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39th Annual Natural Areas Conference
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Join conservation professionals from around the country in Norfolk, Virginia, for the 2012 Natural Areas Conference: Keeping Natural Areas Relevant and Resilient.
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News & Events
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Events
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A century of climate and ecosystem change in Western Montana: what do temperature trends portend?
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Abstract The physical science linking human-induced increases ingreenhouse gasses to the warming of the global climate system is well established, but the implications of this warming for ecosystem processes and services at regional scales is still poorly understood. Thus, the objectives of this work were to: (1) describe rates of change in temperature averages and extremes for western Montana, a region containing sensitive resources and ecosystems, (2) investigate associations between Montana temperature change to hemispheric and global temperature change, (3) provide climate analysis tools for land and resource managers responsible for researching and maintaining renewable resources, habitat, and threatened/endangered species and (4) integrate our findings into a more general assessment of climate impacts on ecosystem processes and services over the past century. Over 100 years of daily and monthly temperature data collected in western Montana, USA are analyzed for long-term changes in seasonal averages and daily extremes. In particular, variability and trends in temperature above or below ecologically and socially meaningful thresholds within this region (e.g., −17.8◦C (0◦F), 0◦C (32◦F), and 32.2◦C (90◦F)) are assessed. The daily temperature time series reveal extremely cold days (≤ −17.8◦C) terminate on average 20 days earlier and decline in number, whereas extremely hot days (≥32◦C) show a three-fold increase in number and a 24-day increase in seasonal window during which they occur. Results show that regionally important thresholds have been exceeded, the most recent of which include the timing and number of the 0◦C freeze/thaw temperatures during spring and fall. Finally, we close with a discussion on the implications for Montana’s ecosystems. Special attention is given to critical processes that respond non-linearly as temperatures exceed critical thresholds, and have positive feedbacks that amplify the changes.
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Climate Science Documents
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A Crowning Achievement
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The Nature Conservancy plants 34,000 native red spruce trees to help bring back West Virginia’s mountaintop forests
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News & Events
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A dispersal-induced paradox: synchrony and stability in stochastic metapopulations
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Understanding how dispersal influences the dynamics of spatially distributed populations is a major priority of both basic and applied ecologists. Two well-known effects of dispersal are spatial synchrony (positively correlated population dynamics at different points in space) and dispersal-induced stability (the phenomenon whereby populations have simpler or less extinction-prone dynamics when they are linked by dispersal than when they are isolated). Although both these effects of dispersal should occur simultaneously, they have primarily been studied separately. Herein, I summarise evidence from the literature that these effects are expected to interact, and I use a series of models to characterise that interaction. In particular, I explore the observation that although dispersal can promote both synchrony and stability singly, it is widely held that synchrony paradoxically prevents dispersal-induced stability. I show here that in many realistic scenarios, dispersal is expected to promote both synchrony and stability at once despite this apparent destabilising influence of synchrony. This work demonstrates that studying the spatial and temporal impacts of dispersal together will be vital for the conservation and management of the many communities for which human activities are altering natural dispersal rates.
Keywords
Autoregressive model, correlated environmental stochasticity, dispersal, dispersal-induced stability, metapopulation, negative binomial model, Ricker model, spatial heterogeneity, synchrony.
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Climate Science Documents
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A drought-induced pervasive increase in tree mortality across Canada’s boreal forests
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Drought-induced tree mortality is expected to increase worldwide under projected future climate changes (1–4). The Canadian boreal forests, which occupy about 30% of the boreal forests worldwide and 77% of Canada’s total forested land, play a critical role in the albedo of Earth’s surface (5) and in its global carbon budget (6). Many of the previously reported regional-scale impacts of drought on tree mortality have affected low- and middle-latitude tropical regions (2) and the temperate forests of the western United States (3), but no study has examined high-latitude boreal regions with multiple species at a regional scale using long-term forest permanent sampling plots (7–9). Here, we estimated tree mortality in natural stands throughout Canada’s boreal forests using data from the permanent sampling plots and statistical models. We found that tree mortality rates increased by an overall average of 4.7%yr−1 from 1963 to 2008, with higher mortality rate increases in western regions than in eastern regions (about 4.9 and 1.9% yr−1 ,respectively).The water stress created by regional drought may be the dominant contributor to these widespread increases in tree mortality rates across tree species, sizes, elevations, longitudes and latitudes. Western Canada seems to have been more sensitive to drought than eastern Canada.
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Climate Science Documents
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A phylogenetic perspective on the distribution of plant diversity
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Phylogenetic studies are revealing that major ecological niches are more conserved through evolutionary history than expected, implying that adaptations to major climate changes have not readily been accomplished in all lineages. Phylogenetic niche conservatism has important consequences for the assembly of both local communities and the regional species pools from which these are drawn. If corridors for movement are available, newly emerging environments will tend to be filled by species that filter in from areas in which the relevant adaptations have already evolved, as opposed to being filled by in situ evolution of these adaptations. Examples include intercontinental disjunctions of tropical plants, the spread of plant lineages around the Northern Hemisphere after the evolution of cold tolerance, and the radiation of northern alpine plants into the Andes. These observations highlight the role of phylogenetic knowledge and historical biogeography in explanations of global biodiversity patterns. They also have implications for the future of biodiversity.
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Climate Science Documents
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Adaptive management of biological systems: A review
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Adaptive Management (AM) is widely considered to be the best available approach for managing biolog- ical systems in the presence of uncertainty. But AM has arguably only rarely succeeded in improving bio- diversity outcomes. There is therefore an urgent need for reflection regarding how practitioners might overcome key problems hindering greater implementation of AM. In this paper, we present the first structured review of the AM literature that relates to biodiversity and ecosystem management, with the aim of quantifying how rare AM projects actually are. We also investigated whether AM practitioners in terrestrial and aquatic systems described the same problems; the degree of consistency in how the term ‘adaptive management’ was applied; the extent to which AM projects were sustained over time; and whether articles describing AM projects were more highly cited than comparable non-AM articles. We found that despite the large number of articles identified through the ISI web of knowledge (n = 1336), only 61 articles (<5%) explicitly claimed to enact AM. These 61 articles cumulatively described 54 separate projects, but only 13 projects were supported by published monitoring data. The extent to which these 13 projects applied key aspects of the AM philosophy – such as referring to an underlying conceptual model, enacting ongoing monitoring, and comparing alternative management actions – varied enormously. Further, most AM projects were of short duration; terrestrial studies discussed biodiversity conservation significantly more frequently than aquatic studies; and empirical studies were no more highly cited than qualitative articles. Our review highlights that excessive use of the term ‘adaptive man- agement’ is rife in the peer-reviewed literature. However, a small but increasing number of projects have been able to effectively apply AM to complex problems. We suggest that attempts to apply AM may be improved by: (1) Better collaboration between scientists and representatives from resource-extracting industries. (2) Better communication of the risks of not doing AM. (3) Ensuring AM projects ‘‘pass the test of management relevance’’.
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Climate Science Documents
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Aeolian process effects on vegetation communities in an arid grassland ecosystem
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Many arid grassland communities are changing from grass dominance to shrub
dominance, but the mechanisms involved in this conversion process are not completely
understood. Aeolian processes likely contribute to this conversion from
grassland to shrubland. The purpose of this research is to provide information
regarding how vegetation changes occur in an arid grassland as a result of aeolian
sediment transport. The experimental design included three treatment blocks, each
with a 25 × 50 m area where all grasses, semi-shrubs, and perennial forbs were
hand removed, a 25 × 50 m control area with no manipulation of vegetation cover,
and two 10 × 25 m plots immediately downwind of the grass-removal and control
areas in the prevailing wind direction, 19◦ north of east, for measuring vegetation
cover. Aeolian sediment flux, soil nutrients, and soil seed bank were monitored on
each treatment area and downwind plot. Grass and shrub cover were measured on
each grass-removal, control, and downwind plot along continuous line transects as
well as on 5 × 10 m subplots within each downwind area over four years following
grass removal. On grass-removal areas, sediment flux increased significantly, soil
nutrients and seed bank were depleted, and Prosopis glandulosa shrub cover increased
compared to controls. Additionally, differential changes for grass and shrub
cover were observed for plots downwind of vegetation-removal and control areas.
Grass cover on plots downwind of vegetation-removal areas decreased over time
(2004–2007) despite above average rainfall throughout the period of observation,
while grass cover increased downwind of control areas; P. glandulosa cover increased
on plots downwind of vegetation-removal areas, while decreasing on plots downwind
of control areas. The relationships between vegetation changes and aeolian
sediment flux were significant and were best described by a logarithmic function,
with decreases in grass cover and increases in shrub cover occurring with small
increases in aeolian sediment flux
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Climate Science Documents
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Afforestation Effects on Soil Carbon Storage in the United States: A Synthesis
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Afforestation (tree establishment on nonforested land) is a management option for increasing terrestrial C sequestration and mitigating rising atmo- spheric carbon dioxide because, compared to nonforested land uses, afforestation increases C storage in aboveground pools. However, because terrestrial ecosystems typically store most of their C in soils, afforestation impacts on soil organic carbon (SOC) storage are critical components of eco- system C budgets. We applied synthesis methods to identify the magnitude and drivers of afforestation impacts on SOC, and the temporal and verti- cal distributions of SOC change during afforestation in the United States. Meta-analysis of 39 papers from 1957 to 2010 indicated that previous land use drives afforestation impacts on SOC in mineral soils (overall average = +21%), but mined and other industrial lands (+173%) and wildlands (+31%) were the only groups that specifically showed categorically significant increases. Temporal patterns of SOC increase were statistically significant on former industrial and agricultural lands (assessed by continuous meta- analysis), and suggested that meaningful SOC increases require ≥15 and 30 yr of afforestation, respectively. Meta-analysis of 13C data demonstrated the greatest SOC changes occur at the surface soil of the profile, although par- tial replacement of C stocks derived from previous land uses was frequently detectable below 1 m. A geospatial analysis of 409 profiles from the National Soil Carbon Network database supported 13C meta-analysis results, indicating that transition from cultivation to forest increased A horizon SOC by 32%. In sum, our findings demonstrate that afforestation has significant, positive effects on SOC sequestration in the United States, although these effects require decades to manifest and primarily occur in the uppermost (and per- haps most vulnerable) portion of the mineral soil profile.
Abbreviations: BD, bulk density; CI, confidence interval; MAP, mean annual precipitation; MAT, mean annual temperature; SOC, soil organic carbon.
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Agenda - March 11, 2015 Workshop
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Urban Woodlands Conservation and Management Workshop. Organized and facilitated by the National Park Service to identify and create opportunities for greater collaboration among urban woodland researchers and managers working to restore and manage urban woodland ecosystems.
To view the goals and objectives of the workshop, please open the workshop agenda.
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Cultural Resources
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Urban Conservation
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Urban Woodlands Conservation and Restoration
