Research and Publications
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The apparent failure of ecosystems to recover from increasingly widespread disturbance is a global concern. Despite growing focus on factors inhibiting resilience and restoration, we still know very little about how demographic and population processes influence recovery. Using inverse and forward demographic modelling of 531 post‐fire sagebrush populations across the western US, we show that demographic processes during recovery from seeds do not initially lead to population growth but rather to years of population decline, low density, and risk of extirpation after disturbance and restoration, even at sites with potential to support long‐term, stable populations. Changes in population structure, and resulting transient population dynamics, lead to a > 50% decline in population growth rate after disturbance and significant reductions in population density. Our results indicate that demographic processes influence the recovery of ecosystems from disturbance and that demographic analyses can be used by resource managers to anticipate ecological transformation risk.
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This brief explains how to find out what is in that container of seed. It is divided into three sections:
- How to decipher a seed analysis label
- How to comprehend a certified seed label
- How to take a representative seed sample for analysis
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The primary goal of seed collecting by European Native Seed Conservation Network (ENSCONET) is the long-term conservation in seed banks of representative samples of the genetic diversity of seed-bearing plant populations. The methods included in this collecting manual should be widely applicable (including outside Europe), with adaptation as necessary to local circumstances. Where the biology of the species is well known, the methods may be made more sophisticated. The quality of seed collections depends upon the expertise of the collector, the circumstances at the collection site on the day of collection, and the knowledge available. This guide helps to address the latter.
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This protocol outlines the procedures for making seed collections for Seeds of Success, part of the national Native Plant Materials Development Program. The purpose of the Seeds of Success program in the United States is to establish a national, high quality, accurately identified and well documented native plant species seed collection. All seed collections made following this protocol can be used to support development of geographically appropriate native plant materials for restoration and emergency fire rehabilitation. Each seed collection should comprise of a significant representation of the genetic variation within the sampled population. The national collection acts as the basis for off site (ex situ) conservation and, where and when appropriate, can be used for study and multiplication in the native plant materials development program.
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The Association of Official Seed Certifying Agencies (AOSCA) has implemented certification requirements and standards that accommodate plant germplasm (whether newly acquired accessions or named varieties) of native grasses, forbs, and woody plants. These certification procedures provide third-party verification of source, genetic identity, and genetic purity of wildland collected or field or nursery grown plant germplasm materials. This bulletin defines AOSCA plant germplasm types, describes certification procedures and labeling, and summarizes supporting guidelines, tables, and flow charts.
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Despite late twentieth‐century increases in area burned, we show that Pacific Northwest forests have experienced an order of magnitude less fire over 32 yr than expected under historic fire regimes. Within fires that have burned, severity distributions are disconnected from historical references. From 1984 to 2015, 1.6 M ha burned; this is 13.3–18.9 M ha less than expected. Deficits were greatest in dry forest ecosystems adapted to frequent, low‐severity fire, where 7.2–10.3 M ha of low‐severity fire was missing, compared to a 0.2–1.1 M ha deficit of high‐severity fire. When these dry forests do burn, we observed that 36% burned with high‐severity compared to 6–9% historically. We found smaller fire deficits, 0.3–0.6 M ha, within forest ecosystems adapted to infrequent, high‐severity fire. However, we also acknowledge inherent limitations in evaluating contemporary fire regimes in ecosystems which historically burned infrequently and for which fires were highly episodic. The magnitude of contemporary fire deficits and disconnect in burn severity compared to historic fire regimes have important implications for climate change adaptation. Within forests characterized by low‐ and mixed‐severity historic fire regimes, simply increasing wildfire extent while maintaining current trends in burn severity threatens ecosystem resilience and will potentially drive undesirable ecosystem transformations. Restoring natural fire regimes requires management that facilitates much more low‐ and moderate‐severity fire.
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Wildland firefighters in the United States are exposed to a variety of hazards while performing their jobs in America’s wildlands. Although the threats posed by vehicle accidents, aircraft mishaps, and heart attacks claim the most lives, situations where firefighters are caught in a life-threatening, fire behavior-related event (i.e. an entrapment) constitute a considerable danger because each instance can affect many individuals. In an attempt to identify the scope of understanding of the causes of firefighter entrapments a review of the pertinent literature and a compilation and synthesis of existing data were undertaken.
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The results of this study indicate that post-fire natural regeneration in the Blue Mountains over the last 20 years has generally been sufficient to maintain forest resilience. Recruitment differs dramatically, however, across sites. In burned areas with abundant surviving adult trees 100 m away or less and on north-facing slopes, hundreds or thousands of seedlings per hectare may establish within the first 10 to 15 years post-fire. In contrast, conifer densities in large high-severity burn patches (i.e., larger than 100 to 200 m in radius) with high overstory mortality, especially those on warmer sites, may be insufficient to meet local silvicultural guidelines or maintain forest ecosystem function without supplementary replanting. Some of these marginal sites may be susceptible to ecosystem state transitions to shrub or grasslands. The results of this study also suggest that as climate change causes temperatures to warm and increases the probability of growing season moisture deficits, Douglas-fir recruitment may decline in drought-prone sites. Ponderosa pine seedlings may be more resilient to warming conditions, though as warming continues they also will become vulnerable to drought stress.
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Historical fires burned every 9–10 years on average up until 1879, when fires ceased contemporaneous with introduction of Euro-American livestock grazing and timber harvest in upland forests. Abundant tree regeneration occurred after fire exclusion, with tree density averaging 45 trees ha−1 in reconstructed 1880 forests versus 106 trees ha−1 today. Intervals between recent (since 1988) wildfires and prescribed fires in these same stands ranged from 7 to 13 years, similar to historical fire timing. Depending on whether plots had burned from zero to three times in recent fires, we found significant differences in canopy base heights (increased), duff and litter depths (decreased), and percent cover of grass and forbs (increased), but not tree density, tree basal area, shrub height, shrub cover, or woody fuels. Combined effects of recent fires on overstory and understory structure resulted in a significant difference in likelihood of crown fire occurrence, declining from a mean of 58% in plots with no fire since 1879 to 13% in plots with three fires since 1988. Significant effects were generally seen after two or three fires, suggesting it is the reintroduction of the fire regime and not just individual fire events that restore resiliency. Overall, effects of recent fires are building on the latent resiliency of ponderosa pine forests at Zion National Park, although questions remain about extent and future dynamics of oak and manzanita shrubfields that occupy similar environmental settings, along with a general lack of ponderosa pine regeneration across all plots.
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This study assessed causal relationships between conifer encroachment and sagebrush restoration (conifer removal and seeding native plants) on small mammal communities over 11 yr using a Before-After-Control–Impact design. Sagebrush habitat supported an additional small mammal species, twice the biomass, and nearly three times higher densities than conifer-encroached habitat. Sagebrush restoration increased shrub cover, decreased tree cover, and density but failed to increase native herbaceous plant density. Restoration caused a large increase in the non-native, invasive annual cheatgrass. Counter to prediction, small mammal diversity did not increase in response to sagebrush restoration, but restoration maintained small mammal density in the face of ongoing conifer encroachment. Piñon mice, woodland specialists with highest densities in conifer-encroached habitat, were negatively affected by sagebrush restoration. Increasing cheatgrass due to sagebrush restoration may not negatively impact small mammal diversity, provided cheatgrass density and cover do not progress to a monoculture and native vegetation is maintained. The consequences of conifer encroachment, a long-term, slow-acting impact, far outweigh the impacts of sagebrush restoration, a short-term, high-intensity impact, on small mammal diversity. Given the ecological importance of small mammals, maintenance of small mammal density is a desirable outcome for sagebrush restoration.