Identifying Barriers to Successful Establishment of Post-Fire Seeding in the Great Basin

The shift of Great Basin ecosystems from diverse shrub-grass communities to near monocultures of annual grasses has altered ecosystems, caused more frequent and intense fires, and led to an increased demand for plant material that can restore altered landscapes back to complex, diverse systems. The Bureau of Land Management (BLM) in Nevada currently spends millions of dollars through the Emergency Stabilization and Rehabilitation (ES&R) program each year to re-seed land affected by fire. Seeds used for revegetation face many barriers that often prevent their successful establishment in this semi-arid environment including precipitation and temperature limitation, competition with invasive species, and soil type. Field surveys were done to monitor revegetation patterns between years and across aspects at five fire sites in Elko County, NV. A novel common garden experiment was conducted to determine what plants traits increase establishment success in invaded, post-fire field sites. We collected seeds from drill seeded populations of Elymus elymoides ssp. californicus (Toe Jam Creek bottlebrush squirreltail) at two fire locations in Elko County, NV. Seeds were planted in a common garden environment, where we compared the phenology, size, and reproduction of surviving plants to those of the original restoration material.In our field survey study, we found that vegetation structure within a site changed significantly in the short distance separating flat, north and south facing aspects; Bromus tectorum (cheatgrass) was more likely to establish on south aspects, residual grasses were more likely to remain on north aspects, and seeded perennial grasses were more likely to establish on flat areas. Over time, the density of B. tectorum and non-seeded perennial grasses and forbs increased, whereas the density of seeded perennial grasses and forbs decreased. We found that for both seeded and residual perennial grass, plant density in 2007 was a good predictor of the plant density in 2009. The density of B. tectorum in 2007 also predicted the density of B. tectorum in 2009, but not as strongly as perennial species. In our common garden experiment, plants grown from the original restoration material were larger, produced larger and more seeds, and produced seeds later in the season, while plants grown from material that successfully established at the restoration sites were smaller, produced smaller and fewer seeds, and produced them earlier. Differences in seed size were observed at the family level and persisted in the common garden environment through the next generation, indicating that seed size is likely a genetic, rather than maternal environment, effect. These results were consistent across two different field sites. Natural selection, rather than genetic drift, is the most likely explanation for trait shifts observed in established seed material, and these results indicate that smaller plants may be better adapted for establishment in arid environments. Our results suggest that altering current monitoring and seed production techniques may increase restoration success in the Great Basin. Modifying management objectives, seed mixes, and seeding efforts for slope-aspect and pre-fire site conditions may result in more cost effective and successful restoration. Restoration practices may also be improved if plant developers select for traits that perform well at restoration sites, rather than in controlled, production environments

Kulpa Leger Evol Apps Data

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Data from: Strong natural selection during plant restoration favors an unexpected suite of plant traits

Restoration is an opportunity to study natural selection: one can measure the distribution of traits in source propagules used to found populations, compare this with the distribution of traits in successful recruits, and determine the strength and direction of selection on potentially adaptive traits. We asked if natural selection influenced seedling establishment during post-fire restoration in the Great Basin, an area where large-scale restoration occurs with a few widely available cultivars planted over a large range of environmental conditions. We collected seeds from established plants of the perennial grass Elymus elymoides ssp. californicus (squirreltail) at two restoration sites, and compared the distribution of phenotypic traits of surviving plants with the original pool of restoration seeds. Seeds were planted in common gardens for two generations. Plants grown from seeds that established in the field were a non-random subset of the original seeds, with directional selection consistently favoring a correlated suite of traits in both field sites: small plant and seed size, and earlier flowering phenology. These results demonstrate that natural selection can affect restoration establishment in strong and predictable ways, and that adaptive traits in these sites were opposite of the current criteria used for selection of restoration material in this system

Similarity of Nutrient Uptake and Root Dimensions of Engelmann Spruce and Subalpine Fir at Two Contrasting Sites in Colorado

Nutrient uptake capacity is an important parameter in modeling nutrient uptake by plants. Researchers commonly assume that uptake capacity measured for a species can be used across sites. We tested this assumption by measuring the nutrient uptake capacity of intact roots of Engelmann spruce (Picea engelmanni Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) at Loch Vale Watershed and Fraser Experimental Forest in the Rocky Mountains of central Colorado. Roots still attached to the tree were exposed to one of three concentrations of nutrient solutions for time periods ranging from 1 to 96h, and solutions were analyzed for ammonium, nitrate, calcium, magnesium, and potassium. Surprisingly, the two species were indistinguishable in nutrient uptake within site for all nutrients (P \u3e0.25), but uptake rates differed by site. In general, nutrient uptake was higher at Fraser (P =0.01, 0.15, 0.03, and 0.18 for NH4+, NO3−, Ca2+, and K+, respectively), which is west of the Continental Divide and has lower atmospheric deposition of N than Loch Vale. Mean uptake rates by site for ambient solution concentrations were , , , and at Loch Vale, and , , , and at Fraser. The importance of site conditions in determining uptake capacity should not be overlooked when parameterizing nutrient uptake models. We also characterized the root morphology of these two species and compared them to other tree species we have measured at various sites in the northeastern USA. Engelmann spruce and subalpine fir were indistinguishable in specific root length and diameter distribution, while most of the other 10 species had statistically distinct diameter distributions across five diameter classes

DataSheet_1_Field observations and remote assessment identify climate change, recreation, invasive species, and livestock as top threats to critically imperiled rare plants in Nevada.pdf

IntroductionRare plant species comprise >36.5% of the world’s flora and disproportionately support ecosystem function and resilience. However, rare species also lead global plant extinctions, and unique ecological characteristics can make them vulnerable to anthropogenic pressure. Despite their vulnerability, many rare plants receive less monitoring than is needed to inform conservation efforts due to limited capacity for field surveys.MethodsWe used field observations and geospatial data to summarize how 128 imperiled, rare vascular plant species in Nevada are affected by various threats. We assessed correlations between threats predicted by geospatial data and threats observed on the ground and asked how historic and current threats compare.ResultsThe most commonly observed threats were from recreation, invasive and non-native/alien species, and livestock farming and ranching. Threat prevalence varied by elevation (e.g., a greater variety of threats at lower elevations, greater threat from climate change observed at higher elevations) and land management. There was a 28.1% overall correlation between predicted and observed threats, which was stronger for some threats (e.g., development of housing and urban areas, livestock farming and ranching) than others. All species experienced extreme climatic differences during 1990-2020 compared to baseline conditions, with the most extreme change in southern Nevada. The average number of threats observed per occurrence increased by 0.024 each decade.DiscussionWhile geospatial data did not perfectly predict observed threats, many of these occurrences have not been visited in over 30 years, and correlations may be stronger than we were able to detect here. Our approach can be used to help guide proactive monitoring, conservation, and research efforts for vulnerable species. </p

Microglial senescence contributes to female-biased neuroinflammation in the aging mouse hippocampus: implications for Alzheimer’s disease

Abstract Background Microglia, the brain’s principal immune cells, have been implicated in the pathogenesis of Alzheimer’s disease (AD), a condition shown to affect more females than males. Although sex differences in microglial function and transcriptomic programming have been described across development and in disease models of AD, no studies have comprehensively identified the sex divergences that emerge in the aging mouse hippocampus. Further, existing models of AD generally develop pathology (amyloid plaques and tau tangles) early in life and fail to recapitulate the aged brain environment associated with late-onset AD. Here, we examined and compared transcriptomic and translatomic sex effects in young and old murine hippocampal microglia. Methods Hippocampal tissue from C57BL6/N and microglial NuTRAP mice of both sexes were collected at young (5–6 month-old [mo]) and old (22–25 mo) ages. Cell sorting and affinity purification techniques were used to isolate the microglial transcriptome and translatome for RNA-sequencing and differential expression analyses. Flow cytometry, qPCR, and imaging approaches were used to confirm the transcriptomic and translatomic findings. Results There were marginal sex differences identified in the young hippocampal microglia, with most differentially expressed genes (DEGs) restricted to the sex chromosomes. Both sex chromosomally and autosomally encoded sex differences emerged with aging. These sex DEGs identified at old age were primarily female-biased and enriched in senescent and disease-associated microglial signatures. Normalized gene expression values can be accessed through a searchable web interface ( https://neuroepigenomics.omrf.org/ ). Pathway analyses identified upstream regulators induced to a greater extent in females than in males, including inflammatory mediators IFNG, TNF, and IL1B, as well as AD-risk genes TREM2 and APP. Conclusions These data suggest that female microglia adopt disease-associated and senescent phenotypes in the aging mouse hippocampus, even in the absence of disease pathology, to a greater extent than males. This sexually divergent microglial phenotype may explain the difference in susceptibility and disease progression in the case of AD pathology. Future studies will need to explore sex differences in microglial heterogeneity in response to AD pathology and determine how sex-specific regulators (i.e., sex chromosomal or hormonal) elicit these sex effects