Consequences of above-ground invasion by non-native plants into restored vernal pools do not prompt same changes in below-ground processes

Given the frequent overlap between biological plant invasion and ecological restoration efforts it is important to investigate their interactions to sustain desirable plant communities and modify long-Term legacies both above-and below-ground. To address this relationship, we used natural reference, invaded and created vernal pools in the Central Valley of California to examine potential changes in direct and indirect plant effects on soils associated with biological invasion and active restoration ecosystem disturbances. Our results showed that through a shift in vegetation composition and changes in the plant community tissue chemistry, invasion by non-native plant species has the potential to transform plant inputs to soils in vernal pool systems. In particular, we found that while invasive plant litter decomposition was driven by seasonal and interannual variability, associated with changes in precipitation, the overall decomposition rates for invasive litter was drastically lower than native species. This shift has important implications for long-Term alterations in plant-based inputs to soils in an amplifying feedback to nutrient cycling. Moreover, these results were independent of historic active restoration efforts. Despite the consistent shift in plant litter decomposition rates and community composition, we did not detect associated shifts in below-ground function associated with invasion by non-native plants. Instead, soil C:N ratios and microbial biomass did not differ between invaded and naturally occurring reference pools but were reduced in the manipulated created pools independent of invasion levels. Our results suggest that while there is an observed invasive amplifying feedback above-ground this trajectory is not represented below-ground, and restoration legacies dominated 10 years after practices were applied. Restoration practices that limit invasive plant feedbacks and account for soil legacy recovery, therefore offer the best solution for disturbed ephemeral ecosystems

A North American dust emission climatology (2001–2020) calibrated to dust point sources from satellite observations

Measurements of atmospheric dust have long influenced our understanding of dust sources and dust model calibration. However, assessing dust emission magnitude and frequency may reveal different dust source dynamics and is critical for informing land management. Here we use MODIS (500 m) albedo-based daily wind friction estimates to produce a new dust emission climatology of North America (2001–2020), calibrated by the novel use of dust point sources from optical satellite observations (rather than being tuned to dust in the atmosphere). Calibrated dust emission occurred predominantly in the biomes of the Great Plains (GP) and North American Deserts (NAD), in broad agreement with maps of aerosol optical depth and dust deposition but with considerably smaller frequency and magnitude. Combined, these biomes produced 7.2 Tg y-1 with contributions split between biomes (59.8% NAD, 40.2% GP) due to the contrasting conditions. Dust emission is dependent on different wind friction conditions on either side of the Rocky Mountains. In general, across the deserts, aerodynamic roughness was persistently small and dust sources were activated in areas prone to large wind speeds; desert dust emissions were wind speed limited. Across the Great Plains, large winds persist, and dust emission occurred when vegetation cover was reduced; vegetated dust emissions were roughness limited. We found comparable aerodynamic roughness exists across biomes/vegetation classes demonstrating that dust emission areas are not restricted to a single biome, instead they are spread across an ‘envelope’ of conducive wind friction conditions. Wind friction dynamics, describing the interplay between changing vegetation roughness (e.g., due to climate and land management) and changing winds (stilling and its reversal), influence modelled dust emission magnitude and frequency and its current and future climatology. We confirm previous results that in the second half of the 21st century the southern Great Plains is the most vulnerable to increased dust emission and show for the first time that risk is due to increased wind friction (by decreased vegetation roughness and / or increased wind speed). Regardless of how well calibrated models are to atmospheric dust, assuming roughness is static in time and / or homogeneous over space, will not adequately represent current and future dust source dynamics

Broader Impacts for Ecologists: Biological Soil Crust as a Model System for Education

Biological soil crusts (biocrusts) are a complex community of algae, cyanobacteria, lichens, bryophytes, and assorted bacteria, fungi, archaea, and bacteriophages that colonize the soil surface. Biocrusts are particularly common in drylands and are found in arid and semiarid ecosystems worldwide. While diminutive in size, biocrusts often cover large terrestrial areas, provide numerous ecosystem benefits, enhance biodiversity, and are found in multiple configurations and assemblages across different climate and disturbance regimes. Biocrusts have been a focus of many ecologists, especially those working in semiarid and arid lands, as biocrusts are foundational community members, play fundamental roles in ecosystem processes, and offer rare opportunities to study biological interactions at small and large spatial scales. Due to these same characteristics, biocrusts have the potential to serve as an excellent teaching tool. The purpose of this paper is to demonstrate the utility of biocrust communities as a model system in science education. Functioning as portable, dynamic mini ecosystems, biocrusts can be used to teach about organisms, biodiversity, biotic interactions, abiotic controls, ecosystem processes, and even global change, and can be easy to use in nearly every classroom setup. For example, education principles, such as evolution and adaptation to stress, or structure and function (patterns and processes) can be applied by bringing biocrusts into the classroom as a teaching tool. In addition, discussing the utility of biocrusts in the classroom &ndash; including theory, hypothesis testing, experimentation, and hands-on learning &ndash; this document also provides tips and resources for developing education tools and activities geared toward impactful learning.</p

Author Correction: Drivers of seedling establishment success in dryland restoration efforts

1 Pág. Correción errata.In the version of this Article originally published, the surname of author Tina Parkhurst was incorrectly written as Schroeder. This has now been corrected.Peer reviewe

Banking on the past: seed banks as a reservoir for rare and native species in restored vernal pools

Citation: Faist AM, Ferrenberg S, Collinge SK. 2013. Banking on the past: seed banks as a reservoir for rare and native species in restored vernal pools. AoB PLANTS 5: plt043; doi:10.1093/aobpla/plt043 Abstract. Soil seed banks serve as reservoirs for future plant communities, and when diverse and abundant can buffer vegetation communities against environmental fluctuations. Sparse seed banks, however, may lead to future declines of already rare species. Seed banks in wetland communities are often robust and can persist over long time periods making wetlands model systems for studying the spatial and temporal links between above-and belowground communities. Using collected soils and germination trials, we assessed species diversity and density in the seed banks of restored, ephemeral wetlands (vernal pools) in California&apos;s Central Valley, USA. Using long-term vegetation surveys, we compared the community structure of seed banks to that of aboveground vegetation and assessed the temporal links between below-and aboveground communities. We also compared the proportional abundances of different cover classes as well as the abundance of native plants in seed banks to aboveground communities. The proportional abundances of both rare and native species were greater in seed bank samples than in aboveground samples, yet the seed bank had lower species richness than aboveground vegetation. However, the seed bank had greater levels of differentiation among pools (beta diversity; b) than aboveground samples. Additionally, the seed bank was more similar to the earlier (2003 -06) aboveground community than the more recent (2007 -10) aboveground community. The correlation of species composition in the current seed bank to an earlier aboveground community suggests that seed banks exhibit storage effects while aboveground species composition in this system is not driven by seed bank composition, but is perhaps due to environmental filtering. We conclude that the seed bank of these pools is neither prone to the same temporal rates of invasion as the aboveground community, nor is seed abundance presently a limiting factor in the aboveground frequency of native species or a promoting factor in plant invasions of these restored habitats

Aboveground and belowground arthropods experience different relative influences of stochastic versus deterministic community assembly processes following disturbance

Background Understanding patterns of biodiversity is a longstanding challenge in ecology. Similar to other biotic groups, arthropod community structure can be shaped by deterministic and stochastic processes, with limited understanding of what moderates the relative influence of these processes. Disturbances have been noted to alter the relative influence of deterministic and stochastic processes on community assembly in various study systems, implicating ecological disturbances as a potential moderator of these forces. Methods Using a disturbance gradient along a 5-year chronosequence of insect-induced tree mortality in a subalpine forest of the southern Rocky Mountains, Colorado, USA, we examined changes in community structure and relative influences of deterministic and stochastic processes in the assembly of aboveground (surface and litter-active species) and belowground (species active in organic and mineral soil layers) arthropod communities. Arthropods were sampled for all years of the chronosequence via pitfall traps (aboveground community) and modified Winkler funnels (belowground community) and sorted to morphospecies. Community structure of both communities were assessed via comparisons of morphospecies abundance, diversity, and composition. Assembly processes were inferred from a mixture of linear models and matrix correlations testing for community associations with environmental properties, and from null-deviation models comparing observed vs. expected levels of species turnover (Beta diversity) among samples. Results Tree mortality altered community structure in both aboveground and belowground arthropod communities, but null models suggested that aboveground communities experienced greater relative influences of deterministic processes, while the relative influence of stochastic processes increased for belowground communities. Additionally, Mantel tests and linear regression models revealed significant associations between the aboveground arthropod communities and vegetation and soil properties, but no significant association among belowground arthropod communities and environmental factors. Discussion Our results suggest context-dependent influences of stochastic and deterministic community assembly processes across different fractions of a spatially co-occurring ground-dwelling arthropod community following disturbance. This variation in assembly may be linked to contrasting ecological strategies and dispersal rates within above- and below-ground communities. Our findings add to a growing body of evidence indicating concurrent influences of stochastic and deterministic processes in community assembly, and highlight the need to consider potential variation across different fractions of biotic communities when testing community ecology theory and considering conservation strategies

Impacts of Mastication: Soil Seed Bank Responses to a Forest Thinning Treatment in Three Colorado (USA) Conifer Forest Types

Mastication is a forest fuel thinning treatment that involves chipping or shredding small trees and shrubs and depositing the material across the forest floor. By decreasing forest density mastication has been shown to lessen crown fire hazard, yet other impacts have only recently started to be studied. Our study evaluates how mastication treatments alter the density and composition of soil seed banks in three Colorado conifer forest types. The three forest types were (1) lodgepole pine, (2) ponderosa pine and (3) pinyon pine-juniper. Results showed that masticated sites contained higher seed bank densities than untreated sites: a pattern primarily driven by treatment effects in ponderosa pine forests. The seed bank was dominated by forbs regardless of forest type or treatment. This pattern of forb dominance was not observed in the aboveground vegetation cover as it demonstrated more even proportions of the functional groups. Graminoids showed a higher seed density in treated sites than untreated and, similarly, the identified non-native species only occurred in the treated ponderosa pine sites suggesting a potential belowground invasion for this forest type. These results suggest that presence of masticated material might not be creating a physical barrier hindering the transfer of seeds as predicted

Lab and Field Warming Similarly Advance Germination Date and Limit Germination Rate for High and Low Elevation Provenances of Two Widespread Subalpine Conifers

Accurately predicting upslope shifts in subalpine tree ranges with warming requires understanding how future forest populations will be affected by climate change, as these are the seed sources for new tree line and alpine populations. Early life history stages are particularly sensitive to climate and are also influenced by genetic variation among populations. We tested the climate sensitivity of germination and initial development for two widely distributed subalpine conifers, using controlled-environment growth chambers with one temperature regime from subalpine forest in the Colorado Rocky Mountains and one 5 °C warmer, and two soil moisture levels. We tracked germination rate and timing, rate of seedling development, and seedling morphology for two seed provenances separated by ~300 m elevation. Warming advanced germination timing and initial seedling development by a total of ~2 weeks, advances comparable to mean differences between provenances. Advances were similar for both provenances and species; however, warming reduced the overall germination rate, as did low soil moisture, only for Picea engelmannii. A three-year field warming and watering experiment planted with the same species and provenances yielded responses qualitatively consistent with the lab trials. Together these experiments indicate that in a warmer, drier climate, P. engelmannii germination, and thus regeneration, could decline, which could lead to declining subalpine forest populations, while Pinus flexilis forest populations could remain robust as a seed source for upslope range shifts

Dispersal Patterns of One-Seed Juniper Seeds Contained in Mammal Scats and Bird Pellets

We conducted a two-year study in New Mexico, USA, to determine the role of birds, lagomorphs, mesocarnivores, and porcupines in one-seed juniper (J. monosperma (Englem.) Sarg.) seed dispersal. We established random plots: (1) around cone-bearing juniper trees in the woodland; (2) around non-cone-bearing juniper trees in the woodland; (3) in woodland/grassland transition zones; and in (4) grassland habitats near juniper woodlands. We estimated seed density and tallied the number of plots with seeds deposited by each disperser group. Birds deposited the highest number of seeds/ha under the canopy of cone-bearing trees. Mesocarnivores were responsible for the highest average seed deposition in all other habitats. In juniper cone-bearing tree habitats, birds deposited seeds in 100% of plots under-canopy and 93% of plots outside-canopy. Seeds deposited by lagomorphs were observed in plots across all sampled habitats. Overall, seed deposition was greatest around cone-bearing juniper trees, followed by non-cone-bearing juniper trees, woodland-grassland transition zones, and grassland habitats. Birds deposited seeds primarily under cone-bearing tree perch sites. Lagomorphs deposited seeds widely in relatively high numbers across all habitats and are likely responsible for the greatest number of one-seed juniper seeds deposited on the soil surface at our research site

Dispersal Patterns of One-Seed Juniper Seeds Contained in Mammal Scats and Bird Pellets

We conducted a two-year study in New Mexico, USA, to determine the role of birds, lagomorphs, mesocarnivores, and porcupines in one-seed juniper (J. monosperma (Englem.) Sarg.) seed dispersal. We established random plots: (1) around cone-bearing juniper trees in the woodland; (2) around non-cone-bearing juniper trees in the woodland; (3) in woodland/grassland transition zones; and in (4) grassland habitats near juniper woodlands. We estimated seed density and tallied the number of plots with seeds deposited by each disperser group. Birds deposited the highest number of seeds/ha under the canopy of cone-bearing trees. Mesocarnivores were responsible for the highest average seed deposition in all other habitats. In juniper cone-bearing tree habitats, birds deposited seeds in 100% of plots under-canopy and 93% of plots outside-canopy. Seeds deposited by lagomorphs were observed in plots across all sampled habitats. Overall, seed deposition was greatest around cone-bearing juniper trees, followed by non-cone-bearing juniper trees, woodland-grassland transition zones, and grassland habitats. Birds deposited seeds primarily under cone-bearing tree perch sites. Lagomorphs deposited seeds widely in relatively high numbers across all habitats and are likely responsible for the greatest number of one-seed juniper seeds deposited on the soil surface at our research site