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

Mosaic fungal individuals have the potential to evolve within a single generation

Although cells of mushroom-producing fungi typically contain paired haploid nuclei (n + n), most Armillaria gallica vegetative cells are uninucleate. As vegetative nuclei are produced by fusions of paired haploid nuclei, they are thought to be diploid (2n). Here we report finding haploid vegetative nuclei in A. gallica at multiple sites in southeastern Massachusetts, USA. Sequencing multiple clones of a single-copy gene isolated from single hyphal filaments revealed nuclear heterogeneity both among and within hyphae. Cytoplasmic bridges connected hyphae in field-collected and cultured samples, and we propose nuclear migration through bridges maintains this nuclear heterogeneity. Growth studies demonstrate among- and within-hypha phenotypic variation for growth in response to gallic acid, a plant-produced antifungal compound. The existence of both genetic and phenotypic variation within vegetative hyphae suggests that fungal individuals have the potential to evolve within a single generation in response to environmental variation over time and space

Alpine moist meadow response to nitrogen deposition in the greater Yellowstone ecosystem

The deposition of anthropogenic reactive nitrogen (N) in alpine ecosystems can have multiple deleterious effects on plants, soils and hydrology in both the alpine and areas downstream through leaching and export. Thresholds for ecological responses to N deposition have been established for lakes, soils and changes in plant community composition in some areas of the Rocky Mountains. These thresholds offer a target for land and air resource managers to prevent significant changes in ecosystem function, however the underlying feedbacks controlling ecosystem response have not been fully examined. Research originally proposed in association with our UW NPS Small Grant aimed to examine plant to ecosystem interactions within alpine moist meadows between two sites receiving different levels of N deposition. This focus has been modified, in response to site limitations, to examine the mediation of the N cycle by the alpine moist meadow plant community

Building human capacity, capability and future leaders for Australia's rangelands

Maintaining a skilled, knowledgeable and adaptable workforce in Australian rangeland enterprises and research, development and extension/adoption (RD&E/A) organisations is a varied and challenging task, compounded by trends of sustained losses of human capacity through senior retirements and short-term appointments over the last decade. Concerns for how to fill these gaps while gaining the skills and knowledge needed for a successful career and leadership roles were raised by students and young professionals in the World Cafe session and throughout Early Career workshops and activities at the 2019 Biennial Conference of the Australian Rangeland Society (ARS). This paper responds to these expressed information needs through drawing on literature, experiences shared by session participants, and existing ARS members currently working in the rangelands in diverse roles to provide insights into two main areas: (i) skills and knowledge for personal development and future success in the rangelands across three broad classes of occupation/careers (i.e. advisors, researchers, and producers), and (ii) skills and knowledge that will be expected of future leaders in the rangelands. We outline a variety of options for professional development in the early stage(s) of a career working on aspects of sustainable production systems and pathways to leadership throughout a career in the rangelands. We note the apparent lack of formal rangeland-specific education in Australia, and suggest that this is a major impediment to efforts to build skills and knowledge to ensure the viability of the livelihoods and the integrity of our rangelands. Finally, we believe that the ARS has the potential to play a more central role in inspiring interest and passion for the rangelands, in providing current information on (i) range science and management-relevant education and training opportunities in Australia and internationally, and (ii) leadership development and training opportunities; and in facilitating and supporting mentoring to develop and retain human capacity for a resilient future

A site for sori : ecophysiology of fertile–sterile leaf dimorphy in ferns

PREMISE OF THE STUDY: Reproduction often requires significant investment and can move resources away from growth and maintenance; maintaining a balance between reproduction and growth can involve trade-offs. Extreme functional specialization has separated reproduction and photosynthesis in most seed plants, yet ferns use the laminar surface of their fronds for both reproduction and photosynthesis. This dual function selects for a variety of frond morphologies that range from no specialization (monomorphy) to extreme dimorphy between fertile and sterile fronds (holodimorphy). Here we examined the ecological and physiological consequences of variation in frond dimorphy in ferns, evaluated reproductive trade-offs across a dimorphy gradient, and speculate on factors controlling the occurrence of holodimorphy. METHODS: Ecophysiological measurements of photosynthetic rate, water potential, hydraulic conductivity, and gross morphological comparisons of frond area and angle were used to evaluate differences between fertile and sterile fronds. We examined three temperate and three tropical fern species that vary in degree of fertile–sterile dimorphy. KEY RESULTS: Holodimorphic species produced fewer fertile fronds, which had significantly higher respiratory rates than in sterile fronds on the same plant or in any frond produced on monomorphic species; hemidimorphic species were frequently intermediate. We found no differences in vulnerability to cavitation between fertile and sterile fronds. In dimorphic species, fertile fronds had higher (less negative) water potential and lower stipe hydraulic conductivity relative than in sterile fronds. CONCLUSIONS: Fertile–sterile dimorphy in ferns appears to come at considerable carbon cost in holodimorohic species. It is possible that the relative costs of this reproductive system are off set by increased spore dispersal, yet such trade-offs require further exploration

Response of plant community structure and primary productivity to experimental drought and flooding in an Alaskan fen1

Northern peatlands represent a long-term net sink for atmospheric CO2, but these ecosystems can shift from net carbon (C) sinks to sources based on changing climate and environmental conditions. In particular, changes in water availability associated with climate control peatland vegetation and carbon uptake processes. We examined the influence of changing hydrology on plant species abundance and ecosystem primary production in an Alaskan fen by manipulating the water table in field treatments to mimic either sustained flooding (raised water table) or drought (lowered water table) conditions for 6 years. We found that water table treatments altered plant species abundance by increasing sedge and grass cover in the raised water table treatment and reducing moss cover while increasing vascular green area in the lowered water table treatment. Gross primary productivity was lower in the lowered treatment than in the other plots, although there were no differences in total biomass or vascular net primary productivity among the treatments. Overall, our results indicate that vegetation abundance was more sensitive to variation in water table than total biomass and vascular biomass accrual. Finally, in our experimental peatland, drought had stronger consequences for change in vegetation abundance and ecosystem function than sustained flooding

The combined effects of an extreme heatwave and wildfire on tallgrass prairie vegetation

Questions: Climate extremes are predicted to become more common in many ecosystems. Climate extremes can promote and interact with disturbances, but the combined effects of climate extremes and disturbances have not been quantified in many ecosystems. In this study, we ask whether the dual impact of a climate extreme and concomitant disturbance (wildfire) has a greater affect than a climate extreme alone. Location: Tallgrass prairie in the Konza Prairie Biological Station, northeastern Kansas, USA. Methods: We quantified the response of a tallgrass prairie plant community to a 2-year climate extreme of low growing-season precipitation and high temperatures. In the first year of the climate extreme, a subset of plots was burned by a growing-season wildfire. This natural experiment allowed us to compare community responses to a climate extreme with and without wildfire. Results: In plots exposed to the climate extreme but not wildfire, community structure, diversity, and composition showed minor to insignificant changes, such as a 20% reduction in grass cover and a slight increase in species diversity. Plots exposed to both the climate extreme and wildfire underwent larger changes, including an 80% reduction in grass cover, 50% increase in forb cover, and increased plant diversity. Two years after the climate extreme, structural shifts in burned plots showed little sign of recovery, indicating a potentially lasting shift in plant community structure. Conclusions: Our results suggest that community responses to climate extremes need to account for climate-related disturbances — in this case, high temperatures, drought and wildfire. This response diverged from our expectation that heat, drought, and an additional fire would favor grasses. Although growing-season wildfires in tallgrass prairie have been rare in recent decades, they will likely become more common with climate change, potentially leading to changes in grassland structure

Near infrared spectroscopy calibration strategies to predict multiple nutritional parameters of pasture species from different functional groups

Near infrared reflectance (NIR) spectroscopy has been used by the agricultural industry as a rapid and inexpensive technique to quantify nutritional chemistry in plants. The aim of this study was to evaluate the performance of NIR calibrations in predicting the nutritional composition of ten pasture species that underpin livestock industries in many countries. The species comprised a range of functional diversity (C3 legumes; C3/C4 grasses; annuals/perennials) and origins (tropical/temperate; introduced/native) that grew under varied environmental conditions (control and experimentally induced warming and drought) over a period of more than two years (n = 2622). A maximal calibration set including 391 samples was used to develop and evaluate calibrations for all ten pasture species (global calibrations), as well as for subsets comprised of the plant functional groups. This study found that the global calibrations were appropriate to predict the six key nutritional quality parameters for the studied pasture species, with the highest estimation quality found for ash (ASH), crude protein (CP), amylase-treated neutral detergent fibre (aNDF) and acid detergent fibre (ADF), and the lowest for ether extract (EE) and acid detergent lignin (ADL) parameters. The plant functional group calibrations for C3 grasses performed better than the global calibrations for ASH, CP, ADF and EE parameters, whereas for C3 legumes and C4 grasses the functional group calibrations performed less well than the global calibrations for all nutritional parameters of these groups. Additionally, the calibrations were able to capture the range of variation in forage nutritional quality caused by future climate scenarios of warming and severe drought

[In Press] Short-term drought is a stronger driver of plant morphology and nutritional composition than warming in two common pasture species

Under warmer and drier future conditions, global livestock and dairy production are threatened by impacts on the productivity and nutritional quality of pastures. However, morphological and nutritional adjustments within plants in response to warming and drought vary among species and less is known how these relate to production and forage quality. To investigate this, we grew two common pasture species, tall fescue (Festuca arundinacea: grass) and lucerne (Medicago sativa: legume), in a climate-controlled facility, under different temperatures (ambient and elevated) and watering regimes (well-watered and droughted). We found that drought had a strong negative impact on biomass production, morphology and nutritional quality while warming only significantly affected both species when response metrics were considered in concert, although to a lesser degree than the drought. Furthermore, interactions between warming and drought were only seen for lucerne, with a reduction in biomass and an increase in dead material and dry matter. In tall fescue, drought had bigger impacts on nutritional composition than morphological traits, while in lucerne, drought affected all morphological traits and most of the nutritional parameters. These findings suggest that in future climate scenarios, drought may be a stronger driver of changes in the morphology and nutritional composition of pasture grasses and legumes, compared to modest levels of warming

Transforming graduate training in STEM education

The need for improved instruction in college science, technology, engineering, and math (STEM) courses is a prominent national policy issue (Brewer and Smith 2011, Olson and Riordan 2012). To address this need, instruction in many college STEM courses is being revolutionized through the adoption of student-centered evidence-based teaching practices. There is a growing body of literature on how to employ these techniques and on the benefits of using empirically validated teaching practices in college classrooms (Handelsman et al. 2004, Allen and Tanner 2005, Haak2011). The majority of efforts in STEM education transformation are directed at faculty, while graduate student training in these practices has not kept pace. Pre-service faculty (i.e. graduate students) should receive training in pedagogy from the beginning of their education (Bouwma-Gearhart et al. 2007), just as K–12 science teachers receive professional development in both the pre-service and in-service stages of their careers. Offering graduate students more training in pedagogy and meaningful opportunities for practice throughout their graduate careers will benefit not only graduate students as they enter the workforce, but also the undergraduates and faculty at their institutions