131 research outputs found
Regional aboveground live carbon losses due to drought-induced tree dieback in pinon-juniper ecosystems
No full textMultiscale analysis of tree cover and aboveground carbon stocks in pinyon-juniper woodlands
No full textWoody plant proliferation in North American drylands: A synthesis of impacts on ecosystem carbon balance
No full textThe Production and Consumption of Volatile Organic Compounds in Soil and Decomposing Litter
Get PDFNon-methane biogenic volatile organic compounds (BVOCs) are reactive, low molecular weight gases that play key roles in atmospheric chemistry, and in soils, where they can alter the rates of biogeochemical cycles and impact the growth of plants and soil organisms. However, the types and quantities of BVOCs released from or taken up by soils and decomposing litter remain poorly characterized as do the biotic and abiotic controls on these fluxes. We used proton transfer reaction mass spectrometry (PTR-MS) to quantify BVOC flux rates from decomposing litter under varying biotic and abiotic conditions. Microbial production was the primary source of BVOCs emitted from decomposing litter, while the types of BVOCs emitted from the litter differed in a predictable manner among litter types. The amount of carbon (C) emitted as VOCs from the some decomposing litter types was near equivalent to the amount emitted as CO2 from microbial respiration. Although nitrogen (N) amendments have been shown to increase CO2 emission rates from decomposing litter, we found that N amendments reduced BVOC emissions to near zero. We also examined BVOC fluxes in soil and litter under field conditions, quantifying the contribution of tree roots to flux rates. Tree roots, directly or indirectly, contributed to half of the total C emitted from the soil as BVOCs. Methanol was the BVOC emitted at the highest net rates in all studies, while isoprene was net consumed into the intact soil at the highest rates. This finding led us to investigate the microbial community involved in the consumption of isoprene. Using amplicon sequencing and experimental amendments of incubating soil with isoprene, we found that several phyla, known to consume other hydrocarbons, were responding positively to increasing isoprene concentrations. These microorganisms were able to consume approximately 70% of the isoprene added into the headspace of incubating soils, with consumption rates up to 770 pmol g-1 h-1. Together these results have increased or understanding of the biotic and abiotic controls on the consumption and production of BVOCs in the soil environment and these results highlight the importance of considering these effects when modeling BVOC flux rates and C dynamics.</p
The Production and Consumption of Volatile Organic Compounds in Soil and Decomposing Litter
Get PDFNon-methane biogenic volatile organic compounds (BVOCs) are reactive, low molecular weight gases that play key roles in atmospheric chemistry, and in soils, where they can alter the rates of biogeochemical cycles and impact the growth of plants and soil organisms. However, the types and quantities of BVOCs released from or taken up by soils and decomposing litter remain poorly characterized as do the biotic and abiotic controls on these fluxes. We used proton transfer reaction mass spectrometry (PTR-MS) to quantify BVOC flux rates from decomposing litter under varying biotic and abiotic conditions. Microbial production was the primary source of BVOCs emitted from decomposing litter, while the types of BVOCs emitted from the litter differed in a predictable manner among litter types. The amount of carbon (C) emitted as VOCs from the some decomposing litter types was near equivalent to the amount emitted as CO2 from microbial respiration. Although nitrogen (N) amendments have been shown to increase CO2 emission rates from decomposing litter, we found that N amendments reduced BVOC emissions to near zero. We also examined BVOC fluxes in soil and litter under field conditions, quantifying the contribution of tree roots to flux rates. Tree roots, directly or indirectly, contributed to half of the total C emitted from the soil as BVOCs. Methanol was the BVOC emitted at the highest net rates in all studies, while isoprene was net consumed into the intact soil at the highest rates. This finding led us to investigate the microbial community involved in the consumption of isoprene. Using amplicon sequencing and experimental amendments of incubating soil with isoprene, we found that several phyla, known to consume other hydrocarbons, were responding positively to increasing isoprene concentrations. These microorganisms were able to consume approximately 70% of the isoprene added into the headspace of incubating soils, with consumption rates up to 770 pmol g-1 h-1. Together these results have increased or understanding of the biotic and abiotic controls on the consumption and production of BVOCs in the soil environment and these results highlight the importance of considering these effects when modeling BVOC flux rates and C dynamics.</p
The Influence of Biological Soil Crust Inoculum on Dryland Vascular Plant Establishment in a Greenhouse Experiment
Get PDFBiocrusts influence vascular plant species performance by modifying soil stability, hydrology, and fertility. Multiple studies suggest that biocrusts have species-specific effects on plant species performance depending on plant characteristics and ecological context and that biocrust inoculum could be used in restoration. Therefore, by promoting the performance of some plant species, but inhibiting others, biocrusts may influence vascular plant community structure. In this study, I compared emergence and establishment of C3 and C4 perennial grasses and annual and perennial forbs grown in biocrust-inoculated versus bare-soil mesocosms in a greenhouse. I hypothesized that biocrust inoculum will increase germination, growth and species richness of a plant community composed of multiple plant functional types based on increased resource availability of soil moisture due to biocrusts soil binding effects that trap moisture and decrease evaporation as well as enhanced soil N availability through biocrusts fixing atmospheric N2. A seed mix containing five plant species was sown into 32 mesocosms containing full factorial crosses of two soil treatments (biocrust-inoculated versus bare-soil) and two watering levels (high-water versus low-water). To accept or refute my hypothesis, I tested parameters incorporating plant germination, growth, and species richness. Overall plant growth results indicate biocrusts did not benefit vascular pant species with neutral effects on germination (high-water) and plant species richness but negative effects on germination (low-water) and plant growth. However, the neutral effects that biocrust inoculum has on vascular plants shows that there may be few negative effects overall, allowing restoration to occur in a holistic way that restores both vascular plants and biocrusts.</p
Managing Soil Seed Banks and Pre-Treating Seeds to Enhance Rangeland Restoration
Get PDFRestoration of exotic species invaded rangelands is essential to enhance ecosystem function and services. Managing soil seed banks to increase the abundance and richness of native species and reduce that of exotic species play a crucial role in long-term success in degraded rangelands. In this context, herbicide application following native seed addition is one of the most effective restoration efforts. In this study, first, we examined the effects of herbicide application in three different frequencies (2, 4, and 5 sprays) and native seeding treatment with twelve native species on soil seed bank dynamics in Bromus spp. invaded land. We collected soil seed bank samples from each treatment combination then moved them to the greenhouse for growth and identification. We analyzed total seedling abundance and richness; exotic abundance and richness; native abundance and richness; and the abundance of key species (the first, second, and third most abundant species). We found that herbicide application and seed treatment did not significantly change the seed bank composition in terms of total and exotic abundance and richness. However, native species’ abundance and richness significantly increased. Among the treatment combinations, two sprays of herbicide with seeding may be used as a first step of restoration in Bromus inermis invaded rangelands. However, the number of native species’ seedlings was lower than expected. Seedling establishment is one of the major limitations in current rangeland restoration efforts. Thus, we evaluated the effects of pre-sowing seed treatments through polymer seed coating and Gibberellic acid (GA) on germination to improve the success of restoration efforts in invaded rangelands in the second chapter. We tested the effects of six seed coating combinations consisting of three polymer types (Ethocell, PLA 65, and PVP) and three solvents, Acetone (ACE), Ether (ETH), and Dichloromethane (DCM), for Gibberellic Acid (GA) on five native species (Nassella viridula, Gaillardia aristata, Linum lewisii, Dalea purpurea, Panicum virgatum). We sowed the seeds with each treatment combination into 280 different plots in the field then we counted the emerged seedlings in June 2021 and September 2021. We found that the treatments (Blank, 81B DCM, 82B ACE, and 82B ETH) only significantly increased the germination of N.viridula through time and decreased G.aristata with the 82B ACE and 82B ETH treatments. Each species we tested responded to the treatments uniquely, and the effects of GA on seed germination for rangeland species are still unclear. Overall, more research is necessary to determine how integrated restoration efforts with herbicide and native seed application change soil seed bank and which combination is the best for native species’ establishment to increase the success of rangeland restoration.</p
Managing Soil Seed Banks and Pre-Treating Seeds to Enhance Rangeland Restoration
Get PDFRestoration of exotic species invaded rangelands is essential to enhance ecosystem function and services. Managing soil seed banks to increase the abundance and richness of native species and reduce that of exotic species play a crucial role in long-term success in degraded rangelands. In this context, herbicide application following native seed addition is one of the most effective restoration efforts. In this study, first, we examined the effects of herbicide application in three different frequencies (2, 4, and 5 sprays) and native seeding treatment with twelve native species on soil seed bank dynamics in Bromus spp. invaded land. We collected soil seed bank samples from each treatment combination then moved them to the greenhouse for growth and identification. We analyzed total seedling abundance and richness; exotic abundance and richness; native abundance and richness; and the abundance of key species (the first, second, and third most abundant species). We found that herbicide application and seed treatment did not significantly change the seed bank composition in terms of total and exotic abundance and richness. However, native species’ abundance and richness significantly increased. Among the treatment combinations, two sprays of herbicide with seeding may be used as a first step of restoration in Bromus inermis invaded rangelands. However, the number of native species’ seedlings was lower than expected. Seedling establishment is one of the major limitations in current rangeland restoration efforts. Thus, we evaluated the effects of pre-sowing seed treatments through polymer seed coating and Gibberellic acid (GA) on germination to improve the success of restoration efforts in invaded rangelands in the second chapter. We tested the effects of six seed coating combinations consisting of three polymer types (Ethocell, PLA 65, and PVP) and three solvents, Acetone (ACE), Ether (ETH), and Dichloromethane (DCM), for Gibberellic Acid (GA) on five native species (Nassella viridula, Gaillardia aristata, Linum lewisii, Dalea purpurea, Panicum virgatum). We sowed the seeds with each treatment combination into 280 different plots in the field then we counted the emerged seedlings in June 2021 and September 2021. We found that the treatments (Blank, 81B DCM, 82B ACE, and 82B ETH) only significantly increased the germination of N.viridula through time and decreased G.aristata with the 82B ACE and 82B ETH treatments. Each species we tested responded to the treatments uniquely, and the effects of GA on seed germination for rangeland species are still unclear. Overall, more research is necessary to determine how integrated restoration efforts with herbicide and native seed application change soil seed bank and which combination is the best for native species’ establishment to increase the success of rangeland restoration.</p
The Influence of Biological Soil Crust Inoculum on Dryland Vascular Plant Establishment in a Greenhouse Experiment
Get PDFBiocrusts influence vascular plant species performance by modifying soil stability, hydrology, and fertility. Multiple studies suggest that biocrusts have species-specific effects on plant species performance depending on plant characteristics and ecological context and that biocrust inoculum could be used in restoration. Therefore, by promoting the performance of some plant species, but inhibiting others, biocrusts may influence vascular plant community structure. In this study, I compared emergence and establishment of C3 and C4 perennial grasses and annual and perennial forbs grown in biocrust-inoculated versus bare-soil mesocosms in a greenhouse. I hypothesized that biocrust inoculum will increase germination, growth and species richness of a plant community composed of multiple plant functional types based on increased resource availability of soil moisture due to biocrusts soil binding effects that trap moisture and decrease evaporation as well as enhanced soil N availability through biocrusts fixing atmospheric N2. A seed mix containing five plant species was sown into 32 mesocosms containing full factorial crosses of two soil treatments (biocrust-inoculated versus bare-soil) and two watering levels (high-water versus low-water). To accept or refute my hypothesis, I tested parameters incorporating plant germination, growth, and species richness. Overall plant growth results indicate biocrusts did not benefit vascular pant species with neutral effects on germination (high-water) and plant species richness but negative effects on germination (low-water) and plant growth. However, the neutral effects that biocrust inoculum has on vascular plants shows that there may be few negative effects overall, allowing restoration to occur in a holistic way that restores both vascular plants and biocrusts.</p
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