1,721,048 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 textSeed Bank Analysis Post Fuels-Reduction Treatments
Get PDFPinyon-Juniper (P-J) ecosystems are extensive throughout the western U.S. and have been expanding into shrublands and grasslands. A variety of tree-removal methods have been used in an attempt to restore herbaceous cover and reduce the risk of catastrophic fire with unknown effects on plant communities. I examined the impact of three different fuels reduction treatments on the local seed bank. The treatments were: mastication, where fuels are mulched and left in the plot; broadcast burn, where fuels are spread evenly across the plot and burned; and pile burn, where fuels are placed in discrete piles and burned. Treatments were adjacent to an untreated control site. The plot subjected to the pile burn treatment had a significantly higher seedling density (P = 0.04) than plot subjected to the broadcast burn treatment. Additionally, the plot subjected to the pile burn treatment had significantly higher species diversity (P = 0.0004) than the control. Artificial seeding, preformed by the Bureau of Land Management, had no effect on seedling density (P > 0.05), but did significantly lower species diversity (P < 0.0001). This study indicates that treatment, most notably the pile burn treatment, has an effect on seedling density and species diversity, while seeding nly affected species diversity
Woody plant proliferation in North American drylands: A synthesis of impacts on ecosystem carbon balance
No full textThe 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
Seed Bank Analysis Post Fuels-Reduction Treatments
Get PDFPinyon-Juniper (P-J) ecosystems are extensive throughout the western U.S. and have been expanding into shrublands and grasslands. A variety of tree-removal methods have been used in an attempt to restore herbaceous cover and reduce the risk of catastrophic fire with unknown effects on plant communities. I examined the impact of three different fuels reduction treatments on the local seed bank. The treatments were: mastication, where fuels are mulched and left in the plot; broadcast burn, where fuels are spread evenly across the plot and burned; and pile burn, where fuels are placed in discrete piles and burned. Treatments were adjacent to an untreated control site. The plot subjected to the pile burn treatment had a significantly higher seedling density (P = 0.04) than plot subjected to the broadcast burn treatment. Additionally, the plot subjected to the pile burn treatment had significantly higher species diversity (P = 0.0004) than the control. Artificial seeding, preformed by the Bureau of Land Management, had no effect on seedling density (P > 0.05), but did significantly lower species diversity (P < 0.0001). This study indicates that treatment, most notably the pile burn treatment, has an effect on seedling density and species diversity, while seeding nly affected species diversity
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
Fuel Reduction Treatment Effects on Soil in Piñon-Juniper Woodlands
Get PDFIncreased infilling and expansion of shrubby woodlands into grasslands has been observed worldwide since European settlement, which has led to serious fuel loads and the risk of severe fire. Under the National Fire Plan in the U.S., fuel reduction treatments have been implemented in order to reduce risk of hazardous wildfire and restore ecosystem structure and function in these woodlands. Piñon-juniper (“P-J”) woodlands are often the most spatially extensive vegetation type and are often targeted for fuel reduction and restoration. In this study, we evaluated soil responses in an upland P-J woodland on the Colorado Plateau to three fuel reduction treatments: 1) mechanical shredding (“mastication”), 2) hand thinned debris burned in piles (“pile burn”), and 3) hand thinned debris scattered across the land then burned (“broadcast burn”), one (2010), two (2011), and six (2015) growing seasons post-treatment. We quantified biocrust presence, soil aggregate stability, and percent cover of woody debris and litter as indicators of soil response to tree removal treatments. If land management goals are to implement fuel reduction treatments while promoting soil health, our results indicate the mastication treatments are best in terms of soil structure and function
The Role of Native Ecosystems in Constraining Alien Tree Invasions
Get PDFAlien tree invasions cause widespread impacts to ecosystem structure and function in many regions across the globe. Limiting the spread of these invasions into untransformed native ecosystems is often a management priority. Understanding the mechanisms by which these native ecosystems are able to resist tree invasion can not only enhance our understanding of invasion processes but may also aid in predicting invasion risk and informing management decisions on monitoring, removal and restoration. Australian Acacia species are particularly invasive in the uniquely biodiverse Cape Floristic Region of South Africa. The generalist reproductive biology of these species results in the ability to reproduce and spread widely in invaded regions. However, little is understood of the ability of native ecosystems to constrain the establishment and growth of these tree invaders. I thus investigated the ability of an untransformed South African shrubland to resist the establishment and growth of an invasive tree species, Acacia cyclops, in order to gain a mechanistic understanding of ecosystem resistance. My results indicate that herbivory by an abundant indigenous rodent resulted in mortality of 60-100 % of transplanted A. cyclops seedlings. Rodent behaviour, rather than densities influenced herbivory levels since rodents were less likely to forage in sparsely vegetated sandy areas. A separate experiment found that belowground competition reduced A. cyclops seedling survival by ca. 1.4–1.8-fold and biomass accumulation by 4–5-fold. A review of available evidence from published literature led me to conclude that if able to navigate early constraints and establish ecophysiological traits such as heteroblasty, N2-fixation and strong allocation to belowground biomass aid invasive Australian Acacias to overcome abiotic constraints. These findings indicate that native ecosystems constrain the survival and growth of an invasive tree species. Mechanisms of resistance may be useful in predicting invasion risks to different native communities, identifying targets for ecosystem restoration and informing decisions on management and clearing operations so as to maximize ecosystem resistance
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