Studies were conducted to determine the effectiveness of using targeted grazing and prescribed burning as tools to reduce fire hazards and cheatgrass (Bromus tectorum) dominance on rangelands in the northern Great Basin. A field study, with four grazing-burning treatments (graze and no-burn, graze and burn, no-graze and burn, and no-graze and no-burn), was conducted on a B. tectorum-dominated site near McDermitt, Nevada from 2005-2007. Cattle removed 80-90% of standing biomass in grazed plots in May 2005 and 2006 when B. tectorum was in the boot (phenological) stage. Grazed and ungrazed plots were burned in October 2005 and 2006. Targeted grazing in May 2005 reduced B. tectorum biomass and cover, which resulted in reductions in flame length and rate of spread when plots were burned in October 2005. When grazing treatments were repeated on the same plots in May 2006, B. tectorum biomass and cover were reduced to the point that fires did not carry in grazed plots in October 2006. Fuel characteristics of the October 2005 burns were used to parameterize dry climate grass models in BehavePlus 3.0, and simulation modeling indicated that grazing in spring (May) would reduce the potential for catastrophic fires during the peak fire season (July-August). The graze-and-burn treatment was more effective than grazing alone (graze and no-burn treatment) and burning alone (no-graze and burn treatment) in reducing B. tectorum cover, biomass, plant density, and seed density, and in shifting species composition from a community dominated by B. tectorum to one composed of a suite of species [including tumble mustard (Sisymbrium altissimum), clasping pepperweed (Lepidium perfoliatum), and Sandberg bluegrass (Poa secunda)], with B. tectorum as a component rather than a dominant. A simulation study was designed to compare the cost-effectiveness of using cattle grazing and herbicide to create fuel breaks on B. tectorum-dominated landscapes in the northern Great Basin. Fuel characteristics from this targeted grazing study and from a Plateau® (Imazapic) herbicide study near Kuna, Idaho were used to parameterize fire behavior models and simulate flame lengths and rates of spread for the two fuel reduction treatments under peak fire conditions using BEHAVE Plus. Targeted grazing and Plateau® had similar reductions in flame length and rate of spread. Cattle grazing had high fixed costs (primarily fencing), and was more cost-effective than applications of Plateau® under five fuel loading scenarios except for three consecutive years of low fuel loads.

The control and eradication of the invasive biennial herb garlic mustard (Alliaria petiolata) and the restoration of invaded forest habitats present important linked challenges to land managers in North America. Removing garlic mustard by hand and by glyphosate herbicide application have both been used as eradication strategies with mixed results. Each method has advantages and disadvantages, but they are rarely compared for effectiveness and community impact across multiple years of management. Some previous studies have shown improvements in species diversity and plant community composition following management, while others have found no differences. To better understand both garlic mustard population and native plant community responses to these two methods across a broad geographic range, we tested these two management methods for four years in seven northern hardwood forests in Massachusetts and New York State. We found that pulling juvenile and adult garlic mustard plants for four years significantly reduced adult abundance, while spraying had no effect compared to invaded control plots. In the plant community, we found no negative impacts of garlic mustard on species diversity nor increased diversity in managed plots following three consecutive years of management. Our results suggest that increased diversity should not be the primary goal of garlic mustard management at these sites and plant community monitoring at the site-specific scale should be explored. This study highlights how complicated decisions can be for managers when deciding which invasions to prioritize and how to measure plant community recovery.

Invasive plants can outcompete native plants, replacing diverse plant communities with monocultures, which can negatively impact the whole ecosystem. One invasive plant, Phragmites australis, has invaded wetlands across North America. In Utah’s Great Salt Lake, it has greatly reduced the area of native plants that are important habitat for migratory birds. Here we describe experiments that assess multiple treatments for Phragmites removal and evaluate the return of native plants after Phragmites management. The treatments were applied to Phragmites patches at two scales (small 1/4-acre plots and large 3-acre plots) and across multiple sites to evaluate how patch size and environmental differences can influence the plants that return after Phragmites removal. The treatments (applied over 3 years and monitored two more) compared two different herbicides (glyphosate and imazapyr) and different herbicide and mowing timings. The treatments evaluated in the large patch study were 1.) untreated control 2.) fall glyphosate, winter mow, 3.) summer imazapyr, winter mow, 4.) summer glyphosate, winter mow. The treatments evaluated in the small patch study included treatments 1-4 above plus 5.) summer mow, fall glyphosate, 6.) summer mow, then black plastic solarization. In the small patches, we also monitored the seeds in the soil to assess how Phragmites management treatments can change the densities of Phragmites and native seeds. Fall glyphosate treatments were superior for Phragmites cover reduction. After the initial treatment, summer herbicide and mow treatments reduced Phragmites seed production, while fall glyphosate did not. Phragmites seeds were plentiful in the soil but were reduced following three years of all herbicide treatments. Native plant recovery following Phragmites management was extremely variable across sites. Sites with high soil moisture had better Phragmites removal and more native plants. But when flooding was deep, native plants were rare. Native seed density in the soil did not change due to Phragmites management, but soil seed densities were different across sites, which influenced native plant recruitment. Phragmites was removed more effectively and native plants returned in greater numbers in small patches compared with large. This was because small patches were typically near established native plant communities, which likely provided more native plant seeds and had hydrology that was less disturbed by human activity. In sites where native plants do not return after Phragmites management, practitioners may need to try revegetation with native plant seeds to restore important native plant communities.

<p dir="ltr">To reduce the establishment and spread of invasive plant species, the Environmental Quality Incentive Program (EQIP) was created in 1996 to provide financial and technical assistance to private landowners to aid in conservation practices and address environmental concerns. From 2014-2022, approximately $90 million dollars was obligated to the EQIP for completed contracts of over 240,000 hectares in Indiana. However, to date, there has been no examination of whether participation in conversation cost sharing programs has resulted in the recovery of native tree diversity, growth, and reproduction following the treatment of invasive plants. Furthermore, there is a gap in our understanding of the effectiveness of EQIP and its success in achieving and maintaining management goals. This thesis quantifies the composition, diversity, regeneration density and growth of tree species in response to invasive plant treatments at sites that participated in the EQIP. In particular, I investigated how the species composition of woody seedlings (stems < 2 cm dbh) and woody saplings (2 – 5 cm dbh) differed across EQIP-treated and untreated reference plots. I then examined how native species richness and diversity values differed between EQIP-treated and untreated plots. Lastly, I used dendroecological methods to determine how treatment of invasive shrubs affected overstory tree growth. Across the state, I found that native species richness of seedlings and saplings was greater in EQIP-treated plots then within reference plots. Reference plots were associated with invasive species such as <i>Lonicera maackii</i> (Amur honeysuckle), <i>Rosa multiflora</i> (multiflora rose), <i>Elaeagnus umbellata</i> (autumn olive) and <i>L. japonica</i> (Japanese honeysuckle), while EQIP-treated plots were associated with native tree species, such as <i>Carya ovata</i> (shagbark hickory),<i> Ulmus americana </i>(American elm), <i>Fraxinus americana</i> (white ash), <i>Liriodendron tulipifera</i> (yellow-poplar), <i>Quercus alba</i> (white oak), <i>Q. velutina</i> (black oak), and shrubs, such as <i>Rubus allegheniensis</i> (Allegheny blackberry) and <i>Lindera benzoin</i> (spicebush). I observed that trees generally had greater basal area increment growth following invasive shrub treatments; therefore, the reduction of invasive shrub dominance on EQIP-enrolled lands has led to a small, but significant, increase in overstory tree growth. I observed high within-group variability in growth for EQIP-treated and reference plots, likely due to differing management strategies across privately owned forests. Overall, my results demonstrate that participation in the EQIP has positively benefited species richness, and native species composition, and tree growth.</p>