Susan W. Beatty - US grants

The National Park Service and other conservation-oriented organizations historically have tried to maintain park land and wilderness areas in their natural conditions, but the invasion of exotic species often has altered indigenous plant communities. Nitrogen-fixing plants alter biogeochemical processes and facilitate future exotic invasions. This doctoral dissertation research project addresses spatial and resource competitive effects of an exotic species, yellow sweet clover (Melitotus officinalis), in montane grasslands in Rocky Mountain National Park. Preliminary analyses show that M. officinalis invasion spreads into native communities and induces an altered species composition from lowered nutrient availability and soil microclimate changes. Continued research will focus on the hypotheses that native species will benefit from prescribed burning and nitrogen manipulations while M. officinalis spread and density will decrease. Research methods to be used in this project include sampling soil and vegetation in replicate disturbed sites of invaded and non-invaded patches. Preliminary results show that M. officinalis expanded past original mapped boundaries throughout the season, and species composition is different between patches. Soil analysis shows lower nitrogen availability, net mineralization, and soil moisture in patches occupied by M. officinalis. Historical aerial photographs, global positioning systems, and geographic information systems will be used to map exotic invasion. Field methods during the latter stages of the project will incorporate prescribed burning in several sites and nitrogen manipulations along patch edges. This project will provide new insights into the processes of biological invasions and altered chemical processes. In addition to generating fundamental knowledge about these biogeographic and biogeochemical processes, this project will provide practical information for land managers, especially as it relates to the role that prescribed fires and nitrogen manipulations may play in the preservation of natural vegetation communities. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

The origin of landforms and soils along temporal landscape gradients long has been a topic of study and speculation in geomorphology, soil science, and related fields. This is true for sub-Arctic areas that were covered by glaciers until very late in the Pleistocene. While considerable attention has been given to analyzing the dates and processes that formed moraines and other landforms as well as soils, far less attention has been given to integrated examinations that link the development of micro-scale landform and soils with vegetational succession. This doctoral dissertation research project will investigate the geoecological controls on micro-scale landscape evolution in the late-Holocene deglaciated terrain of Jotunheimen in south-central Norway. The study will focus on local environmental parameters that were conducive for the formation of patterned ground initially after deglaciation, with attention also given to the processes that led to vegetation succession and soil development in the micro-scale (from 0.5 m to 3 m) patterned ground landforms. The central hypotheses of this project are that significant micro-scale soil development differences occur within patterned ground and are positively correlated to vegetation succession. Vegetation tends to establish itself on the periphery of patterned ground structures due to decreased frost activity. The biotic effects interrelated with the physical environmental parameters will be increasingly detectable in terms of soil genesis within patterned ground along a chronosequence transect. The project will include field work in two glacial forelands within the mountainous area of Jotunheimen. Extensive data are available on postglacial surface ages in the terrains before the Storbreen and Slettmarkbreen glaciers. This project will use these data in addition to data gathered through the excavation of soil pits. Vegetation also will be sampled to obtain measures of species composition, diversity, and coverage (biomass indicator). The results of this project will provide new insights into rapid landscape evolution induced by environmental change. Specifically, this study will contribute to the understanding of factors controlling soil formation, particularly the vegetation factor, and it will elucidate the ecological process of succession as controlled by substrate. This knowledge may then allow for predictions of future landscape changes in other mountainous areas. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

The boundaries between community types, which are rich sources of spatial heterogeneity, are related to a wide variety of biotic and abiotic edge effects. The prevalence of boundaries in modern landscapes emphasizes the need to understand their ecological function. In order to understand boundary function, improved knowledge is needed regarding how environmental factors and vegetation vary under human influence and across multiple scales. Measuring and understanding multi-scale influences is a significant challenge in many fields. This doctoral dissertation research project focuses on evaluating the relative influence of aspect (local scale), management regime (landscape scale), and atmospheric deposition (regional scale) on the character of forest-field edges in southern Sweden. More intensive management, especially increased fertilizer application, and greater atmospheric deposition have increased soil acidity and nitrogen availability in northern Europe's forest and grassland communities, which generally are quite nutrient-poor. These trends have led to marked changes in species composition and declines in plant diversity. Such interactions have likely been intensified across forest-field edges because of their ecological function as 'sinks' (areas where matter has accumulated). This project study will evaluate the general hypothesis that the biotic edge is directly related to abiotic controls and conditions that vary with respect to location and management regime. Specific objectives of this study are to determine abiotic and biotic variation across forest-field edges, to assess relationships between abiotic and biotic variables, and to identify edge characteristics and functions that differ with respect to location at the local, landscape, and regional scale. The study will be conducted in the southwest and east-central regions of Sweden. Locations of sampling sites reflect the regional gradient from high to low deposition. In each region, replicate sites will be located under each of two management regimes: traditional (non-fertilized) and intensively managed (fertilized) meadows. For each management regime, replicate sites will be sampled across a southwest-facing and a northeast-facing edge. Field research will consist of sampling vegetation and environmental characteristics (such as air and soil temperature, relative humidity, soil pH, and soil moisture tension) along forest-field edge gradients. Soil samples will be collected at a sub-set of sites for laboratory analyses.

The results of this project will have both theoretical and management implications. Despite its often-cited importance, multi-scale complexity across edges is not well understood. The project will explore a method for measuring and quantitatively examining the relative influence of processes operating at different scales across landscape boundaries. Results therefore will provide scientists and resource managers with important insights regarding the relationship between regional- and local-scale processes in a culturally fragmented landscape. In addition, by examining change in microclimate, soil conditions, and vegetation across forest-field edges under varying rates of acidic deposition and fertilization, a better understanding can be gained of how boundaries function under human-induced environmental change. Such environmental changes may have a direct effect on forestry, agriculture, water quality, and biodiversity. Findings from this study therefore can be used in land-use planning and environmental policy formation. The project should provide empirical support for the nature of forest-field boundaries in northern Europe as well as provide information about anthropogenic effects at multiple scales. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

The plant species composition of deciduous forest communities varies considerably from place to place. It is not fully understood what determines whether or not a given plant will be located in a given area. Plants are sometimes limited to specific areas because of their inability to tolerate certain environmental conditions, which may be the result of differences in the soil where they grow or the result of changes brought about by other plants or trees already growing at a site. Elsewhere, plants may be limited by their ability to get seeds or other reproductive material to a new site. This doctoral dissertation research project will examine the role that plant dispersal and forest age have in determining spatial pattern in the herbaceous vegetation located underneath the canopy trees in the hardwood-hemlock forest of the Edmund Niles Huyck Preserve in central New York State. The Huyck Preserve provides the opportunity to study forest change over the last 150 years, because most of the area of the preserve was logged sometime during that time period, thereby providing a mosaic of forest types of varying age. The goals of this project are to determine if the type of dispersal a plant uses is related to whether or not it is present in a forest stand of a certain age and to determine if the likelihood of a species being contained in an area is dependent on that species being present in a nearby area. These relationships will be determined by examining the vegetation and the age of 30 to 40 forest stands of the Huyck Preserve. The locations of these stands will be specificed along with their distances from each other. The plant species located in these areas will be grouped by the type of dispersal they use to propogate themselves (wind, animal, gravity, etc.) as well as patterns associated with the age of forest stands. Among the hypotheses that will be explored is whether species using rapid, long-distance dispersal will appear in younger areas before species using slower, more geographically restricted modes of dispersal. Species composition in each area will be compared with species composition in adjacent areas. A hypothesis to be tested in this facet of the project is whether the species composition of an area is dependent on the species composition of other areas. This dependency may also be influenced by physical factors like wind or slope direction, as there may be greater concentration of species in areas located immediately downwind or downslope from established species. These results should help to clarify role that dispersal plays in determination of species composition patterns.

This research will help advance understanding of the role plant dispersal plays in determining which species live where. This will complement what already is known about other factors that influence where plants live, such as how plants interact with the environment and how they interact with other plant species. This type of knowledge is necessary in a conservation context, because knowing the processes that maintain species diversity will help design plans for preservation of species, communities, and ecosystems. Land managers must know which processes increase or decrease species diversity on their lands before they can make informed decisions about the types of actions that should be taken to best preserve them or restore habitat. Understanding which processes are necessary to preserve maximum diversity can lead to more informed decisions about assigning protection priorities to various areas in scenarios involving limited monetary resources. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

Fire is a natural part of most forest ecosystems in the western United States. Forest managers utilize fuel reduction projects to lessen fire severity, often without considering potential negative ecological consequences of non-native plant species introductions. The establishment and spread of non-native species following fire may significantly alter the ability of native plant communities to recover. Factors such as fire severity, resource distribution, and soil alterations all play a role in where and how non-native plant species may establish in burned areas. This doctoral dissertation research project addresses the invasion potential across the forest/grassland ecotone following low severity fire by studying microsite changes from pre- to post-burn conditions. The two research questions of the proposed study are: 1) Are there significant differences in the biotic (vegetation attributes) and abiotic (soil moisture, temperature, nutrients) microsite conditions across the ponderosa pine/grassland ecotone of the Colorado Front Range following low severity fire, which would make the site more invasible? 2) In the post-fire landscape, following low severity fire, how are non-native plant species colonization patterns affected by the microsite patterns? Data collected from several research sites along this forest/grassland ecotone over the course of several seasons prior to prescribed burning provide information on variation in soil moisture and temperature and vegetation structure during times of near normal conditions. Following prescribed burning, the changes in microsite patterns may vary across the ecotone and impact the availability of sites for native and non-native species colonization. Many of the studies of fire effects to date address this question at coarser scales. This research applies a more fine scale approach to determine the mechanisms involved in the spread of non-natives into the forested landscape from a grassland matrix.

This research will contribute to the understanding of the importance of microsite conditions and their effects on the potential for non-native plant species to move across ecotones after low severity fire. The use of this information will contribute not only to the overall understanding of the degree to which a recently burned area is susceptible to invasion by non-native species at the fine scale, but will also contribute to the integration of these fine scale mechanisms into landscape level responses to disturbance. This research will provide fundamental information that is necessary to support present and future forest management decisions in the western United States, in regards to prescribed fires and non-native species control. As a Doctoral Dissertation Research Improvement award, this award will provide support to enable a promising student to establish a strong independent research career.