Digital Commons Network^™

Flower Visitation In Relation To Pollen And Nectar Nutrition: Implications For Pollinator Habitat And Conservation, Megan E. Leach

Electronic Theses and Dissertations

Pollination of both wild and crop plants is at a crossroads; honey bee populations are experiencing losses at a higher rate than ever before, and some native bee species are declining in abundance to the point of being listed as endangered species. A few examples of these threats include pesticide exposure, habitat loss, and climate change. In response to bee population declines, conservation efforts have been initiated to increase habitat quality for bees by planting pollinator reservoirs or gardens. Plants provide nutrition to bees in the form of pollen and nectar. Several studies have shown links between higher nutritional quality …

Band-Sowing With Hoeing For Weed Management In Organic Grains, Margaret R. Mccollough

Electronic Theses and Dissertations

Weeds remain the foremost production challenge for organic small grain growers in the Northeastern United States. Instead of sowing crops in narrow, single-line rows, band-sowing with inter-band hoeing is a cropping strategy that could provide superior weed control. In theory, band-sowing suppresses weeds in the intra-band zone by improving the spatial arrangement of the crop from that of typical rows to a more uniform pattern within the planted bands, maximizing interspecific and reducing intraspecific competition. Weeds in the inter-band zone are controlled by cultivating with aggressive sweeps; tine harrowing can target weeds in the intra- and inter-band zones.

Chapter one …

Optimizing Fertilizer And Compost Rates In Organic Reduced Till Agriculture, Nicholas W. Rowley

Electronic Theses and Dissertations

Interest in reduced tillage systems has been increasing and advanced by a need to practice agriculture in a sustainable way to limit environmental degradation. The focus on preserving soil integrity has become commonplace in all scales of agriculture. Recently trends in agricultural production have given rise to numerous small farms centered on local and sustainable farming. In turn, this has led to a growing desire to implement conservation tillage into these systems.

In 2015 and 2016 a collaborative effort between the University of Maine at the Maine Agricultural and Forestry Experiment Station: Highmoor Farm and Cornell University at the Homer …

Reducing Tillage In Small-Scale Permanent Bed Organic Vegetable Production Systems, Jeremiah D. Vallotton

Electronic Theses and Dissertations

The response of field-grown vegetable crops to reduced tillage and mulching in permanent beds was evaluated through measuring crop yields, weed pressure, earthworm counts, and soil basal respiration. Two vegetable crops (“Bush Delicata” squash and “Farao” cabbage) were started in April and May of 2016 and 2017 respectively, transplanted in late June, and harvested on 15-Sep-2016 and 25-Aug-2017. Fruit number and weight of squash, and head weight and feeding damage of cabbage were measured. These results suggest that intensive tillage (8” rototill every year) can be successfully reduced to alternating years of shallow (2”) rototilling and a less intensive form …

Big Data For Small Parks: Examining Regional Vegetation Patterns To Assess The Current Condition And Vulnerability Of Eastern National Parks To Climate Change, Kathryn M. Miller

Electronic Theses and Dissertations

The United States National Park Service mission is to preserve natural and cultural resources unimpaired for future generations. Given climate change, the paradigm of restoring natural resources to their pre-European settlement condition is no longer appropriate or achievable management. Instead, we must promote resilience and plan for adaptation. This approach poses many challenges, including knowledge gaps about the current condition of park ecosystems including wetlands, and lack of information about the matrix surrounding parks, which will strongly influence park ecosystem response to climate change. My dissertation research focused on filling these knowledge gaps to provide much needed information to managers …

Advancing Development Of Porphyra Umbilicalis As A Red Algal Model System And Aquaculture Crop, Charlotte Royer

Electronic Theses and Dissertations

The marine red alga Porphyra umbilicalis (Rhodophyta, Bangiaceae) has ideal traits to allow it to become a model organism, including its economic value, reproduction in the northwestern Atlantic through asexual neutral spores (NS), and availability of fully-sequenced nuclear and organelle genomes. Research on the bacterial component of the Porphyra microbiome is ongoing. To advance model organism development and support microbial studies, data on natural reproductive trends and early embryonic development are needed, along with a system for genetic transformation, and ways of visualizing the attached microbial community. To meet these needs, two years of phenological data were analyzed, revealing seasonal …

Chemical And Non-Chemical Control Of Potato Pink Rot, Xuemei (Missi) Zhang

Electronic Theses and Dissertations

Pink rot of potato (Solanum tuberosum) is a widespread soilborne disease that causes significant losses in the field and storage. It is caused by Phytophthora erythroseptica (Pethybr.), an oomycete pathogen that produces sexual spores that can survive in soil for years. The management of pink rot mainly relies on chemical control. However, the most effective chemical in pink rot control, mefenoxam, is losing its efficacy owing to the development of mefenoxam resistance in P. erythroseptica. To evaluate alternative fungicides (including chemical and biological fungicides) to mefenoxam in pink rot control, two greenhouse experiments and three field trials …

Propagation And Container Production Of The Amelanchier Spicata Complex, Gregory J. Melcher

Electronic Theses and Dissertations

Amelanchier is a genus in the Rosaceae containing shrubs and trees indigenous to North America that possess traits valued by the horticulture industry. Amelanchier spicata (dwarf serviceberry), a heterogeneous complex of hybrids indigenous to eastern North America, has agricultural and ornamental merit with notable characteristics. White blossoms emerge in early spring, edible pomes ripen in the summer, and vibrant, orange foliage occurs in the fall. I investigated phenological and physiological factors influencing adventitious rooting of stem cuttings, the effects of nitrogen source on the development of seedlings grown in container culture, and phenotypic variation among seedlings of A. spicata from …

The Enhancement Of Wild Bees (Hymenoptera: Apoidea) For Pollination Security, Eric M. Venturini

Electronic Theses and Dissertations

The acreage of pollinator-dependent crops continues to expand across the globe. Simultaneously, honey bee hives – an annually rented commodity that growers rely on – are more expensive every year and in some cases, scarce. In response, pollinator-dependent growers seek alternative pollinators. One approach is installing bee pasture on farms, a strategy that enables systems-based farmers to become in-situ farm-scale habitat managers. This thesis first presents a review of the literature on bee pasture plantings and provides a brief overview of some methods for assessing their impacts on the pollinator community. There are three major gaps in current bee pasture …

Application Of Spatial Modeling Tools To Predict Native Bee Abundance In Maine's Lowbush Blueberries, Shannon J. Chapin

Electronic Theses and Dissertations

Non-native honeybees historically have been used to pollinate many crops throughout the United States, however, recent population declines have revealed the need for a more sustainable pollination plan. Native bees are a natural resource that can play an important role in pollination. I used spatial modeling tools to evaluate relationships between landscape factors and native bee abundance, with a focus on the wild native bees that pollinate Maine’s lowbush blueberries. I applied the InVEST Crop Pollination ecosystem spatial modeling tool, which predicts pollinator abundance based on available floral resources and nesting habitat, to the Downeast Maine region. The InVEST model …

Sources Of Variability In Agronomic Weed Seed Predation: Time, Space, Habitat, And Hyperpredation, Sonja K. Birthisel

Electronic Theses and Dissertations

Weed seed predation is an ecosystem service that benefits farmers by decreasing seedbank inputs, thereby reducing weed pressure in subsequent growing seasons. Seed predation can be considerable, but is highly variable. Sources of variability may include time, space, habitat, and trophic interactions such as hyperpredation. Two experiments were conducted to measure the impacts of these sources of variability on weed seed predation rates in Maine mixed vegetable agroecosystems.

Chapter One of this thesis describes a series of landscape-level field experiments conducted to quantify the effects of time, space, and habitat on seed predation rates. Seed assays, with and without vertebrate …

A Characterization Of Maine Blueberry Growers In 2010, Anya Rose

Electronic Theses and Dissertations

A survey was sent to 343 lowbush blueberry growers in Maine with a response rate of 29%. Growers were asked questions about their management practices, pesticide use, priorities, decision-making influences, and beliefs about pesticide safety. Respondents categorized themselves into one of four categories: Integrated Pest Management (IPM), Conventional, Organic, and No-Spray. Analyses were conducted to examine factors that were linked to these four categories. A major goal of this study was to determine differences and similarities between growers of different management styles, and to define each category by the practices and beliefs of its members. Toxicity ratings were also calculated …

Assessing The Biological Condition Of Maine Streams And Rivers Using Benthic Algal Communities, Thomas John Danielson

Electronic Theses and Dissertations

The purpose of this study was to test and develop algal methods of evaluating the condition of Maine streams and rivers. The primary objective was to develop a statistical model to predict attainment of Maine's aquatic life criteria for water quality classes A, B, and C. I collected 298 samples of algae on rocks from 193 locations across the state. The major pattern in species composition related to conversion of forests to urban, residential, and agricultural land uses. I calculated preferred environmental conditions of 236 algal taxa for 1) concentrations of nitrogen, phosphorus, and dissolved ions in the water, 2) …

Genetic Diversity, Micro Propagation, And Cold Hardiness Of Ilex Glabra (L.) A. Gray, Youping Sun

Electronic Theses and Dissertations

Ilex glabra (L.) A.Gray (inkberry) is a native evergreen shrub with dark green foliage and compact habit. This shrub has gained popularity in the northern landscapes of the United States and more nursery growers would like to produce it. To better understand genetic relationships among inkberry cultivars and breed cold-hardy cultivars for northern nursery growers and landscape specialists, the following projects were conducted. A group of 48 inkberry accessions and two other Ilex species (Ilex crenata Thunb. and I. mutchagara Makino) were studied using amplified fragment length polymorphism (AFLP) markers. A total of 229 markers between 50 and 500 base …

Light-Related Photosynthetic Gene Expression And Enzyme Activity In The Heterokont Alga Vaucheria Litorea And Its Symbiotic Partner The Sacoglossan Mollusc Elysia Chlorotica, Kara M. Soule

Electronic Theses and Dissertations

Photosynthesis is comprised of tightly coupled reactions and therefore requires strict matrices of regulation, particularly involving alterations in gene expression and enzyme activity within the nucleus and plastid. Extensive research has been carried out on these light-regulated mechanisms in plants and green algae, however, much less is known in the red algal lineage, including heterokonts. The goal of this study was to investigate the influence of light on photosynthetic gene expression and select enzyme activity in the heterokont alga Vaucheria litorea and its symbiotic partner Elysia chlorotica, a photosynthetic sacoglossan mollusc (sea slug). Elysia chlorotica harbors V. litorea plastids …

Influence Of Silvicultural Treatment, Site Characteristics, And Land Use History On Native And Nonnative Forest Understory Plant Composition On The Penobscot Experimental Forest In Maine, Elizabeth Bryce

Electronic Theses and Dissertations

This study investigates forest understory plant diversity and composition in managed and unmanaged stands within the context of a long-term silvicultural experiment in the Acadian Forest of Maine. I examined the effects of silvicultural intensity and past land use on understory plant species diversity and composition. Silvicultural treatments include three variants of the selection system, three variants of the shelterwood system, modified and fixed diameter-limit cutting, and an unregulated harvest. Two types of unmanaged stands were studied: a continuously forested natural area and secondary forest stands on old fields. Chapter 1 presents analysis of understory plant diversity and composition in …

Production Of Heuchera And Coleus, Katherine Fisher Garland

Electronic Theses and Dissertations

According to the USD A ERS, 2008 receipts from greenhouse and nursery sales ranked fourth among agricultural commodities in Maine and seventh in the nation. Greenhouse and nursery plant production relies on the availability of quality water for irrigation and, often involves the use of supplemental lighting to enhance the quality and growth of the plants being produced. Increasing energy costs and more frequent water shortages associated with changing demographics, water use legislation, and climate factors have inspired growers to consider more sustainable approaches to utilizing resources such as water and energy. Precise, crop-specific water and light recommendations are essential …

Methodology And Assessment Of The Susceptibility Of Potato Genotypes To Phytophthora Erythrosetpica Causal Organism Of Pink Rot, Erica Fitzpatrick-Peabody

Electronic Theses and Dissertations

Phytophthora erythroseptica Pethyb., causal organism of potato (Solanum tuberosum L.) pink rot is a soil-borne ubiquitous oomycete pathogen that can cause severe losses in both the field prior to harvest and during storage. The efficacy of the most effective fungicide, mefenoxam for control of P. erythroseptica is in jeopardy due to the widespread development of resistance in the US. Cultivar resistance may provide the best option for management of P. erythroseptica in the future. Recently published reports of cultivars susceptible to P. erythroseptica are based on evaluation techniques involving detached tubers and nontuber germplasm rather than field evaluations. Screening detached …

Crop/Livestock Integration Effects On Soil Quality, Crop Production, And Soil Nitrogen Dynamics, Ellen B. Mallory

Electronic Theses and Dissertations

Regional integration of potato and dairy farms has developed in Maine through arrangements where manure, feed, and sometimes land, are exchanged between neighboring farms. The effects of integration on soil quality, crop production, nitrogen (N) cycling, and N loss were investigated in field and laboratory studies of contrasting amended (manure, compost, green manure, and supplemental fertilizer) and nonamended (fertilizer only) soil management systems within 2-year potato (Solanum tuberosum L.) rotations in the Maine Potato Cropping Systems Project (MPEP). Additionally, soil quality of 48 integrated and nonintegrated Maine potato and dairy farm fields was assessed. The MPEP’s amended soil system enhanced …

Systematics Of The Lobulomycetales, A New Order Within The Chytridiomycota, David Rabern Simmons

Electronic Theses and Dissertations

Based on molecular phylogenetic analyses, the polyphyletic order Chytridiales, one of the four orders in the Chytridiomycota, contains several well-supported clades. One species, Chytriomyces angularis, however, does not group within the robust clades of the Chytridiales or any other chytrid order. The light-level morphology and zoospore ultrastructure of this aquatic species also differ from those of the type species of the genus Chytriomyces. I amassed nine additional pure culture isolates of soil-inhabiting chytrids with morphologies or rDNA sequences similar to C. angularis, including two isolates of C. poculatus, and studied the molecular phylogeny of these ten …

Myriophyllum Heterophyllum Michx. (Haloragaceae): Control And Vegetative Reproduction In Southwestern Maine, Jacolyn E. Bailey

Electronic Theses and Dissertations

Native to the southeastern United States, variable-leaf watermilfoil (Myriophyllum heterophyllum) is an invasive species in the Northeast and has been documented in Maine lakes for twenty years. Variable-leaf watermilfoil is targeted by the Maine Department of Environmental Protection as a species of grave concern as it has aggressively colonized twenty-six water bodies in Maine. This aquatic invasive plant grows in dense mats and outcompetes native vegetation. It is causing both ecological and economic disruption to Maine's lakes and ponds. The plants clog boat motors and deter people from swimming and other water related activities. Allofragmentation and autofragmentation occur …

The Impact Of The Strawberry Bud Weevil (Anthonomus Signatus) On Raspberry (Rubus Idaeus) In Maine, Christina S. Howard

Electronic Theses and Dissertations

The response of red raspberry (Rubus idaeus) plants to the loss of flower buds through the feeding and oviposition activities of the strawberry bud weevil (Anthonomus signatus), and the potential impact of this bud loss on fruit yield and quality, was studied through greenhouse and field experiments. With two cultivars of raspberry (‘Killarney’ and ‘Encore’) grown in a greenhouse, manual clipping of flower buds to simulate strawberry bud weevil (SBW) damage demonstrated that the impact on yield is dependent upon the number of buds lost, their position on the inflorescence and cultivar. In a 2006 greenhouse study, removal of primary …

Oxalate Production And Cation Translocation During Wood Biodegredation By Fungi, Jonathan S. Schilling

Electronic Theses and Dissertations

Wood biodegradation is primarily caused by Basidiomycetous white or brown rot fungi. White rot fungi are unique in degrading lignin, while brown rot fungi circumvent lignin to degrade holocellulose via iron-dependent oxidative chemistry. Both groups of fungi produce oxalate during wood metabolism, and oxalic acid secretion may promote wood decay by reducing pH, mobilizing iron, detoxifying copper, and immobilizing calcium. The function of oxalate during wood decay remains unclear, however, primarily due to difficulties in extracting bound oxalate and to inconsistencies among analytical techniques. This work aims to improve oxalate quantification during wood biodegradation and to better characterize fungal oxalate …

Re-Integrating Crops And Livestock In Maine: An Economic Analysis Of The Potential For And Profitability Of Integrated Agricultural Production, Aaron K. Hoshide

Electronic Theses and Dissertations

This thesis examines the profitability of and sustainability indicators for potato and dairy farms in Maine integrating crops and livestock in two different ways. The first is inter-farm coupling, where two or more specialized producers are close enough to exchange manure applications for crops used as livestock feed. Land base is shared between farmers. The second is where farms are on-farm integrated. Here crops and livestock are raised on the same farm and manure is applied to cash crops and livestock feed crops. Face-to-face interviews with Maine producers were used to construct integrated and non-integrated representative budgets. Assuming …

Dynamics Of Bee And Wasp Populations In Maine Lowbush Blueberry (Vaccinium Angustifolium), Joseph E. Karem

Electronic Theses and Dissertations

Conservation of natural enemies can be an effective form of pest management. If beneficial Hymenoptera, native to the area, can be protected and encouraged to multiply, the benefits of natural insect pest control might be realized. Hymenoptera as "natural enemies" as well as "pollinators" have been studied intensively in many agroecosystems worldwide. However, lowbush blueberry is not an ecosystem where ecology of Hymenoptera has been well studied. This thesis discusses two studies conducted in lowbush blueberry fields in Washington County, Maine in 1997 and 1998. In the first study, I investigated "towers" as a method for deploying insect traps along …

Age-Related Trends In Red Spruce Needle Anatomy And Their Relationship To Declining Productivity, Margaret H. Ward

Electronic Theses and Dissertations

Many species of trees undergo predictable age-related changes in foliar morphology and physiology. Age-related declines in photosynthetic rates, which may lead to decreases in productivity, have been described for numerous species. However, the physiological basis for these phenomena is unclear, as are linkages between agerelated trends in morphology/anatomy and physiology. Photosynthetic capacity in red spruce (Picea rubens Sarg.) may result from increased mesophyll resistance to CO2 uptake in older trees. Additional studies with other species imply that the foliage of older trees may have a lower ratio of photosynthetic to non-photosynthetic tissue and a larger proportion of xylem to leaf …

Revegetating Blackwoods Campground, Acadia National Park: Emphasis On Natural Regeneration Of Red Spruce And Balsam Fir, Cristin O'Brien

Electronic Theses and Dissertations

Blackwoods Campground in Acadia National Park has a declining vegetative understory, characterized by a lack of tree seedling recruitment and shrub populations. This project was embarked upon to identify limiting factors to tree seedling establishment and shrub survival. From these studies, management plans will be developed for revegetating the campground understory. To better understand the factors that inhibit successful seedling establishment, we investigated the effects of varying soil moisture levels on seed germination, seedling survival and seedling dry mass accumulation for red spruce and balsam fir. We also studied the effect of organic layer depth on seedling growth for both …

Development And Light Response Of Leaves Of Metasequoia And Close Relatives, Xiaochun Li

Electronic Theses and Dissertations

Metasequoia glyptostroboides is a useful nearest living relative (NLR) of the Eocene fossil Metasequoia. Research on modern Metasequoia might give us some clues about its fossil counterpart. During this study the leaf anatomy of Metasequoia, Glyptostrobus, Sequoia and Taxodium was investigated with light microscopy and transmission electron microscopy. Metasequoia exhibits several characteristics of typical sciaphilic plants, such as slightly arched outer cell walls in the adaxial epidermal cells, strongly arched outer cell walls in the abaxial epidermal cells, mesophyll composed of spongy cells, chloroplasts with well-developed grana not only in mesophyll cells but in both the adaxial and abaxial epidermis. …