Thesis (PhD (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / Dispersal plays an essential role in determining the distribution of populations of species, especially species expanding their ranges. Two disciplines are concerned with gaining understanding of spread of species, namely restoration ecology and invasion biology. Con- ceptual understanding of dispersal, its mechanisms and its management is essential to both disciplines. Nevertheless, the disciplines have quite opposite objectives: in restoration ecol- ogy, spread of indigenous species into transformed landscapes is promoted, while invasion biology aims to prevent the (further) spread of alien species into pristine or restored habi- tats. Despite these two opposite objectives of facilitating spread and preventing spread of their respective target species, these disciplines have essentially the same requirements in terms of information needed for restoration. In this thesis, I will present two modelling studies—one looking at the impact of two different seed-feeding alien control agents on the spread of Hakea sericea, the other investigating the recolonisation by Dicerothamnus rhinocerotis of an old field dominated by Cynodon dactylon. Based on these studies, I will draw conclusions for the management in each case. In a second step, I will compare these two seemingly-different studies and draw conclusions on how these two disciplines can learn from each other, and how conclusions drawn and management recommendations developed for the one discipline can be translated for the other. The invasion biology study concluded that seed-feeding biocontrol agents do have a considerable impact on the velocity of the spread of the target species. In addition, management recommendations included the possibility of substituting seed-feeding biocontrol agents with an increased fire frequency where the negative impact on natural vegetation, on the site invaded by the target species, is acceptable. The restoration study concluded that the main impact on the velocity of spread, and the speed of the return of the shrub species onto the old fields, is the availability of micro-sites. A sensitivity analysis showed the even a slight change from 1% to 2% increases the velocity and pattern of spread dramatically. The other parameters playing an important role are the mean rate of establishment and the time span between

There is growing awareness about the value of preserving and restoring floral-rich habitats for the benefit of pollinators, especially native bees. The increasing demand for native plants in pollinator habitat restoration and other ecological landscaping applications, combined with the desire for more robust and predictable plant habits, have led to the selection and breeding of native cultivars. Yet, little is known about how these cultivated varieties differ from the native species in their ability to attract and support pollinators. I compared flower visitation by all insect pollinators to 12 native herbaceous plant species and 14 native cultivars in a replicated field experiment at two sites over two years. I classified insect pollinators during visual field observations into seven taxonomic and functional groups. I found seven native species to be visited significantly more frequently by all insect pollinators (combined) than their cultivars, four were visited equally, and one native cultivar was visited more frequently than the native species. Bees (both native and non-native) and moths/butterflies exhibited similar preferences, whereas flies showed no preference between the native species and the native cultivar. Our study shows that many insect pollinators prefer to forage on native species over cultivated varieties of the native species, but not always, and not exclusively. Some native cultivars may be comparable substitions for native species in pollinator habitat restoration projects, but all cultivars should be evaluated on an individual basis. Plant selection is integral to the value and success of pollinator habitat restorations, yet there is little consistency and overlap in pollinator planting recommendations and very little empirical data to support plant choice. Non peer-reviewed pollinator plant lists are widely available and are often region-specific, but they are typically based on anecdotal rather than empirical data and lack in specificity. To help close the gap between anecdotal and empirical data, and between practice and research, I reviewed the published literature on plant selection for pollinator habitat restoration. I explicitly reviewed and compared the value of native plant species, near-natives, non-natives and native cultivars. From there, I identified gaps in the literature that are most needed in practice and recommended basic strategies for practitioners to navigate plant lists and choose the best plants for a site's success.

A mineração causa graves impactos ambientais, sendo o solo um dos componentes do meio físico mais vulnerável durante a exploração das jazidas. O ciclo do N tem sido bastante estudado, entretanto, pouco se sabe sobre a trajetória de recuperação da sua ciclagem em florestas restauradas após a mineração de bauxita. O objetivo foi investigar de que maneira o processo de restauração florestal em área minerada para extração de bauxita interfere na ciclagem do nitrogênio no sistema solo-planta-serapilheira. Para tanto, foram mensurados nesses compartimentos a disponibilidade de N, suas razões N:P e a abundância natural do isótopo estável de N (?15N). As hipóteses propostas foram: \"A restauração florestal, conduzida pelo uso de técnicas de engenharia ecológica, plantio de espécies arbóreas nativas e adição de topsoil é suficiente para aumentar a disponibilidade de N no ecossistema\", e \"Áreas mineradas em processo de restauração florestal, com o avanço da sucessão ecológica, podem desenvolver uma dinâmica na ciclagem de N próxima ao ecossistema de referência, apresentando valores de concentrações desse nutriente nos seus compartimentos (solo-planta-serapilheira) semelhantes a esse ecossistema\". O estudo foi conduzido no município de Poços de Caldas/MG, sendo considerados três tratamentos: floresta nativa, área restaurada há aproximadamente 06 anos e área restaurada há 24 anos, com seis repetições para cada. O delineamento utilizado foi o inteiramente casualizado, no esquema de parcelas subdivididas. O ciclo do N não foi recuperado nas florestas em restauração. Entretanto, há uma tendência de a ciclagem desse elemento assemelhar-se a da floresta nativa, conforme o avanço da sucessão ecológica. Deste modo, ambas as hipóteses propostas foram confirmadas, sendo a utilização de técnicas de engenharia ecológica, plantio adensado de espécies nativas e a adição de topsoil, os principais responsáveis pelos resultados / Mining causes serious environmental impacts and the soil is the most vulnerable component of the physical environment during the exploitation of deposits. The N cycle has been extensively studied, however, little is known about the recovery trend of its cycling in forests restored after bauxite mining. The aim was to investigate how the forest restoration process in bauxite mined area interferes in the nitrogen cycling in the soil-plant-litter system. Therefore, we measured the availability of N, the N:P ratios and the natural abundance of N stable isotope (?15N) in these compartments. The hypotheses proposed were: \"Forest restoration, driven by the use of ecological engineering techniques, planting of native tree species and addition of topsoil is sufficient to increase the availability of N in the ecosystem\", and \"Mined areas in forest restoration process, with the advancement of ecological succession, can develop a dynamics in N cycling resembling to that of the reference ecosystem, presenting values of concentrations of this nutrient in their compartments (soil-plant-litter) similar to this ecosystem. The study was conducted in Poços de Caldas county, Minas Gerais state, Brazil, considering three treatments: native forest, area restored for approximately 06 years and a restored area for 24 years with six repetitions for each. The design was completely randomized in a split plot. The N cycle has not been recovered in forest restoration. However, there is a tendency of N cycling resemble that of the native forest as the advancement of ecological succession. Thus, both hypotheses were confirmed, and the use of ecological engineering techniques, dense planting of native species and the addition of topsoil, were the main responsible for these results

A restauração ecológica visa a recuperação de ecossistemas que foram degradados, assegurando o seu restabelecimento estrutural e funcional. Porém, avaliar a funcionalidade do ecossistema ainda é um desafio, e vem sendo foco de trabalhos científicos a fim de desenvolver metodologias aplicáveis. Investigar as redes de interações ecológicas é uma forma adequada para avaliar a funcionalidade do ecossistema. As redes de interações são utilizadas na avaliação de habitats e já evidenciaram alterações na estrutura da comunidade que não foram detectadas pelas métricas tradicionais de riqueza, abundância e composição. Os macrofungos podem ser indicadores relevantes, pois realizam a decomposição e ciclagem de nutrientes e servem de alimento para diversos grupos de organismos, dentre eles os Coleoptera, que também podem utilizar a estrutura fúngica para nidificação. Este trabalho teve por finalidade construir redes tróficas formadas pela interação entre besouros fungívoros (Coleoptera) e macrofungos (Polyporales e Hymenochaetales) a fim de testar a aplicabilidade de redes ecológicas para avaliar a restauração quando comparadas às métricas tradicionais de abundância, riqueza e composição das espécies. O estudo se realizou em duas áreas sobre restauração florestal comparados às áreas de referência pareadas. A primeira área está em restauração há oito anos e a segunda há dez anos, sendo que até o momento, somente a segunda área teve sucesso na restauração da comunidade de plantas. No total, coletamos 512 macrofungos, representando 87 espécies, mas somente 181 indivíduos de 36 espécies apresentaram interações com besouros. Destes, foram obtidos 11.414 besouros de 53 espécies. Em ambas as áreas, as métricas de descritores de comunidade e também as métricas de redes não diferiram entre os tratamentos, indicando que a estrutura e também a funcionalidade das comunidades de macrofungos e besouros fungívoros está sendo recuperada nas áreas em restauração. Apesar de não haver diferença na composição de espécies, a espécie rara Falsocis brasiliensis e alguns exemplares da família Erotylidae somente foram encontradas em áreas de referência. Os processos de restauração diferiram qualitativamente entre as áreas, como podemos perceber através das interações realizadas. As áreas de restauração de dez anos estão mais próximas às áreas de referência, pois foram deixados troncos de madeira que serviram de substrato para os macrofungos, principalmente para o Ganoderma australe e suas interações, encontrado em árvores mortas da floresta de referência de ambas as áreas. Enquanto que as áreas de restauração de oito anos apresentaram pouco substrato lenhoso e baixa umidade, onde Pycnoporus sanguineous predominou em abundância de basidiomas e suas interações em relação à floresta de referência. / Ecological restoration aims to recover degraded ecosystems, ensuring both structural and functional restoration. Assessing ecosystem functionality is still a challenge, and current work is focusing on the development methods. Investigating networks of ecological interactions is a potential tool to assess ecosystem functionality. Interaction networks are used in the assessment of habitat change and have already evidenced differences in community structure that were not detected by the traditional metrics of richness, abundance and composition. Macrofungi are especially relevant indicators, due to their function in decomposition and nutrient cycling in the ecosystem, and as they serve as food source for several groups of organisms, among them the Coleoptera, which can also use the fungal structure for nesting. Here we aimed at building trophic networks formed by the interaction between fungivorous beetles (Coleoptera) and macrofungi (Polyporales and Hymenochaetales), in order to test the applicability of ecological networks for the evaluation of restoration when compared to the traditional metrics of abundance, richness and species composition through the macrofungi-beetles system. Research was conducted in two areas under forest restoration, compared to paired reference areas. The first area is under restoration process for 8 years and the second for 10 years, and in the second area the restoration success has been achieved based on plant community evaluation. During the study, we collected 512 macrofungi individuals, representing 87 species, but only 181 specimens from 36 species showed interactions with beetles. A total of 11,414 beetles from 53 species were obtained. For both areas, traditional community descriptors did not differ between treatments, nor did network metrics, indicating that the structure and also the functionality of the communities of fungivorous beetles and macrofungi are being successfully recovered in restoration areas. Although there is no difference in species composition, the rare species Falsocis brasiliensis and some specimens of the Erotylidae were found only in reference areas. The processes of restoration differ qualitatively between areas, as we can perceive through the interactions. The ten year-long restoration areas are more similar to the reference areas, due to the presence of wood logs that served as substrate for the macrofungus, mainly Ganoderma australe and its associated beetles, occurring on dead trees found in the both reference forest areas. On the other hand, the eight year-long restoration area had less woody substrate, composed mostly of thin branches, and less humidity, where Pycnoporus sanguineous predominated in basidiome abundance and their interactions compared to the reference forest.

A crescente degradação de ecossistemas tornam necessários inúmeros esforços para recuperá-los. A ecologia da restauração é uma ciência que vem crescendo, buscando suporte e apoiando as bases da ecologia teórica. O papel das áreas restauradas na manutenção da biodiversidade é ainda incerto, mas há consenso que estas devem restabelecer os atributos ecológicos. A escolha de bons indicadores ecológicos é crucial para avaliar a evolução dessas áreas. A análise da vegetação é um bom indicador, por ser possível utilizar métodos simples de execução e apresentar respostas rápidas às condições (bióticas e abióticas), fornecendo, por exemplo, informação dos agentes dispersores na área e das características das espécies que compõe a comunidade. Através dessas informações é possível inferir se a área é visitada por animais e como ocorre o processo sucessional. A presente pesquisa consistiu na análise da vegetação de florestas em processo de restauração com idades diferentes. Foram escolhidos plantios com oito e 12 anos e um remanescente florestal. Em cada área foram alocadas 30 parcelas de 10 x 10 m, todos os indivíduos arbustivo-arbóreos (estrato arbóreo) com diâmetro a altura do peito maior ou igual a 10 cm foram amostrados, identificados e tiveram sua altura estimada. O estrato regenerante foi registrado por parcelas de 2 x 10 m alocadas no interior das parcelas (10 x 10m) onde foram amostrados e identificados indivíduos com altura maior ou igual a 50 cm e diâmetro a altura do peito menor que 10 cm. As espécies encontradas foram categorizadas em grupos funcionais (síndromes de dispersão e classes de sucessão) e origem (nativa e exótica). Para o estrato arbóreo e para o regenerante, o ecossistema de referência apresentou maior densidade, riqueza e diversidade. Diferente do ecossistema de referência, os plantios apresentaram muitos indivíduos de espécies de origem exótica, e não apresentaram muitos indivíduos das classes sucessionais clímax. Diante dos resultados talvez sejam necessárias ações de manejo adaptativo, com retirada das espécies que tem potencial invasor e enriquecimento funcional para que a evolução das áreas não seja comprometida. A avaliação da vegetação mostrou-se bom indicativo no estudo da evolução das áreas em processo de restauração. / The growing degradation of ecosystems makes it necessary the adoption of various efforts in order to restore it. Restoring ecology is a science that has been growing, seeking support and providing support to the foundations of theoretical ecology. The role of the restored areas in the maintenance of biodiversity is still uncertain; however there is consensus that they should restore the ecological attributes. The choice of good ecological indicators is crucial in order to assess the evolution of those areas. The analysis of the vegetation is a good indicator, because it enables the use of simple execution methods and because it also presents fast answers to the conditions (biotic and abiotic) providing for example, information about the dispersing agents of the area as well as the characteristics of the species that makes up the community. Through this information, it is possible to infer if the area is visited by animals and how the succession process happens. The current research consists of the analysis of the vegetation of forests in restoring process with different ages. Plantings were chosen between 8 to 12 years and a remnant forest. In each area 30 plots of 10 X 10 m were allocated, all tree species with diameter and breast height higher or the same as 10 cm were shown, identified and had their height estimated. The regenerative component was recorded in plots of 2 X 10 m allocated in the interior of the plots where they were sampled and identified the individuals with height higher than 50 cm and diameter and breast height lower than 10 cm. The species found were categorized in functional groups (dispersion syndrome and restoring guilds). The highest values of density, richness and diversity of arboreal and regeneration layers were found in the reference ecosystem. The forests in process of restoration considered in this work, unlike the reference ecosystem, presented numerous individuous of exotic species, and did not present many late-successional individuous. Results suggest that performing adaptative management actions, such as invasive species removal and functional enrichment, may be necessary for the appropriate evolution of the concerned areas. Evaluation of the vegetation was considered a good indicator to study the development of areas in process of restoration.

A Mata Atlântica é considerada mundialmente um dos biomas prioritários para conservação, devido à elevada riqueza de sua biodiversidade. A preservação da vegetação natural deve estar associada à restauração florestal, de modo que se possa assegurar a continuidade desta rica biota. No Brasil, grande parte dos projetos de restauração florestal realizados até agora tem se preocupado apenas em buscar diversidade florística, contemplando uma baixa diversidade genética em sua implantação, o que têm criado muitos problemas relativos à viabilidade biológica de suas comunidades. O presente trabalho se propôs a realizar um estudo comparando a diversidade genética (utilizando marcadores SSR, cpSSR e AFLP) da espécie arbórea Piptadenia gonoacantha (Mart.) J. F. Macbr. em duas áreas em processo de restauração florestal e dois remanescentes naturais de floresta estacional semidecidual da Mata Atlântica do estado de São Paulo, Brasil. A partir da biblioteca genômica construída, foram obtidos 12 locos SSR. A heterozigosidade média esperada no equilíbrio de Hardy Weinberg (HE = 0,494) foi maior do que a heterozigosidade observada (HO = 0,251) em todas as populações, indicando taxa relativamente alta de endogamia (FIS = 0,342). Os resultados obtidos com os locos cpSSR mostraram, ao todo, 16 haplótipos, dos quais 10 foram encontrados nos remanescentes de floresta nativa e oito nas áreas restauradas. As análises realizadas com os marcadores AFLP resultaram em 303 marcas polimórficas. Uma estrutura genética muito forte foi encontrada relativa às quatro populações, valores de FST foram 0,283, 0,83 e 0,177 em SSR, cpSSR e AFLP, respectivamente. Dez locos de AFLP que podem estar sujeitos a seleção foram encontrados. As análises de agrupamento delimitam claramente as amostras das quarto populações, evidenciando que não existe fluxo gênico significativo entre elas. P. gonoacantha apresentou auto correlação espacial nas quatro populações. Os três tipos de marcadores detectaram maior diversidade genética nos remanescentes naturais do que nas áreas restauradas. Apesar da menor diversidade apresentada pelas áreas restauradas em comparação com as áreas de remanescentes florestais, o tamanho efetivo populacional estimado para essas áreas permite a manutenção da variabilidade existente a curto prazo. As informações obtidas poderão servir para o manejo sustentado desta espécie, bem como para o planejamento de sua conservação. / The Atlantic Forest is considered one of the world biomes for conservation priority due to the high richness of its biodiversity. The preservation of natural vegetation should be associated to forest restoration, so that the continuity of this rich biota can be ensured. Recent studies and practices of reforestation in degraded areas have taken population genetics as a great ally. Several of the forest restoration projects carried out in Brazil so far has been concerned just with floristic diversity, contemplating low genetic diversity. This fact has created many problems related to the biological viability of their communities. The present project proposes to carry out a study on the diversity genetic structure of the arboreal species Piptadenia gonoacantha (Mart.) J. F. Macbr. In this study, we used six chloroplast simple-sequence repeats (cpSSRs), AFLP markers and the construction of an enriched SSR DNA library to investigate the genetic diversity of P. gonoacantha. This species was evaluated in two areas that are under forest restoration process and compared then with two natural remnants of semideciduous seasonal Atlantic Forest. 12 SSR markers were obtained and the average HO=0.251 was smaller than the average HE=0.494, evidencing a heterozygote deficit (average FIS= 0.342). The samples shows a strong structure with a significant differentiation. FST values were 0.283, 0.83 and 0.177 for SSR, cpSSR and AFLP respectively. The cluster analyzes clearly demarcating the samples of the four populations. cpSSR markers showed 16 haplotypes, ten of them were found in the remaining native forest and eight in the restored areas. Ten AFLP outliers loci were found. The three types of markers detected a higher genetic diversity in natural remnant than in restored areas. Despite the lower diversity presented by the restored areas compared with areas of forest remaining, the effective population size estimated for these areas allows the maintenance of existing variability. The results of this study prove that there is greater genetic diversity in the remaining natural areas than in the areas undergoing a reforestation process. The information obtained may be used for the sustainable management of this species, as well as for conservation planning.

Woody encroachment upon grasslands is a global trend that is cause for concern. In the Lampasas Cut Plain of Texas, Ashe juniper is the dominant woody invasive species. Grassland restoration is dependent upon proper seedbed preparation and seedling establishment. Shearing and bulldozing are common methods of juniper removal. Three hypotheses were tested in this experiment. The first was that bulldozing and shearing results in similar seedbed preparations. The second was that electrical conductivity (ECa) models soil moisture storage heterogeneity across a landscape. The third hypothesis tested was that bulldozing and shearing result in similar seedling establishment. Eighteen plots were selected and three treatments were applied: 1) shearing, 2) dozing, and 3) control. After clearing with both juniper removal methods, the levels of soil disturbance and vegetation regrowth were measured. Point measures were used to describe soil surface disturbance, and at each point, presence and size of ground cover and surface depressions were recorded. After germination, when the plants were large enough to identify, vegetation was sampled at 20-24 locations in each plot. At each sample location a quadrat was placed on the transect, and total herbaceous, grass, forb, rock, litter, and bare soil cover were recorded in cover classes. All species were identified, seeded species were enumerated, and in the second vegetation sample, dominant species were assigned a cover class. There was considerable variation between plots for all parameters measured. Bulldozing created a greater number of depressions in the soil than shearing. It also had a higher percent of large depressions. There was no difference in ground cover change between treatments except in the case of the largest litter category. ECa was effective in modeling soil moisture storage patterns and had a lower coefficient of variation than manual soil depth measurements. There was no difference between sheared and dozed plots for any of the vegetation establishment parameters, but control plots had lower establishment in most categories. Overall, there was little difference between the two treatments in seedbed preparation and seedling establishment. The cost of shearing was 80% of the cost of dozing, which made it more desirable in this scenario.

Forests are the dominant terrestrial ecosystem in Ontario and were once widespread throughout much of eastern North America; in southern Ontario, forest cover has declined from 90% to approximately 17% in the past 200 years. Conversion of the surrounding landscape to urban and agricultural land uses creates edge effects which increase the impact of forest cover loss and threaten ecological integrity. Other impacts on forest ecological integrity include incompatible human activities, a generally inhospitable landscape matrix, and microenvironment changes, including those from chemical pollution and heat island effects. Coupled with direct degradation from human activities like free-riding, the altered forest microenvironment can facilitate increased invasion by opportunistic and competitive plant species, e.g. Alliaria petiolata (Brassicaceae). This tends to be worse in urban areas because of greater visitation that creates soil compaction, trampling, and more vectors to introduce the seeds of invasive species. Active management is often necessary in areas which have been degraded. Ecological restoration represents an important active management tool for urban forest protected area managers. The ecological restoration of the forest understory in altered and threatened habitats represents an important aspect of forest restoration. For this study, I tested the effectiveness of an ecological restoration using a multi-species assemblage approach with three native understory species to restore the herbaceous layer in Natchez Hills, an Environmentally Sensitive Policy Area in Kitchener, Ontario. The ecological restoration site was degraded and this reduced native plant species in the forest understory. The species selected, Caulophyllum giganteum (Farwell) Loconte & W.H. Blackwell (Berberidaceae), Podophyllum peltatum Linnaeus (Berberidaceae) and Maianthemum racemosum subsp. racemosum (Linneaus) Link (Asparagaceae), are widespread throughout eastern North America, and were selected for use in this study because of their persistence and relative abundance in Natchez Hills ESPA. Adult transplants were planted into 2 metre by 2 metre quadrats in different densities and shoot populations were monitored for two field seasons to determine if density played a role in early ecological restoration success. The methodology I designed for the ecological restoration was as practical as possible, given the real world financial and logistical constraints faced by many urban forest managers. Statistical analysis using repeated measures multivariate analysis of variance showed aerial shoot density did not have a significant effect on early restoration success rates (p > 0.05). However, there was a significant increase in restored species. Caulophyllum giganteum and Podophyllum peltatum shoot populations increased by over 97% at the ecological restoration site one year after transplanting. Maianthemum racemosum subsp. racemosum shoot populations increased by 51% at the site. For comparison, another study in the same forest reported early ecological restoration rates of 92% to 100% for herbaceous understory species, including C. giganteum and P. peltatum. Other North American studies using transplanted perennial herbaceous material reported average survival rates of 16.6% two years after planting (varying from 1.25% to 51.4% using eight herbaceous species in the Boston area), to 91% one year after restoration (varying from 42.1% to 100% using 19 herbaceous species of the deciduous forest in the Midwest). In instances where protected areas are degraded, active management and ecological restoration are often necessary tools. This ecological restoration demonstrated that the native herbaceous species used in this study are suitable for use in early ecological restorations in maple beech upland forests in the City of Kitchener. Using a practical and cost-effective methodology this ecological restoration experiment showed that it is possible to implement urban restoration of the forest understory in degraded areas, and to achieve success in early ecological restoration using native herbaceous forest understory species.

Woody encroachment upon grasslands is a global trend that is cause for concern. In the Lampasas Cut Plain of Texas, Ashe juniper is the dominant woody invasive species. Grassland restoration is dependent upon proper seedbed preparation and seedling establishment. Shearing and bulldozing are common methods of juniper removal. Three hypotheses were tested in this experiment. The first was that bulldozing and shearing results in similar seedbed preparations. The second was that electrical conductivity (ECa) models soil moisture storage heterogeneity across a landscape. The third hypothesis tested was that bulldozing and shearing result in similar seedling establishment. Eighteen plots were selected and three treatments were applied: 1) shearing, 2) dozing, and 3) control. After clearing with both juniper removal methods, the levels of soil disturbance and vegetation regrowth were measured. Point measures were used to describe soil surface disturbance, and at each point, presence and size of ground cover and surface depressions were recorded. After germination, when the plants were large enough to identify, vegetation was sampled at 20-24 locations in each plot. At each sample location a quadrat was placed on the transect, and total herbaceous, grass, forb, rock, litter, and bare soil cover were recorded in cover classes. All species were identified, seeded species were enumerated, and in the second vegetation sample, dominant species were assigned a cover class. There was considerable variation between plots for all parameters measured. Bulldozing created a greater number of depressions in the soil than shearing. It also had a higher percent of large depressions. There was no difference in ground cover change between treatments except in the case of the largest litter category. ECa was effective in modeling soil moisture storage patterns and had a lower coefficient of variation than manual soil depth measurements. There was no difference between sheared and dozed plots for any of the vegetation establishment parameters, but control plots had lower establishment in most categories. Overall, there was little difference between the two treatments in seedbed preparation and seedling establishment. The cost of shearing was 80% of the cost of dozing, which made it more desirable in this scenario.

Buffelgrass (Pennisetum ciliare) is a perennial bunchgrass native to Africa that has invaded ecologically intact areas of the Sonoran Desert in southern Arizona. It threatens many native plant species by means of competitive exclusion as well as increased fire frequency and intensity. Since the 1990s, efforts have been underway in southern Arizona to control buffelgrass using manual removal. A problem with this method is that the resulting bare, disturbed soil provides a favorable environment for buffelgrass seed germination. This study examined whether thatch composed of uprooted buffelgrass parent plants spread over disturbed areas reduces the density of progeny seedlings. A secondary goal was to determine whether light attenuation and/or autoallelopathy were major factors involved in the effect of thatch on buffelgrass seedling density. The effect of light attenuation on seedling density was tested in containers in the field and in the greenhouse. The propensity of thatch to produce autoallelopathic chemicals was tested in the greenhouse. Field plots with thatch had 1.9 buffelgrass seedlings/m² which was significantly fewer (p= 0.03) than the 2.9 seedlings/ m² in plots without thatch. These results suggest that the placement of thatch over areas disturbed during manual treatment of dense stands of buffelgrass will increase the efficiency of follow-up control of buffelgrass progeny seedlings in these areas. Results of the field container study suggest that light attenuation does not play a significant role (p= 0.39) in the reduction of seedling density by thatch, whereas those of the greenhouse shade treatment study indicated that light attenuation is a significant factor (p= 0.004). However, because percent germination was very low in the field container study, those results may be of little value compared to the greenhouse shade treatment study results which indicate that light attenuation is a mechanism by which thatch reduces buffelgrass seedling emergence. Chemicals leached from decomposed buffelgrass thatch did not have a significant effect (p= 0.09) on buffelgrass seedling density. Only the combination of thatch and leached chemicals significantly reduced (p= 0.014) seedling density. Thatch may also increase the activity of other factors that could reduce seedling density such as pathogens, and predators of seeds and seedlings.