• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 45
  • 17
  • 7
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 101
  • 101
  • 29
  • 25
  • 21
  • 20
  • 17
  • 14
  • 14
  • 13
  • 13
  • 12
  • 12
  • 11
  • 11
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Predicting Woodland Bird Response to Livestock Grazing

Martin, Tara Gentle Unknown Date (has links)
Livestock grazing impacts more land than any other use. Yet knowledge of grazing impacts on native fauna is scarce. This thesis takes a predictive approach to investigating the effects of livestock grazing on Australian woodland birds, employing some novel methodological approaches and experimental designs. These include methods of analysis to handle zero-inflated data and the application of Bayesian statistics to analyse predictions based on expert opinion. The experimental designs have enabled impacts of grazing to be separated from the frequently confounding effects of other disturbances, and to consider the effect of grazing on habitat condition in the context of different surrounding land uses. A distinguishing feature of many datasets is their tendency to contain a large proportion of zero values. It can be difficult to extract ecological relationships from these datasets if we do not consider how these zeros arose and how to model them. Recent developments in modelling zero-inflated data are tested with the aim of making such methods more accessible to mainstream ecology. Through practical examples, we demonstrate how not accounting for zero-inflation can reduce our ability to detect relationships in ecological data and at worst lead to incorrect inference. The impact of grazing on birds was first examined through the elicitation of a priori predictions from 20 Australian ecologists. This expert knowledge was then used to inform a statistical model using Bayesian methods. The addition of expert data through priors in our model strengthened results under at least one grazing level for all but one bird species examined. This study highlights that in fields where there is extensive expert knowledge, yet little published data, the use of expert information as priors for ecological models is a cost effective way of making more confident predictions about the effect of management on biodiversity. A second set of a priori predictions were formulated using a mechanistic approach. Habitat structure is a major determinant of bird species diversity and livestock grazing is one mechanism by which structure is altered. Using available information on the vegetation strata utilised by each species for foraging and the strata most affected by grazing, predictions of the impact of grazing on each bird species were formulated. We found that foraging height preference was a good predictor of species’ susceptibility to grazing. This approach is a starting point for more complex predictive models, and avoids the circularity of post hoc interpretation of impact data. The confounding of grazing with tree clearing was addressed by examining the impact of pastoral management on birds in sub-tropical grassy eucalypt woodland in Southeast Queensland, where land management practices have made it possible to disentangle these effects. Changes in bird species indices were recorded across woodland and riparian habitats with and without trees across three levels of grazing, replicated over space and time. Tree removal had a dramatic influence on 78% of the bird fauna. 65% of species responded significantly to changes in grazing level and the abundance of 42% of species varied significantly with habitat, level of clearing and grazing. The impact of grazing on birds was most severe in riparian habitat. Finally, the extent to which landscape context and local habitat characteristics influence bird assemblages of riparian habitats in grazed landscapes is addressed. Over 80% of bird species responded significantly to changes in local riparian habitat characteristics regardless of context, while over 50% of species were significantly influenced by landscape context. The influence of landscape context increased as the surrounding landuse became more intensive. These results suggest that it is not enough to conserve riparian habitats alone but conservation and restoration plans must consider landscape context. The ability to predict which bird species will be most affected by grazing will facilitate the transformation of this industry into one that is both profitable and ecologically sustainable. Results from this thesis suggest that any level of commercial grazing is detrimental to some woodland birds. Habitats with high levels of grazing support a species-poor bird assemblage dominated by birds that are increasing nationally. However, provided trees are not cleared and landscape context is not intensively used, a rich and abundant bird fauna can coexist with moderate levels of grazing, including iconic woodland birds which are declining elsewhere in Australia.
22

ROLE OF FIRE AND PLANT-DERIVED SMOKE IN SEED GERMINATION AND SEEDLING EMERGENCE IN FESCUE PRAIRIE

2015 December 1900 (has links)
Fire, a natural disturbance, regulates species composition in Fescue Prairie. However, little is known about the contribution of different regeneration strategies in altering species composition after burning in Fescue Prairie. The present study was conducted to determine if and how fire and associated fire cues regulate species composition in Fescue Prairie through their effects on seedling recruitment. The effects of fire and various fire cues, including smoke, ash, and smoke plus ash on seedlings emerging in the field and/or from litter, 0-1 cm, and 1-5 cm layers of the soil seed banks were therefore examined. These studies were complimented by a study of testing effects of smoke originated from different plant materials on seed germination and seedling growth of species from Fescue Prairie. Chemical analyses were also conducted to determine whether different active compounds existed in smoke made from different materials, which in turn affect germination and seedling growth differently. Burning increased densities, richness, and diversity of seedlings emerging in the field. This was possibly attributed to direct fire cues of burning. Seedling densities of native forbs and non-native graminoids emerging from the soil seed bank were increased and decreased by burning, respectively. Ash and smoke plus ash increased density of forbs emerging from the soil seed bank. Species composition of seedlings emerging in the field and from the soil seed bank was altered by burning. Complex responses were observed for the effects of smoke on seedling establishment, which depended on the type and dilution of smoke solutions, as well as germination conditions. Smoke solutions partly substituted light requirement for germination of Artemisia ludoviciana. Germination of Cirsium arvense and Conyza canadensis only responded to smoke solutions at 25/15°C, but not at 10/0 °C. Diluted smoke solutions increased radical length of Artemisia ludoviciana. Karrikinolide (KAR1) was in the smoke made from prairie hay and wheat straw, but not in that made from alfalfa. This is the first report that different active compounds existed in smoke made from different materials. Highly concentrated smoke solutions made from alfalfa increased germination and radical length of Conyza canadensis, while the same concentrated smoke solutions made from prairie hay and wheat straw reduced germination of Conyza canadensis at 25/15 °C in darkness. Priming in KAR1 solutions and active fractions obtained from prairie hay and/or wheat straw increased germination of Artemisia frigida, Artemisia ludoviciana, and Conyza canadensis at certain germination conditions. In summary, fire and direct fire cues, smoke and ash specifically, stimulated recruitment of some species, especially early seral species and native forbs, contributing to potential changes in species composition of the Fescue Prairie. Different compounds existed in smoke solutions made from alfalfa as compared with those from prairie hay and wheat straw, showing different effects on seed germination and seedling growth. KAR1, the most important active compound discovered in smoke, was present in the smoke made from prairie hay and wheat straw, but was not in that made from alfalfa.
23

Dinâmica sazonal e espacial da comunidade de aves de um ambiente semiárido

Silva, Clarisse Caroline de Oliveira e 31 March 2016 (has links)
Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-03-28T20:22:19Z No. of bitstreams: 1 ClarisseCOS_DISSERT.pdf: 4409173 bytes, checksum: ddfe0c2c141a91a0fc8fb6c388923cb2 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T14:41:28Z (GMT) No. of bitstreams: 1 ClarisseCOS_DISSERT.pdf: 4409173 bytes, checksum: ddfe0c2c141a91a0fc8fb6c388923cb2 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T15:07:13Z (GMT) No. of bitstreams: 1 ClarisseCOS_DISSERT.pdf: 4409173 bytes, checksum: ddfe0c2c141a91a0fc8fb6c388923cb2 (MD5) / Made available in DSpace on 2017-04-13T15:08:37Z (GMT). No. of bitstreams: 1 ClarisseCOS_DISSERT.pdf: 4409173 bytes, checksum: ddfe0c2c141a91a0fc8fb6c388923cb2 (MD5) Previous issue date: 2016-03-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The semi-arid tropical environments exhibit high seasonality, including wide variation in the rainfall amount throughout the year. This triggers fluctuations in environmental conditions and the resources availability and therefore should influence the variation in species richness of birds in time and space. In this study we used capturerecapture data from birds to evaluate issues such as: (1) species richness vary seasonally with a high change rate, as in other semi-arid; (2) species richness variation is mainly due to the temporary departure of species in the wet-dry transition and return on dry-wet cycle; and (3) the environment with a lower degree of disturbance is associated with less seasonal variation in species composition and richness than higher disturbed environment. The study was carried out in the Caatinga (semi-arid Neotropical) over three years (2012-2015), with two annual capture season (dry and wet) in two environments (natural and disturbed). We analyzed the data through MARK program, with Robust design models and CJS to estimate parameters of the communities’ dynamics (estimates of species input and output (permanent and temporary), species richness and richness change rate). The analysis showed that seasonality and environment are factors decisive for the temporary emigration, the largest output of species in the wet-dry transition and greater input in the dry-wet. We estimate that approximately 40% of the species left the sampling area after the rainy season and 85% of the outside species entered the area before the rainy season. The average of species richness estimated was 33.4 in the dry season and 53.2 in the rainy season. The change rate of species richness varied from 0.6 in the wet-dry transition to 1.5 in the dry-wet, being similar between environments. The estimates of permanent output of species varied from one to three species per transition, while permanent input varied between four and six species per season. Our results showed that the seasonal variation of water regime, as well as the phytophysiognomy change were important factors in determining the community dynamics / Os ambientes semiáridos tropicais apresentam alta sazonalidade climática, incluindo grande variação pluviométrica ao longo do ano. Isto desencadeia flutuações nas condições ambientais e na disponibilidade de recursos e, consequentemente, deve influenciar a variação na riqueza de espécies de aves no espaço e tempo. Neste estudo utilizamos dados de captura-recaptura de aves para avaliar questões como: (1) a riqueza de espécies varia sazonalmente e a taxa de mudança é alta, assim como em outros semiáridos; (2) a variação na riqueza é consequência principalmente da saída temporária de espécies na transição chuva-seca e retorno na seca-chuva; e (3) o ambiente com menor grau de perturbação está associado à menor variação sazonal em riqueza e composição de espécies do que o mais perturbado. O estudo ocorreu na Caatinga (semiárido neotropical), ao longo de três anos (09/2012 a 08/2015), com dois períodos anuais de captura (seca e chuva) em dois ambientes (natural e perturbado). Analisamos os dados no programa Mark, com modelos do tipo Desenho Robusto e CJS visando estimar parâmetros da dinâmica de comunidades (estimativas de entrada e saída espécies (permanente e temporária), riqueza de espécies e taxa de mudança na riqueza). As análises mostraram que a sazonalidade e o tipo de ambiente são fatores determinantes para a emigração temporária, sendo a maior saída de espécies na transição chuva-seca e maior entrada na seca-chuva. Estimamos que aproximadamente 40% das espécies saíram da área de amostragem após o período chuvoso e 85% das espécies que estavam fora, entraram na área antes do período chuvoso. A riqueza de espécies estimada foi em média de 33,4 na época seca e 53,2 na época de chuva. A taxa de mudança na riqueza de espécies variou entre 0,6 na transição chuva-seca e 1,5 na seca-chuva, sendo semelhantes entre ambientes. As estimativas de saída permanente de espécies variou de uma a três espécies por transição, enquanto que de entradas permanentes variou entre quatro e seis espécies por período. Os nossos resultados mostraram que a variação sazonal do regime hídrico, assim como, a variação na fitofisionomia foram fatores importantes na determinação da dinâmica da comunidade / 2017-03-28
24

Determinantes de comunidades de formigas em restinga / Determinants of ant communities in Restinga

Cardoso, Danon Clemes 23 July 2009 (has links)
Made available in DSpace on 2015-03-26T13:30:25Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1105450 bytes, checksum: 163c50636e0eaab0ec624fc7342a1a43 (MD5) Previous issue date: 2009-07-23 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The Brazilian coast presents approximately 9,200 kilometers, which 5.000 km of them are occupied by the Restinga ecosystems. This ecosystem is a set of vegetation formations that develop in sandy plains dating from the Quaternary, within the Atlantic Forest domain. The plant species that occur in Restinga have high plasticity, presenting adaptations for their development under the influence of various biotic and abiotic factors such as drought stress, wind, topography and salinity. These factors influence the occurrence and distribution of plant communities in the Restinga, and similarly, should influence the distribution and diversity of animals. The aim of this dissertation was to test the assumption that the species richness of ants increases with distance from the ocean, as well as the following hypotheses: (1) ant species richness increases with plant species richness, which in turn increases with distance from the sea, (2) ant species richness is proportional to soil cover by plants and litter; (3) ant species richness increases with soil organic matter concentration, (4) ant species richness decreases with soil salinity, and (5) the species richness of ants responds positively to spatial heterogeneity of the environment. Moreover, we tested a second assumption that the distinct Restinga phytophysiognomies have different ant species composition. The ants were sampled in herbaceous and shrubby Restinga of the Morro dos Conventos in Araranguá (SC) using pitfall traps. Sixty-five pitfall traps were placed 10 meters away from each other in transects disposed from the ocean to the continent. At each sampling point, were collected the following explanatory variables: plant species richness, percentage of vegetation cover and litter, concentration of organic matter and salt in soil. In total, we collected 71 species of ants. Our results have confirmed both assumptions. Ant species richness was related to distance from the sea, plant species richness, soil cover by plant and litter. Moreover, we observed that different vegetation types within Restinga have specific communities of ants, where habitats near or with similar environmental conditions had higher similarity among them. These results indicate that the vegetation and environmental factors affected by them are the main factors determining the ant species richness and composition in Restinga. / O litoral brasileiro apresenta aproximadamente 9.200 quilômetros de extensão, das quais 5.000 km são ocupados por ecossistema de Restinga. Este ecossistema é um conjunto de formações vegetacionais que se desenvolvem em dunas e cordões arenosos do período Quaternário dentro do domínio da Floresta Atlântica. As espécies de plantas que ocorrem em Restinga possuem elevada plasticidade, apresentando adaptações para seu desenvolvimento sob influência de vários fatores abióticos como: estresse hídrico, ventos, topografia e salinidade. Tais fatores condicionam a ocorrência e a distribuição das comunidades vegetais em ambientes de Restinga, e similarmente, devem influenciar a distribuição e a diversidade da fauna animal. O presente estudo teve por objetivo testar o pressuposto de que a riqueza de espécies de formigas aumenta com o aumento da distância em que se encontram em relação ao oceano e as seguintes hipóteses explicativas: (1) a riqueza de espécies de formigas aumenta com a riqueza de espécies de plantas, que por sua vez aumenta com a distância do mar; (2) a riqueza de espécies de formigas é diretamente proporcional a cobertura do solo por plantas e serapilheira; (3) a riqueza de espécies de formigas aumenta com a concentração de matéria orgânica no solo; (4) a riqueza de espécies de formigas diminui com o aumento da concentração de sal no solo; e (5) a riqueza de espécies de formigas responde positivamente à heterogeneidade espacial do ambiente. Além disso, nós testamos um segundo pressuposto de que diferentes fitofisionomias de Restinga possuem composição de espécies de formigas específicas. As coletas de formigas foram realizadas na Restinga herbáceo-arbustiva do Morro dos Conventos, em Araranguá (SC) utilizando armadilhas de solo. Foram instaladas 65 armadilhas distantes 10 metros entre si, em dois transectos do oceano para o continente. Em cada ponto amostral, foram coletadas as seguintes variáveis explicativas: riqueza de espécies de plantas, percentagem de cobertura vegetal e de serapilheira, concentração de matéria orgânica e sal no solo. No total, foram coletadas 71 espécies de formigas. Os resultados obtidos permitiram confirmar nossos dois pressupostos. Observamos que a riqueza de espécies de formigas está positivamente relacionada com a distância em que se encontram do mar, com a riqueza de espécies de plantas, cobertura vegetal e cobertura por serapilheira do solo. Além disso, observamos que diferentes fitofisionomias dentro da Restinga apresentam comunidades de formigas específicas, e que em geral, habitats próximos ou com condições ambientais semelhantes apresentaram maior similaridade quanto à composição de espécies. Esses resultados sugerem que a vegetação e os fatores ambientais condicionados por ela, podem ser os principais fatores determinando a riqueza e composição de espécies de formigas em Restinga.
25

ASSESSING SEED BANK CONTRIBUTION TO LANDWARD EXPANSION OF COASTAL WETLAND COMMUNITIES AND RESPONSES TO FIRE AND TRANSLOCATION ALONG COENOCLINE

Hacker, Molly 01 May 2018 (has links)
Land loss is a major threat to coastal wetlands of the northern Gulf of Mexico due to the impacts and interactions of sea level rise, regional subsidence, and anthropogenic changes to land cover and sediment supply. Here, coastlines are rapidly converting to open water due to an inability of coastal systems to keep pace with sea level rise via marsh migration due to barriers in the landscape, including dense shrub encroachment from fire suppression of inland communities. Fire may play an important role in promoting resiliency by in two ways, first by reducing or removing woody encroachment, allowing species to be released to migrate inland, second, by promoting primary productivity of herbaceous vegetation, which in turn, may promote vertical expansion. Where elimination of barriers is not possible (i.e., roads, industry and infrastructure), assisted migration of coastal communities landward (via translocation) may be also be a viable solution to bypass these barriers. This research is focused on the potential contribution of seed banks in landward migration of species, the role that fire plays in compositional change, and how seed banks compare to translocated communities when introduced into new environments. Here, seed bank dynamics were assessed and compared to aboveground vegetation of naturally regenerating and reciprocally transplanted (translocated) sods through time, with and without fire. The objectives of this study were to examine: 1) richness and abundance of species in the seed bank among vegetation zones of the coastal transition gradient; 2) effect of fire on expression of the soil seed bank; 3) emergence patterns and the degree of mixing/dispersion of dominant species within the seed bank among zones; 4) similarity of species composition of seed bank to that of the standing vegetation, pre- and post-fire; 5) similarity of species composition of the seed bank to that of the inter-zonally transplanted sods, with and without fire; and 6) fire behaviors through fuel loads and fire temperatures across zones. Results demonstrate the effect of zone on the composition, species richness and propagule density of the seed bank, and differences in similarity of the composition of the seed bank and standing vegetation. Fire did not appear to affect the composition of the seed bank. Ordinations indicate that seed bank communities are more widely distributed than standing vegetation assemblages. An overlap of communities was observed in each zone of the seed bank except salt marsh. Reciprocally transplanted sods that were burned prior to translocation were more similar to seed bank composition than no-fire transplants. Similarity, related to habitat preference, was most retained when sods were transplanted one zone away, and when transplanted upslope. A series of Procrustes analyses was conducted for combinations of seed bank treatments to standing vegetation of naturally regenerated and reciprocally transplanted plots of varying survey periods. Results showed that seed bank composition was most similar to the standing vegetation of the same survey period, and least similar for no-fire seed bank to transplanted plots surveyed 15 months after transplant. That the no-fire transplant plots were less similar to seed bank than burned transplant plot indicate that similarity between the seed bank and standing vegetation may be retained with fire. Comparisons of the Jaccard’s Similarity Coefficient of transplanted plot to seed bank with and without fire showed that overall, plots that had been burned were more similar to their source plots than those that had not been burned, across all zones. This study provides insight to zonation patterns of the seed bank across the coastal coenocline of the northern Gulf of Mexico, and compositional similarity of the seed bank to both naturally generated and reciprocally transplanted propagules, in order to understand the how these communities respond to sea level rise, how they may be managed with fire, and how plant species respond to conditions across zone, thereby the potential contribution of the seed bank to landward migration and the promotion of resiliency of coastal communities through facilitation of lateral migration in response sea level rise.
26

Vliv pastvy na diverzitu mechorostů společenstev suchých trávníků v CHKO Český kras / Effect of grazing on bryophytes diversity of dry grasslands in the PLA Český kras

TENČÍK, Aleš January 2018 (has links)
Dry grassland are among the most endangered plant communities mainly due to the overgrowth of a number of localities. That is why from the beginning of the 21st century pasture with mixed herds of sheep and goats is restored on the most valuable dry grassland sites in the Bohemian Karst as the way of maintaining these habitats. Concurrently, research sites each 1x1 m in size were set up at four pastured localities, and were paired with control sites equipped with a fence for the research of grazing effect on vegetation. The main aim of this work was to evaluate the effect of grazing on the diversity of bryophytes at the forty pairs of the above-mentioned areas in three types of calcareous dry grasslands. In addition to the inventory of bryophytes, data on the most important abiotic and biotic factors of the environment were recorded on individual sites. The total number of bryophyte species found at the research sites is 46. 37 species were found at the grazing areas and the same number was at the fenced areas. Minimal differences in the number of species of grazed and unspoilt areas were also found in the comparison of individual localities. The grazing effect was shown up more significantly on species richness in the comparison of individual types of communities, especially in broad-leaved dry grassland (T3.4). There was a 40% increase in the number of species on grazing areas. The environmental factors have a positive effect on the species abundance mainly due to the higher slope of the terrain and the correlation with the larger occurrence of the stones, the smaller coverage of the herb layer and the litter. These conditions prevailed in areas with rock outcrop vegetation with Festuca pallens (T3.1), where the largest species richness of bryophytes in area was found. In the obtained data, the influence of grazing on the species composition of bryophytes on grazed and unspoilt areas was also assessed with the statistical methods and the Sörensen test of beta-diversity. The results show that grazing significantly influences the species composition towards open grassland and supports the growth of the bryophytes T3.1 plant community at the expense of the T3.4 plant community
27

Funkce horských luk při různých způsobech jejich obhospodařování / Functioning of Mountain Meadows under Different Management Impacts

MAŠKOVÁ, Zuzana January 2008 (has links)
Influence of different management practices on the mountain meadows communities and possibilities of their maintenance in the National Park, Protected Landscape Area and Biosphere Reserve of Šumava are discussed. The aim of the study was to compare the effect of mulching of grassland vegetation with those of traditional mowing or leaving a grassland fallow. The results of a ten-year field experiment are presented - the changes of plant biomass, plant community structure and physical properties of the soil A horizon. Acceptable possibilities of mulching as an alternative technique for the maintenance of secondary grassland in the Bohemian Forest are proposed on the basis of data obtained during the experiment.
28

Assembléias de formigas do Parque Estadual do Itacolomi (MG) e relações intra e interespecíficas entre espécies dominantes

Espírito Santo, Nádia Barbosa do 22 February 2008 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-04T19:09:14Z No. of bitstreams: 1 nadiabarbosadoespiritosanto.pdf: 614691 bytes, checksum: 350d5e203557de825054d6f6775e0856 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-06T10:43:56Z (GMT) No. of bitstreams: 1 nadiabarbosadoespiritosanto.pdf: 614691 bytes, checksum: 350d5e203557de825054d6f6775e0856 (MD5) / Made available in DSpace on 2017-04-06T10:43:57Z (GMT). No. of bitstreams: 1 nadiabarbosadoespiritosanto.pdf: 614691 bytes, checksum: 350d5e203557de825054d6f6775e0856 (MD5) Previous issue date: 2008-02-22 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Formigas arborícolas geralmente possuem um forte comportamento territorialista, defendendo agressivamente seu local de forrageamento ou área ao redor de seu ninho contra indivíduos de outras colônias. Dessa forma, as espécies mais agressivas e com maior distribuição, que são consideradas as dominantes, forçam a estruturação da assembléia de formigas em forma de mosaicos tridimensionais nas copas das árvores. O objetivo do trabalho foi investigar o indicativo da existência de um mosaico através da distribuição, riqueza e abundância de formigas em três estágios sucessionais distintos de uma floresta montana tropical. Visando obter uma investigação mais detalhada sobre espécies dominantes, a fim de observar mecanismos formadores do mosaico, foram avaliados, através de experimentos em campo e em laboratório, o grau de agressividade e dominância de Camponotus (Myrmothrix) rufipes (Fabricius), uma espécie dominante no Parque Estadual do Itacolomi. Posteriormente avaliou-se também o comportamento desta espécie perante uma potencial competidora, Camponotus (Myrmepomis) sericeiventris (Guérin – Menéville), que possui tamanho corporal parecido, utiliza os mesmos tipos de alimentos e locais de nidificação. O solo apresentou maior riqueza e abundância de espécies de formigas que o dossel e sub-bosque, independente do estágio sucessional. Já os diferentes estágios sucessionais não apresentaram diferença quanto à riqueza e abundância de formigas, mas a composição de espécies foi significativamente diferente entre as áreas, sugerindo que há espécies típicas de cada estágio sucessional. As espécies consideradas dominantes foram Camponotus rufipes e Myrmelachista sp.1. Com relação aos experimentos de campo e laboratório, observou-se que C. rufipes e C. sericeiventris apresentaram em seu repertório comportamental muitas xv exibições agressivas sendo capazes de afugentar outras formigas. No entanto, mostram-se tolerantes a uma série de outras espécies, que podem coexistir em densidades menores, com tamanhos corporais diferentes e ainda utilizando estratégias de forrageamento diferentes. Camponotus sericeiventris apresentou indícios da capacidade de excluir C. rufipes da sua área de forrageio. / Arboreal ants usually show a strong territolialist behavior, defending aggressively their foraging sites or the area surrounding their nest against individuals of other colonies. Thereby, the most aggressive ants with larger distribution, which may be considered dominants, defines the ant assemblage structure by shaping species distributions into threedimensional mosaics in the forest canopies. The objective of the work was to investigate the indicative of the mosaic existence through the distribution, richness and abundance of ants in three different successional stages of a montane tropical forests. In oerder to obtain a more detailed investigation about dominant species, and so identify mosaic building mechanisms, the aggressiveness degree and dominance of Camponotus (Myrmothrix) rufipes (Fabricius), a dominant species in Parque Estadual do Itacolomi was evaluated through experiments in field and in laboratory. Later, it was also evaluated this species behavior in the face of a potential competitor, Camponotus (Myrmepomis) sericeiventris (Guérin – Menéville), which has a similar body size, eats the same types of food and uses the same nesting sites. Species richness and abundance were significantly higher in the soil than in the canopy and understorey, regardless successional stage. On the other hand, those parameters did not vary significantly between the successional stages, although species composition did, thus suggesting that there are typical species for each successional stage. The species considered dominant were Camponotus rufipes and Myrmelachista sp.1. Concerning the field experiments and laboratory, it was observed that the species C. rufipes and C. sericeiventris presented many aggressive exhibitions in their behavioral repertoire, being able to drive away other ants. However, they seem to be tolerant of many other species that can coexist in smaller densities, with different body sizes and even using different foraging strategies. xvii Camponotus sericeiventris showed indications about the capacity of excluding C. rufipes from their forage area.
29

Post-fire species composition and regeneration of understory vegetation in a boreal forest in central Sweden

Hassel, Anna January 2018 (has links)
Post-fire survival, composition and regeneration of understory species in the boreal forest have shown to be affected by several factors, where consumption of the organic soil layer together with altered soil properties play important parts. There has however also been shown that the pre-fire site characteristics affect the post-fire understory vegetation. This study aimed to investigate the effects of fire and pre-fire site characteristics on understory regeneration and composition at a local scale in a boreal forest. Classification of species richness of the understory species together with measurements of biomass in terms of leaf area index (LAI) and normalized difference vegetation index (NDVI) were performed in a Pinus sylvestris forest in the Gärsjön catchment area, three years after a stand-replacing wildfire. Data of site index, fire severity on soil and moss, fire severity on shrubs, stand age, and remaining humus depth were also used. A total of 36 species of vascular plants (10 forbs, 14 graminoids, 5 dwarf shrubs, 2 ferns, 1 shrub and 4 trees) together with 3 species of bryophytes were recorded in the area. The study revealed that understory species composition was explained by remaining humus depth and site index. The regeneration of the understory was affected differently, where LAI was affected by site index, and NDVI was connected to both site index and fire severity on soil and moss. LAI and NDVI differed in their sensitivity in capturing differences among plant species, where higher values of LAI were associated to species such as E. sylvaticum, P. erecta, C. arundinacea and J. conglomeratus, while NDVI was related to both the ground and field layer, with high values associated to a high abundance of C. canescens and C. ovalis. According to my result, it can be concluded that NDVI is a more appropriate measure of post-fire re-establishment and recovery of understory vegetation in the boreal forest.
30

The Ecological Succession of Mosquitoes Inhabiting Waste Tires in a Subtropical Swamp and Upland Forest in Central West Florida

Dinh, Emily Thuong Nguyen 01 February 2016 (has links)
Literature has not yet seen a contribution involving the description of successional patterns of mosquitoes (Diptera: Culicidae) inhabiting discarded automobile tires in sylvan areas nor an investigation into the macro- and micro-environmental factors that may influence the seasonal shifts in species composition and abundance in that respective habitat. Waste tires in undeveloped forests are a hazard to human and animal health because they can support a population of vector mosquitoes. Locating productive waste tire mosquito habitats is problematic in wooded areas but is crucial for diminishing pathogen transfer in areas where humans have regular access to forests because of possible zoonotic disease transmission. The intentions of this study were 1) to describe the ecological succession patterns of mosquitoes in waste tires in a subtropical wetland and upland forest and 2) to create a database on which regressive geo-spatiotemporal models locating unidentified productive waste tires in sylvan zones can be built. The entomological research conducted here did not confirm the hypothesis that Aedes albopictus (Skuse) would be the dominant species in all the tires at all the study sites. There appeared to be seasonal trends in mosquito production despite the general constant warmth and rainfall levels year-round in subtropical Tampa, Florida. However, the findings of this research indicates that climatic conditions alone do not sufficiently explain spatiotemporal variation in mosquito populations. Rather, the effects of weather are heterogeneous at the microcosmic level, which has a more direct impact on ecological interactions between the different species found here and their abiotic environment.

Page generated in 0.5073 seconds