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  • 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.
1

Demography of Cuban bird communities in the nonbreeding season : effects of forest type, resources, and hurricane /

Wallace, George E. January 1998 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.
2

Demography of Cuban bird communities in the nonbreeding season effects of forest type, resources, and hurricane /

Wallace, George E. January 1998 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.
3

Croissance et dynamique de l'épinette noire (Picea mariana (Mill.) B.S.P.) dans deux types écologiques de la forêt boréale québécoise, région écologique 6e-Coteaux de la rivière Nestaocano /

Bouchard, Marie-Hélène, January 2003 (has links)
Thèse (M.Ress.Renouv.) -- Université du Québec à Chicoutimi, 2003. / Bibliogr.: f. 36-38. Document électronique également accessible en format PDF. CaQCU
4

Utilizing the Landsat spectral-temporal domain for improved mapping and monitoring of ecosystem state and dynamics

Pasquarella, Valerie 07 December 2016 (has links)
Just as the carbon dioxide observations that form the Keeling curve revolutionized the study of the global carbon cycle, free and open access to all available Landsat imagery is fundamentally changing how the Landsat record is being used to study ecosystems and ecological dynamics. This dissertation advances the use of Landsat time series for visualization, classification, and detection of changes in terrestrial ecological processes. More specifically, it includes new examples of how complex ecological patterns manifest in time series of Landsat observations, as well as novel approaches for detecting and quantifying these patterns. Exploration of the complexity of spectral-temporal patterns in the Landsat record reveals both seasonal variability and longer-term trajectories difficult to characterize using conventional bi-temporal or even annual observations. These examples provide empirical evidence of hypothetical ecosystem response functions proposed by Kennedy et al. (2014). Quantifying observed seasonal and phenological differences in the spectral reflectance of Massachusetts’ forest communities by combining existing harmonic curve fitting and phenology detection algorithms produces stable feature sets that consistently out-performed more traditional approaches for detailed forest type classification. This study addresses the current lack of species-level forest data at Landsat resolutions, demonstrating the advantages of spectral-temporal features as classification inputs. Development of a targeted change detection method using transformations of time series data improves spatial and temporal information on the occurrence of flood events in landscapes actively modified by recovering North American beaver (Castor canadensis) populations. These results indicate the utility of the Landsat record for the study of species-habitat relationships, even in complex wetland environments. Overall, this dissertation confirms the value of the Landsat archive as a continuous record of terrestrial ecosystem state and dynamics. Given the global coverage of remote sensing datasets, the time series visualization and analysis approaches presented here can be extended to other areas. These approaches will also be improved by more frequent collection of moderate resolution imagery, as planned by the Landsat and Sentinel-2 programs. In the modern era of global environmental change, use of the Landsat spectral-temporal domain presents new and exciting opportunities for the long-term large-scale study of ecosystem extent, composition, condition, and change.
5

Comparison of Techniques for Estimation of Forest Soil Carbon

Amichev, Beyhan Y. 01 May 2003 (has links)
Soil organic carbon represents the largest constituent of the global C pool and carbon budgets are studied by researchers and modelers in C cycling, global climate change, and soil quality studies. Pedon and soil interpretation record databases are used with soil and ecological maps to estimate regional SOC even though these databases are rarely complete for surface litter and mineral subsurface horizons. The first main objective of the project is to improve the ability to produce soil organic carbon estimates from existing spatial soils datasets, such as STATSGO. All records in the STATSGO Layer table that were incomplete or appeared to be incorrectly filled with a null or zero value were considered invalid. Data sorting procedures and texture lookup tables were used to identify exiting correct (valid) data entries that were used to substitute invalid records. STATSGO soil property data were grouped by soil order, MLRA, layer number, and texture to produce replacement values for all invalid data used to calculate mass SOC. Grouping criteria was specific to each variable and was based on texture designations. The resulting filled and unfilled tables were used with procedures assuming Normal and Lognormal distribution of parameters in order to analyze variation of mass SOC estimates caused by using different computation techniques. We estimated mass SOC to 2 m in Maine and Minnesota using filled and unfilled STATSGO data tables. Up to 54% of the records in Maine and up to 80% of the records in Minnesota contained null or zero values (mostly in fields related to rock fragments) that were replaced. After filling, the database resulted in 1.5 times higher area-weighted SOC. SOC calculated using the Normal distribution assumption were 1.2 to 1.5 times higher than those using the Lognormal transformation. SOC maps using the filled tables had more logical geographic SOC distribution than those using unfilled tables. The USDA Forest Service collects and maintains detailed inventory data for the condition and trends of all forested lands in the United States. A wide range of researchers and landowners use the resulting Forest Inventory and Analysis (FIA) database for analytical and decision making tasks. FIA data is available to the public in transformed or aggregate format in order to ensure confidentiality of data suppliers. The second main objective of this project was to compute SOC (kg m-2) results by FIA forest type and forest type group for three depth categories (25 cm, 1 m, and 2 m) at a regional scale for the 48 contiguous United States. There were four sets of results derived from the filled STATSGO and FIA datasets for each depth class by region: (1) SOC computed by the Lognormal distribution approach for (1a) all soil orders, (1b) without Histosols; and (2) SOC computed by the Normal distribution approach for (2a) all soil orders, (2b) without Histosols. Two spatial forest cover datasets were relevant to this project, FIA and AVHRR. We investigated the effects of FIA inventory data masking for Maine and Minnesota, such as plot coordinates rounding to the nearest 100 arc-second, and the use of 1 km resolution satellite-derived forest cover classes from AVHRR data, on SOC estimates to 2 m by forest type group. SOC estimates by soil mapping unit were derived from fixed STATSGO database tables and were computed by the Lognormal distribution approach including all soil orders. The methods in this study can be used for a variety of ecological and resource inventory assessments and the automated procedures can be easily updated and improved for future uses. The procedures in this study point out areas that could benefit the most during future revisions of STATSGO. The resulting SOC maps are dynamic and can be rapidly redrawn using GIS whenever STATSGO spatial or tabular data undergo updating. Use of pedon data to define representative values for all properties in all STATSGO layers and correlation of STATSGO layers to soil horizons will lead to vast improvement of the STATSGO Layer table and promote its use for mass SOC estimation over large regions. / Master of Science
6

Epigėjinių žygių rūšinė sudėtis ir pasiskirstymas Pašilės girininkijos lapuočių medynuose / Species composition and dynamics of adult’s activity of ground beetles (Carabidae) in deciduous forest of Pašilė

Mulerčikas, Povilas 14 January 2009 (has links)
Darbo tikslas: nustatyti žygių rūšinę sudėtį ir pasiskirstymą Pašilės girininkijos lapuočių medynuose. Darbo objektas: Žygiai ( Coleoptera, Carabidae ) Pašilės girininkijos lapuočių medynuose. Darbo metodai: Stebėjimai buvo vykdomi 2007 metais Pašilės girininkijos lapuočių medynuose. Buvo išskirti penki miško tipai (jie skyrėsi augavietės sąlygomis), kuriuose buvo įtaisyta 50 Barberio žeminės gaudyklių. Kiekviename miško tipe nustatoma dominuojanti rūšis, rūšių individų skaičius, dominantų sezoninis aktyvumas, rūšinės įvairovės rodiklis, ekologinė ir zoogeografinė žygių charakteristika. Darbo uždaviniai: vykdyti žygių rinkimą Pašilės girininkijos lapuočių medynuose 2007m., apdoroti gautus duomenis, išanalizuoti žygių rūšinės sudėties ypatumus atskiruose miško tipuose. Darbo rezultatai: Tyrimo metu penkiuose miško tipuose buvo sugauta 11801 žygių, atpažintos 53 žygių rūšys, priklausančios 26 gentims. Tiriant žygių rūšis buvo nustatyta, kad viena jų (Calosoma inquisitor) įrašyta į Lietuvos Raudonąją knygą. Tiriant žygių gausumo sezoninę dinamiką išskirti du pakilimai: gegužės - birželio mėn. ir rugpjūčio mėn.. Žygių rūšinės įvairovės rodiklis atskiruose miško tipuose svyravo nuo 1,411 kiškiakopūstiniame ąžuolyne, iki 2,549 žibuokliniame – kiškiakopūstiniame uosyne. Atliekant tyrimo analizę išryškėjo tendencija, kad rūšinė įvairovė daugiausiai priklauso nuo dirvožemio drėgnumo ir derlingumo. Kuo derlingesnis ir drėgnesnis dirvožemis tuo didesnė žygių rūšinė įvairovė. Remiantis... [toliau žr. visą tekstą] / Object: to define specific composition and distribution of carabid beetles at different forest types at Aukštasis tyras Mire Reserve. Subject: Pašilės Methods: Observations were performed in 2007. At 5 forest types 50 Barber's ground traps were equipped. Dominating species, number of species individuals, seasonal activity of dominating species, index of species variety, ecological and zoographical characteristics of carabid beetles were ascertained at each forest type. Tasks: 1. To set the link between forest type and existing species composition of carabid beetles. 2. To study the subordination between richness of carabid beetles and forest type. Results: During the study at 5 forest types 11801 carabid beetles were caught, 53 species of carabid beetles which belong to 26 genera were recognized. During the study of carabid beetle species it was established that one of them (Calosoma inquisitor) was included into the Red Book of Lithuania. Studying the seasonal dynamics of carabid beetle richness two peaks were set: in may ¬June and August. Carabid beetle species variety at different forest types fluctuated from 1,411 at Oksalido – Quercetum to 2,549 at Hepatico-oksalido Fraxinetum. Making an evaluation of the study a tendency emphasised that species variety mostly depends on soil humidity and productivity. The more productive and humid the soil is, the bigger species variety of carrabid beetles is. Evaluating all collected carabid beetle species according to zoogeographical... [to full text]
7

Changes in trophic structure of decomposer communities with land use in Central European temperate forests

Klarner, Bernhard 20 January 2014 (has links)
No description available.
8

Forest Growth And Volume Estimation Using Machine Learning

Dahmén, Gustav, Strand, Erica January 2022 (has links)
Estimation of forest parameters using remote sensing information could streamline the forest industry from a time and economic perspective. This thesis utilizes object detection and semantic segmentation to detect and classify individual trees from images over 3D models reconstructed from satellite images. This thesis investigated two methods that showed different strengths in detecting and classifying trees in deciduous, evergreen, or mixed forests. These methods are not just valuable for forest inventory but can be greatly useful for telecommunication companies and in defense and intelligence applications. This thesis also presents methods for estimating tree volume and estimating tree growth in 3D models. The results from the methods show the potential to be used in forest management. Finally, this thesis shows several benefits of managing a digitalized forest, economically, environmentally, and socially.
9

The diversity of fungi in coniferous forests and mixed forests / Svampars diversitet i barr- och blandskog

Asplund, Ida January 2023 (has links)
The fungal domain has one of the highest biodiversities among eukaryotes and species within the domain fill important ecological roles, such as mutualistic mycorrhiza, decomposers, parasites and pathogens. The development of forest ecosystems and their related processes has not only been linked to fungal diversity but the composition and abundance of fungi benefits the abundance and diversity of other species as well. In this study three questions concerning the differences in the fungal communities between mixed forests and coniferous forests were considered. Inventories were done in coniferous forest and mixed forest areas classified as nature reserves and later statistically analyzed. The study could show that while the probability of finding ectomycorrhiza was significantly higher in mixed forests than coniferous forests, the probability of finding saprotrophs was significantly higher in coniferous forests than in mixed forests. Results in contrast to other studies were also found. The study revealed that more is needed to be done on the topic of forest fungi in mixed forest and coniferous forest areas. / Svampdomänen har en av de högsta biologiska mångfalderna bland eukaryoter och domänens arter innehar viktiga ekologiska roller, såsom mutualistisk mykorrhiza, nedbrytare, parasiter och patogener. Utvecklingen av skogsekosystem och deras relaterade processer har inte bara kopplats till svampdiversitet utan svamparnas sammansättning och förekomst gynnar också förekomst av och mångfald hos andra arter. I denna studie behandlades tre frågor om skillnaderna i svampsamhällen mellan blandskogar och barrskogar. Inventeringar gjordes i barrskogs- och blandskogsområden klassificerade som naturreservat och analyserades senare statistiskt. Studien kunde visa att även om sannolikheten för att hitta ektomykorrhiza var signifikant högre i blandskogar än barrskogar, var sannolikheten för att hitta saprotrofer signifikant högre i barrskogar än i blandskogar. Resultat i motsats till andra studier hittades också. Studien visade att det behövs mer forskning om skogssvampar i blandskog och barrskogsområden.
10

Dynamics of Forest Ecosystems Under Global Change: Applications of Artificial Intelligence in Mapping, Classification, and Projection

Akane Ota Abbasi (17123185) 10 October 2023 (has links)
<p dir="ltr">Global forest ecosystems provide essential ecosystem services that contribute to water and climate regulation, food production, recreation, and raw materials. They also serve as crucial habitats for numerous terrestrial species of amphibians, birds, and mammals worldwide. However, recent decades have witnessed unprecedented changes in forest ecosystems due to climate change, shifts in species distribution patterns, increased planted forest areas, and various disturbances such as forest fires, insect infestations, and urbanization. These changes can have far-reaching impacts on ecological networks, human well-being, and the well-being of global forest ecosystems. To address these challenges, I present four studies to quantify forest dynamics through mapping, classification, and projection, using artificial intelligence tools in combination with a vast amount of training data. (I) I present a spatially continuous map of planted forest distribution across East Asia, produced by integrating multiple sources of planted and natural forest data. I found that China contributed 87% of the total planted forest areas in East Asia, most of which are located in the lowland tropical/subtropical regions and Sichuan Basin. I also estimated the dominant genus in each planted forest location. (II) I used continent-wide forest inventory data to compare the range shifts of forest types and their constituent tree species in North America in the past 50 years. I found that forest types shifted more than three times as fast as the average of their constituent tree species. This marked difference was attributable to a predominant positive covariance between tree species ranges and the change of species relative abundance. (III) Based on individual-level field surveys of trees and breeding birds across North America, I characterized New World wood-warbler (<i>Parulidae</i>) species richness and its potential drivers. I identified forest type as the most powerful predictor of New World wood-warbler species richness, which adds valuable evidence to the ongoing physiognomy versus composition debate among ornithologists. (IV) In the appendix, I utilized continent-wide forest inventory data from North America and South America and the combination of supervised and unsupervised machine learning algorithms to produce the first data-driven map of forest types in the Americas. I revealed the distribution of forest types, which are useful for cost-effective forest and biodiversity management and planning. Taken together, these studies provide insight into the dynamics of forest ecosystems at a large geographic scale and have implications for effective decision-making in conservation, management, and global restoration programs in the midst of ongoing global change.</p>

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