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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.
11

Pušinių stiebinių nematodų (Bursaphelenchus sp.) paplitimas Lietuvoje / Distribution of pine wood nematodes Bursaphelenchus sp. in Lithuania

Kučinskas, Vaclovas 14 June 2005 (has links)
Objective – research the pine wood nematodes Bursaphelenchus sp. situation in Lithuania. Goals: 1. Research of native pine wood nematode species composition in Lithuania; 2. Research of preconditions for harmful pine wood nematode species to enter Lithuania; 3. Research of conditions for non-native pine wood nematode species to establish, breed and spread; 4. Research of consequences if harmful species becomes established in Lithuania, anticipate pest management options. Object of the study – coniferous (pine) forests in Lithuania and companies, processing imported wood. Methods. Samples were taken in coniferous clearcuts and wood processing companies from the stained wood or wood with evidence of Monochamus activities. Nematodes were extracted sing Baermann method. Preconditions for nematodes to enter Lithuania, establish and spread were analysed using statistical and literature sources. Strengths, weaknesses, opportunities, threats (SWOT) analysis was applied to the situation of Bursaphelenchus in Lithuania. Results. 27 forest enterprises and 62 wood processing companies were studied. For the first time in Lithuania non-pathogenic species Bursaphelenchus mucronatus was found. Assessement of conditions for wood nematodes in the country (import assortment and volume, countries, host plants and potential vectors), real probability for harmful species, particularly Bursaphelenchus xylophilus, to enter, establish and spread was defined. Existing quarantine system might... [to full text]
12

Žemaitijos nacionalinio parko paprastosios eglės (Picea abies (L.) Karst.) medynų būklės analizė / Analysis of health condition of Scots pine (Picea abies (L.) Karst.) forest stands in Žemaitija national park

Tarvydas, Arūnas 10 August 2009 (has links)
Didėjant aplinkos taršai ir miškų nykimui, vis didesnę reikšmę įgyja medžių fiziologinės funkcijos ir biocheminės-biofizinės reakcijos. Iš visų medžių rūšių spygliuočiai yra patys jautriausi teršalų indikatoriai, savo morfologiniais pokyčiais signalizuojantys apie pasikeitusią aplinkos būklę. Žemaitijos nacionalinis parkas įsteigtas Lietuvos Respublikos Aukščiausios Tarybos 1991 m. balandžio 23 d. įsteigtas tam, kad būtų išsaugoti nacionalinės svarbos kraštovaizdžio kompleksai bei antropoekosistemos, reprezentuojančios Žemaitijos etnokultūrinės srities gamtinius ir kultūrinius savitumus, saugoti, tvarkyti ir naudojimui reguliuoti. Nuo septinto dešimtmečio susirūpinus pavienių gamtos ir kultūros objektų – atodangų, medžių, piliakalnių, pastatų ir pan. – išsaugojimu, kai kurioms šio krašto vertybėms buvo suteiktas gamtos ar kultūros paminklo statusas. Pagal tarptautinio miškų monitoringo metodiką (Manual on Methods <…>, 1994), buvo ištirta Žemaitijos nacionalinio parko 408 paprastosios eglės (Picea abies (L.) H. Karst.) apskaitos medžių pagal svarbiausius I-ojo lygio miškų monitoringo rodiklius: Krafto klasę, perimetrą, viršūnės būklę, sausų šakų kiekį, derėjimą, spyglių išsilaikymo amžių, lajos formą, lajos pažeidimo tipą, lajos defoliaciją, 1/3 lajos defoliaciją, vizualiai pastebimus medžių pažeidimus. Morfologinių rodiklių reikšmės indikuoja, kad Žemaitijos nacionalinio parko eglynų būklė yra gana gera: eglių sausų šakų vidutinis kiekis – 18,62±0,32 %, spyglių išsilaikymo... [toliau žr. visą tekstą] / While environment pollution and forest disappearance are constantly increasing physiological functions and biochemical – biophysical reactions of trees are gaining growing significance. Conifers are the most sensitive indicators of pollution of all the kinds of trees; they, using their morphological changes, can signalize about aberrant environmental condition. Žemaitijos National Park was established by Lithuanian Republic Highest Council in 1991 in order to conserve the landscape complexes of national importance and anthropoecosystems, representing the nature and culture distinction of Žemaitija ethnografical district. Besides, one of the main purpose of Žemaitija National Park is to save, arrange and regulate the using of these nature and culture resources. In the 7th decade it was bothered about the conserving the single objects – exposures, trees, mounds, buildings etc., some of them was provided the status of nature or culture monument. According to international methods of forestry monitoring (Manual on Methods <…>, 1994), 408 vulgar firs (Picea abies (L.) H.Karst) have been investigated. The main indices of the 1st level forestry monitoring have been assessed: Kraft rating, perimeter, the condition of treetop, the amount of dead branches, crop, the age of thorn persistence, tree form, the type of lesion, defoliation, 1/3 of defoliation and violation that can be seen visually. The age of thorn persistence, defoliation and 1/3 of defoliation have been chosen as main... [to full text]
13

Effects of wildfire and prescribed burning on soil fauna in boreal coniferous forests /

Malmström, Anna, January 2006 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.
14

Naturvärdesbedömning och hänglavsinventering i fjällnära barrskog : En jämförande studie mellan två likartade områden med olika påverkan av skogsbruk i Tärnaby, Västerbottens län / Natural values and occurrence of pendulous lichen in subalpine coniferous woodland : A comparing study between two similar areas affected differently by forestry

Ransgart, Emmy January 2021 (has links)
The aim of the study was to investigate natural values and the occurrence of pendulous lichens species in two areas located in subalpine coniferous woodland in Tärnaby, Västerbotten county in northern Sweden. The two areas have similar geology, hydrology and vegetation. Area A is affected by forestry, whilst area B isn’t. Forestry is one of the biggest threats to woodland species because it causes habitat fragmentation a loss of habitat. Pendulous lichens are most occurring in old growth forests where natural processes have been left undisturbed. Therefore, red-listed pendulous lichens are often used as a nature value indicator for identifying old-growth forests. In each study area, five sample areas was studied. In each sample area, a nature value assessment and an inventory of pendulous lichen species and red-listed pendulous lichen species was performed. In area A, three species of pendulous lichen where found, and five species were found in area B. In area B, two of the species found were Alectoria sarmentosa and Bryoria nadvornikiana, both listed as NT in the IUCN red list. In area A, no red listed species were found. Results also showed a higher natural value in the area not affected by forestry, area B, than in area A. The natural values and occurrence of pendulous lichen and red-listed pendulous lichen was higher in area B than in area A. The cause of the differences can’t be identified by this study, but the effect of forestry is probably one of the causes.
15

Heterogenitet i skogsbestånd : faktorer av betydelse för artrikedom och förekomst av småfåglar / Heterogeneity of forest habitats : factors of importance for species richness and abundance among passerine birds

Strömberg, Sanna January 2011 (has links)
Denna studie undersökte hur heterogenitet i skogsbestånd samt omgivningsfaktorerna träddiameter, variation i träddiameter, död ved och lövinslag påverkar förekomsten av 18 skogsfågelarter i södra Sverige. Fågelinventeringen utfördes med hjälp av linjetaxering längs 100 meter långa transekter. Omgivningsfaktorerna mättes i varje transekt i fem provcirklar med diametern 10 meter. Analysen av träddiameter visade att det främst var diameter på barrträd, men inte på lövträd som inverkade på förekomsten av fåglarna. Sambanden mellan diameter på barrträd och totalt antal fågelarter var övervägande negativa vid 0-30 centimeter i diameter och övervägande positiva vid 30-80 centimeter i diameter. Totalt antal fågelarter samt förekomsten av taltrast och nötväcka ökade även signifikant vid ökad variation i träddiameter. Vid ökad grundyta död ved sågs tendenser till att totalt antal fågelarter och förekomsten av flera enskilda fågelarter ökade. Att antalet arter ökade vid en diameter över 30 centimeter kan kopplas till att förekomsten av håligheter då är högre. I Sverige avverkas granar när de är cirka 30 centimeter i diameter. Resultatet tyder alltså på att avverkningen av gran sker vid den storlek då träden börjar få en positiv inverkan på antalet fågelarter. Att antalet arter ökade vid ökad variation i träddiameter kan bero på ett större utbud av mikrohabitat. Slutsatsen av resultaten är att framförallt diameter på träd, variation i träddiameter och till viss del död ved är viktiga omgivningsfaktorer som påverkar antalet fågelarter. För att bevara artrikedomen av fåglar i svenska skogar bör därför dessa parametrar ingå i den naturhänsyn som tas i samband med skogsbruk. / In this study, the occurrence of 18 forest bird species in southern Sweden was investigated in relation to parameters such as forest heterogeneity and the environmental factors tree diameter, variation in tree diameter, dead wood and fraction of deciduous trees. Birds were recorded along transects of 100 meters. The relationships between coniferous tree diameters and total number of bird species were predominantly found to be negative at trunk diameters of 0-30 centimeters, while mainly positive at trunk diameters of 30-80 centimeters. Also, the total number of species significantly increased with increasing variation in trunk diameter. There was also a tendency towards an increase of the total number of species with increasing basal area of dead wood. In Swedish forestry, spruces are felled when they are about 30 centimeters in trunk diameter. Thus the results indicate that felling of spruce is at the size when the trees start having a positive effect on the number of bird species. That the number of species increased at trunk diameter above 30 centimeters can be connected to the fact that the number of cavities is higher. That the number of species increased with increasing variation in trunk diameter can be due to a larger range of micro habitats. In conclusion, tree diameter, variation in tree diameter and dead wood were demonstrated as important environmental factors affecting the number of bird species. In order to maintain bird species richness in Swedish forests, these environmental factors should be considered in the context of forestry.
16

針葉樹人工林におけるカラ類2種の繁殖生態と餌資源利用様式

水谷, 瑞希, Mizutani, Mizuki 12 1900 (has links) (PDF)
農林水産研究情報センターで作成したPDFファイルを使用している。
17

Výukové programy s botanickou tématikou pro Bečovskou botanickou zahradu / Botanical educational programs for the Bečovská Botanical Garden

ŠPAKOVÁ, Markéta January 2018 (has links)
This thesis is dedicated to educational programs in Bečov Botanic Garden. The aim of this thesis was to extend the current offer to other botanical themes. Dendrological themes were selected for new educational programs. In total, three new educational programs were created. The first one is dealing with conifers, the second with cones of conifers and the third with broad-leaved species. All new programs include worksheets and methodological instruction for lectures and teachers. Tutorial tools (determination key, scale, educational box) were also created for the cone educational program.
18

Spatio-temporalité des dynamiques de feux et de végétation au cours de l'Holocène en forêt boréale coniférienne (Québec-Labrador) / Spatial and temporal dynamics of fire and vegetation during Holocene in coniferous boreal forest (Quebec-Labrador)

Remy, Cécile 15 December 2016 (has links)
Les changements climatiques en cours semblent être à l’origine d’une intensification de l’activité de feux dans les forêts circumboréales. Des modèles prédictifs basés sur des données historiques sont couramment utilisés pour essayer d’anticiper les régimes des feux et leurs impacts pour l’horizon 2100. Cependant, les concepts alimentant ces modèles reposent sur l’interprétation de données issues de seulement quelques régions alors que de nombreuses études ont montré que des facteurs régionaux à locaux tels que la topographie, la nature des sols, la composition et la structure de la végétation, ainsi qu’un profil climatique et une météorologie particulière, peuvent impacter l’activité de feux.Au nord-est du Canada, la région de l’est du Québec et du Labrador se caractérise, comparativement aux régions de l’ouest et du centre du Québec, un relief plus vallonné, une végétation différente (plus riche en sapin baumier et plus pauvre en pin gris) et un climat plus froid et plus humide. L’étude des processus liés aux dynamiques de feux et de végétation dans cette région, et leur comparaison avec ceux des régions de l’ouest et du centre au cours de l’Holocène ont donc été réalisées dans cette thèse. L’objectif global était de savoir si l’on peut se contenter de travailler à une échelle supra-régionale plutôt qu’à une échelle régionale ou locale pour prédire les conséquences des changements climatiques en cours sur la dynamique des forêts conifériennes du Québec-Labrador.Les résultats mettent en évidence l’impact de la taille des feux, jusqu’alors sous-estimé, sur la dynamique à long terme de la végétation au sein de chacune des régions. D’un point de vue général, la présence ou l’absence de grands feux a respectivement favorisé, selon le cas, la propagation du pin gris ou du sapin baumier, co-dominants dans le paysage avec l’épinette noire. De plus, les conditions pré-requises à l’éclosion des grands feux diffèrent entre la région de l’est et celles de l’ouest et du centre. Cette divergence s’explique en grande partie par l’influence prédominante de la topographie régionale au détriment de l’impact des grandes tendances climatiques sur l’activité de feux dans l’est.Au regard de nos résultats, les scénarios climatiques annoncés risquent d’augmenter l’occurrence des grands feux dans les régions de l’ouest et du centre du Québec sans qu’il y ait pour autant de conséquence significative sur la composition du couvert forestier. À l’est, les projections restent plus incertaines car les causes à l’origine des grands feux passés dans cette région n’ont pas été totalement élucidées. Cependant, toutes les hypothèses de trajectoires de végétation futures formulées dans cette thèse vont dans le sens d’un maintien du sapin baumier dans le paysage.Compte-tenu de la diversité des interactions susceptibles d’impacter significativement la taille des feux à l’échelle régionale, notre compréhension des processus liés aux dynamiques de perturbation et de végétation semble encore insuffisante pour pouvoir les prédire à large échelle. Il serait donc raisonnable, dans un premier temps, d’étudier plus finement ces processus à l’échelle de zones les plus homogènes possibles en termes de composition végétale, de topographie et de climat. C’est dans cette optique que l’amélioration méthodologique présentée dans cette thèse a été développée. Elle permet de différencier, à partir de l’analyse de dépôts de charbons dans les sédiments lacustres, les feux ayant eu lieu dans le bassin versant du lac étudié (local) de ceux s’étant produits à une plus grande distance (régional), et ce, à l’échelle plurimillénaire. Conjuguée à l’étude d’autres bio-indicateurs permettant de reconstruire l’environnement passé à l’échelle locale, nous devrions être capables de mieux comprendre les causes et conséquences des variations de taille des feux au regard des différentes combinaisons observées de facteurs environnementaux dans l’avenir. / Wildfire activity is projected to increase under global warming in circumboreal forests. Predictive fire models based on historical data are commonly used to anticipate fire regimes and their impacts for 2100. However, these models at large scale depend on concepts developed from only some regional data, while many studies showed that regional and local factors such as topography, soil type, vegetation composition and structure, and particular climatic and meteorological patterns can impact the fire activity.In north-eastern Canada, the eastern region of Quebec-Labrador and the western and central regions of Quebec display distinctive types of relief, climate and vegetation. The drier and flatter western region is mainly dominated by black spruce (Picea mariana) and jack pine (Pinus banksiana), while the more humid and hilly eastern region is dominated by black spruce and balsam fir (Abies balsamea). In this thesis, I compared the processes linked to dynamics of fire and vegetation within and among the three regions. The main objective was to test whether working at the supra-regional scale rather than at regional or local scale is enough to predict efficiently the consequences of current climatic changes on the coniferous forest dynamics in Quebec-Labrador.Results highlight the impact of fire size, hitherto underestimated, on the long-term vegetation dynamics within each region. Overall, the presence or absence of large fires promoted the propagation of jack pine or balsam fir in black spruce forests, respectively. Moreover, the prerequisite conditions for ignitions inducing large fires differ between the eastern region and the two others. This divergence is mainly explained by the predominant influence of regional topography on fire activity (ignition and propagation) in eastern region, while large climatic trends and their impacts explain better the fire activity (mainly propagation) in western and central regions.According to these results, future climate changes could increase large-fire occurrences in western and central regions of Quebec likely without significant consequences on forest composition. In the eastern region, projections are more uncertain due to a lack of full understanding of past large-fire causes. However, all assumptions for future vegetation trajectories showed that balsam fir should be still present in these landscapes.Due to the high diversity of interactions able to impact significantly fire size at regional scale, our understanding of processes linked to dynamics of disturbances and of vegetation seems to be still not sufficient to make predictions at large scale. It would be worth, first, to study more finely these processes on homogenous zones in terms of vegetation composition, topography and climate. The methodological improvement on lacustrine charcoal analysis presented in this thesis has been developed in this perspective. It allows differentiating fires that occurred in the studied lake watershed (local) from those that burned further away (regional). In the future, analyses of local fire histories combined with studies of other proxies to reconstruct the past environment at local scale should allow a better understanding of causes and consequences of fire size variations according to the various combinations of environmental factors.
19

Matematické metody modelování morfologie jehličnanů / Mathematical methods of morphology modelling of coniferous trees

Janoutová, Růžena January 2012 (has links)
The thesis was focused on creation of a coniferous tree by nondestructive method allowing description of structure of adult spruce trees. After processing provided data we created a model of L-system which creates a tree branch. Thereafter, a Python script generated parameters which were required for the creation of the model of the tree in graphical software Blender. Model of coniferous tree was sucesfully generated. Its memory requirements are high but for our purposes this is not an essential problem.
20

Substratpreferenser hos Crossocalyx hellerianus i svenska barrskogar : är skoglig kontinuitet en viktig faktor?

Kvarnsudde, David January 2020 (has links)
In recent time, forests in Sweden have lost habitat quality in the loss of deadwood due to the practices in productions forestry. This means that substrates for epixylic species has decreased both in quality and quantity. The aim with this study was to find which preferences the epixylic liverwort, Crossocalyx hellerianus has on its substrate and environment. C. hellerianus requires coarse logs with rotten wood, which usually is more available in forests with long forest continuity. This study was performed to see if forest continuity, isolation of habitats and if the substrate was of significance for a demanding species such as C. hellerianus. The study was performed in six sites and in each site several 50x10 meter transects were surveyed for logs. Each log was measured for diameter, sun exposure, ground contact, stage of decay and if the log was colonized by C. hellerianus. The result showed that C. hellerianus preferred coarser logs and that the species only appeared on an intermediate or later stage of decay. A high forest continuity and low habitat isolation turned out to be positive factors for the abundance of C. hellerianus

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