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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

Förröjningsstrategier vid förstagallring. : En jämförelseanalys mellan två olika förröjningsmetoder.

Åsa, Andersson January 2016 (has links)
The need for brushing before the first thinning has increased during the last few years. This brushing involves taking away small trees and bushes making it able for the harvester operator to see better and choose the correct trees to be harvested. In today’s silviculture the brushing is often neglected which means that the undergrowth becomes dense and leads to less efficiency for harvesters and a rise in costs. A well brushed first thinning will make the harvesting costs low and time efficient.   In brushing before the 1st thinning all stems below 9 cm d bh are traditionally taken down. This has a tendency to become stereotyped; i.e. brushes are also taken away in areas where  stronger nature conservation should be applied, as in wetlands, edge zones, etc. The harvester operator then gets stuck in these zones which threaten the biodiversity.    This study aims at examining two different types of brushing methods before the thinning, the traditional one and another (new) method where environmental and nature protection aspects were taken into account to a greater degree; i.e. where more stems and undergrowth have been left over and edge zones were not brushed. The study results show that the latter one is to prefer as the more cost efficient one. It also protects the harvester to drive out into the edge zones. This method is also beneficial for the wildlife.   Most harvester operators were positive to a new brushing manual.
2

Occurrence, morphology and growth of understory saplings in Swedish forests /

Wikberg, Per-Erik, January 2004 (has links) (PDF)
Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 3 uppsatser.
3

Nitrogen enrichment of a boreal forest : implications for understory vegetation /

Forsum, Åsa, January 2008 (has links) (PDF)
Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2008. / Härtill 4 uppsatser.
4

Pušynų atvejinių kirtimų įtaka žemutinio medyno ardo formavimuisi / The infuence of pinewood's shelter wood cutting for wood's ground layer

Jonauskas, Rimvydas 15 June 2009 (has links)
Magistro darbe tiriama pušynų atvejinių kirtimų įtaka medynų žemutinių ardų augalijos formavimuisi. Darbo objektas: Tyrimo objektas – pomiškis, žolinė augmenija ir samanos neplynose pušynų kirtavietėse. Darbo tikslas: Ištirti pomiškio, žolinės ir samanų dangos formavimosi ypatumus pušynų atvejinių kirtimų kirtavietėse. Darbo metodai: Pušynuose, kuriuose buvo atlikti atvejiniai kirtimai buvo parinkti 4 pastovūs bareliai. Trijuose bareliuose atvejiniai kirtimai buvo vykdyti 2007 metais, o viename tyrimų barelyje – 2005 metais. Visuose bareliuose augavietės tipas buvo Nbl. Pomiškis, žolinė ir samanų danga buvo įvertinta 20 m ilgio ir 1 m pločio transektose. Pomiškis skaičiuotas nurodant rūšį ir skaičių. Samanų, žolinės augmenijos projekcinis padengimas įvertintas procentais. Darbo rezultatai: Vidutinis paprastosios pušies daigų kiekis 1 m2 antrais metais po atvejinių kirtimų sumažėjo, o karpotojo beržo daigų kiekis 1 m2 iš esmės nepasikeitė. Kai kuriose kirtavietėse antrais metais po kirtimų atsirado paprastosios eglės daigų. Kirtavietėse rastos 29 skirtingos žolių rūšys. Daugeliu atvejų antrais metais po atvejinių kirtimų kirtavietėse žolių rūšių skaičius padidėjo. Žolinės dangos vidutinis projekcinis padengimas antrais metais po atliktų atvejinių kirtimų ženkliai padidėjo. Daugiausiai vidutinis projekcinis padengimas praėjus metams po atvejinių kirtimų padidėjo kirtaviečių augalų – miškinio ir smiltyninio lendrūnų. Viso rastos 4 samanų rūšys. Vidutinis projekcinis samanų... [toliau žr. visą tekstą] / The object of the study: Undergrowth, herbs and moss in pinewoods after shelterwood cuttings. The aim of the study: The main goal of this research was to find out influence of shelterwood cuttings on herbs, moss and seedlings in pinewoods. Methods: The research areas were established in 2007 year shelterwood cutting and in 2005 year shelterwood cutting of pinewood. Saplings, herbs and moss were counted in transect which was 20 meters length and 1 meter width. There were indicated saplings species and number. Average cover projection of herbs and moss was evaluated by percent. The results: The average the number of pine’s saplings decreased in one square meter in shelter wood cuttings of second year. The average the number of birch saplings didn’t change in one square meter in essence on the following year after shelterwood cuttings. In some shelterwood cuttings were found spruce’s saplings on second year. There were 29 different species of herbs in shelterwood cuttings. In most cases the number of herbs species increased on following year. Average cover projection of herbs signally increased on the following year after shelterwood cuttings. There were founded 4 species of moss. Moss average cover projection didn’t change in essence on the following year after shelterwood cuttings.
5

Miško žemutinių ardų augalų atsistatymas po pažeminių gaisrų pušynuose / The recovery of plants in lower pine forest layers after the surface fire

Kolkienė, Jolita 21 June 2010 (has links)
Pažeminiai miško gaisrai padidino samanų dangos rūšinę sudėtį. Na ir Nb augaviečių gaisravietėse nustatytos 11 samanų rūšių, o kontroliniuose medynuose – 5 rūšys. Dėl gaisrų atsirado 8, o išnyko 2 samanų rūšys. / The composition of cover moss species was increased by ground-level fire. There were established 11 species of moss in Na and Nb habitats fireplaces and 5 species in control stands. Because of fire appeared 8 species of moss and disappeared 2 species of moss.
6

Augalijos pokyčiai po pažeminio miško gaisro Zarasų miškų urėdijoje, Salako girininkijoje / Changes of vegetation after the ground-level forest fire in Zarasai forests' state, Salakas district:

Kačiulytė, Alina 20 June 2012 (has links)
Darbo objektas – Gaisravietė Zarasų miškų urėdijos Salako girininkijos 48 kvartalo 10 sklype. Darbo tikslas – nustatyti žemutinių miško ardų: pomiškio, trako, žolinės augalijos ir samanų kaitą, metinį medienos prieaugio kitimą po pažeminio gaisro pušyne Nb augavietėje. Darbo metodai – gaisravietėje buvo parinkta 1 m pločio ir 20 m ilgio juostos. Apskaitos aikštelių pradžia ir pabaiga pažymėta natūroje. Vieno kv. m. (1m x 1 m) apskaitos aikštelėse nustatytas degavietės padengimas trako ir pomiškio augalų, žolių bei samanų danga procentais, suskaičiuoti medžių daigai, registruotos žolių ir samanų rūšys, įvertinant jų padengimą procentais. Šiame darbe pateikiami 2006-2011 m duomenys. Iš 20 pušų I ir II klasės pagal Krafto klasifikaciją, naudojant Pressler grąžtą 1,3 m aukštyje buvo paimti mėginiai metiniam medienos prieaugiui nustatyti. Metiniam medienos prieaugio matavimui buvo naudojama LINTAB medžių matavimo sistema ir TSAP programų rinkinys. Darbe pateikiami 1990 – 2010 metų medienos prieaugio kitimai. Duomenys kaupiami duomenų bazėje panaudojant programą EXCEL. Darbo rezultatai. Po pažeminio miško gaisro pušyne Nb augavietėje pomiškis išnyko, o trako augalų kiekis nežymiai sumažėjo ir išnyko prieš tai augęs paprastasis šermukšnis. Pažeminis miško gaisras padidino gaisravietės ploto padengimą žoliniais augalais ir žolinės dangos rūšinę sudėtį. Gaisravietėje nustatyta 16 žolių rūšių, o kontroliniame medyne 9 žolių rūšys. Po pažeminio miško gaisro atsirado 9 naujos o... [toliau žr. visą tekstą] / The object – 10th plot of 48th block of Zarasai state forests’ Salakas forestry. The aim – to determine the lower forest quarrel: the change of undergrowth forest, underbrush, herbaceous and moss, also, variation of annual timber increment after the ground-level fire in a pine forest Nb habitat. The methods – there were chosen bands of 1 meter wide and 20 meters length in the fire place. A beginning and an end of the accounting sites were marked at a ground. In a one square meter (1 m x 1 m) accounting sites there were determined percentage of the fire place’s coverage by the underbrush, undergrowth forest, grass and moss cover. In addition, there were counted tree seedlings, there were registered grass’ and moss’ species evaluating their coverage in percentage. This paper presents data from 2006 till 2011. According to Kraft classification, there were taken samples from the 20 pines of the first and the second classes, using Pressler drill in the height of 1,3 meters, to determine the annual increment. For a measuring of the annual timber increment there was used LINTAB tree measuring system and TSAP program set. This paper presents a variation of timber growth in 1990-2010. The data are stored in a data base using the EXCEL program. The results. After the ground-level forest fire in the pine forest Nb habitat the undergrowth forest disappeared and the underbrush plants slightly decreased, moreover, a rowan, which grew before the fire, disappeared. The... [to full text]
7

How Does Past Grazing and Surrounding Landscape Affect the Restoration Sucess of Deciduous Forests?

Ringselle, Björn January 2010 (has links)
The Swedish deciduous forest has been actively replaced by coniferous forest during the last two hundred years. In Färna Ekopark, Västmanland, this trend is being reversed by restorations of deciduous forests through the removal of coniferous trees in mixed forests. This field study investigates how successful these restorations have been for plant diversity and how they were affected by past grazing and the proportion of similar mixed and deciduous forest habitats in thesurrounding landscape. Plant species richness was investigated in 370 1m2-plots distributed over 37 sample areas and the surrounding landscape analyzed in a GIS. Results show that a few years after restoration there was higher plant species richness and lower homogenization, at the site scale, compared to the controls. When the restored sites were divided into two subgroups dependant on age, the 5-6 year old restoration displayed higher plot richness than the 2-4 year old restorations, but were also more homogeneous. Past grazing showed a generally positive effect on plant diversity, and these areas also responded with a larger increase of plant species richness and less homogenous plant populations after restorations compared to areas that had not been formerly grazed. The proportion of similar deciduous and mixed forest habitats (more than 40 % deciduous trees) inthe surrounding landscape showed no effect on the plant diversity of deciduous forests in general, though it did display a weak influence over the plot richness of restored deciduous forests without a history of grazing. When restoring deciduous forests to increase plant diversity it would therefore appear wise to focuson the formerly grazed deciduous forests. To take advantage of the beneficial effects to plot richness restored deciduous forests should have a high degree of deciduous and mixed forests within one kilometer. / Den svenska lövskogen har aktivt ersatts med barrskog under de senaste tvåhundra åren. I Färna Ekopark, Västmanland, försöker man vända denna trend genom att ta bort barrträd i blandskog ochpå så sätt restaurera lövskog. Denna fältstudie undersöker om restaureringarna har gett ökad växtdiversitet och hur restaureringarna har påverkats av tidigare bete samt andelen av liknande bland- och lövskogshabitat i det omgivande landskapet. Växtartantalet undersöktes med 370 1m2-rutor utspridda över 37 områden och det omgivande landskapet analyserades i ett GIS. Resultaten visar att några år efter restaurering hade områdena högre växtdiversitet och artsammansättningen var mindre likformig i jämförelse med kontrollerna. När de restaurerade områdena delades upp i två grupper, i avseende på ålder, uppvisade de 5-6 år gamla restaureringarna högre växtdiversitet i rutorna än de 2-4 år gamla restaureringarna, men artsammansättningen var även mer likformig. Tidigare bete visade en generellt positiv inverkar på växtdiversiteten och dessa områden fick en ännu större uppgång i artrikedom och ännu lägre likformighet i artsammansättningarna efter restaureringarna än de områden som inte hade betats tidigare. Andelen av liknande bland- och lövskogshabitat (mer än 40 % lövträd) i det omgivande landskapet uppvisade ingen effekt på växtdiversiteten hos lövskog generellt, men det fanns en svag påverkan på växtdiversiteten på rutnivå hos restaurerade lövskogar utan tidigare bete. När man restaurerar lövskog för att öka växtdiversiteten verkar det därför bra att fokusera på tidigare betade lövskogar. Om man vill ta tillvara på den positiva påverkan på växtpopulationerna som omgivande landskap kan ha bör restaurerade lövskogar ha en stor andel bland- och lövskog en kilometer runt omkring sig.
8

Savaiminis žėlimas eglynuose priklausomai nuo jų struktūros / Self regeneration spruce dependence of stand structure

Gervelis, Deimantas 14 January 2009 (has links)
Darbo objektas – grynų eglynų pomiškis Lietuvos miškuose. Darbo tikslas – ištirti savaiminio žėlimo priklausomybę eglynuose nuo jų erdvinės struktūros. Darbo metodai : miškų inventorizacijos ir laikinų apskaitos aikštelių duomenų analizės, matematinės statistikos metodai. Darbo rezultatai. Remiantis miškų inventorizacijos bei laikinų apskaitos aikštelių duomenimis, išanalizuotas pomiškio kiekis eglynuose priklausomai nuo jų augavietės, amžiaus, skalsumo bei medyne susidariusių aikščių dydžio. Nustatyta, kad tik 20 % vyresnių nei 40 metų eglynų turi pomiškio. Didžiausias kiekis pomiškio rastas Ld ir Nb augavietėse (1,9 tūkst. vnt./ha). 4 – 12 amžiaus klasių eglynuose didėjant amžiui pastebimas nežymus pomiškio kiekio didėjimas. Ištyrus pomiškio kiekio priklausomybę nuo skalsumo nustatyta, kad skalsumui mažėjant, pomiškio kiekis didėja. Pomiškio kiekis priklausomai nuo aikštės dydžio svyruoja nuo 12 iki 17 tūkst. vnt./ha aikštės plotui didėjant nuo 2 iki 10 arų. / Work subject – Undergrowth of spruce stands in Lithuanian forests. Work objective – To estimate forest grows in itself of spatial structure in spruce stand. Work methods: Data analyses of forest inventory and temporary of free space in forest, mathematical statistics methods. Work results. Was made analyses of spruce undergrowth quantity in different forest site type, age, growing stock and free space size in forest. It was established that 20 % of older then 40 years spruce forests has undergrowth. The biggest amount of growth was found in Ld and Nb forest site types. When age is growing in 4 – 12 age class of spruce the undergrowth quantity is growing too. It is ascertain that undergrowth quantity is rise up when growing stock is felling down. Undergrowth quantity variations of 12 to 17 thous.units/ha when free space size in forest variation of 2 to 10 are.
9

Underröjningsgradens påverkan på förstagallringsnetto med flerträdsaggregat / Effects of pre-commercial thinning with multi-grip harvester on first thinning net value

Gunnarsson, Björn January 2015 (has links)
I Sverige finns ca 1,2 miljoner hektar skog som bedöms ha omedelbart röjningsbehov. Skog där röjningen uteblir eller är svag kan komma att klassas som konfliktbestånd. I konfliktbestånd är stammarna många och diameterspridningen stor och dessa kan då behövas underröjas innan gallring. I denna studie jämfördes produktionen, kostnaderna och intäkterna från fyra olika underröjningsbehandlingar, oröjd, siktröjt, röjt allt upp till 5 cm i brösthöjd och röjt allt upp till 7 cm i brösthöjd. Behandlingen oröjd gav det bästa nettot och sämst hade upp till 5 cm efter gallring och uttransport av virke. En anpassad eller svag röjning gav lägre totalkostnader jämfört med ingen eller hårdare röjning. / In Sweden there are about 1,2 million hectares of forest with immediate need of pre-commercial thinning. Stands, where conducted pre-commercial thinning are light or even absent, become tight with thin stems. In such stands pre-commercial thinning before first thinning may be required, due to operational advantages such as increased visibility. This study compared production, cost and revenues from four different pre-commercial thinning treatments: no pre-commercial thinning, sight pre-commercial thinning, cleared everything up to 5 cm diameter at breast height and cleared everything up to 7 cm diameter at breast height. The treatments whit no pre-commercial thinning had best net value and worst had up to 5 cm. A custom or weak pre-commercial thinning give a lower total cost compared to no or harder pre-commercial thinning.
10

Le genre Psychotria (Rubiaceae) en Afrique occidentale et centrale: taxonomie, phylogénie et biogéographie / Genus Psychotria (Rubiaceae) in West and Central Africa: taxonomy, phylogeny and biogeography

Lachenaud, Olivier 11 September 2013 (has links)
Le genre Psychotria est le plus vaste de la famille des Rubiaceae, avec plusieurs centaines d’espèces répandues dans toutes les régions tropicales humides. Les Psychotria sont principalement des arbustes (quelques-uns sont lianescents, herbacés ou arborescents) et entrent souvent pour une part importante dans la composition des sous-bois tropicaux. Certains montrent des adaptations remarquables comme la symbiose bactérienne foliaire ou l’accumulation d’humus. En raison de sa taille et des difficultés d’identifications, ce genre reste mal connu, notamment en Afrique occidentale et centrale où il n’a fait l’objet d’aucun travail d’ensemble depuis les années 1960.<p>Le présent travail a pour objectifs :1) la révision taxonomique du genre Psychotria pour l’Afrique occidentale et centrale; 2) une étude phylogénétique du genre, visant à reconstituer son évolution et améliorer la classification infragénérique ;et 3) une étude biogéographique régionale de ce groupe, afin de définir des centres de diversité et d'endémisme.<p>Notre travail de taxonomie, fondé sur l’examen des spécimens d’herbier et sur des missions de terrain au Cameroun et au Gabon, nous a conduit à reconnaître l’existence de 232 espèces en Afrique occidentale et centrale, ce qui fait de Psychotria le plus vaste genre de plantes dans cette région. Parmi ces espèces, 78 sont nouvelles.<p>Nos travaux phylogénétiques, basés sur l’étude de deux marqueurs nucléaires (ITS et ETS) et quatre chloroplastiques (rps16, trnG, matK et rbcLa), montrent que la classification de Petit (1964, 1966) est largement à revoir. Il apparaît notamment que les deux sous-genres (Psychotria et Tetramerae) reconnus en Afrique, et fondés sur la présence ou l’absence de nodules bactériens foliaires, ne sont pas monophylétiques, certaines espèces ayant secondairement perdu leurs nodules. Nos résultats soutiennent également le rattachement du genre monospécifique Peripeplus à Psychotria.<p>Le genre Psychotria montre une diversité remarquable, associée à un taux d’endémisme élevé, dans le domaine bas-guinéen (Cameroun et Gabon principalement) où plusieurs centres d’endémisme ont été identifiés. Ceux-ci sont localisés non seulement dans les massifs montagneux de l’intérieur, dont la flore particulière est bien connue, mais également dans les régions littorales. L’Afrique de l’ouest, moins diversifiée, montre cependant un fort endémisme localisé principalement dans deux centres, l’un situé au Liberia et dans l’ouest de la Côte d’Ivoire, l’autre vers la frontière Côte d’Ivoire/Ghana. Le bassin du Congo, comparable en diversité à l’Afrique de l’Ouest, est relativement pauvre en endémiques.<p>Ces résultats suggèrent que les forêts du Cameroun et du Gabon auraient relativement bien résisté aux périodes sèches passées, et remettent notamment en question l’hypothèse d’une disparition des forêts littorales du golfe de Guinée au cours du Pleistocène./Psychotria is the largest genus in the Rubiaceae family, with several hundred species in wet tropical areas worldwide. Psychotria spp. are mostly shrubs (a few being lianas, creepers or trees) and are often an important component of the undergrowth in tropical rainforests. Some show remarkable adaptations such as leaf bacterial symbiosis or litter gathering. Due to its size and identification problems, Psychotria remains a little-known genus, especially in West and Central Africa, where no major work has been done on this group since the 1960s.<p>The aims of the present work are: 1) a taxonomic revision of Psychotria in West and Central Africa; 2) a phylogenetic study of the genus, in order to trace its evolution and improve the infrageneric classification; and 3) a regional biogeographic study of the genus, to define centers of diversity and endemism.<p>Our taxonomical work, based on the study of herbarium specimens and field expeditions in Gabon and Cameroon, led us to recognise 232 species of Psychotria in West and Central Africa. Psychotria is therefore the largest plant genus in this area. Among these species, 78 are new.<p>Our phylogenetic work, based on two nuclear markers (ITS and ETS) and four chloroplastic markers (rps16, trnG, matK, rbcLa), shows that Petit’s (1964, 1966) infrageneric classification is in need of revision. In particular, we show that the two subgenera present in Africa (subg. Tetramerae and subg. Psychotria), which are defined by the presence or absence of leaf bacterial nodules, are not monophyletic: a secondary loss of the bacterial nodules has occured in some species. Our results also support the merging of the monospecific genus Peripeplus into Psychotria.<p>The genus Psychotria shows a remarkable diversity and a high level and endemism in the Lower Guinea domain (particularly Cameroon and Gabon) where several centers of endemism are identified. These are located not only in the inland hill ranges, which are well known for their particular flora, but also in littoral areas. West Africa is less diverse but also shows a high level of endemism, which concerns mostly two areas, one in Liberia and western Côte d’Ivoire and the other around the Côte d’Ivoire/Ghana border. The Congo basin, comparable in diversity to West Africa, has relatively few endemic species.<p>These results suggest that the rainforests of Cameroon and Gabon resisted relatively well during historical drier periods. They do not support the hypothesis of a disappearance of the Gulf of Guinea littoral forests during the Pleistocene.<p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

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