Search results for "Betula"
showing 10 items of 71 documents
Klimatisko faktoru ietekme uz pundurbērza Betula nana augšanu Teiču purvā un purvainajā mežā
2020
Lai paredzētu, kādu iespaidu uz augu augšanu atstās klimatiskās pārmaiņas nākotnē, ir jāuzzina, kā uz svarīgākajiem klimatiskajiem faktoriem tie reaģējuši iepriekš. Viena no biežāk izmantotajām metodēm kā iegūt informāciju par klimatisko faktoru ietekmi uz attiecīgo sugu ir izmantojot gadskārtu platumu variēšanu un atšķirības gadskārtu anatomiskajā uzbūvē. Pēdējā laikā šādos dendrekoloģiskajos pētījumos izmanto tieši sīkkrūmu sugas, jo tie aug arī vietās, kur neaug koki. Bieži pētījumos izmanto pundurbērzu, kas Latvijā ir reta un aizsargājama suga. Pētījuma mērķis bija noskaidrot Teiču purvā un purvainajā mežā augošā pundurbērza gadskārtu platumu ekstrēmu jeb zīmīgo gadu saistību ar klimati…
An evaluation of the microscopical counting methods of the tape in hirst-burkard pollen and spore trap
1981
Abstract Three different sampling units in current use and different sampling strategies were tested. Randomly placed microscope fields are good in estimating the daily mean concentration, but very big sample size is needed. Traverses across the slide in systematic order are best to estimate the shortterm concentrations and diurnal variation. A formula for the estimation of the error in one transverse traverse is given. Twelve transverse traverses in systematic order is also enough to estimate the daily mean concentration. One or two traverses along the length of the slide give often unreliable estimates because of the irregularities in the transverse variation of the particle concentration…
Parameters Researches Regarding the Structural Parameters of the Populations of Rhynchitidae and Attelabidae in Romania
2012
The study of the two families took into account the economic factor, because there are not few species of Rhynchitidae and Attelabidae that produced important damages in the vine, orchard, and forest areas as well as in the agricultural cultures. The researches took place during 1996-2006. The fauna material was collected during the travels to different localities in the country. I n some investigated localities the collecting and the observations in the field were extended for at least 2 -3 days and for the vine ecosystems with a great attack of Byctiscus betulae the researches lasted for 3-4 years, at regulated intervals of 3-4 weeks. In order to establish the structural parameters there …
Kora brzozy brodawkowatej jako biomonitor zanieczyszczenia powietrza metalami ciężkimi
2018
Celem przeprowadzonych badań była ocena możliwości wykorzystania kory brzozy brodawkowatej (Betula pendula Roth) w biomonitoringu terenów leśnych. Do badań wykorzystano korę drzew rosnących na obszarze Beskidów i Puszczy Boreckiej. W korze, metodą absorpcyjnej spektrometrii atomowej ze wzbudzeniem w płomieniu (F-AAS), oznaczono stężenia metali ciężkich: Mn, Fe, Ni, Cu, Zn, Cd oraz Pb. Na podstawie przeprowadzonych badań stwierdzono sezonowe zmiany stężenia analitów. Wykazano również, że kora brzozy brodawkowatej może być wykorzystywana jako bioindykator do oceny zanieczyszczenia aerozolu atmosferycznego na tych obszarach np. metalami ciężkimi. Ważne jest jednak, aby dokonać walidacji poszcz…
Stand structure and spatial pattern of regeneration of Pinus sylvestris in a natural treed mire in Latvia
2009
We examined the regeneration patterns of Pinus sylvestris L. in a natural treed mire in the hemiboreal zone in Latvia. Data on tree stem age and size was collected in 207 fine-scale plots (10 m) and 4 medium-scale plots (400 m). Size structure of living and dead trees was also estimated on transects 180-m and 250-m length and 10-m width. In addition, the vegetation was described in 1-m plots to determine preferred microsites for P. sylvestris establishment. Pinus sylvestris showed continuous regeneration by an inverse J-shaped age and size structure. Pulses of mortality induced by fire were also evident. Regeneration of P. sylvestris was mostly on Sphagnum magellanicam Brid. hummocks free o…
Growth increase of birch seedlings under the influence of earthworms—a laboratory study
1992
The effects of the earthworm Lumbricus rubellus (Hoffm.) on net production and nitrogen content of birch seedlings were studied in laboratory microcosms. Coniferous forest floors with litter, humus and mineral horizons were simulated in transparent plastic cylinders. The materials were partially sterilized by microwaving, and re-inoculated with microflora and -fauna. A young (9 cm) birch seedling (Betula pendula Roth) was planted in each container. Earthworms were added to half of the replicates. The microcosms, through which a constant air flow was maintained, were incubated in a climate chamber. After two growth periods, leaf and stem biomasses of birch in treatments with earthworms incre…
Distribution ofLeprariain Latvia in Relation to Tree Substratum and Deciduous Forest Type
2012
The aim of the study was to evaluate the distribution of Lepraria lichen species in dry deciduous forests, in relation to tree substratum and forest characteristics. In total, 34 localities with 1020 trees (13 tree species) were studied in different parts of Latvia. Lepraria spp. were found on 642 trees: L. eburnea on 8 trees, L. incana on 80 trees, and L. lobificans on 568 trees. Lepraria eburnea was recorded for the first time in Latvia. Tree species, tree bark crevice depth, inclination, pH and forest type were the most important variables explaining the presence of Lepraria species. Lepraria incana was associated with Quercus robur and Tilia cordata, while L. lobificans was associated w…
Microfungal community structure in anthropogenic birch stands in central Finland
2002
We describe the soil microfungal communities in 30-year-old birch (Betula pendula Roth) stands planted either on former spruce forest soil (BS) or on former arable soil (BF) and compare these with the soil microfungal communities in spruce forests (S), arable fields (F) and old deciduous forests (D). Fungi were isolated from 0- to 3-cm and 3- to 6-cm samples collected in September 1997 and May 1998. Principal components analysis differentiated fungal communities in the S and BS sites from those in the other site types. The Morisita-Horn index of similarity indicated that fungal communities in the F and BF sites were less similar to those in the other site types. Fungal communities of the BS…
La Betulla dell’Etna: uno studio multidisciplinare sui fattori di deperimento della specie
2018
La betulla dell’Etna (Betula aetnensis Rafin), è una delle specie arboree che durante le ultime glaciazioni si è spinta verso sud e dove oggi costituisce popolazioni pressoché relitte localizzate esclusivamente in Sicilia sulla sommità dell’Etna. I betulleti sono presenti sui versanti orientali ed occidentali dell’Etna, ad un’altitudine compresa tra 1.400 e 2.000 m s.l.m. Si tratta di popolamenti pionieri che colonizzano substrati vulcanici inalterati e/o poco evoluti dove costituiscono a volte dei piccoli boschi puri o misti a pino laricio. Questi boschi in passato erano sottoposti a ceduazioni, che dal 1987 non sono state più eseguite a seguito della istituzione del Parco Regionale dell’E…
Āra bērzs Betula pendula ekosistēmu pakalpojumu kontekstā Latvijā
2015
Maģistra darba mērķis ir novērtēt āra bērza Betula pendula kā ekosistēmas komponenta sniegtos pakalpojumus Latvijā. Tā kā Latvija ir īpaši bagāta ar meža resursiem un koksnes eksports ir viens no galvenajiem valsts ekonomikas ienākumu avotiem, šā darba autors analizē iespējamos šīs koku sugas sniegtos ekoloģiskos pakalpojumus, īpašu uzsvaru liekot uz bērza kā ekosistēmas komponenta ilgtspējīgas izmantošanas nosacījumiem, kā arī izceļot tā nozīmi ekosistēmas bioloģiskās daudzveidības nodrošināšanā. Darbā tika analizēti iegūtie dati, lietojot kopējās ekonomiskās novērtēšanas, aprēķināšanas un tradicionālās vides vērtēšanas metodes. Pamatojoties uz pētnieciskā darba rezultātiem pētnieciskā dar…