排序方式: 共有55条查询结果,搜索用时 15 毫秒
31.
Peeter Lääniste Juhan Jotildeudu Viacheslav Eremeev Erkki Mäeorg 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(4):330-335
Abstract A five-year investigation on overwintering of winter oilseed rape (Brassica napus L.) cv. Wotan has been carried out in Estonia. Sowing in August was conducted four times at weekly intervals. Seeding rates of 100, 150, and 200 plants m?2, at which respectively 47, 71, and 98 plants overwintered, gave different densities at harvest. A lower plant density (47 plants m?2) produced yields just as high as those with higher density (98 plants m?2). The optimal sowing date was mid August, which gave on average 98 plants m?2 with various plant densities. Those plants also gave higher yield (1748 kg ha?1), compared with the plots sown early or later in August. 相似文献
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Arto Huuskonen Hannele Khalili Erkki Joki-Tokola 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(1):37-44
Abstract A 2×2 factorial design with 32 dairy bulls was used to study the effects of partial replacement of a starchy concentrate with a fibrous concentrate and replacement of rapeseed meal with barley protein as protein supplement on performance of bulls with ad libitum access to a total mixed ration feeding. The two energy supplements were flattened barley (B) and a mixture (1:1 on dry matter (DM) basis) of flattened barley and barley fibre (BF). These were fed with either rapeseed meal or barley protein so that the crude protein content of rations was 162 g kg?1 DM. Replacing half of the barley grain with barley fibre increased (P<0.01) the average DM intake (9.3 kg d?1 versus 9.9 kg d?1), but had no effect on the average live weight gain (1.27 kg d?1). There seemed to be only a minor difference between rapeseed meal and barley protein as protein supplements on animal performance. 相似文献
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This study presents empirical data on regeneration and growth of understory trees and constructs simple models for predicting
these characteristics at various stand structure and post-thinning standing volume levels. The field experiment was established
on a grass/herb mineral soil site in central Finland. Regeneration and understory tree growth data were collected from 24
Norway spruce (Picea abies L.)-dominated mixed substands. Seedlings with heights from 5 to 130 cm were measured in 1996 and 2007. In addition, the annual
height growth of Norway spruce seedlings was measured in 2007. The spatial pattern of the substands varied from clustered
to regular with a decreasing standing volume. Stand complexity was uniform across the range of standing volume. In the 2007
survey, the amount of Norway spruce regeneration increased from approximately 400 to 5,000 seedlings ha−1 when the post-thinning standing volume level was reduced from 230 to 90 m3 ha−1, respectively. Nearly no seedlings were found when the standing volume was over 300 m3 ha−1. The annual diameter increment in Norway spruce understory (dbh < 5 cm) trees decreased, on the average, from 2.3 to 0.3 mm
with an increase in the standing volume level from 90 to 340 m3 ha−1, respectively; their height growth showed also a decreasing trend when the standing volume increased. The results indicated
that a post-thinning standing volume lower than 150 m3 ha−1 with a regular overstory spatial structure provides a suitable environment for regeneration and growth of Norway spruce understory
trees in the studied forest type. 相似文献
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Viktor Finns Jan‐Olof Lill Yvette Heimbrand Martina Blass Timo Saarinen Yann Lahaye Erkki Jokikokko Henry Hgerstrand 《Fisheries Management and Ecology》2020,27(5):490-497
Micro X‐ray fluorescence (µ‐XRF) analysis of otoliths was evaluated as a method to estimate the proportion of stocked one‐summer‐old whitefish Coregonus lavaretus L. in catches of adult fish (n = 20) ascending the River Kemijoki to spawn. Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) analysis was applied as control. Polished otoliths were scanned with µ‐XRF to obtain strontium maps that were used to infer visually the provenance of the whitefish. Thirteen of the fish showed signs of being stocked as one‐summer‐old fingerlings. LA‐ICP‐MS was applied to determine the elemental composition in a spot outside the core of the otolith. The results were largely consistent with the visual inspection of the µ‐XRF mapped otoliths. In conclusion, µ‐XRF mapping successfully identified whitefish stocked as one‐summer‐old fingerlings. The vast majority of whitefish returning to the River Kemijoki to spawn were stocked fish. 相似文献
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Mikael Nordström Jouko Högmander Jukka Nummelin Erkki Korpimäki 《Biological conservation》2003,109(3):359-368
We studied the effects of removing introduced American mink (Mustela vison) on the number of birds breeding on small islands in the Baltic Sea. During autumn 1992-2001 mink were removed from a 72 km2 area, while mink were not removed from a 35 km2 control area. Second removal (125 km2) and control areas (130 km2) were established during 1998-2001. The breeding densities of ringed plover (Charadrius hiaticula), arctic skua (Stercorarius parasiticus), arctic tern (Sterna paradisaea) and rock pipit (Anthus petrosus) increased markedly in the removal areas in comparison to the control areas. Turnstone (Arenaria interpres), common gull (Larus canus) and wheatear (Oenanthe oenanthe) also appeared to increase. Two species already extinct in one of the removal areas, razorbill (Alca torda) and black guillemot (Cepphus grylle), returned to breed in the area. Breeding densities of great black-backed gull (Larus marinus), oystercatcher (Haematopus ostralegus) and white wagtail (Motacilla alba) were unaffected. We conclude that it is possible to remove feral mink from large archipelagos with many small islands, and that mink removal increases the breeding densities of many bird species in this habitat. 相似文献
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Matti Maltamo Annukka Pesonen Lauri Korhonen Jari Kouki Mikko Vehmas Kalle Eerik?inen 《中国林学(英文版)》2015,(2):143-154
Background: The occurrence of aspen trees increases the conservation value of mature conifer dominated forests.Aspens typically occur as scattered individuals among major tree species, and therefore the inventory of aspens is challenging.Methods: We characterized aspen populations in a boreal nature reserve using diameter distribution, spatial pattern, and forest attributes: volume, number of aspens, number of large aspen stems and basal area median diameter. The data were collected from three separate forest stands in Koli National Park, eastern Finland. At each site, we measured breast height diameter and coordinates of each aspen. The comparison of inventory methods of aspens within the three stands was based on simulations with mapped field data. We mimicked stand level inventory by locating varying numbers of fixed area circular plots both systematically and randomly within the stands. Additionally, we also tested if the use of airborne laser scanning(ALS) data as auxiliary information would improve the accuracy of the stand level inventory by applying the probability proportional to size sampling to assist the selection of field plot locations.Results: The results showed that aspens were always clustered, and the diameter distributions indicated different stand structures in the three investigated forest stands. The reliability of the volume and number of large aspen trees varied from relative root mean square error figures above 50% with fewer sample plots(5–10) to values of25%–50% with 10 or more sample plots. Stand level inventory estimates were also able to detect spatial pattern and the shape of the diameter distribution. In addition, ALS-based auxiliary information could be useful in guiding the inventories, but caution should be used when applying the ALS-supported inventory technique.Conclusions: This study characterized European aspen populations for the purposes of monitoring and management of boreal conservation areas. Our results suggest that if the number of sample plots is adequate,i.e. 10 or more stand level inventory will provide accurate enough forest attributes estimates in conservation areas(minimum accuracy requirement of RMSE% is 20%–50%). Even for the more ecologically valuable attributes, such as diameter distribution, spatial pattern and large aspens, the estimates are acceptable for conservation purposes. 相似文献
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A new girth band for measuring stem diameter changes 总被引:2,自引:0,他引:2
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Erkki Mäkinen Maarit Korhonen Eeva-Liisa Viskari Seija Haapamäki Maaret Järvinen Li Lu 《Water, air, and soil pollution》2006,171(1-4):95-110
Soil contamination by hazardous heavy metals from various sources is a great concern nowadays. The need for studying contaminated sites has led to an increasing use of various analytical techniques in the laboratory or in the field, for investigation or control of the restoration operations ofpolluted sites. In this study, results using portable field x-ray fluorescence (XRF)-analyzer X-MET 2000 and flame atomic absorption spectrometry (FAAS) are compared to analyze As, Cu and Cr in soil polluted by chromated copper arsenate (CCA)-wood preservatives. Analyses with XRF were done in situ, in difficult, wet conditions, as well as in the laboratory. For the XRF-analysis, two calibrations were available; an empirical calibration, and recently published fundamental parameter calibrations. Comparative analyses were obtained by extracting As, Cr and Cu with aqua regia and analyzing the samples with flame atomic absorption spectrometry (FAAS). The results indicated that in situ analyses with XRF showed more variation in respect to all three elements than measurements made in the laboratory of dried and sieved (mesh size < 125 μm) samples. XRF's empirical calibration turned out to be more consistent with the FAAS analyses than fundamental parameter calibration, and is therefore recommended. Intrusive laboratory analyses with XRF and FAAS in turn showed good correlation with As and Cu results. FAAS also demonstrated high accuracy and precision as did XRF with As and Cu. On the other hand, Cr results showed more variation, and correlation between the different methods was poorer. To increase the reliability of analysis with both methods, careful drying and sieving the samples is recommended. Therefore we conclude that XRF can be used in field analysis, but laboratory analyses are needed to confirm the results. 相似文献
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