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1.
Gunnar Thelin Ulrika Rosengren Ingeborg Callesen Morten Ingerslev 《Forest Ecology and Management》2002,160(1-3):115-125
Atmospheric deposition of N and S appears to have caused nutrient imbalance in Norway spruce stands in southern Sweden. This calls for a change of forest management to procedures that promote nutrient balance. Studies have shown lower soil acidity in Norway spruce/deciduous mixed stands than in spruce monocultures, but the tree nutrient status in such mixtures has not been much investigated so far.
The nutrient status of Norway spruce foliage and top mineral soil chemistry in monocultures and in stands mixed with beech, birch, or oak was investigated through paired comparisons on 30 sites in southern Sweden (27 sites) and eastern Denmark (three sites). In total, 45 mixed stands and 34 pure stands were included in the study.
Spruce needles from mixed stands had higher concentrations and ratios to N of K, P, and Zn than needles from pure spruce stands. Among the mixed stands, the K status appeared to be positively correlated with the percentage of deciduous tree basal area. Soil samples from mixed stands had a higher Mg concentration, base saturation, and BC/Al ratio than soil samples from pure stands. The spruce needle nutrient status was comparable in pure stands on fertile sites and in mixed stands on poor sites. We did not detect any differences in spruce tree growth between pure and mixed stands.
This paper discusses possible reasons for a positive effect on the tree nutrient status in mixed-species stands and the possibility of using mixed-species stands as a forest management procedure to avoid nutrient imbalance. 相似文献
2.
Conventional tillage winter wheat (Triticum aestivum) (WW)–summer fallow reduces soil productivity and increases soil erosion. Conservation tillage management, together with intensive cropping may have the potential to reverse these sustainability concerns. The objective of this study was to determine the effects of conventional tillage (CT) and no-tillage (NT) systems on grain yield of long-term annual cropping of monoculture WW, spring wheat (SW), and spring barley (Hordeum vulgare) (SB) grown with or without fertilizer, in the Pacific Northwest region of the USA. In unfertilized crops, grain yield of WW, SW, and SB was 15%, 25%, and 50% higher, respectively, in CT than in NT plots, an indication of the involvement of yield limiting factors under the NT cropping system. When fertilized, there were no significant differences in grain yield of WW. Yields of SW and SB, however, remained 21% and 15% higher, respectively, in CT than in NT, an indication that factors other than fertility were involved. These results suggest that in order for NT management to be widely adopted by area growers, the yield-limiting factors need to be addressed. 相似文献
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S. K. Garg 《Aquaculture International》1996,4(2):143-155
In order to assess the possibilities of utilizing drainage effluents (salinity range 5.0–12.5), fish culture experiments were carried out. Experiments on polyculture using cow dung (24 000 kg ha–1 y–1) as pond fertilizer were conducted at five different salinity levels (0.3–8.5). Studies have revealed that carp perform well in salinities up to 7.5 and reasonably high fish production has been obtained. Even though the ponds had a high trophic status, higher salinities ( > 7.5) appear to repress fish growth probably due to low dissolved oxygen (DO), high BOD and high NH4-N. Experiments on monoculture of common carp (Cyprinus carpio) conducted at two different salinity levels (0.3–0.9 and 6.0–7.0) using four different organic fertilizers (cow dung at 24 000 kg and 20 000 kg, poultry at 1500 kg, duck at 6000 kg and sheep/goat at 1500 kg ha–1 y–1) have revealed the highest fish growth to be in poultry-treated ponds, followed in decreasing order by duck and sheep/goat wastes. Similar trends in fish production were observed both in fresh- and salt-water ponds. However, fish production was lower in ponds having higher salinities ( > 7.5). Nevertheless, these studies indicated that inland saline waters can be utilized for fish culture. With minor modifications in the existing technology of fish culture in stagnant freshwater fish ponds, animal wastes could be used to fertilize brackishwater fish ponds. 相似文献
6.
Amphimictic diploid (2n), induced triploid (3n) and meiotic gynogenic (MeiG) tench populations were established in 1998 by
mass propagation. After separate nursing, fish were group-marked by freeze branding and 200 specimens per population were
stocked into an experimental earthen pond for communal test until present. Parasitological and haematological (haemoglobin
content Hb, haematocrit PCV and differential leukocyte count) examinations were performed every spring and autumn in the 2+
category, once sex could be registered macroscopically. Altogether 9 genera and/or species of parasites were detected on skin,
7 genera and/or species on gills, 1 genus in eye and 1 species in gut. The highest invasion extensity was recorded in the
MeiG tench in the majority of examinations till the age of 4+. The courses of PCV and Hb values for 2n and MeiG populations
showed high similarity while those for 3n population were slightly decreased and sex-related differences proved to be insignificant
within populations in the majority of examinations. Differential leukocyte counts showed significant differences (p<0.05) of 3n vs. 2n and/or MeiG considering lower proportions of lymphocytes and higher proportions of segmented neutrophils
in the majority of cases. 相似文献
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On the basis of a long-term field experiment with a progessive monoculture of wheat carried out on the research station Hohenschulen (University of Kiel), the yield reaction of wheat in monoculture was analysed with help of a multiple regression approach.
The mean yield of several years declines till the third resp. fourth crop, it increases later ('decline-effect' in the larger sense) without reaching the initial level however.
The weather considerably influence the absolute yield level as well as the yield trend in dependence upon the number of successive wheat crops. Interactions between yield and soil conditions are only slightly marked if the absolute yield is considered. The yield components, however, react differently according to the soil conditions.
Crop management measures such as the choice of varieties and the application of BCM-fungicides or N-fertilization were only able to reduce yield losses, but not to prevent them. 相似文献
The mean yield of several years declines till the third resp. fourth crop, it increases later ('decline-effect' in the larger sense) without reaching the initial level however.
The weather considerably influence the absolute yield level as well as the yield trend in dependence upon the number of successive wheat crops. Interactions between yield and soil conditions are only slightly marked if the absolute yield is considered. The yield components, however, react differently according to the soil conditions.
Crop management measures such as the choice of varieties and the application of BCM-fungicides or N-fertilization were only able to reduce yield losses, but not to prevent them. 相似文献
8.
Carlos R. Fonseca Gislene Ganade Ronei Baldissera Carlos R. Boelter Lucas M. Campos Vanda S. Fonseca Fernando Joner Ana M. Leal-Zanchet Alex S. Mesquita Claudia P. Paz Fabio N. Piovensan Anamaria Stranz Emerson M. Vieira 《Biological conservation》2009,142(6):1209-31
Since pristine Atlantic Forest remnants are vanishing, and biological reserves are in short, conservation of biodiversity will largely depend on proper management of the anthropogenic matrix. Here, we test (1) the effectiveness of ecologically-managed tree monocultures in maintaining Araucaria Forest biodiversity, (2) how this effectiveness change among taxa, and (3) we discuss management principles that can be used by the forestry industry in order to contribute positively to biodiversity conservation. The study was conducted in the São Francisco de Paula National Forest, southern Brazil, an environmental mosaic composed mostly of patches of Araucaria Forest and ecologically-managed monocultures of Araucaria, Pinus and Eucalyptus. Using standardized sampling methods in these four main habitats, we have recorded the richness and species composition of small mammals, birds, leaf-litter frogs, butterflies, galling insects, spiders, opiliones, flatworms, woody plants, epiphytic angiosperms, epiphytic ferns, lichens, and fruit-body producing fungi. Overall, we recorded 506 species in Araucaria Forest, 181 (36%) of which were exclusive of this habitat while 325 (64%) could be found in at least one monoculture. Distribution patterns of species richness and number of records across taxonomic groups showed that a large biodiversity can be found inside ecologically-managed plantations of Araucaria, Pinus, and Eucalyptus. For all studied taxa, except for epiphytic angiosperms and fruit-body producing fungi, more than half of the Araucaria Forest species could be found living on monocultures. We discuss how the actual management practices of the forest industry can be improved to contribute positively to the conservation of the Atlantic Forest biodiversity. 相似文献
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不同大豆品种幼苗叶片光合及叶绿素荧光 特性对套作遮荫的响应 总被引：12，自引：3，他引：9
选用4个耐荫性有差异的大豆品种为材料,通过与单作比较,研究了不同大豆品种幼苗叶片光合及叶绿素荧光特性对套作遮荫的响应差异。结果表明,套作遮荫提高了大豆叶片叶绿素含量、总叶绿素与类胡萝卜素比值（Chl(a+b)/Car）、胞间二氧化碳浓度（Ci）、水分利用效率（WUE）、叶片初始荧光（Fo）、PSⅡ有效光化学量子产量（Fv′/Fm′）和实际光化学效率（ΦPSⅡ）;使叶绿素a与叶绿素b比值（Chla/b）、类胡萝卜素(Car)含量、净光合速率（Pn）、气孔导度（Gs）、气孔限制值（Ls）、蒸腾速率（Tr）、PSⅡ最大光化学量子产量（Fv/Fm）、光化学荧光猝灭系数（qP）、非光化学荧光猝灭（NPQ）呈减小趋势。套作遮荫降低了大豆地上部分干物质积累量,其干物质积累量与Pn呈极显著正相关。耐荫性相对较好的材料,如贡选1号和南豆12在套作遮荫下Pn下降较少,且有着相对较高的Chlb、Car分子组成比例、Fo和Fv/Fm。 相似文献
10.
Jie Song Wei Wei Qin Yao 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2017,67(8):730-736
Experiments were conducted to study the inhibitor factors present in suppressive soil that suppressed the soybean cyst nematode (SCN) in the black soil fields with 21 years continuous cropping of soybean (SSSS) and 3 years continuous cropping of soybean followed by 1 year corn (SSSC). Compared with the SSSC field, the densities of SCN significantly (P?Fusarium equiseti, Pochonia chlamydosporia and Purpureocillium lilacinum were isolated from cysts, eggs and J2 of SCN and soil in SSSS and SSC field. The population density of these parasitic fungi was significantly (P?P. chlamydosporia was higher than other fungi. Real-time PCR was used to test genomic DNA of P. chlamydosporia in SSSS and SSC field soil. The mass of genomic DNA and the population density of P. chlamydosporia were significantly (P?P. chlamydosporia, may play an important role in the suppression of SCN population in the suppressive soil. 相似文献