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The contribution shows changes in the phosphorus and nitrogen status in long-term investigated spruce stands in the Lu?ické, the Jizerské and the Orlické Mts. on the border between the Czech Republic and Germany and Poland. During the 11 evaluated years, low phosphorus concentrations were measured, often below the deficiency limit 1.2 mg P/g, and an N/P ratio exceeding the optimal range (6–12), primarily in the second needle-year class. Values of an N/P ratio of between 12 and 18 in the Jizerské Mts. and of between 12 and 27 in the Lu?ické Mts. were discovered. A low phosphorus concentration below the 10 mg·kg?1 was also detected in the mineral soil horizon. Temporal changes of N/P ratio (increase) and of P concentration (decrease) in the needles are significant for the spruce stands that are in the Orlické Mts. In the Jizerské Mts. and the Lu?ické Mts., there is fluctuation during evaluated period without any clear trend.  相似文献   

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The highest deforestation and forest degradation rates in Africa occur in the dry forests and woodlands where pressure for land is increasing, poverty is rampant, livelihood options are few and climate change effects are severe. This paper examines factors that cause land and forest degradation in the Sahel and dry forests and woodlands of eastern and southern Africa and highlights some successful restoration practices, technologies and approaches. In the Sahel, enclosures are used to protect young growing trees while in East Africa enclosures are implemented on degraded land as a mechanism for environmental rehabilitation with a clear biophysical impact. The choice of techniques for rehabilitating specific degraded areas depends first on the priorities and management objectives of stakeholders followed by the costs and benefits associated with available rehabilitation techniques and the economic, social, and environmental values of the land resources in their current and desired future states. In the Sahel, sustainable land management is considered to be an imperative for their sustainable development and the practices include soil and water conservation activities and structures. In all regions, natural forest rehabilitation has used both natural and assisted regeneration to promote the growth of especially indigenous species through coppice regrowth and root suckers rather than seeds. Assisted regeneration was especially prevalent in the Sahel where indigenous tree species have been identified to dominate the degraded sites during early stages of secondary forest succession. The success of any rehabilitation activities depends on community-based natural resources management. In addition, the forest policies and their related policies need to be enabling in order to address issues of concern, including (1) the full participation of communities, (2) clear land and tree tenure and (3) equitable benefit sharing.  相似文献   

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In this article, we assessed the reproduction rates of the generalist pteromalid parasitoids Anisopteromalus calandrae and Lariophagus distinguendus on the coleopteran pest species, Sitophilus oryzae and Rhyzopertha dominica, when these hosts were offered together under environmental conditions reproducing spring or early summer. These species had proved to be the most suitable hosts in terms of parasitoid progeny production for both parasitoid species in no choice experiments in previous studies. Trials with A. calandrae and L. distinguendus had lower pest emergence in the parasitoid treatment when compared to the control for S. oryzae. However, for R. dominica, there was no difference between treatments for either parasitoid species. Pest reduction levels reached by the two parasitoids were caused by parasitism effects together with other parasitoid-induced mortality causes, which included host feeding and unsuccessful parasitism. The most preferred host under the conditions tested for both parasitoid species was S. oryzae. The parasitoid L. distinguendus decreased grain loss significantly more than A. calandrae thanks to a greater reduction of pest population. Product loss in terms of reduction of the medium (brown rice) weight was always higher in the control treatments.  相似文献   

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ItiswellknownthatthecharacteristicsofChina'ssituationsareoverpopulation,poorfoundation,lowculturalandscienceandtechnologylevels,lackandunevendistributionofresources,andlowrankingofpercapitaGDP.Owingtothebackwardofscienceandtechnologyandmanagement,therelativelyshort-suppliedresourceshasnotbeenutilizedproperly.Takingforestryforexample,thecoverisonly13.92%,lowerthantheworld'saverageof22%;China'spercapitaaverageofforestlandislessthan0.13ha,whiletheworld'saverageis1.lha;Chinaisalsolowinforestqual…  相似文献   

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  • ? The Reineke Stand density rule relating stem numbers to the quadratic mean diameter is generally used as a reference for modelling maximal stand density.
  • ? The linearity of this relationship after double logarithmic transformation is generally assumed, but it must be questioned for untouched stands and stands with a conventional thinning regime. Curvilinearity is demonstrated for some spruce and beech stands in Switzerland and shown to be statistically representative. This relationship is independent of the site index. It can be interpreted as a change in mortality in young stages mainly due to competition and in older stages more to ageing.
  • ? A more accurate estimation of the maximal stand density needs to take into account the important variation around the mean course, known as the yield level. A simple method to assess the yield level of any stand regardless of whether it is thinned or not is presented, based on estimating the effect of a stand opening on the basal area.
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    Decaying mangrove detritus plays a significant role in nutrient cycling and fueling in both the forests and aquatic habitats where the detritus stems from estuarine and coastal food webs.Detrital decay rates partly depend on the type of detritus,but most studies have thus far focused on leaf litter decay and decomposition,whereas other detrital sources(except for roots)have largely been ignored.We compare the decay rates of Rhizophora apiculata and Xylocarpus granatum non-leafy detritus(flowers,propagules,stipules,and twigs)with mangrove leaf litter in field studies,using litter bags during the dry and the wet seasons in the tropical mangrove forest of Sibuti,Sarawak,Malaysia.We observed higher microbial decay rates of stipules,flowers,propagules,and twigs for both the R.apiculata and X.granatumduring the wet months.By contrast,leaf decay rates were higher during the dry months.Decay rates depended on the lignin content of the detrital sources of both species,both during dry and wet months.Accordingly,the half-life(T0.5)and 95%lifespan(T0.95)of non-leaf materials(flowers,propagules,stipules and twigs)for both species were remarkably longer than those of leaf litter.Slowly decaying non-leafy detritus may play a significant role in nutrient and carbon cycling over longer time,when leaf litter is either being decomposing rapidly and/or being washed away by tidal flush and river runoff.Hence,non-leafy(flowers,propagules,stipules and twigs)detritus should be taken into account when budgeting organic matter turnover in mangroves.  相似文献   

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    The beginning of the land rent theory is closely related to the German forest economists Friedrich Wilhelm Leopold Pfeil and Johann Christian Hundeshagen (1828). It was further developed by Gottlob König (1864), Johann Heinrich v. Thünen, Max Robert Preßler, Gustav Heyer, Max Endres and in particular by Martin Faustmann (1849). His 1849 published and well known formula may be seen as the center of the land rent theory. However, the application of this concept demanded a considerable change of forest management practice due to the reduction of usual rotations and stocking density. Eventually, the land rent theory conflicted with the principle of sustained yield which had become the central idea of forestry in Germany in the 19th century. Since forestry under German conditions did not start as an investment on bare forest land, but had to manage existing forests under the principle of sustainability, the theory of the highest revenue seemed to be a more appropriate guideline for forestry. However, the maximization of the highest revenue assumed a marginal interest rate of 0% because the time span between input and output was not considered. Besides that, this principle also conflicted with the reality of forestry, because the scarcity of financial funds was not regarded. So far, both theories have not delivered solutions useful to real forest economic decision problems in Germany. Using an example from Lower Saxony, it is demonstrated that considering the objective of sustainability leads to results which are in accordance with the reality and the economic theory.  相似文献   

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    Marquis  Benjamin  Bergeron  Yves  Simard  Martin  Tremblay  Francine 《New Forests》2021,52(6):1079-1098
    New Forests - Permanent landscape attributes such as topography (elevation [m]) and microtopography (local variation in elevation [cm]) can increase the risk of cold air drainage down-slopes and in...  相似文献   

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    ABSTRACT

    Sweden is one of the most forested countries in Europe, and it has one of the highest shares of productive forest. Production in forestry is largely reliant on the private non-industrial forest owners, who own half of the forest land. As in many countries, however, forest ownership is changing towards a higher extent of urban, female or non-forestry-background owners. This poses a challenge for the forestry services sector, mainly forest owners’ associations and companies, but also broadly the sector at large. By exploring the sales and marketing processes, this paper analyses the service logics and strategies of Swedish forestry under changing forest ownership, drawing on an interview study covering all the large actors in the Swedish forestry sector. The study illustrates an increased focus of forestry organizations on services from a strategic and managerial perspective, in customer-oriented relationship development and in value creation and sales processes, specifically in order to manage “new” forest owners and the demand of forest industries. The results highlight the domination of service logics associated with timber production and the challenges for the service market and the provision of diversified services to forest owners.  相似文献   

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    The global spread of the Asian tiger mosquito Aedes albopictus, an urban pest as well as a vector for arboviruses, is a threat for public health. As control measures include the use of insecticides such as the pyrethroid λ-cyhalothrin, it is crucial to assess their efficiency and their potential impact on the biodiversity especially under climate change conditions. To evaluate the environmental risk, biotests are well established for non-target organisms but not yet for mosquitoes. We therefore developed a full-lifecycle biotest for mosquitoes kept under quarantine conditions based on the OECD guideline 219. Therewith we tested the effect of temperature and nutrition on the ecotoxicological response to λ-cyhalothrin on the mosquitoes Ae. albopictus and Culex pipiens by assessing sublethal and life history parameters. The efficiency of λ-cyhalothrin decreased in both mosquito species with increasing temperature and changed with feeding protocol. At effective concentrations for potential mosquito control in surface waters, λ-cyhalothrin poses a high risk for indigenous aquatic key role species inhabiting the same microhabitats. Those aspects should to be taken into account in vector control strategies.  相似文献   

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    Intheprocesofbuildingasocialistmarketeconomy,itisimportanttostrengthenthesocialservicesystemincommunityforestrytosafeguardth...  相似文献   

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    The practical occasions for isocyanate bonding to woodare often that of heat, high moisture or rich water.When isocyanate reacted with functional groups inwood, such as hydroxyl groups, it formed thecarbamate that fulfils isocyanates powerful chemicalbonding. Meanwhile, it reacted with water or its vapourand formed polyurea, which is a completing reactionwith that of forming carbamate(Rowell, et al., 1981).As a result, this completing reaction correlates to thefinal bonding performance of iso…  相似文献   

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    《林业研究》2008,19(1):F0004-F0004
    The Hardwood Tree Improvement and Regeneration Center (HTIRC), led by Dr. Charles H. Michler, is a collaborative effort between Purdue University, USDA Forest Service, State of Indiana, and the hardwood forest industry. Additional funding partners are the Van Eck Forest Foundation, National Science Foundation, ArborAmerica Inc., Steelcase Inc., Indiana Hardwood Lumbermen's Association, National Hardwood Lumber Association, Indiana Forestry and Woodland Owners Association and Walnut Council. The Center employees eight Ph.D. principal investigators who specialist in genetics and tree improvement, tree physiology, silviculture, entomology, nursery management and plantation establishment, and outreach. HTIRC's research and development is focused on fine hardwood species (Juglans, Quercus, Castanea, Prunus and Fraxinus) native to the central hardwoods region of the USA and the Center is providing graduate education to more than 22 MS and Ph.D. students Recent accomplishments include development of: 1) seed zones and genetic transformation protocols for Juglans nigra, 2) vegetative propagation methods for Prunus serotina, and 3) cold hardiness and advance mineral nutrition guidelines for hardwood nursery stock  相似文献   

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    IssuesRelatingtoForestryandtheMitigationofPovertyByYangShuncheng1.DistributionofforestsandtheoccurenceofpovertyChina′svastmou...  相似文献   

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    Present research on the composition and application of lac   总被引:1,自引:0,他引:1  
    Lac is a natural polymer with atoxigenic, renewable, and naturally degradable characteristics. Nowadays, more and more attentions are paid to environment protection and resource conservation, so it has great significance to study the composition and application of lac. The paper summarizes the research of lac composition and emphasizes on the present research of lac resin. The applications of lac are also introduced. In addition, some suggestions are proposed, which is expected to provide some scientific references for further studies of lac.  相似文献   

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