共查询到20条相似文献，搜索用时 93 毫秒
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国营武冈林场始建于1954年8月，位于武冈市城西南部，由雪峰山脉的云山和夫子山两大山地组成，总面积12万余亩，是湖南省最早组建的林场之一。建场40年来，坚持“以林为主，多种经营，综合利用，全面发展”的方针，取得了巨大的成就。一是林业生产大发展，将荒山秃岭建成了规模宏大的林业基地。建场前，仅有天然来灌木、杉木残次林和榆竹林2万多亩，其余都是荒山。建场后，林场建设者们发扬愚公移山精神，艰苦奋斗，大造林，造大林，累计人工造林10．9万亩，保存面积9．252万亩，采伐迹地造林3．432万亩。抚育间伐中幼林6万亩，不仅绿化了大… 相似文献
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吴建业 《绿色中国(A版)》2014,(10)
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水是生命之源，没有水就没有生命，尽人皆知。
我的家乡万源。万源，万水之源，提起她，人们立刻就会憧憬龙潭河风光的神秘，向往大竹河漂流的浪漫，殊不知那些风光却远离城区百公里之外，至于流经城区的母亲河--后河，就是另一番模样了。
据太平县志记载，后河发源于庙坡乡白龙洞。万水之源指的就是这里。 相似文献
水是生命之源，没有水就没有生命，尽人皆知。
我的家乡万源。万源，万水之源，提起她，人们立刻就会憧憬龙潭河风光的神秘，向往大竹河漂流的浪漫，殊不知那些风光却远离城区百公里之外，至于流经城区的母亲河--后河，就是另一番模样了。
据太平县志记载，后河发源于庙坡乡白龙洞。万水之源指的就是这里。 相似文献
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最大的陆生动物──珍稀的象沈钧远在五万年前，在葱绿的黄河两岸遍布着大象的足迹，到距今三千多年前，在河南地区还群居着大量野象。但由于人类大面积毁林，黄河两岸失去植被，大象的分布区大为缩减，大象被迫越过黄河，跨过长江。一直到明末，在湖南、两广和云南一带，... 相似文献
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A major problem for small farmers in the semi-arid tropics is the chronic shortage of fodder for draft animals. Leucaena leucocephala has improved productivity in many places in India and in various cropping systems, usually as either a pure crop or in a
hedgerow alley-cropping configuration. Mixed cropping with arboreal forms is seldom seen. For off-season fodder production,
hedgerows have the disadvantage of being open to unmanaged browsing when unfenced (as is usual). Arboreal forms are generally
far less vulnerable.
In this paper, the components of production of sorghum and arboreal Leucaena are measured under different intensities of canopy lopping. The most productive management system of those examined was pollarding
of the Leucaena at the time of under-sowing with sorghum. In a year with less than 50% of average seasonal rainfall, this system gave a yield
of 4.6 tonnes/ha/yr fresh wt fodder and 3.8 tonnes/ha/yr dry wt. of fuel harvests, while increasing the standing crop of wood
by 1.8 t/ha/yr and retaining a yield of sorghum grain equivalent to 46% of pure sorghum cropping; the LER of this system was
1.35.
Cash values of the alternative management systems were estimated, including the discounted Net Present Value of the standing
crop of timber. Maximum value was attained with unlopped pure crop Leucaena followed by pollarded Leucaena with sorghum; pure crop sorghum achieved a lower value.
These results demonstrate both the high productivity of Leucaena/sorghum based systems, and the stability of production even in poor rainfall conditions. Pollarding transferred the high
future value of Leucaena timber to the present value of sorghum grain and fuelwood. 相似文献
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Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic
or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts
(stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea
(Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content
as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest
N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized
to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea,
largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for
N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant
components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N
released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures
were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality
components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in
the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols.
Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest
age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its
components are mixed. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
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Marcelo de Carvalho Alves Fábio Moreira da Silva Edson Ampélio Pozza Marcelo Silva de Oliveira 《Journal of pest science》2009,82(2):137-148
The advent of Precision Agriculture has made possible the analysis of complex spatial patterns of plant disease epidemiology
considering statements of integrated disease management. The objective of this work was to use geostatistics, statistics and
geographical information systems to characterize the structure and magnitude of spatial dependency of rust (Hemileia vastatrix) and brown eye spot (Cercospora coffeicola) incidence and severity in coffee agroecosystem cultivated with Catuai Vermelho IAC-99 (Coffea arabica L.). Evaluations of incidence and severity of rust and brown eye spot were accomplished at 67 georeferenced points arranged
in 6.6202 ha of coffee crop, in the years of 2005, 2006 and 2007. Exponential models of covariance enabled the characterization
of the magnitude and structure of rust and brown eye spot spatial variability in the evaluated dates. Ordinary block kriging
presented satisfactory performance to map rust and brown eye spot outbreaks based on kriging error coefficients. Kriged maps
enabled the visualization of intensity of rust and brown eye spot in each evaluation date. Assessments of incidence and severity
presented highly statistical correlation based on linear regression models, also confirmed by the spatial variability of kriging
maps. Kriging maps of rust and brown eye spot enabled to observe that intensity of disease was dispersed in foci patterns
along the coffee plantation, indicating that the current strategy of disease control based in total area may be replaced by
site specific disease management, with less environmental impact and sustainability of coffee crop, according to statements
of integrated disease management and precision agriculture. 相似文献
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《Journal of Sustainable Forestry》2013,32(2-3):133-146
Abstract A sustainable use of forests may be conceived of differently by different scientific disciplines. An underlying definition of sustainability is therefore central to the understanding of any analysis on the subject. This paper approaches the idea of sustainability from an economic perspective. The interpretation of sustainability in terms of concepts such as efficiency, equity and welfare are initially described. Empirical research aiming at obtaining basic elements of economic sustainability analyses is subsequently outlined. Finally, the implications for applied welfare and sustainability analysis at different economic and geographical levels of aggregation are discussed 相似文献
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Nutrient and hydrologic cycles in harvested native forests in southern Australia are largely balanced. For example, we have
little or no evidence of any decline in nutrient capital or availability in harvested forests. Short-term and small-scale
reductions in evapotranspiration due to loss of leaf area after harvesting are adequately balanced at the landscape scale
by large areas of regenerating or older-age forest. In contrast, agricultural systems on similar soils are a) dependent on
large inputs of fertilisers to maintain growth and b) frequently subject to increasing salinity and waterlogging or other
forms of degradation. The large-scale replacement of long-lived communities of perennial and often deep- rooting native species
with annual crops or other communities of shallow-rooting species might be better managed within the framework of knowledge
developed from studies of native plant communities. However, application of such a mimic concept to systems of low natural
productivity is limited when agricultural systems require continued high productivity. Nonetheless, the mimic concept may
help in developing sustainable management of agriculture on marginal lands, and contribute to the nutritional resilience of
agroecosystems. Relevant characteristics for mimic agroecosystems in south western Australia include: high species diversity,
diversity of rooting attributes, utilisation of different forms of nutrients (especially of N and P) in space and time, and
the promotion of practices which increase soil organic matter content.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Native woody species regeneration in exotic tree plantations at Munessa-Shashemene Forest,southern Ethiopia 总被引：2，自引：0，他引：2
Regeneration of native woody species was studied in the plantations and the adjacent natural forest at Munessa-Shashemene Forest Project Area, Ethiopia. The aim of the study was to test the hypothesis that tree plantations foster regeneration of native woody species. A total of 60 plots, having 10 × 10 m area each, were studied in monoculture plantations of 4 exotic species (Cupressus lusitanica, Eucalyptus globulus, E. saligna, Pinus patula) and an adjacent natural forest. Ages of the plantations ranged between 9 and 28 years. Soil seed bank analysis was also undertaken from soil samples collected in each of the 60 plots to examine the similarity between the soil seed flora and aboveground vegetation. A total of 56 naturally regenerated woody species were recorded beneath all plantation stands with densities ranging between 2300 and 18650 individuals / ha in different stands. There was a significant difference among plantation stands with regard to understorey density (standard deviation: 4836 ± 1341). Vegetation diversity was assessed through analyses of floristic composition, species richness and abundance. Generally, seedling populations were the most abundant components of the regeneration in most of the plantation stands, forming 68 % of the total regeneration count in all stands. A total of 77 plant species represented by 44 herbs, 13 woody species, 8 grasses and 12 unidentified species were recorded in the soil seed bank from all stands. Similarity between the soil seed bank and aboveground flora was very low implying that the role of soil seed banks is negligible rather dispersal plays an important role in the process of regeneration. These results support the concept that forest plantations can foster the regeneration of native woody species, thereby increasing biological diversity, provided that there are seed sources in the vicinity of the plantations. 相似文献
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Trees and shrubs as sources of fodder in Australia 总被引：2，自引：0，他引：2
E. C. Lefroy P. R. Dann J. H. Wildin R. N. Wesley-Smith A. A. McGowan 《Agroforestry Systems》1992,20(1-2):117-139
Experience with browse plants in Australia is briefly reviewed in terms of their forage value to animals, their economic value to the landholder and their ecological contribution to landscape stability. Of the cultivated species only two have achieved any degree of commercial acceptance (Leucaena leucocephala and Chamaecytisus palmensis). Both of these are of sufficiently high forage value to be used as the sole source of feed during seasonal periods of nutritional shortage. Both are also leguminous shrubs that establish readily from seed. It is suggested that a limitation in their present use is the reliance on stands of single species which leaves these grazing systems vulnerable to disease and insects. Grazing systems so far developed for high production and persistence of cultivated species involve short periods of intense grazing followed by long periods of recovery. Similar management may be necessary in the arid and semi-arid rangelands where palatable browse species are in decline. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(4):377-384
The objective of this study was to predict the amount and the distribution of compression wood (CW) within a Norway spruce [ Picea abies (L.) Karst.] plank based on green plank curvature. The findings indicated a possibility of predicting the longitudinal distribution of CW from the green plank curvature. Areas free from CW showed a typical concave shape in relation to the centre of the log, while CW was present when a convex shape was shown. The larger the magnitude of convex curvature, the higher the concentrations of CW that could be found, and a larger fraction of dried planks was rejected due to excessive warp. This study also determined what information can be used to eliminate areas of high concentrations of CW by cutting and how cutting affects the grading results with respect to warp. Over 50% of the plank length showing a high concentration of CW (>30% of the cross-cut volume) was successfully cut off. Cutting strategies based on predicted CW concentrations resulted in a 10-40% increase in accepted plank length. 相似文献