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1.
The focus of this study was to investigate the chemical and colour changes occurring at different exposure times on artificially photo-irradiated surfaces of normal and red heartwood in beech in order to understand the mechanisms that cause the changes and to evaluate the possibility of usages of beech not only for energy production purposes. In this sense, surface colour modifications are of crucial importance to define the commercial value of beech wood. The artificial photo-irradiation of the wood samples was performed in a Solar Box, equipped with an ultraviolet filter that cuts off the spectrum at 280 nm. Reflectance spectrophotometry and Fourier transform infrared (FTIR) spectroscopy were used to assess artificial sunlight influence. The experimental data were statistically treated to evaluate their significance. Colour monitoring revealed that wood surface colour undergoes an important variation due to photo-irradiation, occurring within the first 24–48 h. Moreover, it was found that the chromatic coordinates (L*a*b*) in normal wood and in red heartwood tended to similar values after 504 h. FTIR spectroscopy allowed for investigating the rate of photodegradation of wood surface due to oxidation reactions of wood components. The results were validated by statistical analysis applied both to the colorimetric and spectroscopic data.  相似文献   

2.
In Amazonian Ecuador, studies are being realized to intensify fallow periods by grazing African tropical forest type sheep (Red Afro-Colombian X Barbados Black Belly) on Asian tropical forest legume cover forage (Desmodium ovalifolium) under American tropical forest legume fuelwood trees (Inga edulis). The specific approach represents an innovative effort to address the complex problems associated with the pernicious use of less fertile lands by small-scale farmers and graziers in the humid tropics. The technologies developed are closely compatible with traditional socio-cultural patterns. For example, shifting cultivators are encouraged to plant contour strips of legume fuelwood trees in their cassava fields. With the cassava harvest, legume cover forage is planted between the fuelwood trees, to be grazed later by tropical forest sheep. Forage and fuelwood legumes increase soil aeration, organic matter, nitrogen and available phosphorus, control soil erosion and leaching, as well as provide a break in cropping that checks insect, disease and weed build-ups. Tropical forest sheep improve soil fertility by depositing organic matter which stimulates legume/Rhizobium symbiosis and by supplying fecal microorganisms which mineralize crop residues. In addition, tropical forest sheep cause little soil compaction and erosion, produce high quality food protein from legume cover forage, as well as generate cash income, capital and employment for small-scale farmers. Tropical forest sheep on legume forage/fuelwood fallows not only intensify land use under shifting field cultivation, but also form the basis for rehabilitating already degraded lands for further foodcrop production.  相似文献   

3.
Agroforestry with its outstanding variety of systems and technologies has been practiced in all parts of the world since times immemorial. Its worldwide recognition, scientific promotion and application in rural development strategies in the tropics, however, ‘exploded’ with two events: the foundation of the International Council for Research in Agroforestry (ICRAF), 1977 and the Eighth World Forestry Conference in Jakarta, 1978. This is important to be recalled at the occasion of the Ninth World Forestry Congress to be held in Mexico this year. Agroforestry's holistic approach to solving land use problems under prevailing conditions and constraints of different humid, semiarid and mountainous regions has gained importance and produced first remarkable results with regard to increasing the human-ecological carrying capacity. Forestry is gaining from the newly promoted strategies of integrated land use in various ways: less pressure on forest resources and thus less destruction of forest vegetation, additional lands for wood production outside the forest estate, cooperation instead of confrontation with other target groups, and an expanded multiple-use concept increasing the value of marginal forest lands. Agriculture and livestock management are improved by various environmental benefits of the forest component and by the availability of forest products within agroforestry systems. First achievements over the past seven years have been encouraging in many instances. Much more, however, remains to be done in future.  相似文献   

4.

Context

Reliable information on tree stem diameter variation at local spatial scales and on the factors controlling it could potentially lead to improved biomass estimation over pine plantations.

Aims

This study addressed the relationship between local topography and tree diameter at breast height (DBH) within two even-aged radiata pine plantation sites in New South Wales, Australia.

Methods

A total of 85 plots were established, and 1,302 trees were sampled from the two sites. Airborne light detection and ranging (LiDAR) was used to derive slope and aspect and to link them to each individual tree.

Results

The results showed a significant relationship between DBH and local topography factors. At both sites, trees on slopes below 20° and on southerly aspects displayed significantly larger DBHs than trees on steeper slopes and northerly aspects. Older trees with similar heights also exhibited a significant relationship between DBH and aspect factor, where greater DBHs were found on southerly aspects.

Conclusions

The observed correlation between tree DBH and LiDAR-derived slope and aspect could contribute to the development of improved biomass estimation approaches in pine plantations. These topographical variables are easily attained with airborne LiDAR, and they could potentially improve DBH predictions in resource inventories (e.g. stand volume or biomass) and support field sampling design.  相似文献   

5.
The flavonoids content and its composition in Ginkgo (Ginkgo biloba L.) leaves are affected by environmental factors such as temperature and soil moisture. Here we performed experiments in phytotron using 2-year-old Ginkgo seedlings to explore the effects of temperature and soil moisture on flavonoids content, enzymes related to flavonoids biosynthesis such as phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and p-coumarate CoA ligase (4CL), soluble sugar and protein content. We found that temperature and lower soil moisture had significant effects on these parameters. The effects of temperature on flavonoids content, the activity of C4H and 4CL and soluble sugar content were greater than that of soil moisture. The total flavonoid content, the activity of PAL, C4H and 4CL, soluble sugar content were higher in lower temperature regime 15 °C (daytime)/5 °C (nighttime) and lower soil moisture (30–35 % of field capacity), but higher temperature was beneficial to the accumulation of soluble protein. This indicates that increasing of soluble sugar content and the activity of PAL, C4H and 4CL are beneficial to flavonoids biosynthesis and accumulation in the Ginkgo leaves, while increasing of soluble protein is adverse to flavonoids biosynthesis. Because lower temperature and soil moisture are favorable to flavonoids biosynthesis, we can take some silvicultural steps to increase flavonoids production in Ginkgo plantation, such as establishing leaf-harvest plantation at lower temperature zone, reducing irrigating before harvesting leaves.  相似文献   

6.
Field experiments have been carried out to evaluate the potency of the biological control agentBacillus thuringiensis (Dipel), the pyrethroid Fenvalerate and their combinations for the control of the lesser cotton leafwormSpodoptera exigua on soybeans in Qualubia governorate. Molasses was combined with all treatments to enhance their effectiveness. One spray application with either Dipel or Fenvalerate showed an obvious reduction in larval counts ofS. exigua, associated with a significant increase in the crop yield but in varying degrees, in correlation with the tested dose. Treatments with combinations of both biological and chemical insecticides at the lowest tested doses (62 g ofB. t. +50 ml of Fenvalerate/feddan) showed to be highly potential, and caused 2.8 fold increase in the crop yield. It may be recommended that a combination of both preparations may be used for the control ofS. exigua.  相似文献   

7.
Agroforestry Systems Inventory   总被引：2，自引：0，他引：2  
  相似文献   

8.

Context

Mediterranean open woodlands (dehesa) have faced a dual process of intensification and abandonment of grazing which has resulted in alteration of the understory vegetation.

Aims

We analysed the effects of land use changes on the physiological status of holm oak in different open woodlands (dehesa) in southern Iberian Peninsula.

Methods

In an area of extensive grazing, we selected six paired plots (one grazed, one abandoned) and grouped them by habitat types according to understory composition (nearly all monospecific Cistus ladanifer L. shrub or mixed shrub). Six plots of moderate and heavy grazing intensity were chosen within a settled area of livestock use. Shoot growth, macronutrient concentrations and water content were assessed in samples of holm oak leaves.

Results

Abandonment of grazing affected some nutrient concentrations and water content of holm oak leaves, but the effects were different according to habitat type. C. ladanifer shrub reduced N and P concentrations and water content while mixed shrub increased P concentration and water content. High grazing intensity improved shoot growth and leaf N and Mg concentrations.

Conclusion

Extensive grazing could be a useful management tool to enhance growth, nutritional and water status of holm oak in a habitat with limited resources such as Mediterranean open woodlands (dehesa).  相似文献   

9.
A trial demonstrating an establishment and maintenance technique forPinus caribaea var hondurensis in an agroforestry land use system on the Atherton Tableland, north east Australia, is described. The establishment of the tree component involves mechanical cultivation and the application of herbicides which in combination are technically feasible and acceptable to a landholder who wishes to integrate pine trees and pasture grasses. The cost of establishment and maintenance of the pines up to age 39 months was calculated at $A809 ha?1 (1986 values). This includes the cost of thinning. The sale of some thinnings for Christmas trees realised a net profit of $A564 from 300 trees ($A188 ha?1). At age 38 months the stand had a stocking of 254 trees ha?1, a mean height of 6 m and a mean diameter at breast height of 12.1 cm. The growth compares favourably with other plantation grownPinus caribaea var hondurensis on the Atherton Tableland.  相似文献   

10.
The parasitoid fauna of Coccoidea in cultivated and noncultivated areas was studied in the east Mediterranean region of Turkey in 1994–1997. In total, 25 parasitoid species belonging to Aphelinidae, Encyrtidae, and Eulophidae (Hymenoptera) were reared from 21 different scale hosts. On crop plants, mainly citrus and peach, 13 parasitoids from eleven Coccoidea hosts were determined while 14 parasitoid species were obtained from twelve scale insects on non-cultivated plants. Seven parasitoid species are new records for the Turkish insect fauna. Only one of them was found on citrus, while the other six species were sampled in non-cultivated areas. The most common parasitoids encountered wereAphytis melinus DeBach,Encarsia berlesei (Howard) (Aphelinidae),comperiella bifasciata Howard (Encyrtidae), andMetaphycus flavus (Howard) (Eulophidae) in cultivated areas andCoccophagus lycimnia (Walker) (Aphelinidae) in non-cultivated areas. All other parasitoids species were obtained only from a few scale insects hosts.  相似文献   

11.
During spring and summer 1990 observations on the biology of the ash sawfly,Tomostethus nigritus F. were made and control options discussed. The sawfly overwinters as an co- or pronymph in the soil, and pupates in earlys spring. The tlight period lasted for about 3 weeks. The larvae fed on the leaves till June. Injecting the systemic insecticide Carbicron 50 SCW (Dicrotophos) was successful.  相似文献   

12.
Response of growth and secondary metabolites to light intensity are useful measurements to determine suitable silviculture treatments for the cultivation of medicinal plants. Here, we analyzed the growth, flavonols (total flavonol, quercetin, kaempferol, and isorhamnetin) content, flavonols yield per plant, and expression of flavonoid biosynthesis-related genes in 2-year Ginkgo (Ginkgo biloba L.) seedlings at four different light intensities (100, 76, 40, and 25 % of full sunlight) in a greenhouse setting. Across all light intensities, the 76 % sunlight treatment produced the highest growth of total biomass, root, stem, and leaf, indicating negative effects of either fulllight or heavy shading on Ginkgo seedling development. Both flavonols (total flavonol, quercetin, kaempferol, and isorhamnetin) content and expression of flavonoid biosynthesis-related genes [PAL (Phenylalanine ammonia-lyase), CHS (Chalcone synthase), F3H (Flavanone 3-hydroxylase), and FLS (Flavonol synthase)] in leaves were highest under 100 % sunlight, suggesting that full sunlight promotes the expression of flavonoid biosynthesis-related genes and increases flavonoid biosynthesis. The highest and lowest flavonol contents were found in leaves and stems, respectively. The 76 % sunlight treatment produced the highest flavonols yield while the 100 % sunlight produced the highest flavonoids content in leaves, indicating that flavonol production per unit land area depends not only flavonol content but also biomass. Overall, in order to achieve the highest flavonols yield per area in Ginkgo leaf-harvesting plantations, it is important to manipulate light conditions of field.  相似文献   

13.
The silverleaf whitefly, Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae), is considered one of the most important pests of cowpea (Vigna unguiculata L. Walp.), limiting the productivity of this crop worldwide. Chemical control is still the main strategy for the management of populations of this insect. However, due to the harmful effects of pesticides on the environment and to humans, less injurious alternatives have been investigated. Along this line, the use of resistant genotypes can be a valuable tool for the control of the silverleaf whitefly. In this paper, we investigate some biological aspects of B. tabaci biotype B confined on 14 genotypes of cowpea. We evaluated the incubation period, egg viability, duration of nymphal stages, total duration of the juvenile phase, instar mortality and total mortality of the immature stage. The genotype MNC 99-541 F21 exhibited antibiosis against the whitefly, prolonging the lifecycle of the insect. The genotypes Canapu, BRS-Urubuquara and TE97-304 G-4 also exhibited antibiosis, causing high nymphal mortality. These results may help in breeding programmes to develop cowpea lines with resistance to B. tabaci biotype B.  相似文献   

14.
The vertical and horizontal distribution, as well as the persistence ofSteinernema glaseri, S. carpocapsae (1192, I 100 and Mexican strains),Heterorhabditis bacteriophora, H. heliothidis andHeterorhabditis sp. were studied in three different soil types under field conditions. The presence of infective juveniles in soil samples taken at various depths was assessed usingGalleria mellonella larvae as baits for the nematodes. Results show that all tested nematodes had a similar pattern of vertical distribution. On the other hand,Heterorhabditis spp. were significantly more persistent thanSteinernema spp. in all soil types. As for the horizontal dispersal, none of the nematodes were ever found outside the treated plots, indicating that most of the juveniles remained near the point of application.  相似文献   

15.
A review of research on the nun moth (Lymantria monacha L.) 1973–1984 in Czechoslovakia conducted with pheromone traps is given. By using this method many new results on bionomy, ecology and gradology of this pest could be obtained.  相似文献   

16.
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   

17.

Context

Anthropogenic activity has increased the level of atmospheric CO2, which is driving an increase of global temperatures and associated changes in precipitation patterns. At Northern latitudes, one of the likely consequences of global warming is increased precipitation and air humidity.

Aims

In this work, the effects of both elevated atmospheric CO2 and increased air humidity on trees commonly growing in northern European forests were assessed.

Methods

The work was carried out under field conditions by using Free Air Carbon dioxide Enrichment (FACE) and Free Air Humidity Manipulation (FAHM) systems. Leaf litter fall was measured over 4 years (FACE) or 5 years (FAHM) to determine the effects of FACE and FAHM on leaf phenology.

Results

Increasing air humidity delayed leaf litter fall in Betula pendula, but not in Populus tremula?×?tremuloides. Similarly, under elevated atmospheric CO2, leaf litter fall was delayed in B. pendula, but not in Alnus glutinosa. Increased CO2 appeared to interact with periods of low precipitation in summer and high ozone levels during these periods to effect leaf fall.

Conclusions

This work shows that increased CO2 and humidity delay leaf fall, but this effect is species-specific.  相似文献   

18.
Influences of fiber orientation and milling on wood cellulose crystallinity were studied using jack pine wood. The fiber orientation effects were measured by sampling rectangular wood blocks in radial, tangential, and cross-sectional orientations. The influence of milling was studied by analyzing the unsieved and sieved milled wood fractions (all <1,000 μm). Fiber orientation effect was manifested in both X-ray and Raman measurements and was dependent upon the orientation of the sampled wood blocks. In Raman, the observed crystallinity was similar between the blocks sampled on the tangential and the radial faces. However, the estimated values were 5.5 % lower compared to that measured in a powdered sample pellet. Moreover, in these sampling modes, the orientation of the block with respect to the direction of the electric vector of the laser made a difference only for the tangential mode of sampling. When a wood block was sampled on the cross-sectional face, the observed Raman crystallinity was 3.9 % higher from that of the pellet. The observed crystallinity did not significantly differ with change in sample orientation with respect to the electric vector direction. In contrast, the Segal-WAXS study of the blocks indicated that compared to the pellet, the estimated crystallinities in the radial, tangential, and cross-sectional sampling modes were 5, 2, and 11 % lower, respectively. This suggested that the radial and the tangential faces of the blocks can be used to estimate the crystallinity of wood. With regard to the effect of milling on Raman and Segal-WAXS estimates, the wood crystallinity did not depend upon the particle sizes of the fractionated samples and was similar to that of the original unfractionated ground wood.  相似文献   

19.
Maritime pine (Pinus pinaster Ait.) is an important timber and pulpwood species covering about 4 million ha in Portugal, Spain and France. This work studied the cross-sectional distribution of heartwood and sapwood along the stem using 3D modelling on 20 trees. The target was to assess the potential of this species for the industrial production of heartwood sawn products. The maritime pine stems were characterized by wide sapwood of 10 cm, in average, and the presence of heartwood at all height levels with constant diameter up to 35 % tree height, decreasing afterwards. In the radial section, the heartwood follows a circumferential-like shape which changes along the stem. Pith eccentricity index values were low and homogeneous regarding to stem and higher for heartwood. Heartwood cross-sectional shape was constant up to 45 % of total height of the tree and more elongated upwards. The constant heartwood diameter, low taper and pith eccentricity index, and an approximate circular shape up to 10 m height indicated these species’ potential to produce solid wood products made out of heartwood.  相似文献   

20.
Food crops have come under increasing threat from soil insect pests as a result of monotonous use of arable land and the unavailability or ban of soil insecticides. The development of new management strategies is hindered by the limited knowledge of the identity and biology of local soil pests. A literature survey was carried out focusing on the cold temperate zones of East Asia (north-eastern China, far south-eastern Russia, both Koreas). As for DPR Korea, field surveys were added. At least 53 soil insect species appeared to have wide-ranging importance. The highest diversity of soil pests attack maize (at least 29 species), cereals (27), soybean (19), potato (19), other beans (16), peanut (16), fruit tree nurseries (14), followed by cabbage, sorghum, cotton, grassland habitats, and sweet potato. Most belong to the Melolonthidae (21 %), Scarabeidae (15 %), Noctuidae (13 %) or Elateridae (11 %). Genera containing the most species were the melolonthid Holotrichia (at least five species), scarabeid Anomala (5), agromyzid Delia (4) and noctuid Agrotis, melolonthid Maladera, and gryllotalpid Gryllotalpa (each three). Below-ground damaging pests appeared widely problematic across the cold temperate zones, probably due to the limited variety of crops suitable for rotation or strip cropping, and efficient adaptation of pests to the soil environment as a result of long overwintering periods. This review will, as a result of making some of a vast repository of non-English language information available, help to better understand the soil pest community in these regions, and support the development of more effective control methods.  相似文献   

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