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1.
Urban trees provide vital ecosystem services such as mitigating heat island,improving air quality by removing various air pollutants,capturing rainwater,and acting as topsoil carbon storage.The aesthetic value of urban trees is also another feature that has to be considered in the context of urban greening.Classical criteria for the selection of urban trees have to respond to new challenges imposed to the cities in a near future.Global climate change factors increase the harshness of our cities,and thereby the plant resilience to abiotic stresses has also to be seriously considered for planning the urban greening.Red-leafed species,characterized by the permanent presence of foliar anthocyanins,show a greater tolerance to different environmental cues than green-leafed species commonly used in our cities.In addition,red tree species own a great aesthetic value which has been underestimated in the context of urban areas,especially in the harsh Mediterranean cities.In this study,we emphasize the "privilege of being red" from different point of view,in order to drive the attention to the possibility to increase the use of red-leafed species for urban "greening".Some possible negative aspects related to their use are rebutted and the direction of future researches are proposed.  相似文献   

2.
Interactions of fire cycle and plant species' reproductive characteristics could determine vegetation distribution pattern of a landscape. In Canada's boreal region, fire cycles before the Little Ice Age (c. 1850s) ranged from 30-130 years and 25-234 years afterwards until the settlement period (c. 1930s) when longer fire cycles occurred in response to climatic change and human interference. Analysis indi-cated that fire cycles were correlated with growing season (April-October) temperature and precipitation departure from the 1961-1990 nor-mal, varying by regions. Assuming that wildfires will respond to future warming similar to the manner during the past century, an assess-ment using climatic change scenarios CGCM1, CGCM2 and HadCM2 indicates fire cycles would divert to a range of 80-140 years in the west taiga shield, more than 700 years for the east boreal shield and east taiga shield, and 300-400 years for the boreal plains in 2050.  相似文献   

3.
Interactions of fire cycle and plant species' reproductive characteristics could determine vegetation distribution pattern of a landscape. In Canada's boreal region, fire cycles before the Little Ice Age (c. 1850s) ranged from 30-130 years and 25-234 years afterwards until the settlement period (c. 1930s) when longer fire cycles occurred in response to climatic change and human interference. Analysis indicated that fire cycles were correlated with growing season (April-October) temperature and precipitation departure from the 1961-1990 normal, varying by regions. Assuming that wildfires will respond to future warming similar to the manner during the past century, an assessment using climatic change scenarios CGCMI, CGCM2 and HadCM2 indicates fire cycles would divert to a range of 80-140 years in the west taiga shield, more than 700 years for the east boreal shield and east taiga shield, and 300-400 years for the boreal plains in 2050.  相似文献   

4.
I analyzed and elaborated the trends in and responses to global change in arid regions of China, from the perspective of nine variables, i.e., temperature, precipitation, river runoff, melting glaciers, water level of lakes, wind power and evaporation, vegetation, oases, and desertification. The climate and hydrology data I cited represent many years of observations. I conclude that, since the 1980s, the climate in arid regions of China has clearly changed with rising temperatures and precipitation in most areas. Wind power and the number of galestorm days have continuously decreased, which resulted in an improvement of humid conditions and increases in river discharge and water levels of lakes. Simultaneously, vegetation also has improved and the process of desertification has essentially been arrested. Although there are some unfavorable developments, such as decreased river flows or flow interruptions and downstream oases have suffered from degradation, these incidental cases should not distract our attention from the generally favorable trends during the middle and late 20th century. These discordant phenomena are not consequences of climate change but rather of unsuitable human activities. Despite a substantial increase in precipitation, the level of the original precipitation was so small that any increase in precipitation was still small. As a result, none of the fundamental conditions such as a scarcity of water resources and precipitation nor the landscape of drought-ridden deserts in the arid regions will change. The vulnerability of the eco-environmental system in the arid regions will not change fundamentally either in the near future. __________ Translated from Scientia Silvae Sinicae, 2008, 44(8): 124–130 [译自: 林业科学]  相似文献   

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  • ? It is agreed that climate (precipitation and temperature) influences the distribution of plant species. Near the margins of a species’ natural range, climate becomes limiting to physiological processes. There, climate change may be expected to have a significant impact on tree growth and the species’ ranges may be altered.
  • ? In order to assess what influence climate change could exert on the distribution of pine species at their margin, radial growth trends in ring-width chronologies over the last century were analysed. In the French Mediterranean area where climate change is characterized by increased temperature, forest plots were selected along an altitudinal transect on the north-facing slope of the Sainte-Baume mountain (Bouches-du-Rhône, France) where the ranges of Pinus sylvestris and Pinus halepensis overlap.
  • ? Two growth patterns were identified. For P. halepensis, radial growth has increased at all altitudes indicating that climate change has improved growth conditions of this species near the margin of its ecological range. For P. sylvestris, radial growth has increased only at low altitudes and even decreased at high altitudes.
  • ? It must be deduced that the growth changes observed cannot be generalised either at the species level or at the geographical level and must be interpreted with great caution.
  •   相似文献   

    7.
    Whatare"river-connectedlakes" River-connectedlakesmeanthelakesthatareconnectedwithriversandintoorfromwhichthereisriverwaterorlakewaterfreelyflowing.Mostofthemedium-sizedorlargerlakes(morethan10km2)atthetwosidesoftheChangjiangRiverwereoriginallyriv…  相似文献   

    8.
    The economy of the Ukraine is in transition from a communist command-and-control to a capitalist system. In this paper, we describe the current state of its forest resources, the structure of its forestry and wood processing sectors, and the problems facing policy makers. While the forest sector should be, and still has the potential to become, an engine for economic growth, the combination of past exploitation and the slow pace of economic reform are major obstacles to implementing rational forest policies. Given the right economic incentives and appropriate forest policies, it may still be possible for the Ukraine to improve its future timber supply while enjoying environmental benefits from its forests. However, this requires economic and institutional reforms beyond the forest sector.  相似文献   

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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   

    11.
    The whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a worldwide pest which has become one of the main pests in tomato crops. The predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae) and the parasitoid Eretmocerus mundus (Mercet) (Hymenoptera: Aphelinidae) have shown their efficacy at controlling B. tabaci populations when used as biological control agents. Intraguild predation (IGP) between natural enemies can affect their effectiveness at controlling pests. In the present study, the interaction of these three natural enemies and their effect on B. tabaci was studied on tomato plants by combining morphological observations and molecular analysis of trophic interactions. Under the conditions used in the present study, no IGP was detected between M. pygmaeus and N. tenuis by either counting dead predators or by PCR using prey-specific cytochrome c oxidase I primers. However, predation on B. tabaci decreased when they coexisted on the same plant, which could compromise the biological control of this pest. Although PCR analyses using E. mundus-specific primers showed predation on B. tabaci-parasitized nymphs in 27 % of M. pygmaeus and 17 % of N. tenuis, B. tabaci control was improved when both predators coexisted on the same plant with the parasitoid. The combined use of E. mundus and M. pygmaeus/N. tenuis is therefore recommended in order to improve B. tabaci control in conservation biological control strategies.  相似文献   

    12.
    Alongthe6300-kmfulllengthoftheChangjiangRiver,agroupoflakesthatstretchesgreenandvastconstitutesauniquelifesystemofitsvalley.Here,thereusedtobesomuchvitality:howlingmonkeys,flyingbirdsandcountlessaquaticorgasmsinbluewaterandwhitesand,givingrisetothemostpro…  相似文献   

    13.
    概述了近20年来国内外对催化α-蒎烯氧化反应过程的研究,重点分析了α-蒎烯氧化中催化剂的性能特点及产物分布规律,总结了过渡金属盐、氧化物、配合物、分子筛及杂多酸在α-蒎烯氧化中的催化作用,比较了催化活性及选择性的特点,并初步探讨了发展趋势.提出在已有的α-蒎烯氧化反应催化剂中,分子筛类催化剂在制备方法和工业化发展上有一定的优势,深入研究过渡金属化合物在α-蒎烯氧化反应的催化性能及调变方法,应是α-蒎烯氧化反应中值得重点关注的研究内容.  相似文献   

    14.
    The black-necked crane that is rarely known to peopleThere lived32species of cranes in the history of the earth,but now there are only15species.Of the15species,the black-necked crane is the last species found by mankind.It was found in Qinghai Lake of Chi…  相似文献   

    15.
    We investigated the correlation of large fires([300 ha) from 1992 to 2013 within the borders of the Antalya Regional Directorate of Forestry using the Keetch–Byram drought index(KBDI). Daily KBDI values were calculated for each year, and values for the period before the year 2000 differed significantly from those after2000. After 2000(large fires occurred in 2004, 2006, 2007,2008, 2010, and 2013), when KBDI values increased, the KBDI, but not the number of fires, was inversely correlated with the natural log of the burned area(NLBA). While there were both high and low KBDI values when the NLBA was small, only high KBDI values were associated with high NLBA values. Particularly for logarithmic values of 4 and higher, KBDI values increased in parallel with increases in NLBA values. On the basis of a Mann–Whitney U test done in addition to a Pearson correlation test, we found that when the burned areas were grouped according to small and large areas, the KBDI could be used to distinguish the two groups. Using a conditional probability analysis, we found that 4th, 5th and 6th class KBDI values may lead to large fires at the 60 % possibility.Similarly, the possibility of large fires greater than the median burned area in any given 6 years was found to be48 %. In addition, while the mean value of KBDI is 390.51 for the period from May to September for these 6 years, it is 359.93 for the other years. Consequently, the area burned also increased as the KBDI classes(Class 0: 0–99, Class 1:100–199, Class 2: 200–299, Class 3: 300–399, Class 4:400–499, Class 5: 500–599, Class 6: 600–699, and Class 7:700–800) increase.  相似文献   

    16.
    The Kayapó Indians of Brazil's Amazon Basin are described as effective managers of tropical forest, utilizing an extensive inventory of useful native plants that are concentrated by human activity in special forest areas (resource islands, forest fields, forest openings, tuber gardens, agricultural plots, old fields, and trailsides). Long-term transplanting and selection of plants suggest semi-domestication of many species. The overall management strategies of forest also includes many manipulated animal species (birds, fish, bees, mammals) utilized as food and game. Forest patches (apêtê) are created by Indians from campo/cerrado using planting zones made from termite and ant nests mixed with mulch: formation and development of these is briefly discussed, including the implications for new ideas concerning reforestation and campo management. Finally an integrative cognitive model is presented showing the relationships between variants of forest and savanna recognized by the Kayapó. Indigenous knowledge of subtle similarities between conceptually distinct ecological units in the model allows for the interchange of botanical material between microclimates to increase biological diversity in managed areas. It is suggested that indigenous knowledge is extremely important in developing new strategies for forest and campo/cerrado conservation, while improving productiveness of these ecological systems. Such knowledge is not only applicable for Amazônian Indians, but also has far-reaching implications for human populations throughout the humid tropics.This is a preliminary survey of indigenous management strategies that is generated as a part of the Projeto Kayapó , an interdisciplinary ethnobiological research project funded by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brazilian National Council for Scientific and Technological Development) and the World Wildlife Fund. I would like to thank Drs. Gerhard Gottsberger and Anthony Anderson for their assistance in collecting plants that are currently being identified to supply more complete data on Kayapó subsistence. I also wish to thank FUNAI (Fundaão Nacional do Índio) for their assistance and support, as well as FAB (Fora Aérea Brasileira) and VOTEC for providing some transportation to/from Gorotire, and the Unevangelized Field Missions for their assistance in providing communication and acquiring supplies.  相似文献   

    17.
    IntroductionAsagrowthmodelforanindividualtreeorforeststhnd,theChapman-RichardsFunction,anextensiontotheVonBertalanffy'sgrowththeory(Bertalanffy1957)embodiesallotherestablishedgrowthfunction.ThisfunctionhasbeenwideIyusedinforestrybecauseofitsflexibility,ac…  相似文献   

    18.
    Withitsuniquelyfavorableecologicalenvironment,theChangjiangRiverbreedstheChineseriverdolphinsandcow-fishes.Thedistributionoftwocetaceananimalsinthesameriverisrarelyseenintheotherriversoftheearth,highlightingthedistinctivecuttingedgesoftheChangjiangRiverin…  相似文献   

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