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1.
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   

2.
From generation to generation, people cultivate orchid, sing for orchid, draw orchid and keep notes about orchid. So many records of precious species and calligraphic works are left over through ages. At all times and in all over the world, orchid has bee…  相似文献   

3.
IntroductionGreatBustaFd(OtiStBfdB),Gruiformes,Qtidae.ItismainlydistributedinEurope,southofSiberia,andInnerMongoliaAutonomousregioll,JinnProvinceandHeilongjiangProvinceinChina.ItisnearextinCtinCtionbecauseofoverhunting,therefore,itwaslabeledinAppendixlofCITESin1987.InChina,itwasraisedartificiallysincetheearlyof1950s,butfirSttriedinzoosin1987.UPtonow,therearestillmanytechnicalproblemsonartificialbreedingbeingunsolved.SoresearchongreatbuStardwillprovidescientificbasisforartificialbr…  相似文献   

4.
DearcolleagueScientificperiodicalisamainkindofmediumforpublishingscientificresearchresutts.Aboutseventypercentofresearchresultsarepublishedindifferentformsofperiodicals.Thereareabout260kindsofforestryjournalsinChina.Thesejournalsareplayinganimportantroleinadvancingacademicexchangesandflourishingforestryresearch.Mostofthesejoumals,however,arepublishedinChinese,somewithEnglishabstracts,veryfewpublishedinEnglish.SothescopeofacademicexchangesofforestryresearchislimitedinChina.NortheastForestry…  相似文献   

5.
INTRODUCTION After his study in the change of liver cell in human body, Kerr (1972) discovered Programmed Cell Death (PCD), a cell death model totally different from cell necrotic death, in which the cell necrosis usually appears typically as break of the protoplasm membrane and inflammatory leak of cell inclusions, which is a kind of abnormal process. PCD is a kind of active, physiologic death process. This kind of cell death process can helpthe body to eliminate decrepit, excrescent …  相似文献   

6.
Past studies already showed that the protectiveeffects of shelterbelts varied with the structuralparameter of shelterbelts. To get full use of theprotective effects, we must keep the shelterbelts withoptimal structure. In the former studies, theshelterbelts structure was generally divided into 3 or4 types (Cao Xinsun, 1983). Then two new structuralparameters, porosity (β) and permeability (α) as wellas their optimal values were put forward by the latterresearchers (Caborn, 1957; Cao Xinsun…  相似文献   

7.
The effects of water potential, NaCl and Na2SO4 on germination and radicle growth of two riparian tree species, Populus euphratica Oliv. and P. pruinosa Schrenk (Salicaceae), were tested. Growth chamber studies revealed an optimum temperature range for seed germination of both species between 15-35℃. The final germination percentage of both species decreases with decreasing water potential in all types of solution applied in the experiments. P. pruinosa was less tolerant to low ψw stress than P. euphratica, especially in salt solutions. Germination percentages fell below 20% for P. pruinosa at -0.6 MPa (NaCl) or -0.4 MPa (Na2SO4) and for P. euphratica at -1.2 MPa (NaCl) or-0.6 MPa (Na2SO4). Radicle growth of both species was inhibited by high concentrations of PEQ NaCl and Na2SO4. However, growth was enhanced at -0.13 and -0.29 MPa in PEG or at -0.13 MPa in NaCl solutions compared to distilled water. Radicle growth of P. euphratica was higher than that of P. pruinosa. Germination and radicle growth of both species exhibited ion toxicity. Na2SO4 was more toxic than iso-osmotic solutions of NaCl. Radicle growth proved to be more sensitive than seed germination. Thus, flooding does not only yield the necessary soil moisture for germination but also favors seedling establishment of both species through leaching of salts from the soil surface. The different sensitivity of the species during their early growth stages might, moreover, contribute to the observed differences in their distribution in the Talim Basin (northwest China).  相似文献   

8.
lntroductionChinesefir(Cunntwh8mi8IanceoIat8(Lamb.)Hook)isaveryimportantspeciesofwoodresourcesinSouthernChina.TheheredityandameliorationonChinesefirareaIwayspaidgreatattention.However,inthepast,thefocaIpointOftheworkonheredityandamelioF8tionwashowtoCuItivatetheChinesefirwithcharaCtersoff8stgrowth,goodfigure,wideadaPt-abilityandStrongdiseaseresistance.LittleworkwasdoneonameIior8tionofwoodquaIity.AlongwiththecompositionchangeoftheforeStresourcesinChina,Chinesewoodindustryismoredependen…  相似文献   

9.
The biology treatment of cellulases or hemicellulases is used in this paper. The effects of cell ulases and hemicellulases on surface wettability and gluing property of poplar and wheat straw were investigated. It was found that the surface contact angles of poplar and wheat straw were reduced and the surface free energies were increased after treatment by these enzymes. The gluing strengths of popular and wheat straw were enhanced with the increases of the dosage of enzymes and the time of enzymatic treatment.  相似文献   

10.
IntroductionChemicaldefenseisoneofanumberofwaysthatpIantsaredefendedfrommammalianherbivore.SuchchemicaldofenseinvolvestheelaborationandaccumuIationoforganicsubstanceswhenthepIanttissueiseaten.Thesubstancesmaybebittertasting,poisonous,oftenodour,orhaveantinutritionaIeffects.Thegreatmajorityofdeferentsubstancesaretheproductsofsecondarymetabolism.TheyrepresenttheammuIacationofendproductsfromarelativeIyIengthpathwayofenzyme-cataIyzedstepsinbio-synthesis.TheproductsarethenchannelIedwithinthepl…  相似文献   

11.
熊文愈  黄樨 《林业研究》1997,8(2):77-82
IntroductionAsabranchofsystcn1scicnccs'ccos}'stc111scl1ginccr-ing,isdevelopcdfromtl1cpracticcofccoIogicalcl1gi-neeringforstudyandn1a11agcn1cl1tofecos}'Stcl11s.Itstheqandn1cthodolog}'arcl11ai11l}dcri\'cdfro111s}'s-temscnginceringands}'Stc11lsccoIog}'.II1tl…  相似文献   

12.
Urban forest includes the forest that grows in the citycore and the city fringe. And its scale should be largeenough to affect temperature, precipitation and wildanimal activities so that city residents will gain a feelingof returning to the nature. American experts arguesthat only when standing ground basic area reaches5.5 ~ 28.0 m2/ha, the forest can be classified as anurban forest (Liang Xingquan, 2001). With thedevelopment of urban construction and urban forestry,all trees, including bush…  相似文献   

13.
In order to understand the occurrence and the developmental regularity of seabuckthorn carpenterworm (Holcocerus hippophaecolus) and predict its population density, the developmental threshold temperature (C) and effective accumulative tem- perature (K) of the carpenterworm pupae and eggs were analyzed under the conditions of constant and variable temperatures. The results show that the values of C and K of the carpenterworm pupae are (12.1 ± 0.2) °C and (295.2 ± 4.1) day-degrees at constant temperatures, and (15.5 ± 0.4) °C and (202.4 ± 13.1) day-degrees at variable temperatures. However, the values of C and K of the eggs at variable temperatures are (16.7 ± 0.8) °C and (101.5 ± 12.6) day-degrees. The differences of developmental threshold and effective accumulative temperature under the conditions of constant and variable temperatures of the carpenterworm pupae accord with the developmental regularity of most insects in nature. By comparing five different constant temperatures, the conclusion is that the optimum developmental temperature of the pupae is 21 °C when both the pupation of the mature larvae and the eclosion of the pupae are very accordant. Moreover, the percentage of eclosion is over 90%. The average developmental durations of the carpenter- worm pupae and eggs are 31 and 16 d at variable temperatures.  相似文献   

14.
INTRODUCTION The larger genus in Polygonaceae is Calligonum, which includes about 100 species of shrubs that grow in central Asia. It is well suited to arid climates with drought resistance, and grows more on clay, sandy and gravel grounds. These plants are often cultivated as ornamentals and a stabilizer of mobile sand dunes. There was published information on the wood anatomy of all the examined genera in Polygonaceae (Ma 1994), but the selected species have not yet been described. Ad…  相似文献   

15.
IntroductionLarisoIgensiSHenryandLarisgmeIinii(Rupr.)Rupr.areboththenativetreespeciesinChina,buttheirdiStributingcentersarenotwithintherangeofChina.LarisoIgen$isismainlydistributedinNoFthKoreaandadjacentNortheastChinaandRussia(Dylis1961).lnChina,itsdistributingcenterisintheChangbaiMountains.Nevertheless,LarisgmeliniiismainlydistributedintheFar-EastandEastSiberiaofRussiaandNortheasternChina.ItsdistributingcenterinChinaisintheDaxing'anMountains.Thecharac-tersofthesexuaIreproduction…  相似文献   

16.
A survey on the symptom and severity of the leaf spot disease of Pongamia pinnata L. was conducted in the nurseries of the Institute of Forestry and Environmental Sciences, University of Chittagong (IFESCU), Bangladesh Forest Research Institute (BFRI) and Aronnak Nursery in Chittagong. The highest infection percentage and disease index were found in IFESCU nursery, followed by BFRI and the lowest was recorded in Aronnak nursery. The associated organism of leaf spot disease of P. pinnata was isolated from the diseased plant parts and the pathogenicity was established with the isolated fungus. Colletorichum gloeosprioides Penz was proved to be pathogenic. The inhibition of mycelial growth of C. gloeosporioides was observed and identified as suitable fungicides (Bavistin, Cupravite and Dithane M-45) and doses (0.05, 0.10, 0.50, 1.00, 1.50 and 2.00). The lowest and highest mycelial growth were respectively found on Bavistin and on Cupravite at the concentration of 0.05 after 8th day of incubation. It indicates that out of the three tested fungicides, Bavistin showed most effective, followed by Diathane M-45, and Cupravite was ineffective for its very little inhibition on mycelial growth.  相似文献   

17.
For the high biomass and adaptability, application of willow on cultivating bioenergy forest and phytoremediation had been gotten more recognition in the world wide. Integrated with our research practice, we introduced the germ plasm of high biomass willow in China, and the new varieties with high biomass and their cultivated techniques were summarized in this article. Moreover, we reported the development up to date in breeding and cultivation on well-bred willow with high biomass and analyzed the foreground of establishing industrial willow with high biomass in China.  相似文献   

18.
TheprojectofSichuanCommunityForestry,fundedbytheFordFoundationandassistedandguidedbyRECOFTC,isaseriesofactivitiesofresearch,practiceandpromotionofthebestmanagementandoperationalmodesimplementedintheareaoftheprojectofYangtzeriverprotectiveforest.Since1992,SichuancommunityforestryhascarriedoutsomepilotworksinQuxiancounty,PingchangcountyandButoucounty.1.ThethinkingandfeaturesofcommunityforestryCommunityforestryisacompletelynewthinkingandmethodofworksintroducedfromabroad.Itisaproductofcombi…  相似文献   

19.
C.anachoreta causes disease of poplars and willowsthroughout China and reproduces four generationsduring one year in Beijing, lasting the whole growthperiod of forest, not only influencing the landscapebut also bringing economic loss. To produce CaGVand other natural enemies need a large number ofequally developed host insects. For this reason,rearing C.anachoreta is an important subject.CaGV is an obligate parasite with high toxicity andpathogenicity to C.anachoreta. Because of its virion…  相似文献   

20.
The microstructural and ultrastructural traits of three kinds of typical leaves of Populus euphratica Olive, including lanceolate, broad-ovate and dentate broad-ovate leaves, were studied by using electron microscope and optical microscope. The re- sults showed that with the leaves changing from lanceolate shape to dentate broad-ovate shape, their structure obviously tended to be xeromorph: developed palisade tissue, undeveloped spongy tissue, thick cutin layer and sunken stomas. The amount of mitochondria tended to be increased, and the shape of chloroplasts varied from regular spindle to irregular rotundity or oval. The leaves were cov- ered with wax without cilium, and the stomas on the upper and lower epidermis of the leaves opened unevenly. The stomas on the lower epidermis were deeper than those on the upper epidermis under the scanning electron microscope. The results implied that the structural characteristics of the diversiform-leaves of P. euphratica are related to its eco-adaptability.  相似文献   

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