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1.
太行山在造山运动过程中由于构造时间和强度的差异,在地貌上形成了高低、大小不一的山体。依据地貌形成规律和植被类型,将太行山中南部分为低山、中低山、中山、中高山4个立地类型亚区。在海拔的控制下,再根据坡向、地形部位划分出17种立地类型;结合乡土树种分布调查,为17种立地类型提出了可选用的乔灌木树种;根据立地类型和指示植物生物学与生态学特性进行宜林性质划分,提出了水土保持林、水源涵养林、经济林、用材林的适宜树种。 相似文献
2.
A model is described for predicting the dynamic changes in theproportion of tree, shrub and grass life forms at the globalscale. This model is driven by the impacts of climate, soilsand CO2 on global vegetation leaf area index and net primaryproductivity. The life-form model has been used to explore theinfluences of global warming and continued CO2 increase on treecover This reflects a realization from other modelling workthat forested vegetation, at the global scale, exerts significantinfluences on climate, and so it is important to assess thepotential for this feedback under climatic change. An increase in CO2 from 350 to 560 p.p.m. is modelled to haveonly a small impact on tree cover, under current climate. Aregionally-consistent and global increase in temperature ofc.2{ring}C and a 10 per cent increase in precipitation, butwith no increase in CO2, indicates a significant potential fortrees to spread into current shrub tundra, over a period of50 years This could lead to regional warming, through changesin winter albedo. The effect of the CO2 increase is most noticeablein interaction with increases in temperature (2{ring}C) andprecipitation (10 per cent). In this case the life-form modelprojects further increases in tree cover, particularly in areaswith seasonally low periods of precipitation. 相似文献
3.
Based on the plot data from the investigation and the theory of forest ecology and ecological system, the site classification
of the eastern forest region of Daxing’an Mountains was made by mean of mathematical method. The main factors were slope,
thickness of soil layer, slope position and slope aspect. Grades of slope were used as the division standard for site type
group. The slope aspect, slope position and thickness of soil layer were used as the division standards for site type. Altogether
7 site type groups and 15 main site types were determined the region. It provided reliable fundamental basis for the reasonable
management and planting design in the area.
Responsible editor: Zhu Hong 相似文献
4.
Site studies have shown that conifer plantations in northernBritain have increased in General Yield Class (GYC) by 1 m3ha–1 a–1 per decade or more (20–40 per cent)since the 1930s. Large increases in forest productivity havealso occurred in many other regions of Europe. Are these increasesdue to improved silvicultural practices or to increases in Ndeposition, CO2 and temperature? Two process-based mathematicalmodels of forest growth were used to simulate the responsesof conifer forests growing in the Scottish southern uplandsto increases in atmospheric N deposition, CO2 concentrationand temperature, during this century and next century. The modelsdiffered substantially in the ways in which underlying processeswere represented: one simulated a managed plantation, the othera natural forest. Nevertheless, both showed that: (1) increasesin N deposition, CO2 and temperature together might accountfor up to half of the observed increase in GYC this century;(2) increased N deposition and CO2, considered separately, probablyincreased forest productivity by a modest amount (7–14per cent), but their combined effect has been approximatelyadditive; (3) increased temperature, even when combined withincreasing CO2 concentrations, promoted growth less than expectedfrom site studies relating GYC to temperature; and (4) substantialfurther increases in productivity, GYC, leaf area index andstanding biomass are forecast during the next century as a resultof increasing CO2 concentrations and continued N deposition,with or without climatic warming. The predicted increases inGYC could be large enough to have profound effects on the forestindustry. 相似文献
5.
StudysiteThestudysiteislocatedintheeasternslopeofDaxing'anMountains(47"25'~49'37'N,119'37'-122"45'E),whichbelongstotheBalinForestryBu-reauofNeiMenggol.ThemaintopographyislowermountainsandhilIs.Thealtitudeis4oo~1ooom.Theannualaccumulativetemperature(>=1oC)isabout1845oC.AnnuaIprecipitationis42omm.Annualaveragetemperatureis-15t.Thefrost-freeperiodis97d.lnthisarea,thezonalsoilisbrownconiferousforestsoil,theothertypeofsoilismeadowsoilandbogsoiI.ThemainfundamentaIrockisgrinite.ThebasaItisse… 相似文献
6.
Using the Relationship between Rate of Tatter and Topographic Variables to Predict Site Windiness in Upland Britain 总被引：1，自引：0，他引：1
Tatter flags have been used for more than 30 years to measurewind exposure of forest sites in upland Britain. A re-analysisof tatter flag data from 1111 sites was performed to investigatefactors influencing site windiness. At each location flags hadbeen flown for periods of 2 months, and six consecutive bimonthlyreadings were combined to provide an annual estimate of tatter.Average daily tatter rate was related to geographic position,aspect, elevation, topex, valley shape and valley direction.The aspect, valley shape and valley direction were all derivedfrom the eight topex sector values; they provide a more detailedtreatment of topography than previous studies and include ameasure for funnelling of wind in valleys. The proportion ofvariance explained by the regression was 80 per cent. The regressionhas been used to develop revised windiness scores for the WindthrowHazard Classification and could be used to estimate site windinessfor site-yield and related studies. Digital terrain models cancalculate the required site variables. Further investigationsto improve the estimates are discussed. 相似文献
7.
在四种质效类型的基础上，按照树种组成和坡度、坡向、土层厚度等立地因子把太行山低质低效林划分为108个类型，就一些主要类型提出了经营改造技术。 相似文献
8.
We examined the short-term effects of group-selection harvestingwith seed tree retention on the diversity, abundance and establishmentof tree seedlings in a northern hardwood forest in the UpperPeninsula of Michigan (49 openings, 20 closed canopy referencesites). Three opening sizes were examined – opening radius0.5 x canopy height (267 ± 62 m2, n = 16), 0.75 x canopyheight (642 ± 85 m2, n = 17) and 1.0 x canopy height(1192 ± 155 m2, n = 16) (canopy height = 22 m). A singleyellow birch (Betula alleghaniensis Britt.) seed tree was retainedin the centre of each opening. Tree seedling density was significantlyhigher in the largest group-selection opening than at the closedcanopy reference sites (P < 0.05), the main factor for thiswas the increased proportion of yellow birch, red maple (Acerrubrum L.) and other minor species. Nevertheless, yellow birchwas still a minor component of the developing gap cohort, comprising5.9 per cent of the seedlings and 1.1 per cent of the saplings.Within openings, microsite variables, such as per cent coversof bare soil and coarse woody debris, were the best predictorsof yellow birch occurrence and density. Our results suggestthat microsite limitations and competing vegetation may greatlyreduce the efficacy of openings for ensuring the maintenanceof mid-tolerants. 相似文献
9.
The decomposition rates of certain dominant litter species inan undisturbed oak-conifer forest in the Kumaun Himalaya wereinvestigated by enclosing pre-weighed, newly senesced leavesin litter bags, placing these bags on the forest floor and determiningthe weight loss by recovering the bags at monthly intervals.Among the species examined, Daphne cannabina decomposed fastestand Cupressus torulosa decomposed most slowly. The former took6 months for complete decomposition, while Cupressus torulosadecomposed to about 72 per cent in 18 months. A linear combinationof rainfall and temperature explained 80 per cent of the variabilityin monthly weight loss. The rate of decomposition was also relatedto the initial chemical composition of the litter. Initially,several constituents showed a significant relation with decomposition;these are nitrogen, calcium, water soluble compounds, totalnonstructural carbohydrates, lignin, acid detergent cell wallcomponents and fibre. Of these, lignin and fibre contents showeda negative relation with weight loss while the others were positivelyrelated. As decomposition progressed, only nitrogen, lignin,ADCW and fibre content remained important. With further lapseof time only two constituents, nitrogen and lignin, remainedimportant. Among these the effect of nitrogen declined withtime while that of lignin increased. A linear combination ofnitrogen and lignin explained 59 per cent variability in theannual weight loss. 相似文献
10.
气候变化情景下河北省3个优势树种适宜分布区预测 总被引：2，自引：0，他引：2
【目的】探究河北省3个优势树种分布与气候因子的关系,并进行适宜分布区预测,以期为评估气候变化的影响及制定适宜未来气候变化的森林经营策略提供理论依据。【方法】依据河北省森林资源调查数据,选取华北落叶松、蒙古栎和油松这3个主要树种,采用ClimateAP气候模型生成当前及未来(2040—2069年和2070—2099年)与降水和温度相关的10个气候因子,利用MaxEnt生态位模型和基于3个气候变化情景(温室气体最低排放,RCP2.6;中度稳定排放,RCP4.5;高度排放,RCP8.5)的一致性预测,模拟3个树种当前和未来的潜在适宜分布区,并采取响应曲线分析主要气候因子对3个树种适宜分布区的影响。【结果】3个树种MaxEnt模型的受试者工作特征曲线下面积(AUC值)都大于0.85,具有较好的预测能力;当前3个树种主要适宜分布在燕山和太行山地区;影响3个树种分布的主导气候因子存在差异,华北落叶松主要受小于0℃年积温和湿季降水量的影响,蒙古栎则主要受最热月平均气温、Hargreaves水分亏缺和湿季降水量的影响,而最热月平均气温、湿季降水量、大于5℃年积温和年均气温是影响油松分布的主要气候因子;一致性预测表明,在2040—2069年,河北省华北落叶松分布面积明显扩大,蒙古栎分布面积变化较小,而油松分布面积显著缩小;在2070—2099年,3个树种的适宜分布面积都显著缩小,幅度均超过3%。【结论】随着气候变化,3个树种均有向高海拔地区迁移的趋势,但在经纬度方向上的分布变化不大。在未来3个树种的适宜分布区,采取人工手段(如造林)辅助树种扩散以适应气候变化,有利于提高森林生产力,构建健康稳定的森林生态系统。 相似文献
11.
The influences of cambial age and ring width on density of Sitkaspruce (Picea sitchensis (Bong.) Carr) were analysed in relationto within-tree trends in tracheid diameter and cell wall thickness.Discs were sampled at breast height from a total of 24 trees,from seven stands at three contrasting sites in Wales, and atbreast height, 30 per cent and 60 per cent total tree heightfrom one of the stands. Across the juvenile wood, ring density decreased with ring numberfrom the pith while radial tracheid diameter increased. Theseoverall trends were considered to be inherent to tree growth,presumably associated with cambial ageing, since they occurredin all trees on all sites. In juvenile wood, density also variedwith site growth rate (as indicated by ring width) at similarcambial age, wider rings being associated with more rapidrateof change in tracheid diameter with ring number and with decreasein tracheid wall thickness. Consequently, on a site having treeswith high growth rate density decreased more rapidly acrossthe juvenile wood, down to a lower minimum value, than on siteswith a slower growth rate. In mature wood, the decrease in densitywith increase in ring width was associated with differencesin both tracheid diameter and wall thickness. Density was slightly(though not significantly) higher at breast height than in comparablerings at 30 per cent total height, associated with significantlythicker tracheid walls at breast height. Changes in radial tracheid diameter (with ring number, or withring width) were associated with greater differences in theearlywood than towards the latewood end of each growth ring,while variations in wall thickness with ring width were associatedwith rate of increase in wall thickness towards the latewoodend. This may account for some previously conflicting reportson influence of silvicultural management on density, for densityis likely to vary with influence of environment on the seasonalcycle of cambial activity. The extent of the juvenile wood as delimited by the inner coreof wide growth rings does not necessarily correspond to theregion of varying tracheid dimensions in Sitka spruce. 相似文献
12.
Russia's forests play a significant role at the global levelin producing both timber and environmental benefits, i.e. inroundwood production, carbon sequestration and biodiversityprotection. Information on these forest resources is based onocular compartment-level forest inventory data. The basic problemwith this inventory approach is that its reliability cannotbe assessed, since the method is not based on statistical sampling.The inventory data for the Novgorod region were therefore checkedby remeasuring a sample of the original compartments in orderto determine their accuracy. The results showed that the originaltotal stand volumes based on the Russian forest inventory wereon average underestimated by 13.4 per cent, the correspondingroot mean-square error for the whole material being 32.4 percent. This bias varied in the range 8–20 per cent betweenindividual different forest management units, leskhozy, andalso varied according to the dominant tree species, being 12per cent in pine-dominated compartments, 14 per cent in birch-dominatedcompartments, 21 per cent in aspen-dominated compartments andhaving a slight negative bias of 4 per cent in spruce-dominatedcompartments. Finally, consideration of timber quality in thevolume calculations showed notable changes from sawnwood timberto pulpwood. 相似文献
13.
Greenhouse gas emissions from the use of primary energy in forest operations and long-distance transportation of timber in Finland 总被引：2，自引：0，他引：2
In Finland in 1993 the greenhouse gas emissions caused by machineryused in silvicultural and forest improvement work, wood harvesting,and timber transportation were 424.2 Gg carbon dioxide (CO2(Gg = gigagram = 109 g), 10.6 Mg nitrous oxide (Mg = megagram= 106 g), 3.5 Gg carbon monoxide, 31.5 Mg methane, 5.6 Gg nitrogenoxide, and 0.7 Gg non-methane volatile organic compounds. Whenemissions were converted into equal units as global warmingpotential in terms of CO2, the warming effects on a 20-yeartime frame equalled 1310 Gg as CO2 and on a 100-year time frame669 Gg as CO2. The proportion of silvicultural and forest improvementwork of the total emission was 8 per cent, cutting of timber13 per cent, haulage 18 per cent, long-distance transportation57 per cent, and transportation of machinery 4 per cent. Theemissions caused by the use of primary energy in forestry seemto be small compared with the amount of carbon in harvestedtimber, which was 30 300 Gg in terms of CO2. 相似文献
14.
A holm oak forest was exposed to an experimental drought (reductionof 15 per cent soil moisture as predicted for this area forthe next decades by General Circulation Models and ecophysiologicalmodels) during 7 years to elucidate the reproductive responsesof the dominant species Quercus ilex L., Arbutus unedo L. andPhillyrea latifolia L. Soil moisture was partially reduced byplastic strips intercepting rainfall and by ditch exclusionof water runoff. During the period studied, meteorological conditionsand soil moisture were continuously monitored, together withflower and fruit production in the three dominant species. InQ. ilex and A. unedo, flower and specially fruit productionwere strongly correlated with annual rainfall, but not in P.latifolia. The experimental drought reduced flower and fruitproduction in Q. ilex by 30 per cent and 45 per cent, respectively.Reductions in flower and fruit production were not significantin A. unedo and were not observed in P. latifolia. A decreasein production of reproductive structures and the different responseof the species studied to a decrease in water availability couldinduce important changes in the competitive ability of the differentspecies and in the long term in the community species compositionand future distribution of these Mediterranean species. 相似文献
15.
海南岛霸王岭热带天然林景观中木本植物功能群划分及其潜在分布 总被引：4，自引：1，他引：3
为了解热带天然林景观中木本植物功能群及其基本分布规律,在对研究区进行千米网格样方凋查和环境因子收集的基础上,采用演替地位和最大潜在高度2个指标将579种木本植物划分为8个功能群;采用生态位模型对这些功能群的地理分布进行预测,并应用受试者工作特征分析进行模型精度验证;应用多元线性回归对影响各功能群分布的主要因子进行分析.结果表明:生态位模型对8个功能群的潜在分布预测都达到70%以上;相对于顶极类功能群,先锋类功能群具有较高的最大潜在分布面积和较低的最适分布面积,同时呈现出较为分散的格局,反映了两大类功能群个体生态学特性和对环境适应的差异;在选择的10个环境因子中,有7个因子(极端最低温、年均温、极端最高温、年均相对湿度、年均降水量、海拔和坡向)对木本植物功能群的潜在分布影响显著. 相似文献
16.
Forest biomass estimated from MODIS and FIA data in the Lake States: MN, WI and MI, USA 总被引：3，自引：0，他引：3
This study linked the Moderate Resolution Imaging Spectrometerand USDA Forest Service, Forest Inventory and Analysis (FIA)data through empirical models established using high-resolutionLandsat Enhanced Thematic Mapper Plus observations to estimateaboveground biomass (AGB) in three Lake States in the north-centralUSA. While means obtained from larger sample sizes in FIA datasetscan be used as reference numbers over large scales, remote sensing(RS)-based observations have the ability to reflect spatialvariation of properties of interest within a given area. Thus,combining two national on-going datasets may improve our abilityto accurately estimate ecological properties across large scales.Using standard and consistent data sources can reduce uncertaintyand provide more comparable results at both temporal and spatialdimensions. We estimated total forest AGB in the region was1479 Tg (1012 g, dry weight) in 2001 with mean AGB value of95 mg ha–1 ranging from 4 to 411 mg ha–1 (within95 per cent percentiles). Mixed forests featured 66 per centof the total AGB while deciduous and evergreen forests contained32 and 2 per cent of the total AGB, respectively, at 1-km pixelresolution. Spatially, AGB values increased from north-westto south-east in general. The RS-based estimates indicated agreater range in AGB variations than the FIA data. Deciduousforests were more variable (both in absolute and relative terms)than evergreen forests. The standard deviation of AGB for deciduousforests was 137 mg ha–1, or a coefficient of variationof 92 per cent, that for evergreen forests was 24 mg ha–1,or a coefficient of variation of 37 per cent. 相似文献
17.
Carbon pools and sequestration in forest ecosystems in Britain 总被引：1，自引：0，他引：1
British vegetation is estimated to contain 113.8 million tC,80 per cent of which is in forests and woodlands (91.9 milliontC). Sitka spruce plantations, although covering 21.4 per centof the forest/woodland area, contain only 8.2 per cent of theforest/woodland carbon, because the plantations are young andhave an average of only 14.1 tC ha–1. Broadleaved woodlandsin Britain have an average of 61.9 tC ha–1 and contain46.8 per cent of the total carbon in all vegetation. A breakdownis given of the carbon density (tC ha–1) and content ofdifferent tree species. A carbon density map of Britain highlightsthe concentration of carbon in the broadleaved woodlands insouthern England and in the large conifer plantations in southernScotland and northern England. Carbon storage in the trees, products, litter and soil can beevaluated in terms of long-term equilibrium storage or short-termrate of storage. These two components vary among forest typesin Britain and globally. Plantations harvested at the time ofmaximum mean annual increment (MAI) will not store as much carbonas mature, old-growth forests on the same site unless they havelong-lasting products and/or are very fast growing. Maximumequilibrium carbon storage is generally achieved by harvestingat the time of maximum MAI when the lifetime of products exceedsthe time to maximum MAI. Undisturbed peatlands sequester CO2and emit CH4, and may be greenhouse neutral. When peatlandsare drained and planted with trees, they stop emitting CH4 andstore carbon in the trees, forest litter, forest soil and woodproducts. However, these greenhouse gas ‘gains’are offset by the oxidation to CO2 of the peat, and the gainsare exceeded by CO2 losses when 20–40 cm depth of peathas been oxidized. Forests in Britain are currently sequestering1.5–1.7 million tC a–1 in trees, 0.3–0.5 tCa–1 in litter and 0.5 million tC a–1 in wood products,totalling about 2.5 million tC, equivalent to about 1.5 percent of the carbon currently emitted by burning fossil fuelsin the UK. In order to maintain the current forest carbon sink,the forest area needs to continue to expand at about 25 000ha a–1 of upland conifers or 10 000 ha a–1 of poplarson good land. 相似文献
18.
云南野生余甘子单株选优的协方差分析 总被引：1，自引：0，他引：1
为快速选择余甘子优良单株 ,项目组于 1991年初在滇中、滇西北余甘子分布区按不同海拔、坡向、年龄随机抽取 2 4 7株样木 ,并设立树龄、株高、地径、冠幅等 18项变量因子进行协方差分析、逻辑斯谛回归、因子分析以及评估选优等估算过程 ,筛选出影响余甘子品质的主导因子 ,结果为果实横径、坡向、郁闭度、冠幅、生长级、土层厚度等 6项因子对单株选优具有重要指导意义。 相似文献
19.
祁连山北坡立地因子对青海云杉树高生长的相关分析 总被引：1，自引：0，他引：1
本文以祁连山北坡青海云杉林３２块标准地资料为依据，采用通径分析、主成分分析和多元回归等方法，定量地分析了立地因子对青海云杉树高生长的影响途径及强度，建立了简单、合理的影响模型，并初步探讨了不同分析方法在立地评价中的综合应用。 相似文献
20.
Data describing the growth, survival and stem form of: a) Europeancontinental, and b) British provenances of trees native to Britainwere collated from Forestry Commission records. The growth ratesof European continental provenances of Scots pine (Pinus sylvestris),silver birch (Betulo pendula), sessile oak (Quercus petraea)and common alder (Alnus glutinosa) were inferior to those ofBritish provenances in 90 per cent of cases. European provenancesof these species also showed inferior survival. The growth ratesof continental provenances of beech (Fagus sylvatica) were superiorto British provenances in about 50 per cent of cases, provenancesfrom northern France, Belgium and Holland being the fastestgrowing. Relationships between the relative height growth offoreign provenances and latitude were demonstrated for Scotspine, silver birch and beech (relative height growth = the heightgrowth of a foreign provenance expressed relative to that ofBritish provenances at the same site). The continental provenancesthat grew best originated at 0–4° south of the latitudesof the planting sites. Relative height growth decreased bothnorth and south of these latitudes. In the case of oak, relativeheight growth did not vary widely between origins. The survivalof continental provenances of Scots pine was particularly pooron exposed upland sites. The stem form of British provenancesof Scots pine was intermediate between Fennoscandian provenancesand provenances from the rest of Europe. In oak and beech therewas generally little difference in stem form between Britishand continental provenances, but the best continental provenances(Belgian beech; French oak) were most reliable. The growth andsurvival of native trees is interpreted in the light of thepost-glacial history of these species. The implications regardingthe continued use of seed of native hardwoods imported fromcontinental Europe are discussed. 相似文献