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1.
The effects of the number of chromosome sets on chlorophyllcontent in diploid and tetraploid black wattle were assessedthrough chlorophyll absorbance. Seedlings of 8 months of age,1-year-old trees in polybags and 2-year-old field material wereselected for this investigation. Three families per ploidy levelcomprising of 10 half-sibs per family were used in the analysis.An analysis of variance revealed significant differences (P< 0.05) in chlorophyll absorbance between diploid and tetraploidmaterials ( = 0.375 and = 0.653, respectively). Significantdifferences (P < 0.05) between treatments (seedling, baggedmaterial and field material) within each ploidy level were recorded,where chlorophyll absorbance increased from diploid bagged trees( = 0.343) to seedlings ( = 0.375) to field trees ( = 0.408). Similar significant increases were recordedfor the tetraploid seedlings ( = 0.629) to bagged trees ( = 0.644) to field trees ( = 0.686). Significant differences (P < 0.05) were also recordedbetween genetic lines within both ploidy levels. However, whencomparing families within each ploidy level, with respect totreatment differences, in most cases, two of the three familiesshowed no significant differences (P > 0.05). Within eachfamily, significant differences (P < 0.05) were recordedbetween each of the three treatments tested, with the fieldmaterial consistently having significantly (P < 0.05) greateramounts of chlorophyll. 相似文献
2.
Stands of clonal Salix viminalis (in 1985) and Populus trichocarpa(in 1986) were grown for one growing season from cuttings incontainers, at 0.3 m spacing, supplied with trickle irrigationand nutrients. Woody biomass production (Bw) in the first yearwas analysed as the product of the proportion of dry matterpartitioned to wood ({macron}), the seasonal mean efficiencywith which intercepted light was used to produce dry matter({macron}), the mean fraction of incident light interceptedby the canopies (f{macron}), and the amount of incoming solarradiation over the season (A). Thus, Bw = {macron}f{macron}{macron}A. For Salix, Bw=10 t ha–1y–1, while for Populus, Bw= 5 t ha–1y–1, mainly because of differences in{macron} and f{macron}. The Populus partitioned more dry matterto roots (and correspondingly less to stems) and interceptedless light over the growing season. The Salix and Populus cloneshad surprisingly similar ({macron}) values, namely 1. 58 and1. 50 g MJ–1, respectively (based on total dry matterand total solar radiation), which are very like the {macron}values measured on C3 agricultural crops in Britain. Also, theSalix and Populus clones produced canopies with similar lightextinction coefficients and hence similar relationships betweenfractional interception and leaf area index. 相似文献
3.
Oyen Bernt-Havard; Blom Hans H.; Gjerde Ivar; Myking Tor; Saetersdal Magne; Thunes Karl H. 《Forestry》2006,79(3):319-329
Results from a literature review on pinewood ecology, silviculture,genetics, aspects of history and forest resources of Scots pine(Pinus sylvestris L.) in western Norway are presented. The pinewoodscover 40 per cent of the forested land, 0.31 million ha. Duringthe last 75 years, the area has increased by 17 per cent andthe growing stock has risen from 10 to 34 million m3. The impactof man in previous times was very marked, and has had a significantinfluence on the present forest conditions. The pronounced climaticgradients mixed with the topographic variation – fromthe coastal plains via the fjord systems to the high mountains– is reflected in rather steep gradients in the pine forestvegetation. Various floristic elements can be distinguished,from oceanic via the suboceanic in the outer islands to thethermophytic, boreonemoral and boreal elements in the innerfjord districts and valleys. The introduction of spruce (Piceaspp.) plantations on 10–15 per cent of former native pineforests has not negatively affected the bird fauna at the landscapescale. Although not particular species rich, the pine forestsharbour species usually not found in other forest types. Sofar, most work in the field of silviculture and forest ecologyin the pinewoods of West Norway has been in the form of casestudies. Implications of the results for forestry in the regionare briefly discussed. 相似文献
4.
Observations to follow the development of 2-year-old oak seedlingstook place over a 6-year period at a fenced site within a maturestand of oak in southern England. Bramble and bracken were abundant,but the cover of other species was low. Although seedlings doubledin height, only 13 per cent survived and few were taller thaneither bramble or bracken. The initial number of seedlings wasinversely related to both canopy cover and distance to the nearestparent tree. The final number of seedlings could be predictedfrom the initial percentage covers of bramble and bracken, andeither the overstorey canopy cover or the initial number ofseedlings. The average annual rate of seedling mortality, whichwas 25–50 per cent, was significantly influenced by thevegetation present. Grass was positively related to survivalwhereas there was an inverse relationship with both brambleand bracken cover. Models estimated 80 per cent annual seedlingsurvival at 25 per cent bramble cover but only 50 per cent at60 per cent cover. Although grasses can be competitive species,results indicate that oak seedling establishment may be betterin areas with a ground flora comprising grass. 相似文献
5.
Armillaria ostoyae is an important disease of Pinus pinasterin north-west Spain, which kills trees following a heterogeneousspatial structure. In a progeny trial of P. pinaster seedlings,spatial heterogeneity and autocorrelation of neighbour mortalitycaused by A. ostoyae impeded proper analysis of the diseaseincidence. We used variography and kriging methods to describethe spatial distribution of the infection probability and thegenetic variation of the resistance to A. ostoyae among families.The spatial structure of disease incidence was modelled, andthe probability of survival was corrected by kriging at eachtree location. Cumulative mortality 3 years after planting was65.1 per cent. Significant differences among P. pinaster familiesin terms of mortality to A. ostoyae were found, with low individual(h = 0.08) and moderate family (h = 0.35) heritability estimates. According to a theoretical semivariogram, the patch size ofthe disease incidence was 63 m wide. This is the first timevariography and kriging are used to select P. pinaster resistantto Armillaria root rot. It is concluded that geostatistics providesforest pathologists with a powerful tool for screening resistanttrees in field conditions. 相似文献
6.
Possible Impacts of Climatic Warming on Trees and Forests in the United Kingdom: a Review 总被引：2，自引：0，他引：2
There is growing evidence and concern that increasing levelsof greenhouse gases in the atmosphere will increase global temperatures.Temperatures in the UK may increase by 3C± 1.5C overthe next 70 years The tree crop is sensitive to such large andrapid climatic change because of its longevity. This paper reviews(1) changes that might occur in the forest environment, includingsoil, following climatic warming; (2) past and future long-termchanges in the species composition of UK forest; (3) possiblepositive and negative effects.of climatic warming on the growthand yield of UK forests; and (4) the vulnerability of foreststo any change in the frequency of extreme events. 相似文献
7.
Effect of Desiccation on Water Status and Forest Performance of Bare-rooted Sitka Spruce and Douglas Fir Transplants 总被引：3，自引：0，他引：3
Sitka spruce transplants which had been exposed to drying conditionswere assessed for shoot water potential (), shoot moisture content(MC), water saturation deficit (WSD) and root moisture content(RMC) before forest planting. Exposure for 1 hour 44 minuteshad no effect on subsequent survival or growth, but exposurefor 3 hours 18 minutes reduced survival to 68 per cent aftertwo years and significantly reduced height growth. The damagedplants were clearly distinguished at the time of planting by and RMC but not by MC or WSD. After a range of desiccation treatments, survival was high inSitka spruce unless RMC had fallen below 180 per cent but survivalwas reduced in Douglas fir with smaller reductions in RMC or. During the desiccation treatment, Douglas fir started withand maintained a higher RMC than Sitka spruce and reached lowlevels of less rapidly. The poor performance of desiccatedDouglas fir was therefore not the result of an inability toconserve water. After rewetting for one hour in the dark RMC was restored butnot , and there was no significant effect on survival or growthin either species. It may be possible to devise a method to establish when plantsare in poor condition by direct or indirect measurement of RMC,but high levels of RMC can be misleading if rewetting has occurred. Handling systems which involve brief periods of exposure aretolerable for Sitka spruce but not for Douglas fir, and specialmeasures are justified to ensure that the latter species isnever subjected to root desiccation during handling. 相似文献
8.
The study aimed specifically at investigating if canopy opennesswas a better predictor of the height growth of Norway spruce(Picea abies (L.) Karst.) advance regeneration than overstoreybasal area or overstorey standing volume. In 1990, a field experimentwith 3 x 2 factorial design and two replications (blocks) wasestablished in an uneven-aged Norway spruce forest. Plots hada net plot area of 30 x 30 m, each with a 10-m-wide treatedbuffer zone. Three overstorey density levels retained approximately15, 40 and 70 per cent of the pre-harvest overstorey standingvolume and were allotted to the plots. Two types of thinningthat harvested smaller trees or harvested larger trees wererandomly allocated to each pair of overstorey density plots.In mid-June 2000, canopy openness was estimated from hemisphericalphotographs taken at five marked points in the centre of eachof the plots at 0.9 m from ground to the top of the ‘fish-eye’camera lens. Regression results showed that canopy opennesswas a better predictor of height increments of spruce seedlings(0.1< height < 0.5 m), saplings (0.5 height < 2.0m), and small trees (height 2.0 m, diameter at 1.3 m height< 5 cm) than with overstorey basal area (m2 ha–1) oroverstorey standing volume (m3 ha–1). The height incrementof the spruce advance regeneration was not significantly correlatedto stand basal area or to standing volume. Overstorey basalarea in the net plots was significantly negative (P 0.05) withmean canopy openness estimates, and the r2 value was 0.40. Resultsindicated that basal area was not linearly related to canopyopenness as it increased, which might explain the lack of predictivepower of retained basal area on spruce regeneration height indense stands in boreal Sweden. 相似文献
9.
The role of forests in absorbing atmospheric carbon has beenrecognized under the Kyoto Protocol, which allows signatorycountries to use forests as a mitigation option. Although severalstudies have estimated carbon stock changes in Japanese forests,most only estimate changes up to 1995 or ignore carbon stockchanges in natural forests. This study is the first attemptto estimate carbon stock changes in Japanese forests from 1966to 2012, to coincide with the final year of the Kyoto Protocol'sfirst commitment period. Forest area and growing stock datawere analysed. Then, two models for predicting the change inforest area and growing stock were developed. Results showedthat most natural forest loss resulted from conversion to plantationforest. The total above-ground and below-ground carbon stockin Japanese forests has been estimated to have increased from1114.8 TgC in 1966 to 2076.0 TgC in 2012, representing an increaseof 20.9 TgC year-1 over the same period. During the first commitmentperiod of the Kyoto Protocol (2008–2012), annual carbonsinks were estimated at 20.1 TgC, of which 76.9 per cent weresequestered in plantation forests. Of the 20.1 TgC year-1, eligiblecarbon sinks are estimated at 10.2 TgC or 78.7 per cent of themaximum or capped amount as allowed under the Marrakesh Accord.Although further effort is needed so that the capped amountof 13 TgC year-1 could be achieved, this study suggests thatcarbon sinks through forest management could be used to offsetindustrial carbon emissions. 相似文献
10.
The rate of interest to be used for calculations in forestryunder Danish conditions (3 per cent) has beeen determined asthe long-term effective first mortgage rate (4 per cent) lessthe long-term average inflation (1 per cent) and the averageannual relative rise in prices of forest products ( per cent). A comparison shows that agriculture pays a real net return ofabout 3 per cent (about 3 per cent for larger farms). A comparisonwith the profit on shares seems to show that, according to Danishinvestigations, these yield a real profit of about 4 per cent. The rate of interest in forestry-a very safe type of investment-whichwe have estimated to be about 3 per cent of the market value,seems on the whole to fit well into the general real returnlevel in this country. Similarly the average real interest cost of second mortgageloans has been investigated and proved to be about 4 per cent.For forest owners having bank loans secured by third mortgage,the real interest cost of these is presumably 5 per cent ormore, but varies from person to person. A figure shows real interest costs at various degrees of indebtedness. The majority of Danish forests have a rate of interest of about3 per cent, or sometimes less (this applies to some unencumberedestates). So far, only few larger forests have a rate of interestof about 4 per cent. A rate of 5 per cent or more is mainlyseen in very small forests. 相似文献
11.
The paper discusses the results obtained to date from a uniqueseries of Norway spruce spacing plots established in 1910 inBavaria. There is a series often plots covering initial spacingsranging between 3 ft. 7 in. and 6 ft. 7 in. and an eleventhplot, spaced at just over 13 ft., and interplanted 6 years laterat 3 ft x 3 ft. The plots have only been twice thinned and havesuffered no windfall in spite of their rapid growth. The results of the latest assessment by Prof. Vanselow, in 1949,have been summarized in a recent German forestry journal, andin the present paper extracts from Vanselow's data have beenconverted into English units. Although spacing has had no apparent effect on height growth,other factors such as B.H. girth, form of stem, branching, andaverage volume per tree show the expected response to increasedspacing. There is some indication of a reduction in total yieldto date with increasing spacing in the main series of plots.The plot spaced at 13 feet has many features of special interest,inter alia the death by suppression of 97 per cent, of the plantsused to fill up. Vanselow concludes that the optimum initial spacing for spruceon similar sites lies within the narrow range of 4 ft. 6 in.and 5 ft. 3 in. This accords closely with current Forestry Commissionpractice. Received 1 April 1951. 相似文献
12.
《Forestry》1979,52(1):107
David WHITEHEAD 1978 Forestry 51, 137–149. Equation (3)on page 144 should read: 相似文献
13.
《Forestry》1933,7(2):155
IT is regretted that the legend of the text-figure on page 46of vol. vii, No. I was wrong. It should read as follows: Zone in which capillary stream is dominant. Zone in which percolating stream is dominant. Zone of intensity of interaction and initial horizon formation.# 相似文献
14.
In a disk from the stem of a very fast-grown Douglas fir (Pseudotsugataxifolia Brit.), 19 years old, with an almost constant ring-widthof about inch, the density of the individual rings was almostconstant from pith to bark and there was no sign of any increaseoutwards such as was found by Turnbull in fast-grown South Africanpines. Similar results were also obtained with more closelygrown material (mean ring-width about 1 1/0 inch). There appearedto be no general relation between density and ring-width, butthe highest densities occurred in rings less than 6 mm. widein the centre of the fast-grown tree and at the outside of atree with access to river water. 相似文献
15.
This paper shows that head fires spread in cribs and in controlledburns in gorse and heather (in the New Forest) at similar rates,R, given by
where is the bulk density of the burnt fuel and U is the wind speed in m/s. Although the values of U were similar, the values of differed by more than an order of magnitude betweenthe two types of fire. The constant of proportionality is roughly0.07 kg/m3 for the wildland fuels and 0.05 kg/m3 for cribs.The similarity of the relationships is perhaps more significantthan the agreement between the coefficients, which appears closerthan it really is since the cribs were drier than the wildlandfuels. Assuming a wind speed of 10 mile/h the constant for theGreat Fire of London (1666) was also about 0.05 kg/m3. A comparison between the flames in the controlled burns anda partly theoretical correlation of flame lengths from burningcribs has been partly successful and the duration of flamingof a piece of fuel has been empirically correlated with moisturecontent, though the general effects of moisture on the rateof spread are not satisfactorily accounted for. The reason forthis and other anomalies is probably the relatively few datafor wildland head fires (ten in all) and the fact that theirfuel composition was not uniform. The author uses many of theresults of the work described in an earlier paper in Forestry(Thomas, 1967) to derive heat balances for head fires and todiscuss the theoretical aspects of the above expression. 相似文献
16.
We studied the effect of afforestation on soil CO2 emissionsin blanket peat. The study sites were as follows: two undrainedblanket peatland sites, six sites which had been drained andafforested 3, 19, 23, 27, 33 and 39 years previously, and twoforest sites which were clearfelled in summer 1996. Soil CO2emissions were measured using the soda-lime method during 13sampling campaigns throughout 1997. Each campaign consistedof two consecutive 24-h measurements. Comparison of the averageannual CO2 emission revealed no clear pattern in relation tosoil type and suggests that afforestation does not always leadto an increase in soil CO2 emissions. In the most recently forestedsite, CO2 emissions were 1.7 t C ha–1 a–1 and drainagehad failed to lower the water-table sufficiently to cause alarge increase in CO2 emissions. In the 19-, 23-, 27- and 33-year-oldsites soil CO2 emissions were 1.0–1.4 t C ha–1 a–1and were similar to, or lower than, levels in the undrainedsites. In the 39-year-old site average CO2 emissions were 2.6t C ha–1 a–1. In the clearfelled sites CO2 emissionswere lower at between 1.4 and 1.6 t C ha–1 a–1.Root respiration appears to account for a large proportion ofCO2 emissions, and blanket peat, despite drainage, is resistantto decay. It is concluded that losses of soil C are compensatedby C uptake by the trees. 相似文献
17.
Zhang Gong; Zeng Guang-Ming; Du Chun-Yan; Jiang Yi-Min; Su Xiao-Kang; Xiang Ren-Jun; Huang Lu; Xu Min; Zhang Chang 《Forestry》2007,80(2):211-221
The chemistry and deposition pattern in bulk precipitation andthroughfall (TF) were examined and evaluated based on the 3-yearobservations in Shaoshan subtropical deciduous-conifer mixedforest in central-south China. The TF chemistry was notablychanged when passing through canopies, which probably was attributedto the dry deposition (DD) on leaf surface and the canopy exchanges.Base cations' (Ca2+, Mg2+ and K+) fluxes were significantlyenriched in TF, in particular for K+. The annual K+ canopy exchangewas 12 times larger than DD, and canopy exchange of Ca2+, Mg2+and K+ was four times as high as the DD. The canopy exchangeof base cations in association with weak acid accounted for28.4 per cent of total leached base cations, which was one ofthe important factors to modify the TF chemistry. 相似文献
18.
We compared shade tolerance of maple, ash and beech in the saplingstage from two sites with rich soils differing in water supply,growing in dense thickets underneath a beech shelterwood ofvarying canopy densities. Shade tolerance was described by twocomponents: mortality in shade and height growth in high light.At low light, beech showed the least mortality, maple the highestand ash in between on both sites. The decline with increasinglight was steepest in beech and more gradual with ash and maple.At 15 per cent above canopy light, all three species approachedzero mortality. Beech as the most shade-tolerant species hadthe highest survival rate under low light and the least lengthgrowth rate under high light (>17 per cent). Ash had a lowersurvival rate at low light than beech and a highest growth rateat high light. Maple showed a bit weaker trade-off with thelowest survival rate but a growth rate inferior to ash. On thebetter water-supplied site, height growth was significantlysuperior in all three species only under high light. On thebasis of these results, silvicultural conclusions are drawnwith respect to appropriate light levels and cutting types. 相似文献
19.
The scale and distribution of American grey squirrel (Sciuruscarolinensis) bark-stripping damage to beech (Fagus sylvatica)stems was monitored in a mixed broadleaved woodland retainedas a Research Natural Area through the use of permanent transects.During an initial outbreak of debarking damage in 1983 almostone-third of beech individuals 4 cm d.b.h. in stands of 40 years'growth were badly damaged and by 1993 this level of damage hadrisen dramatically to over 50 per cent. One-third of badly damagedindividuals in 1983, including a number of potential canopydominants, died during the decade, but some that survived grewvery vigorously. Throughout squirrels preferentially debarkedintermediate sized (10–25 cm d.b.h.) stems in particularparts of the stands aged 40–50 years, apparently tendingto select stems that were growing rapidly. Other species andstand areas of <100 years' growth remained largely unscathed.Within the 10-year period squirrels had critically affectedthe successional development of the wood. 相似文献
20.
Socio-economic status of boreal communities in Canada 总被引：1，自引：0，他引：1
The boreal forest region contains nearly 20 per cent of theworld's forest resources. Canada contains 30 per cent of theworld's boreal forest and the future of Canada's boreal regionhas been the subject of spirited debate, with some advocatingmore extensive and intensive harvest, while others argue forincreased protection. Since the boreal region lags behind Canadaas a whole on most indicators of socio-economic status, argumentsfor expanded harvest and for increased protection invoke theneed to sustain human communities. To provide context for thesediscussions, we use Census of Canada data to examine the relationshipbetween forest dependence and socio-economic status in the borealregion, and whether this relationship has changed over time.Controlling for other forms of economic development and place-specificcharacteristics, we find mixed results of forest dependenceon socio-economic status. The forest industry plays a relativelysmall role in direct employment and labour income. Forest dependenceis associated with increased income (especially in the lumberand pulp sectors), but relatively unstable employment. Examiningthe trend data, the forest industry appeared to have the greatestpositive impact on socio-economic status in 1996, with a subsequentdecline in 2001. Results signal a need for multi-faceted policydevelopment associated with intensive management zones for industrialexpansion and additional protected areas to support, in part,the maintenance of traditional activities such as trapping andfishing. 相似文献