共查询到20条相似文献，搜索用时 15 毫秒
1.
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
2.
Acorns collected from a range of Quercus robur L. and Q. petraea(Matt.) Liebl. populations were germinated and grown in an unheatedgreenhouse using a standard commercial compost. Total seedlingdry weight did not increase until the end of the growing season,with Q. robur and Q. petraea seedlings showing mean dry weightincreases of 211 per cent and 414 per cent respectively. Oakseedlings appear to depend upon cotyledon reserves of carbohydrate,P, K and Mg during most of the first year of growth, but relyon external sources of Ca. Seedlings become independent of thecotyledons at the end of the first growing season. 相似文献
3.
Sphagnum peat (peat), spruce bark compost (compost), peat +perlite (1 : 1, v : v) and compost + perlite (1 : 1, v : v)substrates were inoculated with vegetative alginate-bead inoculumof Hebeloma crustuliniforme, Hygrophorus agathosmus or Paxillusinvolutus or left uninoculated prior to the addition of Norwayspruce seed. Growth and percentage of mycorrhization of barerootseedlings cultivated in a greenhouse were evaluated after thefirst growing season. Seedlings grown in peat-based substrateshad significantly larger aboveground and total dry weight, butsignificantly lower mycorrhization percentage than those grownin compost-based substrates. There were no significant differencesbetween fungal treatments (including control) for both the percentageof mycorrhization and growth of seedlings. The artificiallyintroduced fungi were not efficient in mycorrhizal formation– naturally occurring fungi were common in all treatments.However, a significant interaction between substrate and fungustreatments in root dry weight was detected. Hebeloma-inoculatedseedlings grown in peat showed the highest value of root dryweight. This fact indicates other possible effects of the fungion root growth independent of mycorrhization. Growth parameterswere negatively correlated with the extent of mycorrhization,indicating allocation of host photosynthates to the fungi. Tothe best of our knowledge, operational inoculation of Norwayspruce seedlings with the test fungi has not been reported previously. 相似文献
4.
Comparison between empirical and theoretical biomass allometric models and statistical implications for stem volume predictions 总被引：1，自引：0，他引：1
Comparisons between empirical and theoretical allometric modelsfor estimating tree biomass and the statistical caveats attachedto empirical stem volume equations are presented in this paper.First, the elastic and stress similarity models, derived fromfirst biomechanical principles, as well as predictions obtainedfrom geometric similitude, were validated against allometricequations that relate dry above-ground tree biomass M to stemdiameter D. In addition, a recent geometric model which predictsthat M D8/3 was also validated against a pooled dataset whichconsisted of 764 M-D pairs compiled from empirical studies conductedthroughout the globe and for several tree species. Moreover,59 empirical equations which relate M to D were selected froma European database to validate the aforementioned theoreticalmodels. The analysis indicated that the biomechanical and thegeometric models failed to describe the shape in M-D allometryfor the empirical datasets. Finally, the multicollinearity problem,which is directly related to the reliability of the predictions,was analysed for stem volume equations (V). In total, 23 empiricalmodels based on the six-parameter formula V = a + bD + cD2 +dD3 + eH + fD2H were used in order to pinpoint the dependencybetween the parameters. It is illustrated that parameters a,b and c are highly related to each other, and parameter e isalso related to parameter f. It is concluded that the interrelationshipbetween D and stem height (H) could be one of the reasons forthis dependency and scepticism should be placed in the reliabilityof V estimates derived from these models. 相似文献
5.
Dwarf French beans and broad beans were grown at 0.25 m x 0.25m for 2 years with a without cuttings of Populus ‘RAP’at spacings of 2.0 m x 0.5 m and 3.0 m x 0.5 m. The presenceof beans lead to a greater height and diameter growth and greatertotal dry matter production per hectare of the Populus at bothspacings after 2 years. Bean yield was reduced at the end ofthe second year by the presence of Populus; there was no effectat the end of the first year. 相似文献
6.
Some Consequences of the 1975-1976 Drought for Dutch Elm Disease in Southern England 总被引：2，自引：0，他引：2
During the exceptionally hot, dry summer of 1976 the large elmbark beetle, Scolytus scolytus, was able to invade and successfullybreed in apparently healthy, undiseased elms. A conspicuousfeature was the clustering of wasps, bees and ladybirds on thestems, attracted by sap exudation. The trees were probably sufferingfrom drought, although many showed no symptoms. The phenomenonoccurred mainly on shallow soils over limestone; trees on chalkwere not generally affected. In 1976, and to some extent in 1975, the downward developmentof Ceratocystis ulmi through the tree was less than in previousyears, and only a low proportion of the numerous maturationfeeding wounds became infected. However the drought does notappear to have significantly influenced the course of the epidemic. The attacks by S. scolytus on undiseased trees are discussedin respect of 19th Century reports of attacks on elms, and itis concluded that the ability of S. scolytus to assume a moreprimary role may have been underestimated. 相似文献
7.
The growth of seven Picea sitchensis x Picea glauca hybridswas compared with the growth of two P. sitchensis provenancesand Picea glauca var.albertiana at two sites in northern Scotland.The sites were at Aultmore (an exposed, dry site with a mineralsoil) and Shin (a frosty, wet site with deep peat). They wereof the type considered more suited to Pinus contorta than P.sitchensis. At age 10, in 1984, most of the hybrids, at both sites, wereabout 10 and 20 per cent taller than P. sitchensis of Masset(Q.C.I.) and Ketchikan (Alaska) provenance, respectively. P.glauca var. albertiana grew very poorly, especially at Aultmore. At Aultmore, the frost hardiness of three of the tallest hybrids,the two P. sitchensis provenances, and P. glauca var.albertiana,was tested at about 3-weekly intervals throughout 1982 and 1983.Detached shoots were subjected to artificial frosts in a programmablechamber. P. glauca var. albertiana was frost susceptible atbudburst, but at all other times it was relatively very frosthardy (eg. to–10°C in mid-August). Also, the hybridswere consistently more hardy than P. sitchensis of even Ketchikan(Alaska) provenance from July onwards. However, the hybridswere less frost hardy than P. sitchensis of Masset (Q.C.I.)provenance in early spring (they dehardened a week earlier inMarch-April) and their buds were equally as frost susceptibleat the time of budburst. In 1983, trees of P. glauca var. albertianaburst their buds about a week sooner than P. sitchensis. It was concluded that P. sitchensis x P. glauca hybrids canperform better than P. sitchensis at sites considered ‘marginal’for P. sitchensis, and that their good performance may be partlyattributed to, or associated with, their greater summer andautumn frost hardiness. A programme of inter-specific hybridizationis being pursued. 相似文献
8.
Direct seeding and planting of European beech (Fagus sylvaticaL.) are two common techniques for the conversion of pure Norwayspruce (Picea abies [L.] Karst.) stands into mixed stands. Thisstudy tested whether the growth of sown beech seedlings differsfrom that of planted seedlings of two stock types. Thereforeat two experimental sites repeated measurements were made ofheight, stem and first order branch diameter on sown and plantedseedlings over a period of nine years. The results showed thatthe growth responses of planted and sown seedlings to the environmentalconditions below the canopy of overstorey Norway spruce wererather similar. No differences between planted and sown seedlingswere found in their diameter and their estimated abovegrounddry weight. For all three batches the ratio between the estimatedbranch dry weight and the estimated main stem dry weight (branch-shoot-ratio(BSR)) was increased with age. Due to intraspecific competitionBSR was lowest for the sown seedlings irrespective of theirage. Differences in growth dynamics between planted and sownseedlings were found. For example, differences in the heightor the estimated aboveground woody dry weight between sown andplanted seedlings at a given age were not constant. Height,diameter and estimated dry mass of the seedlings in relationto age could be modelled precisely by a second-order polynomialfunction in the hitherto studied period. 相似文献
9.
This experiment was conducted to evaluate the effect of seed priming on the germination and physiology of Pinus bungeana seeds.Seeds were treated by hydropriming with distilled water,halopriming with potassium nitrate (KNO 3) at 0.3,0.6,1.2 MPa respectively (untreated dry seeds were taken as control).Properties of seed germination and physiology were determined and the effect of hydro-and halopriming on germination and physiology of P.bungeana seeds were investigated.The results showed that,compared with control,each priming treatment had increased the germination percentage (GP) and germination index (GI),shortened the mean germination time (MGT) and the time required for 50% of the seeds to germinate (G 50).Primed P.bungeana seeds significantly decreased the relative conductivity and the amount of malondialdehyde (MDA).Of all the treatments applied to seeds of P.bungeana,halopriming at 0.3 MPa KNO 3 produced the highest GP (65.0%) and the shortest MGT (18.8 d) and G 50 (18.2 d). 相似文献
10.
- Equilibrium in the moisture content of the stem appears to bereached at a given percentage of saturation rather than at apercentage based on the dry weight, and this method of expressingmoisture content eliminates many of the fluctuations apparentwith the latter.
- Summer moisture content in Sitka spruce (Piceasitcbensis, Carr.)was highest on the site with the highestrainfall and lowestwith the lowest rainfall. It decreased inlate summer, suddenlyin Sitka spruce (in August) and graduallyin Douglas fir (Pseudotsugataxifolia Brit.).
- There was asharp moisture gradient from cambium to heartwood,the saturatedzone being very narrow except on the wet Sitkaspruce site.In the Douglas fir it appeared that water couldbe withdrawnfrom the layers just behind the transpiration streamfasterthan it could be replaced, leaving this zone drier thanthesurrounding layers.
- Lateral root pruning in Douglas fir ledto the drying out ofa narrow strip of tissue in the stem.
11.
Morecroft Michael D.; Stokes Victoria J.; Taylor Michele E.; Morison James I.L. 《Forestry》2008,81(1):59-74
Sycamore (Acer pseudoplatanus L.) is an invasive, non-nativespecies in Great Britain and its management in conservationareas is controversial. Climate change adds further uncertaintyto decision making. We investigated the role of management historyin determining present-day abundance and the effects of climaticvariability on growth, photosynthesis and phenology at WythamWoods, a UK Environmental Change Network (ECN) monitoring site.Relatively few sycamore trees were found in undisturbed ancient,semi-natural woodland and recent plantations, despite beingcommon in other areas of the site. Sycamore grew more slowlythan ash (Fraxinus excelsior L.), its principal competitor,but at a similar rate to pedunculate oak (Quercus robur L.)in the period 1993–2005. There were fewer sycamore thanash seedlings, regardless of which species dominated the canopy.Growth of sycamore was slower in dry periods than wet ones andlower photosynthetic rates were measured in canopy leaves underdry compared with wet soil conditions. This study thereforesuggests that sycamore does not present a serious threat toundisturbed ancient woodland on the site and that it may eventuallydecline in areas of the site where it competes with ash, inthe absence of disturbance. It may also decline under climatechange if summer droughts become more frequent. 相似文献
12.
Two methods of biometrical analysis were used to characterizea collection of 178 leaf samples assembled in the course ofan all-Wales survey of elms made in 1977–78. All sampleswere referable to either U. glabra, U. minor var. minor, U.minor var. vulgaris (= U. procera)orU. x hollandica. The variationwithin each taxon is described. Elm regions are demarcated tosupplement those already described for England. U. glabra isthe only elm believed to-be native. It is thought most likelythat the main Welsh population of U. minor var. vulgaris, inGlamorgan, was introduced from Somerset some time before theNorman Conquest. U. minor var. minor is rare throughout Walesand could be of 18th century origin; its possible spread alongdrovers' routes is considered. Some notomorphs of U. x hollandicamust have been introduced as such. Others probably arose inWales from hybridization involving U. glabra, U. minor var.vulgaris and U.x hollandica var. hollandica. 相似文献
13.
An experiment in Helmsdale Forest (Highland Region, Scotland)examined the effects of shelter and weed competition on Sitkaspruce (Picea sitchensis (Bong.) Can.) and lodgepole pine (Pinuscontorta Douglas ex Loudon). Different levels of shelter fromwind were achieved by using netting and were measured usingtatter flags. Three treatments compared weed competition byremoving no vegetation, heather (Calluna vulgaris L.) only orall ground vegetation respectively. Results indicate a definiterelationship between material lost from tatter flags and treedry weight at five years. Even the smallest increase in shelterresulted in increased growth of Sitka spruce and the beneficialeffect of shelter became most apparent 4 to 5 years after planting.Tree dry weight was found to be correlated with root collardiameter and height but not fifth year height increment. Resultsfrom weeding treatments were unclear and differed between species.This was because bird damage interacted with weeding, the completelyweeded plots being most heavily damaged; and because the methodof hand weeding (pulling out the whole plant including roots)damaged fine tree roots. Bird damage was prevented by nettingbut in unnetted plots it was found impossible to separate birddamage from other factors although it was clearly more seriouson lodgepole pine. 相似文献
14.
The nature of the differences between the climates of the QueenCharlotte Islands and of England and Wales are discussed briefly.The author then examines the site tolerance of the principalspecies within their own natural range, comparing particularlythe place of Sitka spruce (Picea sitcbensis Carr.) in the foreston Graham Island with its place around Terrace and describingthe Douglas fir forests of the drier eastern side of VancouverIsland and the place that Sitka spruce has in them. Factorsaffecting the growth of Douglas fir (Pseudotsuga taxifolia Brit.)are discussed. It is suggested that care is needed before itis assumed that a markedly dry summer period such as occursin much of the Douglas fir region entails a ‘dry’period as regards supply to the tree. Illustrations are givenfrom eastern North America of changes in type of site occupiedby a species with change in climatic or edaphic environment.Observation of the relative position of a species in the forestas climate changes makes it possible to suggest the place ofSitka spruce and Douglas fir in Great Britain. 相似文献
15.
The development of ploughing, draining, planting, and the useof turfs and of phosphate is considered in detail for each oftwo main types. For Molinia lands, the 1952 technique securesadequate drainage and a very considerable turnover of turf,and here the spruces Picea abies Karst. and P. sitcbensis Carr.remain the first choice. For Calluna lands, the developmentof methods and the choice of species is more difficult. Thespruces refuse to grow pure and unnursed on the poorer Callunatypes and the use of Scots pine (Pinus sylvestris L.), P. contortaDoug., the Mountain pine (P. uncinata Ramond), Japanese larch(Larix leptolepis Gord.), and Douglas fir (Pseudotsuga taxifoliaBrit.) is discussed. The main requirements for successful afforestationof these ground types are summarized. 相似文献
16.
This biometrical study is based on a collection of nearly 500leaf samples from every ancient parish in the county. Most ofthe elms could be assigned to one of nineteen groups, 9 of U.carpinifolia, 1 of U. glabra, 2 of U. procera, 3 of putativeF1 U. carpinifolia x U. glabra, 3 of U. carpinifolia with suspectedintrogression from U. glabra, and 1 of U. carpinifolia x U.procera. U. glabra is indigenous. Most of the U. carpinifolia appearto have spread out from six centres of origin, mostly near thecoast. These elms are very similar to forms now occurring innorth-west France, and it is thought probable that they wereintroduced from there, possibly by the settlers responsiblefor the Red Hills salt workings shortly before the Roman occupation.One group of U. carpinifolia came from Cambridgeshire via theEssex branch of the river Cam. Of the two main populations ofU. procera, that characteristic of south-east Essex is believedto have come from northern Kent, probably from the Hoo peninsula,while the group found in south-west Essex is probably a laterintroduction from further west. Hybridization between introduced U. carpinifolia and nativeU. glabra has occurred on a very large scale and putative F1hybrids extend in a broad band across the county from the Hertfordshireborder to Suffolk. This hybridization most likely occurred duringthe clearing of the heavily forested part of northern Essexin pre-Conquest times. Subsequently, back crossing occurredbetween these hybrids and U. carpinifolia. Occasional hybridizationalso seems to have occurred between U. procera and the othertwo species. An outline of the probable history of the elm in eastern Englandas a whole concludes the paper. 相似文献
17.
Between 1975 and 1982 a study was made of the invertebrate faunacolonizing two deciduous species of southern beech, Nothofagusobliqua and N. procera, introduced into Britain from South America.Special attention was paid to the folivorous larvae of Lepidopterawhich were sampled at 15 localities in southern England, mostlyin Forestry Commission trial plots and arboreta in Gloucestershire. The literature describing the native insect fauna of Nothofagusin Chile and Argentina is briefly reviewed. Mention is alsomade of the few previous records of lepidopterous larvae observedfeeding on Nothofagus in Britain. The larvae of 81 species Lepidoptera are recorded from Nothofagus.Seventy-eight of these were feeding on the foliage, of which73 were found on N. procera and 62 on N. obliqua, although approximately62 per cent of all the larvae collected were from N. obliqua.Faunal differences between the sites studied are briefly described.Two additional species of cutworm larvae are also reported attackingthe roots of Nothofagus seedlings. The changing lepidopterous fauna on Nothofagus from May untilSeptember is described and discussed. Spring-feeding larvaeof Operophtera brumata (L.), Agriopis aurantiaria (Hübn.)and Erannis defoliaria (Clerck) comprised 55 per cent of alllarvae collected on the two hosts, and represented between 68per cent and 87 per cent of those larvae in beating samplescollected in late May and early June. Most of the larvae collected were reared to adult in the laboratoryon a diet of Nothofagus leaves. The majority of these are regardedas polyphagus species although 64 are known to have one of thetwo native Quercus as a host-plant, while 24 have been recordedas feeding on Fagus sylvatica. The relevance of these two generaas sources for the Lepidoptera fauna colonizing Nothofagus isdiscussed. Nothofagus obliqua and N. procera are shown to have acquireda substantial lepidopterous fauna since their introduction intoBritain near the beginning of this century, although most ofthe trees sampled were less than 25 years old. These two speciesof Nothofagus may be vulnerable to defoliation by several speciesof caterpillar, especially if planted as monocultures in areaswhere oak and beech are plentiful. However, their surprisinglylarge insect fauna may be seen to have some value for natureconservation purposes. 相似文献
18.
The selective herbicide clopyralid is often used to controlcompeting Cirsium arvense in newly planted woodlands. When appliedas an overall spray at different dates in the spring (at 0.2kg acid equivalent (a.e.) ha–1) to 10 tree species (Fraxinusexcelsior, Prunus avium, Quercus robur, Acer pseudoplatanus,Populus x canadensis cv. ‘Ghoy’, Pseudotsuga menziesii,Pinus nigra ssp. laricio, Larix kaempferi, Picea abies and Piceasitchensis) it did not reduce survival, and had little effecton growth. However, some species showed distortion of the youngestsprayed leaves or needles for several weeks after treatment,particularly F. excelsior, L. kaempferi and P. x canadensis.Sequential applications of clopyralid (first at 0.1 kg a.e.ha–1 followed by 0.2 kg a.e. ha–1 after 3 weeks),which are often required to control C. arvense, did not leadto increased leaf damage or growth reduction. Mixtures of clopyralidwith selective graminicides (cycloxydim at 0.45 kg active ingredient(a.i.) ha–1; fluazifop-p-butyl at 0.38 kg a.i. ha–1and propaquizafop at 0.15 kg a.i. ha–1) did not causesignificant adverse effects on survival or growth of any species.If herbicides are required to control mixed stands of susceptibleproblem weeds such as C. arvense and grasses which are overtoppingyoung trees, these herbicide mixtures, applied as overall sprays,are less likely to cause damage to trees than attempts to usedirected applications of broad-spectrum foliar-acting herbicides. 相似文献
19.
Biomass production and allometric above- and below-ground relations for young birch stands planted at four spacings on abandoned farmland 总被引：4，自引：0，他引：4
The objective of the study was to quantify above- and below-stumpbiomass of silver (Betula pendula Roth) and downy (Betula pubescensEhrh.) birches planted at four spacing intervals and growingon two soil types on an area of farmland. The 12-year-old bircheshad been grown at four spacings (1.3, 1.5, 1.8 and 2.6 m) ontwo sites: one on medium clay soil and the other on fine sandsoil. The dry weight of the stem, branches, leaves, stumps androots was estimated by drying and weighing sub-samples. Theprojected leaf area (PLA) m–2 of trees, leaf area indexof stands and basic density (kg m–3)of stems were alsoestimated. A significant greater dry weight of stem, branches,stump and roots and species and spacing for pendula birch werefound. The root length of silver birch was significantly greaterthan that for downy birch and for both species the root lengthwas greatest at the widest spacing (2.6 m). There was also asignificant difference between leaf weights of birch of thesame species growing on the two soil types. Significant differenceswere also found between PLA and species, and for both species,between PLA spacing. Basic density of stems was significantlydifferent between soil types. Equations for estimating the above-groundbiomass and root biomass from diameter at breast height weredeveloped for birches growing on fine sand and on medium claysoils. The total biomass production per hectare on fine sandwas higher for silver birch (19.9–65.9 tonnes ha–1),than for downy birch (13.0–48.3 tonnes ha–1). Onmedium clay soil, total biomass production for silver and downybirches was 30.8–52.8 and 16.8–42.8 tonnes ha–1,respectively. 相似文献
20.
Pinus nigra Arnold var. pallasiana Endl. and Abies equi-trojaniAschers-Sinten are indigenous species of Turkey. The area ofPinus nigra is very large (more than 2 million hectares) occurringin the west, south and north of Turkey. However, Abies equi-trojanioccurs only in the west of Turkey in the Ida Mountains (Kazdagi)and is of limited area (5500 ha).These two species naturallyform both mixed stands and pure stands in the Ida Mountains. When mixed stands of Pinus nigra and Abies equi-trojani areregenerated, if the seedlings of these two species regeneratesimultaneously, the Pinus nigra will be eliminated from thestand in 15 to 25 years because of the rapid growth of Abiesequi-trojani. In different site conditions, Abies equi-trojanireaches 22–30 m in height and 40–65 cm in diameterin 70 years, whereas Pinus nigra reaches 17–22 m in heightand 25–40cm in diameter in the same period in the sameforest sites. 相似文献