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1.
It is estimated that British peatlands, excluding lowland fens,contain about 3000 million tonnes of carbon, 76 per cent ofwhich is in deep peats (> 45 cm deep) and 9 per cent of whichhas been drained and planted with trees. Undisturbed peatlands emit CH4 but accumulate CO2-derived carbon.The net greenhouse effect may be near zero. Peatland drainagevirtually stops methane emission and increases CO2-carbon lossthrough aerobic decomposition, but can also increase CO2-carbonfixation by the peatland vegetation partly through microbialmineralization of nitrogen, resulting in either a net loss orgain in CO2-carbon. Planting conifer forests leads to an accumulation of CO2-derivedcarbon in the trees, wood products, litter and forest soil upto equilibrium values, totalling about 16.7 kg C m2 forPicea sitchensis, Yield Class 12. Deep and shallow peats inthe British uplands contain about 0.47 and 0.80 kg C m2per centimetre depth, respectively. Thus, the 16.7 kg C m2that is stored by P. sitchensis (Yield Class 12) is equivalentto the carbon stored in about 35.5 cm of deep peat or 20.9 cmof shallow peat. If forests are planted on peats substantiallydeeper than this, there could be a net loss of CO2-carbon inthe long term. Scenarios are presented for the time course of CO2-carbon gainand loss when peatlands are drained and planted with conifers.If CO2 loss rates from drained peats are 50100 g C m2a1 there is likely to be increased carbon storage inthe whole system for at least three rotations; but if CO2 lossrates are 200300 g C m 2 a1 increased storagemay be restricted to the first rotation, after which there isa net loss of carbon. 相似文献
2.
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 ha1. Broadleaved woodlandsin Britain have an average of 61.9 tC ha1 and contain46.8 per cent of the total carbon in all vegetation. A breakdownis given of the carbon density (tC ha1) 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 gainsare offset by the oxidation to CO2 of the peat, and the gainsare exceeded by CO2 losses when 2040 cm depth of peathas been oxidized. Forests in Britain are currently sequestering1.51.7 million tC a1 in trees, 0.30.5 tCa1 in litter and 0.5 million tC a1 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 a1 of upland conifers or 10 000 ha a1 of poplarson good land. 相似文献
3.
Productivity and site data from 187 temporary sample plots wereanalysed by multiple regression analysis to derive models inwhich site variables accounted for 7886 per cent of thevariation in Sitka spruce productivity (General Yield Class,GYC). Climatic variables (accumulated temperature and windiness)extrapolated from meteorological data and tatter flag resultsaccounted for up to 78 per cent of the variation, the contributionof edaphic factors being small. The best regression models wereassociated with confidence limits of about ± 2.5 m3 ha1y1 and the mean error for predicting GYC for a forestblock (acquisition) was calculated to be ±1 m3 ha1y1 These figures were confirmed by the results of a validationsurvey and the application to field prediction of productivityis described. 相似文献
4.
The effect of geographical variation of planting rate on the uptake of carbon by new forests of Great Britain 总被引:1,自引:0,他引:1
The planting rates from 1921 to 1996 of new coniferous and broadleavedforests for 11 regions of Great Britain were assembled for thestate and private sectors. Over that period new planting totalled231 kha of conifers and 132 kha of broadleaves in England, 141kha of conifers and 16 kha of broadleaves in Wales and 881 khaof conifers and 52 kha of broadleaves in Scotland. These time series and regional values of Yield Class were usedas input data for an accounting model of carbon in the trees,litter, soils and products to produce estimates of their netuptake of carbon by the forests from the atmosphere (i.e. increasein the carbon pools). On the assumption that conifer and broadleafplanting could be represented by Sitka spruce and beech treesrespectively, litter and forest soil in Great Britain were accumulatingcarbon at 2.42 Mt a1 in 199596. Coniferous forestaccounted for 89 per cent of this uptake. Scottish conifer andbroadleaf forests took up 68 per cent and mapping the uptakeshowed that the greatest rate occurred in western Scotland.The pool of carbon in wood products increased in 199596by 0.31 Mt a1. The estimated uptake rates were sensitive to the relative amountsof conifer and broadleaf forest planted (particularly in relationto increases in the pool of carbon in wood products) but notto regional differences in Yield Class. Use of any single YieldClass in the range 1016 m3 ha1 a1 for allSitka spruce planting produced estimates of uptake rate in GreatBritain to trees, litter and soil within ±10 per centof that, assuming yield varied across the country. Lack of preciseknowledge on the parameters of the model was estimated to introducean uncertainty of ±3070 per cent into estimatesof carbon uptake. 相似文献
5.
The exchange of CH4 and CO2 over extensive tracts of peatlandhas recently been measured using micrometeorological methods.Fluxes of CH4 measured in Caithness (UK) during May and June1994 using eddy covariance yielded fluxes in the range 70to +170 µmol CH4 m2 h1 with a mean fluxof 39 µmol CH4 m2 h1 Landscape emissions of CH4 from peatland are shown to vary withwater table and temperature, increasing from 25 µmol CH4m2 h1 at 5 per cent area to 50 µmol CH4m2 h1 with 30 per cent within the footprint occupiedby pool. A positive temperature response of 4.9 µmol CH4m2 h1 {ring} C in the temperature range612{ring}C was also observed The mean day time fluxes of CO2 during May and June 1994, of3.6 mmol m2 h1 were two orders of magnitudelarger than the emission of CH4 of 40 µmol m2 h1,while at night (when net radiation is negative) the respirationflux of CO2 averaged +2.2 mmol m2 h1approximatelytwo orders of magnitude larger than night-time CH4 emissionsof 30 µmol m2 h1. 相似文献
6.
We have used the mass balance approach for calculating nitrogencritical loads (CL(N)) to avoid eutrophication for Sitka spruceplantation forestry in Wales. The various approaches for assigningvalues to the parameters in the mass balance equation are discussedwith particular reference to the soil nitrogen immobilizationvalue. A CL(N) value of 11 kgN ha1 a1 was calculatedfor an intensively studied site in Wales of Yield Class 14 ona freely draining acid soil. If this site is assumed to representa typical spruce stand, application of the CL(N) value meansthat 97 per cent of the area of coniferous forest in Wales,which is predominantly Sitka spruce, is currently receivingnitrogen deposition in excess of the CL(N). The area of coniferousforest at risk is reduced to 72 per cent if the proposed empiricalCL(N) for managed acidic coniferous forests to prevent ecologicalchanges (1020 kgN ha1 a1) is applied andto 45 per cent if the empirical CL(N) to prevent nitrogen saturation,nitrate leaching and depletion of soil base cations is applied(1025kgN ha1 a1). Irrespective of the choiceof CL(N) values, the implications of critical load exceedanceneed urgent investigation. Available information at presentindicates that the main known consequence of chronic atmosphericnitrogen deposition to coniferous forest ecosystems is enhancednitrate and associated aluminium leaching to freshwaters. Thereis insufficient information regarding the potential adverseeffects of eutrophication of soils and waters and of impactson tree health and production. 相似文献
7.
Denitrification of an Upland Forest Site 总被引:1,自引:0,他引:1
Rates of nitrogen loss through denitrification were monitoredfor standing forest and adjacent clear-felled areas locatedon a peaty-gley soil at Kershope Forest in the north of England,in two year-long studies. The rates of denitrification in soilcores brought back to the laboratory were determined using theacetylene (C2H2) block technique. An equation relating denitrificationto temperature was applied to derive an estimate for the monthlyloss of nitrogen via denitrification from the sites. In an additional study, half of the cores were incubated inthe absence of C2H2, so that an estimate of the ratio of emissionof N2O/N2 could be made. An annual loss of 13 kg N ha1 y1 was estimatedfor the standing forest while losses from the clearfelled siteswere estimated at 1040 kg N ha1 y1 duringthe first 2 years after felling. This loss returned to pre-fellinglevels 4 years after felling. The results are discussed in relation to other studies of denitrificationin forest soils and to the rates of N2O being lost to the atmosphereby UK forests. 相似文献
8.
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 ha1 a1 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 1.01.4 t C ha1 a1and were similar to, or lower than, levels in the undrainedsites. In the 39-year-old site average CO2 emissions were 2.6t C ha1 a1. In the clearfelled sites CO2 emissionswere lower at between 1.4 and 1.6 t C ha1 a1.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
9.
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
10.
The rate of accumulation of carbon in forests and woodlandsin Northern Ireland was estimated using the record of forestplanting since 1900 and a model that calculated the flow ofcarbon from the atmosphere to trees, litter, soil, wood productsand back to the atmosphere. It was assumed that all coniferforests had the carbon accumulation characteristics of Piceasitchensis, and upper and lower estimates of carbon storagewere calculated assuming Yield Class 16 m3ha1 a1unthinned and Yield Class 14 m3 ha1 a1 thinned.Broadleaved woodlands were assume to have the carbon accumulationcharacteristics of Fagus sylvatica, Yield Class 6 m3ha1a1. Northern Ireland currently has about 78 300 ha offorest, 83 per cent of which is coniferous, 77 per cent state-owned,mostly planted since 1945, with peak planting in 19601975.In 1990, conifer forests contained 34 MtC (trees + litter)and broadleaved wdlands contained about 0.8 MtC (trees + litter+ new forest soil). In 1990, conifer forests were sequestering0.150.20 MtC a1 and broadleaved woodlands about0.025 MtC a1. To maintain these sink sizes, new coniferforests need to be planted at 15002000 ha a1,and new broadleaved woodland at100150 ha a1 inaddition to full restocking. Current carbon sequestration byNorthern Ireland forests represents around 6.58.2 percent of the total for UK forests and is greater per hectar thanin Britain because the average forest age is younger in NorthernIreland 相似文献
11.
Rates of mineral nitrogen production and carbon dioxide evolutionin incubated samples from the upper 300mm of peat beneath lodgepolepine (Pinus contorta Dougl.) have been compared with those foradjacent unplanted areas at each of six sites in the North ofScotland. Under both aerobic (moist) and anaerobic (water logged)conditions, rates of mineral nitrogen production at 30°Care strongly influenced by peatland type, sampling depth andafforestation. During the early stages of the incubation underaerobic conditions, samples of planted peat showed a more rapidaccumulation of mineral nitrogen than did samples from unplantedareas, the amounts after 17 days being 170ppm and 46ppm mineralN, respectively; after 62 days however, the difference was nolonger significant. The mean rate of CO2 production averaged446µg CO2 g1 day1 in planted as against728µg in unplanted peat. Under anaerobic conditions, amountsof mineral nitrogen accumulated were similar in planted andunplanted sites but a difference in accumulation between the0150 and 150300mm horizons in unplanted peat wassignificantly reduced beneath the trees. 相似文献
12.
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
13.
Samples of LFH collected beneath the canopies of 16 coniferousspecies growing at the same site were incubated in the laboratorywith or without a starch amendment. Exchangeable nitrogen presentranged from 10.5256 and 11.4512 µgg1organic matter for freshly collected and unamended incubationsrespectively. When starch was added material from 11 speciesshowed significantly greater accumulation of mineral nitrogenwith increases ranging from ca 201370 per cent. Nitrificationwas negligible except in Thuja plicata where nitrate constituted68 or 83 per cent of the mineral nitrogen present after incubationwithout or with starch respectively. Starch addition increasedrates of net nitrogen mineralisation in LFH material from Piceasitchensis over a range of growth rates. Rates were greatestin material from the most productive stands whether or not starchwas added. The results are discussed with reference to the factorscontrolling litter decomposition and nitrogen mineralisationin the forest floor. 相似文献
14.
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 ha1 ranging from 4 to 411 mg ha1 (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 ha1, or a coefficient of variationof 92 per cent, that for evergreen forests was 24 mg ha1,or a coefficient of variation of 37 per cent. 相似文献
15.
Recent ideas on silage and fuelforestry call for more information on the total harvestablewoody dry matter produced by hardwoods grown at very close spacingsin fertile soils and coppiced every few years. Yields of oven-driedstems and branches (S and B) are presented here for Populustrichocarpa Torr. and Gray, clone Fritzi Pauley.Plantings in Bedfordshire at 21 600 trees ha1 had a meanannual increment (M.A.I.SB) of 5.2 t ha1 y1 overfive years, and plantings in the Cambridgeshire fens at 1480trees ha1 produced 4.8 t ha1 y1 over sixyears. Fan-shaped spacing experiments, established in Midlothianby inserting cuttings through black polythene into nursery soilwith added fertilizers, gave 4.6 t ha1 y1 at theend of the first year and about 7 t ha1 y1 oneyear after coppicing, but only with over 250 000 stems ha1producing closed canopies with leaf area indices of about 4.Similar spacing experiments planted without fertilizer on farmlandin Gloucestershire, Suffolk, Argyll and Midlothian gave averageM.A.I.SB values of 6.57.0 t ha1 y1 afterthree years with over 25 000 trees ha1 and similar valuesafter five years with over 10 000 trees ha1. Peak currentannual increments (C.A.I.SB) averaged 1012 t ha1y1. The maximum M.A.I.SB, attained in Gloucestershire,was 10.0 t ha1 y1 at age 5 with over 20 000 treesha1, with maximum C.A.I.SB values of about 14 t ha1y1 at age 4; M.A.I.SB values of about 11.5 t ha1y1 were anticipated at this site by age 68. Equivalentstem volumes are given. As expected, trees subjected to competitionaccumulated greater proportions of their woody biomass in stemsrather than branches. Biomass yields of fully-stocked young hardwood stands are independentof planting density. In Britain, M.A.I.SB values of 68t ha1 y1 can be obtained over 1 or 25 years byplanting 250 000 or 2000 trees ha1, using vigorous Populusspp, Salix spp or Nothofagus procera on good sites. Advantages and problems of silage forestry arediscussed, and it is considered that hardwood fuel coppicescould not meet more than about 2% of national energy needs. The reciprocals of individual tree weights were linearly relatedto planting density. 相似文献
16.
In an 11-year-old stand of Sitka spruce (Picea sitchensis [Bong.]Carr.) application of nitrogen fertilizers, at a rate of 10kgN ha1 month1, increased mean diameter incrementby 12 per cent, while the further addition of phosphorus, at5 kg ha1 month1, resulted in a 23 per cent increase.An attack by the green spruce aphid (Elatobium albietinum Walker)occurred during the period of fertilizer addition. The mostseverely affected trees showed a reduction in diameter growthof 50 to 56 per cent but the severity of the attack betweentrees was unrelated to the treatments applied. However, fertilizerapplication did hasten the recovery of diameter growth afterdefoliation. 相似文献
17.
Yang Yonghui; Watanabe Masataka; Li Fadong; Zhang Jiqun; Zhang Wanjun; Zhai Jianwen 《Forestry》2006,79(1):135-147
To estimate the possible effects of site factors and climatechange on forest growth in the Taihang Mountains, northern China,we assessed the factors influencing forest growth by using forestinventory data from 712 forest sample plots. Meteorologicaldata from 77 meteorological stations in the region were usedto estimate temperature and precipitation at each site fromelevation and longitude. Analyses showed that temperature, aspect,precipitation and soil thickness all significantly influencedforest growing stock (FGS), i.e. stem volume. When temperaturerose, FGS was reduced, possibly because increasing temperatureincreased evapotranspiration. Precipitation had a positive effecton FGS. The effect of aspect on FGS was perfectly expressedas a cosine function, with south-west- and south-facing slopeshaving the lowest FGS and north-facing slopes having the highest.We developed multifactorial regression models to predict changesin FGS in the Taihang Mountains. Temperature, forest age, forestcover, soil thickness, precipitation and aspect were well relatedto FGS. The effects of a temperature decrease and a precipitationincrease on FGS would be 2.58 per cent per degree centigradeand 10 per cent per 100 mm, respectively. The combination oftemperature increase and precipitation changes under futureclimate change is likely to result in a decrease of FGS, thoughthis does not take account the effect of increasing CO2. Wealso used multifactorial regression models to analyse the effectsof site factors on FGS of Pinus tabulaeformis Carr. and Robiniapseudoacacia L., two major species used in afforestation inthe Taihang Mountains. Although site factors had similar effectson FGS, diameter at breast height and tree height of both species,prediction accuracy (regression coefficient) was improved greatlywhen we treated the species separately. 相似文献
18.
Forest inventory data (FID) include forest resources informationat large spatial scale and long temporal scale. They are importantdata sources for estimating forest net primary productivity(NPP) and carbon budget at landscape and regional scales. Inthis study, more than 100 datasets of biomass, volume, NPP andstand age for Chinese pine forests (Pinus tabulaeformis) fromthe literature were synthesized to develop regression equationsbetween biomass and volume, and between NPP and biomass as wellas stand age. Using these regression equations and the fourthFID surveyed by the Forestry Ministry China from 1989 to 1993,NPP values of Chinese pine forests were estimated. The meanNPP of Chinese pine forests was 4.35 Mg ha1 yr1.NPP varied widely among provinces, ranging from 1.5 (Neimenggu)to 13.73 Mg ha1 yr1 (Guizhou). Total NPP of Chinesepine was 10.87 Tg yr1 (1 Tg = 1012 g). NPP values ofChinese pine forests were not distributed evenly across differentprovinces in China. This study may be useful not only for estimatingforest carbon of other forest types but also for evaluatingterrestrial carbon balance at regional and global levels. 相似文献
19.
CANNELL M. G. R.; TABBUSH P. M.; DEANS J. D.; HOLLINGSWORTH M. K.; SHEPPARD L. J.; PHILIPSON J. J.; MURRAY M. B. 《Forestry》1990,63(1):9-27
Seedlings (transplants) of 2+1 Sitka spruce (Picea sitchensis(Bong.) Carr.) and 1 + 1 Douglas fir (Pseudotsuga menziesii(Mirb.) Franco) were grown in a nursery at the Bush Estate,Scotland. Batches were lifted and cold stored at 0.5°C inNovember, December and January. Changes in growth, shoot apicalmitotic index, root growth potential (RGP), carbohydrate content,bud dormancy and shoot frost hardiness were monitored throughoutthe winter by taking samples at intervals from the nursery andfrom cold storage. Frost hardening occurred during the later stages of bud development(as mitotic indices decreased); autumn hardening was arrestedwhen seedlings were put in cold store, and some dehardeningoccurred in cold storage, especially in spring. Bud dormancystarted, and was greatest, just after bud growth (mitotic activity)virtually ceased; chilling in cold store was almost as effectivein releasing dormancy as natural chilling. The concentrationof total nonstructural carbohydrates stayed more or less constantat 100150mg g1 from September to April in thenursery; in cold storage carbohydrates were depleted at 0.40.6mgg1 d1 (corresponding to respiration at 0.030.05mgCO2 g1 h1) until there was only 4050mgg1. Root growth potentials in the nursery increased in December,once the buds ceased growth, became dormant and had receivedsome chilling. Sitka spruce was storable in November,before RGPs increased, but they then failed to achieve maximalfrost hardiness or ROP. Winter RGPs were high in Sitka spruceand were increased or maintained in cold storage, whereas RGPswere low in Douglas fir and decreased immediately after storage(except when stored in January). By the end of April, the RGPof cold stored Sitka spruce was much higher than that of directlifted plants. ROP changes in the nursery and in cold storagewere not consistently related to changes in seedling carbohydratecontents, shoot frost hardiness or bud dormancy. In practical terms, it was concluded that (1) the optimum dateto start lifting bare- rooted conifer transplants in the autumnis when their shoot apical mitotic indices have decreased tonear zero, and their RGPs have risen sharply; (2) high RGPsmay depend as much on the morphology of the roots (e.g. numberof undamaged root apices) as on the physiology of the shoots(e.g. carbohydrate status, dormancy and frost hardiness); and(3) in spring, transplants kept in cold storage since November,December or January are more frost hardy, slightly more dormant,and (in May) have higher RGPs than transplants lifted from thenursery. 相似文献
20.
Samples of litter and humus from beneath 10 m tall, closed-canopySitka spruce planted on a brown forest soil were incubated underboth field and laboratory conditions to measure mineral nitrogenproduction and carbon dioxide evolution. Mineral nitrogen productionin enclosed samples over 12 months was equivalent to 50 and17 kg N ha1 in litter and humus, respectively. Applicationsof fertilizer NPK (200 kg N ha1 as ammonium nitrate,100 kg P ha1 as unground rock phosphate and 150 kg Kha1 as potassium chloride), 18 months previously, decreasedthese values slightly, but stimulated the production of nitratein both litter and humus. Compared with samples kept under laboratoryconditions at 10°C, those incubated in the field at a similarmean temperature released less carbon dioxide and, in the caseof fertilized humus produced smaller amounts of mineral nitrogen. 相似文献