Carbon storage and sequestration in the forests of Northern Ireland

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 m³ha^–1 a^–1unthinned and Yield Class 14 m³ ha^–1 a^–1 thinned.Broadleaved woodlands were assume to have the carbon accumulationcharacteristics of Fagus sylvatica, Yield Class 6 m³ha^–1a^–1. 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 1960–1975.In 1990, conifer forests contained 3–4 MtC (trees + litter)and broadleaved wdlands contained about 0.8 MtC (trees + litter+ new forest soil). In 1990, conifer forests were sequestering0.15–0.20 MtC a^–1 and broadleaved woodlands about0.025 MtC a^–1. To maintain these sink sizes, new coniferforests need to be planted at 1500–2000 ha a^–1,and new broadleaved woodland at100–150 ha a^–1 inaddition to full restocking. Current carbon sequestration byNorthern Ireland forests represents around 6.5–8.2 percent of the total for UK forests and is greater per hectar thanin Britain because the average forest age is younger in NorthernIreland     

The effect of geographical variation of planting rate on the uptake of carbon by new forests of Great Britain

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 a^–1 in 1995–96. 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 1995–96by 0.31 Mt a_–1. 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 10–16 m³ ha^–1 a^–1 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 ±30–70 per cent into estimatesof carbon uptake.     

The Amount and Nutrient Content of Litter Fall under Sitka Spruce on Poorly Drained Soils

Litter fall was collected every three months for four yearsfrom twenty-one vigorous (Yield Class 18–20 m³ ha^–1y^–1) and sixteen less vigorous (Yield Class 10–12)plots of Sitka spruce on gleyed soils in Northern Ireland. Forty-fourper cent of all litter fell in the June-August quarter, andlitter fall was heaviest in years when there was green spruceaphis attack. Beneath YC 10–12 crops, both rate and quantityof litter fall was less and nutrient concentrations were lower,than under YC 18–20 crops. As the pool of organic matterand nutrients on the forest floor was greater under trees ofYC 10–12, poor growth was associated with a slow organicmatter and nutrient turnover.     

Carbon pools and sequestration in forest ecosystems in Britain

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.     

Conifer Plantations on Drained Peatlands in Britain: a Net Gain or Loss of Carbon?

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 m^–2 forPicea sitchensis, Yield Class 12. Deep and shallow peats inthe British uplands contain about 0.47 and 0.80 kg C m^–2per centimetre depth, respectively. Thus, the 16.7 kg C m^–2that 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 50–100 g C m^–2a^–1 there is likely to be increased carbon storage inthe whole system for at least three rotations; but if CO₂ lossrates are 200–300 g C m ^–2 a^–1 increased storagemay be restricted to the first rotation, after which there isa net loss of carbon.     

Carbon stocks and sequestration in plantation forests in the Republic of Ireland

The United Nations Framework Convention on Climate Change andits Kyoto Protocol (KP) have created a clear need for methodsthat enable accurate accounting of carbon (C) stocks and stockchanges in forest ecosystems. The rate of accumulation of Cin plantation forests in the Republic of Ireland was estimatedfor the period 1906–2002 using the record of afforestationand a dynamic C accounting model (C-flow). Projections for theperiod 2003–2012 were made using different afforestationrates. It was assumed that Sitka spruce planted in the period1906–1989 was Yield Class (YC) 16 m³ ha^–1 year^–1and that after 1990 this increased to 20 m³ ha^–1 year^–1.All other conifers were assumed to have the growth characteristicsof YC 8 m³ ha^–1 year^–1 lodgepole pine. Broadleaveswere assumed to have the growth characteristics of YC 6 m³ ha^–1year^–1 beech. In 2002, the total forest C stock was 37.7Mt C representing an increase of 14.8 Mt C since 1990. In 2002,the rate of increase in trees, products, litter and soil was0.7, 0.1, 0.1 and 0.5 Mt C, respectively. Under a business-as-usualscenario, afforestation since 1990 is estimated to create anannual average C sink of 0.9 Mt C year^–1 during the period2008–2012. This accounts for 22 per cent of Ireland'sreduction commitment under the KP. Afforestation on peat soilswas found to reduce the net C sink, although the extent to whichit does so is highly dependent on assumptions regarding therate of peat C loss.     

Sweet chestnut: silviculture, timber quality and yield in the Forest of Dean

The silviculture, performance and value of sweet chestnut (Castaneasativa Miller) are reviewed in the light of experience in theForest of Dean in Gloucestershire. The many advantages of includingthe species within broadleaved woodland include its ease ofestablishment, fast growth rate, and the high value of its timber.Veneer and first quality planking material fetch premium prices.That it is not more widely planted is mainly due to the widelyheld view that it is difficult or impossible to grow chestnutlogs that are not shaken. Shake is shown to be mainly a problemof overmature trees. Ink disease (Phytophthora sp.) is not regardedas a major limitation, especially in new plantings. Guidanceis given on the conversion of chestnut coppice to high forest.Yield tables are presented which may be applied to chestnuthigh forest of coppice origin in the Forest of Dean, and withcaution elsewhere in southern England. The data for the bettersites in the Forest of Dean indicate possible yields of up to11 m³ ha^–1 a^–1, and a dominant diameter incrementof up to 1 cm a^–1.     

Productivity of Closely-spaced Young Poplar on Agricultural Soils in Britain

Recent ideas on ‘silage’ and ‘fuel’forestry 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 ha^–1 had a meanannual increment (M.A.I._SB) of 5.2 t ha^–1 y^–1 overfive years, and plantings in the Cambridgeshire fens at 1480trees ha^–1 produced 4.8 t ha^–1 y^–1 over sixyears. Fan-shaped spacing experiments, established in Midlothianby inserting cuttings through black polythene into nursery soilwith added fertilizers, gave 4.6 t ha^–1 y^–1 at theend of the first year and about 7 t ha^–1 y^–1 oneyear after coppicing, but only with over 250 000 stems ha^–1producing 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 6.5–7.0 t ha^–1 y^–1 afterthree years with over 25 000 trees ha^–1 and similar valuesafter five years with over 10 000 trees ha^–1. Peak currentannual increments (C.A.I._SB) averaged 10–12 t ha^–1y^–1. The maximum M.A.I._SB, attained in Gloucestershire,was 10.0 t ha^–1 y^–1 at age 5 with over 20 000 treesha^–1, with maximum C.A.I._SB values of about 14 t ha^–1y^–1 at age 4; M.A.I._SB values of about 11.5 t ha^–1y^–1 were anticipated at this site by age 6–8. 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 6–8t ha^–1 y^–1 can be obtained over 1 or 25 years byplanting 250 000 or 2000 trees ha^–1, 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.     

Nitrogen Transformations and Decomposition in Litter and Humus from beneath Closed-Canopy Sitka Spruce

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 ha^–1 in litter and humus, respectively. Applicationsof fertilizer NPK (200 kg N ha^–1 as ammonium nitrate,100 kg P ha^–1 as unground rock phosphate and 150 kg Kha^–1 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.     

Nitrogen critical loads for spruce plantations in Wales: is there too much nitrogen?

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 ha^–1 a^–1 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 (10–20 kgN ha^–1 a^–1) 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(10^–25kgN ha^–1 a^–1). 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.     

Biomass production and allometric above- and below-ground relations for young birch stands planted at four spacings on abandoned farmland

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.     

Carbon sequestration in the trees, products and soils of forest plantations: an analysis using UK examples

A carbon-flow model for managed forest plantations was used to estimate carbon storage in UK plantations differing in Yield Class (growth rate), thinning regime and species characteristics. Time-averaged, total carbon storage (at equilibrium) was generally in the range 40-80 Mg C ha(-1) in trees, 15-25 Mg C ha(-1) in above- and belowground litter, 70-90 Mg C ha(-1) in soil organic matter and 20-40 Mg C ha(-1) in wood products (assuming product lifetime equalled rotation length). The rate of carbon storage during the first rotation in most plantations was in the range 2-5 Mg C ha(-1) year(-1).A sensitivity analysis revealed the following processes to be both uncertain and critical: the fraction of total woody biomass in branches and roots; litter and soil organic matter decomposition rates; and rates of fine root turnover. Other variables, including the time to canopy closure and the possibility of accelerated decomposition after harvest, were less critical. The lifetime of wood products was not critical to total carbon storage because wood products formed only a modest fraction of the total.The average increase in total carbon storage in the tree-soil-product system per unit increase in Yield Class (m(3) ha(-1) year(-1)) for unthinned Picea sitchensis (Bong.) Carr. plantations was 5.6 Mg C ha(-1). Increasing the Yield Class from 6 to 24 m(3) ha(-1) year(-1) increased the rate of carbon storage in the first rotation from 2.5 to 5.6 Mg C ha(-1) year(-1) in unthinned plantations. Thinning reduced total carbon storage in P. sitchensis plantations by about 15%, and is likely to reduce carbon storage in all plantation types.If the objective is to store carbon rapidly in the short term and achieve high carbon storage in the long term, Populus plantations growing on fertile land (2.7 m spacing, 26-year rotations, Yield Class 12) were the best option examined. If the objective is to achieve high carbon storage in the medium term (50 years) without regard to the initial rate of storage, then plantations of conifers of any species with above-average Yield Classes would suffice. In the long term (100 years), broadleaved plantations of oak and beech store as much carbon as conifer plantations. Mini-rotations (10 years) do not achieve a high carbon storage.     

Carbon storage in forest soils

The amounts of carbon stored in soils and vegetation in Britain,and the potential of forestry to influence, whether soils actas sinks or sources, are discussed. Soils are estimated to containc.22 x 10⁹ t carbon, while the amount in vegetation includingforests is only 115 x 10⁶ t. Some 86 per cent of the soil carbonis present in peats and peaty-surfaced soils, mainly in north-westBritain. Soil carbon content is strongly related to climateand altitude. Conversion of lowland cultivated land to forestcan result in carbon accumulation in soils, as it can followingthe planting of some uplands, but quantities appear to be smallin relation to the amounts carbon released to the atmospherethrough fossil fuel use. Forest felling may result in decreasesin soil carbon store, due to soil disturbance and changes inmicroclimatic conditions, but several decades after reafforestationthe carbon store may recover to near original levels. Shorteningforest rotations may result in long-term declines in soil carbonstore. The main concern is the potential for forestry to convertpeats, which contain amounts of carbon equivalent to 100 years'fossil fuel use at 1988 levels and which are normally slow sinksfor atmospheric carbon, into carbon sources returning it tothe atmosphere. The possible impacts of forestry and globalwarming on rates of carbon loss from upland soils includingpeats are discussed.     

Mechanized Direct-Seeding of Native Forests in Xingu,Central Brazil

The Y Ikatu Xingu Campaign brought together indigenous people, farmers, researchers, governmental, and non-governmental organizations seeking riparian forest restoration in the Xingu watershed, in west-central Brazil. Forest restoration is challenging in the region because of scarce nurseries, long distances, and high costs associated with the usual technique of planting nursery-raised seedlings. This article describes mechanized direct seeding and compares it with the planting of seedlings, in terms of cost and tree densities at ages of 0.5 until 5.5 yr after planting. Direct-seeding was mechanized using common agricultural machines designed for sowing cereals or grasses, which were loaded with 200,000 seeds of native trees and 150,000 seeds of annual and sub-perennial legumes, plus 50–150 kg sand ha^?1. The Campaign restored more than 900 ha by direct-seeding and 300 ha by planting seedlings. The great demand for native seeds was met by the Xingu Seed Network, formed by Indians, small landholders, and peasants, which commercialized 98 tons of native seeds and earned US$500,000 since 2006. Direct-seeding costs less per hectare than planting seedlings (US$1,845 ha^?1 against US$5,106 ha^?1), results in higher tree densities (2,500–32,250 trees ha^?1 against 1,500–1,650 trees ha^?1), is more practical, and creates layers of dense vegetation that better resembles natural forest succession.     

Estimating net primary productivity of Chinese pine forests based on forest inventory data

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 ha^–1 yr^–1.NPP varied widely among provinces, ranging from 1.5 (Neimenggu)to 13.73 Mg ha^–1 yr^–1 (Guizhou). Total NPP of Chinesepine was 10.87 Tg yr^–1 (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.     

Stocks and dynamics of soil organic carbon and coarse woody debris in three managed and unmanaged temperate forests

The effect of forest conservation on the organic carbon (C) stock of temperate forest soils is hardly investigated. Coarse woody debris (CWD) represents an important C reservoir in unmanaged forests and potential source of C input to soils. Here, we compared aboveground CWD and soil C stocks at the stand level of three unmanaged and three adjacent managed forests in different geological and climatic regions of Bavaria, Germany. CWD accumulated over 40–100 years and yielded C stocks of 11 Mg C ha^?1 in the unmanaged spruce forest and 23 and 30 Mg C ha^?1 in the two unmanaged beech–oak forests. C stocks of the organic layer were smaller in the beech–oak forests (8 and 19 Mg C ha^?1) and greater in the spruce forest (36 Mg C ha^?1) than the C stock of CWD. Elevated aboveground CWD stocks did not coincide with greater C stocks in the organic layers and the mineral soils of the unmanaged forests. However, radiocarbon signatures of the O _e and O _a horizons differed among unmanaged and managed beech–oak forests. We attributed these differences to partly faster turnover of organic C, stimulated by greater CWD input in the unmanaged forest. Alternatively, the slower turnover of organic C in the managed forests resulted from lower litter quality following thinning or different tree species composition. Radiocarbon signatures of water-extractable dissolved organic carbon (DOC) from the top mineral soils point to CWD as potent DOC source. Our results suggest that 40–100 years of forest protection is too short to generate significant changes in C stocks and radiocarbon signatures of forest soils at the stand level.     

The tolerance of young trees to applications of clopyralid alone and in mixture with foliar-acting herbicides

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.     

Productivity of Sitka Spruce in Northern Britain 2. Prediction from Site Factors

Productivity and site data from 187 temporary sample plots wereanalysed by multiple regression analysis to derive models inwhich site variables accounted for 78–86 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 ha^–1y^–1 and the mean error for predicting GYC for a forestblock (acquisition) was calculated to be ±1 m³ ha^–1y^–1 These figures were confirmed by the results of a validationsurvey and the application to field prediction of productivityis described.     

Litter production, seasonal pattern and nutrient return in seven natural forests compared with a plantation in southern China

The amount and pattern of litterfall and its nutrient returnwere studied in seven natural forests of Schima superba Gardn.and Champ. (SCS), Castanopsis fabri Hance (CAF), Tsoongiodendronodorum Chun (TSO), Cinnamomum chekiangense Nakai (CIC), Altingiagracilipes Hemsl. (ALG), Castanopsis carlesii (Hemsl.) Hayata(CAC) and Pinus massoniana D. Don (PIM), and compared with thatof an adjacent 29-year-old plantation of Chinese fir (Cunninghamialanceolata Lamb.) (CUL) in Jianou, Fujian, China. Mean annualtotal litterfall over 3 years of observations varied from 4.63Mg ha^–1 in the CUL to 8.85 Mg ha^–1 in the PIM; ofthis litterfall, the leaf contribution ranged from 62 to 73per cent. Litterfall in the CAF, ALG and CAC showed an unimodaldistribution pattern, while for the five other forests, thelitterfall pattern was multi-peak. The rank order of the eightforests, according to nutrient return mass with the exceptionof P, was different from the order when rank was according tototal mass of litterfall. The highest annual N, K and Ca returnsfrom total litterfall were noticed in the TSO, the CAF and theCUL, respectively. The amounts of P and Mg potentially returnedto the soil were the highest in the PIM. The leaf fraction providedgreater potential returns of N, P, K, Ca and Mg to the soilthan other litter fractions. The results of this study demonstratethat natural forests have a greater capability for maintainingsite productivity than the monoculture coniferous plantation,due to higher amount of above-ground litter coupled with greaternutrient returns; therefore conservation of natural forestsis recommended as a practical measure in forest management torealize sustainable development of forestry in mountainous areasof southern China.     

How much carbon can the Siberian boreal taiga store: a case study of partitioning among the above-ground and soil pools

In the context of global carbon cycle management, accurate knowledge of carbon content in forests is a relevant issue in contemporary forest ecology. We measured the above-ground and soil carbon pools in the darkconiferous boreal taiga. We compared measured carbon pools to those calculated from the forest inventory records containing volume stock and species composition data. The inventory data heavily underestimated the pools in the study area(Stolby State Nature Reserve, central Krasnoyarsk Territory, Russian Federation). The carbon pool estimated from the forest inventory data varied from 25(t ha-1)(low-density stands) to 73(t ha-1)(highly stocked stands). Our estimates ranged from 59(t ha-1)(lowdensity stands) to 147(t ha-1)(highly stocked stands). Our values included living trees, standing deadwood, living cover, brushwood and litter. We found that the proportion of biomass carbon(living trees): soil carbon varied from99:1 to 8:2 for fully stocked and low-density forest stands,respectively. This contradicts the common understanding that the biomass in the boreal forests represents only16–20 % of the total carbon pool, with the balance being the soil carbon pool.