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 carbon sink provided by plantation forests and their products in Britain

The rate of accumulation of carbon in forest plantations inBritain is estimated using the record of forest planting since1925 and a model that calculates the flow of carbon from theatmosphere to trees, litter, soil, wood products and back tothe atmosphere. It is assumed that all trees planted so farhave the carbon accumulation characteristics of P. sitchensis,Yield Class 14 m³ ha^-1 a^-1, but that future planting could includeF. sylvatica Yield Class 6 and Populus Yield Class 12. It isfurther assumed that conifer plantings increase surface litter,but not soil organic matter, whereas broadleaved tree plantings(on mineral soils) increase both. Because the current forest estate is relatively young, it isestimated to be accumulating about 2.5 million tonnes of carbonper year (1990), and to be still increasing in carbon density(tonnes C ha^-1). In order to maintain this rate of carbon removalfrom the atmosphere, planting would need to continue at a rateof 25–30 thousand ha of conifers or (theoretically) 10thousand ha of poplars per year (on good mineral soils). Itis noted that 2.5 million tonnes C is about 1.5 percent of theUK carbon emission, and may be similar to the natural carbonsink in Britain represented by wetlands and rivers.     

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.     

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.     

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.     

The effect of afforestation on soil carbon dioxide emissions in blanket peatland in Ireland

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.     

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.     

UK conifer forests may be growing faster in response to increased N deposition, atmospheric CO2 and temperature

Site studies have shown that conifer plantations in northernBritain have increased in General Yield Class (GYC) by 1 m³ha^–1 a^–1 per decade or more (20–40 per cent)since the 1930s. Large increases in forest productivity havealso occurred in many other regions of Europe. Are these increasesdue to improved silvicultural practices or to increases in Ndeposition, CO₂ and temperature? Two process-based mathematicalmodels of forest growth were used to simulate the responsesof conifer forests growing in the Scottish southern uplandsto increases in atmospheric N deposition, CO₂ concentrationand temperature, during this century and next century. The modelsdiffered substantially in the ways in which underlying processeswere represented: one simulated a managed plantation, the othera natural forest. Nevertheless, both showed that: (1) increasesin N deposition, CO₂ and temperature together might accountfor up to half of the observed increase in GYC this century;(2) increased N deposition and CO₂, considered separately, probablyincreased forest productivity by a modest amount (7–14per cent), but their combined effect has been approximatelyadditive; (3) increased temperature, even when combined withincreasing CO₂ concentrations, promoted growth less than expectedfrom site studies relating GYC to temperature; and (4) substantialfurther increases in productivity, GYC, leaf area index andstanding biomass are forecast during the next century as a resultof increasing CO₂ concentrations and continued N deposition,with or without climatic warming. The predicted increases inGYC could be large enough to have profound effects on the forestindustry.     

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.     

Denitrification of an Upland Forest Site

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 1–3 kg N ha^–1 y^–1 was estimatedfor the standing forest while losses from the clearfelled siteswere estimated at 10–40 kg N ha^–1 y^–1 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.     

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.     

Litter Production in Western Washington Douglas-Fir Stands

Litter production by Douglas-fir stands ranging in age from22 years old to 160 years old, is discussed. Typical leaf litterproduction was 2100 kg ha^–1 yr^–1 while total litterwas 2500 kg ha^–1 yr^–1. Annual fall of leaf litterincreases up to about 40 years of age and then becomes fairlyconstant while total litter continues to increase because ofwood production, although this increase may be quite irregular.Average nutrient returns to the forest floor are 21, 3, 7, 32,4, and 7 kg ha^–1 yr^–1 for N, P, K, Ca, Mg, and Mnrespectively.     

Above-Ground Biomass of Mountain Beech (Nothofagus solandri (Hook.f.) Oerst. var. cliffortioides (Hook.f.) Poole) in Different Stand Types Near Timberline in New Zealand

In the alpine timberline ecotone at 1350 m in the CraigieburnRange, New Zealand, four distinct mountain beech stand types(a pole, a coppice, a high forest and a shrublike stand) wereanalysed for stand biomass and leaf area by means of allomet-ricregressions based on stem diameter. Differences between stand types in terms of age, structure,biomass and leaf area are interpreted as development stagesafter stand breakdowns due to external impacts. Vegetative reproduction,mainly coppicing, plays an important part in stand regeneration. The young pole stand had 177 t ha^–1, the coppice stand272 t ha^–1, and the mature high forest stand 323 t ha^–1aboveground dry weight. A low mountain beech shrub stand withgnarled, windshaped dwarf trees had only 135 t ha^–1. Foliageaccounted for only 3–5% in all stands, the leaf area indexwas also low, at 3.0 in the shrub stand and 3.7–7.4 inthe forest stands. The low foliage proportion is consideredto be a response to the harsh environment.     

High Productivity in a Polestage Sitka Spruce Stand and its Relation to Canopy Structure

1. The net annual above ground dry matter production of a 17 yearplantation of Sitka spruce in Scotland was 26.7 t ha^–1y^–1.Total annual production which includes estimates for roots,was 35 t ha^–1y^–1, one of the highest values reportedfor coniferous forest in the temperate zone.
2. When comparedwith other forests with high rates of net productionthis standhad the highest foliage and branch biomass and lowestrate ofproduction per unit of foliage.
3. Gross foliage increment tothe canopy declined following thetime of maximum stand basalarea increment, which coincidedwith the onset of competitionbetween individual trees. Thesechanges in canopy and standstructure are discussed in relationto the decline in net productionwhich has been observed inpolestage conifer plantations.
4. Foliageand branch production were greatest in the top 6 whorlsof thecanopy; over the period studied new foliage became concentratednearer to the top of the trees. Significant branch wood incrementceased below the height where needle death balances needle production.
5. New needles produced at increasing depth in a canopy weighedless per unit needle area. Generally needles lost weight asthey aged. All needles survived for three years, the greatestmortality was of 5-year-old needles but some survived for 8years.
6. Needle area index was 10–11 at age 16, 7–8at age18. Branch area index was 3.6 and the ratio of main stembarksurface area to ground area was 0.4 at age 16.

     

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.     

孟加拉吉大港地区丘陵森林有机物积累

在孟加拉吉大港丘陵地区,调查了热带季风气候条件下的3种人工林(7年生大叶相思(Acacia auriculiformis)林、15年生大叶相思林和18年生混交林)和1种天然林的森林凋落物及其对土壤性质的作用.结果表明,总的有机质积累随人工林树龄增加而增加,但是年积累量随之降低.在同一植被类型内,不同坡位新鲜或部分分解的凋落物有机质累计量变化较大,坡底部有机质积累量最高,沿着山坡向上逐渐减少.在15年生大叶相思人工林内,土壤整合有机物积累量变化趋势与新鲜或部分分解有机质积累量变化趋势相反.在7年生和15年生的大叶相思林以及18年龄的阔叶混交人工林内,新鲜、部分分解和完全分解(含土壤整合有机质)有机质总生产速率分别是2554.31、705.79和1028.01kg.ha-1·a-1,新鲜凋落物有机质在3种林分中的生产速率分别是38.23,19.40和30.48 kg·ha-1·a-1.3种人工林和自然林内,平均新鲜凋落物的有机质积累占有机质产出总量的32.45%,部分分解凋落物占13.50%,而全分解整合土壤有机质占54.56%.森林土壤酸度随凋落物分解阶段的深入而增加.     

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.     

Carbon and nitrogen storage in agroforests, tree plantations, and pastures in western Oregon, USA

Pastures store over 90% of their carbon and nitrogen below-ground as soil organic matter. In contrast, temperate conifer forests often store large amounts of organic matter above-ground in woody plant tissue and fibrous litter. Silvopastures, which combine managed pastures with forest trees, should accrete more carbon and nitrogen than pastures or timber plantations because they may produce more total annual biomass and have both forest and grassland nutrient cycling patterns active. This hypothesis was investigated by conducting carbon and nitrogen inventories on three replications of 11 year-old Douglas-fir (Pseudotsuga menziesii)/perennial ryegrass (Lolium perenne)/subclover (Trifolium subterraneum) agroforests, ryegrasss/subclover pastures, and Douglas-fir timber plantations near Corvallis, Oregon in August 2000. Over the 11 years since planting, agroforests accumulated approximately 740 kg ha^–1 year ^–1 more C than forests and 520 kg ha^–1 year^–1 more C than pastures. Agroforests stored approximately 12% of C and 2% of N aboveground compared to 9% of C and 1% of N above ground in plantations and less than 1% of N and C aboveground in pastures. Total N content of agroforests and pastures, both of which included a nitrogen-fixing legume, were approximately 530 and 1200 kg ha^–1 greater than plantations, respectively. These results support the proposition that agroforests, such as silvopastures, may be more efficient at accreting C than plantations or pasture monocultures. However, pastures may accrete more N than agroforests or plantations. This apparent separation of response in obviously interrelated agroecosystem processes, points out the difficulty in using forest plantation or pasture research results to predict outcomes for mixed systems such as agroforests. This revised version was published online in June 2006 with corrections to the Cover Date.     

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.     

Nutrient Leaching from the Litter Layer after Clearfelling of Sitka Spruce Stands on Peaty Gley Soils

The nutrient dynamics in the litter layer of former Sitka sprucestands were examined from 0 to 7 years after clearfelling usingzero-tension lysimeters on a time series of sites 0, 2 and 5years after felling. The loss of most nutrients monitored inleachate was independent of the time from clearfelling. However,54 per cent (43 kg ha^–1) of the 7-year net loss of potassiumwas leached out of the litter layer in the first year. Also,nitrate losses, although small, increased after 5 years. Leachinglosses of NH₄-N, PO₄-P, K, Ca and H⁺ exceeded precipitationinputs. However, leaching losses were less than precipitationinputs for NO₃-N, Na and Mg. Nutrient losses from under brashswathes were generally greater than from clear strips.