Deposition patterns in bulk precipitation and throughfall in a subtropical mixed forest in central-south China

The chemistry and deposition pattern in bulk precipitation andthroughfall (TF) were examined and evaluated based on the 3-yearobservations in Shaoshan subtropical deciduous-conifer mixedforest in central-south China. The TF chemistry was notablychanged when passing through canopies, which probably was attributedto the dry deposition (DD) on leaf surface and the canopy exchanges.Base cations' (Ca²⁺, Mg²⁺ and K⁺) fluxes were significantlyenriched in TF, in particular for K⁺. The annual K⁺ canopy exchangewas 12 times larger than DD, and canopy exchange of Ca²⁺, Mg²⁺and K⁺ was four times as high as the DD. The canopy exchangeof base cations in association with weak acid accounted for28.4 per cent of total leached base cations, which was one ofthe important factors to modify the TF chemistry.     

Changes to blanket bog adjoining forest plots at Bad a' Cheo, Rumster Forest, Caithness

Some impacts of 28-year-old South Coastal lodgepole pine foreston adjacent open blanket bog were investigated. A general risein ground level in unplanted areas between 1966 and 1987 hadbeen cancelled out by subsidence over most of the area by 1996.The forest plots had subsided by 40–80 cm since planting,depending on the cultivation/drainage treatment used and hadan increased peat dry bulk density (0.13 Mg m^–3) and adecreased water content (7 kg kg^–1 dry matter) comparedwith points more than 50 m from the forest (0.060–11 Mgm^–3 and 9–16 kg kg^–1 dry matter). The depthto water table in July averaged 55 cm in the forest but only20 cm outside. The zone outside the forest affected by subsidence averaged30 m wide in 1996, compared with 10–20 m in 1987, suggestingthat by the end of the first rotation a 40-m wide zone willbe affected. The development of a slope outside the forest bysubsidence was considered to be a consequence of more rapidrun-off and seepage towards the forest, rather than root spreadonto the bog. Where pool systems or other vulnerable habitatsare surrounded by forest, a buffer zone at least 40 m wide isneeded between the edge of the habitat and the edge of the forestto safeguard the habitat during the first rotation. A narrowerbuffer zone may be sufficient in higher rainfall areas.     

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.     

Deposition pattern of precipitation and throughfall in a subtropical evergreen forest in south-central China

The effects of dry deposition, canopy leaching, precipitation ion concentration, and precipitation H⁺ concentration on net throughfall flux (NTF, throughfall minus bulk precipitation) were evaluated on a seasonal basis by using a multiple regression analysis approach based on an observation period of 4 years in Shaoshan subtropical mixed evergreen forest, south-central China. Regression analysis results indicated that the estimated canopy exchange flux was the dominant factor regulating the NTF and the calculated dry deposition was a minor term. The seasonal dry deposition of base cations accounted for 15%–43% of the NTF. The NTF analysis showed that K⁺, Ca²⁺, Mg²⁺, Na⁺, and weak acids in throughfall were derived from foliar leaching and the canopy uptakes of H⁺, NH₄ ⁺, and NO₃ ⁻ were from precipitation. The retention rate of proton (H⁺ and NH₄ ⁺) in the canopy was close to the canopy leaching rate of base cations when corrected for weak acids because weak acid-induced canopy leaching did not exchange with protons, which suggested that the canopy leaching processes neutralized acid precipitation in Shaoshan forest.     

Some Effects of Afforestation with Lodgepole Pine on Rates of Nitrogen Mineralization in Peat

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 g^–1 day^–1 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 the0–150 and 150–300mm horizons in unplanted peat wassignificantly reduced beneath the trees.     

Relationships between local stand density and local species composition and nutrient content in the topsoil of pure and mixed stands of silver fir (Abies alba Mill.)

This study examined topsoil samples from the humic mineral horizon in four pure silver fir (Abies alba Mill.) and five mixed stands with beech (Fagus sylvatica L.), spruce (Picea abies L.; Karst.) and pine (Pinus sylvestris L.). In every stand, 60–70 sampling locations were chosen using a stratified random scheme that represented a gradient in local stand density and local species composition. One working hypothesis was that stand density and species composition affect the content of nutrients in the mineral humic soil horizon. Specifically, the analysis statistically tested for relationships between general and species-specific local stand density measures (basal area, sum of tree diameters weighted by distance, canopy openness) and the contents of total C, total N (in four stands), base cations (Ca²⁺, Mg²⁺, K⁺, Na⁺) and Mn²⁺ (in nine stands). A considerable variation in nutrient concentrations was observed; the coefficients of variation ranged from 0.21 to 0.38 for N, from 0.20 to 0.94 for the sum of base cations and from 0.56 to 0.95 for Mn. However, no clear relationship emerged between local stand density and the concentration of N and base cations; in five stands, manganese showed a negative correlation with local stand density. In the mixed fir-beech stand, significantly higher concentrations of Ca, K and Mn were found in the vicinity of beeches, and species-specific stand density explained up to 15, 29 and 34% of total variation in the content of these elements, respectively. Similar tendencies also appeared in the mixed stands with pine, although the relationships were weak. The results obtained for two fir-spruce stands were ambiguous. In sum, in the stands studied, small canopy gaps and inter-crown openings might not be considered ‘‘nutrient hot spots’’, and the admixed species, except for beech, had an insignificant effect on nutrient content in the humic mineral horizon.     

Chemical content and seasonal variation of throughfall and litterflow under individual trees in the Hyrcanian forests of Iran

We assessed the effect of seasons and the tree species velvet maple (Acer velutinum Boiss), Hainbuche hornbeam (Carpinus betulus L.) and chestnut-leaved oak (Quercus castanefolia C. A. Mey.; Fagaceae) on nutrient fluxes (Na⁺, K⁺ and Ca²⁺) in throughfall (TF) and litter flow (LF) from January 2012 to February 2013. Potassium (K⁺) and calcium (Ca²⁺) in total TF and LF over the measurement period significantly differed between 3 the species (p < 0.05). Maple and oak trees had significantly higher fluxes of K⁺ and Ca²⁺ in their TF, respectively. The average quantity of nutrients in LF was significantly higher in the leafy season than in the leafless season for all cations except for Na⁺. Under velvet maple trees, the average flux of nutrients (Na⁺, K⁺, and Ca²⁺) in TF was significantly higher than LF. Lastly, leaching of potassium (K⁺) and calcium (Ca²⁺) in LF during the measurement period was significantly lower than TF under the hornbeam trees. Our results suggest that different tree species may impact the nutrient availability and possibly the sustainability of Hyrcanian forests. Further research is needed to determine how managing different species will affect the long-term nutrient status of these forests.     

六盘山华北落叶松林降水转化中的阳离子通量变化特征

在六盘山香水河小流域的华北落叶松人工林样地,测定了2011年生长季降水转化过程中的大气降水、穿透水、干流、枯落物渗透水和主根系层(30 cm土层)土壤渗透水的pH值与多种阳离子的浓度及通量变化.结果表明:林外降水的pH值平均为7.13,转化为穿透雨和干流后降为6.73和6.00,转化为枯落物渗透水和土壤渗透水后回升为6.87和7.28.在降水转为由穿透雨和干流组成的林下降水后,绝大多数阳离子的浓度都不同程度地增大,但Zn2+浓度下降;虽然林冠截持使林下降水的数量减小,但由于雨水对林冠的离子交换及淋洗,林下降水的多数阳离子通量都比林外降水明显增大,K+、Mg2+、H+、Mn2+、Cu2+、Fe3+由林外的17.23、12.51、0.06、0.09、0.13、0.19 mmol·m-2分别上升到林下的141.87、32.93、0.10、0.68、0.24、0.56 mmol·m-2,但Na+、Ca2+、Zn2+的通量分别由林外的33.73、112.91、2.05 mmol·m-2减小为林内的30.70、75.75、1.10 mmol·m-2.在枯落物层渗透水中,绝大多数阳离子的浓度都不同程度地下降,仅Mg2+浓度微弱上升;受枯落物截持部分降水及雨水中阳离子与枯落物交换的影响,枯落物渗透水中所有阳离子的通量都比林下降水明显减小,K+、Na+、Mg2+、Ca2+、H+、Mn2+、Cu2+、Zn2+、Fe3+分别降至83.06、12.30、23.96、65.73、0.04、0.12、0.09、0.13、0.32 mmol·m-2.在主根系层土壤渗透水中,一些阳离子(K+、Mn2+、Cu2、Fe3+)的浓度下降,另一些阳离子(Na+、Mg2+、Ca2+、Zn2+)的浓度则上升,尤其Ca2+浓度显著上升;Na+、M2+、Ca2+、Mn2+、Zn2+的通量比枯落物渗透水增大,其值分别为37.49、62.83、202.41、0.22、1.05 mmol·m-2,但K+、Cu2+、Fe3+的通量比枯落物渗透水减小,其值分别为27.14、0.07、0.09 mmol·m-2.相对于林外降水的阳离子输入通量,林冠层对多数阳离子(除Na+、Ca2+、Zn2+)的通量为净淋出(增加)作用,枯落物层对多数阳离子(除K+、Mg2+、Mn2+、Fe3+)的通量为净固定(减少)作用,主根系层土壤对盐基离子(Na+、K+、Mg2+、Ca2+)和Mn2+的通量为净淋失(增大)作用,但对其他阳离子(H+、Cu2+、Zn2+、Fe3+)的通量为净固定(减少)作用.     

The Application of Fertilizers to Drained Peat 1. Nutrient Losses in Drainage

An experiment to follow the fate of applied fertiliser was installedon a newly-drained raised bog near Edinburgh. Sixteen lysimeters(2.25 m²) were constructed to isolate blocks of peat to 0.8m depth and were allocated to four treatments; untreated control,+ 50 kg P ha^–1 (as rock phosphate), + 100 kg K ha^–1(as KCl), P and K together at these same rates. Fertiliserswere applied in May 1977 and for the following three years drainagewas collected weekly for chemical analysis. The hydrologicalbehaviour of the lysimeters was checked by monitoring run-offfrom an enclosed 2.5 ha catchment. Losses of K in drainage were rapid but declined over the perioduntil they were only slightly greater than control values; lossesof P began after 24 weeks and were greatest in winter with noapparent decline; Ca was not leached and no significant releaseof N was detected. Control lysimeters showed a net loss of Nand P following drainage. When K and P were applied separatelylosses were 39 and 16 per cent respectively but in combinationthe losses were reduced to 26 and 7 per cent. Concentrationsof dissolved P in leachates exceeded 1.0 mgl^–1 on occasionand K fertiliser initially reduced water pH.     

Effect of clear-felling and slash removal on the acidity of Northern coniferous soils

Measurements of pH were carried out at two experimental sites in Sweden before and after clear-felling. At eleven sites, pH, cation-exchange capacity, base saturation and exchangeable hydrogen ions were compared in clear-felled areas where slash was left and removed, respectively. It is shown that pH increases significantly after clear-felling. The increase is larger than can be explained by the release of basic cations in connection with decomposition of slash and humus. The increase in pH is less in a clear-felled area when the slash is removed than when it is left. There is a decrease in exchangeable Ca²⁺, Mg²⁺ and Mn²⁺ and an increase in H⁺ and Al³⁺. There is a decrease in base saturation of about 80%.     

Biogeochemical cycling and chemical fluxes in a managed northern forested wetland, Michigan, USA

Forest harvesting and subsequent regeneration treatments may cause changes in soil and solution chemistry that adversely affect forest productivity and environmental quality. The objective of this study was to assess soil carbon (C), nitrogen (N), and base cation pools and fluxes, and to construct a hydrogen ion (H⁺) mass balance to identify major processes controlling acidity production and consumption 14 years following whole-tree harvesting and regeneration in a northern forested wetland with underlying mineral soils derived from calcareous glacial drift. Results for soil elemental and nutrient pools in the harvested/regenerated stand were compared to an adjacent non-harvested stand and a riparian zone. The riparian zone had the highest soil total C, total N, and exchangeable calcium (Ca) and magnesium (Mg) pools; however, no difference in exchangeable potassium (K) was evident among stand types. Moreover, no differences between the harvested/regenerated and uncut stands were evident in any of the soil chemical pools.Net export of base cations was minimal and the H⁺ mass balance indicated that net cation exchange was not a significant process in H⁺ production or consumption in either the uncut or harvested/regenerated stands. The most striking differences in the H⁺ mass balance were (1) eight times the H⁺ consumption from sulfate (SO₄²⁻) reduction in the harvested/regenerated stand compared to that in the uncut condition and (2) nearly twice the H⁺ production due to N immobilization in the harvested/regenerated stand. However, both stand types were net H⁺ sinks and increases in H⁺ export due to whole-tree harvesting were not evident.The riparian zone was a net exporter of base cations. This finding was attributed to a combination of base cation exchange and carbonate mineral weathering; data suggested the importance of the latter. More research, however, is required to isolate the contributions of cation exchange and carbonate weathering on base cation export from the riparian zone. Stream chemistry was consistent with that of the riparian zone, indicating a strong linkage between the riparian zone stream chemistry, and whole-tree harvesting had no intermediate term (i.e., 14 years) effects on stream acidification in this managed northern wetland ecosystem.     

Cloning of plasma membrane H-ATPase gene in Populus euphratica Oliv.

For this paper, the plasma membrane (PM) H -ATPase gene has been cloned from Populus euphratica Oliv. through a homology based strategy. The isolated 3,210 bp cDNA contains a single 2,862 bp open reading frame (ORF) which encodes a putative H -ATPase protein of 953 amino acid residues, with a significant homology to plasma membrane H -ATPase of Primus persica, Phaseolus vulgaris, Sesbania rostrata and Daucus carota. The predicted protein has a molecular weight of 104,553 Da. The copy number analysis revealed multiple copies of the PM H -ATPase in the P. euphratica genome after digestion of their genomic DNA by the restriction enzymes EcoRI, NdeⅠ, FbaⅠand BglⅡ, and Southern blot.     

Comparison between empirical and theoretical biomass allometric models and statistical implications for stem volume predictions

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 D^8/3 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.     

Phosphorus Nutrition of Lodgepole Pine and Sitka Spruce Stands as indicated by a Root Bioassay

A bioassay for determining P-deficiency, based on the rate ofuptake of ³²P-labelled phosphorus by roots from a standard solutionand developed on pot grown tree seedlings, has been appliedto roots from 10–18 year old lodgepole pine and Sitkaspruce stands in field fertilizer trials on peat. Rates of ³²-phosphorusuptake by roots were negatively related to quantities of P fertilizerpreviously given and to tree heights. The P content of firstwhorl needle samples were generally high but were not significantlydifferent between fertilizer treatments nor related to treeheights. There was, however, a general relationship between rates of³²P uptake by roots and P content of needles over all sitesand tree species. The bioassy, however, rapidly detects changesin internal P status of the tree which takes time to manifestitself in a change of needle P content. Preliminary work suggests that the bioassay detects a P-statusin trees, not identifiable from needle analyses. A number offactors which might influence the results of the bioassay andtherefore the field applicability of the method are discussed.     

The impact of six European tree species on the chemistry of mineral topsoil in forest plantations on former agricultural land

Influences on mineral topsoils of common European tree species (oak-Quercus robur L., lime-Tilia cordata Mill., ash-Fraxinus excelsior L., birch-Betula pendula Roth., beech-Fagus sylvatica L. and spruce-Picea abies (L.) Karst.) were studied in 30 to 40-year-old stands planted in adjacent plots on former arable land. Mineral soil samples from two depth layers (0–10 and 20–30 cm) under the different species were compared in terms of pH, base saturation, pools and concentrations of exchangeable macro- and micronutrients, total nitrogen and carbon. With the exception of pH (H₂O) and extractable Al and Fe, no significant differences between species were detected in the lower layer. The upper (0–10 cm) layer was, however, affected differently depending on tree species: significant differences in pH, base saturation, exchangeable base cations and other nutrients were observed. The most prominent differences were between lime and spruce. Lime had considerably higher pH, base saturation, base cation and boron pools compared to spruce, which had the most acidifying effect on the mineral topsoils. Among the deciduous species, beech had the most similar effect to spruce on the upper layer of mineral topsoils. Soil C, N and C/N ratios did not differ significantly among species.     

Tree species and pruning regime affect crop yield on bench terraces in SW Uganda

Integration of trees on farms may exert complementary or competitive effects on crop yield. This 4 year study examined novel systems in which Alnus acuminata (alnus), Calliandra calothyrsus (calliandra), Sesbania sesban (sesbania) or a mixture of all three were grown on the degraded upper part of bench terraces in Uganda; beans or maize were grown on the more fertile lower terrace during the short and long rains. Three pruning treatments (shoot, root or shoot + root pruning) were applied to the tree rows adjacent to the crops; shoot prunings were applied as green manure to the woodlot from which they came. Pruning increased survival in calliandra and reduced survival in sesbania; alnus was unaffected. Pruning reduced tree height and stem diameter in alnus, but did not affect calliandra or sesbania. Maize yield adjacent to unpruned calliandra, alnus and sesbania or a mixture of all three was reduced by 48, 17, 6 and 24% relative to sole maize. Shoot pruning initially sustained crop performance but shoot + root pruning became necessary when tree age exceeded 2 years; shoot + root pruning increased maize yield by 88, 40, 11 and 31% in the calliandra, alnus, sesbania and tree mixture systems relative to unpruned trees. Bean yield adjacent to unpruned calliandra, alnus, sesbania and the tree mixture was 44, 31, 33 and 22% lower than in sole crops and pruning had no significant effect on crop yield. The results suggest that sesbania fallows may be used on the upper terrace without reducing crop yield on the lower terrace, whereas pruning of alnus is needed to sustain yield. Calliandra woodlots appear to be unsuitable as crop yield was reduced even after pruning.     

Establishing forest tree species on peatland in a reflooded area of the Huleh Valley, Israel

The study evaluates the establishment performance of four treespecies (Ficus carica, Fraxinus syriaca, Salix acmophylla, Platanusorientalis) 3 years after planting in the peatland in the HulehValley. To develop good tree establishment and avoid uprooting,two types of soils were tested as alternatives for the rhizosphere.For each tree 6 m³ of soil (2 x 2 x 1.5 m) were replaced withriver bed alluvium or terra-rossa, in which the tree was planted.Control trees were planted directly in the peat. Changing therhizosphere soil type to river bed alluvium significantly improvedthe establishment and performance of Salix acmophylla and Fraxinussyriaca (survival, height, diameter and canopy shade area).Ficus carica was not affected by changing the soil in the rhizosphere,while Platanus orientalis was affected mainly in canopy shadearea. Terra-rossa improved establishment only of Salix acmophylla;it did not affect the other species.     

Tree effects on the chemical topsoil features of oak, beech and pine forests

We aimed to study tree effects on the chemical properties of forest soils. We compared soil features of three types of forest ecosystems, each with four stands (replicates): beech forests (Fagus sylvatica), oak forests (dominated by Quercus pyrenaica) and pine plantations (Pinus sylvestris). Five samples from the top 10 cm of soil were taken per stand, from which pH, organic matter content (O.M.), total nitrogen (N) and available calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺) and sodium (Na⁺) were determined. Litter layer depth was measured at each soil sampling point. We also measured tree density and crown diameters at each stand. Our results indicated that soil samples from the four pine plantation stands were more similar while oak and beech stands were characterised by great variability in terms of soil properties and leaf litter depth. Although the identity of the dominant tree species significantly influenced several topsoil chemical properties (increase in pH and available cations in oak forests and higher organic matter and total nitrogen in beech and pine ecosystems), there were other important factors affecting soil features that may be taken under consideration. Differences between soil properties of the three types of forest ecosystems were mainly related to the characteristics of the litter layer and less related to the tree layer structure. Finally, the establishment of pine plantations in naturally deciduous tree areas made the topsoil features more homogeneous.     

Changes in Amount and Distribution of Stem Growth in Pole-Stage Corsican Pine Following Application of Nitrogen Fertilizer

Ring-width measurements on trees felled in a nitrogen-deficientpole-stage crop of Corsican pine on the sand dunes of Culbinforest (Morayshire) showed that, in addition to a growth checkascribed to the low nitrogen content of the soil, there wasevidence for decreasing site quality, tree growth decliningprogressively with time. This feature is ascribed to the continuingimmobilization of the limited nitrogen capital in the newlydeveloping mor humus layer. Ammonium sulphate, at rates equivalentto 84, 168, 336, and 504 kg elemental nitrogen ha^–1, wasapplied to this crop when it was 36 years old, and the treatmentsrepeated for a further 2 years. Nitrogen levels in the foliagerose from 0.9 per cent to as high as 20 per cent in the firstyear, increasing to 2.6 per cent after the third year of application.Response in terms of basal area appeared in the year after firstapplication but was not accompanied by any changes in the patternof growth throughout the season, nor was there a significanteffect of tree size on the proportional change in relative basalarea growth induced by the fertilizer, except for a slightlyreduced response by the smallest trees to the lower rates ofapplication. A similar low response by the smallest trees wasfound for height, but, in addition, height growth after treatmentwas greatest for the middle-sized trees, despite the fact thatthese had been growing significantly more slowly than the largesttrees prior to application of the fertilizer. Form factor remainedunaltered by the treatments but taper changed slightly. Heightand basal area showed very different response patterns to thetreatments. Thus, whereas maximum height growth occurred atthe 168 kg N ha^–1 treatment rate (2.41 m over 7 years,1.4 times the control growth) maximum basal area growth occurredat the 504 kg N ha^–1 rate, the highest rate used (13.0m² ha^–1 over seven years, 2.4 times the control growth);volume growth was maximum at the 336 kg N ha^–1 rate (126m³ ha^–1 over 7 years, 2.6 times the control growth). Whenrelated to levels of foliar nitrogen in the previous year, annualheight growth was maximum at 1.6 per cent with maximum basalarea growth occurring nearer 2.2 per cent. It is estimated thatvolume growth would be maximised at just over 20 per cent nitrogen.