Effects of forest management on soil C and N storage: meta analysis

The effects of forest management on soil carbon (C) and nitrogen (N) are important to understand not only because these are often master variables determining soil fertility but also because of the role of soils as a source or sink for C on a global scale. This paper reviews the literature on forest management effects on soil C and N and reports the results of a meta analysis of these data. The meta analysis showed that forest harvesting, on average, had little or no effect on soil C and N. Significant effects of harvest type and species were noted, with sawlog harvesting causing increases (+18%) in soil C and N and whole-tree harvesting causing decreases (−6%). The positive effect of sawlog harvesting appeared to be restricted to coniferous species. Fire resulted in no significant overall effects of fire on either C or N (when categories were combined); but there was a significant effect of time since fire, with an increase in both soil C and N after 10 years (compared to controls). Significant differences among fire treatments were found, with the counterintuitive result of lower soil C following prescribed fire and higher soil C following wildfire. The latter is attributed to the sequestration of charcoal and recalcitrant, hydrophobic organic matter and to the effects of naturally invading, post-fire, N-fixing vegetation. Both fertilization and N-fixing vegetation caused marked overall increases in soil C and N.     

Short- and long-term responses of total soil organic carbon to harvesting in a northern hardwood forest

The long-term response of total soil organic carbon pools (‘total SOC’, i.e. soil and dead wood) to different harvesting scenarios in even-aged northern hardwood forest stands was evaluated using two soil carbon models, CENTURY and YASSO, that were calibrated with forest plot empirical data in the Green Mountains of Vermont. Overall, 13 different harvesting scenarios that included four levels of aboveground biomass removal (20%, 40%, 60% and 90%) and four different rotation lengths (60 year, 90 year, 120 year, and No Rotation (NR)) were simulated for a 360 year period. Simulations indicate that following an initial post-harvest increase, total SOC decreases for several decades until carbon inputs into the soil pool from the re-growth are greater than losses due to decomposition. At this point total SOC begins to gradually increase until the next harvest. One consequence of this recovery pattern is that between harvests, the size of the SOC pool in a stand may change from −7 to 18% of the pre-harvest pool, depending on the soil pool considered. Over 360 years, the average annual decrease in total SOC depends on the amount of biomass removed, the rotation length, and the soil pool considered. After 360 years a stand undergoing the 90yr-40% scenario will have 15% less total SOC than a non-harvested stand. Long-term declines in total SOC greater than 10% were observed in the 60yr-60%, 60yr-90%, and 90yr-90% scenarios. Long-term declines less than 5% were observed in scenarios with 120 year rotations that remove 60% or less of the aboveground biomass. The long-term decreases simulated here for common management scenarios in this region would require intensive sampling procedures to be detectable.     

Topographical differences in soil N transformation using15N dilution method along a slope in a conifer plantation forest in Japan

Soil N transformation was investigated using¹⁵N dilution method along a slope on a conifer plantation forest. Although there was no significant difference in the net N mineralization rates by laboratory incubation, net nitrification rates increased downslope. Gross N transformation by¹⁵N dilution method showed a distinct difference not only on the rates, but also on the main process between the lower and the upper of the slope. Half of minelarized N was immobilized and the other half was left in NH ₄ ⁺ pool at the upper part of the slope, while all of mineralized N was used for immobilization or nitrification and NH ₄ ⁺ pool decreased at the lower of the slope. Soil N transformations were classified into two groups: one was shown below 773 m and the other was shown above 782 m. The incubation with nitrification inhibitor showed that nitrification was mainly conducted by autotrophs irrespective of the position of the slope. Microbial biomass and microbial C/N were similar among the sites. However, the gross mineralization rate was higher below 773 m than above 782 m under similar respiration rates. This suggests that the substrate quality may be one of the controlling factors for soil N transformation. Extractable organic C/N was similar to microbial C/N at the lower of the slope. It indicated that the substrate was more decomposable below 773 m. It is considered that soil N transformation is affected by topographical gradient of moisture and nutrient which makes plant growth and decomposition rate different.     

Responses of labile soil organic carbon and enzyme activity in mineral soils to forest conversion in the subtropics

Aims

Globally, extensive areas of native forest have been almost replaced by plantations to meet the demands for timber, fuel material and other forest products. This study aimed to evaluate the effects of forest conversion on labile soil organic C (SOC), soil respiration, and enzyme activity, and to quantify their relationship in subtropical forest ecosystems.

Methods

Surface mineral soil (0–20 cm) was collected from a Cunninghamia lanceolata Hook. plantation, Pinus massoniana Lamb. plantation, Michelia macclurei Dandy plantation, and an undisturbed native broadleaf forest. Soil microbial biomass C, dissolved organic C, permanganate-oxidizable C, basal respiration, and six enzyme activities were investigated.

Results

Soil microbial biomass C was higher by 45.9 % in native broadleaf forest than that in M. macclurei Dandy plantation. The ratio of soil microbial biomass C to total SOC was 27.6 % higher in the M. macclurei Dandy plantation than in the native broadleaf forest. The soil respiration increased by 25.2 % and 21.7 % after conversion from native broadleaf forest to P. massoniana Lamb. and M. macclurei Dandy plantations respectively. The effects of forest conversion on the soil enzyme activities differed among the tree species. Soil microbial biomass C had higher correlation with soil respiration than with the other SOC fractions. Moreover, soil microbial biomass C was positively correlated with urease and negatively correlated with cellulase activity. Soil respiration had higher correlation with soil microbial biomass C, dissolved organic C and permanganate-oxidizable C.

Conclusion

Forest conversion affected the soil microbial biomass C, soil respiration, invertase, cellulase, urease, catalase, acid phosphatase, and polyphenol oxidase activities, but their response depended on tree species. Soil respiration was mainly controlled by labile SOC, not by total SOC.     

13C and 15N isotopic fractionation in trees, soils and fungi in a natural forest stand and a Norway spruce plantation

¹⁵N and ¹³C natural abundances of foliage, branches, trunks, litter, soil, fungal sporophores, mycorrhizas and mycelium were determined in two forest stands, a natural forest and a Norway spruce plantation, to obtain some insights into the role of the functional diversity of saprotrophic and ectomycorrhizal fungi in carbon and nitrogen cycles. Almost all saprotrophic fungi sporophores were enriched in ¹³C relative to their substrate. In contrast, they exhibited no or very little shift of δ¹⁵N. Judging from the amount of C discrimination, ectomycorrhizal fungi seem to acquire carbon from their host or from dead organic matter. Some ectomycorrhizal species seem able to acquire nitrogen from dead organic matter and could be able to transfer it to their host without nitrogen fractionation, while others supply their host with ¹⁵N-depleted nitrogen. Moreover ectomycorrhizal species displayed a significant N fractionation during sporophore differentiation, while saprotrophic fungi did not.     

Influence of tree internal N status on uptake and translocation of C and N in beech: a dual 13C and 15N labeling approach

Influence of plant internal nitrogen (N) stocks on carbon (C) and N uptake and allocation in 3-year-old beech (Fagus sylvatica L.) was studied in two 15N- and 13C-labeling experiments. In the first experiment, trees were grown in sand and received either no N nutrition (-N treatment) or 4 mM unlabeled N (+N treatment) for 1 year. The -N- and +N-pretreated trees were then supplied with 4 mM 15N and grown in a 13CO2 atmosphere for 24 weeks. In the second experiment, trees were pretreated with 4 mM 15N for 1 year and then supplied with unlabeled N for 24 weeks and the remobilization of stored 15N was monitored. On the whole-plant level, uptake of new C was significantly reduced in -N-pretreated trees; however, partitioning of new C was not altered, although there was a trend toward increased belowground respiration. The amount of N taken up was not influenced by N nutrition in the previous year. In +N-pretreated trees, partitioning of new N was dominated by the fine roots (59.7% at Week 12), whereas in -N-pretreated trees, partitioning of new N favored stem, coarse roots and fine roots (24, 21 and 31.9%, respectively, at Week 12), indicating the formation of N stores. The contribution of previous-year N to leaf N was about 15%. The N remobilized for leaf formation had been stored in stem and coarse roots. We conclude that, within a growing season, the growth of beech is strongly determined by the availability of tree internal N stores, whereas the current N supply is of less importance.     

Changes in soil N mineralization and nitrification pathways along a mixed forest chronosequence

Changes in soil N mineralization pathways occurring along a full rotation cycle have received little attention to date, while tree uptake for N may change during forest ageing. The aims of this study were (i) to characterize changes in potential net N mineralization and potential net nitrification within organic layers and the topsoil (organo-mineral horizon) along a 100-year chronosequence for a temperate oak–hornbeam forest and (ii) to reveal covariances between potential net N mineralization pathways and the properties of the humic epipedon (defined as the sum of organic layers and topsoil). For that purpose, a space-for-time substitution procedure and aerobic laboratory incubation method for 28 days at 28 °C in the dark were used. In addition, acetylene and captan were used to discriminate between autotrophic and heterotrophic (bacterial and/or fungal) nitrification. Several humic epipedon properties were determined, e.g. pH, exchangeable cation concentrations, effective cation exchange capacity, total C and N, dissolved organic C and N, fungal and microbial biomass N. Potential net N mineralization and nitrification pathways changed greatly along the mixed forest chronosequence. Potential net N mineralization in the organic layers increased with stand maturation whereas potential net nitrification in the topsoil decreased significantly. Selective inhibitors revealed changes in nitrification pathways along the chronosequence, i.e. potential net nitrification was autotrophic in the topsoil while it was mainly heterotrophic within the organic layers. In the organic layer, potential net nitrification was autotrophic at the onset of the chronosequence while it appeared heterotrophic during the aggradation phase and finally fungal in mature stands. A Co-Inertia Analysis was used to reveal covariances between N mineralization pathways and humic epipedon properties. The analysis showed two functional temporal shifts within N cycling along the chronosequence, one probably controlled by organic matter quality and high competition for available N resulting in the autotrophic versus heterotrophic nitrification shift in the organic layers and one mainly controlled by (i) fine organic matter abundance, allowing high N mineralization in the organic layers and (ii) acidity inhibited autotrophic nitrification in the topsoil.     

Foliar C/N stoichiometry in urban forest trees on a global scale

Foliar C/N stoichiometry is an indicator of geochemical cycling in forest ecosystems,but the driving changes for its response to urbanization at the wide scale is not clear.In this study,data on tree-leaf C and N stoichiometry were collected in papers from across 105 tree species from 82 genera and 46 families.The foliar C/N of urban forest trees varied among different climate zones and tree taxonomic variation and tended to be higher in trees of urban forests near the equator and in eastern regions,mainly driven by lowered foliar N concentration.Neither the foliar C concentration nor foliar C/N for trees of urban forests was statistically higher than those of rural forests.For variation by taxonomic classification,C_4 species Amaranthus retroflexus and Chenopodium ambrosoides(Amaranthaceae) had lower foliar C/N than did other species and families.Myrsine guianensis(Primulaceae) and Myconia fallax(Asteraceae) had the highest foliar C/N.Therefore,urbanization has not caused a significant response in forest trees for foliar C/N.The change in foliar N concentration was globally the main force driving of the differences in foliar C/N for most tree species in urban forests.More work is needed on foliar C/N in trees at cities in polar regions and the Southern Hemisphere.     

Effect of tree species on carbon stocks in forest floor and mineral soil and implications for soil carbon inventories

Forest soil organic carbon (SOC) and forest floor carbon (FFC) stocks are highly variable. The sampling effort required to assess SOC and FFC stocks is therefore large, resulting in limited sampling and poor estimates of the size, spatial distribution, and changes in SOC and FFC stocks in many countries. Forest SOC and FFC stocks are influenced by tree species. Therefore, quantification of the effect of tree species on carbon stocks combined with spatial information on tree species distribution could improve insight into the spatial distribution of forest carbon stocks.We present a study on the effect of tree species on FFC and SOC stock for a forest in the Netherlands and evaluate how this information could be used for inventory improvement. We assessed FFC and SOC stocks in stands of beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii), Scots pine (Pinus sylvestris), oak (Quercus robur) and larch (Larix kaempferi).FFC and SOC stocks differed between a number of species. FFC stocks varied between 11.1 Mg C ha⁻¹ (beech) and 29.6 Mg C ha⁻¹ (larch). SOC stocks varied between 53.3 Mg C ha⁻¹ (beech) and 97.1 Mg C ha⁻¹ (larch). At managed locations, carbon stocks were lower than at unmanaged locations. The Dutch carbon inventory currently overestimates FFC stocks. Differences in carbon stocks between conifer and broadleaf forests were significant enough to consider them relevant for the Dutch system for carbon inventory.     

磷添加对南亚热带森林土壤有机碳氮矿化影响的培养实验研究

采用室内培养的方法,分析了磷添加对南亚热带鼎湖山马尾松林（PMF）、针阔叶混交林（PBMF）和季风常绿阔叶林（MEBF）土壤（0～10cm）CO小CH4排放／吸收和有机氮矿化的影响。结果表明：28周的培养,100mg磷添加处理土壤C—CO2累积排放量依次为PMF、PBMF和MEBF对照的82．4％、84．4％和102．8％,2000mg磷处理土壤依次为其对照的107．2％、101．2％和109．1％;100mg磷处理土壤CH4累积排放量依次为其对照的69．9％、102．7％和66．3％,2000mg磷处理土壤依次为其对照的-57．4％、25．3％和22．4％,其中,磷在处理初期较一致的提高土壤CO2和CH4排放,磷对土壤有机碳矿化的影响与森林的土壤状况有关,添加的磷浓度越高,其促进作用越强。1周的培养,100mg磷处理土壤有效氮净矿化量依次比PMF、PBMF和MEBF对照少37．06％、39．60％和28．62％,2000mg磷处理土壤依次比其对照少70．97％、84．14％和187．97％,100mg磷处理土壤硝态氮净矿化量依次比其对照少48．06％、40．45％和28．03％,2000mg磷处理土壤依次比其对照少254．09％、115．32％和238．50％,磷显著的抑制土壤有机氮的矿化和硝化。结果建议,在研究P对土壤有机碳氮矿化过程时应充分考虑土壤对P的吸附作用。     

Effect of gap size and forest type on mineral nitrogen forms under different soil properties

Gaps play a key role in forest ecosystem development and result from either natural processes or targeted forest management activities.The aim of this study was to investigate the interrelationships of soil properties in each of three forest types and two treatments,and to identify factors that influence levels of soil mineral nitrogen forms.The relation between mineral nitrogen and factors of soil parameters and stand type(European beech,Norway spruce,mixed stand)categories were investigated.The spruce forest type stored significant nitrogen in both mineral forms of nitrogen.Moreover,there was a significant linear dependence between N-NO3^-(nitrate anion)concentrations and cation exchange capacity(CEC)parameters such as base cation contents(S-CEC)and potential ureolytic activities(UreasePot),as well as between N-NH4^+(ammonium cation)concentrations and both hydrolytic acidities(Ha-CEC)and ureolytic activities.The dependence of N-NO3^-concentrations on S-CEC contents and UreasePot was negative,especially in adjacent stand.The dependence of N-NH4^+concentrations on Ha-CEC and UreasePot was week in the beech and mixed forest types while it was significantly positive in the spruce forest type.     

Distribution of persistent organic pollutants in aggregate fractions of a temperate forest and semi-rural soil

The fate of persistent organic pollutants(POPs)and their interactions with aggregates of forest soils are not completely understood.Our objectives here were to quantify the distribution of different POPs in waterstable aggregate fractions and to study their influence on soil organic carbon(C_(org)) content.Soil samples were taken from a forest-site,Gogerddan(G) and a semi-rural site,Hazelrigg(H) in Great Britain,from 0–2 and 2–5 cm and 0–4 and 8–12 cm soil depth,respectively.POPs analyzed were PAHs,PCBs,total DDT,PBDEs and HCB.The bulk soil analysis showed that the concentration of POPs was significantly higher(p≤0.05) in forest site G than in semi-rural site H,particularly at the surface soil levels compared to the subsurface soil depths in both sites.Total concentrations of PCBs and PAHs of both sites were positively correlated with C_(org) contents.POPs concentrations and C_(org) ,Ntcontents of forest site G were significantly higher(p≤0.05) in water-stable macro aggregates(0.25,1,2 mm) than the micro aggregates(0.053 mm).The POP concentrations of all aggregate fractions after normalizing to their respective C_(org) content were increased due higher contamination and strong sorption by C_(org) .These results showed a strong effect of C_(org) on the partitioning of organic pollutants to soil aggregate size fractions.The present study affirms the ecological significance of forest soils act as a potential sink of POPs.In summary,our results suggest that aggregate fractions may promote soil C storage and act as a potential POP sink in surface soil without increasing their concentration in the aggregate fraction of subsoil.     

Effects of soil moisture and temperature on CH4 oxidation and N2O emission of forest soil

IntroductionMethane (CH4) and Nitrous oxide (NZO) are tWoimportant greenhouse gases that also play an important role in photochemical reactions in atmosphere.The global warming potential of CH4 and NZO areestimated tO be about 62 and 290 times that of carbon dioxide respeCtively. The concentration of thesegases have been increasing rapidly since the start ofthe industrial age, currently at rate of about 1% and0.25% per year respeCtively (Lelieveld et al. 1993),and 70%-90% of these gases …     

Effects of soil moisture and temperature on CH4 oxidation and N2O emission of forest soil

Soil samples were taken from depth of 0–12 cm in the virgin broad-leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L⁻¹ and 200 μL·L⁻¹ CH₄ and N₂O concentration were supplied for analysis. Laboratory study on CH₄ oxidation and N₂O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N₂O. Air-dried soil sample could not oxidize atmospheric methane, but could product N₂O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L⁻¹. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N₂O emissions within 2 hours. There were curvilinear correlations between N₂O emission and temperature (r²=0.706, p<0.05), and between N₂O emission and water content (r²=0.2968, p <0.05). These suggested temperature and water content were important factors controlling N₂O emission. The correlation between CH₄ oxidization and temperature was also found while CH₄ was supplied 200 μL·L⁻¹ (r²=0.3573, p<0.05). Temperature was an important factor controlling CH₄ oxidation. However, when 20 μL·L⁻¹ CH₄ was supplied, there was no correlation among CH₄ oxidization, N₂O emission, temperature and water content. Foundation item: This paper was supported by Chinese Academy of Sciences. Biography: ZHANG Xiu-jun (1960-), female, Ph. Doctor, lecture in Laboratory of Ecological Process of Trace Substance in Terrestrial Ecosystem, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110015, P.R. China. Responsible editor: Song Funan     

Anthropogenic disturbance of natural forest vegetation on calcareous soils alters soil organic matter composition and natural abundance of <Superscript>13</Superscript>C and <Superscript>15</Superscript>N in density fractions

In the last century, many calcareous soils in Castilla León (northwestern Spain) have been transformed from natural Quercus ilex forest to cropped land. Reforestation with Pinus halepensis has been taking place during the past 40 years. In order to obtain a better understanding of how these disturbances affect ecosystem functioning, we studied the quantity and quality of soil organic matter (SOM) in natural forest ecosystems, cropland and Pinus plantations. Density fractionation combined with ultrasonic dispersion enables separation and study of SOM fractions: free organic matter (OM), OM occluded into aggregates and OM stabilized in organo-mineral complexes, considered on the basis of the type of physical protection provided. We separated SOM density fractions and determined the concentrations of C and N, C/N ratios and the natural isotopic abundance (δ¹³C and δ¹⁵N values). Transformation of Quercus forest to cropland resulted in major losses of SOC and N, as expected. However, subsequent reforestation with Pinus resulted in good recovery of the original SOC and soil N pools. This indicates the potential for enhanced C storage in agricultural soils by their reversion to a forested state. Study of the density fractions and their ¹³C and ¹⁵N signatures enabled better understanding of the high stability of OM in calcareous soils, and analysis of δ¹³C variations throughout the profile also enabled identification of past C3/C4 vegetation change. Despite the different OC contents of soils under different land use, OM stabilization mechanisms were not significantly different. In calcareous soils, accumulation of SOC and N is mainly due to organo-mineral associations, resulting in physicochemical stabilization against further decomposition.     

土壤林木营养诊断与平衡施肥现状及展望

简要概述土壤和林木营养诊断的理论基础、技术方法发展动态、应用现状,阐述土壤和林木营养诊断的必要性,并结合福建省的具体情况,提出土壤林木营养诊断与平衡施肥研究的建议与展望,为现代林业经营管理提供参考。     

Effects of long-term nitrogen addition and seasonal variation on soil faunal community structure in a temperate natural secondary forest

Elevated nitrogen (N) deposition is changing soil communities around the world and will have unknown consequences for terrestrial ecosystem functions. In this study, we investigated a field experiment that lasted for 13 years to explore the effect of simulated N deposition and seasonal variations on the soil faunal community structure in a temperate natural secondary forest. The experimental design included a control group (0 kg N ha^?1 yr^?1, CK), low N addition (25 kg N ha^?1 yr^?1, LN), and high N addition (50 kg N ha^?1 yr^?1, HN). The results showed that long-term high N addition reduced the soil pH, C/N ratio, and microbial biomass carbon (MBC) and increased the total phosphorus. The soil faunal community structure after high N addition was significantly different from those after the CK and low N addition treatments. The overall trend was that abundance and richness increased under low N addition and decreased under high N addition. Further analysis showed that the abundance of omnivores and detritivores was lowest after high N addition, significantly less than the CK and low N addition. The interaction of N addition and seasonal dynamics had a significant impact on herbivores. We found that these changes were driven by differences in ecological strategies such as food and environmental preferences. Furthermore, temperature, moisture, nutrients, and pH in the soil environment were the key factors driving ecological strategies and environmental factors. Seasonal variations significantly affected the soil faunal community structure, showing the highest abundance, richness, diversity, and functional group abundance and richness of the soil faunal community in September. Nitrogen addition and seasonal dynamics significantly affected the abundance and richness of soil fauna by changing soil nutrient concentrations, MBC, and plant diversity. Our study showed that long-term high N addition reduced the abundance and functional group abundance of the soil fauna in natural secondary forests, while low N addition had a positive effect on soil faunal community structure. Collectively, the results suggest that the seasonal balance of soil fauna is affected after long-term N addition, which increases the seasonal sensitivity of soil fauna.

     

The Level II aggregated forest soil condition database links soil physicochemical and hydraulic properties with long-term observations of forest condition in Europe

Key message

Aggregated, consolidated, and derived soil physicochemical data of 286 ICP Forests Level II plots were completed with soil hydraulic properties for integrated use with forest monitoring data. Database access should be requested at http://icp-forests.net . Metadata associated available at https://metadata-afs.nancy.inra.fr/geonetwork/apps/georchestra/?uuid=153e599e-6624-4e2b-b862-8124386ea9cd&hl=eng

Context

The ICP Forests database is one of the most comprehensive forest ecosystem datasets in Europe and contains the accumulated results of more than two decades of harmonised forest monitoring all over Europe.

Aims

The aim of this paper is to share knowledge on the ICP Forests Level II soil data for broader use among forest scientists.

Methods

After standard analysis, quality checks, aggregation, and calculation of derived variables (e.g. nutrient stocks, base saturation, C:N ratio, and water retention parameters), data have been gathered into a static database (AFSCDB.LII.2.2), which will be updated to new versions as soon as new measurements become available.

Results

The database provides a basis for the combined evaluation of up to 130 unique soil variables of 286 plots with dynamic data on tree growth, ground vegetation, foliar chemistry, crown condition, tree phenology, leaf area index, ozone injury, litterfall, soil solution chemistry, deposition, ambient air quality, and meteorological data assessed on the same plots.

Conclusion

The unprecedented comprehensiveness and level of detail in this newly aggregated database may overcome existing restrictions so far impeding the realisation of large-scale forest ecosystem studies in Europe.

     

Tracing the fate of mineral N compounds under high ambient N deposition in a Norway spruce forest at Solling/Germany

The fate of high and equally distributed ammonium and nitrate deposition was followed in a 72-year-old roofed Norway spruce forest at Solling in central Germany by separately adding ¹⁵NH₄⁺ and ¹⁵NO₃⁻ to throughfall water since November 2001. The objective was to quantify the retention of atmospheric ammonium and nitrate in different ecosystem compartments as well as the leaching loss from the forest ecosystem. δ¹⁵N excess in tree tissues (needles, twigs, branches and bole woods) decreased with increased tissue age. Clear ¹⁵N signals in old tree tissues indicated that the added ¹⁵N was not only assimilated to newly produced tree tissues but also retranslocated to old ones. During a period of over 3-year ¹⁵N addition, 30% of ¹⁵NH₄⁺ and 36% of ¹⁵NO₃⁻ were found in tree compartments. For both ¹⁵N tracers, 15% of added ¹⁵N was found in needles, followed by woody tissues (twigs, branches and boles, 7–13%) and live fine roots (7%). The recovery of ¹⁵NH₄⁺ and ¹⁵NO₃⁻ in the live fine roots differed with soil depth. The recovery of ¹⁵NH₄⁺ tended to be higher in the live fine roots in the organic layer than in the upper mineral soil. In the live fine roots in deeper soil, the recovery of ¹⁵NO₃⁻ tended to be higher than that of ¹⁵NH₄⁺. Soil retained the largest proportion of ¹⁵N, accounting for 71% of ¹⁵NH₄⁺ and 42% of ¹⁵NO₃⁻. Most of ¹⁵NH₄⁺ was recovered in the organic layer (65%) and the recovery decreased with soil depth. Conversely, only 8% of ¹⁵NO₃⁻ was found in the organic layer and 34% of ¹⁵NO₃⁻ was evenly distributed throughout the mineral soil layers. Nitrate leaching accounted for 3% of ¹⁵NH₄⁺ and 19% of ¹⁵NO₃⁻. Only less than 1% of the both added ¹⁵N was leached as DON. These results suggested that trees had a high contribution to the retention of atmospheric N and soil retention capacity determined the loss of atmospheric N by nitrate leaching.