Nutrient status in needles of Norway spruce and Scots pine following harvesting of logging residues

Nutrient concentrations in current and 1-year old needles from two Picea abies (L.) Karst and two Pinus sylvestris L. stands in Sweden were determined 8–10, 16–18 and 22–24 years after clear-felling and experimental manipulation of harvesting intensity. On all sites, three levels of harvest intensity had been applied in a randomized block design (n=4); (i) conventional stem-only harvesting, where all logging residues (i.e. tops, branches and needles) were evenly distributed on the ground, (ii) harvesting all above-ground tree parts except needles and (iii) above-ground whole-tree harvesting (no residues left on site). At stand age 8–10 years, nitrogen concentrations in the current year needles in plots where all residues or needles only were retained were higher than in whole-tree harvested plots, whereas concentrations of K, Ca and Mg were lower. The latter response was interpreted as a dilution effect. P:N, K:N, Ca:N, Mg:N, Mn:N and Zn:N were in general higher after whole-tree harvesting treatments than after the treatments where all residues or only needles had been left on site. At stand age 16–18 years, no significant differences in nitrogen concentrations were observed between treatments, but the levels of Ca, Mg and Mn in both current and 1-year-old needles were lower after whole-tree harvesting than after the treatments where logging residues remained on site. By contrast, potassium levels in the foliage were highest in treatments where only the needles were left on site, whereas the lowest levels were observed for treatments where all residues was left. At stand age 22–24 years, the treatment effects had diminished, except for the effects on Ca and K on the southern Norway spruce stand. It is concluded that the nutrient release from logging residues enhances nutrient uptake in trees of the succeeding forest generation, but this effect does not occur simultaneously for all elements. This revised version was published online in June 2006 with corrections to the Cover Date.     

Soil fertility of afforested arable land compared to continuously

In Finland, over 220,000 ha of arable land has been afforested in recent decades. To meet the goals of forest management on afforested fields, information on the effects of former agricultural land use on soil fertility is needed. In this study, we examine the soil fertility of 12 former arable fields afforested either 10 or 60–70 years ago with Norway spruce (Picea abies (L.) Karst.) and adjacent sites that have been forested continuously. Volumetric soil samples were collected from the organic soil layer and from mineral soil to a depth of 40 cm. Soil samples were analyzed for pH, bulk density, organic matter content and amounts of nutrients (Kjeldahl N, extractable P, K, Ca, Mg, Zn and B). On afforested fields, amounts of nutrients in the mineral soil, especially in 10-year-old afforestations, were higher than on continuously forested sites. In the organic layer plus the 0–40 cm soil layer, the 10-year-old afforestations had 68% more N, 41% more P, 83% more K, 252% more Ca, 6% more Mg, 61% more Zn and 33% more B than the continuously forested sites at a comparable soil depth. In the 60–70-year-old afforestations, the differences were significant only for N, Ca and Zn (20% more N, 121% more Ca and 115% more Zn than on the continuously forested sites). The effects of agriculture on amounts of nutrients were most clearly detected in the former plough layer (0–20 cm) of the 10-year-old afforestations and in the top layer (0–10 cm) of the older afforestations. Amounts of nutrients in the organic layer of the afforested sites were lower, but their concentrations were higher than in the continuously forested sites. On the 10-year-old afforestations, the bulk density of the mineral soil tended to be lower and the organic matter content higher than on the continuously forested sites. On both young and old afforestations, soil pH was higher than on the continuously forest sites. According to these results, changes in soil properties caused by agriculture have increased the soil fertility and therefore probably also the site index. The results also suggest that changes in soil properties due to agricultural land use are quite long lasting.     

Under-storey Nutrient Content in an Age Sequence of Douglas-fir Stands

The nutrient concentrations and contents of the under-storeyspecies were estimated for a series of Pacific North-west Douglas-fir[Pseudotsuga menxiessii (Mirb.) Franco] stands ranging in agefrom 9 to 95 years. Analyses were carried out for ash, N, P,K, Ca, Mg, Mn, Fe, Zn and Na and significant differences innutrient concentrations were found to exist between species;species rejecting certain nutrients and accumulating others.General trends for mean concentrations of some nutrients areassociated with stand maturity in that ash, K and Mg decline,P and Mn increase and N and Ca reaches a peak at 20–30years and then declines. The nutrient contents (kg ha^–1)of the under-storey component of the stands are presented andtrends discussed. Mineral nutrient content, under-storey vegetation, Pseudotsuga menziessii stands, Douglas-fir     

The effect of soil nutrient availability on retranslocation of Ca,Mg and K from senescing sapwood in Atlantic white cedar

Nutrient resorption from senescing tissues increases plant nutrient-use efficiency, and may be an adaptation to nutrient limitation. In some tree species, retranslocation of nutrients from sapwood during heartwood formation is a comparable process. We measured Ca, Mg and K concentrations in Atlantic white cedar (Chamaecyparis thyoides) stemwood samples taken from two swamps in the northeastern United States and compared them to soil mineral nutrient availability at each site. We found that Ca, Mg and K concentrations were 60–700% higher in sapwood than in the immediately adjacent heartwood, indicating retranslocation of these nutrients from senescing sapwood. Sapwood nutrient concentrations were similar between the two sites. However, nutrient concentrations in the heartwood differed significantly between the sites, as did the relative degree of Ca and Mg retranslocation from senescing sapwood. We found these differences between sites to be inversely related to significant differences in exchangeable Ca, Mg and K as well as Al concentrations in the soil. These findings suggest that the degree of nutrient retranslocation from senescing sapwood may be influenced by soil nutrient availability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in the Above- and Below-ground Biomass and Nutrient Pools of Ground Vegetation After Clear-cutting of a Mixed Boreal Forest

Ground vegetation may act as a sink for nutrients after clear-cutting and thus decrease leaching losses. Biomass and nutrient (N, P, K, Ca) pools of ground vegetation (mosses, roots and above-ground parts of field layer) were determined one year before and five years after clear-cutting of a Norway spruce (Picea abies (L.) H. Karst.) dominated boreal mixed forest stand in eastern Finland (63°51′ N, 28°58′ E). Before clear-cutting the average biomass of ground vegetation was 5307 kg ha⁻¹, with nutrient contents of 46.9 kg N ha⁻¹1, 4.1 kg P ha⁻¹1, 16.2 kg K ha⁻¹1 and 13.9 kg Ca ha⁻¹1. The biomass and nutrient pools decreased after clear-cutting being lowest in the second year, the biomass decreasing by 46–65% in the cut plots. The nutrient pools decreased as follows: N 54–72%, P 36–68%, K 51–71% and Ca 57–74%. The decrease in ground vegetation nutrient uptake, and the observed reduced depth of rooting may decrease nutrient retention after clear-cutting and decomposing dead ground vegetation is a potential source of leached nutrients. These negative effects of clear-cutting on the nutrient binding capacity of ground vegetation was short-lived since the total biomass and nutrient pools returned to pre-cutting levels or were even greater by the end of the 5-year study period.     

Nutrient balance and P,K, Ca,Mg, S and B accumulation in a Norway spruce stand following ammonium sulphate application,fertigation, irrigation,drought and N-free-fertilisation

The nutrient balance and above ground accumulation of macro nutrients, except for N, resulting from improved or deteriorated availability of water and nutrients in a 25 year old Norway spruce stand in SW Sweden is presented. The site and the productivity of the stand is typical for the area. Treatment include irrigation (I); artificial drought (D1); ammonium sulphate addition (NS); N-free-fertilisation (V) and irrigation with liquid fertilisers including a complete set of nutrients according to the Ingestad principle (IF). At start of the experiment the stand contained 86.5 t dry mass, 342 kg N, 33 kg P, 142 kg K, 172 kg Ca, 36 kg Mg and 34 kg S ha^-1. Enhanced accumulation vs control of S was seen in the NS and IF treatments. In the V and IF treatments P accumulation was 7–9 times higher and Ca and Mg, 2–4 times higher compared to the control. K accumulation was increased for the IF treatment. B that accumulated in the needles was decreased in the NS and D1 treatments and increased in the IF and V treatments, as compared to the control. The gross accumulation of nutrients relative to the amounts added was in the IF and V treatments 56 and 47% for P, 40 and 64% for K, 40 and 24% for Mg and, 22 and 8% for S, respectively. We conclude that application with N-free fertilizer, Skogvital (V), including macro nutrients and essential micro nutrients, results in a fast and efficient accumulation above ground of P, K, Ca, Mg and B. The treatment is efficient when aiming at restoring nutrient imbalances in Norway spruce. Application with ammonium sulphate at a rate of 5–6 times higher than the current deposition of N and S did not lead to decreased accumulation above ground of any of the macro nutrients P, K, Ca or Mg. The accumulation of B, however, was significantly reduced. Results from this and other studies indicate that today, N alone, generally is a growth limiting nutrient for Norway spruce in Southern Sweden.     

Dynamics of Nutrient Translocation in Stemwood across an Age Series of a Eucalyptus Hybrid

Despite the continuous nature of growth of eucalyptus hybridsin Congo, taper functions fitted to stem profiles of one clonethroughout stand development, combined with annual tree measurements,made it possible to locate accurately the position of annualrings in stems. Annual rings were identified on discs of woodsampled every 4 m in four trees cut from 1-, 2-, 3-, 4-, 5-,6- and 7-year-old stands. Chemical analysis, performed individuallyfor each ring per level and per tree sampled, made it possibleto quantify the changes in nutrient content of the rings duringstand development. Nutrient translocation in stemwood was thuscalculated in a stepwise manner between trees of two successiveages. The cumulated nutrient translocations in stemwood fromthe 1-year-old stage to the 6-year-old stage amounted to 18·5kg ha^-1N, 4·2 kg ha^-1P, 38·8 kg ha^-1K, 1·5kg ha^-1Ca and 3·2 kg ha^-1Mg. They represented 11, 18,121, 6, and 15% of the amounts of N, P, K, Ca and Mg accumulatedin stemwood, respectively, at the 7-year-old stage (loggingage). Negative translocations of N, P, Ca and Mg in stemwoodbetween 6 and 7 years might indicate an improvement in the nutritivestatus of the stand at the end of the rotation. Much translocationof K in stemwood suggests that this process might be involvedin the high use efficiency of this element. Copyright 2001 Annalsof Botany Company Translocation, stemwood, ring, nutrient, Eucalyptus, age series     

Nutrient dynamics of drained peatland forests

Forest drainage has been used rather widely to improve tree growth in peatlands in northern and northeastern Europe and some parts of North America. The consequent fundamental change in the vegetation presumably gives rise to a concomitant change in the distribution of nutrients within the ecosystem. We investigated the post-drainage dynamics of soil properties (top 30-cm) and tree stand biomass on a series of peatlands drained for forestry in Finland to evaluate the sufficiency of soil nutrient pools for production forestry, and the ability of a floristic-ecological peatland site type classification for estimating soil nutrient status. The nutrient dynamics were assessed by comparing the nutrient pools in a large number of peatland sites differing in drainage age. Drainage unambiguously influenced stand biomass and structure and, consequently, the nutrient pool bound in trees. Nevertheless, with the exception of Mg, ditching did not decrease soil nutrient pools over the 75-year observation period. Thus, the soil pools seem sufficient for forest production on these sites. The decreasing trend in the soil Mg pool points on a potential risk in the long run, however. Peat depth and temperature sum were identified as significant sources of variation for the soil nutrient pools. Using soil Ca, K, Fe and N pools, on average 49% of our sites were grouped correctly according to the floristic-ecological site type classification. This classification most successfully described soil nutrient status among the most nutrient-poor sites. We concluded that the floristic-ecological classification of drained peatlands successfully describes their production potential, but not their total nutrient pools in varying thermoclimatic conditions.     

Carbon, nitrogen and phosphorus in volcanic soils following afforestation with native birch (Betula pubescens) and introduced larch (Larix sibirica) in Iceland

Afforestation has become an important tool for soil protection and land reclamation in Iceland. Nevertheless, the harsh climate and degraded soils are growth-limiting for trees, and little is know about changes in soil nutrients in maturing forests planted on the volcanic soils. In the present chronosequence study, changes in C, N and total P in soil (0–10 and 10–20 cm depth) and C and N in foliar tissue were investigated in stands of native Downy birch (Betula pubescens Enrh.) and the in Iceland introduced Siberian larch (Larix sibirica Ledeb.). The forest stands were between 14 and 97 years old and were established on heath land that had been treeless for centuries. Soils were Andosols derived from basaltic material and rhyolitic volcanic ash. A significant effect of tree species was only found for the N content in foliar tissue. Foliar N concentrations were significantly higher and foliar C/N ratios significantly lower in larch needles than in birch leaves. There was no effect of stand age. Changes in soil C and the soil nutrient status with time after afforestation were little significant. Soil C concentrations in 0–10 cm depth in forest stands older than 30 years were significantly higher than in heath land and forest stands younger than 30 years. This was attributed to a slow accumulation of organic matter. Soil N concentrations and soil P_tot were not affected by stand age. Nutrient pools in the two soil layers were calculated for an average weight of soil material (400 Mg soil ha⁻¹ in 0–10 cm depth and 600 Mg soil ha⁻¹ in 10–20 cm depth, respectively). Soil nutrient pools did not change significantly with time. Soil C pools were in average 23.6 Mg ha⁻¹ in the upper soil layer and 16.9 Mg ha⁻¹ in the lower soil layer. The highest annual increase in soil C under forest compared to heath land was 0.23 Mg C ha⁻¹ year⁻¹ in 0–10 cm depth calculated for the 53-year-old larch stand. Soil N pools were in average 1.0 Mg N ha⁻¹ in both soil layers and did not decrease with time despite a low N deposition and the uptake and accumulation of N in biomass of the growing trees. Soil P_tot pools were in average 220 and 320 kg P ha⁻¹ in the upper and lower soil layer, respectively. It was assumed that mycorrhizal fungi present in the stands had an influence on the availability of N and P to the trees. Responsible Editor: Hans Lambers.     

The effects of ferulic acid on the mineral nutrition of grain sorghum

The combined effects of whole-tree harvesting (WTH) and soil leaching by both acid deposition and naturally-produced carbonic acid were evaluated in a mixed oak and a loblolly pine forest growing on similar soils in the Ridge and Valley province of eastern Tennessee. It was hypothesized that nutrient export via WTH would be greater in a mixed oak stand than in the loblolly pine stand because of greater nutrient concentrations in oak and hickory species than in pine. This hypothesis was true for N,P, and particularly Ca at the time of harvest, but not for K or Mg. When expressed on an annual basis, exports of N,P,K, and Mg were greater in the loblolly pine site and only Ca export was greater in the mixed oak site. It was also hypothesized that the large accumulation of Ca in the oak and hickory vegetation would cause lower exchangeable Ca²⁺ in soils, and, consequently, lower Ca²⁺ leaching in the mixed oak site than in the loblolly pine site. This hypothesis was supported by the data, which indicated 340–370% more exchangeable Ca and 100% more Ca²⁺ leaching in the loblolly pine site than in the mixed oak site. Research sponsored by the U.S. Environmental Protection Agency under Interagency Agreement No. 79-D-X0533 and Biofuels and Municipal Waste Technology Division, U.S. Department of Energy, under Contract No. De-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. Publication No. 2933, Environmental Sciences Division, ORNL.     

Litter production and forest floor nutrient dynamics in pine and hardwood stands of New Brunswick, Canada

Biomass and nutrient transfer (N, P, K, Ca, Mg) of overstory (branches and leaves) and understory litter fall were examined over a two year period in four jack pine stands aged 16, 29, 49 and 57 years and four mixed hardwood stands aged 7, 17, 20 and 29 years. Relative amounts of the five nutrients in litter fall for both series of stands were N > K ≷ Ca > P = Mg. Return of mineral elements to the forest floor was generally twice as high on the hardwood stands as for similarly aged pine stands. Overall return of nutrients plotted versus stand age generally exhibited a plateau relationship, with relatively little difference among stands; however, some exceptions occurred. Understory contribution to litter fall was very important on these stands, since in most cases the nutrient mass in understory litter was usually similar to or higher than that from the tree layer. Data on forest floor biomass, nutrient distribution and turnover rates of these stands were also presented; mobility of nutrients in the forest floor was in the order K > Mg ≥ P ≥ Ca ≥ N.     

Nutrient cycling in Pinus sylvestris stands in eastern Finland

Nutrient cycling within three Pinus sylvestris stands was studied in eastern Finland. The aim of the study was to determine annual fluxes and distribution of N, P, K, Ca, Mg, Zn, Fe, B, and Al in the research stands. Special emphasis was put on determining the importance of different fluxes, especially the internal cycle within the trees in satisfying the tree nutrient requirements for biomass production. The following nutrient fluxes were included, input; free precipitation and throughfall, output; percolation through soil profile, biological cycle; nutrient uptake from soil, retranslocation within trees, return to soil in litterfall, release by litter decomposition. The distribution of nutrients was determined in above- and belowground tree compartments, in ground and field vegetation, and in soil.The nitrogen use efficiencies were 181, 211 and 191 g of tree aboveground dry matter produced per g of N supplied by uptake and retranslocation in the sapling, pole stage and mature stands, respectively. Field vegetation was more efficient in nitrogen use than trees. Stand belowground/aboveground and fine root/coarse root biomass ratios decreased with tree age. With only slightly higher fine root biomass, almost three times more nitrogen had to be taken-up from soil for biomass production in the mature stand than in the sapling stand.The annual input-output balances of most nutrients were positive; throughfall contained more nutrients than was lost in mineral soil leachate. The sulphate flux contributed to the leaching of cations, especially magnesium, from soil in the mature stand.Retranslocation supplied 17–42% of the annual N, P and K requirements for tree aboveground biomass production. Precipitation and throughfall were important in transferring K and Mg, and also N in the sapling stand. Litterfall was an important pathway for N, Ca, Mg and micro nutrients, especially in the oldest stands.     

Global‐scale patterns of nutrient density and partitioning in forests in relation to climate

Knowledge of nutrient storage and partitioning in forests is imperative for ecosystem models and ecological theory. Whether the nutrients (N, P, K, Ca, and Mg) stored in forest biomass and their partitioning patterns vary systematically across climatic gradients remains unknown. Here, we explored the global‐scale patterns of nutrient density and partitioning using a newly compiled dataset including 372 forest stands. We found that temperature and precipitation were key factors driving the nutrients stored in living biomass of forests at global scale. The N, K, and Mg stored in living biomass tended to be greater in increasingly warm climates. The mean biomass N density was 577.0, 530.4, 513.2, and 336.7 kg/ha for tropical, subtropical, temperate, and boreal forests, respectively. Around 76% of the variation in biomass N density could be accounted by the empirical model combining biomass density, phylogeny (i.e., angiosperm, gymnosperm), and the interaction of mean annual temperature and precipitation. Climate, stand age, and biomass density significantly affected nutrients partitioning at forest community level. The fractional distribution of nutrients to roots decreased significantly with temperature, suggesting that forests in cold climates allocate greater nutrients to roots. Gymnosperm forests tended to allocate more nutrients to leaves as compared with angiosperm forests, whereas the angiosperm forests distributed more nutrients in stems. The nutrient‐based Root:Shoot ratios (R:S), averaged 0.30 for R:S_N, 0.36 for R:S_P, 0.32 for R:S_K, 0.27 for R:S_Ca, and 0.35 for R:S_Mg, respectively. The scaling exponents of the relationships describing root nutrients as a function of shoot nutrients were more than 1.0, suggesting that as nutrient allocated to shoot increases, nutrient allocated to roots increases faster than linearly with nutrient in shoot. Soil type significantly affected the total N, P, K, Ca, and Mg stored in living biomass of forests, and the Acrisols group displayed the lowest P, K, Ca, and Mg.     

Nutrient flow rates in rice roots under varying drainage conditions

Summary The relative importance of massflow and diffusion in supplying nutrients to plant roots under various drainage conditions is tested. Rice (Oryza sativa L. variety Jaya) plants were grown in field lysimeters. Transpiration, nutrient content and root length were measured along with the soil solution composition at four stages of growth. The mean inflow, apparent massflow and root demand coefficients were calculated for different nutrients.The mean inflow values of N and P were highest in continuous drainage followed by no drainage and flooding followed by 2– and 4-day drainage conditions. Inflow values of K, Ca, Mg and Na, however, were lowest in no drainage. The apparent massflow of K was lower and that of Na, Ca as well as well as Mg was higher than the corresponding inflow values. Mean solution concentration of K at the root surface decreased, but that of Ca, Mg and Na increased slightly. Root demand coefficients of K, Ca, Mg and Na were highest in continuous drainage. Under different water management practices, the values of inflow rate can be used for judging the efficiency of root.Contribution of G. B. Pant University of Agriculture and Technology, Pantnagar-263145, India.     

油茶低产林养分需求和时间配置动态变化研究

以常宁油茶低产林为研究对象,分析了油茶低产林树体各器官及土壤养分时间动态变化。结果表明:油茶低产林树体在不同生长期需求的大量元素均为全N、Ca和全K最多,而需求的Mg和全P最少;需求的微量元素均为Mn和Fe最多,Cu和Cd最少;春梢期供应的土壤养分元素是速效N和Mg,夏梢期主要供应的土壤元素是速效K、全N、全P、Fe和有机质,果实成熟期主要供应的土壤养分元素是全K,开花期主要供应的土壤元素是速效P和Ca;不同时间油茶低产林养分需求为春梢期(28.36%)夏梢期(26.17%)果实成熟期(22.75%)开花期(22.73%);土壤养分供应为夏梢期(2999.83±87.04 mg/kg)果实成熟期(2703.93±292.26 mg/kg)开花期(2554.60±508.84 mg/kg)春梢期(2385.88±199.62 mg/kg);油茶低产林在不同生长期需要的养分和土壤供应的养分并不一一对应。研究结果可为油茶低产林的施肥时间配置和养分时间变化提供科学依据,在春梢期多施肥。     

Nutrients and mass in litter and top soil of ten tropical tree plantations

The importance of litter to nutrient and organic matter storage and the possible influence of species selection on soil fertility in ten stands each consisting of a separate tree species were examined in this study. The plantations had been grown under similar conditions in an arboretum in the Luquillo Experimental Forest, Puerto Rico. The species involved were: Anthocephalus chinensis, Eucalyptus × patentinervis, E. saligna, Hernandia sonora, Hibiscus elatus, Khaya nyasica, Pinus caribaea var. hondurensis, P. elliottii var. densa, Swietenia macrophylla, and Terminalia ivorensis. After 26 yr, litter mass ranged from 5 mg ha^-1 in the H. sonora stand to 27.2 Mg ha^-1 in the P. caribaea stand. Nutrients in the litter (N, P, K, Ca, and Mg) also varied widely, but stands were ranked in different order when ranked by nutrients in the litter than then ranked according to accumulation of mass. Only E. saligna and A. chinensis stands were ranked similarly in accumulation of both nutrients and mass, and the stand of H. elatus was ranked higher with respect to nutrient accumulation than to accumulation of mass. The nutrient concentration in standing leaf litter generally increased in the order of recently fallen <old intact< fragmented. Nutrient concentration of standing leaf litter appears to increase with age and depth in the litter layer. The amount of nutrients stored in the litter compartment of these plantations was in the same order of magnitude as the quantity of available nutrients in the top 10-cm of mineral soil. Total litter mass was negatively correlated with the mass-weighted concentration of N, K, and Mg. The same relationship was found for Ca in the leaf litter and N in the fine wood litter compartments. In some stands (notably P. caribaea, P. elliottii, and E. saligna), leaf litter derived from species other than the species planted in that particular stand had higher nutrient concentration than leaf litter from the planted species. Soils of the 10 stands were classified in the same soil series and had similar texture (clay soils). However, significantly different chemical characteristics were found. Results obtained by analysis of covariance and by limiting comparisons to adjacent stands with similar soil texture, indicate that different species have had different influences on the concentration of available nutrients in soil.     

Long-term effects of drainage and hay-removal on nutrient dynamics and limitation in the Biebrza mires,Poland

To provide a reference for wetlands elsewhere we analysed soil nutrients and the vegetation of floodplains and fens in the relatively undisturbed Biebrza-valley, Poland. Additionally, by studying sites along a water-table gradient, and by comparing pairs of mown and unmown sites, we aimed with exploring long-term effects of drainage and annual hay-removal on nutrient availabilities and vegetation response. In undrained fens and floodplains, N mineralization went slowly (0–30 kg N ha⁻¹ year⁻¹) but it increased strongly with decreasing water table (up to 120 kg N ha⁻¹ year⁻¹). Soil N, P and K pools were small in the undisturbed mires. Drainage had caused a shift from fen to meadow species and the disappearance of bryophytes. Biomass of vascular plants increased with increasing N mineralization and soil P. Annual hay-removal tended to have reduced N mineralization and soil K pools, but it had increased soil P. Moreover, N concentrations in vascular plants were not affected, but P and K concentrations and therefore N:P and N:K ratios tended to be changed. Annual hay-removal had induced a shift from P to K limitation in the severely drained fen, and from P to N limitation in the floodplain. The low nutrient availabilities and productivity of the undisturbed Biebrza mires illustrate the vulnerability of such mires to eutrophication in Poland and elsewhere. In nutrient-enriched areas, hay removal may prevent productivity increase of the vegetation, but also may severely alter N:P:K stoichiometry, induce K-limitation at drained sites, and alter vegetation structure and composition.     

Internal Nutrient Translocation in Chestnut Tree Stemwood: III. Dynamics Across an Age Series of Castanea sativa (Miller)

Nutrient translocation in chestnut tree stemwood was calculatedfrom the distribution of nutrient content throughout the tissuelife-span. The dynamics of internal translocation were followedduring the crop rotation by means of an age series of five coppicedstands (2–19 years). N, P, K, Ca and Mg contents in treerings were estimated from the concentrations along a verticaland radial gradient and from the ring volume obtained usingstem ring analysis.Real nutrient translocation was calculatedstepwise between successive stages in the age series;apparenttranslocation was computed on a complete tree rotation by comparingthe initial content just after the ring was formed with themineral content in the oldest stand. There was a marked translocationof N, P, K and Ca when the rings were physiologically-activetissues. Real translocation of N, P and K (but not Ca) increasedwith stand age, obviously in parallel with the enlarged stemwoodbiomass reaching 23.2 and 20.6 kg ha^-1for K and N in the lastyears of rotation, nearly 5 kg ha^-1for Mg and about 3 kg ha^-1forCa and P. Potassium was the most mobile element since translocationreached 60% of the total amount immobilized in the stemwoodat the end of the rotation, whereas values for N, P and Mg wereapproximately 25% and 10% for calcium. Total apparent translocationreached respectively 39.2 and 32.4 kg ha^-1for K, N, approximately12 and 7 kg ha^-1for Mg and Ca and only 4.4 kg ha^-1for P. Totalapparent translocation as a percentage of total wood immobilizationwas 114% for K, 83% for Mg, 63% for P, but only 39% for N and24% for calcium. Translocation; nutrient content; stemwood; tree ring; coppice; age series; dynamics; chestnut tree; Castanea sativa Miller     

RETRACTED ARTICLE: CO<Subscript>2</Subscript> effects on plant nutrient concentration depend on plant functional group and available nitrogen: a meta-analysis

Elevated CO₂ is expected to lower plant nutrient concentrations via carbohydrate dilution and increased nutrient use efficiency. Elevated CO₂ consistently lowers plant foliar nitrogen, but there is no consensus on CO₂ effects across the range of plant nutrients. We used meta-analysis to quantify elevated CO₂ effects on leaf, stem, root, and seed concentrations of B, Ca, Cu, Fe, K, Mg, Mn, P, S, and Zn among four plant functional groups and two levels of N fertilization. CO₂ effects on plant nutrient concentration depended on the nutrient, plant group, tissue, and N status. CO₂ reduced B, Cu, Fe, and Mg, but increased Mn concentration in the leaves of N₂ fixers. Elevated CO₂ increased Cu, Fe, and Zn, but lowered Mn concentration in grass leaves. Tree leaf responses were strongly related to N status: CO₂ significantly decreased Cu, Fe, Mg, and S at high N, but only Fe at low N. Elevated CO₂ decreased Mg and Zn in crop leaves grown with high N, and Mn at low N. Nutrient concentrations in crop roots were not affected by CO₂ enrichment, but CO₂ decreased Ca, K, Mg and P in tree roots. Crop seeds had lower S under elevated CO₂. We also tested the validity of a “dilution model.” CO₂ reduced the concentration of plant nutrients 6.6% across nutrients and plant groups, but the reduction is less than expected (18.4%) from carbohydrate accumulation alone. We found that elevated CO₂ impacts plant nutrient status differently among the nutrient elements, plant functional groups, and among plant tissues. Our synthesis suggests that differences between plant groups and plant organs, N status, and differences in nutrient chemistry in soils preclude a universal hypothesis strictly related to carbohydrate dilution regarding plant nutrient response to elevated CO₂.     

Nutrient distributions and bio-cycle characteristics in both natural and artificial Pinus tabulaeformis Carr. forests in hilly loess regions

Pinus tabulaeformis Carr. forest, the dominant community in Ziwuling Mountain lying in the hilly loess region, was studied for its nutrient distributions and bio-cycle characteristics in both natural and artificial forms. The results showed that the changes in the nutrient contents for different components in the same Pinus tabulaeformis Carr. forest stood in the order of needles > branches > bark > roots > bole. The aboveground nutrient elements in needles, branches, bark bole and litterfalls stood in the order of Ca > N > K > Mg > P, but the nutrients stored in the soil stood in the order of Ca > K > Mg > N > P. The accumulated amounts of nutrients increased first and then decreased with the increased age of the forest. The nutrient amounts reached their maximum when the stand was 30 years old, and decreased greatly when it was 50 years old. The 30-year-old artificial Pinus tabulaeformis Carr. forest had the highest annual accumulated amount of nutrients, and different stands stood in the order of II > III > IV > I. Comparatively, annual accumulated nutrients in different components stood in the order of needles > branches > roots > bark > bole. It was also suggested that the amounts of nutrients annually taken in from and retained in the natural Pinus tabulaeformis Carr. forest were significantly higher than those in artificial forests. The coefficients of nutrient use in various Pinus tabulaeformis Carr. stands stood in the order of Ca > Mg > N > K > P, but the nutrient use efficiency (NUE) of the same element decreased with increased age of the forest. There were no differences in the utilization coefficient and the turnover period of nutrients in both natural and artificial matured Pinus tabulaeformis Carr. forests.