Declining soil fertility does not increase leaf lifespan within species: evidence from the Franz Josef chronosequence, New Zealand

Leaf lifespan varies widely among plant species, from a few weeks to >40 years. This variation is associated with differences in plant form and function, and the distribution of species along resource gradients. Longer leaf lifespans increase the residence time of nutrients and are one mechanism by which plants conserve nutrients; consequently, leaf lifespan should increase within species with declining soil nutrient availability. The Franz Josef chronosequence is a series of post-glacial surfaces along which soil fertility declines strongly with increasing soil age. We used this fertility gradient to test whether leaf lifespans of six common indigenous woody species increased as soil nutrient availability declined. Leaf lifespan varied from 12.4 months in Coprosma foetidissima (Rubiaceae) to 47.1 months in Pseudopanax crassifolius (Araliaceae). These leaf lifespans sample 12% of the full range of leaf lifespans reported globally and occupy a relatively conservative portion of global leaf trait space. Contrary to our expectations, leaf lifespan of two species (Pseudopanax crassifolius and Prumnopitys ferruginea) decreased by 44?61% with increasing soil age and there were no other relationships between soil age and leaf lifespan. Across all species, leaf nutrient residence times increased by 85% for N and 90% for P with declining soil fertility, but this was caused by increased nutrient resorption efficiency rather than by increased leaf longevity. These data demonstrate that plants increase leaf nutrient resorption efficiency rather than leaf lifespan as a within-species response to long-term declines in soil fertility.     

Environmental constraints on phenology and internal nutrient cycling in the Mediterranean winter-deciduous shrub Amelanchier ovalis Medicus

The functional adjustments of winter-deciduous perennials to Mediterranean conditions have received little attention. The objectives of this study were: (i) to determine whether Amelanchier ovalis, a winter-deciduous shrub of Mediterranean and sub-Mediterranean regions, has nutritional and phenological traits in common with temperate zone deciduous trees and shrubs and (ii) to determine the constraints of Mediterranean environmental conditions on these traits. Over two years, phenology and nitrogen, and phosphorus concentrations were monitored monthly in the crown of A. ovalis. Leaf longevity, survival and nutrient resorption from senescing leaves were used to infer nutrient use efficiency and retention times of nutrients within the crown. In A. ovalis, bud burst was much earlier than in temperate deciduous trees and shrubs. Most vegetative and reproductive growth occurred in spring. Limited phenological development took place during the summer drought period. Unexpectedly, leaf shedding was very gradual, which might be related to water shortages in summer. Leaf longevity, nutrient resorption from senescing leaves, and maximum leaf nutrient concentrations indicated that nutrient retention times were short and nutrient use efficiency was low compared to that found in temperate deciduous plants and co-occurring Mediterranean evergreens. A. ovalis exhibited phenological development appropriate for a Mediterranean climate, although its limited ability to retain nutrients likely restricts the types of sites that it can occupy.     

The effect of increased nutrient availability on leaf turnover and aboveground productivity of two evergreen ericaceous shrubs

Summary Leaf turnover and aboveground productivity in relation to nutrient availability were studied in the evergreen shrubs Erica tetralix and Calluna vulgaris. In monospecific stands of these species four levels of nutrient (NPK) availability were created during three growing seasons. Percentage survival and life expectancy of Erica leaves decreased with increasing nutrient availability. For Calluna there was no effect. Winter mortality of Erica leaves was smaller than growing season mortality. These was no difference for Calluna. The timing of leaf mortality of both species was not affected by nutrient treatment. At the end of the experimental period current year leaf biomass, total biomass and current year second year and third year biomass of both species showed a significant increase with increasing nutrient availability. The relative increase was greater for Calluna, except for second and third year biomass. Stem production and stem mortality of both species increased with increasing nutrient availability. The increased stem mortality resulted also for Calluna in an increased leaf turnover (per unit ground area) with increasing nutrient availability. Nutrient cycling in ecosystems dominated by these species will increase with increasing nutrient availability, because of increased leaf and stem turnover and productivity. This phenotypic effect is similar to the effect of the shift in dominance between different species which occurs along natural gradients of nutrient availability.     

Foliar demand and resource economy of nutrients in dry tropical forest species

Important phenological activities in seasonally dry tropical forest species occur within the hot‐dry period when soil water is limiting, while the subsequent wet period is utilized for carbon accumulation. Leaf emergence and leaf area expansion in most of these tree species precedes the rainy season when the weather is very dry and hot and the soil cannot support nutrient uptake by the plants. The nutrient requirement for leaf expansion during the dry summer period, however, is substantial in these species. We tested the hypothesis that the nutrients withdrawn from the senescing leaves support the emergence and expansion of leaves in dry tropical woody species to a significant extent. We examined the leaf traits (with parameters such as leaf life span, leaf nutrient content and retranslocation of nutrients during senescence) in eight selected tree species in northern India. The concentrations of N, P and K declined in the senescing foliage while those of Na and Ca increased. Time series observations on foliar nutrients indicated a substantial amount of nutrient resorption before senescence and a ‘tight nutrient budgeting’. The resorbed N‐mass could potentially support 50 to 100% and 46 to 80% of the leaf growth in terms of area and weight, respectively, across the eight species studied. Corresponding values for P were 29 to 100% and 20 to 91%, for K 29 to 100% and 20 to 57%, for Na 3 to 100% and 1 to 54%, and for Ca 0 to 32% and 0 to 30%. The species differed significantly with respect to their efficiency in nutrient resorption. Such interspecific differences in leaf nutrient economy enhance the conservative utilization of soil nutrients by the dry forest community. This reflects an adaptational strategy of the species growing on seasonally dry, nutrient‐poor soils as they tend to depend more or less on efficient internal cycling and, thus, utilize the retranslocated nutrients for the production of new foliage biomass in summer when the availability of soil moisture and nutrients is severely limited.     

Significance of sequential leaf development for nutrient balance of the cotton sedge,Eriophorum vaginatum L.

Summary The sedgeEriophorum vaginatum in an interior Alaskan muskeg site produced leaves sequentially at about 1.5-month intervals. Each leaf remained active for two growing seasons. Young leaves (even those initiated late in the season) always had high concentrations of N, P, K and Mg and were low in Ca. Stems had high concentrations of nutrients, sugar, amino acid N and soluble organic P in autumn and spring but low concentrations in summer. Growth of leaves in spring was strongly supported by translocation from storage. Leaves approached their maximum nutrient pool before nutrient uptake began in late spring, one month before maximum biomass. Retranslocation of nutrients from aging leaves could support nutrient input into new, actively growing leaves as a consequence of the sequential leaf development. For instance retranslocation from aging leaves accounted for more than 90 and 85% of P and N input to new leaves appearing in early summer and 100% to leaves that appeared later. Leaching losses were negligible. Half time for decay of standing dead litter was 10 years. We suggest that sequential leaf development paired with highly efficient remobilization of nutrients from senescing leaves enables plants to recycle nutrients within the shoot and minimize dependence upon soil nutrients. This may be an important mechanism enablingEriophorum vaginatum to dominate nutrient-poor sites. This may also explain why graminoids with sequential leaf production cooccur with evergreen shrubs and dominate over forbs and deciduous shrubs in nutrient-poor sites in the boreal forest (e.g., in bogs) and at the northern limit of the tundra zone.     

The efficiency of nitrogen retranslocation from leaf biomass in Quercus ilex ecosystems

Nitrogen retranslocation from senescing leaves represents a crucial adaptation by tree species towards a more efficient use of this nutrient. As a result, this part of the nitrogen cycle has received increasing attention in recent years. However, there remain strong discrepancies with respect to the factors responsible for interspecific differences in the efficiency of this process.In the present work the seasonal pattern of leaf growth and the movement of nitrogen in leaves have been studied in a series of Quercus ilex plots with different levels of rainfall and soil quality in central-western Spain, as well as in 20 other woody species typical of this area. The percentage of nitrogen retranslocated was estimated from the difference between the maximum mass of nitrogen stored in the leaf biomass and the amount of this nutrient returned annually to the soil through leaf fall. Q. ilex appears as one of the least efficient species in the Mediterranean region in the recovery of nitrogen from senescing leaves (29.7% of the maximum pool). Furthermore, the older leaves of Q. ilex do not show the cycles of nitrogen withdrawal during new flushes of shoot growth, such as occurs in Pinus spp. This suggests that older leaves in Q. ilex do not play an important role as nitrogen storage organs.     

Variation in leaf longevity of Pistacia lentiscus and its relationship to sex and drought stress inferred from leaf δ13C

1. Leaf formation, loss, retention, longevity and biomass on male branches of the evergreen mediterranean shrub Pistacia lentiscus , L. correlated strongly with water-use efficiency inferred from leaf δ¹³C across a gradient of precipitation on the island of Mallorca, Spain.
2. The correlations suggest that the leaf phenology is under control of drought-induced constraints on the carbon balance.
3. In fruiting female branches, the correlations between the inferred water-use efficiency and number of formed and retained leaves, leaf biomass and leaf longevity were non-significant. Leaf formation was strongly reduced by fruiting and the females compensated the reduced photosynthetic capacity by retaining older leaves for a longer time than male plants.
4. It is suggested that leaf longevity in females is under strong control of resource allocation to fruit formation which is 'overlaid' on the drought-induced carbon stress, which led to the observed longer leaf longevity in females than in males.     

Soil organic matter,nutrient distribution,fungal and microbial biomass and enzyme activities in a forest beech stand on the Apennines of southern Italy

The aim of this study was to analyse the amount and qualitative characteristics of organic matter (OM) in the litter horizon (considering leaf litter at different decomposition stages) and underlying soil to a 30-cm depth in a beech stand on the Apennines in southern Italy. Distribution of major nutrients as well as fungal and microbial biomass were also evaluated, in addition to beech leaf nutrient content monitor from full expansion to abscission in order to estimate annual nutrient input to soil from litterfall and nutrient retranslocation before abscission. OM was significantly higher in leaf litter. C/N ratio and the Na, Mn, Fe levels also decreased along the decomposition continuum, whereas N and S contents slowly decreased with soil depth. Generally, leaf nutrient content was also significantly lower in dead leaves, indicating efficient retranslocation to persistent organs. Fungal biomass was the highest in leaf layers, with no significant changes between spring and autumn samplings. Enzyme activities did not differ significantly along the decomposition continuum but marked decreases were found in the upper soil layer; these remained relatively constant, with the exception of laccase, at deeper soil depths. No seasonal effect on enzyme activities and OM content was found.     

不同林龄杉木组织迁移养分的再利用

为了清楚了解不同林龄杉木(Cunninghamia lanceolata)组织迁移养分(氮、磷、钾、钙、镁)再利用特征, 为人工林丰产的经营管理提供科学依据, 该文利用湖南会同杉木林不同林龄段的活的枝叶与枯死枝叶养分浓度及其差异和枝叶枯死量, 估算枝叶枯死前的养分迁移量。用某林龄段开始和结束时的杉木器官的养分浓度差异, 估算那些在某林龄段开始前林分生产的, 在林龄段结束时仍存活的器官(干、皮、枝、叶、根), 即仍存活物质, 在该林龄段的养分迁移量。将枝叶枯死前迁移的养分和这些仍存活物质中转移的养分与从土壤中吸收的养分相结合, 根据森林生产的生物量, 综合分析森林物质生产的养分利用特征。研究表明: 1-7年生林分, 利用枝叶枯死前迁移的养分生产的生物量及占总生产生物量的比例, 分别为217 kg·hm ^-2·a ^-1和3.52%; 20-25年生林分则分别上升到2 540 kg·hm ^-2·a ^-1和17.50%。枝叶枯死前迁移的养分生产的生物量及占总生产生物量的比例都随林龄增加而增大。林分在12-16、17-20、21-25年林龄段, 由这些仍存活物质中迁移出的养分生产的生物量分别为385、561和450 kg·hm ^-2·a ^-1, 分别占总生产生物量的3.40%、3.40%和3.11%。这些仍存活物质中迁移出的养分量随林龄增加呈现先上升后下降的变化, 由这些养分生产的物质量占总生产物质量的比例随林龄增加呈下降趋势。结果显示, 只要有枝叶枯死发生, 就有枝叶枯死前迁移出养分用于物质再生产。林分郁闭后, 才会发生这些仍存活物质中迁移出的养分再利用。杉木体内养分再分配及贮备机制、杉木生长规律和不同生长发育阶段对养分的需求和利用效率等, 共同调节控制着枝叶枯死前迁移的和这些仍存活物质中迁移出的养分再利用的年变化。     

Seasonal changes in element contents in mangrove element retranslocation during leaf senescene

The concentrations of nitrogen (N), phosphorus (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg) and chlorine (Cl) were followed monthly in pre-senescence leaves and post-abscission leaves of Kandelia candel (L.) Druce at the Jiulongjiang estuary, and Fujian, China. The element retranslocation efficiency (RE) was studied during leaf senescence. The element RE's evaluated using different methods were compared and a new method was put forward to evaluate element RE during leaf senescence in evergreen trees without concentrated leaf fall. The results showed that during leaf senescence, 77.22% N, 57.53% P, and 44.51% K were translocated out of senescing leaves. Translocation of nutrients out of senescing leaves back into shoots was an important nutnent-conservation mechanism for N and P, was less important for K, and did not occur for Ca, Mg, Na, or Cl. One of the reasons for the high primary productivity of mangroves in nutrient poor sites (especially with low N) is the high nutrient use efficiency.     

Changes in nutrient use efficiency, status and retranslocation in young post-fire regeneration Pinus halepensis in response to sudden N and P input, irrigation and removal of competing vegetation

The capacity of Mediterranean species to adapt to variable nutrient supply levels in a global change context can be a key factor to predict their future capacity to compete and survive in this new scenario. We aimed to investigate the capacity of a typical Mediterranean tree species, Pinus halepensis, to respond to sudden changes in N and P supply in different environmental conditions. We conducted a fertilisation, irrigation and removal of competing vegetation experiment in a calcareous post-fire shrubland with an homogeneous young (5 years old) population of P. halepensis in order to investigate the retranslocation and nutrient status for the principal nutrients (N, P, Mg, K, S, Ca and Fe), and the nutrient use efficiency (NUE) of the most important nutrients linked to photosynthetic capacity (N, P, Mg and K). P fertilisation increased P concentration in needles, P, N, Mg and K retranslocations, and NUE calculated as biomass production per unit of nutrient lost in the litterfall. The P fertilisation was able to increase the aboveground biomasses and P concentration 3 years after P fertiliser application. Those responses to P fertilisation were enhanced by the removal of competing vegetation. The N needle and litterfall concentration decreased after P fertilisation and this effect was greater when the P fertilisation was accompanied by removal of competing vegetation. The increase of P availability decreased the P-NUE and increased the N-NUE when these variables were calculated as aboveground biomass production per unit of P present in the biomass. Both P-NUE and N-NUE increased when calculated as total aboveground production per unit of nutrient loss. The results show that it is necessary to calculate NUE on a different basis to have a wider understanding of nutrient use. The irrigation did not change the needle nutrient concentrations and the litterfall production, but it significantly changed the nutrient litterfall concentrations and total aboveground contents (especially P and K). These results show a high capacity of P. halepensis to quickly respond to a limiting nutrient such as P in the critical phases of post-fire regeneration. The increase in P availability had a positive effect on growth and P concentrations and contents in aboveground biomass, thus increasing the capacity of growth in future periods and avoiding immediate runoff losses and leachate. This capacity also strongly depends on neighbour competition.     

Site fertility and leaf nutrients of sympatric evergreen and deciduous species of Quercus in central coastal California

Leaf and soil nutrient levels interact with and may each influence the other. We hypothesize that to the extent soil fertility influences the nutritional state of trees, soil fertility should correlate with summer leaf nutrient levels, whereas to the extent that trees influence soil nutrient levels, the quality of leaf litterfall should correlate with soil fertility. We examined these correlations for five sympatric oak species (genus Quercus) in central coastal California. Soil fertility, including both nitrogen and especially phosphorus, correlated significantly with summer leaf nutrient levels. In contrast, phosphorus, but not nitrogen, in the leaf litterfall correlated positively with soil nutrients. These results suggest that soil nitrogen and phosphorus influence tree nutrient levels and that leaf phosphorus, but not leaf nitrogen, influence soil fertility under the trees. Feedback between the soil and the tree for phosphorus, but not nitrogen, is apparently significant and caused by species-specific differences in leaf quality and not by litterfall quality differences within a species. We also compared functional differences between the evergreen and deciduous oak species at our study site. There were no differences in soil nitrogen and only small differences for soil phosphorus between the phenological types. Differences in leaf nutrient concentration were much more pronounced, with the evergreen species having substantially lower levels of both nitrogen and phosphorus. Evergreen species conserved more phosphorus, but not more nitrogen, than the deciduous species, but there was no consistent relationship between retranslocation and either soil nitrogen or phosphorus. These results do not support the hypothesis that evergreenness is an adaptation to low soil fertility in this system.     

Close linkages between leaf functional traits and soil and leaf C:N:P stoichiometry under altered precipitation in a desert steppe in northwestern China

Leaf functional traits are important for characterizing plant nutrient strategies. The C:N:P stoichiometric balance in soils and plants, which could indicate types of nutrient limitation, is altered under changing precipitation patterns. However, whether such alterations affect leaf functional traits remains unclear. We conducted a three-year simulated precipitation experiment in a desert steppe in northwestern China to determine changes in leaf photosynthetic traits and nutrient conservation traits in five plant species and tested the relationships of these traits with soil and leaf C:N:P stoichiometry. The five species showed few changes in their leaf traits under drought conditions, but they adjusted these traits (especially P traits) under extremely wet conditions (50% increase in precipitation). Improved leaf photosynthetic N and P use, lowered leaf P uptake, and enhanced leaf N resorption might help Lespedeza potaninii to rely less on soil nutrients in extremely wet environments than other species do. Leaf photosynthetic traits were regulated primarily by soil and leaf C:N:P stoichiometry. Leaf nutrient conservation traits were controlled by both leaf C:N:P stoichiometry and soil properties (i.e., enzyme activity and microbial biomass), a condition especially true for P traits. The results suggest that precipitation-induced alteration in the C:N:P stoichiometric balance might have important influences on plant nutrient use strategies and even on the nutrient cycling of desert steppes.

     

The importance of nutrient source in determining the influence of retention time on phytoplankton: an explorative modelling study of a naturally well-flushed lake

Two models were used to examine the relationship between hydraulic retention time, nutrient source and total chlorophyll in a shallow lake (Bassenthwaite Lake, UK). The first model was a derivation of the Vollenweider model and the second was the phytoplankton community model, PROTECH. The adapted Vollenweider model produced two different responses to changing the retention time that were phosphorus source dependent. If the phosphorus was totally from a point source, then annual mean chlorophyll steadily declined with increasing flushing rate. However, when a diffuse source was used, the chlorophyll changed little and even increased with short retention times (retention time <40 days). The PROTECH model produced some similar responses but they were more season dependent. Winter mean chlorophyll always declined with decreasing retention time, regardless of nutrient source, but the summer mean curves were source dependent and similar to those produced by the adapted Vollenweider model. Further simulations with PROTECH using a standardized flow regime provided strong evidence as to the mechanisms behind these responses. Analysis showed that the decline in chlorophyll with decreasing retention time was the prevalent response of the PROTECH simulations due to flushing loss of both nutrients and algae. Furthermore, the curve formed an asymptote at long retention times because other factors (e.g. light) limited growth; retention times >100 days had little effect on chlorophyll. However, with a diffuse phosphorus source and short retention times, an increase in biomass was observed when the nutrient was limiting for growth. Handling editor: Luigi Naselli-Flores     

Interactive effects of soil nitrogen and water availability on leaf mass loss in a temperate steppe

Although the link between leaf mass loss and assessment of ecosystem nutrient use efficiency and plant nutrient resorption efficiency has received considerable attention in various ecosystems, there has been relatively little effort to assess plant leaf mass loss during senescence, especially for herbaceous species. We conducted experimental studies to assess leaf mass loss during senescence in five dominant herbaceous species and examined the effects of increasing nitrogen (N) and water availability on leaf mass loss of four species in a temperate steppe in northern China. We nondestructively estimated mature leaf mass based on leaf length and width. Leaf mass loss varied substantially among species, ranging from 20–50%. On average across all species, N and water addition increased leaf mass loss by 30% and 19%, respectively. N and water addition interacted to affect leaf mass loss, as water addition had a significant positive effect on leaf mass loss under enriched N conditions but showed no effect under ambient N levels. We conclude that leaf mass loss of herbaceous plants was considerable and can potentially be more pronounced with increasing N and water availability. It is notable that the responses of plant species to N and water addition were variable. We suggest that leaf mass loss during senescence should be given full consideration in assessing nutrient use and resorption efficiency in semi-arid areas.     

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.     

Determinants of some leaf characteristics of Australian mangroves

Leaf characteristics reflecting the size, lifespan (longevity), moisture content (degree of succulence) and complexity of structure of 20 mangrove species were studied over several years at 13 locations along the tropical and subtropical Australian coast. These characteristics were found to fall generally within the ranges of those for woody species from other ecosystems. With the exception of one species, it was found that leaf longevity was related inversely to leaf moisture content, increasing from nearly 6 months in more succulent species to over 2 years in less succulent species. This suggested that more succulent leaves are less complex in their structure because they have less well‐developed ability to compartmentalize salt. There was a tendency also for leaf longevity to increase in species with larger leaves. These findings were consistent with the general view for land plants that leaf longevity is greater in species that have developed tolerance to environmental stress, salt particularly in the case of mangroves. Leaf tissue in such species is more robust or complex and requires greater metabolic resources in its construction; the plant is then advantaged by retaining the tissue for longer periods. Classification of the species considered here, based on their leaf longevity, moisture content and complexity, identified phylogenetically related species groupings that reflected these leaf longevity effects.     

High nitrogen : phosphorus ratios reduce nutrient retention and second-year growth of wetland sedges

Shifts from nitrogen (N)- to phosphorus (P)-limited growth due to high N deposition may alter the functioning of wetland vegetation. This experiment tested how N vs P deficiency affects the growth and nutrient use of wetland sedges. Five wetland Carex species were grown at nine N : P supply ratios (0.6-405) with two absolute levels of N and P. Biomass and nutrient concentrations were determined after one and two growing seasons. Shoot biomass was maximal at N : P supply ratios of 15-26 after one season but 5-15 after two seasons. Photosynthesis after the first season, second-year growth, leaf longevity, and the fraction of nutrient supply retained by plants over two seasons were all negatively related to N : P supply ratios, with small effects of absolute supply. The five Carex species responded similarly to N : P ratios but differed in nutrient resorption efficiency and biomass allocation. Plants treated with high N : P ratios appeared to lose nutrients below ground. Such losses may reduce plant performance in P-limited wetlands affected by high N deposition.     

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.     

Is N‐resorption efficiency related to secondary compounds and leaf longevity in coexisting plant species of the arid Patagonian Monte,Argentina?

Leaf longevity and nutrient resorption efficiency are important strategies to conserve plant nutrients. Theory suggests a negative relationship between them and also proposes that high concentration of phenolics in long‐lived leaves may reduce nutrient resorption. In order to provide new evidence on these relationships, we explored whether N‐resorption efficiency is related to leaf longevity, secondary compounds and other leaf traits in coexisting plant species of different life forms in the arid Patagonian Monte, Argentina. We assessed N‐resorption efficiency, green leaf traits (leaf mass per area (LMA), leaf longevity and lignin, total soluble phenolics and N concentrations) and N concentration in senescent leaves of 12 species of different life forms (evergreen shrubs, deciduous shrubs and perennial grasses) with contrasting leaf traits. We found that leaf longevity was positively correlated to LMA and lignin, and negatively correlated to N concentration in green leaves. N concentrations both in green and senescent leaves were positively related. N‐resorption efficiency was not associated with the concentration of secondary compounds (total soluble phenolics and lignin) but it was negatively related to LMA and leaf longevity and positively related to N concentration in green leaves. Furthermore, leaf traits overlapped among life forms highlighting that life forms are not a good indicator of the functional properties (at least in relation to nutrient conservation) of species. In conclusion, our findings indicated that differences in N‐resorption efficiency among coexisting species were more related to N concentration in green leaves, leaf lifespan and LMA than to the presence of secondary compounds at least those assessed in our study (soluble phenolics and lignin). Accordingly, N‐resorption efficiency seems to be modulated, at least in part, by the productivity–persistence trade‐off.