Does the Gradualness of Leaf Shedding Govern Nutrient Resorption from Senescing Leaves in Mediterranean Woody Plants?

To reveal the environmental and substrate quality effects on decomposition process and enzyme activities, litterbag experiments containing Nuphar and Carex leaves, Nuphar rhizome, and Ranunculus shoot, were carried in five-subalpine marshes in Lake Tahoe basin, USA. Alkaline phosphatase, β-glucosidase, and β-xylosidase activities were determined by a fluorogenic method using methyumbelliferyl substrates. Carex leaves, Nuphar rhizome and leaves, and Ranunculus shoots lost, respectively, 33, 67, 82 and 93% of original dry weight over 268 days. Decay rates were different among substrates but not among marshes. Nitrogen and carbon contents increased during the first 58 days and subsequently remained stable. Phosphorus content was stable during the experimental period except for a decrease in the first 16 days in Nuphar shoots. Enzyme activities in decomposing Carex and Nuphar leaves in four marshes were not significantly affected by environmental conditions. β-glucosidase and β-xylosidase activities in decomposing Carex leaves increased with time, but in other plant tissue these enzyme activities remained stable during experimental period. Enzyme activities were significantly different among decomposing substrates. Alkaline phosphatase activity was highest in Nuphar leaves (ca. 1286 μ-mole h⁻¹ g DW −1) but lower and similar in other plant tissues (ca. 100 and 10 μ-mole h −1 g DW −1, respectively). This study showed differences in decay rates and enzyme activities rely on substrate and not the environment conditions of the study area. Decomposition rates in the early stage of decomposition were related to cumulative enzyme activities.     

Nitrogen resorption in Acer platanoides and Acer saccharum: influence of light exposure and leaf pigmentation

We investigated the effects of leaf color change in the fall on photosynthetic production and nitrogen resorption. Seedlings of Acer platanoides L. and A. saccharum Marsh. were grown in a shade house for 5 months in either 21 % (intermediate light, M) or 4.9 % (low light, L) of incident irradiance. After this period, a subset of the intermediate-light grown seedlings was transferred to a high-light stress treatment (H). Gas exchange, chlorophyll fluorescence, pigments, antioxidant activity, and nitrogen (N) resorption were examined at three leaf senescence stages during September and October. Our results show that plants of both species produce more anthocyanins in the H treatment. In comparison with plants grown in the L and M treatments, plants of both species in the H treatments had lower chlorophyll, carotenoid and chlorophyll fluorescence parameters (F _v/F _m, Φ _PSII, NPQ and ETR) at the third sampling date (October 12–18), and indicating higher levels of photoinhibition in the seedlings exposed to high light. Our results imply that autumn leaf redness is inducible and closely linked to photo-oxidative stress. However, anthocyanins did not enhance antioxidant capacity in red leaves in either species, when exposed to high light. For both species, our results showed a higher N-resorption for high-light stressed plants. We also observed that the number of abscised leaves at the second sampling dates (September 10) was higher than at the third sampling dates. The intra-leaf distribution of anthocyanin, the association between anthocyanin production and the high-light environments, the retention of red leaves, the substantial physiological gain of photosynthetic activity, as well as the links between anthocyanins and increased N resorption led us to assume that one primary role of autumn anthocyanin could be to protect the photosynthetic apparatus from photo-oxidative damage as light filters rather than as antioxidant. Another major role is to extend carbon capture and help supply the energy needed for N resorption from senescing leaves in both A. saccharum and A. Platanoides during high-light stress. Nevertheless, photoprotective capacity of anthocyanins was not able to fully compensate for photoinhibitory stress as the anthocyanins are not optimally located to efficiently reduce light within the leaves.     

Foliar Nitrogen Dynamics and Nitrogen Resorption of a Sandy Shrub Salix gordejevii in Northern China

Resorption of nitrogen (N) from senescing leaves is an important conservation mechanism that allows plants to use the same N repeatedly. Seasonal variations in leaf nitrogen of mature green and senescing leaves and N resorption in Salix gordejevii Chang, a sandy shrub in northern China, were studied. Our objective was to compare N resorption of this Salix species that successfully occupy different habitats (shifting sandland, fixed sandland and lowland) with differences in soil N availability and moisture. Nitrogen concentrations in green and senescing leaves were higher in June and July. N resorption efficiency (percentage reduction of N between green and senescing leaves) was highest at shifting sandland, intermediate at fixed sandland, and lowest at lowland. There was a clear seasonal variation in N-resorption efficiency, with a lower value at the early growing season and a higher value during summer. N resorption efficiency was lower at the sites with higher soil N availability, suggesting that the efficiency of the resorption process is determined by the availability of the nutrient in the soil. Resorption from senescing leaves may play an important role in the nitrogen dynamics of sandy plants and reduce the nitrogen requirements for plant growth. We conclude that N resorption from senescing leaves in S. gordejevii was correlated to soil characteristics and higher N resorption on poor soils is a phenotypic adjustment by this species to maximize N-use at low availability.     

Leaf mass loss in wetland graminoids during senescence

Mass loss of senescing leaves is an important part of plant biomass turnover and has consequences for assessment of ecosystem productivity, ecosystem nutrient use efficiency, and plant nutrient resorption efficiency. Data, however, on mass loss are scarce, and often based on leaf area as the reference base. This leads to an underestimation of the mass loss, as leaf area itself shrinks during senescence. Furthermore, the few existing studies have almost exclusively used woody species. The purpose of the present study was twofold: i) to assess leaf mass loss during senescence in herbaceous species, with the example of five wetland graminoids and, ii) to compare two different methods of mass loss assessment (two species). Assuming that leaf length does not change during senescence, we assessed leaf mass per leaf length prior to and after senescence. We also estimated pre‐senescence leaf mass nondestructively based on leaf length, width and thickness. For Typha latifolia and Carex stricta, two species with graminoid type leaves but contrasting leaf structure, both methods delivered almost identical results. After the first assessment of leaf mass on July 7th, T. latifolia leaf mass initially increased by 13%, and then decreased to be 12% below the original mass after senescence. C. stricta leaf mass remained stable until senescence, but decreased then by 33%. In a second experiment, the mass of 100 mm pieces of leaves was measured before and after senescence. Calamagrostis canadensis, Carex rostrata and C. stricta lost 23–57% of their leaf mass during senescence, whereas Glyceria canadensis did not show any mass loss. We conclude that mass loss of senescing leaves of herbaceous plants can be considerable and should not be neglected in studies of productivity, nutrient use efficiency or nutrient resorption. For species with no shrinking leaf length during senescence, mass loss can be measured with leaf length as the base whereas for others, pre‐senescent mass can be estimated on the basis of leaf dimensions.     

Extended leaf senescence promotes carbon gain and nutrient resorption: importance of maintaining winter photosynthesis in subtropical forests

The relative advantages of being deciduous or evergreen in subtropical forests and the relationship between leaf phenology and nutrient resorption efficiency are not well understood. The most successful deciduous species (Lyonia ovalifolia) in an evergreen-dominated subtropical montane cloud forest in southwest (SW) China maintains red senescing leaves throughout much of the winter. The aim of this study was to investigate whether red senescing leaves of this species were able to assimilate carbon in winter, to infer the importance of maintaining a positive winter carbon balance in subtropical forests, and to test whether an extended leaf life span is associated with enhanced nutrient resorption and yearly carbon gain. The red senescing leaves of L. ovalifolia assimilated considerable carbon during part of the winter, resulting in a higher yearly carbon gain than co-occurring deciduous species. Its leaf N and P resorption efficiency was higher than for co-occurring non-anthocyanic deciduous species that dropped leaves in autumn, supporting the hypothesis that anthocyanin accumulation and/or extended leaf senescence help in nutrient resorption. Substantial winter carbon gain and efficient nutrient resorption may partially explain the success of L. ovalifolia versus that of the other deciduous species in this subtropical forest. The importance of maintaining a positive carbon balance for ecological success in this forest also provides indirect evidence for the dominance of evergreen species in the subtropical forests of SW China.     

Analysis of the chlorophyll catabolism pathway in leaves of an introgression senescence mutant of Lolium temulentum

Pigments, proteins and enzyme activity related to chlorophyll catabolism were analysed in senescing leaves of wild-type (WT) Lolium temulentum and compared with those of an introgression line carrying a mutant gene from stay-green (SG) Festuca pratensis. During senescence of WT leaves chlorophylls a and b were continuously catabolised to colourless products and no other derivatives were observed, whereas in SG leaves there was an accumulation of dephytylated and oxidised catabolites including chlorophyllide a, phaeophorbide a and 13(2) OH-chlorophyllide a. Dephytylated products were absent from SG leaf tissue senescing under a light-dark cycle. Retention of pigments in SG was accompanied by significant stabilisation of light harvesting chlorophyll-proteins compared with WT, but soluble proteins such as Rubisco were degraded during senescence at a similar rate in the two genotypes. The activity of phaeophorbide a oxygenase measured in SG tissue at 3d was less than 12% of that in WT tissue at the same time-point during senescence and of the same order as that in young pre-senescent WT leaves, indicating that the metabolic lesion in SG concerns a deficiency at the ring-opening step of the catabolic pathway. In senescent L. temulentum tissue two terminal chlorophyll catabolites were identified with chromatographic characteristics that suggest they may represent hitherto undescribed catabolite structures. These data are discussed in relation to current understanding of the genetic and metabolic control of chlorophyll catabolism in leaf senescence.     

Correction of leaf nutrient resorption efficiency on the mass basis

植物叶片养分重吸收效率的质量损失校正 养分重吸收是植物保持养分的关键机制，但以往多数研究未考虑叶片衰老过程中的质量损失，低估了植物的叶片养分重吸收效率(NuRE)；或只能基于文献中植物功能群水平的平均质量损失，校正所研究的不同物种的叶片NuRE，从而影响了该参数的精确性。本研究通过采集中国北方地区35种常见木本植物的绿色叶片和凋落叶片样本，测量绿色叶片和凋落叶片的质量，计算了叶片衰老过程中的质量损失，并给出了这些物种凋落叶片的质量损失校正系数(MLCF)。总体而言，植物凋落叶片的质量比成熟绿 色叶片平均损失17%，物种水平质量损失变化范围为1.3%–36.8%，功能群水平为11.7%–19.6%。相 应地，这35种木本植物的凋落叶片的MLCF值平均为0.832，变化范围为0.632–0.987。与校正前相 比，用MLCF校正后的NuRE总体上显著增加。例如，校正后氮和磷的平均NuRE皆增高约9%，即比其校正前(低估)更接近真实值；当植物NuRE较低时，这种校正作用(改善)表现得尤为明显。本研究基于物种水平的野外实测数据，报道了中国北方部分常见木本植物的MLCF参考值，研究结果将有助于更准确地计算此类植物的养分重吸收效率，提升本地区植物-土壤系统中养分流通评估的精准度。     

Simulated climate change decreases nutrient resorption from senescing leaves

Nutrient resorption is the process whereby plants recover nutrients from senescing leaves and reallocate them to storage structures or newer tissues. Elemental resorption of foliar N and P has been shown to respond to temperature and precipitation, but we know remarkably little about the influence of warming and drought on the resorption of these and other essential plant macro‐ and micronutrients, which could alter the ability of species to recycle their nutrients. We conducted a 5 year manipulative field study to simulate predicted climate change conditions and studied the effects of warming (W), rainfall reduction (RR), and their combination (W+RR) on nutrient resorption efficiency in five coexisting shrub species in a semiarid shrubland. Both mature and senesced leaves showed significant reductions in their nutrient contents and an altered stoichiometry in response to climate change conditions. Warming (W, W+RR) reduced mature leaf N, K, Ca, S, Fe, and Zn and senesced leaf N, Ca, Mg, S, Fe, and Zn contents relative to ambient temperature conditions. Warming increased mature leaf C/N ratios and decreased N/P and C/P ratios and increased senesced leaf C/N and C/P ratios. Furthermore, W and W+RR reduced nutrient resorption efficiencies for N (6.3%), K (19.8%), S (70.9%) and increased Ca and Fe accumulation in senesced leaves (440% and 35.7%, respectively) relative to the control treatment. Rainfall reduction decreased the resorption efficiencies of N (6.7%), S (51%), and Zn (46%). Reductions in nutrient resorption efficiencies with warming and/or rainfall reduction were rather uniform and consistent across species. The negative impacts of warming and rainfall reduction on foliar nutrient resorption efficiency will likely cause an impairment of plant nutrient budgets and fitness across coexisting native shrubs in this nutrient‐poor habitat, with probable implications for key ecosystem functions such as reductions in nutrient retention in vegetation, litter decomposition, and nutrient cycling rates.     

Delayed leaf senescence in ethylene-deficient ACC-oxidase antisense tomato plants: molecular and physiological analysis

To determine the role of ethylene during tomato (Lycopersicon esculentum Mill. cv. Alisa Craig) leaf senescence, transgenic ACC oxidase antisense plants were analysed. Northern analysis of wild-type plants indicated that ACC oxidase mRNA accumulation normally begins in pre-senescent green leaves but was severely reduced in the antisense plants. Although the levels of ethylene evolved by wild-type and transgenic leaves increased during the progression of senescence, levels were extremely low in transgenic leaves. Leaf senescence, as assessed by colour change from green to yellow, was clearly delayed by 10–14 days in the antisense plants when compared with wild-type plants. Northern analysis of the photosynthesis-associated genes, cab and rbcS, indicated that levels of the corresponding mRNAs were higher in transgenic leaves which were not yet senescing compared with senescing wild-type leaves of exactly the same age. Northern analysis using probes for tomato fruit ripening-related genes expressed during leaf senescence indicated that once senescence was initiated the expression pattern of these mRNAs was similar in transgenic and wild-type leaves. In the antisense plants chlorophyll levels, photosynthetic capacity and chlorophyll fluorescence were higher when compared with senescing wild-type plants of the same age. Photosynthetic capacity and the quantum efficiency of photosystem II were maintained for longer in the transformed plants at values close to those observed in wild-type leaves prior to the visible onset of senescence. These results indicate that inhibiting ACC oxidase expression and ethylene synthesis results in delayed leaf senescence, rather than inducing a stay-green phenotype. Once senescence begins, it progresses normally. Onset of senescence is not, therefore, related to a critical level of ethylene. The correlation between higher levels prior to senescence and early onset, however, suggests that ethylene experienced by the plant may be a significant contributing factor in the timing of senescence.     

Antioxidant and Pigment Composition during Autumnal Leaf Senescence in Woody Deciduous Species Differing in their Ecological Traits

Abstract: Photoprotection mechanisms have been studied during autumnal senescence in sun and shade leaves of woody plants with different ecological characteristics and senescence patterns. Three of them belonging to the same family, Betulaceae: the shade‐intolerant and early successional species (Betula alba L.), the shade‐tolerant and late successional species (Corylus avellana L.), and an N‐fixing tree with low N resorption efficiency (Alnus glutinosa L.). The other two species: a shade‐intolerant (Populus tremula L.) and a shade‐tolerant (Cornus sanguinea L.), were chosen because of their ability to accumulate anthocyanins during autumnal leaf senescence. The study of plants with different ecological strategies allowed us to establish general trends in photoprotection mechanisms during autumnal senescence, when nutrient remobilisation occurs, but also during whole leaf ontogeny. We have not found a clear relationship between shade tolerance and the level of photoprotection; the main difference between both groups of species being the presence of α‐carotene in shade leaves of shade‐tolerant species. Preceding autumn, nitrogen resorption started in mid‐summer and occurred in parallel with a slight and continuous ascorbate, chlorophyll and carotenoid degradation. However, the ascorbate pool remained highly reduced and lipid oxidation did not increase at this time. Contrasting with ascorbate, α‐tocopherol accumulated progressively in all species. Only during the last stages of senescence was chlorophyll preferentially degraded with respect to carotenoids, leading to the yellowing of leaves, except in A. glutinosa in which a large retention of chlorophyll and N took place. Senescing leaves were characterised, except in C. sanguinea, by a relative increase in the proportion of de‐epoxidised xanthophylls: zeaxanthin, antheraxanthin and lutein. The light‐induced accumulation of anthocyanins in C. sanguinea could play an additional protective role, compensating for the low retention of de‐epoxidised xanthophylls. These different strategies among deciduous species are consistent with a role for photoprotective compounds in enhancing nitrogen remobilization and storage for the next growing season.     

Drought-deciduous behavior reduces nutrient losses from temperate deciduous trees under severe drought

Nutrient resorption from senescing leaves is an important mechanism of nutrient conservation in temperate deciduous forests. Resorption, however, may be curtailed by climatic events that cause rapid leaf death, such as severe drought, which has been projected to double by the year 2100 in the eastern United States. During a record drought in the southeastern US, we studied 18 common temperate winter-deciduous trees and shrubs to understand how extreme drought affects nutrient resorption of the macronutrients N, P, K, and Ca. Four species exhibited drought-induced leaf senescence and maintained higher leaf water potentials than the remaining 14 species (here called drought-evergreen species). This strategy prevented extensive leaf desiccation during the drought and successfully averted large nutrient losses caused by leaf desiccation. These four drought-deciduous species were also able to resorb N, P, and K from drought-senesced leaves, whereas drought-evergreen species did not resorb any nutrients from leaves lost to desiccation during the drought. For Oxydendrum arboreum, the species most severely affected by the drought, our results indicate that trees lost 50% more N and P due to desiccation than would have been lost from fall senescence alone. For all drought-deciduous species, resorption of N and P in fall-senesced leaves was highly proficient, whereas resorption was incomplete for drought-evergreen species. The lower seasonal nutrient losses of drought-deciduous species may give them a competitive advantage over drought-evergreen species in the years following the drought, thereby impacting species composition in temperate deciduous forests in the future.     

Why leaves turn red in autumn. The role of anthocyanins in senescing leaves of red-osier dogwood

Why the leaves of many woody species accumulate anthocyanins prior to being shed has long puzzled biologists because it is unclear what effects anthocyanins may have on leaf function. Here, we provide evidence for red-osier dogwood (Cornus stolonifera) that anthocyanins form a pigment layer in the palisade mesophyll layer that decreases light capture by chloroplasts. Measurements of leaf absorbance demonstrated that red-senescing leaves absorbed more light of blue-green to orange wavelengths (495-644 nm) compared with yellow-senescing leaves. Using chlorophyll a fluorescence measurements, we observed that maximum photosystem II (PSII) photon yield of red-senescing leaves recovered from a high-light stress treatment, whereas yellow-senescing leaves failed to recover after 6 h of dark adaptation, which suggests photo-oxidative damage. Because no differences were observed in light response curves of effective PSII photon yield for red- and yellow-senescing leaves, differences between red- and yellow-senescing cannot be explained by differences in the capacities for photochemical and non-photochemical light energy dissipation. A role of anthocyanins as screening pigments was explored further by measuring the responses PSII photon yield to blue light, which is preferentially absorbed by anthocyanins, versus red light, which is poorly absorbed. We found that dark-adapted PSII photon yield of red-senescing leaves recovered rapidly following illumination with blue light. However, red light induced a similar, prolonged decrease in PSII photon yield in both red- and yellow-senescing leaves. We suggest that optical masking of chlorophyll by anthocyanins reduces risk of photo-oxidative damage to leaf cells as they senesce, which otherwise may lower the efficiency of nutrient retrieval from senescing autumn leaves.     

Pigment dynamics and autumn leaf senescence in a New England deciduous forest,eastern USA

The leaves of woody plants at Harvard Forest in Central Massachusetts, USA, changed color during senescence; 70% (62/89) of the woody species examined anatomically contained anthocyanins during senescence. Anthocyanins were not present in summer green leaves, and appeared primarily in the vacuoles of palisade parenchyma cells. Yellow coloration was a result of the unmasking of xanthophyll pigments in senescing chloroplasts. In nine red-senescing species, anthocyanins were not detectable in mature leaves, and were synthesized de novo in senescence, with less than 20µg cm^–2 of chlorophyll remaining. Xanthophyll concentrations declined in relation to chlorophyll to the same extent in both yellow- and red-leaved taxa. Declines in the maximum photosystemII quantum yield of leaves collected prior to dawn were only slightly less in the red-senescing species, indicating no long-term protective activity. Red-leaved species had significantly greater mass/area and lower chlorophylla/b ratios during senescence. Nitrogen tissue concentrations in mature and senescent leaves negatively correlated to anthocyanin concentrations in senescent leaves, weak evidence for more efficient nitrogen resorption in anthocyanic species. Shading retarded both chlorophyll loss and anthocyanin production in Cornus alternifolia, Acer rubrum, Acer saccharum, Quercus rubra and Viburnum alnifolium. It promoted chlorophyll loss in yellow-senescing Fagus grandifolia. A reduced red:far-red ratio did not affect this process. Anthocyanins did not increase leaf temperatures in Q.rubra and Vaccinium corymbosum on cold and sunny days. The timing of leaf-fall was remarkably constant from year to year, and the order of senescence of individual species was consistent.     

Current measures of nutrient resorption efficiency lead to a substantial underestimation of real resorption efficiency: facts and solutions

Nutrient resorption is an important process during leaf senescence, which helps plants to minimize nutrient losses. To quantify nutrient resorption, the parameter resorption efficiency is commonly used. This parameter describes the percentage of the nutrient pool withdrawn before leaf abscission. The nutrient pool is generally expressed on the basis of leaf mass or leaf area, assuming that these bases do not change during senescence. In this paper we firstly present a mathematical formula describing the effect of change in measurement basis on the difference between the real resorption efficiency (RRE) value and the measured resorption efficiency (MRE). This formula shows that even moderate senescence-related changes in a measurement basis can lead to considerable underestimation of RRE. Secondly, to estimate the general change in measurement basis we quantified leaf mass loss and leaf shrinkage during senescence from literature data. These data shows that mass loss percentages can be as high as 40%, and leaf shrinkage can be up to 20%. This level of change in basis seriously compromises the MRE when not corrected for. Using our formula and the reported average literature values of changes in leaf mass (21%) and leaf shrinkage (11%) during senescence, we calculated that the average RRE for nitrogen and phosphorous of terrestrial plants is 6% (leaf area) to 10% (leaf mass) higher than the 50%, respectively 52% as reported by Aerts (1996) . This implies that nutrient resorption from senescing leaves is even more important for nutrient retention in terrestrial plants than thought so far. We advocate that preselecting leaves and monitoring the measurement basis throughout the duration of the experiment should minimize the difference between MRE and RRE.     

Analysis of Guard Cell Viability and Action in Senescing Leaves of Nicotiana glauca (Graham), Tree Tobacco

In an attempt to determine whether low epidermal conductances to water vapor diffusion of senescing leaves were caused by internal changes in guard cells or by factors external to guard cells, stomatal behavior was examined in intact senescing and nonsenescing leaves of Nicotiana glauca (Graham), tree tobacco, grown in the field or in an environmental chamber. Conductances of senescing leaves were 5 to 10% of the maximum conductances of nonsenescing leaves of the same plant, yet guard cell duplexes isolated from epidermal peels of senescing leaves developed full turgor in the light in solutions containing KCl, and sodium cobaltinitrite staining showed that K⁺ accumulated as turgor developed. Ninety-five per cent of the guard cells isolated from senescing leaves concentrated neutral red and excluded trypan blue. Intercellular leaf CO₂ concentrations of senescing and nonsenescing leaves of chamber-grown plants were not significantly different (about 240 microliters per liter), but the potassium contents of adaxial and abaxial epidermes of senescing leaves taken from plants grown in the field were less than half those of nonsenescing leaves. We conclude that guard cells do not undergo the orderly senescence process that characteristically takes place in mesophyll tissue during whole-leaf senescence and that the reduced conductances of senescing leaves are produced by factors external to guard cells.     

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.     

江西阳际峰30种阔叶树叶片氮磷含量及再吸收效率

养分再吸收是植物养分利用的重要策略,体现了植物对养分留存、利用和适应环境的能力.为研究亚热带不同生活型(常绿与落叶)阔叶树养分含量与养分再吸收的关系,以江西阳际峰国家级自然保护区内30种阔叶树为研究对象,测定成熟和衰老叶片氮(N)和磷(P)含量,分析常绿和落叶树种叶片N和P含量及其再吸收效率差异,揭示阔叶树种叶片养分再...