Nutrient Retranslocation Research Articles

A case study of nutrient retranslocation in four deciduous tree species of West Bengal tropical forest, India

A case study of nutrient retranslocation in four deciduous tree species of West Bengal tropical forest, India

Light Quality Effect on Internal N Retranslocation in Podocarpus macrophyllus Precultured with Exponential Nutrient Loading.

Streetlamp light is inevitable in the night landscape of a city and may affect the phenology of newly planted ornamental plants, but it has rarely been fully examined. Newly transplanted ornamental plants probably suffer periodic shocks, which mainly result from the inefficient reuse of internal nutrients for new growth. Exponential nutrient loading (ENL) is well known for its ability to overcome transplant shocks by promoting retranslocation for the reuse of strengthened nutrients from internal reserves in precultured seedlings. Transplantation to urbanized lands is distinct from that of montane areas; this is mainly due to a high frequency of exposure to the artificial illumination of night lighting. It is suspected that this lighting modifies vegetative phenology and generates potential risks by increasing reliance on internal nutrient retranslocation. In this study, Podocarpus macrophyllus seedlings were cultured with ENL at low and high rates of nitrogen (N) deliveries (40 and 120 mg N seedling-1, respectively), and the high-rate treatment was identified as being able to trap seedlings within toxic states. A labeled 15N isotope was pulsed to transplanted seedlings exposed to simulated light qualities in red, green, and blue light spectra. The seedlings harvested at one month showed rare responses to the interactive spectra and preculture treatments, but most of them responded to the low-rate N preculture treatment with stronger abilities in terms of the reuse of internal N and the synthesizing of photosynthetic pigments. In conclusion, it was verified that night light enforces the effect on newly transplanted plants; the red light invoked internal N for reuse, and the blue light promoted the uptake of the current N. The internal N reserve established through preculture ENL rarely made a contribution to the night light effect, except for the enhancement of height growth in the red light. The red light spectrum was recommended for the exposure of newly transplanted seedlings due to its effect on the enhancement of the retranslocation of internal N and the induction of a steady state of uptake from the current N input.

Arbuscular mycorrhizal fungi alter plant N and P resorption of dominant species in a degraded grassland of northern China

Plant nutrient resorption is an important regulator of biogeochemical cycling and decomposition. Arbuscular mycorrhizal fungi (AMF) may influence this process by helping plants absorb nutrients, although the mechanism by which this occurs remains unclear. We examined variations in nutrient resorption over a period of 3 years in three dominant species, namely, Artemisia frigida, Potentilla acaulis, and Stipa krylovii, treated with or without fungicide in a degraded grassland in Inner Mongolia in 2017. Our results showed that AMF increased the nitrogen resorption efficiency (NRE) and phosphorus resorption efficiency (PRE) in A. frigida but decreased NRE and PRE in S. krylovii and PRE in P. acaulis. The inconsistent nutrient resorption responses of A. frigida and S. krylovii to AMF were primarily attributed to the changes in biomass in the presence of AMF, thereby changing the nutrient requirements. For P. acaulis, the reduction in PRE with AMF was because AMF-induced its N limitation, which is consistent with the relative nutrient resorption hypothesis. AMF increased internal nutrient cycling in A. frigida, which may promote its dominance in degraded grassland in Inner Mongolia, China. Moreover, AMF reduced senesced leaf N concentrations, thereby reducing the carbon (C):N ratio in senesced leaves, which may affect nutrient return to the soil. Our findings indicate that AMF substantially affect the biomass and nutrient requirements of dominant plant species, potentially leading to changes in nutrient resorption during grassland degradation, which may provide a deep insight into plant nutrient retranslocation in degraded grasslands.

Nutrient retranslocation strategies associated with dieback of Pinus species in a semiarid sandy region of Northeast China

In the semiarid sandy region of Northeast China, Mongolian pine (Pinus sylvestris var. mongolica) suffers dieback after the age of 35, while Japanese red pine (Pinus densiflora) and Chinese pine (Pinus tabuliformis) stay healthy. Foliar nutrient retranslocation reflects the nutrient conservation and utilization mechanism of plants in response to their habitats. However, the nutrient retranslocation strategies employed by three Pinus tree species to cope with nutrient limitations remain largely unknown. For this study, we investigated the seasonal variations in nitrogen (N) and phosphorus (P) concentrations of Mongolian pine, Japanese red pine, and Chinese pine plantations in terms of the green needles of all ages, senesced needles, and soil. Further, the N retranslocation efficiency (NRE), and P retranslocation efficiency (PRE), and correlations between the N:P ratios of needles and soil were analyzed. The results showed that, except for the spring NRE in 1-year-old needles of Mongolian pine, the spring NRE and PRE in 1- and 2-year-old needles of the three tree species were greater than zero. The autumn PRE was higher than zero for Mongolian pine, but lower than zero for Japanese red pine and Chinese pine. Among the three Pinus species, Mongolian pine showed greater spring PRE in 2-year-old needles, and PRE from 1- to 2-year-old needles, and from 2-year-old needles to litter. However, Japanese red pine had higher P concentrations and lower N:P ratios in senesced needles, while greater PRE was found in Chinese pine litter. Significant relationships between the N:P ratios were found in the current year and 1-year-old needles and soil in the Mongolian pine plantation, while there was an insignificant relationship between the N:P ratios of the needles and soil in the Chinese pine plantation. Thus, for Mongolian pine, the removal of P from needles in autumn, and higher P translocation from older needles under P-deficient soil may have contributed to the tree dieback. In contrast, Japanese red pine and Chinese pine stored P in their needles during autumn. Japanese red pine returned more P to the soil via litter, while Chinese pine maintained N:P homeostasis and increased P withdrawal prior to needle abscission.

Implications of Foliar Particulate Matter Deposition on the Physiology and Nutrient Allocation of Dominant Perennial Species of the Indo-Gangetic Plains.

The ramifications of different concentrations of foliar particulate matter on the physiology, nutrient stoichiometry, allocation pattern, and their corresponding re-translocation rates were investigated for evergreen (Mangifera indica and Psidium guajava), semi-evergreen (Ficus religiosa and Azadirachta indica), and deciduous (Dalbergia sissoo) tree species in a simulation experiment over an exposure period of 2 years. Physiological parameters (Pn, gs, Ci, E, and WUE), nutrient stoichiometry (C: N) in different plant parts, and their allocation pattern for five macro- (C, N, K, Mg, Ca) and five (Zn, Ni, Mn, Cu, Fe) micro-elements at two different concentrations of particulate matter (ambient and elevated) with respect to control (no particulate load) were assessed. Significant differences in nutrient concentrations and their re-translocation rates were observed between the treatments in evergreen species compared to deciduous species. The photosynthetic rate significantly declined with an increase in foliar deposition of particulate matter. Higher variations in C, N, K, Mg, and Zn levels were found compared to other elements under particulate matter stress and the ratio of C/N showed a slight decline in mature leaves except in deciduous tree species. The nutrient stoichiometry revealed that the deciduous species were more tolerant whereas the re-translocation efficiency was maximum for the semi-evergreen tree species. The nutrient allocation was found greater in foliage compared to branch in evergreen and was opposite in semi-evergreen and deciduous tree species. The element re-translocation rate indicated an inconsistent behavior in nutrient recycling under the particulate matter load depending upon the tree species. The study entrenched a critical change in nutrient re-translocation and allocation pattern under the particulate stress in different parts of the tree, suggesting a novel approach for screening the tree species for sustainable plantation and planning of urban areas.

The effect of Acacia mangium harvest residue management on productivity and soil characteristics of a subsequent Eucalyptus pellita plantation in South Sumatra, Indonesia

We report on a study of harvest residue management impacts on productivity and soil properties of Eucalyptus pellita plantation in South Sumatra. We assessed the effect of harvest residue retention and P fertilisation on stand growth, biomass and nutrient cycling of the first rotation of E. pellita after 3 previous rotations of Acacia mangium. Changes in soil properties over the E. pellita rotation were also evaluated. Retention of harvest residues combined with the application of P fertiliser yielded stem volume of 209.4 m3 ha−1 and total biomass of 132 Mg ha−1, increased stem volume by 19% and total biomass by 22% compared with complete removal of harvest residue and no P fertiliser in the end of rotation at age 6 years. Mean annual litterfall production was 8.7 Mg ha−1 y-1, and nutrient retranslocation at leaf senescence was high (N, 25–33%; P, 55–73%; K, 40–49%). In the surface soil (0–10 cm) soil organic carbon and N did not change much, while extractable P and available cations decreased over the course of the rotation. Harvest residue retention of the previous rotation of A. mangium and addition of P fertiliser resulted in earlier canopy closure, higher litterfall production in the first two years, lower nutrient retranslocation and higher nutrient return to the soil when the stand is harvested, leading to better nutrient conservation in the soil.

Spatial patterns and seasonal dynamics of foliar nutrients in 5-year-old Betula alnoides plantations

Spatial distribution and season-induced variations in foliar nutrients of tree crowns play key roles in growth, and nutrient retranslocation and resorption from leaves are important mechanisms for trees to cope with sites of diversified fertility. Seasonal dynamics and spatial patterns of foliar macronutrients (Nitrogen (N), Phosphorus (P) and Potassium (K)) as well as nutrient retranslocation and resorption in a series of crown layers were examined in 5-year-old Betula alnoides plantations using a spacing trial (2500 (2 m × 2 m, spacing), 1667 (2 m × 3 m), 1250 (2 m × 4 m), 1111 (3 m × 3 m), 833 (3 m × 4 m) and 625 (4 m × 4 m) stems·ha−1) in south China. Significant effects of planting density on foliar nutrient concentrations and nutrient retranslocation and resorption were absent during a whole seasonal cycle or in each season. Both foliar total P and K concentrations increased significantly with increasing crown depth, whereas an obvious trend was not observed for foliar total N concentration. The season with the lowest foliar nutrient concentration varied with the elements, i.e. summer (Jul) for N, winter (Jan) for P and spring (Apr) for K, whereas the highest was observed in autumn (Oct) for all these macronutrient elements. Among crown layers, differences in nutrient concentrations were much lower in the high growth seasons from October to April than those in other seasons. There were significant differences among crown layers in N and P retranslocation efficiency rather than in nutrient resorption efficiency. Significant differences were absent in both retranslocation and resorption efficiencies of K. The highest nutrient retranslocation efficiency was found in the crown layer 2–3 m above ground level for N and 3–4 m for P. The absence of considerable differences among spacing treatments and crown layers mentioned above might be due to the weak early intra-specific competition induced by planting density, soil fertility or fertilization and nutrient demands of this species. These findings could provide suggestions for implementing proper pruning treatments, improving fertilization regimes and other related forest managements for B. alnoides and even other valuable timber species in the tropical and warm sub-tropical regions.

Nitrogen addition elevated autumn phosphorus retranslocation of living needles but not resorption in a nutrient-poor Pinus sylvestris var. Mongolica plantation

Continuously increasing atmospheric nitrogen (N) deposition has aggravated phosphorus (P) limitation in many forests worldwide, but how trees change nutrient use efficiency to adapt to the aggravated P limitation induced by N deposition, and what is the role of understory vegetation in mediating the responses are largely unknown. Here, the primary nutrient use strategies, i.e., nutrient resorption during leaf senescence and seasonal nutrient retranslocation in living tree leaves, were investigated in response to 5 years of N addition (none vs. 10 g N m−2 year−1) and understory removal (understory vegetation was intact vs. removed) in a nutrient-poor Mongolian pine (Pinus sylvestris var. mongolica) plantation in semiarid northern China. Soil available P concentration was significantly decreased due to N addition, but such decrease was counteracted by the understory removal. Neither P resorption efficiency nor P proficiency was significantly affected by these treatments, with an average P and N resorption efficiency of 60% and 57%, respectively. N addition decreased P concentration by 17% but did not affect total P content in a needle of all aged classes, regardless of the understory vegetation manipulation. Furthermore, N addition significantly elevated the autumn P retranslocation of all aged living needles only when understory vegetation was intact, with an average of 55% of autumn P retranslocation, compared to an average of 15% in the other treatments. The autumn P retranslocation of Mongolian pine was positively correlated with soil available P concentration. Understory removal alone marginally decreased leaf P concentration only in the current-year needles, and significantly attenuated the spring and autumn P retranslocation. Our results highlight the importance of seasonal P retranslocation in elevating tree P use efficiency under the condition of enhanced P deficiency, and role of understory vegetation in mediating seasonal P dynamics and their responses to increasing N enrichment.

Nutrient retranslocation in Larix principis-rupprechtii Mayr relative to fertilization and irrigation

Nutrient retranslocation from senescing foliage to perennial organs is critical for nutrient conservation and a mechanism of plant adaptation to low-fertility soils. And it has been well documented for evergreen species and for deciduous broadleaf tree species. Meanwhile, subirrigation (SI) and fertilization are used to improve the production efficiency of seedlings, however, little is known about how retranslocation in deciduous conifer seedlings is affected by SI or soil fertility. We fertilized Larix principis-rupprechtii Mayr seedlings with 50, 100, and 150 mg N per seedling using SI and overhead irrigation (OI). Seedling growth and nutrient status, at both pre-senescence (T1) and post-abscission (T2) moments, and growing media electrical conductivity were measured to (1) explore relationships between foliar nutrient retranslocation and (a) growth, (b) nutrient status, and (c) media fertility, and (2) examined how these are affected by irrigation method and fertilizer rate. Fertilizer rate and irrigation method had little effect on seedling growth, with the exception of root mass, but N, P, and K concentrations increased with increasing soil fertility and both concentrations and contents were greater under SI compared to OI. Foliar N and K retranslocation was lower under SI compared to OI across all fertilizer rates, while foliar P retranslocation was lower only at the highest fertilizer rate for SI-seedlings. For OI-seedlings, retranslocation was unaffected by fertilizer rate, with average N, P, and K retranslocation efficiencies of 71%, 29%, and 55%, respectively. However, retranslocation in SI-seedlings declined as fertilizer rates increased. Foliar nutrient retranslocation directly correlated with seedling biomass accumulation over the growing season (up to T1) and inversely correlated with soil fertility, shoot biomass accumulation during hardening (from T1 to T2), and T1 nutrient concentration in roots (N, P, and K) and stems (N and K). Understanding nutrient retranslocation dynamics for deciduous woody plants informs more effective nutrient management regimes for seedling production under SI.

Changes in phosphorus concentration in needles of adult Norway spruce - nutrient re-translocation or dilution effect?

Regarding the low availability of phosphorus in soil, tree internal cycling of phosphorus through re-translocation among needles would be a good strategy for conifers to cope with soil phosphorus deficiency and to support new needles in annual growth. Therefore, the relationship between the amount of plant-available phosphorus in the soil and the differences in concentrations of phosphorus among first- and second-year needles (P-difference Ny1 − Ny2) of adult Norway spruce was examined. No significant correlation could be detected between the stocks of available phosphorus extracted using citric acid and P-difference Ny1 − Ny2, even for trees with deficient nutritional status. The temporal variations of P-difference Ny1 − Ny2 at single plots showed the same order of magnitude as the variability between plots. The typically lower concentrations of phosphorus in second-year needles result mainly from an increase in needle weight of older needles. The net phosphorus re-translocation into younger needles appears to be of minor importance.

Litterfall and Nutrient Returns in the Rainforest of Southwestern Cameroon: Some Implications for Tropical Forest Productivity

Understanding litterfall and macronutrients in the rainforest ecosystem gives baseline information on nutrient dynamics. Litterfall and macronutrients return were studied for 12 months from November 2011 to October 2012 in a 50 ha plot in the Takamanda National Park, South-western Cameroon. This study evaluates the pattern and quantity of litterfall, with implications for forest productivity. It thus assesses the macronutrient concentrations, nutrient inputs into the surface soil, nutrient retranslocation by some key tree species and some physicochemical properties of the soil in the study site. Litter traps where placed randomly in the study plot. Litter was collected every fortnight sorted and air-dried after which they were oven dried at 70°C to constant weight. Soils were sampled from three flanks at depths of 0-10cm, 10-20cm and 20-30cm. Percentage retranslocation or accumulation before leaf fall was calculated from freshly fallen litter and mature green leaf. Total annual litterfall was 5.46 t/ha/yr and this varied with the seasons. Leaf litter contributed 90.9% of total litterfall. The concentration of N and Ca was higher than other nutrient elements Mg, K, P in all litter fragments. Nitrogen had the highest total nutrient input with the following pattern N>Ca>K>Mg>P (85.36 kg/ha/yr> 56.71 kg/ha/yr> 23.1 kg/ha/yr> 17.32 kg/ha/yr> 4.27 kg/ha/yr) respectively.Pterocarpus soyauxii had the highest retranslocation percentages for all the macronutrients studied compared to Afziliabipidensis and Terminalia ivorensis. It was observed that Terminalia ivorensis could be a good nutrient recycler that could be used to improve on degraded soils. It was however observed that Ca and Mg tend to accumulate in leaf litter for all the three species.

Seasonal nutrient retranslocation in reforested Pinus halepensis Mill. stands in Southeast Spain

Retranslocation, resorption and relocation of nutrients are important adaptive mechanisms developed by plants to acquire the amount of the nutrients required for growth. They are usual mechanisms in deciduous and conifer trees that occur in Mediterranean regions where drought periods are usual. Soil factors, environmental characteristics and species factors are key drivers of nutrient retranslocation in conifers but is not well understood how soil fertility or intraspecific competition influences the process. We studied retranslocation in Pinus halepensis Mill. stands showing different site quality (differences in climate and intraspecific competition) occurring in Southeast Spain. We monitored reforested mature Aleppo pine forests in stands with differences in site quality, climate and intraspecific competition. Stands were characterised, the content of nutrients of soil and green samples (twigs and pine needles) were recorded, and seasonal nutrient retranslocation was obtained. Site characteristics were related to growth rate and nutrient content of foliage and soil. We evaluated whether the retranslocation of nutrients from older to younger foliage was related to the current-year growth rate and to the nutritional status of the plant as influenced by intraspecific competition. Foliar macronutrient concentrations and the amount of retranslocated macronutrients were seasonal, with differences related to site quality and tree density. As a general trend, nutrient concentrations increased after drought (autumn) and decreased during the growth period (spring). However, some micronutrients (mainly Na and Fe) decreased during both periods. The retranslocation pattern in Aleppo pine reinforced the hypothesis that pine adaptations to drought- and fire-prone habitats are linked to the resilience of these forest types. We developed scientific knowledge to assist decision making in adaptive forest management; e.g. fertilizer recommendations or reforestation programmes.

Rubber Trees Demonstrate a Clear Retranslocation Under Seasonal Drought and Cold Stresses.

Having been introduced to the northern edge of Asian tropics, the rubber tree (Hevea brasiliensis) has become deciduous in this climate with seasonal drought and cold stresses. To determine its internal nutrient strategy during leaf senescence and deciduous periods, we investigated mature leaf and senescent leaf nutrients, water-soluble soil nutrients and characteristics of soil microbiota in nine different ages of monoculture rubber plantations. Rubber trees demonstrate complicated retranslocation of N, P, and K during foliar turnover. Approximately 50.26% of leaf nutrients and 21.47% of soil nutrients were redistributed to the rubber tree body during the leaf senescence and withering stages. However, no significant changes in the structure- or function-related properties of soil microbes were detected. These nutrient retranslocation strategy may be important stress responses. In the nutrient retranslocation process, soil plays a dual role as nutrient supplier and nutrient “bank.” Soil received the nutrients from abscised leaves, and also supplied nutrients to trees in the non-growth stage. Nutrient absorption and accumulation began before the leaves started to wither and fall.

Nutrient cycling over five years of mixed-species plantations of Eucalyptus and Acacia on a sandy tropical soil

Mixed-species plantations have the potential to enhance nutrient cycling and increase the overall biomass of the stand. In this study, we evaluate the dynamics of nutrient accumulation and exports in mixed-species plantations of Eucalyptus urograndis (Eucalyptus urophylla S. T. Blake×Eucalyptus grandis W. Hill ex Maiden) and Acacia mangium Willd. after five years of rotation. Monocultures of Eucalyptus urograndis, with or without nitrogen fertilization (120kgNha−1) (E100 and E100+N, respectively), and of Acacia mangium (A100) were established in a randomized block experimental design. Two arrangements with these species in mixed stands were also established: one with 50% of the stand density composed by each species (E50A50; 1,111 treesha−1), and one high-density system, containing double the population of each species (E100A100; 2,222treesha−1). Aboveground biomass and litter nutrient contents, nutrient retranslocation from leaves, and nutrient export through wood harvesting were measured over a full rotation. Eucalyptus in E50A50, despite having half of the population of trees (555treesha−1), accumulated the same amount of nutrients in total aboveground biomass in relation to E100, suggesting a lower nutrient limitation to the growth of Eucalyptus in this mixed stand. Conversely, Eucalyptus in E100A100 did not accumulate proportionally larger amounts of nutrients in relation to E50A50, possibly due to intra- and interspecific competition in this high-density arrangement. The deposition of N and K via litter was higher in mixed-species stands than in Eucalyptus monocultures. Also, P, Ca and Mg depositions were higher in mixed-species stands than Acacia monocultures. These results suggest higher nutrient cycling and availability in the mixtures, especially after 30months. The retranslocation of N in Eucalyptus and Acacia leaves decreased with age. At 60months, Eucalyptus trees in E100A100 retranslocated less N than the trees in E100, probably reflecting the higher availability of soil N in relation to E100. At this same age, the Eucalyptus trees planted in E50A50 exported less N, P, K and Mg in relation to E100. However, at stand level, mixtures exported more N due to the enrichment of this nutrient in the soil promoted by Acacia. This study shows the importance of introducing Acacia in Eucalyptus plantations to promote a positive balance of nutrients for subsequent rotations and additional ecological benefits to the ecosystem due to N2-fixation from Acacia trees.

Nutrient retranslocation from the fine roots of Fraxinus mandshurica and Larix olgensis in northeastern China

Nutrient retranslocation in trees is important in nutrient budgets and energy flows in forest ecosystems. We investigated nutrient retranslocation in the fine roots of a Manchurian Ash (Fraxinus mandshurica) and a Larch (Larix olgensis) plantation in northeastern China. Nutrient retranslocation in the fine roots was investigated using three methods, specifically, nutrient concentration, the ratio of Ca to other elements (Ca/other elements ratio) and nutrient content. The method based on nutrient content proved most suitable when investigating nutrient retranslocation from fine roots of the two species. The nutrient-content-based method showed that there were retranslocations of N, P, K and Mg from the fine roots of Manchurian Ash, with retranslocation efficiencies of 13, 25, 65, and 38 %, respectively, whereas there were no Ca retranslocations. There were retranslocations of N, P, K, Ca and Mg from the fine roots of Larch, with retranslocation efficiencies of 31, 40, 52, 23 and 25 %, respectively.

<b>Nutrient retranslocation in forest species in the Brazilian Amazon

Internal retranslocation is an important mechanism for nutrient conservation in plants, which depends on different factors. However, there are little data about this subject, especially on tropical forest species. This study aimed to evaluate the macronutrient retranslocation dynamic and the influence of ecological (P: pioneer x NP: non-pioneer) and phenological (ND: non-deciduous x D: semideciduous / deciduous) characteristics on the macronutrient content of leaves of five tree species on monospecific plantations in the Brazilian Amazon: Acacia mangium Willd., Parkia decussata Ducke, Dipteryx odorata (Aublet) Willd., Jacaranda copaia (Aubl.) D. Don and Swietenia macrophylla King. Photosynthetically active green leaves and senescent leaves (leaf litter) were collected. Retranslocation was estimated through an equation proposed by Attiwill, Guthrie and Leuning (1978). The pioneer species presented higher foliar contents of N; the non-pioneer species presented higher contents of K, Ca and S; and the results were inconclusive for P and Mg. The deciduous species presented higher foliar contents of K and of P, whereas the foliar contents of N, Ca, Mg and S were virtually identical between the phenological groups. The internal retranslocation of foliar nutrients in pioneer and non-deciduous species was higher than that of non-pioneer and deciduous species.

Litter decomposition and nutrient cycling in temperate forest of Kumaun region

Background & Aim: The magnitude of litter fall and its decomposition in a forest ecosystem impart a crucial role innutrient supply to plant as well as microorganisms. The present study was conducted to evaluate and compare thelitter fall production, leaves litter decomposition and nutrient re-translocation among the dominant species i.e. Pineand Oak, of temperate forest of Kumaun region. Results: The estimated annual litter fall production was significantly23% higher in Pine stand than Oak stand. The maximum portion of litter fall was occurred in summer and dry periodbetween April-June. The nutrients concentration was higher in green leaves than leaves litter. Additionally, thenutrients concentration was found to be high in green leaves as well as in leaves litter of Oak species. Thedecomposition rate of leaves litter was found to high in Oak floor which is inversely proportional to the C/N ratio.The nutrient immobilization for all the nutrients was found to be high in Pine stand. The nutrient re-translocationpercentage were in the order of P > K > N > Ca, in both the species that indicates the higher immobilization ofphosphorous and potassium in the region. Soil status is also responsible for litter decomposition. The soil MBC,MBN, MBP, basal respiration and enzymes activity were higher in Oak stand which is directly correlated with thedecomposition rate. Conclusions: Our results suggested that different plant species growing in same climaticcondition differed in litter fall, litter decomposition and have different level of nutrients uptake and availability

Warming and drought differentially influence the production and resorption of elemental and metabolic nitrogen pools in Quercus rubra.

The process of nutrient retranslocation from plant leaves during senescence subsequently affects both plant growth and soil nutrient cycling; changes in either of these could potentially feed back to climate change. Although elemental nutrient resorption has been shown to respond modestly to temperature and precipitation, we know remarkably little about the influence of increasing intensities of drought and warming on the resorption of different classes of plant metabolites. We studied the effect of warming and altered precipitation on the production and resorption of metabolites in Quercus rubra. The combination of warming and drought produced a higher abundance of compounds that can help to mitigate climatic stress by functioning as osmoregulators and antioxidants, including important intermediaries of the tricarboxylic acid (TCA) cycle, amino acids including proline and citrulline, and polyamines such as putrescine. Resorption efficiencies (REs) of extractable metabolites surprisingly had opposite responses to drought and warming; drought treatments generally increased RE of metabolites compared to ambient and wet treatments, while warming decreased RE. However, RE of total N differed markedly from that of extractable metabolites such as amino acids; for instance, droughted plants resorbed a smaller fraction of elemental N from their leaves than plants exposed to the ambient control. In contrast, plants in drought treatment resorbed amino acids more efficiently (>90%) than those in ambient (65-77%) or wet (42-58%) treatments. Across the climate treatments, the RE of elemental N correlated negatively with tissue tannin concentration, indicating that polyphenols produced in leaves under climatic stress could interfere with N resorption. Thus, senesced leaves from drier conditions might have a lower nutritive value to soil heterotrophs during the initial stages of litter decomposition despite a higher elemental N content of these tissues. Our results suggest that N resorption may be controlled not only by plant demand, but also by climatic influences on the production and resorption of plant metabolites. As climate-carbon models incorporate increasingly sophisticated nutrient cycles, these results highlight the need to adequately understand plant physiological responses to climatic variables.

Phosphorus conservation during post‐fire regeneration in a Chilean temperate rainforest

AbstractNitrogen and phosphorus are the main elements limiting net primary production in terrestrial ecosystems. When growing in nutrient‐poor soils, plants develop physiological mechanisms to conserve nutrients, such as reabsorbing elements from senescing foliage (i.e. nutrient retranslocation). We investigated the changes in soil N and P in post‐fire succession in temperate rainforests of southern Chile. In this area, forest recovery often leads to spatially scattered, discrete regeneration with patches varying in age, area, species richness and tree cover, representing different degrees of recovery from disturbance. We hypothesized that soil nutrient concentrations should differ among tree regenerating patches depending on the progress of forest regeneration and that nutrient resorption should increase over time as colonizing trees respond to limited soil nutrients. To evaluate these hypotheses, we sampled 40 regeneration patches in an area of 5 ha, spanning a broad range of vegetation complexity, and collected soil, tree foliage and litter samples to determine N and P concentrations. Nutrient concentrations in leaf litter were interpreted as nutrient resorption proficiency. We found that soil P was negatively correlated with all the indicators of successional progress, whereas total soil N was independent of the successional progress. Foliar N and P were unrelated to soil nutrient concentrations; however, litter N was negatively related to soil N, and litter P was positively related with soil P. Finally, foliar N:P ratios ranged from 16 to 25, which suggests that P limitation can hamper post‐fire regeneration. We provide evidence that after human‐induced fires, succession in temperate forests of Chile can become nutrient limited and that high nutrient retranslocation is a key nutrient conservation strategy for regenerating tree communities.

Macrophyte root and rhizome decay: the impact of nutrient enrichment and the use of live versus dead tissue in decomposition studies

The decomposition of roots and rhizomes of two macrophytes, Eleocharis cellulosa and Typha domingensis, was studied in oligotrophic phosphorus (P) limited marshes of northern Belize. The experiment was conducted in long-term control and P enriched plots in five limestone-based inland marshes. Decomposition of naturally senescent root and rhizome litter was studied over 9 months using litterbags. Belowground litter was acquired by growing plants in unenriched (control) or P enriched marsh soils for 5 months. Plants were then allowed to naturally senesce using a split root design, which promoted nutrient retranslocation. The resulting senescent litter had 30 % higher C:P and 40 % lower P content than living roots and rhizomes. There were no differences in C:N among treatments or senescent versus live litter. Litterbags, filled with control or enriched root and rhizome litter, were buried in the upper 10–14 cm soil in the corresponding plot of each marsh. Differences in the rate of decay between species were greatest for rhizome tissue, with Typha decaying more than twice as fast as Eleocharis. For both species, however, tissue P enrichment had no effect on coarse root and rhizome decay. Enhanced root production from P enrichment, coupled with no change in decay, should lead to enhanced accretion over time. Additional tests, using litterbags filled with living roots and rhizomes, yielded dramatically different results between treatments compared to senescent tissue. Results from senescent belowground tissue also differed from shoot decomposition. Caution should be exercised when inferring belowground decomposition from live tissue and aboveground rates of decay.