How does Dryobalanops aromatica supply carbohydrate resources for reproduction in a masting year?

The effect on reproduction of the dynamics of resource allocation was studied in an emergent and masting tree species, Dryobalanops aromatica (Dipterocarpaceae), in a lowland dipterocarp forest in Sarawak, Malaysia. Girdling of the reproductive shoots (5 mm diameter) caused an increase in abortion during the flowering period, but did not affect the fruit set at the middle or final stages of seed maturation. In contrast, 50% defoliation significantly affected fruit setting, but had little effect on flowering. The total leaf area of reproductive shoots was significantly correlated with final fruit set and total fruit mass. Control of the carbohydrate supply to reproductive shoots by girdling and defoliation made no difference to fruit size, but the fruit number was highly sensitive to carbohydrate availability. Total non-structural carbohydrate (TNC) decreased during the flowering period mainly in the branch (P<0.05), but fluctuated little in any organs during fruit maturation. Leaf nitrogen and photosynthetic capacity of the reproductive shoots were not significant variables for reproduction. Our results suggest that D. aromatica uses current photosynthates in the leaves of reproductive shoots as a carbon source during fruit development, but requires stored assimilates in the branch for flowering. However, since TNC was still present in all organs even after flowering, our study also suggests that storage of carbohydrate resources might not be the decisive factor in the occurrence or frequency of flowering in this species.     

Masting in whitebark pine (Pinus albicaulis) depletes stored nutrients

? In masting trees, synchronized, heavy reproductive events are thought to deplete stored resources and to impose a replenishment period before subsequent masting. However, direct evidence of resource depletion in wild, masting trees is very rare. Here, we examined the timing and magnitude (local vs individual-level) of stored nutrient depletion after a heavy mast event in Pinus albicaulis. ? In 2005, the mast year, we compared seasonal changes in leaf and sapwood nitrogen (N) and phosphorus (P) concentrations and leaf photosynthetic rates in cone-bearing branches, branches that never produced cones, and branches with experimentally removed cones. We also compared nutrient concentrations in cone branches and branches that had never had cones between 2005 and 2006, and measured tree ring width and new shoot growth during 2005. ? During the mast year, N or P depletion occurred only in tissue fractions of reproductive branches, where photosynthetic rates were reduced. However, by the end of the following year, nutrients were depleted in all branches, indicating individual-level resource depletion. New shoot and radial growth were not affected by masting. ? We provide direct evidence that mast events in wild trees deplete stored nutrients. Our results highlight the importance of evaluating reproductive costs over time and at the individual level.     

Dynamics of internal carbon resources during masting behavior in trees

Several proximate factors of masting have been provided. Here, I focus on the role of internal factors, especially the relationship between internal carbon resources and modular structures in trees. I summarize various studies of carbon resource allocation for reproduction during masting events in terms of the proximate factors of masting and discuss the modular structure in which trees accumulate and consume carbon resources as well as the timing when internal carbon resources affect masting since trees have complex resource dynamics among organs. The resource budget model, which provides a simple mechanistic explanation of the masting mechanism, is supported by various study lines. This model assumes decreasing levels of stored photosynthate after flowering and fruiting. According to several studies, however, carbon reserves do not decrease after fruiting in species in which the modules autonomously allocate current photosynthate for fruiting. In addition, it is important to elucidate when carbon resources affect masting events because during their long developmental processes, trees pass through various stages until they produce maturing fruits to create successful masting events. To explore the mechanisms of masting in future studies, it would be important to figure out how and when candidate factors (including nutrients other than carbon) may influence the entire reproduction process, for example, using field manipulation experiments.     

Accumulation and Retranslocation of Mineral Nutrients in Developing Needles in Relation to Seasonal Growth of Young Radiata Pine Trees

The growth, accumulation and movement of mineral nutrients (nitrogen,phosphorus, potassium (calcium) and chlorophyll in needles ofyoung radiata pine trees (Pinus radiata D. Don) were examined,from bud break in spring through the following year. Retranslocationof nutrients from needles was measured and is discussed in relationto nutrient requirements for seasonal growth. During the first 4–5 months after bud break when mostneedle growth occurred, all nutrients and chlorophyll accumulatedprogressively, although the concentrations of nitrogen, phosphorusand potassium decreased. During summer, substantial amounts of phosphorus were withdrawnfrom needles less than 6 months old, regardless of positionon the tree and silvicultural practice. In young needles andunder certain environmental conditions, this led to a markedtemporary decline in concentrations, even in fertilized treeson a fertile site. However, the phosphorus content of needleswas quickly restored following autumn rains. Similar fluctuations,including nutrient withdrawal in summer, occurred for nitrogenand potassium, but these were smaller than those observed forphosphorus. Phosphorus was also withdrawn from relatively olderneedles during summer. It was estimated that on a tree basis 86, 48 and 39 per centof the phosphorus, nitrogen and potassium, respectively, insummer shoots could have come from the retranslocation of nutrientsfrom young needles formed during the preceding spring. These results highlight the importance of nutrients stored inneedles to meet the nutrient requirements for growth when environmentalfactors may not be conducive to nutrient uptake from the soil. Pinus radiata D. Don, mineral nutrition, retranslocation, phosphorus, nitrogen, seasonal effects, pine needle growth     

Nitrogen storage dynamics are affected by masting events in Fagus crenata

It is generally assumed that the production of a large crop of seeds depletes stores of resources and that these take more than 1 year to replenish; this is accepted, theoretically, as the proximate mechanism of mast seeding (resource budget model). However, direct evidence of resource depletion in masting trees is very rare. Here, we trace seasonal and inter-annual variations in nitrogen (N) concentration and estimate the N storage pool of individuals after full masting of Fagus crenata in two stands. In 2005, a full masting year, the amount of N in fruit litter represented half of the N present in mature leaves in an old stand (age 190–260 years), and was about equivalent to the amount of N in mature leaves in a younger stand (age 83–84 years). Due to this additional burden, both tissue N concentration and individual N storage decreased in 2006; this was followed by significant replenishment in 2007, although a substantial N store remained even after full masting. These results indicate that internal storage may be important and that N may be the limiting factor for fruiting. In the 4 years following full masting, the old stand experienced two moderate masting events separated by 2 years, whilst trees in the younger stand did not fruit. This different fruiting behavior may be related to different “costs of reproduction” in the full masting year 2005, thus providing more evidence that N may limit fruiting. Compared to the non-fruiting stand, individuals in the fruiting stand exhibited an additional increase in N concentrations in roots early in the 2007 growing season, suggesting additional N uptake from the soil to supply resource demand. The enhanced uptake may alleviate the N storage depletion observed in the full masting year. This study suggests that masting affects N cycle dynamics in mature Fagus crenata and N may be one factor limiting fruiting.     

Abrupt increase in phosphorus and potassium fluxes during a masting event in a Bornean tropical forest

Mechanisms by which the productivity of tropical ecosystems is limited by nutrients is a long-standing question, but little information is available on the nutrient dynamics supporting the masting phenomenon in Southeast Asian evergreen rainforests. In this study we examined the nutrient sink and potential nutrient sources of masting in a Bornean tropical forest. We investigated if nutrient flux in fine litter, tree stems, and soils changed temporally in response to intense flower and fruit production. Fifty-five litter traps were installed in a 2-ha plot at the onset of flowering (April 2010), and litter and nutrient fluxes were monitored for more than 4 years (May 2010–December 2014). Wood cores of trunks and coarse roots of abundant species (Shorea spp.) and soil samples were collected in May 2010, September 2010, and September 2011 (coinciding with peak flowering, peak fruiting, and 1 year after fruiting, respectively). The P and K fluxes in the total litter were significantly greater in the mast year (2010) than non-mast years, whereas the Mg, N, and Ca fluxes did not vary in relation to masting. In line with the nutrient fluxes, P and K concentrations in coarse roots of flowering individuals of S. multiflora decreased in September 2011. The present results suggest that tropical trees require extraordinary amounts of P and K for masting, and may retranslocate stored nutrients to meet the elevated nutrient demands for masting.     

Uptake and release of nutrients by living and decomposing Typha glauca godr. tissues at Eagle Lake,Iowa

Uptake and release of nitrogen, phosphorus, potassium, calcium, and sodium from living above-ground and below-ground tissues and from decomposing litter of Typha glauca Godr. were studied at Eagle Lake, IA, during 1976. All nutrients were accumulated rapidly by shoots in the spring. Some of the nitrogen and phosphorus came from belowground storage; but potassium, calcium, and sodium were extracted entirely from the soil. Nutrients were immobilized in shoot tissues for different periods of time. Potassium content declined as rapidly as it had accumulated, and there was no evidence of belowground storage. Nitrogen and phosphorus content also declined, though not as rapidly. Approximately 45% of the nitrogen and phosphorus lost from the shoots was translocated to the rhizomes and stored. Calcium and sodium were conserved in shoot tissues until the shoots died. In the decomposing litter, potassium and sodium content declined, phosphorus and calcium content remained relatively constant, but nitrogen content increased. Over the full year of production and decomposition, this Typha glauca stand accumulated calcium and nitrogen, maintained phosphorus levels, and lost potassium and sodium.     

An increase in canopy cover leads to masting in Quercus ilex

Masting is the intermittent and synchronous production of large crops, but its relation to tree growth remains elusive despite the ecological relevance of mast seeding. The production of huge fruit crops has been linked to the accumulation and consumption of resources as nutrients and carbohydrates, but no conclusive assessment has supported this assumption. To evaluate if masting takes place once trees’ canopies reach maximum foliage, changes in canopy cover were measured in Quercus ilex susbp. ballota stands before and after a masting event using the normalized difference vegetation index (NDVI). The results on the whole underline that masting in Q. ilex occurred once maximum levels of NDVI and canopy cover were reached. After the masting event, NDVI dropped, leaf shedding increased and trees produced shorter shoots, narrower tree rings and fewer acorns than before the masting event. These findings support our contention that an increase in canopy cover precedes masting.     

Matter-economical roles of evergreen leaves inAucuba japonica,an understory shrub in the warm-temperate region of Japan

Seasonal dynamics in nitrogen and phosphorus content were examined for each component organ ofAucuba japonica, an evergreen understory shrub in the warmtemperate region of Japan. Evergreen foliage was the largest pool for each nutrient; nitrogen and phosphorus were accumulated and stored in autumn and then redistributed in the spring. For individual leaves, such seasonal accumulations and redistributions were repeated through two or three years and then at leaf fall, an additional amount was withdrawn. Rapid growth of new shoots and flowers during spring was supported by the massive redistribution of the nutrients from the old foliage. The redistribution accounted for 85% and 65% of the total nitrogen and phosphorus input to the new shoots, respectively. Such a high ratio of redistribution resulted in a conservative nutrient economy, and must be positively related to the photosynthetic production in the ligh-limited environment.     

Breeding system and pollen limitation in the masting tree Sorbus aucuparia L. (Rosaceae) in the NW Iberian Peninsula

Mast seeding or masting is the supra-annual periodic production of a large number of seeds by long-lived plants. It has been suggested that this may be a strategy to increase pollination efficiency. Sorbus aucuparia is a masting tree typically showing rather low fruit set, though with some variation among years and populations, together with marked among-year variation in flower and fruit production. Here we report a study of the reproductive biology and insect-visitor spectrum of S. aucuparia in the NW Iberian Peninsula. Results obtained over a 4-year period indicate marked self-incompatibility, so that fruit set is strongly dependent on pollinator service. Nevertheless, fruit and seed set were not limited by pollen supply in any of the years of study, since fruit and seed set after manual cross-pollination were no higher than after natural pollination. Inflorescences were visited by diverse insect species. There was no significant correlation between fruit set and insect visit frequency. Taken together, these findings indicate that the rather low fruit and seed sets observed in this species, and the spatiotemporal variation in these parameters, must be attributed to other factors, such as abiotic resource availability. We conclude that masting in S. aucuparia is probably not a strategy for increasing pollination efficiency.     

Fruit production in three masting tree species does not rely on stored carbon reserves

Fruiting is typically considered to massively burden the seasonal carbon budget of trees. The cost of reproduction has therefore been suggested as a proximate factor explaining observed mast-fruiting patterns. Here, we used a large-scale, continuous ¹³C labeling of mature, deciduous trees in a temperate Swiss forest to investigate to what extent fruit formation in three species with masting reproduction behavior (Carpinus betulus, Fagus sylvatica, Quercus petraea) relies on the import of stored carbon reserves. Using a free-air CO₂ enrichment system, we exposed trees to ¹³C-depleted CO₂ during 8 consecutive years. By the end of this experiment, carbon reserve pools had significantly lower δ¹³C values compared to control trees. δ¹³C analysis of new biomass during the first season after termination of the CO₂ enrichment allowed us to distinguish the sources of built-in carbon (old carbon reserves vs. current assimilates). Flowers and expanding leaves carried a significant ¹³C label from old carbon stores. In contrast, fruits and vegetative infructescence tissues were exclusively produced from current, unlabeled photoassimilates in all three species, including F. sylvatica, which had a strong masting season. Analyses of δ¹³C in purified starch from xylem of fruit-bearing shoots revealed a complete turn-over of starch during the season, likely due to its usage for bud break. This study is the first to directly demonstrate that fruiting is independent from old carbon reserves in masting trees, with significant implications for mechanistic models that explain mast seeding.     

The Evolution of Fruit Tree Productivity: A Review

The Evolution of Fruit Tree Productivity: A Review. Domestication of fruit trees has received far less attention than that of annual crop plants. In particular, very little is known about the evolution of fruit tree productivity. In the wild, most tree species reach reproductive maturity after a long period of juvenility and even then, sexual reproduction appears sporadically, often in a mode of masting. Environmental constraints limit trees’ reproductive activity in their natural, wild habitats, resulting in poor, irregular productivity. Early fructification and regular, high rates of productivity have been selected by people, unconsciously and consciously. The reviewed evidence indicates an evolutionary continuum of productivity patterns among trees of wild habitats, intermediary domesticates, and the most advanced domesticates. Alternate bearing appears to represent an intermediate step in the fruit tree evolutionary pathway. The existence of a molecular, genetic mechanism that controls trees’ sexual reproduction and fruiting pattern is suggested.     

Masting uncoupling: mast seeding does not follow all mast flowering episodes in a dioecious juniper tree

Evolutionary selective forces, like predator satiation and pollination efficiency, are acknowledged to be major causes of masting (the variable, periodic and synchronic production of seeds in a population). However, a number of recent studies indicate that resources might also play an important role on shaping masting patterns. Dioecious masting species offer a privileged framework to study the role of resources on masting variation, since male and female plants often experience different reproductive costs and selective pressures. We followed masting and reproductive investment (RI) of the dioecious tree Juniperus thurifera in two populations along 10 years and studied the different response of males and females to experimentally increased water and nutrient availability in a third population. Juniperus thurifera females invested in reproduction three times more resources than males. Such disparity generated different resource‐use strategies in male and female trees. Tree‐ring growth and water use efficiency (WUE) confirmed that sexes differed in their resource investment temporal pattern, with males using current resources for reproduction and females using resources accumulated during longer periods. Watered and fertilized female trees presented significantly higher flowering reproductive investments than males and experienced an extraordinary mast‐flowering event. However, seeding RI and mast seeding were not affected by the treatment. This suggests that although resource availability affects the reproductive output of this species, there are other major forces regulating masting on J. thurifera. During 10 years, J. thurifera male and female trees presented high and low flowering years more or less synchronously. However, not all mast flowering episodes resulted in mast seeding, leading to masting uncoupling between flowering and seeding. Since flowering costs represent only 1% of females’ total reproductive investments, masting uncoupling could be a beneficial bet‐hedging strategy to maximize reproductive output in spite of unpredictable catastrophic events.     

Reproductive allocation in hermaphrodite and female plants of Sidalcea oregana SSP. spicata (Malvaceae) using four currencies

Reproductive allocation was investigated in female and hermaphrodite plants of gynodioecious Sidalcea oregana ssp. spicata. Total reproductive investment and partitioning of that investment was documented at the level of whole plants in terms of four ecologically relevant currencies: biomass, nitrogen, phosphorus, and potassium. Nutrient augmentations in the field confirmed that nutrients were limiting plant vegetative growth and propensity to flower; thus the use of these nutrients as currency was appropriate. Once the effects of plant size were removed, the sex morphs allocated similar total amounts of biomass, nitrogen, phosphorus, and potassium to reproduction, but partitioned those differentially. For any given individual size, females allocated larger proportions of their reproductive resource budgets to seeds. Hermaphrodites' reproductive investment in pollen and flowers was allocated at the expense of allocation to seeds. These data are relevant to the evolution of gynodioecy from hermaphroditism and support the hypothesis that females reallocate resources not spent on pollen to seeds.     

Seasonal Allocation and Efficiency Patterns of Biomass and Resources in the Perennial Geophyte Sparaxis grandiflora Subspecies fimbriata (Iridaceae) in Lowland Coastal Fynbos, South Africa

The seasonal allocation and efficiency of biomass and resources(starch, soluble carbohydrates, N, P, K, Ca, Mg, Na, Zn, Fe,Mn and Cu) within and between the constituent plant parts ofSparaxis grandiflora subspecies fimbriata , a deciduous, synanthousgeophyte, are described. The sequential production of roots,leaves and a new daughter corm, with fruit production phasedin during the development of the daughter corm, results in continualtransfer of resources when the plant is not dormant. The newdaughter corm serves as the major sink for the allocation ofdry matter and resources during the vegetative, reproductiveand senescent periods. The parent corm is the major source ofresources in the early stages of the vegetative period. Theamount of resources allocated to the reproductive structureswas comparatively low when compared with that allocated to vegetativeplant parts. The corms have highly flexible storage capacitiesfor a variety of nutrients, particularly the better conservednutrients such as nitrogen, phosphorus, potassium, and carbohydrates.The dynamic patterns for the majority of the resources revealedhigh allocation when metabolic activity was also highest. Efficientrecovery or recycling of important resources from senescingorgans results in a similar or greater allocation to the daughtercorm than the amount that was present in the parent corm ofthe previous growth season. This is seen as an advantage tothese plants that grow in a seasonal environment where soilsare of low nutrient status.Copyright 1994, 1999 Academic Press Dry mass, efficiency, phenophase, resource allocation, Sparaxis grandiflora, fynbos     

辽西北沙地苹果-大豆间作对土壤养分和微生物量分布的影响

为了解辽西北沙地果农间作系统中土壤养分及微生物量分布特征,选取研究区具有代表性的苹果(Malus pumila)-大豆(Glycine max)间作系统为研究对象,对间作系统0～60 cm 土层、0～300 cm水平距离范围内的土壤养分和微生物量进行了测定,并与大豆单作、苹果单作进行对比.结果表明:辽西北沙地苹果与大豆...     

The response of microbial biomass and hydrolytic enzymes to a decade of nitrogen, phosphorus, and potassium addition in a lowland tropical rain forest

Nutrient availability is widely considered to constrain primary productivity in lowland tropical forests, yet there is little comparable information for the soil microbial biomass. We assessed microbial nutrient limitation by quantifying soil microbial biomass and hydrolytic enzyme activities in a long-term nutrient addition experiment in lowland tropical rain forest in central Panama. Multiple measurements were made over an annual cycle in plots that had received a decade of nitrogen, phosphorus, potassium, and micronutrient addition. Phosphorus addition increased soil microbial carbon (13 %), nitrogen (21 %), and phosphorus (49 %), decreased phosphatase activity by ~65 % and N-acetyl β-glucosaminidase activity by 24 %, but did not affect β-glucosidase activity. In contrast, addition of nitrogen, potassium, or micronutrients did not significantly affect microbial biomass or the activity of any enzyme. Microbial nutrients and hydrolytic enzyme activities all declined markedly in the dry season, with the change in microbial biomass equivalent to or greater than the annual nutrient flux in fine litter fall. Although multiple nutrients limit tree productivity at this site, we conclude that phosphorus limits microbial biomass in this strongly-weathered lowland tropical forest soil. This finding indicates that efforts to include enzymes in biogeochemical models must account for the disproportionate microbial investment in phosphorus acquisition in strongly-weathered soils.     

Influence of Cultivation Parameters on the Mineral Composition of Kiwi Fruit from Corsica

The effect of four cultivation parameters (postmaturity harvest date, storage period at 0 °C, and input of nitrogen and potassium fertilizers) on the mineral composition of kiwi fruit (Actinidia deliciosa var. H ayward) from Corsica were evaluated. The kiwi fruit were harvested on three dates at two‐week intervals and some fruit were stored for three and four months. The kiwi fruit orchard was fertilized with controlled levels of nitrogen (five levels) and potassium (three levels) during one growing season. The concentrations of 67 elements in kiwi fruit were measured using various analytical methods, such as flow injection spectrophotometry, flame atomic absorption spectrometry, flame atomic emission spectrometry, electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, and filtration. The main elements in kiwi fruit are K, N, Cl, P, and Si and, to a lesser amount, Ca, Mg, Na, and Fe. This study demonstrates a high degree of difference in the amount of 23 mineral elements depending on the harvest date, the time of storage, and the input of fertilizers.     

Leaf traits, shoot growth and seed production in mature Fagus sylvatica trees after 8 years of CO2 enrichment

Background and Aims

Masting, i.e. synchronous but highly variable interannual seed production, is a strong sink for carbon and nutrients. It may, therefore, compete with vegetative growth. It is currently unknown whether increased atmospheric CO₂ concentrations will affect the carbon balance (or that of other nutrients) between reproduction and vegetative growth of forest species. In this study, reproduction and vegetative growth of shoots of mature beech (Fagus sylvatica) trees grown at ambient and elevated atmospheric CO₂ concentrations were quantified. It was hypothesized that within a shoot, fruiting has a negative effect on vegetative growth, and that this effect is ameliorated at increased CO₂ concentrations.

Methods

Reproduction and its competition with leaf and shoot production were examined during two masting events (in 2007 and 2009) in F. sylvatica trees that had been exposed to either ambient or elevated CO₂ concentrations (530 µmol mol⁻¹) for eight consecutive years, between 2000 and 2008.

Key Results

The number of leaves per shoot and the length of terminal shoots was smaller or shorter in the two masting years compared with the one non-masting year (2008) investigated, but they were unaffected by elevated CO₂ concentrations. The dry mass of terminal shoots was approx. 2-fold lower in the masting year (2007) than in the non-masting year in trees growing at ambient CO₂ concentrations, but this decline was not observed in trees exposed to elevated CO₂ concentrations. In both the CO₂ treatments, fruiting significantly decreased nitrogen concentration by 25 % in leaves and xylem tissue of 1- to 3-year-old branches in 2009.

Conclusions

Our findings indicate that there is competition for resources between reproduction and shoot growth. Elevated CO₂ concentrations reduced this competition, indicating effects on the balance of resource allocation between reproduction and vegetative growth in shoots with rising atmospheric CO₂ concentrations.     

Parameterisation and validation of a resource budget model for masting using spatiotemporal flowering data of individual trees

Synchronised and fluctuating reproduction by plant populations, called masting, is widespread in diverse taxonomic groups. Here, we propose a new method to explore the proximate mechanism of masting by combining spatiotemporal flowering data, biochemical analysis of resource allocation and mathematical modelling. Flowering data of 170 trees over 13 years showed the emergence of clustering with trees in a given cluster mutually synchronised in reproduction, which was successfully explained by resource budget models. Analysis of resources invested in the development of reproductive organs showed that parametric values used in the model are significantly different between nitrogen and carbon. Using a fully parameterised model, we showed that the observed flowering pattern is explained only when the interplay between nitrogen dynamics and climatic cues was considered. This result indicates that our approach successfully identified resource type‐specific roles on masting and that the method is suitable for a wide range of plant species.