Seasonal Partitioning Research Articles

Seasonal Partitioning of Nitrogen by Plants and Soil Microorganisms in an Alpine Ecosystem

Seasonal Partitioning of Nitrogen by Plants and Soil Microorganisms in an Alpine Ecosystem

Technical note: Techniques to obtain improved predictions of global radiation from sunshine duration

Data for 42 stations in different parts of the world in the northern hemisphere have been employed to partition monthly averaged daily global radiation H̄ and sunshine duration n̄ in a bid to obtain improved fits to Angstroms correlation. It has been found that regression fits to the correlation using data for biannual groups of months from March–August (months 3–8) and September–February (months 9–2), or March–September (months 3–9) and October–February (months 10–2), give an improvement in the rms error over the year, which is 25% or higher than the errors for annual fits for half of the cases. In no case is there an increase in rms error from the partitioning. It is found that biannual regression parameters for a pyranometer station may be used to predict with good accuracy global radiation for locations hundreds of kilometers away from the station if the climate, altitude and latitude are similar. A use of the seasonal partitioning of data leads to the following relations with station independent coefficients for n̄⧸N̄

Seasonal variation and partition of trace metals (Fe, Zn, Cu, Mn, Cr, Cd and Pb) in surface sediments: relationship with physico-chemical variables of water from the Calabar River, South Eastern Nigeria

The seasonal variation and partition of trace metals (Fe, Cu, Zn, Mn, Cd, Cr and Pb) in the surface sediments of the Calabar River are reported. Chemical partition of the metals in the sediments reveals that 2–30% of the total metal load was contributed by the non-detrital (acid-soluble) fraction, while fine-grained host minerals/compounds are the main carriers of the detrital (acid-insoluble) fraction (70–98%). Using multivariate statistical analysis, the seasonal fluctuations in the distribution of some of the metals show significant influence by physio-chemical changes (dissolved oxygen, pH, salinity and conductivity) in the water column. Fe–Mn oxide grain coatings and sulphide materials have been identified as scavengers of some of the non-detrital and detrital trace metals in the sediments. On the basis of index of geoaccumulation (I-geo) and comparison with previous studies, the Calabar River surface sediments have been classified as unpolluted.

Partitioning of seasonal evapotranspiration from a commercial furrow-irrigated Sultana vineyard

Seasonal partitioning of evapotranspiration (ET) between transpiration by grapevines (Vitis vinifera) (T gp) and by cover crops of a ryegrass/clover mixture (T cc), and soil evaporation (E s) was performed for a furrow-irrigated vineyard during the 1994/1995 and 1995/1996 growing seasons in south-eastern Australia. ET, determined with a water balance approach, averaged 622 mm. The ET rate averaged over the two seasons increased from 2 mm day–1 in spring (September to November), when it was dominated by T cc, to peak rates of around 5 mm d–1 in summer (December to February) when it was dominated by E s. T gp, determined with either heat-pulse sensors or the Penman-Monteith equation, attained peak rates of 0.75 and 0.98 mm d–1, or 6.2 and 8.1 l vine–1 day–1 in the first and second seasons, respectively. Total seasonal T gp of 109.1 mm (900 l vine–1) in 1994/1995 and 118.8 mm (980 l vine–1) in 1995/1996 constituted just 18 – 19% of total ET. T cc totalled 214 mm (34% of ET) in the first season, when pasture cover was sparse and present for 5 months of the growing season (September to February), and 196 mm (30% of ET) in the second season when pasture cover was heavy but present for only 3 months (September to November). E s averaged 49% of total ET over both seasons. At least 30% of water used for ET was contributed by antecedent soil water in both seasons. The crop factor (K c) was largely constant throughout the season with an average value of 0.48. The depletion pattern of soil water indicated that the vine explored the soil profile well beyond 1.0 mm depth and almost evenly up to a distance of 1.5 m from the trunk. Water use efficiencies for fresh fruit yield (WUE), i. e., the ratio of fruit weight to total water use at harvest,were 13.3 and 40.5 kg ha–1 mm–1 when based on ET in 1994/1995 and 1995/1996, respectively, and 84.0 and 211.1 kg ha–1 mm–1, respectively, when based on T gp. The T gp data were used to verify three models of vine transpiration developed in an earlier study. Models based on the green area index or on fraction of incident radiation intercepted by the vine canopy produced good agreement with T gp. The model based on canopy resistance performed poorly, indicating the difficulty of extrapolating the stomatal response to environmental variables from one set of experimental conditions to another.

Rootstock Influences Seasonal Dry Matter and Carbohydrate Content and Partitioning in Above-ground Components of `Flordaprince' Peach Trees

Seasonal development of leaf area, leaf area index (LAI), dry matter, and carbohydrate content were measured from harvest 1992 to harvest 1993 in above-ground components of `Flordaprince' peach [Prunus persica (L.) Batsch] trees grafted on GF 677 (Prunus persica × Prunus amygdalus) and MrS 2/5 (Prunus cerasifera free pollinated) rootstocks, which widely differ in vigor. Whole trees were separated into fruit, leaves, shoots, 1-year-old wood and >1-year-old wood. Sampling dates were coincident with key fruit and tree developmental stages: dormancy, fruit set, pit hardening, and fruit harvest. Rootstock modified the vegetative vigor of the tree, the seasonal partitioning of dry matter, and starch content in above-ground components. Leaf area, LAI, and total above-ground dry matter were twice as high in the most vigorous combination (`Flordaprince'/GF 677), which gave the highest yield, but had the lowest harvest index. Rootstock vigor did not affect soluble sugar concentration in any of the canopy components. Starch content was greatest during dormancy and in the oldest wood of GF 677 trees. During fruit development, starch content rapidly decreased in 1-year-old wood and perennial components; at pit hardening it was four times greater in MrS 2/5 than in GF 677 trees. The vegetative-to-fruit dry mass ratio by pit hardening was 3:1 for MrS 2/5 and 9:1 for GF 677 trees. Competition with shoot growth apparently reduced fruit growth, particularly during Stage I and Stage II, as fruit size at harvest was significantly lower (17%) in GF 677 than in MrS 2/5 trees.

Effect of N supply upon the seasonal partitioning of N and P uptake in young Sitka spruce (Piceasitchensis)

Seasonal relationships between N supply, tree growth, and partitioning of both N and P have been studied in young trees using 15N and 32P isotopes. Three-year-old clonal cuttings of Sitka spruce (Piceasitchensis (Bong.) Carr.) were grown for 2 years in sand irrigated with a nutrient solution containing either 1.0 mol N•m−3 (low N) or 6.0 mol N•m−3 (high N). In the first year, trees received 2-week pulses of 15N and 32P to label current nutrient uptake during either a period of rapid spring growth or shortly after bud set in summer. In the second year, trees that had been preconditioned to a low-N supply received 3-week pulses of 15N at either the low rate of application or at the high rate to simulate a single application of N fertilizer. In spring of the first year, N treatment had no effect upon tree growth. Low-N trees increased the partition of 15N uptake to roots, but the partition of 32P was not affected by N supply and was similar to the partition of 15N in the high-N treatment. At the time of the later pulse, however, growth was affected by N supply and 32P partitioning to roots increased to match the partition of 15N in the low-N treatment. During the second year, the additional 15N given to Low-N trees to simulate fertilizer application was partitioned predominantly to current shoots and roots. Results are discussed in relation to the processes of internal cycling and the partition of nutrients taken up by larger trees.

Seasonal Partitioning of Evaporation Between Trees and Understorey in a Widely Spaced Pinus radiata Stand

Tree transpiration, E t , and understorey evaporation, E u , were measured hourly on 2-3 fine days during 12 periods throughout a year in a Pinus radiata plantation. There were 450 stems ha −1 and 60% of the herbaceous understorey vegetation and forest floor was covered by dead stems, branches and foliage from earlier thinning and pruning operations. Annual rainfall was 1154 mm and the trees and understorey vegetation were supplied adequately with water throughout the year. When stomatal conductance, g s , was normalized to a maximum value, g max , for each shoot, 87% of the variability was attributable to air saturation deficit above the forest canopy, D, and incident quantum flux density, Q

Comparative habitat selection by muskoxen introduced to northeastern Alaska and the Taimyr Peninsula, Russia

Muskoxen (Ovibos moschatus) introduced to formerly occupied areas in northeastern Alaska (70°N) in 1969 and 1970, and the Taimyr Peninsula (75°N) in 1974 and 1975 increased in number (exceeding 20%/year in the early years following their establishment), and have expaned into available habitats. Vegetation of the two areas share many similarities, although richness of vascular plant species is greater in Alaska (350) than in the Taimyr (230). Seasonal partitioning of range use is similar in both areas with low-lying tussock tundra being used primarily from summer through early to mid-winter. By late winter, when snow accumulation in low areas and on lower slopes of hills limits access to forage, muskoxen concentrate activity on drier ridge tops and river and coastal bluffs with little snow accumulation. Riparian habitats appear to receive greater year round use in Alaska than in the Taimyr.

Egg production of Eurytemora affinis—Effect of k-strategy

The number of eggs found in egg sacs of Eurytemora affinis in the Schlei, a mesohaline fjord in the Western Baltic, was determined between January and August, and female prosome length measured. Prosome length at 25°C was only half that at 0°C and was significantly correlated with mean temperature during development. Clutch size increased from lower winter values to a maximum in April and thereafter sharply decreased to a minimum at the end of July. The correlation between clutch size and body size was stronger than that between clutch size and temperature at collection. From calculations using regressions of body size and clutch size with temperature, a curve was derived for female fecundity at satiating food levels with a minimum at 12°C and increased values at both lower and higher temperatures. Depending on the length-weight conversion applied, P/B for egg production was 0·01 to 0·02 day−1 in winter and 0·43 to 0·51 day−1 at the temperature maximum in summer. Reproductive production is similar to somatic production of larval stages at low temperatures, but increases faster with increasing temperatures. The considerably smaller fecundity and weight specific egg production rate of E. affinis may be the reason why it is outnumbered by Acartia tonsa in the summer in many locations. Seasonal partitioning of the biotope by the two species is maintained by k-strategy at lower temperatures with E. affinis carrying few large eggs, and r-strategy in summer with A. tonsa depositing many small eggs.

Seasonal Partitioning of Leaf and Fruit Potassium and Fruit Dry Matter in French Prune Trees at Various Potassium Levels

A study was undertaken to determine the seasonal dynamics of leaf and fruit K content and the influence of tree K status and fruit growth on leaf and fruit K accumulation rates in French prune (Prunus domestics L. cv. d'Agen). Mature trees in a commercial orchard were treated with various rates of K2 SO4. (O to ≈20 kg/tree) in the fall. Fruit dry weight yield per tree at harvest and fruit K content were higher for high-K trees, but fruit percent K (by dry weight) was ≈1.0% for all trees. Leaf scorch and subsequent abscission severely reduced the canopy of K-deficient trees. Significant positive linear relationships between leaf and fruit K accumulation rates existed for the periods of 28 Apr.-28 May (May) and 28 May-7 July (June). A significant negative linear relationship existed between these two criteria from 7 July-3 Aug. (July). May (0.237 mg K per fruit-day) and July (0.267 mg K per fruit-day) mean fruit K accumulation rates were similar, but both were significantly higher (P = 0.001) than those for June (0.140 mg K per fruit-day). Mean leaf K accumulation rates for May (- 0.007 mg K per leaf-day) and July (-0.010 mg K per leaf-day) were similar, but both were significantly (P = 0.001) less than for June (0.005 mg K per leaf-day). Potassium per fruit accumulation was highest in trees with highest K status. Periods of net leaf K efflux and influx did not precisely correlate with fruit growth stages measured by fruit dry weight. The period of lowest fruit K accumulation (28 May-7 July) coincided with the period of maximum dry matter accumulation by the kernel. After 7 July, all increases in fruit dry weight and K content were due to mesocarp growth.

Enzymes of Nitrogen Assimilation Undergo Seasonal Fluctuations in the Roots of the Persistent Weedy Perennial Cichorium intybus

Chicory (Cichorium intybus), a deep rooted weed, grows in regions with temperate climates. Seasonal partitioning of compounds between the root and shoot results in fluctuations in the soluble carbohydrate, nitrate, amino acid, and protein pools within the roots. The activities of nitrate reductase (NR) (EC 1.6.6.1), glutamine synthetase (EC 6.3.1.2), NADH (EC 1.4.1.14), ferrodoxin glutamate synthase (EC 1.4.7.1), and glutamate dehydrogenase (GDH) (EC 1.4.1.2-4) vary throughout the year and coincide with seasonal alterations in nitrate, fructose, and sucrose. During the winter, NR, glutamine synthetase and ferrodoxin glutamate synthase activities increase in the root, while GDH displays the opposite trend with elevated activity in the summer months. All of these enzymes exhibit seasonal alterations in abundance as detected by Western blot analysis, increasing during the winter and, therefore, contributing to the seasonally dynamic protein pool. Extensive fluctuations in abundance and activity of these enzymes in the root occur during the spring and fall and coincide with shoot growth and senescence, respectively. Several observations indicate that posttranslational modifications of NR and GDH are taking place throughout the year; for example, NR is particularly unstable during the spring and fall, and seasonal GDH activity does not correlate with protein abundance.

Seasonal Patterns of Planktonic Production in McMurdo Sound, Antarctica

The prolonged periods of continuous darkness and light in polar regions have resulted in a unique seasonal partitioning of primary and heterotrophic production. In McMurdo Sound for example, the biomass, size distribution and production by phytoplankton and bacterioplankton undergo distinct seasonal cycles. The seasonal pattern of primary production appeared to be regulated by light whereas the three order of magnitude change in phytoplankton biomass during mid- to late December was largely controlled by the advection of planktonic algae from the Ross Sea into McMurdo Sound. The size distribution of phytoplankton was highly seasonal; nano- and picoplankton were dominant from August through November while netplankton were more abundant in December and January. Seasonal variations of bacterial biomass and production were smaller than those of phytoplankton. During the late austral winter and spring, bacterial biomass and production exceeded those of phytoplankton. This implies that during this period, organic material from allochthonous sources sustained bacterial growth. During the late spring and summer, however, the pattern was reversed and autochthonous primary production was sufficient to support concurrent bacterioplankton production. The apparent temporal disequilibrium in autochthonous bacterioplankton and phytoplankton production was maintained by the seasonal input of allochthonous organic material into McMurdo Sound. The facts that a) bacteria were both abundant and highly active, b) bacterivory was common among many of the endemic protozoa and some planktonic metazoa and c) these bacterivores consumed >95% of the bacterial production strongly suggest that bacteria are a crucial component in the transfer of energy and material to metazoans in polar regions.

The seasonal partitioning of energy in an estuarine fish, the common goby, Pomatoschistus microps Krøyer

The common goby, Pomatoschistus microps, is an abundant brackish water species which has an appreciable role, both as predator and prey, in the ecosystems of British estuaries. The partitioning of energy within each sex is described and discussed, and energy values are provided for the gonad, liver and carcass throughout almost the entire life of one year class. Partitioning of resources within the body at different times of the year shows considerable variation, not only with time but also between the sexes. In particular, the energy content of the male gonad during the spawning season is never more than 3.7% of that of the female. Important aspects of the biology of the species which relate to energy partitioning are maturation at an early age, high reproductive investment, high stochastic mortality, and death usually after a single breeding season.

Seasonal partitioning and utilization of energy reserves in two age classes of the bay scallop Argopecten irradians irradians (Lamarck)

Seasonal cycles in body component indices, reproductive condition (determined histologically), and storage and utilization of protein, lipid and carbohydrate reserves in various tissue pools, were investigated in two cohorts of the bay scallop Argopecten irradians irradians (Lamarck). Scallops were held in cages at two contrasting localities in Long Island, New York, U.S.A. Gametogenesis occurred mainly at the expense of adductor muscle protein and lipid reserves. Energy loss in the adductor muscle could potentially account for 63 to 99% of the gonadal buildup in the spring. In contrast to prior studies, digestive gland lipid and muscle carbohydrate made an insignificant contribution to the energy demand during reproduction. In first-year, pre-reproductive scallops, adductor muscle protein also contributed 63–66% of the total energy loss during overwintering stress. Senescence of older scallops was evidenced by a more rapid decline in mantle protein reserves than in young individuals. Twenty percent of the older population showed signs of anomalous, advanced oogenesis in March, coincident with the period of highest natural mortality. Results of this study suggest a possible association between senescence and protein metabolism. Contrary to studies showing glycogen to be the main storage product in bivalves such as oysters and mytilids, this study serves to stress the importance of protein as an energy substrate in pectinids.

Growth and Seasonal Partitioning of Dry Matter in Eight-year-old ‘Loring’ Peach Trees

Abstract During the 1984 growing season, trees of ‘Loring’ peach (Prunus persica L. Batsch) on ‘Halford’ rootstocks were divided into the following components; fruit, leaves, shoots, 1-year wood, 2-year wood, frame, and roots. The sampling dates were coincident with key fruit and tree developmental stages: dormant, 15 days after full bloom, the end of Stages I and II of fruit developement, harvest, and 45 days after harvest (leaf fall). At the beginning of Stage II, four additional trees per remaining sampling date were hand-thinned to 15 cm between fruit. Initially, the mean dry weight of trees was 27.1 kg. Unthinned and thinned trees increased 43% and 39%, respectively, in dry weight by 45 days after harvest. Dormant hand-pruning removed about 4 kg of growth. This amount represented nearly the entire season's dry weight of shoot, 1-year-old, and 2-year-old wood growth. The proportion of total tree weight in fruit was increased at harvest in unthinned trees, whereas leaf and 2-year wood dry weight was reduced. A modified harvest index, the proportion of total annual increase distributed to fruit, was 0.50 for unthinned trees and 0.37 for thinned trees. The ratio of annual dry weight increase per unit leaf area was 0.33 and 0.27 kg·m−2 leaf area for unthinned and thinned trees, respectively. The maximum mean leaf area was estimated to be 62.9 × 103 m2·ha−1. The greatest leaf area density, measured at the end of Stage II, was 7.7. Absolute growth rates of vegetative components were highest during Stage II of peach fruit growth, and intermediate during Stage I.

Seasonal partitioning of atympanate moths in relation to bat activity

Certain families of atympanate (deaf) moths are more abundant during the summer at times when bat activity is low. Atympanate moths were collected at ultraviolet lights throughout the summer at a site in southeastern Ontario. Seasonal frequency distributions for individual families showed different trends when compared with ambient bat activity levels. Most saturniids were collected between mid-May and mid-June, before the time when bats are most active (July and August). Lasiocampids were also collected outside the range of high bat activity, emerging in early May, late June, or late August. Population levels of the sphingids, on the other hand, were similar to bat activity levels. From these data, I suggest that some families of deaf moths face reduced selection pressure by bats through temporal isolation.

Trophic relationships among concentrated populations of small fishes in seagrass meadows

Changes in available food and utilized foods for a densely populated guild of animals can uncover periods of niche displacement among particular consumer species or their separate size classes. Dense populations of small fishes and their foods were çensussed for 13 months and studied experimentally in shoalgrass and turtlegrass meadows of Redfish Bay, Texas. Feeding habits were determined with respect to prey availability, and illustrated the extent to which seasonal partitioning of food corresponded to food depletion among these abundant consumers in seagrass meadow food webs. The darter goby, code goby, pinfish, and Gulf pipefish were the most common species throughout the year. Although the darter goby did not show distinct ontogenetic changes in food habits, the code goby, Gulf pipefish, and pinfish demonstrated major ontogenetic progressions of foods selected. Food availability in the seagrass meadows changed seasonally. When major prey such as amphipods were abundant, during spring, many fish species showed high overlap in food use. Regardless of food availability, the code goby and Gulf pipefish fed mainly on amphipods or copepods. The more common darter goby and pinfish seasonally changed their diets with changes in food availability; the darter goby and pinfish were more carnivorous during spring, but they largely consumed epiphytic algae during summer. Cage experiments were used to monitor foods confined with elevated densities of pinfish and darter gobies, relative to control cages at natural overall densities. Prey items in the former cages decreased sharply, with corresponding dietary shifts by these common fishes. During resource depletion, these changes in resource use by these naturally concentrated consumers appeared as temporary partitioning of available resources. This shift occurred during both natural (seasonal) and experimental depletions of food, and appears to result from increased interspecific and intraspecific competition during periods of depleted preferred foods.

Nutrient internal cycling and the trophic regulation of Green Lake, Wisconsin1

Algal nutrients (Si, N, P) and dissolved oxygen were studied in Green Lake, Wisconsin, in 1971– 1972, and in 1978–1980 following a reduction of about 35% in total external P loading in December 1976.Despite oxic conditions, there is more P in the hypolimnion than would be expected from the dissolved oxygen and from classical Redfield stoichiometry. Because of a metalimnetic dissolved oxygen minimum in late summer, the calculation and interpretation of the hypolimnetic oxygen deficit is affected by turbulent transport of dissolved oxygen.Vertical fluxes of P into the mixed layer are important in late spring and early summer, but, owing to metalimnetic P depletion, negligible between mid‐July and mid‐October. Vertical transport of Si into the mixed layer is negligible in summer and early fall compared with inputs from the land drainage basin.Although P is high at spring turnover, epilimnetic concentrations of P are low and Secchi transparency is high by mid‐to‐late summer. These seasonal changes are caused by sedimentation of P and low seasonal inputs from the drainage basin. This P is recovered in the hypolimnion and recirculated throughout the lake at fall overturn. It causes silica limitation of the diatom bloom each succeeding spring.The total P content of Green Lake and its seasonal partition among the layers were remarkably stable between 1971 and spring 1980, despite the reduction in external loading in 1976. The hypolimnetic oxygen deficit also showed no significant change between the first and eighth decades of this century.

Insect Seasonal Cycles: Genetics and Evolution

The cyclic changes associated with seasonal progression probably constitute the most important and all-encompassing set of environmental variables that organisms encounter. Therefore, a fundamental and unifying aspect of each species' or population's life history is the adaptations that determine its seasonal cycle-i.e. the timing of the periods of development, reproduction, dormancy, and migration in relation to seasonal changes in biotic and abiotic factors. Such coordinated sets of seasonal adaptations are popularly referred to as seasonal strategies. Insects occur all over the world, and they encounter an extraordinary variety and range of seasonal conditions. Although insects that experience similar environmental changes sometimes show similar patterns in their seasonal responses, each species appears to have a unique set of eco-physiological adaptations that underlie its seasonal cycle. Moreover, seasonal adaptations vary within species. This great interand intraspecific diversity in seasonal adaptations subserves the broad geographic distribution of the Insecta and enables insects to utilize diverse, often ephemeral, biotic and abiotic resources and unpredictable habitats. Seasonal cycles also strongly influence interactions between organisms, the major example being the seasonal synchrony between host and parasite (sensu lato). Moreover, in some instances species utilizing a single resource reduce competition by the seasonal partitioning of that resource (e.g. 129). Asynchronous seasonal cycles can also serve as important reproductive isolating mechanisms between both sympatrically and allopatrically derived species (96, 137, 138). Knowledge of the evolution of seasonal cycles thus provides a key to understanding how organisms exploit their environment, how they interact,

The radiation climate of an irrigated orange plantation

Regular measurements of incoming and reflected global radiation and net radiation were taken both above and below the canopy of an irrigated orange plantation during one year. The results have been analyzed to show the diurnal and seasonal changes in the main components of the radiation balance. The mean albedo of the plantation throughout the year was 0·16, ranging from a minimum of 0·12 in late spring to a maximum value of 0·21 in late autumn. The reflectivity of a single layer of orange leaves was more than twice that of the entire canopy, indicating the importance of internal absorption of reflected radiation within the canopy. Over the year, 0·28 of the incident global radiation was radiated to space in net long-wave flux, slightly more during the day than the night. The seasonal variation in net long-wave loss at sunrise and sunset was relatively small and showed no clear seasonal trend. Summertime profiles of net radiation from above the canopy to the soil surface beneath the canopy, together with canopy leaf area measurements, were used to compute the extinction coefficient for the plantation. Measurements of the net and short-wave radiation fluxes at ground level, made at different times of the year, were analyzed to show the extent of seasonal changes in the transmission coefficient for both long- and short-wave radiation. Measurements of the soil heat flux show this to be a minor component of the energy balance; seasonal and diurnal variations in this flux are discussed. The annual sum of the radiation balance available to the canopy amounted to 56 per cent of the incident global radiation. The changing seasonal partition of radiation energy between latent and convective heat fluxes has been calculated for both above- and below-canopy conditions and the results show that the leaf surfaces offer a greater resistance to water-vapor diffusion than the bare soil surface beneath the leaf canopy.