Seasonal Production Patterns Research Articles

Seasonal variation in plasma metabolite and hormone concentrations, amino acid utilization and responses to Thyrotropin-releasing hormone in fleeceweight-selected and control Romney rams

Two studies were conducted to examine the effects of season on differences between the Massey University fleeceweight-selected and control lines of Romney sheep in hormone and metabolite concentrations, phenylalanine irreversible loss rate, urea and creatinine clearance and space, and response to an intravenous thyrotropin releasing hormone (TRH) challenge. Rams from the two lines were studied in autumn, winter and spring (5, 9 and 13 months of age) in Experiment 1 or winter and spring (9 and 14 months of age) in Experiment 2. Basal concentrations of urea and creatinine were lower in fleeceweight-selected (FW) than in control (C) rams in both experiments. A significant linexseason interaction, reflecting a greater difference between the lines in winter than in autumn or spring, was observed only in Experiment 1. This interaction could not be accounted for by a corresponding effect on distribution space or clearance of these metabolites. Phenylalanine irreversible loss rate (per unit metabolic body weight) was significantly lower in FW than in C rams, but the magnitude of this difference was not influenced by season (winter v. spring). No differences were observed between the lines in basal concentrations of thyroxine or triiodothyronine, or in the responses of these hormones to TRH. Prolactin response to TRH was lower in FW than in C rams during spring, but this reflected the higher pre-challenge concentrations of this hormone in FW rams. It is concluded that, compared with C rams, FW rams have lower basal concentrations of urea and lower irreversible loss rates (per unit metabolic body weight) of phenylalanine. However, these observations do not explain the less seasonal patterns of wool production in fleeceweight-selected compared with control sheep.

Yield and Quality of Subterranean and White Clover - Bermudagrass and Tall Fescue Associations

Overseeding perennial grass pastures with clovers (Trifolium spp.) can extend the grazing season and improve the quality of available forage. Our objective was to compare forage yield and quality of an annual and perennial clover overseeded on perennial grasses differing in seasonal productivity patterns. Common bermudagrass [Cynodon dactylon (L.) Pers.], ‘Kentucky 31’ tall fescue (Festuca amndinacea Schreb.), and a mixture of the two were established on a Catalpa silty clay soil (fine, montmorillonitic, thermic Fluvaquentic Hapludoll) and oversown in the fall with annual ‘Mt. Barker’ subterranean clover (T. subterraneum L.) and perennial ‘Regal’ white clover (T. repens L.). White clover was oversown in succeeding years to maintain uniform stands, while subterranean clover was permitted to self-seed. Grass and clover dry matter (DM) yield, in vitro digestible DM (IVDDM), crude protein (CP), and neutral detergent fiber (NDF) concentration of total forage were measured at each harvest in each of 3 yr. Overseeding the three grass swards with subterranean clover vs. white clover resulted in greater yield of total forage (3470 vs. 2670 lb DM/acre) and clover (1600 vs. 1080 lb DM/acre). Total forage yield was increased from 2460 to 3880 lb DM/acre and clover yield from 1050 to 1700 lb DM/acre when either clover was oversown on bermudagrass vs. tall fescue. Clover oversown on a mixture of the two grasses did not provide a consistent yield advantage (total forage or clover) over either grass in monoculture. Forage nutrient concentration and intake potential were positively related to clover yield and negatively related to grass yield. We conclude that overseeding bermudagrass rather than tall fescue with clovers will improve distribution and annual yield of superior-quality forage because interspecific competition is minimized during the spring as a result of the seasonal productivity pattern of bermudagrass.

Weight and nutrient content of litter during secondary succession on well-drained uplands of the East Gulf Coastal Plain in Mississippi

Production of forest litter was examined over 2 years in a chronosequence of stands representing four stages of secondary succession on well-drained uplands of the East Gulf Coastal Plain in Mississippi. Average age for these stands was from 22 to 207 years. Early succession was dominated by dense pine stands, whereas mature forests were about 75% hardwood. Litter mass was greatest early in succession, when productivity was highest, and decreased as stands matured. Foliage was approximately 70% of the litter throughout succession. The remaining 30% was mostly large woody material in young pine stands, but a heavy reproductive component in mature stands. Stands dominated by pines produced litter throughout the year, whereas hardwood stands were more cyclic. In young pine stands, the N and P content of litter was already 80–90% of the maximum value realized later in succession, whereas Ca and Mg accumulated in proportion to hardwood basal area. Nutrient concentrations in litter varied by season, component, and stage of succession. Foliar litter that fell in the spring and summer had higher N and P concentrations than that that fell in the fall. Seasonal patterns of litter production, as well as variations in nutrient concentration, made the monthly variation of nutrients returned to the forest floor less extreme than that of foliar litter fall weights.

A comparison of seasonal patterns of photosynthate production and use in branches of red spruce saplings at two elevations

Seasonal patterns of carbon transport from 14C-labeled foliage were examined in red spruce (Picearubens Sarg.) branches at 1935 and 1720 m elevations in the Great Smoky Mountains National Park to characterize possible physiological mechanisms underlying the observed reductions in growth at high elevations. Current and 1-year-old foliage was labeled on 5- to 7-year-old branches of sapling-sized trees in June, August, and October. Retention of 14C was measured after 24 h, and allocation to other branch segments was characterized after 7 days. Total 14C-labeled carbon assimilation was greater in current than in 1-year-old foliage throughout the growing season. This suggests that photosynthetic capacity is high in developing foliage prior to needle maturity and remains high during the first growing season. In August, 14C retention in labeled foliage was less at the higher than at the lower elevation site, possibly reflecting increased respiratory losses that had been previously reported at the higher site. Retention of 14C in current-year shoots as a percent of 14C remaining after 7 days, a measure of sink strength, was high at both sites in June and remained high throughout the season in current-year shoots at the higher elevation site. The relatively high sink activity coupled with the large apportionment of biomass to current-year shoots (19.9 and 26.7% of total branch biomass at the lower and higher elevation sites, respectively) may make red spruce particularly susceptible to stresses such as winter injury that affect young foliage. In addition, the relatively greater sink activity of current-year shoots at the higher elevation site in August and October suggests that the contribution of current-year foliage to overall tree growth may be less at the higher than at the lower elevation site.

Bacterial secondary production and it relation with primary production in the Embalse del Río III Reservoir, Argentina

During an annual period the bacterial biomass (epifluorescence) and secondary production (methyl-3H-thymidine incorporation), as well as biomass (Chlorophyll) and algal primary production (incorporation of NaH14CO3) were studied in the Embalse del Rio III Reservoir, Argentina. The relations between these variables and their responses to seasonal changes in water temperature were analyzed. A close relationship in seasonal patterns of algal primary production and bacterial secondary production was observed, with the estimated rates of bacterial production similar to that obtained by other authors in eutrophic lakes. Bacterial production was 17 to 46% of the primary production, thus, at 60% assimilation efficiency, the bacterioplankton would consume 28 to 77 % of the total fixed carbon. Seasonal trends in algal primary production and bacterial secondary production were mainly affected by temperature.

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.

Seasonal and spatial patterns of oxygen production, respiration and root-rhizome release in Potamogeton perfoliatus L. and Zostera marina L.

Oxygen release to the rhizosphere was measured in situ with O 2 microelectrodes and in hydroponic, split-compartment chambers. Light-dark experiments revealed that O 2 release from the rhizomes of Potamogeton perfoliatus L. was directly dependent on photosynthesis and that O 2 concentrations in sediments near the rhizomes started to decrease within 2 min after plants were darkened. Using Fick's first law of diffusion, the calculated net O 2 flux in P. perfoliatus was approximately 120 μmol g −1 dry weight h −1, similar to fluxes calculated from hydroponic measurements. Root-rhizome O 2 release, photosynthesis and respiration were measured for P. perfoliatus and Zostera marina L., with split-compartment hydroponic chambers in spring, summer and fall. For Z. marina, variability of root-rhizome O 2 release, photosynthesis and respiration were observed between different sites within an eelgrass bed. The highest rates of O 2 release from roots and rhizomes occurred in spring for both species and declined during the summer. For P. perfoliatus, the shortest plants (< 10 cm stem length) had the highest O 2 release, about 43 μmol g −1 dry weight h −1. Root-rhizome O 2 release was significantly related to photosynthesis only for P. perfoliatus. Oxidation of the rhizosphere depended on root-rhizome O 2 release and biomass, which changed seasonally. Although weight-specific release rates were higher for P. perfoliatus than Z. marina, the potential oxidation of the rhizosphere was similar for both species (approximately 4–6 mmol O 2 m −2 h −1) because of relatively high Z. marina root and rhizome biomass.

Earthworms as vectors of viable propagules of mycorrhizal fungi

Casts of 13 earthworm species with differing ecological strategies were collected from more than 60 sites and examined for the presence of propagules of vesicular arbuscular mycorrhizal (VAM) fungi. Intact spores of VAM fungi were found in all but one collection. VAM root fragments were also present in some cast samples. The diversity of VAM spore types found in casts was similar to that in adjacent, uningested soils. However, the relative concentration of spores (No. g −1 dry wt) in casts was higher than in the general soil for the two earthworm species ( Pontoscolex corethrurus and Diplotrema heteropora) for which this was assessed. There was a strong seasonality in the number of spores recovered from casts of D heteropora and this reflected seasonal patterns of spore production in soil. Glasshouse experiments demonstrated that spores recovered from casts of P. corethrurus and D. heternpora maintained viability and initiated mycorrhizal infection on Sorghum bicolor. Similarly, some VAM root fragments found in casts were also able to infect S. bicolor. Spores of ectomycorrhizal fungi and fragments of ectomycorrhizal roots were observed at low frequencies in some cast samples from sites dominated by sclerophyllous vegetation. The infectivity of these propagules was not determined. The ubiquity and ecological significance of short distance transport of VAM propagules by earthworms is discussed in relation to the ecological strategics of earthworms.

Seasonal patterns of pasture production in the Bay of Plenty and Waikato

Patterns of pasture growth were measured on 3 farms in the Bay of Plenty (BOP) and at No2 Dairy (Ruakura Agricultural Centre) in the Waikato from 1989 to 199 1. A standardised trim technique with cages and 4-weekly cutting under grazing was used. Long-term seasonal growth patterns, using a predictive pasture model, were also simulated. Simulated pasture growth from long-term climatic data shows that pasture growth rates are higher in winter, early spring and late autumn in the BOP than the Waikato. However, the actual measurements over the 2 years show that pasture growth over the latter periods is lower at the BOP sites than at the Waikato site. In the BOP the spring peak is much later than in the Waikato while an early summer peak, with higher growth rates than in the Waikato, occurred in the BOP. No such summer peak was evident in the Waikato. The difference between the two regions is caused by the large contribution of subtropical grasses to sward production in summer and autumn, The prolific summer growth of subtropical grasses may explain the low ryegrass content and low pasture production in winter. The lower than expected autumn, winter, spring production may also becaused by low clover content, possibly a result of competition from subtropical grasses and a sulphur deficiency. The apparent low amount of nitrogen fixed by clover may explain the low rates of pasture production over the cooler season. Applications of nitrogen fertiliser may substantially increase dry matter production from April to September. Keywords pasture,simulation,subtropical grasses, Paspalum, Digitaria sanguinalis, growth rates

Climatic change effects on seasonal patterns of pasture production in New Zealand

The performance of livestock industries in New Zealand is affected by a large spatial and seasonal variability in patterns of pasture production. A software package of a database and a predictive pasture production model has been used to make an initial evaluation of the impact of climate change expected around 2030, on the average seasonal pattern of pasture growth at four sites in New Zealand. Mean annual temperature is expected to be 1.2-1.8" C warmer and annual rainfall 510% less. On two cooler/ wetter sites in Southland and Canterbury (irrigated) the predicted pasture production, compared with present, was substantially better in winter (+80%, +50% respectively), better in spring and autumn (+20 to 40%), and unchanged in summer. On two warmer/ drier sites in East Coast (North Island) and Waikato, similar analyses showed improved autumn and winter growth (20-40%) with production unchanged in spring and slightly depressed in summer. Annual production was increased by 20% at South Island sites and about 5% at North Island sites. The onset of spring growth was 2-4 weeks earlier at all sites. Present technology would be expected to be able to formulate management strategies to cope with pasture changes of this magnitude. More reliable predictions of pasture growth will depend on improved climate models which can predict seasonal change in regional climate throughout New Zealand, especially rainfall variability. Keywords climate change, pasture production, mathematical modelling, regional climate

Seasonal patterns of bacterial production and biomass in intertidal sediments of the western Dutch Wadden Sea

Seasonal patterns of bacterial production and biomass in intertidal sediments of the western Dutch Wadden Sea

Seasonal patterns of phytoplankton biomass and productivity in a tropical estuarine complex (west coast of India)

Phytoplankton cell numbers and chlorophylla determinations were made during the premonsoon, monsoon and postmonsoon periods in the Mandovi-Zuari estuarine complex (west coast of India). Primary productivity estimates agreed well with chlorophylla and phytoplankton cell numbers. The consequent decline in salinity with the onset of monsoon was found to be an important factor controlling the distribution, abundance and productivity of phytoplankton. As compared to the Zuari estuary, the Mandovi retained typical estuarine conditions and a greater phytoplankton biomass. Based on primary productivity estimations, the potential fishery resource of this estuarine complex has been computed.

Natural Selection of Parental Ability to Vary Resource Partitioning among Offspring?

Hassell and May (1985) suggest that our understanding of population dynamics would be advanced by integrating behavioural and population studies. An increasing number of published reports reflect the benefits of this approach. However, it may also be profitable for ecologists to review with hindsight some of their older population studies. In particular, one would point to those analyses which have relied on interpretation of population dynamics in terms of macro-ecological factors, like the effect of temperature on breeding patterns, rather than examining other aspects of the species' biology. In this note I want to illustrate a possible example, based on speculative hypothesis rather than a new model, re-interpreting seasonal patterns of egg production in terms of adaptive sexual strategies rather than tactical responses to climate, though these are not mutually exclusive influences. Marine and freshwater amphipods (Crustacea, Gammaridae) do not produce eggs of a constant size. Within species there is significant seasonal variation in the size of eggs, which are usually larger in winter. However, within samples at any season females produce eggs of a similar mean size. Clutch sizes vary significantly between populations, with season and with female size but total clutch volume for a given female size varies to a much smaller extent (Hynes 1955, Kinne 1959, Kolding and Fenchel 1981). The conclusions are that there is, unsurprisingly, an evolutionarily stable egg size but that the adaptive optimum varies with site and season. Why should optimal egg size vary? Skadsheim (1984) modified and expanded a model of Kolding and Fenchel (1981). The model assumes that relative reproductive effort (clutch volume) is fixed for a given female at any given season but that resource partitioning is subject to opposing selective forces to maximise total fecundity (i.e. clutch size) and juvenile survival (which is proportional to egg size). Survival increases with egg size and larger eggs give rise to larger offspring with better reserves and faster growth rates. Net selection maximises effective fecundity: the product of total fecundity and survival probability. Survival rates of any given size class vary seasonally as a consequence of climate and food supply. The implications of this model for optimal egg size are fully explained by Skadsheim (1984: Fig. 6). He concludes that, tactically, mothers respond to harsher weather by producing smaller clutches of larger eggs. A consequence of this reproductive trait which has not so far been considered is that there is variation in individual resource allocation between progeny produced at different times of the year. Winter offspring are effectively more expensive than summer offspring. If there were no other differences between the offspring this observation would be trivial. However, it is now evident that the mechanism of sex determination in at least some amphipod species will also produce a seasonal variation in the production of sons and daughters (Adams et al. 1987). For example, sex in Gammarus duebeni Lilljeborg is determined by environmental conditions (Bulnheim 1978). Male Gammarus carry their mates in precopula (as is widespread among Malacostraca), but are restricted in their freedom of mate choice by other males (Ward 1986) and by loading constraints (Adams and Greenwood 1987, Adams et al. 1989). Larger males have a wide choice of mates but small males may be unable to carry any females. Fitness also increases with size for females at any given season but small females can nonetheless breed successfully. Relative changes in size related fitness are shown in Fig. 1. Animals which will become large should differentiate as males and animals which will be small should be females. Field and laboratory data confirm that, under the influence of photoperiod, most immature animals early in the breeding season differentiate as males but as females later in the season. The critical day length for the shift from male to female varies with latitude. The adaptive nature of this environmental response is that, in a seasonal habitat, those animals produced earlier which grow for longer and will be larger adults in the next breeding season will also be male (Naylor et al. 1988a, b). Photoperiod is a highly predictable index of season, available growth time and future fitness expectations and environmental sex determination (ESD) is the product of a highly flexible system of sex ratio control. Although the relative genetic and environmental components vary between populations of G. duebeni the system is present at all sites sampled (Naylor 1986, H.-P. Bulnheim, pers. comm., P. J. Watt, pers. comm.). Some other species of Gammarus have also been shown to have ESD (Bulnheim 1987, Adams et al. 1987) and the genetic potential for environmental sensitivity could be widespread amongst amphipods. Since apparently non-ESD populations may nonetheless carry the trait

Credit as a Production-Smoothing Device: The Case of Automobiles, 1913–1938

Credit financing of automobile sales and dealer inventories was provided primarily by hundreds of sales finance companies in the interwar United States. The few finance companies tied to auto manufacturers wrote 90 percent of credit business. Manufacturers initially established finance companies not to bolster retail sales but to finance dealers' wholesale inventory so manufacturers could lower average costs by smoothing seasonal production patterns. Moreover, until the Justice Department intervened, manufacturers apparently illegally coerced franchised dealers into using the manufacturer's preferred finance company rather than an independent.

Mood disorders and patterns of creativity in British writers and artists.

Extremes in mood, thought and behavior--including psychosis--have been linked with artistic creativity for as long as man has observed and written about those who write, paint, sculpt or compose. The history of this long and fascinating association, as well as speculations about its reasons for being, have been discussed by several modern authors and investigators, including Koestler (1975), Storr (1976), Andreasen (1978), Becker (1978), Rothenberg (1979), Richards (1981), Jamison (in press) and Prentky (in press). The association between extreme states of emotion and mind and creativity not only is fascinating but also has significant theoretical, clinical, literary and societal-ethical implications. These issues, more thoroughly reviewed elsewhere (Jamison et al. 1980; Richards 1981; Jamison, in press), include the understanding of cognitive, perceptual, mood and behavioral changes common to manic, depressive and creative states; the potential ability to lessen the stigma of mental illness; effects of psychiatric treatment (for example, lithium) on creativity; and concerns raised about genetic research on mood disorders. The current study was designed to ascertain rates of treatment for affective illness in a sample of eminent British writers and artists; to study differences in subgroups (poets, novelists, playwrights, biographers, artists); to examine seasonal patterns of moods and productivity; and to inquire into the perceived role of very intense moods in the writers' and artists' work. One of the major purposes of this investigation was to look at possible similarities and dissimilarities between periods of intense creative activity and hypomania. Hypothesized similarities were based on the overlapping nature of mood, cognitive and behavioral changes associated with both; the episodic nature of both; and possible links between the durational, frequency and seasonal patterns of both experiences.

Factors Associated with Seasonality of Milk Production in New York State

The effect of a base-excess seasonal pricing plan on pattern of production and the role played by various factors related to management and to breeding practices on seasonality of production were investigated. A mail survey of a randomly selected group of farmers in New York State provided the data; 1061 farmers responded to the questionnaire. Seasonality coefficient (difference between spring and fall production as a proportion of fall production) was used as a measure of seasonal production pattern. Three major conclusions were: 1) the use of a base-excess plan in addition to the Louisville plan reduced seasonality when compared with the Louisville plan alone; 2) seasonality was associated with region, type of housing, and herd production; and 3) farmers’ perceptions that spring milk production is more profitable than production in other seasons was an important cause of seasonality.

Seasonal patterns of grass production under cutting or continuous stocking managements

AbstractA comparison was made between the seasonal pattern of net herbage accumulation under cutting and the pattern of intake under continuous variable stocking on a Lolium perenne sward, which was well supplied with nitrogen fertilizer and irrigated to minimize moisture stress.The seasonal pattern of production under monthly cutting showed characteristic asymmetry with a marked peak in production in late May/early June, a rapid decline in June followed by an increase in rate in August and the total amount harvested over the season was 9–28 t organic matter ha−1.By contrast, the seasonal patterns of production on swards grazed by ewes to maintain sward surface heights of 30, 50 and 70 mm all differed fundamentally from that observed under cutting. Production was more evenly distributed throughout the season under these grazing treatments which, it has been proposed, should optimize performance. Total amounts harvested by grazing were 10–84, 10.12 and 8.51 t OM ha−1, respectively. The different patterns of production under cutting and grazing were considered to be associated with differences in the expression of reproductive development in the grass crop and the maintenance of a smaller leaf area per unit ground area under grazing.The results of the study suggest that it is not appropriate to regard the seasonal pattern of net accumulation under a standard cutting regime as representing the potential production of grass under continuous stocking. Moreover, in practice, the more uniform seasonal pattern of production seen in swards maintained on the basis of a controlled sward surface height makes it easier to match the supply of herbage to the appetite of grazing animals as the season progresses.

Yearly variation in seasonal patterns of honeyeater abundance, flower density and nectar production in heathland near Sydney

AbstractDespite a consistent seasonal pattern of daily production of nectar‐energy per unit area with peak production around the end of May, the seasonal pattern of honeyeater abundance is not consistent between years and does not correspond to the pattern of nectar‐energy production.

Seasonality in the antarctic marine environment

1. 1. The Southern Ocean is characterized by the combination of a low but stable temperature with a markedly seasonal pattern of primary production. It therefore offers an environment where the annual variations in temperature and production are uncoupled and it is possible to distinguish the effects of one from the other. 2. 2. The widely observed slow growth of polar marine ectotherms is not due to a direct limitation by the low temperature. Rather the seasonal pattern of growth in many species, together with the frequent limitation of reproduction to the summer months, indicate that many processes are regulated strictly by the availability of food (that is they are resource limited). 3. 3. The degree of seasonality in the biology of polar marine organisms varies with their position in the food web. In general, herbivores have highly seasonal life-histories, whereas carnivores, scavengers and higher level predators show less seasonal patterns of growth or reproduction.

Nutrient recycling through litter production in young plantations of acacia nilotica and eucalyptus tereticornis in a highly alkaline soil

A field study was conducted from July, 1982 to June, 1986 to investigate the litter production and nutrient recycling behaviour of young acacia and eucalyptus plantations raised on a highly alkaline soil. Experimental results showed that litter production in an acacia plantation was significantly higher than in a eucalyptus plantation of the same age and stocking rate during all of the said years. Variation in total annual litter yield during the observed period ranged from 1027 to 1125 kg ha −1 in eucalyptus and from 2537 to 5746 kg ha −1 in acacia. Winter season (November–February) accounted for nearly 40 and 55% of the annual litter-fall in eucalyptus and acacia plantations, respectively. Concentrations of N, P, S and K were significantly higher in acacia litter than in eucalyptus litter. The opposite was true for Ca, Mg, Na, Fe and Mn accumulation, but annually recycled quantities of all nutrients were significantly more in acacia than in eucalyptus. The seasonal recycling trend of these nutrients indicated a high degree of relationship with the seasonal litter production pattern of the two plantations. Concentrations of almost all the nutrients in the litter tended to decline with successive growth years notwithstanding seasonal fluctuations. An ameliorating effect of both plantations on the soil was also observed. Good decomposability and low Na accumulation in the litter of acacia favour raising acacia plantations on highly alkaline sites for their amelioration. Considerably greater accumulation of Na in litter of eucalyptus seems to deter not only the soil reclamation process but also the plant growth.