Variation in nitrogen and phosphorus concentrations of wetland plants

The use of nutrient concentrations in plant biomass as easily measured indicators of nutrient availability and limitation has been the subject of a controversial debate. In particular, it has been questioned whether nutrient concentrations are mainly species' traits or mainly determined by nutrient availability, and whether plant species have similar or different relative nutrient requirements. This review examines how nitrogen and phosphorus concentration and the N:P ratio in wetland plants vary among species and sites, and how they are related to nutrient availability and limitation. We analyse data from field studies in European non-forested wetlands, from fertilisation experiments in these communities and from growth experiments with wetland plants. Overall, the P concentration was more variable than the N concentration, while variation in N:P ratios was intermediate. Field data showed that the N concentration varies more among species than among sites, whereas the N:P ratio varies more among sites than among species, and the P concentration varies similarly among both. Similar patterns of variation were found in fertilisation experiments and in growth experiments under controlled nutrient supply. Nutrient concentrations and N:P ratios in the vegetation were poorly correlated with various measures of nutrient availability in soil, but they clearly responded to fertilisation in the field and to nutrient supply in growth experiments. In these experiments, biomass N:P ratios ranged from 3 to 40 and primarily reflected the relative availabilities of N and P, although N:P ratios of plants grown at the same nutrient supply could vary three-fold among species. The effects of fertilisation with N or P on the biomass production of wetland vegetation were well related to the N:P ratios of the vegetation in unfertilised plots, but not to N or P concentrations, which supports the idea that N:P ratios, rather than N or P concentrations, indicate the type of nutrient limitation. However, other limiting or stressing factors may influence N:P ratios, and the responses of individual plant species to fertilisation cannot be predicted from their N:P ratios. Therefore, N:P ratios should only be used to assess which nutrient limits the biomass production at the vegetation level and only when factors other than N or P are unlikely to be limiting.     

Acquisition and allocation of resources in two waterlogging-tolerant grasses

This study focuses on the following questions: (i) whether reductions in root:shoot ratio have a cost in terms of nutrient balance of the plant, and (ii) whether changes in resource-allocation patterns are proportional among different resources. Our approach was to analyse the variations in the allocation pattern induced by soil waterlogging. A pot experiment was conducted to analyse the effects of waterlogging on biomass, phosphorus (P) and nitrogen (N) accumulation of Paspalum dilatatum and Danthonia montevidensis , two waterlogging-tolerant grasses. When changing from oxic to anoxic conditions, a common response of these and other waterlogging-tolerant grasses is a reduction in allocation to below-ground resources. It was observed that (i) the reduction in root:shoot ratio caused by waterlogging did not have a cost in terms of capacity for nutrient uptake; (ii) resource partitioning within aerial parts was less sensitive to treatments than partitioning between roots and shoots; and (iii) biomass does not appear to be a useful currency for evaluating nutrient-allocation patterns, as the allocation of P and N was inadequately represented by biomass. The results presented here indicate that the existence of compensation mechanisms reduces the predictive value of the partition of resources for the capacity of plants to acquire resources. Data on the allocation of nutrients in relation to biomass suggest that the assumptions of independence in the allocation pattern between biomass and limiting nutrients under the effects of environmental factors can be extended.     

Opportunities to improve nutrient efficiency in pigs and poultry through breeding

Efficiency of food and nutrient (including energy) use are considered the key factors in the economic and environmental performance of livestock systems. The aim of this paper is to consider the basis of genetic variation in the components that constitute dietary nutrient efficiency; and to conclude whether there would be benefit, in any relevant terms, in including these components in breeding programmes that aim to improve nutrient efficiency within pig and poultry systems of production. The components considered are (i) external, pre-ingestion losses, such as food spillage and its relation to feeding behaviour traits, (ii) digestive efficiency, (iii) maintenance requirements, (iv) net efficiency of energy and nutrient utilisation and (v) partitioning of scarce resources within productive and between productive and fitness functions. It is concluded that opportunities to exploit genetic variation exist mainly in the potential to improve the digestive efficiency of pigs and to reduce the maintenance requirements for resources mainly in hens, but also potentially in pigs. Current evidence suggests that there are very weak genetic and phenotypic correlations between components of feeding behaviour and productive traits, and little genetic variation in the net efficiency of nutrient utilisation among poultry and pig genotypes. The implication of the latter is that there would be little exploitable genetic variation in the partitioning of scarce nutrients between productive functions. Currently, there is a lack of understanding of the genetic basis of the partitioning of scarce nutrients between productive and fitness functions, and how this may impact upon the efficiency of nutrient use in pig and poultry systems. This is an area of research to which further effort might usefully be devoted.     

Responses of wetland graminoids to the relative supply of nitrogen and phosphorus

The biomass production of wetland vegetation can be limited by nitrogen or phosphorus. Some species are most abundant in N-limited vegetation, and others in P-limited vegetation, possibly because growth-related traits of these species respond differently to N versus P supply. Two growth experiments were carried out to examine how various morphological and physiological traits respond to the relative supply of N and P, and whether species from sites with contrasting nutrient availability respond differently. In experiment 1, four Carex species were grown in nutrient solutions at five N:P supply ratios (1.7, 5, 15, 45, 135) combined with two levels of supply (geometric means of N and P supply). In experiment 2, two Carex and two grass species were grown in sand at the same .ve N:P supply ratios combined with three levels of supply and two light intensities (45% or 5% daylight). After 12-13 weeks of growth, plant biomass, allocation, leaf area, tissue nutrient concentrations and rates and nutrient uptake depended signi.cantly on the N:P supply ratio, but the type and strength of the responses differed among these traits. The P concentration and the N:P ratio of shoots and roots as well as the rates of N and P uptake were mainly determined by the N:P supply ratio; they showed little or no dependence on the supply level and relatively small interspeci.c variation. By contrast, the N concentration, root mass ratio, leaf dry matter content and speci.c leaf area were only weakly related to the N:P supply ratio; they mainly depended on plant species and light, and partly on overall nutrient supply. Plant biomass was determined by all factors together. Within a level of light and nutrient supply, biomass was generally maximal (i.e. co-limited by N and P) at a N:P supply ratio of 15 or 45. All species responded in a similar way to the N:P supply ratio. In particular, the grass species Phalaris arundinacea and Molinia caerulea showed no differences in response that could clearly explain why P. arundinacea tends to invade P-rich (N-limited) sites, and M. caerulea P-limited sites. This may be due to the short duration of the experiments, which investigated growth and nutrient acquisition but not nutrient con­servation.     

Influence of sward structure on daily intake and foraging behaviour by horses

The spatial heterogeneity of grasslands determines the abundance and quality of food resources for grazing animals. As plants mature, they increase in mass, which allows greater instantaneous intake rates, but the cell wall concentrations increase too, reducing diet quality. In ruminants, daily intake rates are often constrained by the time needed for the ingesta to pass through the rumen, which is influenced by the rate of digestion. It has been suggested that the digestive constraint should have much less effect on hindgut fermenters such as equids. Horses play an increasing role in the management of grasslands in Europe, but the data on the influence of the heterogeneity of the vegetation on their daily intake and foraging behaviour are sparse. We report here the results of a preliminary study concerning the effects of sward structure on nutrient assimilation and the use of patches of different heights by horses grazing successively a short immature, a tall mature and a heterogeneous pastures (with short and tall swards). Daily nutrient assimilation was higher in the heterogeneous pasture compared to the short (+35%) and the tall (+55%) ones. The digestive constraints may have limited voluntary intake by horses on the tall swards. In the heterogeneous pasture, the mean height used for feeding (6 to 7 cm) by horses was intermediate between the heights used in the short (4 to 5 cm) and tall pastures (22 to 23 cm), and the animals may thus have benefited from both short swards of high quality and tall swards offering a higher instantaneous intake rate.     

Distinct commensal bacteria associated with ingesta and mucosal epithelium in the gastrointestinal tracts of calves and chickens

The primary aim of this study was to determine whether distinct gastrointestinal tract (GIT) microbial communities are established within ingesta and on mucosal surfaces of dairy calves and chickens to evaluate whether the principle of microbial segregation is of broad biological significance. Multivariate analysis of the predominant bacterial PCR-denaturing gradient gel electrophoresis profiles and estimated bacterial populations were compared in rumen, jejunum, ileum, cecum, and colon ingesta and matching mucosal tissues. Samples collected from 3-week old (n = 8) and 6-month old (n = 8) calves revealed that the predominant mucosa-associated bacteria were distinct from those inhabiting ingesta, and bacterial diversity varied significantly among the GIT regions. The estimated bacterial populations displayed significant regional differences for bovine mucosal (P = 0.05) and for ingesta (P = 0.03) only at 6 months of age. This indicates an established segregation of the enteric bacterial population throughout the GIT in weaned calves. Analysis of ileal and cecal bacterial profiles in chickens confirmed that the segregation of commensal bacteria between ingesta and the mucosal tissue was a common biological phenomenon. Our study provides some fundamental understanding of the impact of sample type (mucosa vs. ingesta), region, and host age on commensal bacterial establishment and segregation throughout the GIT.     

AN EXPERIMENTAL ASSESSMENT OF THE EFFECTS OF NUTRIENT ENHANCEMENT ON THE INTERTIDAL KELP HEDOPHYLLUM SESSILE (LAMINARIALES,PHAEOPHYCEAE)1

We tested whether experimentally enhancing nutrients around the kelp Hedophyllum sessile would increase growth, tissue nitrogen, or allocation to phenolic compounds. Packets of time‐released fertilizer were anchored adjacent to fronds in the field, and algae were monitored for several months. Although fertilizer packets increased the concentration of ammonium, nitrate, and phosphorus adjacent to treatment algae by an order of magnitude, there was little evidence that this increased frond growth or size. Hedophyllum individuals showed no tendency to alter allocation patterns in response to nutrient addition. Tissue carbon and nitrogen was unchanged by the nutrient manipulation; most H. sessile had tissue nitrogen concentrations in excess of 2.0% of dry mass. Additionally, the concentration of phloroglucinol equivalents was also unaffected by the presence of increased water column nutrients. Although nutrient concentrations in the water column surrounding the study site show relatively high mean values for ammonium, nitrate, and phosphorus, they are characterized by high spatial and temporal variation. Nonetheless, these data suggest that this intertidal kelp is not limited by nitrogen or phosphorus in wave‐exposed areas in the northeast Pacific Ocean.     

NUTRIENTS AND THE PRODUCTIVITY OF ESTUARINE AND COASTAL MARINE ECOSYSTEMS

SUMMARY

Recent research on estuarine and coastal marine systems has revealed two particularly interesting things about nutrients and productivity. First is the observation that these areas are among the most intensively fertilized environments on earth. Second is the common finding that much of the characteristically high primary productivity of these shallow waters is supported by nutrients released or recycled by pelagic and benthic microheterotrophs. Since nutrient inputs to coastal areas have probably been increasing and are likely to continue to do so, it is particularly important to understand the relationship between nutrient loading and nutrient cycling and the extent to which their interactions may set the levels of primary and secondary production in coastal systems.

That some direct relationship exists between the input of nutrients and the productivity of higher trophic levels has been a principle of marine ecology since the turn of the century. It is surprisingly difficult, however, to find quantitative evidence showing that estuaries, lagoons, or other coastal waters respond to eutrophication by producing a larger biomass of animals. Part of this difficulty arises because the amount of nitrogen or phosphorus incorporated in animal tissue is a very small term in the total nutrient budget of an estuary, and the accuracy and precision of ecological field measurements may not be adequate to the task. In addition, the response of natural systems to nutrient enrichment is compounded by changes in climate, hydrography, harvesting effort and technology, and pollution.

Attempts to avoid some of these problems by carrying out controlled nutrient addition experiments in the field or with mesocosms have been much rarer in marine ecology than in limnology. The results that are available for such studies seem to suggest that there is a modest enhancement of primary production with nutrient addition, but that most of this extra organic matter is rapidly consumed, presumably by microheterotrophs. In other words, as nutrient inputs rise, so does the rate of nutrient recycling. Only a small fraction of the added nutrients appears as an increment in the production of higher trophic levels.     

Plant allometry, stoichiometry and the temperature-dependence of primary productivity

Aim While physical constraints influence terrestrial primary productivity, the extent to which geographical variation in productivity is influenced by physiological adaptations and changes in vegetation structure is unclear. Further, quantifying the effect of variability in species traits on ecosystems remains a critical research challenge. Here, we take a macroecological approach and ask if variation in the stoichiometric traits (C: N: P ratios) of plants and primary productivity across global‐scale temperature gradients is consistent with a scaling model that integrates recent insights from the theories of metabolic scaling and ecological stoichiometry. Location This study is global in scope, encompassing a wide variety of terrestrial plant communities. Methods We first develop a scaling model that incorporates potentially adaptive variation in leaf and whole‐plant nutrient content, kinetic aspects of photosynthesis and plant respiration, and the allometry of biomass partitioning and allocation. We then examine extensive data sets concerning the stoichiometry and productivity of diverse plant communities in light of the model. Results Across diverse ecosystems, both foliar stoichiometry (N : P) and ‘nitrogen productivity’ (which depends on both community size structure and plant nutrient content) vary systematically across global scale temperature gradients. Primary productivity shows no relationship to temperature. Main conclusions The model predicts that the observed patterns of variation in plant stoichiometry and nutrient productivity may offset the temperature dependence of primary production expected from the kinetics of photosynthesis alone. Our approach provides a quantitative framework for treating potentially adaptive functional variation across communities as a continuum and may thus inform studies of global change. More generally, our approach represents one of the first explicit combinations of ecological stoichiometry and metabolic scaling theories in the analysis of macroecological patterns.     

Interspecific Variation in RGR and the Underlying Traits among 24 Grass Species Grown in Full Daylight

Abstract: A growth analysis was conducted with 24 central European grass species in full daylight to test whether traits underlying interspecific variation in relative growth rate (RGR) are the same in full daylight as they are at lower light, and whether this depends on the ecological characteristics of the studied species, i.e., their requirements with respect to nutrient and light availability.
In contrast to studies with herbaceous species at lower light, net assimilation rate (NAR) contributed more than leaf area ratio (LAR) or specific leaf area (SLA) to interspecific variation in RGR. This was associated with a larger interspecific variation in NAR than found in experiments with lower light. Without the two most shade-tolerant species, however, the contribution of LAR and its components to interspecific variation in RGR was similar or even higher than that of NAR.
Leaf dry matter content correlated negatively with RGR and was the only component of LAR contributing in a similar manner to variation in LAR and RGR. There was a positive correlation between NAR and biomass allocation to roots, which may be a result of nutrient-limited growth. RGR correlated negatively with biomass allocation to leaves. Leaf thickness did not correlate with RGR, as the positive effect of thin leaves was counterbalanced by their lower NAR.
Low inherent RGR was associated with species from nutrient-poor or shady habitats. Different components constrained growth for these two groups of species, those from nutrient-poor habitats having high leaf dry matter content, while those from shady habitats had thin leaves with low NAR.     

How lichens impact on terrestrial community and ecosystem properties

Lichens occur in most terrestrial ecosystems; they are often present as minor contributors, but in some forests, drylands and tundras they can make up most of the ground layer biomass. As such, lichens dominate approximately 8% of the Earth's land surface. Despite their potential importance in driving ecosystem biogeochemistry, the influence of lichens on community processes and ecosystem functioning have attracted relatively little attention. Here, we review the role of lichens in terrestrial ecosystems and draw attention to the important, but often overlooked role of lichens as determinants of ecological processes. We start by assessing characteristics that vary among lichens and that may be important in determining their ecological role; these include their growth form, the types of photobionts that they contain, their key functional traits, their water‐holding capacity, their colour, and the levels of secondary compounds in their thalli. We then assess how these differences among lichens influence their impacts on ecosystem and community processes. As such, we consider the consequences of these differences for determining the impacts of lichens on ecosystem nutrient inputs and fluxes, on the loss of mass and nutrients during lichen thallus decomposition, and on the role of lichenivorous invertebrates in moderating decomposition. We then consider how differences among lichens impact on their interactions with consumer organisms that utilize lichen thalli, and that range in size from microfauna (for which the primary role of lichens is habitat provision) to large mammals (for which lichens are primarily a food source). We then address how differences among lichens impact on plants, through for example increasing nutrient inputs and availability during primary succession, and serving as a filter for plant seedling establishment. Finally we identify areas in need of further work for better understanding the role of lichens in terrestrial ecosystems. These include understanding how the high intraspecific trait variation that characterizes many lichens impacts on community assembly processes and ecosystem functioning, how multiple species mixtures of lichens affect the key community‐ and ecosystem‐level processes that they drive, the extent to which lichens in early succession influence vascular plant succession and ecosystem development in the longer term, and how global change drivers may impact on ecosystem functioning through altering the functional composition of lichen communities.     

三种高寒植物幼苗生物量分配及性状特征对光照和养分的响应

为了解高寒植物幼苗对生境资源异质性的适应策略,以高寒草甸中常见的3种草本植物大耳叶风毛菊(Saussurea macrota)、甘西鼠尾草(Salvia przewalskii)和千里光(Senecio scandens)为材料,比较研究了这3种植物幼苗对不同光照和养分资源的响应。结果表明:光照和养分异质性显著影响了3种植物幼苗的性状特征和生物量分配,并存在一定的交互影响。随着光照的降低,3个物种的幼苗的生物量和根分配呈现降低趋势,但是其株高、比叶面积、叶分配、茎分配却逐渐升高。在低养分条件下,3个物种幼苗的总生物量、株高、比叶面积和叶分配均降低,而根分配均却显著增加。对于光照和养分资源异质性而言,光照异质性对高寒植物生物量分配和性状特征的改变具有更大的影响。喜阴物种大耳叶风毛菊和喜光物种甘西鼠尾草比中性生境物种千里光表现出了较大的性状特征和生物量分配的可塑性指数。     

Evolutionary significance of fecundity reduction in threespine stickleback infected by the diphyllobothriidean cestode Schistocephalus solidus

Parasites may cause fecundity reduction in their hosts via life‐history strategies involving simple nutrient theft or manipulation of host energy allocation. Simple theft of nutrients incidentally reduces host energy allocation to reproduction, whereas manipulation is a parasite‐driven diversion of energy away from host reproduction. We aimed to determine whether the diphyllobothriidean cestode parasite Schistocephalus solidus causes loss of fecundity in the threespine stickleback fish (Gasterosteus aculeatus) through simple nutrient theft or the manipulation of host energy allocation. In one stickleback population (Walby Lake, Matanuska‐Susitna Valley, Alaska), there was no difference in the sizes and ages of infected and uninfected reproducing females. Lightly‐ and heavily‐infected females produced clutches of eggs, but increasingly smaller percentages of infected females produced clutches as the parasite‐to‐host biomass ratio (PI) increased. Infected, clutch‐bearing sticklebacks showed reductions in clutch size, egg mass, and clutch mass, which were related to increases in PI and reflected a reduction in reproductive parameters as growth in parasite mass occurs. The findings obtained for this population are consistent with the hypothesis of simple nutrient theft; however, populations of S. solidus in other regions may manipulate host energy allocation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 835–846.     

Competitive ability of two Brassica varieties in relation to biomass allocation and morphological plasticity under varying nutrient availability

Green cabbage (Brassica campestris, leafy variety) and turnip (Brassica campestris var. rapifera, rooty variety) were grown in both monocultures and mixtures at three nutrient levels to investigate their responses to nutrient availability with respect to biomass allocation, morphological plasticity and competitive ability. Their allocation parameters and leaf morphological traits were affected by both nutrient availability and developmental stage. Both of the varieties had a smaller biomass allocation to leaf blades, but a greater allocation to petioles at high nutrient levels. Root:shoot ratio (RSR) of green cabbage decreased with increasing nutrient availability, whereas that of turnip increased. Turnip had a smaller leaf blade weight ratio (LBWR) than cabbage, being compensated for by larger leaf area ratio (LAR) and specific leaf area (SLA). Leaf area ratio and SLA of both the varieties increased with increasing nutrient availability as did their mean dry weights. The mean dry weight of turnip was slightly greater than that of green cabbage in their respective monocultures, while that of green cabbage was greater than that of turnip in their 1:1 mixture. Therefore, green cabbage, having inherently greater biomass allocation to leaves, was generally more competitive than turnip with more biomass allocation to roots, especially at higher nutrient levels. However, within a variety, morphological plasticity (variation in LAR and SLA) was more important than the plasticity in biomass allocation (e.g. variation in RSR and LBWR) in determining competitive ability. The implication of our results is that competition models based on biomass allocation pattern alone may fail to predict competitive outcomes and that such models should also take morphological plasticity into full account.     

Shading reduces exploitation of soil nitrate and phosphate by Agropyron desertorum and Artemisia tridentata from soils with patchy and uniform nutrient distributions

 Shading may both lessen the demand for soil nutrients and also the energy supply for nutrient acquisition. Since root foraging for nutrients in patchy environments can be energy-costly, especially for an immobile nutrient such as phosphate (P), the effects of shading may be most expected in heterogeneous soils. Plant acquisition of nitrate (N) and phosphate from soils with patchy and uniform nutrient distributions was determined in a field study under open sunlight and with shading for two common perennial Great Basin shrub steppe species, Agropyron desertorum and Artemisia tridentata. Partial shading in a pattern which can occur in shrub steppe vegetation significantly decreased plant N and P acquisition from soils both in the patchy and the uniform nutrient treatments. Artemisia was more affected by the shading than was Agropyron. Exploitation of the rather immobile P ion by both species was reduced to a much greater degree by the shading in the patchy distribution treatment than in the uniform nutrient treatment. As expected, plant acquisition of the more mobile N varied little with nutrient distribution treatment for both species and the depression of N acquisition by shading was the same in both nutrient distributions. The effects of shading appeared to have had its primary influence on different components of root foraging in the two species, especially in the nutrient-rich patches. For Agropyron shading primarily affected root proliferation, as indicated by reduced root density in patches. For Artemisia, shading most influenced root physiological uptake capacity and this was most pronounced in the nutrient-rich patches. While aboveground competition for light may generally reduce nutrient acquisition, the effects appear to be most pronounced if root systems of these steppe species are foraging for nutrients such as P in spatially heterogeneous soils. Received: 29 February 1996 / Accepted: 16 July 1996     

河口区营养物基准制定方法

河口区营养物基准是河口环境监测、评估和管理的基础。然而,如何从营养盐基准制定的角度分析相关的科学基础问题,提出有效操作方式和制定方法仍然缺乏系统研究,国内外营养物基准制定亦处于探索阶段。从基准状态的判断、基准关注的营养物质、河口生态系统对营养盐的响应特征3个方面分析了基准制定的科学基础问题,认为基准值的判断可以参照状态为基础,N、P、Si、Fe等对植物生长具有较明显限制作用,实践中均应纳入考虑,复杂的物理特征使河口营养物敏感性具有显著差异,地理区域和河口类型的划分有利于基准的制定。结合上述分析及国内外经验,提出了基准制定的6个步骤,认为河口分类与分区、参照状态确立是基准制定的核心步骤,其分析方法较多,需要针对河口特征选择并调整。结合我国营养物基准研究现状和管理需求,提出了建立我国河口基础数据库、制定河口营养物基准技术指南、建立基于生态系统健康的河口营养物基准及标准体系等建议。     

Towards a biological basis for predicting nutrient partitioning: the dairy cow as an example

Prediction of nutrient partitioning is a long-standing problem of animal nutrition that has still not been solved. Another substantial problem for nutritional science is how to incorporate genetic differences into nutritional models. These two problems are linked as their biological basis lies in the relative priorities of different life functions (growth, reproduction, health, etc.) and how they change both through time and in response to genetic selection. This paper presents recent developments in describing this biological basis and evidence in support of the concepts involved as they relate to nutrient partitioning. There is ample evidence that at different stages of the reproductive cycle various metabolic pathways, such as lipolysis and lipogenesis, are up or down regulated. The net result of such changes is that nutrients are channelled to differing extents to different organs, life functions and end-products. This occurs not as a homeostatic function of changing nutritional environment but rather as a homeorhetic function caused by the changing expression of genes for processes such as milk production through time. In other words, the animal has genetic drives and there is an aspect of nutrient partitioning that is genetically driven. Evidence for genetic drives other than milk production is available and is discussed. Genetic drives for other life functions than just milk imply that nutrient partitioning will change through lactation and according to genotype - i.e. it cannot be predicted from feed properties alone. Progress in describing genetic drives and homeorhetic controls is reviewed. There is currently a lack of good genetic measures of physiological parameters. The unprecedented level of detail and amounts of data generated by the advent of microarray biotechnology and the fields of genomics, proteomics, etc. should in the long-term provide the necessary information to make the link between genetic drives and metabolism. However, gene expression, protein synthesis etc, have all been shown to be environmentally sensitive. Thus, a major challenge in realising the potential afforded by this new technology is to be able to be able to distinguish genetically driven and environmentally driven effects on expression. To do this we need a better understanding of the basis for the interactions between genotypes and environments. The biological limitations of traditional evaluation of genotype × environment interactions and plasticity are discussed and the benefits of considering these in terms of trade-offs between life functions is put forward. Trade-offs place partitioning explicitly at the centre of the resource allocation problem and allow consideration of the effects of management and selection on multiple traits and on nutrient partitioning.     

The budgets of nitrogen and phosphorus in shallow eutrophic Lake Võrtsjärv (Estonia)

Hydrobiologia - The nutrient budget, phytoplankton primary productionand sedimentation rate were studied weekly in the large(270 km2) and shallow (mean depth 2.8 m)eutrophic Lake...