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1.
Vegetation growth models often concentrate on the interaction of vegetation with soil moisture but usually omit the influence of groundwater. However the proximity of groundwater can have a profound effect on vegetation growth, because it strongly influences the spatial and temporal distribution of soil moisture and therefore water and oxygen stress of vegetation. In two papers we describe the behavior of a coupled vegetation-groundwater-soil water model including the competition for water and light. In this first paper we describe the vegetation model, compare the model to measured flux data and show the influence of water and light competition in one dimension. In the second paper we focus on the influence of lateral groundwater flow and spatial patterns along a hillslope. The vegetation model is based on a biophysical representation of the soil-plant-atmosphere continuum. Transpiration and stomatal conductance depend both on atmospheric forcing and soil moisture content. Carbon assimilation depends on environmental conditions, stomatal conductance and biochemical processes. Light competition is driven by tree height and water competition is driven by root water uptake and its water and oxygen stress reaction. The modeled and measured H2O and CO2 fluxes compare well to observations on both a diurnal and a yearly timescale. Using an upscaling procedure long simulation runs were performed. These show the importance of light competition in temperate forests: once a tree is established under slightly unfavorable soil moisture conditions it can not be outcompeted by smaller trees with better soil moisture uptake capabilities, both in dry as in wet conditions. Performing the long simulation runs with a background mortality rate reproduces realistic densities of wet and dry adapted tree species along a wet to dry gradient. These simulations show that the influence of groundwater is apparent for a large range of groundwater depths, by both capillary rise and water logging. They also show that species composition and biomass have a larger influence on the water balance in eco-hydrological systems than soil and groundwater alone. 相似文献
2.
In temperate climates groundwater can have a profound effect on vegetation, because it strongly influences the spatio-temporal distribution of soil moisture in the rootzone and therefore the occurrence of water and oxygen stress of vegetation. This article focuses on vegetation and groundwater dynamics along a hill slope by developing and evaluating a fully coupled hydrological-vegetation model for a temperate forest ecosystem. The vegetation model is described in part 1 of this series of two papers. To simulate the hydrology an extended version of the saturated-unsaturated hydrological model STARWARS has been used. The coupled model is used to investigate both the short and long-term dynamics for a system of two species. Both compete for light and water where one is adapted to wet conditions and the other to dry conditions. The daily dynamics show that the influence of groundwater is particularly strong in spring when waterlogging occurs due to decreased evapotranspiration in winter. Long simulation runs of 1000 years were performed to study the equilibrium state for the two species. Comparison of simulation results with observations of groundwater depth and vegetation types along a dry-wet gradient in a natural forest shows that a reductionist approach is able to capture these patterns well. Sensitivity analysis shows that the border between wet- and dry-adapted species moves upslope with increased rainfall, decreased slope angle and decreased aquifer thickness. These results are similar to previous findings which were based on global maximization of ecosystem evaporation or minimizing ecosystem stress. Comparison of runs with a fixed and a dynamic groundwater table shows that a dynamic groundwater table facilitates a wider transition zone between vegetation types along the hill slope. In this transition the biomass of vegetation is higher in the case of a dynamic groundwater than in case of a static groundwater table. This underlines the importance of incorporating spatial groundwater dynamics in models of groundwater influenced ecosystems. 相似文献
3.
Short-term physiological indicators of N deficiency in phytoplankton: a unifying model 总被引:2,自引:0,他引:2
Nitrogen resupply to N-limited microalgae elicits several rapid physiological responses which have been used as indicators of N deficiency. These include a stimulation of dark respiration and dark carbon fixation. In addition, N resupply to some microalgae results in a transient suppression of photosynthetic carbon fixation. Long term, N enrichment results in an increase in the rate of photosynthesis and ultimately in the rate of growth. In this report these physiological indicators of N deficiency are documented as a function of steady-state growth rate in Selenastrum minutum Naeg. Collins (Chlorophyta). Based on previous biochemical and physiological studies, we suggest that these short-term responses are a reflection of redirection of photosynthetic carbon flow to the process of N assimilation. A unifying model is proposed that interrelates these responses to N resupply. 相似文献
4.
Guang-yu Wang Michael D. Greenfield Todd E. Shelly 《Behavioral ecology and sociobiology》1990,27(3):191-198
Summary Males of the desert grasshopper Ligurotettix coquilletti typically eclose 3–5 weeks prior to females. Early-eclosed males experience more female encounters than the later-eclosed individuals. Evidence suggests that the number of encounters may be proportional to male lifetime mating success. Early-eclosed males enjoyed greater adult lifespans, occupied and defended higher quality territories (Larrea shrubs), and tended to be dominant on these shrubs if several males were present. The elevated number of female encounters were not conferred on early-eclosed males by their extended survivorship, but rather by the high quality of their territories, which retained numerous females, and their dominant behavior. We evaluate several female-benefit and male-benefit hypotheses for the evolution of protandry and propose that in L. coquilletti, the phenomenon arose due to male-male competition for female-encounter sites, a mechanism not considered in earlier models. Finally, we discuss several reasons for the high variance in the date of male eclosion. 相似文献
5.
Catherine A. Toft 《Behavioral ecology and sociobiology》1984,14(4):287-296
Summary This study compares time budgets of males and females of two sympatric species of bee flies, Lordotus pulchrissimus and L. miscellus. These species occur synchronously in sand dune habitat on the north shore of Mono Lake, Mono Co., California, and feed almost exclusively on the flowers of a composite shrub, Chrysothamnus nauseosus. The two closely related species, with similar ecological requirements and in an identical environment, allocate time and energy in very different ways, even when accomplishing the same ecological goals. L. pulchrissimus males and females engage respectively in aggressive interactions and feeding primarily in the morning. In contrast, L. miscellus males and females intersperse brief periods of resting with flying when defending territories and feeding, and they keep up these activities until later in the day. Similarly within species, males are involved in aggressive interactions for a shorter period each day, and females feed over a longer period. Flies in all sex-species classes but male pulchrissimus allocate their time energetically in similar ways. Male pulchrissimus spend more time each day in energetically costly activities; they engage in continuous hovering flight and intense interactions in aerial aggregations. While male miscellus feed little, male pulchrissimus spend a large portion of their time feeding, approximately as much as females, contrary to the expectation that males should be foraging-time minimizers. This study corroborates the conclusions of previous studies on bee-fly communities by showing that nectar and pollen are important resources for adult bee flies, at least for some species: Individuals of these two species spend a large proportion of their adult lifetimes feeding. 相似文献
6.
Zhu Xiaodong Yang Fen Wei Chaoyang Liang Tao 《Environmental geochemistry and health》2016,38(1):233-241
Environmental Geochemistry and Health - The objective of this study was to examine whether a single model could be used to predict the bioaccessibility of heavy metals in soils in two adjacent... 相似文献
7.
Gauri R. Pradhan Antje Engelhardt Carel P. van Schaik Dario Maestripieri 《Behavioral ecology and sociobiology》2006,59(3):333-343
Female copulation calls are mating-associated vocalizations that occur in some species of Old World monkeys and apes. We argue
that copulation calls have two immediate functions: to encourage mating attempts by other males and to increase mate guarding
by the consort male. We hypothesize that female copulation calls have evolved under the selective pressures of risk of infanticide
and sperm competition. When male mate guarding is effective, copulation calls allow females to concentrate paternity in dominant
males and benefit from their protection against the risk of infanticide. When mate guarding is ineffective, copulation calls
may bring genetic benefits to females through facilitation of sperm competition. We present a quantitative model in which
interspecific variation in females' promiscuity predicts their tendency to use copulation calls in conjunction with mating.
The model predicts that in species with little female promiscuity, copulation calls should be rare and exhibited only in association
with mating with dominant males. In species in which females are highly promiscuous, copulation calls should be frequent and
unrelated to male dominance rank. The limited data available to test the model support its main predictions as well as the
predicted relation between copulation calls and male dominance rank.
相似文献
Dario MaestripieriEmail: |
8.
On temperature and water limitation of net ecosystem productivity: Implementation in the C-Fix model
Monitoring, understanding and modelling carbon emission and fixation fluxes are key actions to guide climate change stakeholders in the application of mitigation strategies. In this study, we use the remote sensing model C-Fix at the local stand scale to improve the integration of algorithms for water and temperature limitation. These new algorithms are applied to estimate net ecosystem productivity in a fully water limited mode. 相似文献
9.
Knut L. Seip 《Ecological modelling》1980,10(2):77-104
A mathematical model has been constructed for the algal community on the rocky shores of a Norwegian fjord. We report here on the studies of competition and colonization along a vertical transect from the upper intertidal to the sublittoral habiats. Results on species abundance and distribution (patterns of zonation) and time to reach maturity have been compared to observations both in the fjord area and in other rocky shore areas.Competition coefficients for the algae were inferred from plant morphology and shown to be in agreement with observations of algal abundance and their zone-forming ability. Competition restricts the distribution of the species, especially at the lower elevations, but does not alter their relative position. However, increasing uniform competition prolongs the time in which zone-forming can occur, and it also decreases the overall biomass which an area can sustain. Colonization by a single species may create transient stages in community development of the same order of magnitude as algae longevity, and probably also alters the zonation pattern to some degree.The simulation results indicate that the large-scale algal distribution pattern in the Hardangerfjord area results from global stability of the rocky shore community. 相似文献
10.
The non-random dispersal of plant propagules is thought to counter competitive exclusion and thus promote the survival of competitively inferior species. We investigated this process by modelling the outcome of interactions between species with competitive ability defined as a function of both life-history traits and the environment with both random and clustered dispersal strategies and in environmentally homogeneous and heterogeneous environments. Four main results emerged: (1) environmental heterogeneity was seen to promote co-existence in conjunction with associated trait variation for tolerance to the environmental variable and where this trait variation was effectively limited by ‘trade-off’ such that no single species had an overall competitive advantage, (2) consistent with theory, random dispersal appeared to enhance the likelihood of competitive exclusion, whereas clustering favoured co-existence, (3) the ecological outcome of interactions between dispersal and competitive relationships varied as a function of the trait determining the competitive advantage within a particular environment, and (4) promotion of co-existence by clustered dispersal was most marked when associated with environmental heterogeneity. It is argued that these results suggest that current ecological models of species interactions may need to be modified to incorporate a more realistic understanding of competitive ability if we are to better understand the factors effecting species co-existence. 相似文献
11.
Kraus F. B. Neumann P. van Praagh J. Moritz R. F. A. 《Behavioral ecology and sociobiology》2004,55(5):494-501
Honeybee queens (Apis mellifera) show extreme levels of polyandry, but the evolutionary mechanisms underlying this behaviour are still unclear. The sperm-limitation hypothesis, which assumes that high levels of polyandry are essential to get a lifetime sperm supply for large and long-lived colonies, has been widely disregarded for honeybees because the semen of a single male is, in principle, sufficient to fill the spermatheca of a queen. However, the inefficient post-mating sperm transfer from the queens lateral oviducts into the spermatheca requires multiple matings to ensure an adequate spermatheca filling. Males of the African honeybee subspecies A. m. capensis have fewer sperm than males of the European subspecies A. m. carnica. Thus, given that sperm limitation is a cause for the evolution of multiple mating in A. mellifera, we would expect A. m. capensis queens to have higher mating frequencies than A. m. carnica. Here we show that A. m. capensis queens indeed exhibit significantly higher mating frequencies than queens of A. m. carnica, both in their native ranges and in an experiment on a North Sea island under the same environmental conditions. We conclude that honeybee queens try to achieve a minimum number of matings on their mating flights to ensure a sufficient lifetime sperm supply. It thus seems premature to reject the sperm-limitation hypothesis as a concept explaining the evolution of extreme polyandry in honeybees.Communicated by R.E. Page 相似文献
12.
Sperm competition should select for increased sperm production if the probability of fertilization by a specific male is proportional to the relative number of sperm inseminated. A review of the literature generally supports the predicted positive association between sperm production or allocation and various measures of the presumed intensity of sperm competition. However, it is not clear how increased sperm competition is related to extra-pair paternity, and it remains unknown whether certainty of paternity should be associated with relative testis size. Based on a large sample of bird species with information on extra-pair paternity gathered from the literature, we demonstrate that testis mass is related positively to the level of extra-pair paternity, after controlling for body size and phylogeny. Although large testes may be necessary to avoid sperm depletion in species in which males frequently engage in multi-pair copulations, we argue that selection has favoured increased testis mass in situations of more intense sperm competition in order to retaliate against copulations by rival males. The fact the males are not always successful in retaliating against rival ejaculates further suggests that females may largely control the allocation of paternity in birds and that increased sperm production by males may simply be a male strategy to make the best of a bad situation. 相似文献
13.
Anders Pape Møller 《Behavioral ecology and sociobiology》2007,61(8):1311-1319
Protandry reflects the earlier arrival of males than females to the site of reproduction. Such protandry is hypothesised to
arise from sex differences in costs and benefits of early arrival. I investigated temporal patterns of arrival date of male
and female barn swallows Hirundo rustica and temporal patterns of selection to test the hypothesis that sex differences in selection account for sex differences in
arrival date. Mean arrival date of male barn swallows but not of females advanced during the last 33 years, giving rise to
an increasing sex difference in arrival date. Early arrival was favoured by increasingly better survival in males, while females
showed an opposite pattern that did not reach significance, although the effect differed between sexes. Early arrival increased
fecundity in both sexes equally.The sex difference in viability selection in relation to arrival date changed from positive
to negative as the degree of protandry increased in recent years, although there was no similar significant relationship for
fecundity selection. Furthermore, sex differences in viability selection in a given year affected the degree of protandry
in the following year through differential survival of certain phenotypes over others. Finally, temporal changes in sex difference
in viability selection and protandry were related to an increase in the interval between first and second clutches, as the
duration of the breeding season increased because of climatic amelioration. These findings suggest that arrival date is under
divergent selection in the two sexes, providing a mechanism for the evolution of protandry. 相似文献
14.
Theoretical models of the evolution of matrotrophy from a lecithotrophic ancestor suggest that resource availability plays a major role in selective scenarios favoring a change in offspring provisioning. We examined effects of feeding level on embryo provisioning in the livebearing fish Gambusia geiseri, a species with dual provisioning of embryos via both yolk sequestered in large eggs and post-fertilization mother-to-embryo nutrient transfer. Females were fed either once per day or once every three days for three months. Females fed daily had marginally larger brood size, significantly larger embryos, and a higher rate of nutrient transfer (assayed directly by injection of radiolabeled nutrients) than females fed every third day. There was no difference in the size of unfertilized eggs between the feeding treatments. Resource effects on matrotrophic provisioning in G. geiseri suggest that matrotrophy plays an important role in provisioning and allows females to adjust offspring size in response to resource availability. 相似文献
15.
A discrete spatial simulation model is developed to investigate the type and intensity of biological and physical factors influencing the structure of coral communities. The model represents reproduction, growth, and interspecific competition by coral colonies in terms of “ownership” of space in a plot of reef habitat. Using data for several eastern Pacific coral species, the model reproduces observed changes in species composition and diversity during coral community development. Model results suggest that during early successional stages, or in areas that are frequently disturbed, larval colonization and rapid growth are more important than dominance achieved by extracoelenteric digestion or by growing over another coral in acquiring and maintaining possession of reef substrate. In mature communities that remain undisturbed, dominance is the best competitive strategy. Although the model was developed to study natural and man-induced changes in the community dynamics of coral reefs, it could be adapted to study other sessile organisms where spatial pattern is an important influence on the frequency and outcome of biological interactions. 相似文献
16.
《Ecological modelling》2005,188(1):76-92
Mechanistic theories of plant competition developed to explain changes in community structure and dynamics along resource availability gradients have been mostly applied to temperate forests and grasslands where light and nutrients are the two main limiting resources. In contrast, the mechanisms underlying the structure and dynamics of water-limited plant communities have been little explored. Also previous mechanistic models rely either on complex simulators, which are difficult to interpret or on simple conceptual models, which ignore too many critical details. In this study, we develop a model of stand dynamics for light and water-limited forests of intermediate complexity and we provide an analytical framework for its analyses. The model is an individual-based simulator that describes the feedback between transpiration, stomatal function and soil water dynamics with asymmetrical competition for light and water. Trees allocate carbon to three main compartments: shoot, stem and roots. We use the model to explore general patterns that may emerge across levels of biological organization from the leaf to the stand. Model predictions are consistent with a number of features of Mediterranean forests structure and dynamics. At the plant-level the leaf-based tradeoff between carbon gain and water loss expresses as a tradeoff between mortality and growth. This tradeoff explains plant morphological changes in above-ground biomass and root to shoot allocation along a water availability gradient. At the community-level, tradeoffs among carbon acquisition and water loss govern the sign of plant interactions along the gradient. Coexistence among morphological types was not observed for the range of parameters and environmental conditions explored. Overall the model provides an unifying explanation for the observed changes in the sign of plant to plant interactions along environmental gradients as well as a process-based formulation that can be linked to empirical studies. 相似文献
17.
Using circuit theory to model connectivity in ecology, evolution, and conservation 总被引:13,自引:0,他引:13
Connectivity among populations and habitats is important for a wide range of ecological processes. Understanding, preserving, and restoring connectivity in complex landscapes requires connectivity models and metrics that are reliable, efficient, and process based. We introduce a new class of ecological connectivity models based in electrical circuit theory. Although they have been applied in other disciplines, circuit-theoretic connectivity models are new to ecology. They offer distinct advantages over common analytic connectivity models, including a theoretical basis in random walk theory and an ability to evaluate contributions of multiple dispersal pathways. Resistance, current, and voltage calculated across graphs or raster grids can be related to ecological processes (such as individual movement and gene flow) that occur across large population networks or landscapes. Efficient algorithms can quickly solve networks with millions of nodes, or landscapes with millions of raster cells. Here we review basic circuit theory, discuss relationships between circuit and random walk theories, and describe applications in ecology, evolution, and conservation. We provide examples of how circuit models can be used to predict movement patterns and fates of random walkers in complex landscapes and to identify important habitat patches and movement corridors for conservation planning. 相似文献
18.
P. Jivoff 《Behavioral ecology and sociobiology》1997,40(3):175-185
In many species, post-copulatory mate guarding prevents other males from mating with the guarded female. In crabs, males
stay with their mates to protect the female from predators because, in some species, mating occurs when she is soft and vulnerable
after molting. I tested the relative roles of sperm competition and predation on the duration of the post-copulatory association
in the blue crab, Callinectes sapidus. Unpaired females suffered greater predation mortality than paired females and males stayed with the female longer in the
presence of predators than in their absence, suggesting that the post-copulatory association protects females during their
vulnerable period. However, the association may also occur in blue crabs because of sperm competition since spermathecal contents
of females in the field indicate that 12.4% mated twice. Females experimentally mated with two males contained both males
ejaculates and each ejaculate had access to the unfertilized eggs, suggesting that the size of a male's ejaculate influences
his fertilization rate in a multiply-mated female. Males stayed longest in response to a high risk of sperm competition. Longer
post-copulatory associations allowed the first male's ejaculate to harden into a type of sperm plug, which limited the size
of a second inseminator's ejaculate in a non-virgin female as compared with a virgin. Males passed larger ejaculates in the
presence of rivals and when previous ejaculates were in the female spermathecae, another response to sperm competition. Larger
ejaculates may need longer post-copulatory associations before a more effective sperm plug forms. Large males stayed with
the female longer, which is consistent with their ability to pass larger ejaculates than small males and suggests that there
may be costs to minimizing the duration of the post-copulatory association. In the field, associations last long enough to
protect the female during her vulnerable phase and may ensure that the guarding male fertilizes the most eggs in the female,
even if she remates. Thus, the post-copulatory association protects female blue crabs from additional inseminators as well
as from predators.
Received: 23 January 1996 / Accepted after revision: 9 November 1996 相似文献
19.
Skeletonema costatum was grown at different steady-state growth rates in ammonium or silicate-limited chemostats. The culture was perturbed from its steady-state condition by a single addition of the limiting nutrients ammonium or silicate. The transient response was followed by measuring nutrient disappearance of the liliting perturbation experiment indicate that three distinct modes of uptake of the limiting nutrient can be distinguished; surge uptake (V
s
), internally controlled uptake (V
i
), and externally controlled uptake (V
e
). An interpretation of these three modes of uptake is given and their relation to control of uptake of the limiting nutrient is discussed. The uptake rates of the non-limiting nutrients were shown to be depressed during the surge of the uptake of the limiting nutrient. Kinetic uptake parameters, K
s
and V
max, were obtained from data acquired during the externally controlled uptake segment, V
e
. The same V
max value of 0. 12 h-1, was obtained under either silicate or ammonium limitation. Estimates of K
s
were 0.4 g-at NH4-N l-1 and 0.7 g-at Si l-1. Short-term 15N uptake-rate measurements conducted on nitrogen-limited cultures appear to be a combination of V
s
or V
i
, or at lower substrate concentrations V
s
and V
e
. It is difficult to separate these different uptake modes in batch or tracer experiments, and ensuing problems in interpretation are discussed.Contribution No. 882 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA. This work represents portion of three dissertations submitted to the Department of Oceanography, University of Washington, Seattle, in partial fulfillment of the requirements for the Ph.D. degree. 相似文献
20.
Summary Conflicts of interest within and between the sexes are important processes leading to variability in mating systems. The behavioral interactions mediating conflict are little documented. We studied pairs and harems of the snail-shell inhabiting cichlid fish Lamprologus ocellatus in the laboratory. Due to their larger size, males controlled the resource that limited breeding: snail shells. Males were able to choose among females ready to spawn. Females were only accepted if they produced a clutch within a few days of settling. When several females attempted to settle simultaneously the larger female settled first. Females were least aggressive when guarding eggs. Secondary females were more likely to settle when the primary female was guarding eggs. In established harems females continued to be aggressive against each other. The male intervened in about 80% of female aggressive interactions. Male intervention activity correlated with the frequency of aggression among the females in his harem. The male usually attacked the aggressor and chased her back to her own snail shell. When a male was removed from his harem, aggression between females increased immediately and usually the secondary female was expelled by the primary female within a few days. Time to harem break-up was shorter the more mobile the primary females' young were and did not correlate with the size difference between harem females. Male L. ocellatus interfere actively in female conflict and keep the harem together against female interests. Female conflict presumably relates to the cost of sharing male parental investment and to the potential of predation by another female's large juveniles on a female's own small juveniles.Correspondence to: F. Trillmich 相似文献