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Seed Mass (seed + mass)

Distribution by Scientific Domains

Life Sciences	81%
Earth and Environmental Science	16%

Distribution within Life Sciences

Ecology & Organismal Biology	50%
Plant Science	22%
Conservation Science	7%

Selected Abstracts

The Effect of Seed Mass and Gap Size on Seed Fate of Tropical Rain Forest Tree Species in Guyana

PLANT BIOLOGY, Issue 2 2004
L. H. van Ulft
Abstract: For eleven tree species, differing in seed mass, germination success (emergence success for two small-seeded species) and the causes of failure to germinate were studied in the forest understorey and in logging gaps in the tropical rain forests of Guyana. In the forest understorey, germination success increased with seed mass. However, as gap size increased the difference between smaller and larger seeded species diminished because germination success of smaller-seeded species increased slightly, while that of larger-seeded species decreased dramatically. The negative effect of gap size on germination success of larger-seeded species was caused by an increased risk of desiccation with gap size, which was a far more important seed mortality agent for larger than for smaller-seeded species. Generally, seeds of smaller-seeded species suffered more from insect predation and were removed at higher rates than larger-seeded species. On the other hand, larger-seeded species were eaten more by mammals than smaller-seeded species. It is concluded that logging can result in shifts in the species composition in the tropical rain forests of Guyana which are dominated by species with large seeds, since germination success of larger-seeded species is dramatically reduced in large logging gaps. [source]

Seed mass and the competition/colonization trade-off: competitive interactions and spatial patterns in a guild of annual plants

JOURNAL OF ECOLOGY, Issue 1 2004
Lindsay A. Turnbull
Summary 1We used neighbourhood modelling to estimate individual-level competition coefficients for seven annuals growing in limestone grassland over 2 years. We calculated the relative strength of intra- and interspecific competition and related this to differences in seed size and plant size between targets and neighbours. 2Significant differences in the impact of neighbours on each target species were observed in half the models fitted, allowing us to reject a null hypothesis of competitive equivalence. 3In one year we found that as the seed size or plant size of neighbours increased relative to targets, so did their competitive effect. Although this is consistent with the competition/colonization trade-off model the competitive interactions were not sufficiently asymmetric to allow coexistence. In a second year we found only weak interspecific competition and no relationship with plant or seed size. 4We found no overall relationship between competition coefficients and the degree of segregation, contradicting the spatial segregation hypothesis for coexistence. However, segregation was linked to differences in plant traits: when targets were smaller than neighbours the degree of segregation increased with relative neighbour size. 5Most species were positively associated with each other due to a shared preference for otherwise unvegetated patches. The degree of association was negatively correlated with differences in plant and seed size, particularly when interspecific competition was weak. This might reflect (i) decreasing overlap in microhabitat use with increasing trait divergence or (ii) density-dependent mortality. 6Seed size is a key trait within this group of species, determining both competitive and colonizing ability. The presence of such a competition/colonization trade-off undoubtedly stabilizes community dynamics although other mechanisms may also be at work. [source]

Seedling growth and morphology of three oak species along field resource gradients and seed mass variation: a seedling age-dependent response

JOURNAL OF VEGETATION SCIENCE, Issue 3 2010
Ignacio M. Pérez-Ramos
Abstract Question: What is the relative importance of seed mass and abiotic factors in species-specific seedling growth and morphology during the first and the second growing season? How do oak species respond along gradients of these factors? Location: Mediterranean oak forest in southern Spain. Methods: We analysed seedling growth components and morphology of three co-occurring Quercus species (two deciduous and one evergreen). Oak seeds with a wide variety of sizes were sown along broad gradients of abiotic conditions. Intra- and inter-specific differences were evaluated by calibrating maximum likelihood estimators of seedling growth during the first two years of life. Results: We found multiple resources and conditions affecting seedling morphology and biomass allocation. However, the integrative variables of seedling growth , total aboveground biomass and relative growth rate (RGR) , were affected by two main factors: seed mass and light conditions. The relative contribution of these two factors depended strongly on seedling age. Seed mass explained most of the growth and morphological variables during the first year, while light conditions were the best predictor in the second growing season. In contrast, soil factors did not play an important role in seedling growth. We found some evidence of regeneration niche partitioning between oak species along the light gradient, a reflection of their distribution patterns as adults at the study site. Conclusions: We conclude that inter-specific differences in seedling growth, arising from seed size variability and microsite heterogeneity, could be of paramount importance in oak species niche segregation, driving stand dynamics and composition along environmental gradients. [source]

Seed size and response to rainfall patterns in annual grasslands: 16 years of permanent plot data

JOURNAL OF VEGETATION SCIENCE, Issue 1 2009
B. Peco
Abstract Question: Are seed size and plant size linked to species responses to inter-annual variations in rainfall and rainfall distribution during the growing season in annual grasslands? Location: A 16-year data set on species abundance in permanent plots 15 km north of Madrid in a Quercus ilex subsp. ballota dehesa. Methods: At species level, a GLM was used to analyse the effects of various rainfall indices (total autumn rainfall, early autumn rainfall and spring drought) on species abundance residuals with respect to time and topography. We also assessed the importance of seed size and plant size in the species responses at community level using species as data points. Seed mass and maximum stem length were used as surrogates for seed size and plant size, respectively. Results: Seed mass and plant size may explain some of the fluctuations in the floristic composition of annual species associated with autumn rainfall patterns. Species that are more abundant in dry autumns have greater seed mass than those species that are more abundant in wet autumns. Early autumn rainfall seems to favour larger plants. Conclusions: Our empirical results support the hypothesis that autumn rainfall patterns affect the relative establishment capacity of small and large seedlings in annual species. [source]

Germination is related to seed mass in grasses (Poaceae) of the eastern Qinghai-Tibetan Plateau, China

NORDIC JOURNAL OF BOTANY, Issue 5-6 2007
Gaolin Wu
Seed germination is a vulnerable stage in the plant life cycle. Many studies have focused on effects of seed mass on seed germination within a single species, but few studies have compared species of a common habitat. Poaceae plants are widely distributed on the Qinghai-Tibetan Plateau. We investigated how seed mass affect seed germination characters with forty-seven species of Poaceae typical to the alpine meadows of the eastern Qinghai-Tibetan plateau. The frequency of seed mass classes for these species produced a log-normal distribution. The weight of the seeds varied from 0.11 mg to 14.4 mg, and the weight variation nearly reached 103%. There were positive correlations between seed mass and germination index (R=0.331, p<0.05) and between seed mass and germination percentage (R=0.168, p>0.05). The results suggest that seed mass of the Poaceae family on the eastern Qinghai,Tibetan plateau is comparatively log-normal distributed as consistent with other studies, and the larger-seed species have faster germination than the smaller-seed species. Seed mass could be considered as one of the maintenance and construction mechanisms for plant communities in alpine meadows. [source]

Time , size tradeoffs: a phylogenetic comparative study of flowering time, plant height and seed mass in a north-temperate flora

OIKOS, Issue 3 2008
Kjell Bolmgren
Parents face a timing problem as to when they should begin devoting resources from their own growth and survival to mating and offspring development. Seed mass and number, as well as maternal survival via plant size, are dependent on time for development. The time available in the favorable season will also affect the size of the developing juveniles and their survival through the unfavorable season. Flowering time may thus represent the outcome of such a time partitioning problem. We analyzed correlations between flowering onset time, seed mass, and plant height in a north-temperate flora, using both cross-species comparisons and phylogenetic comparative methods. Among perennial herbs, flowering onset time was negatively correlated with seed mass (i.e. plants with larger seeds started flowering earlier) while flowering onset time was positively correlated with plant height. Neither of these correlations was found among woody plants. Among annual plants, flowering onset time was positively correlated with seed mass. Cross-species and phylogenetically informed analyses largely agreed, except that flowering onset time was also positively correlated with plant height among annuals in the cross-species analysis. The different signs of the correlations between flowering onset time and seed mass (compar. gee regression coefficient=,7.8) and flowering onset time and plant height (compar. gee regression coefficient=+30.5) for perennial herbs, indicate that the duration of the growth season may underlie a tradeoff between maternal size and offspring size in perennial herbs, and we discuss how the partitioning of the season between parents and offspring may explain the association between early flowering and larger seed mass among these plants. [source]

Seed mass and seedling establishment after fire in Ku-ring-gai Chase National Park, Sydney, Australia

AUSTRAL ECOLOGY, Issue 4 2004
ANGELA T. MOLES
Abstract Relationships between seed mass and several aspects of plant regeneration ecology were investigated in a post-fire environment in Ku-ring-gai Chase National Park near Sydney, Australia. We found a significant positive relationship between seed mass and time to seedling emergence (P < 0.001) and a strong negative relationship between seed mass and time between emergence and production of the first true leaf (P < 0.001). Surprisingly, we found no relationship between seed mass and seedling establishment (P = 0.21). It seems most likely that this lack of relationship is a result of the many stochastic factors affecting seedling establishment during any given recruitment episode at any given site. A cause of mortality was assigned to 56% of the 781 seedlings that died during the present study. There was no relationship between cause of death and seed mass (P = 0.28). Of the seedlings for which the cause of death was known, 57% were killed by herbivory and 21% were killed by drought. Seedling,seedling competition affected only one species. [source]

Conifers as invasive aliens: a global survey and predictive framework

DIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004
David M. Richardson
ABSTRACT We summarize information on naturalized and invasive conifers (class Pinopsida) worldwide (data from 40 countries, some with remote states/territories), and contrast these findings with patterns for other gymnosperms (classes Cycadopsida, Gnetopsida and Ginkgoopsida) and for woody angiosperms. Eighty conifer taxa (79 species and one hybrid; 13% of species) are known to be naturalized, and 36 species (6%) are ,invasive'. This categorization is based on objective and conservative criteria relating to consistency of reproduction, distance of spread from founders, and degree of reliance on propagules from the founder population for persistence in areas well outside the natural range of species. Twenty-eight of the known invasive conifers belong to one family (Pinaceae) and 21 of these are in one genus (Pinus). The Cupressaceae (including Taxodiaceae) has six known invasive species (4%) in four genera, but the other four conifer families have none. There are also no known invasive species in classes Cycadopsida, Gnetopsida or Ginkgoopsida. No angiosperm family comprising predominantly trees and shrubs has proportionally as many invasive species as the Pinaceae. Besides the marked taxonomic bias in favour of Pinaceae, and Pinus in particular, invasiveness in conifers is associated with a syndrome of life-history traits: small seed mass (< 50 mg), short juvenile period (< 10 year), and short intervals between large seed crops. Cryptomeria japonica, Larix decidua, Picea sitchensis, Pinus contorta, Pinus strobus, and Pseudotsuga menziesii exemplify this syndrome. Many rare and endangered conifer species exhibit opposite characters. These results are consistent with earlier predictions made using a discriminant function derived from attributes of invasive and noninvasive Pinus species. Informative exceptions are species with small seeds (< 4 mg, e.g. Chamaecyparis spp., Pinus banksiana, Tsuga spp. , mostly limited to wet/mineral substrates) or otherwise ,non-invasive' characters (e.g. large seeds, fleshy fruits, e.g. Araucaria araucana, Pinus pinea, Taxus baccata that are dependent on vertebrates for seed dispersal). Most conifers do not require coevolved mutualists for pollination and seed dispersal. Also, many species can persist in small populations but have the genetic and reproductive capacity to colonize and increase population size rapidly. The underlying mechanisms mediating conifer invasions are thus easier to discern than is the case for most angiosperms. Further information is needed to determine the extent to which propagule pressure (widespread dissemination, abundant plantings, long history of cultivation) can compensate for low ,inherent invasiveness'. [source]

Does a latitudinal gradient in seedling survival favour larger seeds in the tropics?

ECOLOGY LETTERS, Issue 10 2004
Angela T. Moles
Abstract The mean size of seeds produced by plants at the equator is two to three orders of magnitude higher than the mean size of seeds produced by plants at 60°. We compiled data from the literature to assess the possibility that this latitudinal gradient in seed size allows species to cope with more difficult seedling establishment conditions in tropical environments. We found no relationship between latitude and seedling survival through 1 week (P = 0.27, n = 112 species). There was also no evidence that a larger seed mass is required to gain a given level of seedling survival in tropical environments (P = 0.37, n = 112 species), and no relationship between latitude and the duration of the juvenile period (P = 0.57, n = 132 species). Thus, our results are not compatible with the idea that seedling establishment is more difficult in the tropics. [source]

A multi-trait test of the leaf-height-seed plant strategy scheme with 133 species from a pine forest flora

FUNCTIONAL ECOLOGY, Issue 3 2010
Daniel C. Laughlin
Summary 1.,Westoby's [Plant and Soil (1998), 199, 213] Leaf-Height-Seed (LHS) plant strategy scheme quantifies the strategy of a plant based on its location in a three-dimensional space defined by three functional traits: specific leaf area (SLA), height, and seed mass. This scheme is based on aboveground traits and may neglect strategies of belowground resource capture if root functioning is not mirrored in any of the axes. How then do fine roots fit into the LHS scheme? 2.,We measured 10 functional traits on 133 plant species in a ponderosa pine forest in northern Arizona, USA. This data set was used to evaluate how well the LHS scheme accounts for the variation in above and belowground traits. 3.,The three most important plant strategies were composed of multiple correlated traits, but SLA, seed mass, and height loaded on separate principle components. The first axis reflected the widely observed ,leaf economics spectrum'. Species at the high end of this spectrum had high SLA, high leaf and fine root nitrogen (N) concentration, and low leaf dry matter content. The second axis reflected variation in seed mass and fine root morphology. Plants at the positive end of this spectrum were plants with large seeds and low specific root length (SRL). The third axis reflected variation in height and phenology. Plants at the positive end of this spectrum were tall species that flower late in the growing season. 4.,Leaf N concentration was positively correlated with fine root N concentration. SRL was weakly positively correlated with SLA. SRL was not correlated with fine root N concentration. Leaf litter decomposition rate was positively correlated with the leaf economics spectrum and was negatively correlated with the height and phenology spectrum. 5.,Leaf traits, seed mass, and height appear to be integrating properties of species that reflect much of the variation in plant function, including root function. Fine root N concentration was positively mirrored by the leaf economics spectrum, and SRL was inversely mirrored by seed mass. The leaf and height axes play a role in controlling leaf litter decomposability, indicating that these strategy axes have important consequences for ecosystem functioning. [source]

Intraspecific seed trait variations and competition: passive or adaptive response?

FUNCTIONAL ECOLOGY, Issue 3 2009
Cyrille Violle
Summary 1The phenotype of offspring depends on the abiotic and biotic environment in which the parents developed. However, the direct effects of competition experienced by parent plants on single-seed traits are poorly documented despite their impact on plant fitness. 2We hypothesize that single-seed traits can differentially respond to the resource deficiencies of parent plants due to competition: seed quality may decrease as seed number does, magnifying the negative effects of competition for offspring (,passive response' hypothesis), or increase and then enhance offspring fitness to offset the reduction in offspring number (,adaptive response' hypothesis). Here we tested these hypotheses for four single-seed traits. We assessed the sensibility of their responses to changes in competition intensity due to species with different competitive effects and to contrasting soil nitrogen conditions. 3In a common-garden experiment, four single-seed traits related to fitness , seed mass, seed nitrogen concentration (SNC), germinability and the timing of germination , were measured on a phytometer species transplanted in 14 different neighbours grown in monoculture with and without soil nitrogen limitation. 4Under nitrogen-limiting conditions, the responses of SNC and of the timing of germination were passive and mainly related to the effects of neighbours on soil nitrogen availability, as shown by the increase in SNC with N-fixing neighbours. Within-individual seed mass variability decreased with increasing competition intensity, as an adaptive response to counterbalance the reduction in seed production. With nitrogen supplementation, competitors had no detectable effect on single-seed traits despite an overall increase in SNC and germination rate, confirming their nitrogen-dependent passive responses to competition. Germinability did not change among treatments. 5The impact of competition on single-seed traits depends on both phytometer trait identity and resource modulation by neighbours. The passive response of seed chemical composition to competitors may magnify the competitive effects on offspring. By contrast, the adaptive response of seed size variability may offset these competitive effects. As a consequence, experiments looking at the fitness consequences of competition should not only consider the effects on fitness parameters of a target plant but also on the offspring. [source]

Differences in seed mass between hydric and xeric plants influence seed bank dynamics in a dryland riparian ecosystem

FUNCTIONAL ECOLOGY, Issue 2 2008
J. C. Stromberg
Summary 1Dryland riparian zones have steep spatial gradients of soil moisture and flood disturbance, and the component hydrogeomorphic surfaces support hydric to xeric plant species. These systems undergo extremes of flood and drought, a dynamic that may select for persistent soil seed banks. We asked if reliance on this strategy differed among plants in three moisture groups (hydric, mesic and xeric), and if patterns were related to diaspore traits. 2We assessed the composition of soil and litter seed banks (emergence method) and extant vegetation along a riparian hydrogradient, and measured seed persistence (using an indirect method) and diaspore mass and shape variance of the component species. 3Hydroriparian species had smaller diaspores than xeroriparian species, corresponding to differences in selective pressures on seedlings in their respective habitats, but the two groups formed persistent seed banks at approximately equal percentages. Persistent seeds were smaller than transient seeds, but within the persistent seed group there was separation between the smaller-diaspored hydrophytes and larger-diaspored xerophytes. 4Distribution patterns of extant vegetation, in concert with diaspore trait differences among moisture-affinity groups, gave rise to divergent spatial patterns of diaspores within the soil: hydroriparian diaspores were abundant not only along wet channel bars but also in deep soils under floodplain forests and shrublands, presumably owing to dispersal by flood waters. Xeroriparian diaspores were largely restricted to the litter and upper soil layers of their drier, higher, floodplain habitats. With increasing depth in the soil of floodplain forests and shrublands, viable diaspores became smaller and rounder, and plant composition shifted from xeroriparian to hydroriparian species. 5The wide distribution of hydroriparian diaspores in floodplain soils influences disturbance dynamics, increasing the probability that ephemeral wetland communities will develop wherever suitable conditions are stochastically created by floods. Persistent seed banks also allow many xeric annuals to be maintained in dryland riparian zones throughout extended drought, similar to processes that occur in desert uplands. [source]

Comparative ecology of seed mass in Psychotria (Rubiaceae): within- and between-species effects of seed mass on early performance

FUNCTIONAL ECOLOGY, Issue 4 2005
H. PAZ
Summary 1Experimental field data and interspecific comparative analyses were used to detect effects of seed mass on seedling performance within and among seven species of Psychotria sown in gaps and shaded rainforest sites. In addition we compared the effects of seed mass within and among species to detect concordance between the two ecological scales. We used two comparative methods: phylogenetically independent contrasts and cross-species correlations. 2Among species, we detected weak evidence of a positive correlation between seed mass and the probability of emergence in the shaded forest, and no effects of seed mass in gaps. 3Among species, no significant correlations between seed mass and either seedling survival or seedling recruitment were found in any habitat. Other variables specific to each subgenus appear to be more important than seed mass in determining survival in the shaded forest. 4There was a negative correlation between seed mass and relative growth rate (RGR) in both habitats. In gaps, small-seeded taxa exhibited particularly high RGR, compensating for the initial advantages of higher seed mass. 5All species studied exhibited recruitment in gaps equal to or higher than that in the shaded forest. However, recruitment success in shaded forest relative to gaps increased with seed mass, indicating a higher affinity for shaded forest among larger-seeded taxa, but this relationship was only detected using PICS analysis. 6.,Correlations between seed mass and seedling mass are similar within and among species, indicating a simple principle of mass transference. In contrast, correlations between seed mass and seedling emergence, seedling survival, seedling recruitment and RGR depend on the scale at which they are observed. [source]

Ecological correlates of seed survival after ingestion by Fallow Deer

FUNCTIONAL ECOLOGY, Issue 2 2005
A. MAARTEN MOUISSIE
Summary 1The survival and retention of seeds was studied by feeding known quantities of seeds of 25 species to four captive Fallow Deer (Dama dama L.). To test for ecological correlates, plant species were selected to represent large variation in seed size, seed shape, seed longevity and habitat fertility. 2Seeds of 24 out of 25 fed plant species survived ingestion and defecation by Fallow Deer. Seed survival ranged between 0·5 and 42% of germinable seeds fed. Time to recover 50% of all seeds defecated by Fallow Deer in faeces averaged 25 h, and ranged from 13 to 38 h. 3Seed survival was negatively related to seed mass (R = 0·65) and variance of unit seed dimensions (R = ,0·56), and positively related to seed longevity (R = 0·40), but not related to habitat fertility. Log10 of (seed mass × variance of seed dimensions) was the best predictor of seed survival (R = ,0·68). 4The ecological correlates of seed survival presented here can help us to estimate the ability of plant species to disperse seeds over long distances. [source]

Greater seed production in elevated CO2 is not accompanied by reduced seed quality in Pinus taeda L.

GLOBAL CHANGE BIOLOGY, Issue 3 2010
DANIELLE A. WAY
Abstract For herbaceous species, elevated CO2 often increases seed production but usually leads to decreased seed quality. However, the effects of increased atmospheric CO2 on tree fecundity remain uncertain, despite the importance of reproduction to the composition of future forests. We determined how seed quantity and quality differed for pine trees grown for 12 years in ambient and elevated (ambient+200 ,L L,1) CO2, at the Duke Forest free-air CO2 enrichment (FACE) site. We also compared annual reproductive effort with yearly measurements of aboveground net primary productivity (ANPP), precipitation (P), potential evapotranspiration (PET) and water availability [precipitation minus potential evapotranspiration (P,PET)] to investigate factors that may drive interannual variation in seed production. The number of mature, viable seeds doubled per unit basal area in high-CO2 plots from 1997 to 2008 (P<0.001), but there was no CO2 effect on mean seed mass, viability, or nutrient content. Interannual variation in seed production was positively related to ANPP, with a similar percentage of ANPP diverted to reproduction across years. Seed production was negatively related to PET (P<0.005) and positively correlated with water availability (P<0.05), but showed no relationship with precipitation (P=0.88). This study adds to the few findings that, unlike herbaceous crops, woody plants may benefit from future atmospheric CO2 by producing larger numbers of seeds without suffering degraded seed quality. Differential reproductive responses between functional groups and species could facilitate woody invasions or lead to changes in forest community composition as CO2 rises. [source]

Sex-specific physiological and growth responses to elevated atmospheric CO2 in Silene latifolia Poiret

GLOBAL CHANGE BIOLOGY, Issue 4 2003
XIANZHONG WANG
Abstract Dioecy is found in nearly half of the angiosperm families, but little is known about how rising atmospheric CO2 concentration will affect male and female individuals of dioecious species. We examined gender-specific physiological and growth responses of Silene latifolia Poiret, a widespread dioecious species, to a doubled atmospheric CO2 concentration in environmentally controlled growth chambers. Elevated CO2 significantly increased photosynthesis in both male and female plants and by a similar magnitude. Males and females did not differ in net photosynthetic rate, but females had significantly greater biomass production than males, regardless of CO2 concentrations. Vegetative mass increased by 39% in males and in females, whereas reproductive mass increased by 82% in males and 97% in females at elevated CO2. As a result, proportionately more carbon was allocated to reproduction in male and female plants at elevated CO2. Higher CO2 increased individual seed mass significantly, but had no effect on the number or mass of seeds per female plant. Our results demonstrated that rising atmospheric CO2 will alter the allocation patterns in both male and female S. latifolia Poiret plants by shifting proportionally more photosynthate to reproduction. [source]

Unravelling the effects of temperature, latitude and local environment on the reproduction of forest herbs

GLOBAL ECOLOGY, Issue 6 2009
P. De Frenne
ABSTRACT Aim, To investigate the effect of temperature, latitude and local environment on the reproductive traits of widespread perennial forest herbs to better understand the potential impacts of rising temperatures on their population dynamics and colonization capacities. Location, Six regions along a latitudinal gradient from France to Sweden. Methods, Within each region, we collected data from three to five populations of up to six species. For each species, several variables were recorded in each region (temperature, latitude) and population (local abiotic and biotic environmental variables), and seed production and germination were estimated. Resource investment in reproduction (RIR) was quantified as seed number × seed mass, while germinable seed output (GSO) was expressed as seed number × germination percentage. We performed linear regression and mixed effect models to investigate the effects of temperature (growing degree hours), latitude and local abiotic and biotic environment on RIR and GSO. Results, Temperature and latitude explained most of the variation in RIR and GSO for early flowering species with a northerly distribution range edge (Anemone nemorosa, Paris quadrifolia and Oxalis acetosella). Reproduction of the more southerly distributed species (Brachypodium sylvaticum, Circaea lutetiana and Primula elatior), in contrast, was independent of temperature/latitude. In the late summer species, B. sylvaticum and C. lutetiana, variation in RIR and GSO was best explained by local environmental variables, while none of the investigated variables appeared to be related to reproduction in P. elatior. Main conclusions, We showed that reproduction of only two early flowering, northerly distributed species was related to temperature. This suggests that the potential reproductive response of forest herbs to climate warming partly depends on their phenology and distribution, but also that the response is to some extent species dependent. These findings should be taken into account when predictions about future shifts in distribution range are made. [source]

Effects of Grazing on Bituminaria bituminosa (L) Stirton: A Potential Forage Crop in Mediterranean Grasslands

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2006
M. Sternberg
Abstract Plant traits of Bituminaria bituminosa, as affected by different intensities of cattle grazing, were studied in a Mediterranean grassland in Israel. B. bituminosa is a widespread Mediterranean perennial legume species that may potentially serve as a fodder crop in Mediterranean grasslands. The aims of the present study were: (i) to evaluate the responses of B. bituminosa to different cattle grazing intensities; (ii) to study functional traits associated with grazing tolerance; and (iii) to evaluate its potential as an alternative forage crop in the region. A total of 100 B. bituminosa plants were monitored in field conditions. During the growing season each individual was sampled five times and the following plant traits were monitored each time: (i) aboveground biomass production, (ii) plant height, (iii) specific leaf area (SLA), (iv) number of flowers, (v) seed mass and size, (vi) tannin concentration in leaves, (vii) total nitrogen in leaves, (viii) fibre concentration in leaves (Neutral Detergent Fiber), and (ix) in vitro dry matter digestibility. The results showed that grazing intensity and history of grazing affected B. bituminosa performance. Plant biomass, height, and flower and seed production were all reduced when plants were exposed to cattle grazing. However, under moderate grazing intensities, its plant cover remained relatively stable indicating a potential tolerance under this stocking rate. The nutritious characteristics of B. bituminosa leaves were good, and the condensed tannins concentration found indicated favourable conditions for digestion. Moreover, the in vitro digestibility studies indicated relatively high values (46,51 %) of digestion. B. bituminosa may be considered as a potential crop for cattle feeding in Mediterranean grasslands. Growing this plant in dense stands in rotational paddocks may provide alternative sources of natural fodder protein, reducing the potential costs of artificial feed supplements. [source]

Large-scale geographical trends in fruit traits of vertebrate-dispersed temperate plants

JOURNAL OF BIOGEOGRAPHY, Issue 4 2003
Arndt Hampe
Abstract Aim, To assess large-scale geographical trends in the character of fleshy, vertebrate-dispersed fruits. Location, Europe between central Sweden and southern Spain. Methods, Analyses of fruit of sixty-three plant species from twenty-nine families were compiled from four regional data sets. Four structural and five chemical fruit traits were analysed intraspecifically to control rigorously for phylogenetic lineage effects. Trends were examined in relation to various biological features of the considered species. Results, Contents of soluble carbohydrate and lipids decreased markedly northwards. Fruit diameter and fresh mass peaked at the wettest site, while the pulp water content remained more constant throughout the gradient than any other fruit trait. Ash content, seed number and seed mass did not change, while the nitrogen content showed conflicting trends. No relation was detected between observed variation in fruit traits and fruit type, fruit colour, ripening season, plant growth form, leaf longevity, or geographical distribution of the considered plant species. Main conclusions, Considerable intraspecific variability exists in vertebrate-dispersed fruits on large geographical scales. Climate presumably affects particularly those traits related to carbon and water gain and storage. Most research on fruit,frugivore interactions has been carried out on small spatial scales and failed to find matchings between frugivore communities and the character of fleshy fruits. I suggest that explicitly addressed large-scale surveys on the geographical variability of fruits and their disperser assemblages are needed to elucidate their spatial patterns and to determine the extent to which fleshy fruit traits are shaped by animals and/or abiotic factors. [source]

Global patterns in plant height

JOURNAL OF ECOLOGY, Issue 5 2009
Angela T. Moles
Summary 1. ,Plant height is a central part of plant ecological strategy. It is strongly correlated with life span, seed mass and time to maturity, and is a major determinant of a species' ability to compete for light. Plant height is also related to critical ecosystem variables such as animal diversity and carbon storage capacity. However, remarkably little is known about global patterns in plant height. Here, we use maximum height data for 7084 plant Species × Site combinations to provide the first global, cross-species quantification of the latitudinal gradient in plant height. 2. ,The mean maximum height of species growing within 15° of the equator (7.8 m) was 29 times greater than the height of species between 60° and 75° N (27 cm), and 31 times greater than the height of species between 45° and 60° S (25 cm). There was no evidence that the latitudinal gradient in plant height was different in the northern hemisphere than in the southern hemisphere (P = 0.29). A 2.4-fold drop in plant height at the edge of the tropics (P = 0.006) supports the idea that there might be a switch in plant strategy between temperate and tropical zones. 3. ,We investigated 22 environmental variables to determine which factors underlie the latitudinal gradient in plant height. We found that species with a wide range of height strategies were present in cold, dry, low productivity systems, but there was a noticeable lack of very short species in wetter, warmer, more productive sites. Variables that capture information about growing conditions during the harsh times of the year were relatively poor predictors of height. The best model for global patterns in plant height included only one term: precipitation in the wettest month (R2 = 0.256). 4. ,Synthesis. We found a remarkably steep relationship between latitude and height, indicating a major difference in plant strategy between high and low latitude systems. We also provide new, surprising information about the correlations between plant height and environmental variables. [source]

Interspecific variation in primary seed dispersal in a tropical forest

JOURNAL OF ECOLOGY, Issue 4 2008
Helene C. Muller-Landau
Summary 1We investigated the relationships of seed size, dispersal mode and other species characteristics to interspecific variation in mean primary seed dispersal distances, mean annual seed production per unit basal area, and clumping of seed deposition among 41 tropical tree species on Barro Colorado Island, Panama. 2A hierarchical Bayesian model incorporating interannual variation in seed production was used to estimate seed dispersal, seed production, and clumping of seed rain for each species from 19 years of data for 188 seed traps on a 50-ha plot in which all adult trees were censused every 5 years. 3Seed dispersal was modelled as a two-dimensional Student's T distribution with the degrees of freedom parameter fixed at 3, interannual variation in seed production per basal area was modelled as a lognormal, and the clumping of seed rain around its expected value was modelled as a negative binomial distribution. 4There was wide variation in seed dispersal distances among species sharing the same mode of seed dispersal. Seed dispersal mode did not explain significant variation in seed dispersal distances, but did explain significant variation in clumping: animal-dispersed species showed higher clumping of seed deposition. 5Among nine wind-dispersed species, the combination of diaspore terminal velocity, tree height and wind speed in the season of peak dispersal explained 40% of variation in dispersal distances. Among 31 animal-dispersed species, 20% of interspecific variation in dispersal distances was explained by seed mass (a negative effect) and tree height (a positive effect). 6Among all species, seed mass, tree height and dispersal syndrome explained 28% of the variation in mean dispersal distance and seed mass alone explained 45% of the variation in estimated seed production per basal area. 7Synthesis. There is wide variation in patterns of primary seed rain among tropical tree species. Substantial proportions of interspecific variation in seed production, seed dispersal distances, and clumping of seed deposition are explained by relatively easily measured plant traits, especially dispersal mode, seed mass, and tree height. This provides hope for trait-based generalization and modelling of seed dispersal in tropical forests. [source]

Carbohydrate storage enhances seedling shade and stress tolerance in a neotropical forest

JOURNAL OF ECOLOGY, Issue 2 2007
JONATHAN A. MYERS
Summary 1To survive in forest understoreys, seedlings must depend on carbohydrate reserves when they experience negative carbon balance imposed by occasional light reduction and tissue loss to herbivores and diseases. We present the first experimental evidence in support of this hypothesis, using seven woody neotropical species. 2We transplanted seedlings that had recently expanded their first photosynthetic cotyledon or leaf to the forest understorey (1% of full sun) and quantified initial biomass and total non-structural carbohydrate (TNC) in stems, roots and storage cotyledons. We then randomly assigned seedlings to control and two stress treatments: light reduction (0.08% of full sun for 8 weeks) and complete defoliation. 3First-year survival of control seedlings, a comparative measure of shade tolerance, differed widely among species. The two stress treatments reduced survival and relative growth rates (RGR) of all species. Shade-tolerant species were little impacted by the stress treatments, whereas the two least shade-tolerant species experienced 100% mortality. 4In all treatments, 8-week and first-year survival was positively correlated with initial TNC pool size in stems and roots. By contrast, survival was generally not correlated with initial TNC concentration in any organ, TNC pools in cotyledons, seed mass or seedling biomass. 5TNC in stems and roots, but not in cotyledons, decreased in response to light reduction and defoliation over 8 weeks. Leaf area recovery of defoliated seedlings was positively correlated with initial TNC pools in stems and roots. 6First-year survival in each treatment was negatively correlated with 0,8 week RGR of control seedlings, suggesting higher stress tolerance of species with inherently slow growth rates in shade. RGR of control seedlings from 0 to 8 weeks was negatively correlated with initial TNC pools, but not concentrations, in stems and roots. After 8 weeks, RGR was positive for all species, without clear relationships with survival or TNC. 7We conclude that carbohydrate storage in stems and roots enhances long-term survival in shade by enabling seedlings to cope with periods of biotic and abiotic stress. Carbohydrate storage is a key functional trait that can explain species differences in growth and survival that lead to species coexistence through niche assembly processes and life-history trade-offs. [source]

Seedling survival and seed size: a synthesis of the literature

JOURNAL OF ECOLOGY, Issue 3 2004
ANGELA T. MOLES
Summary 1Large-seeded species have long been known to have higher survivorship during establishment than small-seeded species. Here, we assessed the size of this advantage by compiling published data on survival through seedling emergence, seedling establishment and sapling establishment. 2We found no relationship between seed mass and survival through the transition from viable seed in or on the soil to newly emerged seedlings (P = 0.47, n = 33 species). 3Synthesis of data from experimental studies on the advantages of large-seeded species establishing under particular hazards (such as shade, drought or herbivory) confirmed that seedlings of large-seeded species perform better than those of small-seeded species in most situations. However, the magnitude of this advantage was not sufficient to counterbalance the greater number of seeds produced by small-seeded species m,2 of canopy outline year,1. 4Synthesis of data from field studies of populations under natural conditions also showed that large-seeded species have higher survival through early seedling establishment than small-seeded species (P = 0.006, n = 112 species). However, the magnitude of this advantage would only be sufficient to counterbalance the greater number of seeds produced by small-seeded species m,2 of canopy outline year,1 if mortality continued at the same rate for some time. 5The time required for a species with 10-fold larger seeds to recoup the advantage gained by a smaller-seeded species during seed production ranged from 8.8 weeks for the smallest seeded species in the data set, up to an implausible 4.2 years for the largest-seeded species. Thus, while large-seeded species do have a survival advantage over small-seeded species during seedling establishment, the available evidence suggests that advantages must also accrue during other stages in the life cycle. One possibility is that the greater seed production of small-seeded species (m,2 of canopy outline year,1) is partly offset by larger canopies and longer reproductive life spans in large-seeded species. [source]

Positive and negative consequences of salinity stress for the growth and reproduction of the clonal plant, Iris hexagona

JOURNAL OF ECOLOGY, Issue 5 2003
Peter A. Van Zandt
Summary 1Salinization is a growing environmental stress in wetland ecosystems world-wide. Several models have been proposed that predict clonal plant responses to stress, including that environmental stress stimulates sexual reproduction. 2We conducted a common-garden experiment to investigate the effects of salinity on 10 natural populations of Iris hexagona, a clonal perennial endemic to freshwater and brackish wetlands of the North American Gulf Coast. 3Salinity reduced vegetative growth but either increased or had neutral effects on sexual reproduction, consistent with the clonal stress hypothesis. Salinity of 4 µg g,1 more than doubled the number of seeds produced compared with freshwater controls, but flower number and seed mass were unaffected. 4Salinity reduced total below-ground mass by nearly 50% compared with controls, with no significant change in rhizome numbers. 5Plants from 10 randomly selected I. hexagona populations differed dramatically in growth and reproduction, independent of salinity. Total biomass that accumulated over the 20-month experiment ranged across all treatments from 52 to 892 g, and flower numbers varied from 2.3 to 11.3 per replicate. 6Populations did not respond differently to salinity, except with respect to above- : below-ground ratios, thus providing no conclusive evidence for local adaptation to salinity stress. 7Our results concur with published models of plant reproductive strategies in variable environments, in that environmental stress stimulated sexual reproduction at the expense of growth. However, these models do not predict the observed sharp decline in seed production at near lethal salinity levels. [source]

Reduced fecundity and offspring performance in small populations of the declining grassland plants Primula veris and Gentiana lutea

JOURNAL OF ECOLOGY, Issue 1 2000
Marc Kéry
Summary 1,We studied reproduction and offspring performance in relation to population size in the declining self-incompatible perennials Primula veris and Gentiana lutea. In both species, reproduction was strongly reduced in small populations, where plants produced fewer seeds per fruit and per plant. Total seed mass per plant was higher in large populations, but individual seeds were smaller, indicating a trade-off between seed number and size. Reproduction was depressed most strongly in populations consisting of less than c. 200 (P. veris) and c. 500 plants (G. lutea), respectively. 2,The inclusion of plant size (an integrated measure of habitat quality) in the statistical models did not change the relationships between fecundity and population size. Pollen limitation or inbreeding depression in small populations are therefore more likely explanations for these patterns than is habitat quality. 3,Germination rate and survival of seedlings in a common environment was not related to population size in either species, although P. veris developed into larger rosettes when seeds were derived from large populations. This suggests that inbreeding depression occurs in small populations of P. veris. 4,In a factorial fertilizer-by-competition experiment with P. veris, offspring from larger populations grew significantly larger and responded more strongly to fertilizer. For this declining species genetic deterioration as a result of habitat fragmentation may therefore aggravate the effects of environmental changes such as habitat eutrophication. 5,Our results suggest that small populations may face an increased short-term risk of extinction because of reduced reproduction, and an increased long-term risk because they are less able to respond to environmental changes. [source]

Seedling growth and morphology of three oak species along field resource gradients and seed mass variation: a seedling age-dependent response

A community-level test of the leaf-height-seed ecology strategy scheme in relation to grazing conditions

JOURNAL OF VEGETATION SCIENCE, Issue 3 2009
Carly Golodets
Abstract Question: Is the assumption of trait independence implied in Westoby's (1998) leaf-height-seed (LHS) ecology strategy scheme upheld in a Mediterranean grazing system dominated by annuals? Is the LHS approach applicable at the community level? Location: Northern Israel. Methods: LHS traits (specific leaf area [SLA], plant height and seed mass), and additional leaf traits (leaf dry matter content [LDMC], leaf area, and leaf content of nitrogen [LNC], carbon [LCC], and phosphorus [LPC]), were analyzed at the species and community levels. Treatments included manipulations of grazing intensity (moderate and heavy) and protection from grazing. We focused on species comprising 80% of biomass over all treatments, assuming that these species drive trait relationships and ecosystem processes. Results: At the species level, SLA and seed mass were negatively correlated, and plant height was positively correlated to LCC. SLA, seed mass, and LPC increased with protection from grazing. At the community level, redundancy analysis revealed one principal gradient of variation: SLA, correlated to grazing, versus seed mass and plant height, associated with protection from grazing. We divided community functional parameters into two groups according to grazing response: (1) plant height, seed mass, LDMC, and LCC, associated with protection from grazing, and (2) SLA, associated with grazing. Conclusions: The assumption of independence between LHS traits was not upheld at the species level in this Mediterranean grazing system. At the community level, the LHS approach captured most of the variation associated with protection from grazing, reflecting changes in dominance within the plant community. [source]

Seed size and response to rainfall patterns in annual grasslands: 16 years of permanent plot data

The effect of twig architecture and seed number on seed size variation in subtropical woody species

NEW PHYTOLOGIST, Issue 4 2009
Hong Chen
Summary ,,This study aims to determine the effect of twig (current year shoot) size on seed size variation and to test whether a seed size vs number tradeoff occurs for the twigs of subtropical broad-leaved species. ,,Fruit-bearing twigs were sampled for 55 woody species (including 33 evergreen and 22 deciduous dicot species) from a southwest Chinese forest. Twig size, fruit size and number, and seed size and number were measured for each species. The relationships among these functional traits were determined both across species and across correlated phyletic divergences. ,,Total fruit mass and total seed mass were positively correlated with twig size. Seed size was positively associated with fruit size, which was, in turn, positively correlated with twig diameter, but negatively correlated with the ratio of twig length to diameter. The effect of twig size on seed size variation was not significant, possibly as a result of the large variation in seed number per fruit. Cross-species and across-phyletic divergence analyses revealed that seed size was negatively and isometrically correlated with seed number per twig mass in both the evergreen and deciduous species groupings, demonstrating the existence of tradeoff between seed size and number. ,,A seed size vs number tradeoff is detectable in the twigs of woody species. Comparatively little of the variance in seed size was attributable to twig size variation. [source]