bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nutrient limitations and their implications on the effects of atmospheric deposition in coastal dunes; lime‐poor and lime‐rich sites in the Netherlands
Authors: Kooijman A. M. , Dopheide J. C. R. , Sevink J. , Takken I. , Verstraten J. M. 
Published: May 2003

1 A survey of plant and soil parameters was carried out in dry dune grasslands along the Dutch coast in the lime‐ and iron‐poor Wadden district and initially lime‐ and iron‐rich Renodunaal district, in order to detect differences in nutrient availability related to soil characteristics and potential sensitivity to atmospheric deposition of nitrogen. 2 Plant biomass and phosphorus pools in the shoot were higher in the Wadden district. The low foliar nitrogen concentrations and nitrogen/phosphorus ratios in the Wadden district suggested nitrogen‐limitation, while in the Renodunaal district there appeared to be a balanced supply of both nitrogen and phosphorus. 3 Soil pH, soil organic matter, soil nitrogen and phosphorus concentrations and total amounts were generally higher in the Renodunaal district. In both districts mineral phosphorus decreased with acidification and phosphorus oxalate (iron and aluminium bound) increased. 4 In the Wadden district iron is present primarily in iron–organic matter complexes, which leads to reversible binding of phosphorus. In the Renodunaal district large amounts of iron (hydr)oxides occur and at high pH may contribute to reversible phosphorus‐sorption, but at low pH this probably leads to immobilization of phosphorus. 5 While pools of soil phosphorus are low in the Wadden district, the phosphorus availability may be relatively high due to the comparatively loose nature of phosphorus‐sorption. As a result the area may be nitrogen‐limited and grass‐encroachment may thus have resulted from atmospheric deposition of nitrogen. 6 In the Renodunaal district, atmospheric deposition probably only accelerates grass‐encroachment, because deposition of acid and nitrogen increases the availability of both nitrogen and phosphorus and maintains the ‘co‐limitation’.
Effects of supplementary feeding on growth and reproduction of three carnivorous plant species in a subarctic environment
Authors: Thorén L. Magnus , Karlsson P. Staffan 
Published: May 2003

1 The effect of supplementary feeding on growth and reproduction of three carnivorous plants species was investigated over a 6‐year period. Pinguicula alpina, P. villosa and P. vulgaris populations growing at two altitudes in a subarctic environment were fed with fruit flies (Drosophila melanogaster). 2 Fed plants increased in size relative to control plants during the first years. Subsequently a stable size difference between feeding levels was established. The weight of the over‐wintering part was higher in fed plants than in control plants. 3 The flowering frequency (i.e. proportion of plants in a population carrying flowers) was also higher in the fed plants. The proportion of flowering plants increased in the feeding treatment compared to control plants during more‐or‐less the whole experimental feeding period (5–6 years). Seed production also increased slowly in response to feeding. 4 No feeding effect on nitrogen and phosphorus concentrations in seeds and over‐wintering parts was found. 5 In most characteristics the high‐altitude populations were less responsive than populations growing at low altitude. In the high‐altitude population reproduction failed repeatedly, suggesting that seed output may be more dependent on abiotic factors than on resource availability in cold environments. 6
Pinguicula villosa and P. vulgaris used the new resources the same summer for increased leaf rosette growth and current reproduction, showing these species to be income breeders, while the third species (P. alpina) allocated a larger proportion to storage and future reproduction, characteristic of a capital breeder.
Quantitative representation of local forest composition in forest‐floor pollen assemblages
Authors: Jackson Stephen T. , Kearsley Jennifer B. 
Published: May 2003

1 We compared modern pollen assemblages from 60 moss polster sites in northern New York with forest composition data within 20–120 m of the sites using extended R‐value (ERV) models, which correct for non‐linearities arising from use of pollen percentage data. Our sites were concentrated in two regions, one dominated by Tsuga and hardwood (Acer, Betula, Fagus) forests, and the other by Tsuga, Pinus, Betula, Acer and Quercus forests. 2 Our results confirm that forest‐floor pollen assemblages are dominated by pollen originating from trees growing more than 20 m from the site of deposition. However, our results suggest that background pollen percentages were overestimated by Jackson & Wong in 1994, owing to unusually high Pinus pollen production in the year of their sampling. 3 Expansion of our vegetation sampling radius from 20 to 120 m resulted in modest but consistent improvement in model fit and a decrease in background pollen percentages. 4 ERV model parameters (slope and background) differed substantially between the two study regions, primarily owing to differences in background pollen productivity and dispersal from regional sources. 5 High background pollen percentages may lead to poor estimation of calibration parameters in regions of complex vegetation patterns. Expansion of the vegetation sampling radius to reduce the background component may lead to better parameter estimates. 6 Calibration of pollen–vegetation relationships requires definition of the vegetation term so that it approximates the vegetation sampled by the pollen assemblages. Critical challenges are to define better the appropriate vegetation sampling area and distance‐weighting functions for application to pollen–vegetation calibration.
An experimental test of limits to tree establishment in Arctic tundra
Authors: Hobbie Sarah E. , Chapin F. Stuart 
Published: May 2003

1 Five treeline species had low seed germination rates and low survivorship and growth of seedlings when transplanted into Alaskan tundra. Seed germination of all species increased with experimental warming, suggesting that the present treeline may in part result from unsuccessful recruitment under cold conditions. 2 Growth, biomass and survivorship of seedlings of treeline species transplanted into tundra were largely unaffected by experimental warming. However, transplanted seedlings of three species (Betula papyrifera, Picea glauca and Populus tremuloides) grew more when below‐ground competition with the extant community was reduced. All three measures of transplant performance were greater in shrub tundra than in the less productive tussock or heath tundra. Establishment of trees in tundra may thus be prevented by low resource availability and competition. 3 Two species (Alnus crispa and Populus balsamifera) had low seed germination and survivorship of germinated seeds; transplants of these species did not respond to the manipulations and lost biomass following transplanting into tundra. Isolated populations of these two species north of the present treeline in arctic Alaska probably became established during mid‐Holocene warming rather than in recent times. 4 Of all the species studied here, Picea glauca was the most likely to invade intact upland tundra. Its seeds had the highest germination rates and it was the only species whose seedlings survived subsequently. Furthermore, transplanted seedlings of Picea glauca had relatively high survivorship and positive growth in tundra, especially in treatments that increased air temperature or nutrient availability, two factors likely to increase with climate warming.
Sources and consequences of seed mass variation in Banksia marginata (Proteaceae)
Authors: Vaughton Glenda , Ramsey Mike 
Published: May 2003

1 We examined the sources and consequences of seed mass variation in Banksia marginata occurring in fire‐prone heath on nutrient‐poor soils to determine factors influencing seed size and possible fitness benefits of large seeds. 2 Individual seed mass varied fivefold. Variation occurred among populations (29% of total), among years (10%) and among plants (plants, 6%; year × plants, 13%), but was most pronounced within plants (42%). Within plants, seed mass variation was greater within infructescences (35%) than among infructescences (7%). 3 Seed mass variation within infructescences was not related to whether follicles contained one or two seeds. Seed mass was also unaffected by ovule position within follicles and follicle position within infructescences. 4 Seed mass variation among infructescences and plants was related to the limited availability of nutrient resources during seed provisioning. Mean seed mass was negatively related to seed number per infructescence and per plant. When resources decreased late in the flowering season and after defoliation, seed mass declined by 7–10% and seed number by 31–45%. When resources increased after inflorescence removal, seed mass increased by 8% but seed number was unaffected. Plants thus had only a limited capacity to maintain seed mass by adjusting seed number when resources varied. 5 The N and P contents of seeds (mg seed−1) increased linearly with seed mass, indicating costs of producing larger seeds in terms of limited environmental nutrients. 6 Seedling size increased with seed mass, implying fitness benefits of larger seeds in terms of increased seedling establishment on nutrient‐poor soils. Seed mass had little or no effect on seed germination, relative growth rates and root:shoot ratios. 7 Although stabilizing selection should eliminate seed mass variation occurring within plants, such variation persists because resource constraints limit the ability of plants to control individual seed size.
Variation in the demography of a woodland understorey herb (Primula vulgaris) along the forest regeneration cycle: projection matrix analysis
Authors: Valverde Teresa , Silvertown Jonathan 
Published: May 2003

1 Gaps in the forest canopy allow establishment of many understorey species. As gaps close, their demographic behaviour is affected by changing environmental conditions. A demographic analysis of Primula vulgaris populations in forest patches with varying canopy openness was carried out to investigate the effect of forest canopy dynamics on the demography of this forest understorey herb. 2 Eight P. vulgaris populations across a range of light conditions were studied in three deciduous temperate forests in Britain. Demographic data were collected in each population during summer 1992, 1993 and 1994, and stage‐based population projection matrices were built to describe their demography for two growth periods (1992–93 and 1993–94). 3 Population growth rate (λ) varied from 0.97 to 1.98 in 1992–93, and from 0.88 to 1.23 in 1993–94. There was a significant positive correlation between λ and diffuse light for the two periods studied: generally, population growth rate was lower in darker patches, implying that populations decline as the canopy closes. Lower λ‐values in 1993–94 were the result of increased mortality and decreased fecundity compared to 1992–93. In most cases the observed population structures were significantly different from the calculated stable‐stage distributions. 4 Sensitivity analysis showed that λ was most sensitive to changes in matrix transitions that corresponded to growth from small to adult stages, especially those that implied fast growth. Elasticity analysis revealed that the contribution of fecundity elements to λ was small, but populations in brighter patches showed comparatively higher fecundity elasticities than populations under the closed canopy. High elasticities corresponded to the entries that implied growth (especially in brighter patches) or persistence in adult categories (predominantly in darker patches). 5 The observed variation in the demography of P. vulgaris in different patches along the forest regeneration cycle stresses the importance of studying the variation in plant population dynamics across the range of habitat patches in which the plant naturally occurs.
A comparative study of the seedbanks of heathland and successional habitats in Dorset, Southern England
Authors: Mitchell R. J. , Marrs R. H. , Auld M. H. D. 
Published: May 2003

1 Many areas of lowland heaths are being lost due to invasion by Betula spp., Pinus sylvestris, Pteridium aquilinum, Rhododendron ponticum and Ulex europaeus. One of the factors influencing the success of restoration of heathland on such sites will be the content of their viable seedbanks. 2 Ten heathland areas in the Poole Basin area of Dorset, where succession to one or more of the above species had occurred were studied. The viable seedbanks of the successional sites were compared with those of nearby heathland using Canonical Discriminant Analysis. 3 The seedbanks of all the successional stages were significantly different from the seedbank of the heath. 4 The seedbanks from the Pinus sylvestris and Pteridium aquilinum successional stages contained significantly lower numbers of heathland species than did the heathland seedbank, although few non heathland species were present. 5 The seedbanks from the Betula spp., Rhododendron ponticum and Ulex europaeus successional sites contained both significantly lower numbers of heathland species and significantly higher numbers of non heathland species than the heathland seedbank. 6 The results are discussed in relation to the restoration of heathland on successional sites and the use of the seedbank as a source of propagales for the establishment of heathland species.
Seedling growth response to added nutrients depends on seed size in three woody genera
Authors: Milberg Per , Pérez‐Fernández María A. , Lamont Byron B. 
Published: May 2003

1 We tested whether seedlings of small‐seeded species were more reliant on soil nutrients than large‐seeded ones by growing 21 species from three woody genera (Eucalyptus, Hakea and Banksia) along a gradient of nutrient availability. 2 At very low nutrient availability, larger seeds produced larger seedlings. This was seen especially among the eucalypts, but the difference was eliminated at optimal soil nutrient levels. Hakea species with large seed mass, and all Banksia species, appeared unable to exploit additional soil nutrients for growth, whatever the level supplied. 3 Larger seeds tended to have proportionately higher contents of N, P and K and, under nutrient‐poor conditions, supplied more of these to their seedlings, although at a diminishing rate. 4 We suggest that large‐seededness could be an adaptation to the high‐light, nutrient‐impoverished habitats in which these species occur by providing the seedling with the mineral nutrients, rather than carbon‐based metabolites, needed for maximizing initial root growth. Reaching reliable moisture before summer (drought avoidance) is an alternative strategy to physiological tolerance of drought.
Recruitment rates in forest plots: Gf estimates using growth rates and size distributions
Authors: Kohyama Takashi , Takada Takenori 
Published: May 2003

1 In censuses of tree populations in permanent plots, short census intervals and small population size lead to uncertainty in the observed recruitment rate of a minimum size. Increasing the census interval, however, underestimates the rate because of unrecorded ‘recruit and die’ events. 2 We propose a new Gf procedure for estimation of recruitment rates. Recruitment rate per area is obtained by multiplication of the density in the smallest size class (f) and the average size growth rate in that class (G) divided by the width of the class. This procedure is valid when the size distribution of the population examined is continuous with size. 3 When tree size structure is negative‐exponentially distributed, as is often the case in natural rain forest populations, the Gf estimate of the recruitment rate for a given size class was least biased close to the midpoint size of this class. 4 Gf estimates agreed well with census estimates of recruitment rate from permanent plots in rain forests. A tendency for Gf estimates to be larger than census estimates disappeared when census estimates were corrected for mortality after recruitment. 5 The effects of plot size, census interval and variation in growth rate on estimates of recruitment rate were simulated using model populations. Small plot size caused substantially more among‐plot deviation for the census count of recruitment events than for the Gf estimate. The census recruitment rate also showed larger variation among plots for shorter intervals than the Gf estimate, which was independent of census interval. The Gf estimates were therefore more accurate than census counts in many situations. More than several tens of trees were needed in a size class to allow a reliable Gf estimates.
Survival and growth of woody plant seedlings in the understorey of floodplain forests in South Carolina
Authors: Jones Robert H. , Sharitz Rebecca R. 
Published: May 2003

1Survival and height growth of permanently tagged understorey seedlings in four river floodplain forests in South Carolina were monitored for 8 years. Regression models were used to determine if a common survival pattern emerged and if the pattern varied according to species, spatial location, time, seedling size and seedling growth.2For most of the populations, per capita survival was initially poor but increased steadily with age. A few populations, however, had relatively high survival rates for 1–3 years after establishment, or brief periods (1–2 years) with much lower survival. Although the underlying survival function was best described by a negative power curve, a log‐logistic model also fit the data and provided more versatility for fitting individual populations.3Significant differences in general survival pattern were found among species, sites (forests), years of establishment (cohorts), and all two‐way interactions of species, site and cohort. Species differences were large. Spikes in mortality for individual species and cohorts were synchronized within sites and to a lesser degree among sites. In some sites, weak relationships were noted between mortality and peak river discharge during summer (negatively correlated) and winter (positively correlated).4Species differed strongly in their initial height, but effects of cohort and site on height were also significant as were all two‐way interactions of species, site and cohort. During the 8 years of this study, very few seedlings grew taller than 30 cm. For most species, taller seedlings had greater per capita survival. Height growth, however, was not consistently related to survival. Since mean size of survivors changed little with time, age may be a better variable than size to use in models of survival.5Simulation models could probably be developed using a log‐logistic function that includes (in order of importance): seedling age, species, intensity of winter floods (some sites) and occurrence of summer droughts (some sites).
Treefall gap size effects on above‐ and below‐ground processes in a tropical wet forest
Authors: Denslow Julie S. , Ellison Aaron M. , Sanford Robert E. 
Published: May 2003

1We examined the effects of variation in gap size on above‐ and below‐ground light and nutrient processes in a tropical wet forest in Costa Rica.2Trees were felled to create canopy openings ranging in size from 65 to 611 m2. Following treefall, we measured initial litter mass in the crown zone of six gaps. During the subsequent year, we measured litter decomposition rate and light levels as well as NH4‐N, NO3‐N and PO4‐P levels in surface soils, soil moisture and fine root mass. We also measured growth rates of fertilized and non‐fertilized plants of four species ofMiconia(Melastomataceae) to assess nutrient limitation to plant growth in large gaps.3Light levels in the centres of gaps were significantly related to size of the canopy opening. After 1 year, light levels near the ground in larger openings (35–40% full sunlight immediately after treefall) declined to levels similar to those in smaller gaps (10–20%).4Although canopy opening had only slight effects on soil NH4‐N, NO3‐N pools were significantly greater in gaps than in understorey at both sites. The effect was positively correlated with gap size. Extractable PO4‐P was also greater in gaps than in adjacent understorey, although the difference did not vary as a function of gap size. In three of six gaps, fine root biomass was less in gaps than in adjacent understorey.5Of four species ofMiconia, onlyM. affinis, a small tree common in early secondary forests, grew significantly faster in fertilized than in non‐fertilized treatments in three large gaps.6Our data suggest that higher nutrient pools in surface soils of treefall gaps may result from decomposition and mineralization of the large mass of fresh litter from the fallen tree. While growth rates of shade‐tolerant rain forest trees and shrubs are not much affected by the increased nutrient availability even at high light levels, growth rates of pioneer or high‐light demanding species may be enhanced by increased above‐ and below‐ground resources.
A 38‐year study of relations between weather and vegetation dynamics in road verges near Bibury, Gloucestershire
Authors: Dunnett N. P. , Willis A. J. , Hunt R. , Grime J. P. 
Published: May 2003

1 The Bibury long‐term data set contains information on annual fluctuations in the abundance of over 100 grasses and forbs in roadside verge vegetation over the period from 1958 to the present. Monitoring has been carried out every July by the same individual. The data set represents a unique long‐term record of the dynamics of a complete plant community. 2 Records for the most abundant taxa (including bare ground and litter) were used to determine the effect of climate variability on the year‐to‐year performance of the selected species. Residuals about the long‐term mean log biomass of each species (de‐trended where the species showed a significant increase or decrease in abundance over time) were correlated against indices of interannual climate variability. Plant and weather records were compared over 3‐month seasonal periods (March–May, June–August, September–November, December–February) or 6‐month seasonal periods (March–August, September–February), with time lags of 0, 1 and 2 years. 3 Principal components analysis (PCA) was used to formulate annual weather indices, using either conventional weather variables (temperature, rainfall and sunshine) or the Lamb catalogue of daily weather types. 4 Between 5% and 70% more correlations were observed than might be expected to occur by chance, depending on the season and the PCA index, indicating markedly non‐random plant–weather relationships. Total vegetation production was positively correlated with minimum spring temperature. The distribution of correlations was generally evenly distributed across the three lag periods. 5 In general, those species favoured by environmental stress or disturbance were promoted following warm dry springs and summers, whereas those favoured by more productive conditions were promoted following a wet growing season.