Home About us Contact
|
Home About us Contact | ||
|
|
||
Grassland Plants (grassland + plant)
Terms modified by Grassland Plants Selected AbstractsSoil animals influence microbial abundance, but not plant,microbial competition for soil organic nitrogenFUNCTIONAL ECOLOGY, Issue 5 2004L. COLE Summary 1In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2- 13C- 15N) between a grassland plant, Agrostis capillaris, and the soil microbial biomass, to determine how soil fauna and their diversity influence plant,microbial competition for organic N. 2We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the microbial biomass, due to the effect of animal grazing on the microbial biomass, and hence its ability to sequester N. 3Certain individual species of Collembola influenced the microbial community of the soil. Folsomia quadrioculata reduced microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on microbial 15N. 5Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6Our data suggest that, while single species and variations in diversity of microarthropods influence microbial abundance in soil, there is no effect on microbial or plant uptake of N. Overall, these data provide little support for the notion that microbial-feeding soil animals are regulators of microbial,plant competition for N. [source] Restoration of species-rich grassland on arable land: assessing the limiting processes using a multi-site experimentJOURNAL OF APPLIED ECOLOGY, Issue 2 2002Richard F. Pywell Summary 1Agricultural intensification has resulted in the reduction and fragmentation of species-rich grasslands across much of western Europe. 2We examined the key ecological processes that limit the creation of diverse grassland communities on ex-arable land in a multi-site experiment over a wide variety of soil types and locations throughout lowland Britain. 3The results showed it was possible to create and maintain these communities successfully under a hay-cutting and grazing management regime. Furthermore, there was a high degree of repeatability of the treatment effects across the sites. 4Lack of seed of desirable species was the key factor limiting the assembly of diverse grassland communities. Sowing a species-rich seed mixture of ecologically adapted grassland plants was an effective means of overcoming this limitation. Community assembly by natural colonization from the seed bank and seed rain was a slow and unreliable process. However, there was no evidence to suggest that sowing a species-poor grass-dominated seed mixture made the vegetation any less susceptible to colonization by desirable species than allowing natural regeneration to take place. 5Deep cultivation caused significant reductions in soil P and K concentrations across the sites. This had a significant beneficial effect on the establishment and persistence of sown forbs in all years. It also resulted in a significant reduction in the number of unsown weedy grasses. However, for both variables these differences were very small after 4 years. 6Sowing a nurse crop significantly reduced the number of unsown grass species, but had no beneficial effect on the establishment of desirable species. 7Treatments sown with the species-rich seed mixture following deep cultivation corresponded most closely to the specified target communities defined by the UK National Vegetation Classification. Natural regeneration and treatments sown with the species-poor seed mixture were much less similar to the target. The sites on circum-neutral soils achieved the greatest degree of similarity to the target. Those on calcareous and acid soils failed to achieve their targets and most closely resembled the target for neutral soils. This reflected the poor performance of the sown preferential species for these communities. [source] Gene diversity in a fragmented population of Briza media: grassland continuity in a landscape contextJOURNAL OF ECOLOGY, Issue 1 2006HONOR C. PRENTICE Summary 1We investigated patterns of allozyme variation in demes of the grass Briza media in semi-natural grassland fragments within a mosaic agricultural landscape on the Baltic island of Öland. In the study area, Briza is both a characteristic species of old pastures and an early colonizer of young grasslands developing on previously forested or arable sites. 2Generalized linear models revealed that descriptors of both present landscape structure and past grassland history are significant determinants of genetic variation in the Briza demes. Genetic structure and levels of within-deme diversity are influenced by the size of grassland fragments, the type of habitat surrounding the grasslands, the size/spatial extent of the demes, the geographic position of the demes and the historical continuity of the grassland fragments. 3Gene diversity (H) was higher in demes from grassland polygons with a high proportion of adjacent grassland, higher in the more extensive demes, and decreased northwards within the study area. 4The negative association between the inbreeding coefficient (FIS) and grassland continuity is interpreted in terms of a two-stage colonization process: recruitment into young grasslands leads initially to spatial patchiness, but subsequent selection in maturing pastures occurs within an increasingly uniform and dense sward. 5Despite a weak overall genetic structure (as indicated by Bayesian cluster analysis) the between-deme FST was significant. Linear discriminant analysis of within-deme allele frequencies grouped the demes according to the age and previous land-use history of their grassland polygons. The convergence of the allele frequency profiles in the younger grasslands towards those of the old grasslands is consistent with convergence of selective regimes as pastures mature towards an increasingly uniform, dense sward and characteristic species assemblage. 6The genetic composition of demes of a grassland species appears to be influenced by the process of plant community convergence during grassland development , complementing the recent finding that convergence of species composition in experimental assemblages of grassland plants is dependent on the genotypic composition of the component species. [source] A comparative study of seed number, seed size, seedling size and recruitment in grassland plantsOIKOS, Issue 3 2000Anna Jakobsson In this study we analyse relationships between seed number, seed size, seedling size and recruitment success in grassland plants. The often hypothesised trade-off between seed size and seed number was supported by a cross-species analysis and by an analysis of 35 phylogenetically independent contrasts, derived from a data-set of 72 species. Apart from among-species relatedness, we also controlled for possible confounding effect of plant size that may influence both seed size and seed number. A sowing experiment with 50 species was performed in the field. The seeds were sown in a grassland and subjected to two treatments, disturbance and undisturbed sward. Evidence for seed-limited recruitment was obtained for 45 of the species. Disturbance had a significant, or nearly significant, positive effect on recruitment for 16 of the 45 species. The relative recruitment in undisturbed sward increased with increased seed size, and both recruitment success and seedling size were positively related to seed size. We suggest that a trade-off between competitive ability and number of recruitment opportunities follows from the trade-off between seed size and seed number, through a causal chain from seed size via seedling size to recruitment success. The relationships between seed size, seed number and recruitment may be an important underlying mechanism for abundance and dynamics of plant species in grassland vegetation. This is an example of a direct link between evolutionary life-history theory, and theory of plant community structure. [source] Grasshopper Herbivory Affects Native Plant Diversity and Abundance in a Grassland Dominated by the Exotic Grass Agropyron cristatumRESTORATION ECOLOGY, Issue 1 2009David H. Branson Abstract The indirect effects of native generalist insect herbivores on interactions between exotic and native grassland plants have received limited attention. Crested wheatgrass (Agropyron cristatum) is the most common exotic rangeland grass in western North America. Crested wheatgrass communities are resistant to colonization by native plant species and have strong competitive effects on native species, imposing problems for the restoration of native grasslands. Grasshoppers are generalist herbivores that are often abundant in Crested wheatgrass,dominated sites in the northern Great Plains. We conducted two experiments in a Crested wheatgrass,dominated grassland in western North Dakota to test the hypothesis that grasshopper herbivory influences local Crested wheatgrass community composition by impeding native seedlings. Grasshopper herbivory negatively affected the species richness, abundance, and Shannon diversity of native plants in 3 of 4 years. Although additional research is needed to determine if grasshoppers actively select native plants, the effects of grasshopper herbivory may be an important consideration in the restoration of Crested wheatgrass areas. Our findings illustrate the importance of understanding the impact of native generalist invertebrate herbivores on the relationships between exotic and native plants. [source] Remnant habitats for grassland species in an abandoned Swedish agricultural landscapeAPPLIED VEGETATION SCIENCE, Issue 3 2010Anna Dahlström Abstract Questions: Which factors influence the persistence of vascular grassland plants in long-abandoned (at least 50 yr) arable fields and meadows? What might be the implications of current levels of species richness on abandoned arable fields and meadows for future restoration? Location: Forested highlands of Kilsbergen, south central Sweden. Methods: The abundance of all vascular plant species was investigated in three habitat types: former arable fields, hay meadows and outlands (pastures) at 27 farms, abandoned for either approximately 50 yr or 90 yr. Time since abandonment, tree cover, soil depth, degree of soil podsol development, size of the infield area and two measures of connectivity were used as predictors for species richness and species composition. Results: Former outland had denser tree cover, fewer species and fewer grassland species than former arable fields and hay meadows, irrespective of time since abandonment. Former hay meadows and arable fields with a longer time since abandonment were less rich in species, more wooded and had greater podsolization than meadows and fields abandoned at a later stage. Species richness was higher in hay meadows and arable fields at farms with larger infield area and deeper soils compared with farms with smaller infield area and shallower soils. The greatest richness of species and most open habitat were former arable fields at larger farms abandoned 50 yr before the study. Former arable fields had the highest number of grassland species. Conclusion: After 50 yr of abandonment, former arable fields were the most important remnant habitats for grassland species and may be a more promising target for restoration than formerly managed grasslands. [source] | ||||||||||