Mapping the Microenvironment for Seed Germination in the Field

Silvertown, Jonathan; Smith, Ben

doi:10.1093/oxfordjournals.aob.a087719

Cited by 35 publications

(31 citation statements)

References 9 publications

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“…The summer grazing mechanism was clearly through the opening of vegetation gaps, and superior gap colonizers plant species showed a more positive response to higher stocking rate (Bullock et al 2001). For example, Silvertown and Smith (1989) observed that heavy grazing by sheep in Akinola et al 1998;Dutoit et al 2003;Zimmergren 1980 Low similarity in species composition between soil seed bank and established vegetation Amiaud and Touzard 2004;Edwards and Crawley 1999;Martinkova et al 2009a;Smith et al 2002 Seed predation…”

Section: Seed Bank Expressionmentioning

confidence: 99%

Factors and processes affecting plant biodiversity in permanent grasslands. A review

Gaujour¹,

Amiaud²,

Mignolet³

et al. 2011

Agron. Sustain. Dev.

143

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Research has delivered convincing findings on the effect of biodiversity on ecosystem functioning and humankind. Indeed, ecosystems provide provisioning, regulating, supporting, and cultural services. The global value of annual ecosystem services of grasslands and rangelands is about US$ 232 ha −1 year −1 . Nevertheless, the precise evaluation of biodiversity benefits remains challenging. This issue is due to valuation methods, subjective assumptions, and complexity of drivers of plant community dynamics. Here, we review the primary factors that influence plant diversity of permanent grasslands, and we describe underlying processes. These factors must indeed be identified to focus policies meant to preserve and restore plant diversity and to advise farmers about efficient decision rules. We show that plant dynamics of permanent grasslands cannot be explained simply by agricultural management rules, e.g., grazing, fertilization, and mowing, implemented at the field scale. The configuration of the surrounding landscape, e.g., landscape heterogeneity, habitat fragmentation, and connectivity, acts as a species filter that defines the regional species pool and controls seed flow. The regional species pool often contains higher species richness in a heterogeneous landscape, because of a higher diversity of suitable habitats. This regional pool could be a major species sources for permanent grasslands according to the seed flow. We discuss the need to consider all of these factors to understand plant species composition of permanent grasslands and the necessity to study plant communities using both taxonomic and functional approaches. In order to report this integrative approach, we propose a conceptual model based on three ecological challengesdispersal, establishment, and persistence-that are considered to act as filters on plant diversity, and a graphical representation of the complexity of such studies due to the interaction effects between plant dispersal abilities, forage productivity, disturbances induced by farming practices, and landscape heterogeneity on plant diversity. Last, we discuss the ability of farmers to manage each factor and the necessity of such study in the improvement of the current agro-environment schemes efficiency for farmland biodiversity restoration or preservation.

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Section: Seed Bank Expressionmentioning

confidence: 99%

Factors and processes affecting plant biodiversity in permanent grasslands. A review

Gaujour¹,

Amiaud²,

Mignolet³

et al. 2011

Agron. Sustain. Dev.

143

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“…These gap sizes were chosen to span the range of gap sizes observed in natural grasslands (Gross 1980, Watt and Gibson 1988, Silvertown and Smith 1989. Our rationale was to choose two intergap distributions with a common mean but different variances (underdispersed vs. overdispersed).…”

Section: Field Invasion Studymentioning

confidence: 99%

Rates of Weed Spread in Spatially Heterogeneous Environments

Bergelson¹,

Newman²,

Floresroux³

1993

Ecology

140

136

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Communities subject to disturbance are apparently vulnerable to invasion in that they contain a large fraction of the introduced plant species persisting in any given area. Still, ecologists have a poor understanding of how details of the disturbance regime influence the success with which invaders spread through a community. In this paper, we report results from an experiment that investigates how the spatial distribution of bare ground influences the rate at which offspring of an introduced invader spread through a perennial ryegrass community. Artificially created gaps of three sizes were positioned along linear transects according to one of two spatial distributions. These six transects (one for each treatment combination) were positioned as spokes on a wheel and Senecio vulgaris was introduced into the center. After controlling for the total amount of gap area, we monitored the number and position of Senecio vulgaris establishing for two subsequent generations. Our results showed that the rate of spread of Senecio vulgaris was sensitive to both the gap size and the gap distribution; plants moved a greater distance when the gaps were large and underdispersed. Simulation models confirm that this pattern follows from the way in which gaps sample from seed shadows. We derive an analytical expression to explain why the mean seed dispersal distance does not predict the spread of Senecio vulgaris adults, and show how rates of spatial spread will change under different spatial patterns of disturbance. Finally, a model of spatial point processes confirms that the distribution of gaps mediates the rate of weed spread in two dimensions as well.

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“…Canopy gaps in grasslands can be important for the germination and survival of forbs (Morgan 1998), with both the size of gaps (Silvertown and Smith 1989) and the arrangement of gaps (Platt and Weis 1977) influencing plant recruitment. Small scale variation in plant cover may also allow more plant species to coexist (Silvertown 1981).…”

Section: Introductionmentioning

confidence: 99%

Effects of exotic grass invasion on spatial heterogeneity in the ground-layer of grassy woodlands

Lindsay

Cunningham

2011

Biol Invasions

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We quantified the effects of exotic annual grass invasion on the ground-layer structure of grassy eucalypt woodlands, with the aim of determining if weed invasion decreased gap size and plant basal area leading to reduced spatial heterogeneity. We measured plant density, distance between plants and basal plant area in woodland sites which ranged from zero to 100% exotic plant cover in the ground-layer. The ground-layer in uninvaded woodlands was heterogeneous, with a large variation in basal plant area and distance between plants. Exotic annual grass density was positively correlated with total plant density, whereas native plant density was negatively correlated. Total plant basal area decreased as total plant density increased, with a lower total plant area in exotic dominated transects compared to native dominated. Variation in basal plant area decreased with increasing plant density. Exotic annual grasses were more closely spaced together (smaller gap size) and had a smaller basal area than the native grasses and rushes. There was also less variation in basal area and gap size with individual exotic annual grasses compared to the native grasses. Inter-plant distance was greater for both the native and exotic grasses when they had native grasses neighbouring them instead of exotic grasses. These findings show that woodlands invaded by exotic annual grasses have relatively less spatial heterogeneity in the groundlayer. These results have implications for other aspects of perennial grassy ecosystems invaded by annual grasses, including plant recruitment and restoration strategies.

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Mapping the Microenvironment for Seed Germination in the Field

Cited by 35 publications

References 9 publications

Factors and processes affecting plant biodiversity in permanent grasslands. A review

Factors and processes affecting plant biodiversity in permanent grasslands. A review

Rates of Weed Spread in Spatially Heterogeneous Environments

Effects of exotic grass invasion on spatial heterogeneity in the ground-layer of grassy woodlands

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