Stuart R. Band

Seed size and shape predict persistence in soil.

An understanding of seed persistence in the soil is important to vegetation management and weed control, but experimental collection of seed bank data is tedious and expensive. We report a rapid, simple method for predicting seed persistence in the soil. The method is tested on a range of British, mostly herbaceous, species. Diaspore (seed or fruit) weight is plotted against variance of the three linear dimensions of the diaspore. All diaspores within an area of the graph defined by a maximum weight and variance are persistent in the soil. The critical weight is the same for fruits and seeds, but the critical variance of diaspore dimensions appears slightly higher for fruits. The great majority of diaspores outside this region are short lived, and the relatively few ambiguous cases can be resolved by reference to habitat (...)

Changing leaf nitrogen and canopy height quantify processes leading to plant and butterfly diversity loss in agricultural landscapes

Summary We describe a novel method for quantifying ecosystem drivers that potentially compromise the effectiveness of agri-environment schemes. We use three sources of data that for many countries are already in the public domain: governmental agricultural statistics, which provide a quantitative assessment of farming intensity in the ‘working landscape’, data on threat status and species distribution for plants and butterflies from conservation agencies and similar bodies and functional traits of plant species abstracted from published data bases. Changes in land use alter ecosystem processes which in turn modify both biodiversity and representation of functional types at the landscape scale. We interpret functional shifts to quantify important ecological drivers of floristic and faunal change and their causal land use origins. We illustrate the power of this approach by means of a worked example. We demonstrate that despite conservation policies to counteract them, eutrophication, identified by leaf nitrogen content, and abandonment, correlated with plant canopy height, are still causing biodiversity loss to native higher plants and butterflies in the English countryside. We use our analyses to suggest how conservation policies can be made more effective and discuss how similar approaches could be applied elsewhere.

An index of weed size for assessing the soil productivity of ancient crop fields

A method is presented for generating data on archaeological weed species relevant to soil productivity and consequently crop husbandry. Three plant attributes (maximum canopy height, maximum canopy spread and maximum dry leaf weight per node) which are functionally related to habitat productivity were measured for 161 British annual species. These three attributes were combined to produce an index of weed size. Index values were found to differ significantly between character species of phytosociological classes from fertile and infertile habitats and to provide an objective assessment of CSR (Competitor/Stress-tolerator/Ruderal) strategysensu Grime (1974, 1979). Further work is required, however, to distinguish ‘medium-sized’ species that exploit highly disturbed and productive habitats from those of less disturbed and less productive situations.

The triangular seed mass-leaf area relationship holds for annual plants and is determined by habitat productivity

Summary Plant allometries help us to understand resource allocation in plants and provide insight into how communities are structured. For woody species, a triangular allometric relationship between seed size and leaf size occurs in which all combinations are all possible, except for species with big seeds and small leaves (Cornelissen 1999). This relationship is thought to be a consequence of between habitat variation in abiotic conditions. In this study, we tested if the triangular relationship between seed mass and leaf area holds for annual species, and if variation in soil productivity and light (measured as Ellenberg indicator values: EIVs) are driving this relationship. We show that the triangular relationship also holds for annuals, which suggests that the allometric combinations between leaf area and seed mass are conserved across life-forms. The triangular relationship was driven by between-habitat variation in soil productivity. This means that as soil productivity increases, plants with bigger leaves could have either big or small seeds. However, in low soil productivity habitats, plants are constrained in their options, and plants with small leaves can only have small seeds. This article is protected by copyright. All rights reserved.