Biodiversity is often ill-defined and subjectively surveyed, resulting in inefficient and ambiguous estimates. Strengths and deficiencies of prevailing survey techniques are appraised through a review of selected literature. Analogies with forest inventory are used to suggest options for more efficient and rigorous biodiversity assessment. Techniques such as variable-probability and model-based sampling, especially when used in conjunction with generalized linear modelling, offer efficient alternatives to more traditional assessments based on quadrats and nested plots. Bayesian methods offer scope to combine expert and local knowledge with formal samples, and warrant further investigation. Suggestions for further research are given. 1.

This paper uses a spatial model of the dispersal of annual plants in hierarchical ran- dom maps to extend the investigation of the inter- action between landscape pattern and dispersal characteristics. We examine the following ques- tions: (1) What is the role of species dispersal char- acteristics in their ability to colonize patchy land- scapes? (2) How will the patterns of species spread be affected by landscape scale-dependent patterns of site suitability? 2. Methods The model is a discrete-cell population model (Skellam 1951) simulating the population dynamics of annual plants in landscapes with a hierarchical structure. Each landscape map consists in a grid of individual sites, over which plants of a cific annualpopulation spread through seed disper- sal. The probability of population extinction and the fraction habitat utilization once the population reaches a stable size are examined. 2.1 The landscapes Randomly generated hierarchically structuredmaps were used to simulate nested scale-dependent changes in habitat heterogeneity. Suitability for plant establishment is assumed to be a discrete fea- ture, with sites on the map labelled as 1 (a suitable or `safe'site, Harper 1977)or 0, an unsuitable site. Suitability doesn't reflect site productivity, but describes whether plant establishment is possible. For example, locations covered by a rock would be labelled 0, while open soil would be labelled 1. Site 279 suitability is assumed to be a time-independent fea- ture, so that the habitat map were fixed for the course of a simulation. Recursive algorithms de- rived from fractal geometry (Mandelbrot 1983, Chayes et al. 1988, see also et 1992, Lavorel et 1993)were used togenerate three level hierarchical maps by specifying: (1) the number of units, = w...

doi:10.1111/j.1365-2427.2009.02206.x Theory, methods and tools for determining environmental flows for riparian vegetation: riparian vegetation-flow response guilds

Soil-related performance variation and distributions of tree

The aim of this thesis was to investigate the role of resources in driving ecosystem processes and in influencing soil- and plant communities in boreal and temperate forests, through four complementary experimental studies. In the first study, plant and soil microbial responses to the quality and diversity of added organic substrates from boreal forests were investigated. The substrate-diversity effects were greatest for plants and depended on the presence of high-quality substrates. In the second study, the impact of fire disturbance in boreal forests on litterfall composition and decomposition rates was assessed along a fire chronosequence, by collecting litterfall data and performing a litterbag experiment. Time since last fire reduced tree litterfall quality by increasing the proportion of twigs (lowquality litter) in the litterfall and this resulted in a decline in overall litter decomposition rates. In the third study, effects of resource availability on the performance of coexisting boreal tree seedlings were examined by growing seedlings in pots with low- and high fertility soil under different light filters. The