Modelling the role of stores and reserves in grassland plants

• Collaborators
  • Institute of Low Temperature Science, University of Hokkaido, Japan
• Macaulay Contacts
  • Barry Thornton (Soil Plant Microbial Interactions)

Hokkaido's climate and flora have similarities with those of Scotland, but Hokkaido has a relatively short history of human impact and rich volcanic soil, so that its unenclosed land is predominantly forest. The Japanese flora is very diverse and influenced by habitats and factors unfamiliar in Britain, such as volcanoes and prolonged, deep snow cover. This project provided an exciting opportunity to exchange ideas about grassland ecology, see familiar species from British grasslands in natural habitats (no longer possible in Britain), and study the indigenous grassland vegetation of Japan, which appears to be a neglected resource.

Recent research and modelling at the Institute has emphasized the roles of storage and remobilization of photo-assimilates and nutrients in the recovery of grassland plants from grazing damage. In Japan, Dr Suzuki has been studying the role of storage in perenniality and species coexistence. The Anglo-Japanese collaboration developed ideas about links between allocation, morphology and ecology. Professor Hara and Dr Suzuki are establishing a new molecular biology laboratory to study local and regional genetic variation in plants. Dr Li was conducting experiments using genotypes of Arabidopsis thaliana from an international collection to study the interactions between known genetically determined life-history traits, defoliation and competition. This use of selected genotypes was unusual in a study of life history and fitness. Macaulay staff used a model of grazing impacts to predict the likely results of Dr Li's proposed defoliation treatments.

The complex morphology of grasses makes it difficult to develop and test mathematical or simulation models of grazing impacts on them. Differences between experimental observations and model predictions may result from fundamental flaws in model assumptions, failures of the model to include processes peripheral to the main focus of interest, or merely inaccurate estimation of model parameters.

In contrast to Britain, Japan has a rich flora of spring ephemeral species that are potentially valuable model plants for testing growth models. For example, Erythronium japonicum (the Japanese dog-tooth violet) can consist entirely of a bulb in winter and a bulb, roots and a single leaf in spring. Numerous other species have individuals or units that are almost as simple and determinate. However, leaf expansion and growth in these species would need to be substantially self-supporting for these species to provide useful analogues of grass growth. Repeated measurements on plants of several species in the University of Hokkaido's botanic garden and in a local forest allowed identification of the timing of the end of leaf expansion. A small experimental study was also made on the effect of imposing deep shade on the leaf expansion over 48 hours of a population of E. japonicum in an experimental forest at Moshiri in northern Hokkaido (Figure 1). Shading did not affect increases in leaf area, but reduced leaf mass. These results suggest that these species can be useful for future model development in Britain and Japan.