Mapping the Microenvironment for Seed Germination in the Field

Abstract

Gaps in the canopy have a major influence upon the microenvironment for seed germination in natural vegetation. Two methods for measuring gaps in grasslands are described. The first uses a field-portable instrument for mapping R/IR ratios under the canopy, and the second employs infrared photography and image analysis to measure gaps from above. The methods are illustrated with results from an experiment in which grazing sheep are the principle influence upon the structure of the grass canopy. Results of both methods show that the effects of current and past grazing regimes may be detected in the canopy structure of the grassland. Seeds of Geranium dissectum sown into gaps of different sizes showed greater establishment in small gaps (1-2 cm2) than under a closed canopy.