Browsing by Subject "valokuvaus"

Loss of biodiversity in the Finnish agricultural environment has increased during the last decades due to the agricultural intensification. Accurate, efficient and repeatable sampling methods are important to follow the impacts of the measures to enhance biodiversity. This study focuses on the assessment of vegetation structure and species diversity. Vegetation cover is one of the most common measures to assess vegetation biodiversity. Cover data is usually collected by a point intercept method, a line intercept method or by visual estimation in quadrats. Traditional methods have been found to be laborious, time-consuming and subjective, and having poor repeatability. The main objective of this study was to find out if it is possible to improve vegetation surveys with digital photographs and an object-based image analysis. To answer this question, a visual method (VM) was compared with a photographic method (PM). The VM was based on ocular estimation of the total vegetation cover. In the PM, pictures of the top cover were taken vertically downward from 1.5 meters above the ground. Using a software program called Definiens, the photographs were divided into segments, which were then classified into bare ground, litter, monocots and dicots to estimate the covers for each category. The data was collected during the summer 2010 from environmental fallows and set-asides. There was a clear correlation between the cover measures in the VM and the PM, so it can be assumed that the PM is suitable for the assessment of the vegetation cover. However, using only the PM, it is not possible to get a reliable estimate of the vegetation structure or species diversity. It was faster to collect the data in the field with the PM than with the VM. The computer used in this survey was inefficient, thus the image analysis took more time than expected and as a result the PM was in its entirety slower than the VM. The study gave important theoretical and practical information about the photographic method, its strengths and weaknesses. Photographic methods are still under development and further research is needed but they hold promise for the future.