TY - JOUR
T1 - Detecting differences in crown transparency assessments between countries using the image analysis system croco
AU - Mizoue, Nobuya
AU - Dobbertin, Matthias
N1 - Funding Information:
We are grateful to T. Bucha of Forest Research Institute, Slovak Republic for his assistance in the field survey. Financial support for this study was partially provided by the European Commission and by a Grant-in-Aid for Scientific Research (B) (No. 13556021) from the Japan Society for the Promotion of Science (JSPS). The data used in this study were obtained when the corresponding author was a visiting researcher at the Swiss Federal Institute for Forest, Snow and Landscape Research, and was jointly funded by the Swiss National Science Foundation and JSPS.
PY - 2003/12
Y1 - 2003/12
N2 - Estimates of crown transparency calculated using the semi-automatic image analysis system CROCO were compared with the visual estimates of survey teams from 12 European countries. For each of five European species (Norway spruce (Picea abies (L.) Karst.), silver fir (Abies alba Mill.), Scots pine (Pinus sylvestris L.), beech (Fagus sylvatica L.), oak (Quercus robur L.)) 15 trees were assessed. In 64% of the comparisons, CROCO estimates and the survey teams' scores differed significantly, while differences between countries were significant in 58% of all comparisons. We calculated Spearman's rank correlation and the standard deviation of the differences between CROCO and each country and between pairs of countries. We then computed the medians for CROCO and each country. CROCO and only a few countries had for all species a higher median correlation and lower median standard deviation than the median for the comparison between countries. In addition no country had a consistently higher correlation or lower standard deviation than CROCO. We conclude that CROCO can provide more consistent and less variable estimates of crown transparency than visual assessments and that it can serve as a reference to detect differences in visual transparency assessments between countries over time.
AB - Estimates of crown transparency calculated using the semi-automatic image analysis system CROCO were compared with the visual estimates of survey teams from 12 European countries. For each of five European species (Norway spruce (Picea abies (L.) Karst.), silver fir (Abies alba Mill.), Scots pine (Pinus sylvestris L.), beech (Fagus sylvatica L.), oak (Quercus robur L.)) 15 trees were assessed. In 64% of the comparisons, CROCO estimates and the survey teams' scores differed significantly, while differences between countries were significant in 58% of all comparisons. We calculated Spearman's rank correlation and the standard deviation of the differences between CROCO and each country and between pairs of countries. We then computed the medians for CROCO and each country. CROCO and only a few countries had for all species a higher median correlation and lower median standard deviation than the median for the comparison between countries. In addition no country had a consistently higher correlation or lower standard deviation than CROCO. We conclude that CROCO can provide more consistent and less variable estimates of crown transparency than visual assessments and that it can serve as a reference to detect differences in visual transparency assessments between countries over time.
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U2 - 10.1023/A:1026044701939
DO - 10.1023/A:1026044701939
M3 - Article
C2 - 14632089
AN - SCOPUS:0242364117
VL - 89
SP - 179
EP - 195
JO - Environmental Monitoring and Assessment
JF - Environmental Monitoring and Assessment
SN - 0167-6369
IS - 2
ER -