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Comparison of Visual Assessment and Digital Image Analysis for Canopy Cover Estimation
Author(s) -
Büchi Lucie,
Wendling Marina,
Mouly Pauline,
Charles Raphaël
Publication year - 2018
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2017.11.0679
Subject(s) - canopy , cover (algebra) , plant cover , vegetation (pathology) , cover crop , remote sensing , environmental science , context (archaeology) , estimation , agroforestry , geography , ecology , biology , mechanical engineering , engineering , medicine , management , archaeology , pathology , economics
Core Ideas Cover crops provide ecosystem services linked to canopy cover development. Visual assessment of canopy cover is compared with two digital image analysis methods. Visual estimation is well correlated with image estimation but showed lower values. The choice of the canopy cover estimation method depends on the objective.Currently, in the context of agriculture, cover crops are crops cultivated with the sole aim of providing important ecosystem services such as erosion prevention. Many services offered by these crops are directly linked to the development of their vegetation, and especially of canopy cover. A proper estimation of this cover is thus necessary to evaluate cover crop performance. Many methods to estimate canopy cover exist, but differ in terms of effort and time needed to implement them. In this study, we compared visual assessment of canopy cover in the field with two methods of digital image analysis (Assess and Canopeo), for different cover crop species and vegetation types. Visual estimation was positively correlated with both type of image analysis estimations. However, it showed systematically lower values of canopy cover, especially at intermediate canopy cover values. The type of vegetation influenced the visual and digital image estimations, narrow leaf species being the most difficult to evaluate visually. This study showed that depending on its utilization, visual canopy cover assessment could be useful, especially when only relative estimation of canopy cover is needed. When absolute canopy cover estimation is needed, the use of digital image analysis should be preferred.