Open AccessTesting Hopkins’ Bioclimatic Law with PhenoCam data
Author(s) -
Richardson Andrew D.,
Hufkens Koen,
Li Xiaolu,
Ault Toby R.
Publication year - 2019
Publication title -
applications in plant sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 23
ISSN - 2168-0450
DOI - 10.1002/aps3.1228
Subject(s) - phenology , evergreen , spatial variability , deciduous , precipitation , vegetation (pathology) , grassland , latitude , atmospheric sciences , physical geography , environmental science , climatology , longitude , ecology , geography , biology , geology , meteorology , medicine , statistics , mathematics , geodesy , pathology
Premise of the Study We investigated the spatial and temporal patterns of vegetation phenology with phenometrics derived from PhenoCam imagery. Specifically, we evaluated the Bioclimatic Law proposed by Hopkins, which relates phenological transitions to latitude, longitude, and elevation. Methods “Green‐up” and “green‐down” dates—representing the start and end of the annual cycles of vegetation activity—were estimated from measures of canopy greenness calculated from digital repeat photography. We used data from 65 deciduous broadleaf ( DB ) forest sites, 18 evergreen needleleaf ( EN ) forest sites, and 21 grassland ( GR ) sites. Results DB green‐up dates were well correlated with mean annual temperature and varied along spatial gradients consistent with the Bioclimatic Law. Interannual variation in DB phenology was most strongly associated with temperature anomalies during a relatively narrow window of time. EN phenology was not well correlated with either climatic factors or spatial gradients, but similar to DB phenology, interannual variation was most closely associated with temperature anomalies. For GR sites, mean annual precipitation explained most of the spatial variation in the duration of vegetation activity, whereas both temperature and precipitation anomalies explained interannual variation in phenology. Discussion PhenoCam data provide an objective and consistent means by which spatial and temporal patterns in vegetation phenology can be investigated.