SAMPLING DESIGN
Routine observations of phenology at HBEF began in the spring of 1989 at all watershed sites; observations at HQ began in 1993. The objective of the observations is to provide repeatable, quantified phenology data in a way that takes little time. Each location as described above (1B, 6T, etc) is a specific point along the weekly watershed rounds route which is permanently marked. Visible from each location are three dominant or codominant trees of each of the three species: sugar maple, yellow birch, and beech. These individual trees are permanently marked on the side toward the "location" mark. When possible, their crowns are visible from the location itself to minimize the amount of moving around that is necessary.
DATA DESCRIPTION
For each tree at each location, one index value is recorded weekly during the seasonal transition periods in spring and autumn. The index value reflects the stage of leaf-out or scenescense as described in the data table below. The index is averaged for the three trees of one species at a location and this averaged value is recorded as the phenology index for a given date in the phenology database. Observations are not needed in winter or in summer unless insect attack causes premature senescence or leaffall.
Phenology Codes:
SPRING:
[0] No change from winter conditions, unexpanded buds only
[1] Bud swelling noticeable
[2] Small leaves or flowers visible, initial stages of leaf expansion, leaves about 1 cm long
[3] Leaves 1/2 of final length, leaves obscure half of sky as seen through crowns
[3.5] Leaves 3/4 expanded, sky mostly obscured through crown, crowns not yet in summer condition
[4] Canopy appears in summer condition leaves fully expanded little sky visible through crowns
FALL:
[0] All leaves have fallen except remnants on beech, winter condition
[0.5] Most leaves fallen
[1] No more green in canopy, half of leaves have fallen, leaves still obscure half of sky as seen through crown
[2] Most leaves yellow, red or colored, few leaves have fallen, leaves still obscure most of the sky as seen through crown
[3] Many leaves have noticeable reddening or yellowing, much green still present
[4] Canopy appears in summer condition only scattered leaves or branches have any color change