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Harvard Forest Symposium Abstract 2011
- Title: Woody Species Phenology, Prospect Hill Tract, Harvard Forest - 2010
- Primary Author: John O'Keefe (Harvard Forest)
- Abstract:
Woody Species Phenology, Prospect Hill Tract, Harvard Forest - 2010
J. O'Keefe
2010 was the twenty-first year in our ongoing investigation of the timing of woody vegetation development during the growing season. However in 2002 the scope of the study was changed significantly. For the first twelve years we observed bud break, leaf development, flowering, and fruit development on three or more individuals of 33 woody species at 3-7 day intervals from April through June. These observations documented substantial (up to three weeks difference) interannual variation in the timing of spring development, but good relative consistency among species and among individuals within species during these twelve years.
Therefore, starting in 2002 we maintained the same observation schedule, but reduced the number of species observed to nine, including red maple (Acer rubrum), sugar maple (A. saccharum), striped maple (A. pensylvanicum), yellow birch (Betula alleghaniensis), beech (Fagus grandifolia), white ash (Fraxinus americana), witch hazel (Hamamelis virginiana), red oak (Quercus rubra), and white oak (Q. alba). This subset of important, representative species should allow us to continue to characterize leaf development each spring, and document inter-annual variability while reducing the resources required for the study significantly.
We have also recorded fall phenology since 1991, with the exception of 1992. Weekly observations of leaf coloration and leaf fall begin in September and continue through leaf fall. In 2002 the number of species observed in the fall was reduced to fourteen, including red maple (Acer rubrum), sugar maple (A. saccharum), striped maple (A. pensylvanicum), shadbush (Amelanchier laevis), yellow birch (Betula alleghaniensis), black birch (B. lenta), paper birch (B. papyrifera), beech (Fagus grandifolia), white ash (Fraxinus americana), black gum (Nyssa sylvatica), black cherry (Prunus serotina), white oak (Quercus alba), red oak,(Q. rubra) and black oak (Q. velutina).
All individuals are located within 1.5 km of the Harvard Forest headquarters at elevations between 335 and 365 m, in habitats ranging from closed forest, through forest-swamp margins, to dry, open fields.
The winter of 2009-10 was unusually mild. In fact, from mid-January through early March Boston set a record of 45 consecutive days with average daily temperatures at or above the 100+ year mean. Warmer than normal weather continued through spring and summer, and into the fall. Slightly below normal winter precipitation was followed by a very wet March and a somewhat drier than normal late spring and summer. The first frost at Harvard Forest occurred on October 22nd, about three weeks later than the mean first frost date observed from 1990-2009, continuing the pattern of quite late first frosts over the past several years.
Reflecting the very mild spring, bud break in 2010 was the earliest yet observed (Table 1/Figure 1). For most species bud break occurred from a day to a week earlier than observed in any of the prior twenty years of observation. Leaf development then progressed steadily, with 75% leaf development occurring close to the same date as in the earliest prior years. Despite rather mild fall temperatures and a late first frost, 50% leaf fall in 2010 occurred quite close to the long-term mean date. This year’s extremely early leaf emergence coupled with near normal leaf senescence continues the trend toward a slightly lengthened growing season (Figure 2).
The record earliness of leaf emergence in 2010, along with the extreme lateness of leaf senescence and fall in 2002, continues to point out the extreme variability in the timing of these events and the complexity of the factors controlling them. These observations emphasize the need to continue these long-term studies and data sets.
- Research Category: Forest-Atmosphere Exchange
- Figures: JO'K's Phenology Font 8-2010.pdf
Symp abstract figs 2010.ppt
