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Harvard Forest Symposium Abstract 2013
- Title: Woody Species Phenology, Prospect Hill Tract, Harvard Forest - 2012
- Primary Author: John O'Keefe (Harvard Forest)
- Abstract:
2012 was the twenty-third year in our ongoing investigation of the timing of woody vegetation development (phenology) during the growing season (Data are available at - http://harvardforest.fas.harvard.edu:8080/exist/xquery/data.xq?id=hf003). 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) inter-annual 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 through full development 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). An additional seven species, including shadbush (Amelanchier sp.), black birch (B. lenta), paper birch (B. papyrifera), alternate-leaved dogwood (Cornus alternifolia), hawthorn (Crataegus sp.), black cherry (Prunus serotina), and black oak (Q. velutina), continue to be observed through bud break. This subset of important, representative species has allowed 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. Approximately 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 sp.), 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 2011-12 was very mild (the warmest on record for Boston and Worcester) and, with the exception of a late October snowstorm, largely snow free. Spring continued very warm and drier than normal. Summer stayed warmer than normal, but with slightly above average precipitation. Fall turned drier again with near normal temperatures. The first frost at Harvard Forest occurred on October 12th, more than a week later than the mean first frost date observed from 1990-2011, continuing the pattern of later first frost dates over the past several years.
Despite the very warm winter and spring, bud break in 2012 was only the second earliest we have observed, clustered in a group of several other early years but nearly a week later than the earliest year, 2010 (Figure (Table) 1/Figure 2). Leaf development then progressed steadily, with 75% leaf development occurring nearly a week earlier than the 22-year mean. Despite the mild fall temperatures and rather late first frost date, 50% leaf fall in 2012 occurred slightly ahead of the 22-year mean date. 2012’s quite early leaf emergence coupled with slightly early leaf senescence continues the trend toward a slightly lengthened growing season over the period of our observations (Figures 3, 4 & 5).
The record earliness of leaf emergence in 2010, along with the extreme lateness of leaf senescence and fall in 2002, continue 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.
study significantly.
We have also recorded fall phenology since 1991, with the exception of 1992. Approximately 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 sp.), 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 2011-12 was very mild (the warmest on record for Boston and Worcester) and, with the exception of a late October snowstorm, largely snow free. Spring continued very warm and drier than normal. Summer stayed warmer than normal, but with slightly above average precipitation. Fall turned drier again with near normal temperatures. The first frost at Harvard Forest occurred on October 12th, more than a week later than the mean first frost date observed from 1990-2011, continuing the pattern of later first frost dates over the past several years.
Despite the very warm winter and spring, bud break in 2012 was only the second earliest we have observed, clustered in a group of several other early years but nearly a week later than the earliest year, 2010 (Table 1/Figure 1). Leaf development then progressed steadily, with 75% leaf development occurring nearly a week earlier than the 22-year mean. Despite the mild fall temperatures and rather late first frost date, 50% leaf fall in 2012 occurred slightly ahead of the 22-year mean date. 2012’s quite early leaf emergence coupled with slightly early leaf senescence continues the trend toward a slightly lengthened growing season over the period of our observations (Figure 2).
The record earliness of leaf emergence in 2010, along with the extreme lateness of leaf senescence and fall in 2002, continue 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: Phenology_JOK_Table 1-2013.pdf
Phenology_JOK_Figure 2-2013.pdf
Phenology_JOK_Figure 3-2013.pdf
Phenology_JOK_Figure 4-2013.pdf
Phenology_JOK_Figure 5-2013.pdf
