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Harvard Forest Symposium Abstract 2012
- Title: Woody Species Phenology, Prospect Hill Tract, Harvard Forest - 2011
- Primary Author: John O'Keefe (Harvard Forest)
- Abstract:
Woody Species Phenology, Prospect Hill Tract, Harvard Forest - 2011
J. O'Keefe
2011 was the twenty-second 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) 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. 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 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 2010-11 was cool and very snowy. Spring then turned somewhat warmer and wetter than normal, a pattern that continued into the summer and climaxed with flooding rains at the end of August in association with tropical storm Irene. Fall continued wetter and much warmer than normal. The first frost at Harvard Forest occurred on October 27th, more than three weeks later than the mean first frost date observed from 1990-2009, continuing the pattern of very late first frosts over the past several years.
Probably influenced by the slow melting of the deep winter snow, bud break in 2011 was a few days later than the 20-year mean (Table 1/Figure 1). Leaf development then progressed steadily, with 75% leaf development occurring a few days later than the 20-year mean. The mild fall temperatures and very late first frost led to a 50% leaf fall in 2011 several days later than the long-term mean date. 2011’s slightly later leaf emergence coupled with later 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: Phenology_JOK_Table 1-2012.pdf
Figure 1-4spp 2011.pdf
Figure 2-grow season-2011.pdf
