Preston R. Aldrich
- Evolutionary ecology
- Invasive plants
- Old-growth
- Forest disturbance
- Laboratory
- Microsatellites
- Functional genomics
Old-growth forests
Often it is assumed that the terms old-growth, ancient, virgin, uncut, remnant, and undisturbed forest all refer to the same kind of forest, however this is not necessarily the case. It is true that old-growth stands represent a unique resource that deserve special consideration when it comes to management, and many old-growth forests have developed under a rather minimal disturbance regime. However, other old-growth stands have developed on sites amidst repeated disturbances spread over long periods. In the Midwestern U.S., repeated disturbance of lowland mesic sites can lead to the formation of open-canopy oak forests. Oaks (Quercus) are less tolerant of shade than many other temperate tree species such as maple, and the occasional occurrence of canopy openings allows for regeneration.
Oak regeneration
is faltering in many Midwestern and eastern U.S. forests. Stands comprised
of large oaks often contain few oak seedlings or saplings in their understory
where shade-tolerants such as maple now predominate, foreshadowing possible
problems for timber and gene pool resources. Several factors have convened
to produce the oak failure. Many eastern U.S. forests developed under
a regime of disturbances from fire, timber harvest, and livestock grazing
mediated by European settlers (1800-1900s) and Native Americans before
them. Over the past century, disturbances have been suppressed in forest
remnants, promoting the regeneration of shade-tolerant species over those
adapted to disturbance and fire.
Compounding these effects are seed and seedling predation by deer and
rodents, exotic pests and pathogens, and invasive plants that may interfere
with oak forest regeneration.
Much of my research on temperate old-growth forests has focused on the oak-hickory stands at the Davis-Purdue Research Forest in east-central Indiana. The stand was disturbed during settlement of the area in the mid-1800s likely by timber removal, fires, and livestock grazing. All exogenous disturbances were later suppressed following purchase of the property in 1926 by Purdue University. There have been several full censuses of trees > 10 cm dbh in the largest (20-ha) and smallest (4-ha) stands since 1926, initiated by Dr. Burr Prentice and continued by Dr. George Parker. The site is one of the longest-running studies of forest composition and dynamics, and has made numerous important contributions to our understanding of temperate forest ecology.
Links of interest
Hardwood Tree Improvement and Regeneration Center
North Central Research Station, USDA-Forest Service
