Keeping time in a space-for-time substitution: A chronosequence of forest histories at Jefferson's Monticello plantation

Background/Question/Methods

The piedmont region of southeastern North America experienced intensive land use after colonial settlement in the 1700s.  Thomas Jefferson’s Monticello provides a well-documented opportunity to examine the long-term recovery of forests to past plantation agriculture typical of this region.  Using dendroecology, repeated forest surveys, and historical documents, we reconstruct the ecological history of forest stands at Monticello to discern how forest succession varies through time from colonial settlement to the present.  Tree-ring data, primarily from Pinus and Quercus species, provide estimates of tree establishment beginning in the 1700s forming a chronosequence of reconstructed forest histories with increasing time since past land use.  Subsequent canopy disturbance events within these forests are determined using time series analysis with intervention detection, which identifies release events in the growth rates of these trees over the past two centuries.  Surveys and documents from Jefferson are used to indirectly estimate forest condition during his tenure.  Current species composition and density are also compared with a forest survey collected across Monticello in 1935.

Results/Conclusions

Collectively, the growth, composition, structure, and extent of forests at Monticello reflect interactions of life history attributes, aspect, and past land use that began during the colonial era.  During Jefferson’s time, tree-ring and documentary evidence reveal a partial ring of forests surrounding the slopes of Monticello, leading to a new interpretation of Jefferson’s timber zone.  These oldest forests in the chronosequence, which are largely found on west-facing slopes, show pine recruitment starting in the late 1700s followed by oaks.  Former agricultural fields on southeast-facing slopes record additional successional sequences beginning in the early and mid-1900s with pine recruitment.  In 1850s and 1860s, a period of synchronous oak recruitment is observed across much of the property that is not mentioned in documentary accounts and could reflect decreased land use at that time.  Numerous release events are also observed during the early 1800s, mid 1800s and 1960s, coincident with recruitment pulses.  Thus, the forests at Monticello record how colonial-era land use decisions continue to impact forest growth and composition more than two centuries later.