Palmer Drought Severity Index

1
   
Sites of the Historical Structures and Old-Growth
Forests
DEVELOPMENT AND ANALYSIS OF A REGIONAL
DROUGHT-SENSITIVE OAK RING-WIDTH RECORD IN
NORTHEAST OHIO LEHMANN, Sophie B.1, WILES,
Gregory C.1, and COOK, Edward R.2, Nigel Brush.3
Geology, The College of Wooster, 1189 Beall Ave,
Wooster, OH 44691, slehmann08_at_wooster.edu, (2)
Tree-Ring Lab, Lamont-Doherty Earth Observatory,
61 Route 9W, Palisades, NY 10964, (3) Geology,
University of Ashland, Ashland, OH.
Figure 4 Table 4 Table of Northeast Ohio white
oak chronology comprised of living old growth
white oaks and timber from historical structures.
Circles indicate structures and squares, old
growth forests. The location of the OARDC and
the Killbuck Gauging Station are also shown.
Abstract Dating Historical Structures
Tree-ring series developed from old growth oak
forests in Northeast Ohio are sensitive records
of past moisture variability and have been used
in pervious work, together with a larger network
of chronologies, to reconstruct drought histories
on a continental scale. The development and
extension of a network of tree-ring records for
Northeast Ohio use tree-ring width data obtained
from both living white oaks and oak timbers from
historical buildings. Three hundred and four
series from thirteen locations are combined into
a regional ring-width chronology that spans AD
1550- 2005 and is positively correlated with
summer precipitation and streamflow in the
region. The strong correlation with streamflow
and precipitation potentially provide a
reconstruction of past years. The regional
chronology standardized using a negative
exponential shows a downward tread while the
linear regression standardization shows a general
upward trend in the tree growth over the past
hundred years. The three most narrow rings in
the 456 year chronology are AD 1699, 1810, and
1748 and correspond with large-scale volcanic
events suggesting either anomalously cold summers
for the region or Midwest drought associated with
cooling recognized at higher latitudes.
 
   
Climate Significance of NEO The regional NEO
chronology (Figure 4 Table 4) has been extended
and updated from what was initially a chronology
based on two old growth sites. The resulting
record spans 1550-2005 with 304 series and shows
a strong intercorrelation (0.58). The NEO
ring-width series was compared with a long
monthly (1888-2003) precipitation record from the
Agricultural Station in Wooster located centrally
to the study sites. The common period of 112
years was compared for monthly temperature and
precipitation values for the dendroclimatic year
starting March of the previous through October of
the year of growth (Fig. 5). The total
precipitation for June and July of the year of
growth (r 0.48) shows the moisture sensitivity
of the record. A strong negative relationship
with June temperatures is noted and is likely due
to the intercorrelation with precipitation. In
addition to the comparisons with the monthly
Meteorological records we compared the NEO series
with monthly streamflow records for the region at
Killbuck on the Killbuck River. For a common
75-year period August and September streamflow
yielded the strongest correlation at 0.37
potentially a significant level for streamflow
reconstruction. Standardization of the
chronology was done in two ways, by using the
negative exponential and linear regression (Fig.
6a, b.). The two standardizations are similar
until the late 1800s when negative exponential
standardization (Fig. 6a) indicates a downward
trend after the early 1900s. In contrast,
linear regression standardization (Fig. 6b)
produced a general increasing trend in ring-width
in the early 1900s.
Palmer Drought Severity Index
Crossdating allows us to extend tree-ring
chronologies further into the past by matching
ring patterns. (graphic - Anne Krawiec)
Tree-ring based spatial patterns of drought.
(Fig 7 and 8). By transferring tree-ring proxy
record results into Palmer Drought Severity
indices (PDSI), the regional pattern of drought
during a given year or decade can be recognized
(Cook et al., 1999). This information is used for
understanding past drought and conditions
associated with drought as well as for
agricultural planning.
METHODS AND DATA Ohio Ring-Width Chronologies
With assistance from the Fall 2004 class,
Climate Change 210, at the College of Wooster, we
have sampled old growth oak (Quercus) trees at
Browns Lake Bog, Sigrist Woods, and Johnson
Woods. The Johnson Woods chronology now extends
back to the 1559, giving us a continuous,
annually-dated series for the area. From these
sites tree-ring chronologies have been developed
that provide us with a more regional tree-ring
record with which to compare newly sampled cores
and ancient wood. Sampling living trees is
preformed by using an increment coring into the
trunk of the tree. This action produces a thin
core (5 mm) that is taken to the Tree Lab to be
dated. Although the tree is living, the process
of extracting a core from the trunk does not hurt
the tree. Once the core is taken, the tree
quickly fills the hole with sap to protect the
small wound.
Figure 7 Figure 8
Figure 5 Twenty-month dendroclimatic year of
tree-ring growth relating to precipitation and
temperature. Months with a 0.05 confidence level
are indicated.


Figures 7 and 8 are Palmer Drought Severity
Index (PDSI) maps showing summer drought spatial
variability (Cook et al, 1999). These plots are
based on a network of tree-ring records. For the
year 1895, trees in northeastern Ohio added a
narrow tree-ring which correlates with
considerably low precipitation which resulted in
drought. The high peak of 1969 is a wide tree
ring displayed as a high level of moisture for
Northeast Ohio. The tree ring model from
Northeastern Ohio explains 34 of the variation
in June and July precipitation.
Increment borer
Electric Borer used to sample historical
structures
Conclusions

• Using tree-ring crossdating we can assign
  calendar dates to outer rings of historical
  structures, and determine the date of cutting
  where outer rings are preserved. Once the house
  is dated we provide a report to the homeowner or
  organization that owns the structure.
• This continuing work has extended tree-ring
  chronologies from Northeastern Ohio from 1550 to
  2005.
• The Midwestern climate changes, especially
  moisture variability, can be explored using
  tree-ring records.
• We will have a better understanding of how
  climate changes as well as recognize persistent
  climate patterns that will help us better prepare
  for future precipitation variation and drought.
• The regional chronology when compared with
  monthly Meteorological records correlates at
  0.48. The streamflow record correlates most
  strongly with the regional chronology at 0.37.
  Therefore giving a strong potential for
  reconstructing streamflow discharge from the
  Killbuck River.
• Narrow rings in this record (1699, 1810)
  correlate with large-scale volcanic events
  suggesting regional cool summers or Midwest
  drought associated with cooling.
• Standardization through linear regression shows
  an upward trend whereas \negative exponential
  shows a downward trend.

Boring an old growth oak
Shear House at Smithville Community Historical
Society
Dating Ohio Historical Structures
We have been sampling in the Wayne County
Ohio at sites such as the Geiser House in
Orrville, the Beall House of the Wayne County
Historical Society in Wooster, the Morgan House
and Barn in Orrville, and the Pee Wee-Hilton in
Wooster. By coring and sawing beams and joists in
old houses, barns, and other historical
structures, we are extending the Ohio Oak
chronology further back in time as well as
calendar date structures. A sample is
extracted from a structure by drilling a thin
long core from a beam. The process of extracting
a sample does not harm the structure. The
evacuated hole due to the core is plugged by a
peg to cover and protect against infestation by
insects.
 
Pee Wee Hilton was originally from downtown
Wooster, Ohio area and the beams were later moved
to the Boycott camp in Pee Wee Hollow.
Coring on the side of the historical Smithville
Cabin, Smithville, Ohio. Beams are inspected for
the presence of their outer rings (bark year).
The outer rings are marked before drilling to
ensure that the ring remains intact when sampling.
Acknowledgements
A metal guide is nailed into the beam prior to
drilling to prevent travel of the coring device
across the wood.
The Environmental Analysis and Action (EAA)
program was made possible by a grant from the
Luce Foundation. Shawn Godwin, an architect
working on the Beall House in Wooster, allowed us
to sample the beams at the Beall House as well as
at the Geiser House in Orrville. Home and Forest
owners like Dr. David Taggart took us to sample
beams at Pee Wee Hollow.The fall 2004 Climate
Change 210, sampled trees from Browns Lake. Dr.
Ed Cook of Lamont-Doherty Earth Observatory
provided unpublished data and support for dating
historical structures.
References Cook, E.R. and L.A. Kairiukstis. 1990.
Methods of Dendrochronology. Dordrecht Kluwer
Academic Publishers. 394 p. Stokes, M. A. and
Smiley, T. L., 1968, An introduction to tree-ring
dating Tucson University of Arizona
Press. http//www.ncdc.noaa.gov/paleo/pdsi.html