Purpose of the Tree Project Study

In central Texas, periods of intermittent and unpredictable drought strain water resources necessary for human use and ecosystem health. Serious drought has been present at least once every decade of the 20th century (Riggio et al, 1987). The instrumental record indicates that the most severe deficit in precipitation occurred during the drought of record in the 1950s (1947-1957). Towards the end of this drought in 1956, 96% of the counties (244 out of 254) in Texas were considered disaster areas by the federal government (Hatfield, 1964). This was also a time where temperatures increased thus increasing PET and magnifying the effect of decreased precipitation. It is important for water planners as well as citizens to understand that the drought of the 1950s is most likely not an aberration and can return. This was brought into the forefront of many individual’s minds as the region has experienced moderate to extreme drought conditions from May 2008 through the fall of 2009.  However, this is easily forgotten as the region also experiences abnormally wet periods that ease the ill effects of drought.  At best the instrumental record extends to the late 19th century and does not allow for determination of trends or long term cycles in precipitation. To determine drought frequency it is important to find adequate paleoclimate proxies that extend the record of precipitation for the region.

Determining the frequency of past drought can assist water planners in future resource management. Drought has recently occurred in central Texas and is predicted to occur with increased intensity and frequency as current climate models indicate Texas as a “hot spot” for adverse effects of climate change (IPCC, 2007). Therefore, a longer record of the drought history of the region is needed to: (1) gain insight into the future of water resources; (2) understand past climate conditions; and (3) help verify the validity of climate models.

bald cypressCurrently water managers (Texas Water Development Board, River Authorities, Texas Commission on Environmental Quality), use the drought of the 1950s as the drought of record when planning for future water resources. What is unknown is the extent to which the drought of the 1950s characterizes the historical record of drought for the region. However, there is evidence to suggest that droughts as prolonged and severe as the drought of the 1950s have occurred in the region (Stahle and Cleaveland, 1988). If you couple this knowledge with a growing population and increased water usage it is foreseeable that future droughts can have substantial, negative impacts. A longer record of drought for the region will assist in determining the past frequency of drought and the frequency and intensity in which it may return. This study aims to determine the extent to which bald cypress (Taxodium distichum) trees can lengthen the drought record for central Texas.