Document: JUL-3-88-12

Hydrologic regimes, disturbance history, and environmental gradients at four forested long-term ecological research sites : Andrews, Coweeta, Hubbard Brook, and Luquillo.

JONES, J.A.* ¹ and D.A.POST ²

Oregon State University, Corvallis, OR 97331 USA ¹
CSIRO Land and Water, Aitkenvale, Qld 4814, Australia ²

Abstract:
Hydrologic regimes reflect the operation of key moisture storage reservoirs in the vegetation canopy, snow, and soils; hence they influence key ecosystem properties. These moisture storage reservoirs can be defined by lagged cross-correlations between precipitation and streamflow. They have been determined for four forested sites: Cascade Mountains, Oregon (HJ Andrews LTER); White Mountains, New Hampshire (Hubbard Brook LTER); Smoky Mountains, North Carolina (Coweeta LTER); and Luquillo Mountains, Puerto Rico (Luquillo LTER). Precipitation and streamflow are coherent at multiple time scales, ranging from daily to annual, and the periodicity and strength of these lagged cross-correlations varies among sites according to their forest canopy type, soils, snow and climate. At Hubbard Brook, which has a seasonal snowpack, but small soil moisture storage, and deciduous forest canopy, streamflow is highly correlated with precipitation 4-6 months earlier, reflecting a snowmelt influence. At Coweeta, which also has a deciduous forest canopy, but no seasonal snow, and pronounced spatial heterogeneity of soils, streamflow is highly correlated with precipitation a few days earlier where soils are shallow, but this correlation is much smaller and lasts much longer where soils are deep, indicating a long-term soil moisture reservoir. At Luquillo, which has an evergreen forest canopy, no snow, and a small soil moisture storage, precipitation and streamflow are most strongly correlated at scales of days or even shorter time intervals. At Andrews, which has seasonally varying precipitation, some snow, large soil storages, and an evergreen forest canopy, streamflow is significantly correlated with precipitation over multiple time lags ranging from one day to half a year. These storage reservoirs influence stream ecologic processes and may be diagnostic of ecosystem responses to disturbance.

Keywords: Hydro-ecology, LTER sites

This abstract is being presented at: 8:45 AM in session:
Oral Session #22: Multiple Disturbance Effects, Including Fire.