Effects of riparian buffers on hydrology of northern seasonal ponds

Although seasonal ponds are common in northern, glaciated, forested landscapes, forest management guidelines are generally lacking for these systems. The objective of this study was to determine the effect of riparian buffer type on seasonal pond hydrology following harvest of the adjacent upland forest. A replicated block design consisting of four buffer treatments was established in north central Minnesota in 2000. Treatments included an uncut control (i.e., the upland and buffer were uncut) and three treatments in which the upland was clearcut but the buffer was either uncut, partially harvested, or clearcut. Hydrologic characteristics were examined for differences among buffer treatments. One year of pre-harvest data was collected followed by five years of post-harvest data. Regression analysis of water levels indicated that all buffer treatments had significantly higher pond water depth than the uncut control for four years following harvests. The fifth year following harvests showed no difference in water depth between buffer treatments and the uncut control. In the first post-treatment year, the clearcut buffer treatment had the highest mean annual water depth of the three buffer treatments. Changes in evapotranspiration and runoff due to altering upland and riparian vegetation are considered key factors in explaining these hydrological responses. The results of this study indicate that upland harvesting increases water tables in seasonal ponds, and it takes about five years before water tables are similar to predisturbance levels. Our results also suggest that the amount of vegetation harvested within a riparian buffer affects the hydrologic response, especially in the first year following harvest.