Patterns of forest cover, hydrological regime, and aquatic biota in Alabama

Background/Question/Methods

The changes in natural forest landscape and aquatic systems are a major consequence of increasing population and urbanization. The processes of converting, harvesting, and fracturing forest landscapes can result in profound changes in aquatic flow regime. We hypothesize that (i) loss of forest cover or increased frequency of disturbances may increase stream peak flow, and reduced low flow; (ii) stream flow regime shapes the dimensions of a channel, including depth and speed; and (iii) changes to the natural flow regime may impact aquatic biological processes and result in novel selective pressures to biota. In the state of Alabama, timber industry is the second largest business. Forest cover loss has potentially profound effects on the flow regimes of stream networks and biota in the state. Through literature and historic data, patterns of forestation, hydrologic flow regime, and aquatic biological distribution are quantified and their co-relationships are estimated.

Results/Conclusions

The spatial relationships are identified and the above hypotheses are tested. It has been found that within the period from 1992-2006, an average forest cover loss in the surrounding 675 km2 around 2nd and 3rd order stream systems has been between 2 and 12%. On these undammed streams, an increase in peak flow discharge and decrease in low flow discharge has been observed during the period of 1993-2006. During this period, local extirpations and invasion of non-native species of freshwater fish increased in these streams. There is positive correlation  between forest cover loss at the100km2 to 1000km2 scale, flow regime, and aquatic selective pressure.