Spatial-functional pattern of ecotonal riparian landscapes on Meridional Plateau, Southern Brazil

Abstract

This study analyzes the Pitangui and Jotuba riparian zonesinthe Meridional Plateau, to create a landscape model of forest/field riparian ecotones. The areas were delineated from 2001 orthophotos (1:10,000), including all native vegetation in flooding limits of the lotic channels. The landscape units (UP) were represented by the Alluvial Ombrophilous Mixed Forest metacommunity (FOMA) including as phytocoenosis both the riparian woody forest (FR) and hydrophilous vegetation (VH). Landscape metrics and statistical treatment were used to characterize landscapes and patches. To evaluate the FR patches we presumed a 30 m edge. The Pitangui River (1,072 ha) has double the riparian area of Jotuba River (539 ha), although proportionally both were UPs equivalent (40 % of FR and 60 % of VH). Both rivers have a large number of small rounded patches and relatively few large areas that trend to more complex and irregular shapes as the area increases. Also smaller patches are more spatially heterogeneous than the larger ones, and more aggregated along the river channel. 60 % of FR area on both rivers is under an edge effect: Pitangui has 91 core areas linked by 69 corridors and the Jotuba River has 53 core areas with 47 corridors. In the riparian zones, VH areas occupy the flood plains showing higher variability in size and spatial distribution. This summarizes the natural fragmentation of the riparian vegetation of regional rivers in Southern Brazil.