Comparison of vegetation composition in an ephemeral stream channel and the perimeter of pools in subtropical subhumid Central Texas

Ephemeral streams are common in sub-humid central Texas, but have received little attention. Within ephemeral streams are isolated pools that contain water for longer periods than the channel. This study examined the vegetation composition in an ephemeral dry stream channel and pools in Leon Creek. Twelve sites within the dry channel and twelve ephemeral pools in Leon Creek were surveyed for vegetation between late March and mid-May 2020 in central Texas, USA. Plant species were similar between the dry channel and pools over a 1.5 km distance indicating that habitats are similar in both allowing the occurrence of upland, facultative, and wetland plant species. A total of 114 species of multiple functional groups were documented in this study. Panicum virgatum had greater coverage at >20% in both the ephemeral channel and pools compared to all other plant species. Ten plant species were dominant with a mean coverage of >3% and no difference was observed for dominant species in the dry channel and pools. The coverage of perennial species were significantly greater in the dry channel and pools but annual coverage in the dry channel was similar to perennial coverage in the pools. Graminoids and forbs were significantly greater in coverage compared to trees, shrubs, vines, and ferns in both the dry channel and pools. Shrub and tree cover was rare accounting for <0.3% coverage. Native species coverage was significantly greater compared to non-native species in the dry channel and pools. Droughts, flash floods, and scouring events appear to promote perennial graminoids and forbs dominance in Leon Creek with shrubs and trees being uncommon. The results of this study is the first to evaluate vegetation in an ephemeral channel and pools in central Texas and provides current vegetation composition providing information that can be used to compare changes to vegetation in the future.

Automated summary

Ephemeral streams in central Texas have been overlooked despite their common occurrence. This study examined the vegetation composition in an ephemeral dry stream channel and pools, revealing similarities in plant species between the two habitats. Panicum virgatum emerged as the dominant species, with a higher coverage than other plants. Perennial grasses and forbs were more abundant than annuals, and graminoids and forbs had greater coverage compared to trees, shrubs, vines, and ferns. Native species had greater coverage than non-native species. Droughts, flash floods, and scouring events were found to promote the dominance of perennial grasses and forbs in Leon Creek.