Effects of a natural precipitation gradient on fish and macroinvertebrate assemblages in coastal streams

Anthropogenic climate change is expected to increase the aridity of many regions of the world. Surface water ecosystems are particularly vulnerable to changes in the water-cycle and may suffer adverse impacts in affected regions. To enhance our understanding of how freshwater communities will respond to predicted shifts in water-cycle dynamics, we employed a space for time approach along a natural precipitation gradient on the Texas Coastal Prairie. In the spring of 2017, we conducted surveys of 10 USGS-gauged, wadeable streams spanning a semi-arid to sub-humid rainfall gradient; we measured nutrients, water chemistry, habitat characteristics, benthic macroinvertebrates, and fish communities. Fish diversity correlated positively with precipitation and was negatively correlated with conductivity. Macroinvertebrate diversity peaked within the middle of the gradient. Semi-arid fish and invertebrate communities were dominated by euryhaline and live-bearing taxa. Sub-humid communities contained environmentally sensitive trichopterans and ephemeropterans as well as a variety of predatory fish which may impose top-down controls on primary consumers. These results warn that aridification coincides with the loss of competitive and environmentally sensitive taxa which could yield less desirable community states.

Rediscovery, new county records, and distribution notes for Chloris texensis (Poaceae) in Texas, U.S.A.

Rediscovery of the Texas endemic Chloris texensis in Brazoria County, and new records for Ft. Bend, Matagorda, and Waller counties are documented. Collection records outside the narrow Upper Coastal Prairie distribution are also reviewed.

Dichanthium aristatum (angelton bluestem).

Dichanthium aristatum is a perennial grass native to Asia and parts of India and naturalized in the tropics and subtropics worldwide through its use as a forage/fodder species. It is reported as invasive in USA (Texas and Hawaii) and French Polynesia due to its prolific seed production, a high density of reproductive shoots and its fast growth. D. aristatum is also reported as invasive in heavily grazed grasslands. In Texas it invades and outcompetes native grasses in coastal prairie communities. D. aristatum has been categorized as an F1 (Fundamental Invasiveness Index 1) species: invasive in disturbed and natural habitats; affecting native species and the biodiversity by altering the native vegetation and habitats by outcompeting the native species; or causing economic damage. Although D. aristatum is considered potentially invasive in Cuba, it has been reported that despite naturalization of the species, it is not frequent, and is neither aggressive nor expanding in the country.

Response of Deeproot Sedge (Cyperus entrerianus) to Herbicide and Prescribed Fire in Texas Coastal Prairie

Introduced accidentally from South America, deeproot sedge is rapidly expanding in a variety of habitats throughout the southeastern United States. Of particular concern is its rapid expansion, naturalization, and formation of monocultures in Texas coastal prairie, one of the most imperiled temperate ecoregions in North America. The objective of this research was to examine how deeproot sedge responds to prescribed fire, to the herbicide imazapic, and to treatment combinations of both. Combinations of prescribed fire and imazapic treatments and imazapic-only treatments effectively reduced deeproot sedge cover and frequency. However, plots exposed to dormant season fires (with no imazapic) had greater deeproot sedge cover after burn treatments were applied, indicating that coastal prairie management using only dormant season prescribed fire will not work toward reduction or management of this exotic invasive species. Although deeproot sedge cover was often reduced in fire–imazapic treatment combinations, it was still present in treatment plots. Moreover, desirable functional plant groups (i.e., native bunchgrasses) did not respond positively to the fire–imazapic treatments, but in some instances, woody plant coverage increased. Repeated, long-term approaches using integrated and coordinated efforts with multiple treatment options will be necessary to restore community structure to desired compositional levels. Such integrated approaches should be effective in reducing deeproot sedge frequency, cover, and extent to more manageable levels throughout its introduced geographic range.