Plant, Small Mammal, and Avian Diversity following Control of Honey Mesquite

Abstract

The effects of herbicide applications to kill honey mesquite (Prosopis ghdulosa Torr.) on community diversity are poorly documented. Our objective was to test the hypothesis that herbicide application to kill honey mesquite would reduce plant and vertebrate species richness and diversity. A 1:l mixture of triclopyr ([(3,!!,6-trichloro-2-pyridinyl) oxylacetic acid] + picloram (4-amino-3,5,6tricholopicolinic acid) was applied to three 13-ha plots during 1992 and to 3 additional plots in 1993. Mesquite and forb canopy cover in the zone I 1 m from the soil surface were lower within treated plots than in control plots (n = 3) following the 1992 and 1993 treatments. Grass canopy cover did not differ between herbicide-treated plots and control plots. Vegetation species richness and evenness, Shannon's index, beta diversity, and proportion of rare plant species did not differ between controls and sites treated during 1992 and 1993. Rodent and avian relative frequency, richness, and diversity were not different on 1992 herbicide treatment plots and controls. Based on these results, application of triclopyr + picloram in mesquite-mixed grass communities in the Texas Coastal Bend does not appear to reduce plant and vertebrate species richness and diversity within the first 2 years after treatment. However, our results should be interpreted cautiously because (1) annual rainfall was 16 % above the annual average during the study and (2) limited replication possibly reduced statistical power to detect differences.

Adherence to guidelines for self-treatment of mild hypoglycaemia in type 1 diabetes

“…Cattle grazing in Arizona has been shown to reduce abundance and community structure of rodents due to depletion of the grass layer and trampling damage (Hayward et al 1997), but deer have little effect on the grass layer and cause less soil disturbance than cattle. Overall it is not surprising that we observed little response by rodent populations to changes in the level of deer browsing because even fire and extensive mechanical brush reduction have been shown to have minimal effects on abundance of rodents in arid ecosystems, and any changes that do occur tend to be species specific (Guthery et al 1979, Nolte and Fulbright 1997, Fitzgerald et al 2001, Valone et al 2002, Jones et al 2003).…”

Plant and Small Vertebrate Composition and Diversity 36–39 Years After Root Plowing

“…Percent canopy cover was used in calculations of species richness (species Á 5.6 m À2 ), Shannon's index, and evenness for herbaceous plants. Beta diversity for woody and herbaceous plants was estimated by calculating the mean of the Jaccard's similarity index values computed for all possible pairs of the 14 transects within each 4-ha root-plowed site and each 4-ha untreated site (Nolte and Fulbright 1997;Balvanera et al 2002). The number of species within each transect was based on canopy cover estimates.…”

Review. Impact of grazing on plant communities in forestry areas

“…The use of other clearing techniques (mechanical or chemical) is not always effective Table 2. Some characteristics of competitive, stress tolerant and ruderal plants (Grime, 1977) at increasing the density of herbaceous plants ( Morton and Melgoza, 1991;Bartolomé et al, 1994;Nolte and Fulbright, 1997) either due to the influence of topo-edaphological (Archer and Smeins, 1991) and climatic factors (Bozzo et al, 1992;Bartolomé et al, 1994), and to the influence of the dominant shrubby vegetation (Ratliff et al, 1991) on the response of herbaceous plants to shrub control.…”