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The effects of timing of grazing on plant and arthropod communities in high-elevation grasslands.

Davis SC, Burkle LA, Cross WF, Cutting KA - PLoS ONE (2014)

Bottom Line: In the upland grassland experiment, we found that both early and late grazing treatments reduced forb biomass, whereas graminoid biomass was only reduced with late grazing.Grazing earlier in the growing season versus later did not result in greater recovery of graminoid or forb biomass as expected.Both grazing treatments also reduced end-of-season total arthropod and Hemiptera densities and Hemiptera biomass in both grassland habitat types.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Montana State University, Bozeman, Montana, United States of America.

ABSTRACT
Livestock grazing can be used as a key management tool for maintaining healthy ecosystems. However, the effectiveness of using grazing to modify habitat for species of conservation concern depends on how the grazing regime is implemented. Timing of grazing is one grazing regime component that is less understood than grazing intensity and grazer identity, but is predicted to have important implications for plant and higher trophic level responses. We experimentally assessed how timing of cattle grazing affected plant and arthropod communities in high-elevation grasslands of southwest Montana to better evaluate its use as a tool for multi-trophic level management. We manipulated timing of grazing, with one grazing treatment beginning in mid-June and the other in mid-July, in two experiments conducted in different grassland habitat types (i.e., wet meadow and upland) in 2011 and 2012. In the upland grassland experiment, we found that both early and late grazing treatments reduced forb biomass, whereas graminoid biomass was only reduced with late grazing. Grazing earlier in the growing season versus later did not result in greater recovery of graminoid or forb biomass as expected. In addition, the density of the most ubiquitous grassland arthropod order (Hemiptera) was reduced by both grazing treatments in upland grasslands. A comparison of end-of-season plant responses to grazing in upland versus wet meadow grasslands revealed that grazing reduced graminoid biomass in the wet meadow and forb biomass in the upland, irrespective of timing of grazing. Both grazing treatments also reduced end-of-season total arthropod and Hemiptera densities and Hemiptera biomass in both grassland habitat types. Our results indicate that both early and late season herbivory affect many plant and arthropod characteristics in a similar manner, but grazing earlier may negatively impact species of conservation concern requiring forage earlier in the growing season.

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Related in: MedlinePlus

End-of-season comparisons for key grassland variables for ungrazed wet meadow and upland grasslands.End-of-season (late August) values for a) graminoid biomass, b) forb biomass, c) arthropod density, and d) arthropod biomass are untransformed means ± 1 SE. Wet meadow grasslands were sampled in 2011 and upland grasslands in 2012. * Indicates a significant difference between wet meadow and upland grasslands (p<0.05 from paired t-tests, n = 3). All variables were square-root transformed +0.5 for t-tests.
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pone-0110460-g001: End-of-season comparisons for key grassland variables for ungrazed wet meadow and upland grasslands.End-of-season (late August) values for a) graminoid biomass, b) forb biomass, c) arthropod density, and d) arthropod biomass are untransformed means ± 1 SE. Wet meadow grasslands were sampled in 2011 and upland grasslands in 2012. * Indicates a significant difference between wet meadow and upland grasslands (p<0.05 from paired t-tests, n = 3). All variables were square-root transformed +0.5 for t-tests.

Mentions: At the end of the season, ungrazed wet meadow and upland grassland habitats differed substantially in many plant and arthropod characteristics. The wet meadow grassland had greater graminoid and forb biomass, as well as total arthropod density (Figure 1a, b, c). In contrast, there were no inter-habitat differences in total arthropod biomass (Figure 1d). Soil moisture differed significantly between grassland habitat types (Kolmogorov-Smirnov test; p<0.05; Figure 2) with greater cumulative soil moisture in wet meadows (mean of 116% and median of 115%) versus uplands (mean of 81% and median of 82%; Figure 2). Total arthropod density was positively correlated with both graminoid (r = 0.06, p = 0.012) and forb biomass (r = 0.55, p = 0.03) in the wet meadow grassland. In contrast, neither graminoid nor forb biomass was significantly correlated with arthropod density in the upland grassland. Cumulative soil moisture was negatively correlated with end-of-season graminoid (r = −0.44, p = 0.02) and forb biomass (r = −0.49, p = 0.007) in ungrazed plots in the upland grassland. All other correlations were non-significant.


The effects of timing of grazing on plant and arthropod communities in high-elevation grasslands.

Davis SC, Burkle LA, Cross WF, Cutting KA - PLoS ONE (2014)

End-of-season comparisons for key grassland variables for ungrazed wet meadow and upland grasslands.End-of-season (late August) values for a) graminoid biomass, b) forb biomass, c) arthropod density, and d) arthropod biomass are untransformed means ± 1 SE. Wet meadow grasslands were sampled in 2011 and upland grasslands in 2012. * Indicates a significant difference between wet meadow and upland grasslands (p<0.05 from paired t-tests, n = 3). All variables were square-root transformed +0.5 for t-tests.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4206520&req=5

pone-0110460-g001: End-of-season comparisons for key grassland variables for ungrazed wet meadow and upland grasslands.End-of-season (late August) values for a) graminoid biomass, b) forb biomass, c) arthropod density, and d) arthropod biomass are untransformed means ± 1 SE. Wet meadow grasslands were sampled in 2011 and upland grasslands in 2012. * Indicates a significant difference between wet meadow and upland grasslands (p<0.05 from paired t-tests, n = 3). All variables were square-root transformed +0.5 for t-tests.
Mentions: At the end of the season, ungrazed wet meadow and upland grassland habitats differed substantially in many plant and arthropod characteristics. The wet meadow grassland had greater graminoid and forb biomass, as well as total arthropod density (Figure 1a, b, c). In contrast, there were no inter-habitat differences in total arthropod biomass (Figure 1d). Soil moisture differed significantly between grassland habitat types (Kolmogorov-Smirnov test; p<0.05; Figure 2) with greater cumulative soil moisture in wet meadows (mean of 116% and median of 115%) versus uplands (mean of 81% and median of 82%; Figure 2). Total arthropod density was positively correlated with both graminoid (r = 0.06, p = 0.012) and forb biomass (r = 0.55, p = 0.03) in the wet meadow grassland. In contrast, neither graminoid nor forb biomass was significantly correlated with arthropod density in the upland grassland. Cumulative soil moisture was negatively correlated with end-of-season graminoid (r = −0.44, p = 0.02) and forb biomass (r = −0.49, p = 0.007) in ungrazed plots in the upland grassland. All other correlations were non-significant.

Bottom Line: In the upland grassland experiment, we found that both early and late grazing treatments reduced forb biomass, whereas graminoid biomass was only reduced with late grazing.Grazing earlier in the growing season versus later did not result in greater recovery of graminoid or forb biomass as expected.Both grazing treatments also reduced end-of-season total arthropod and Hemiptera densities and Hemiptera biomass in both grassland habitat types.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Montana State University, Bozeman, Montana, United States of America.

ABSTRACT
Livestock grazing can be used as a key management tool for maintaining healthy ecosystems. However, the effectiveness of using grazing to modify habitat for species of conservation concern depends on how the grazing regime is implemented. Timing of grazing is one grazing regime component that is less understood than grazing intensity and grazer identity, but is predicted to have important implications for plant and higher trophic level responses. We experimentally assessed how timing of cattle grazing affected plant and arthropod communities in high-elevation grasslands of southwest Montana to better evaluate its use as a tool for multi-trophic level management. We manipulated timing of grazing, with one grazing treatment beginning in mid-June and the other in mid-July, in two experiments conducted in different grassland habitat types (i.e., wet meadow and upland) in 2011 and 2012. In the upland grassland experiment, we found that both early and late grazing treatments reduced forb biomass, whereas graminoid biomass was only reduced with late grazing. Grazing earlier in the growing season versus later did not result in greater recovery of graminoid or forb biomass as expected. In addition, the density of the most ubiquitous grassland arthropod order (Hemiptera) was reduced by both grazing treatments in upland grasslands. A comparison of end-of-season plant responses to grazing in upland versus wet meadow grasslands revealed that grazing reduced graminoid biomass in the wet meadow and forb biomass in the upland, irrespective of timing of grazing. Both grazing treatments also reduced end-of-season total arthropod and Hemiptera densities and Hemiptera biomass in both grassland habitat types. Our results indicate that both early and late season herbivory affect many plant and arthropod characteristics in a similar manner, but grazing earlier may negatively impact species of conservation concern requiring forage earlier in the growing season.

Show MeSH
Related in: MedlinePlus