Spread of exotic grass in grazed native grass pastures and responses of insect communities

Island species and habitats are particularly vulnerable to human disturbances, and anthropogenic changes are increasingly overwriting natural island biogeographic patterns.However, quantitative comparisons of how native and alien assemblages respond to human disturbances are scarce. Using data from 6,252 species (vertebrates, invertebrates and plants), 7,731 sites and 80 islands, we model how land-use change, human population density and distance to the nearest road affect local assemblages of alien and native species on islands. We found that these pressures reduce both richness and abundance of natives, whereas the number and abundance of alien species are high in plantation forests and agricultural or urban sites. In contrast to the long-established pattern for native species, more isolated islands have a higher number of alien species across most land uses than do less isolated islands. Finally, our models of compositional similarity comparing sites in minimallydisturbed primary vegetation with other land uses, and sites within the same land use show that alien species play a major role in the turnover and homogenization of island assemblages.The declines of native species on islands in the face of human pressures, and the proneness to invasions of even the more remote islands, highlight the need to reduce the intensity of human pressures on islands and so far as possible to prevent the establishment of alien species.

show abstract

Section: Discussionmentioning

confidence: 82%

Effects of land-use change and related pressures on alien and native subsets of island communities

Sánchez-Ortiz

Taylor

Palma

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…The lower ADG of steers documented in Monroe et al. (2017) may have been because of the higher proportion of lower‐yielding LB in their mixed NWSG sward coupled with the incomplete eradication of bermudagrass, which approximately doubled in coverage from Year 1 to Year 2 of their experiment (Monroe, Hill, & Martin, 2017). Heifer calves on CONT and HEAVY had similar ADG (0.89 and 0.81 kg d −1 , respectively), and there was no year effect or year × treatment interaction (Table 6).…”

Section: Resultsmentioning

confidence: 99%

Continuous grazing of mixed native warm‐season grass in the fescue belt

et al. 2020

View full text Add to dashboard Cite

Continuous, season-long (May-August) grazing is the most commonly used grazing strategy among tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] belt beef (Bos taurus) producers. However, little information is available regarding the feasibility of managing native warm-season grass (NWSG) pastures in this region with continuous, season-long grazing. We compared stand sustainability, beef cattle performance, and pasture production between continuous (CONT), season-long grazing and heavy-early (HEAVY), a modified continuous grazing strategy, on mixed-NWSG pastures. Heavy-early was designed to match the growth curve of NWSG, with an initial stocking target of 1.25 times the CONT density until 25 June, at which time stocking was reduced to 0.75 times the CONT density. Pastures were mixed big bluestem (Andropogon gerardii Vitman), indiangrass [Sorghastrum nutans (L.) Nash], and little bluestem [Schizachyrium scoparium (Michx.)]. The plant population (plants m −2) was similar between treatments, but years differed (P < .001), with a 35% reduction from 2017, the third and final year of grazing, to 2018. Despite the decline in plant density, overall tiller density (tillers m −2) increased 14%, indicating that the grazing strategies were likely sustainable. The grazing strategies had similar (P > .05) average daily gain (ADG; kg d −1), animal-days ha −1 , and total gain (kg ha −1). Weaned steer ADG was 0.98 kg d −1 for CONT and 0.89 kg d −1 for HEAVY. Total gain was 379 kg ha −1 for CONT and 334 kg ha −1 for HEAVY. Continuous grazing appears to be an appropriate strategy for managing NWSG pastures in the Fescue Belt.

show abstract

“…Alien species are much more common on human-dominated sites than on more natural sites (especially minimally-used primary vegetation), as expected from their tolerance to disturbed conditions, their colonisation ability and the fact that they may need to displace native species in undisturbed sites [ 15 ]. The high abundance of aliens in agricultural sites and cities ( Fig 1 ) has been highlighted previously [ 25 , 86 – 90 ], and often follows from intentional introduction (e.g., for livestock forage [ 91 ]; or, in cities, for trade [ 92 ] and ornamental gardening [ 93 ]). Overall, land-use change boosted alien abundance more than alien richness, suggesting that those alien species able to tolerate the extreme conditions of disturbed sites can become very successful and abundant [ 94 , 95 ] even if few species are introduced and become established–perhaps also partly because island natives are poor competitors in human-dominated land uses [ 15 ].…”

Section: Discussionmentioning

confidence: 91%

Effects of land-use change and related pressures on alien and native subsets of island communities

et al. 2020

View full text Add to dashboard Cite

Island species and habitats are particularly vulnerable to human disturbances, and anthropogenic changes are increasingly overwriting natural island biogeographic patterns. However, quantitative comparisons of how native and alien assemblages respond to human disturbances are scarce. Using data from 6,242 species of vertebrates, invertebrates and plants, from 7,718 sites on 81 islands, we model how land-use change, human population density and distance to the nearest road affect local assemblages of alien and native species on islands. We found that land-use change reduces both richness and abundance of native species, whereas the number and abundance of alien species are high in plantation forests and agricultural or urban sites. In contrast to the long-established pattern for native species (i.e., decline in species number with island isolation), more isolated islands have more alien species across most land uses than do less isolated islands. We show that alien species play a major role in the turnover of island assemblages: our models show that aliens outnumber natives among the species present at disturbed sites but absent from minimally-disturbed primary vegetation. Finally, we found a homogenization pattern for both native and alien assemblages across sites within most land uses. The declines of native species on islands in the face of human pressures, and the particular proneness to invasions of the more remote islands, highlight the need to reduce the intensity of human pressures on islands and to prevent the introduction and establishment of alien species.

show abstract

Spread of exotic grass in grazed native grass pastures and responses of insect communities

Cited by 10 publications

References 82 publications

Effects of land-use change and related pressures on alien and native subsets of island communities

Effects of land-use change and related pressures on alien and native subsets of island communities

Continuous grazing of mixed native warm‐season grass in the fescue belt

Effects of land-use change and related pressures on alien and native subsets of island communities

Contact Info

Product

Resources

About