Evaluating ecosystem services provided by non-native species: an experimental test in California grasslands

Published source details Stein C., Hallett L.M., Harpole W.S. & Suding K.N. (2014) Evaluating ecosystem services provided by non-native species: an experimental test in California grasslands. PLoS ONE, 9, e75396.
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This study is summarised as evidence for the following.

	Action	Category
	Soil: Use fewer grazers Action Link
	Other biodiversity: Use fewer grazers Action Link
	Other biodiversity: Use grazers to manage vegetation Action Link

Soil: Use fewer grazers

A replicated, randomized, controlled study in 2008–2010 in sown plots in lowland grasslands in northern California, USA, found no difference in nitrogen availability or soil respiration between plots grazed at medium intensity, compared to high intensity. Nutrients: There was no difference in nitrogen availability between plots grazed at medium or high intensity (0.2–0.3 g N/g soil/day). Greenhouse gases: There were no differences in soil respiration between plots grazed at a medium or high intensity (245–315 µmol CO₂/min/g soil). Methods: In 2007 four experimental blocks were established across two pastures. Each block was split into eighteen plots and subjected to one of three treatments: no manipulation; mowing and trampling by cattle to simulate medium cattle grazing; mowing and trampling by cattle to simulate heavy cattle grazing. Soil nitrogen availability was measured in December 2009–March 2010 using ion exchange resin bags. Soil respiration was measured in February 2010.
Other biodiversity: Use fewer grazers

A replicated, randomized, controlled study in 2008–2010 in grasslands in northern California, USA, found that plant diversity did not vary between plots grazed at different intensities, but that cover of native species was higher in plots grazed at lower intensities, compared to those grazed at higher intensities, for one of three plant assemblages. Plants: Plant diversity did not differ between plots with different grazing intensities (results reported as Shannon diversity). Cover of native species was higher in plots with medium, rather than high, grazing intensity in plots sown with native perennial grasses (17% vs 22% cover), but there was no difference in plots sown with two types of non-native assemblages (2–3%). Methods: In 2007 four experimental blocks were established across two pastures. Each block was split into three areas, sown with one of three vegetation types: native perennial grasses, non-native annual forage grasses, or a non-native, non-edible annual weed. These were then divided into six plots, which were subjected to one of three treatments, each replicated twice: no manipulation, mowing and trampling by cattle to simulate medium cattle grazing, or mowing and trampling by cattle to simulate heavy cattle grazing. Plants were surveyed in a 1 m² quadrat in May 2008–2010.
Other biodiversity: Use grazers to manage vegetation

A replicated, randomized, controlled study in 2008–2010 in lowland grasslands in northern California, USA, found that plant diversity did not differ between plots with simulated grazing and ungrazed plots. The cover of native species was lower in plots with simulated grazing, compared to ungrazed plots, for one of three plant assemblages. Plants: Plant diversity did not differ between plots with simulated grazing and ungrazed plots (results reported as Shannon diversity). Cover of native species was lower in plots with simulated grazing, compared to ungrazed plots, when plots were sown with native perennial grasses (17–22% vs 59% cover), but there was no difference in plots sown with two types of non-native assemblages (1–3%). Methods: In 2007, four experimental blocks were established across two pastures. Each block was split into three areas, sown with one of three vegetation types: native perennial grasses, non-native annual forage grasses, and a non-native, non-edible annual weed. These were then divided into six plots, which were subjected to one of three treatments, each replicated twice: no manipulation, mowing and trampling by cattle to simulate medium grazing, or to simulate heavy grazing. Plants were surveyed in a 1 m² quadrat in May 2008–2010.