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CCBER's restoration sites offer many opportunities to explore and evaluate the enormous challenge of enhancing ecological resistance and creating diverse self-sustaining ecosystems. |
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Another way in which we are trying to reduce non-native grassland species and promote native species in California grassland is through winter livestock grazing. With ICESS scientist/CCS lecturer Claudia Tyler, we are trying this at UCSB’s Sedgwick Reserve. We have found that cows reduce the invasive grass ripgut brome, on one of the two soil types where our experiment is ongoing. But responses by native species are mixed and depend on the rainfall for that year of the study. This year, for example, was a great year for native wildflowers and we saw a strong increase in native forbs in our grazed plots compared to the ungrazed plots on one soil type. This response was much weaker in 2006 and 2007, both years where non-native grasses did extremely well and native wildflowers were sparse. In those years, grazing reduced ripgut but did not lead to a response by native grasses or wildflowers probably due to germination conditions. Thus, grazing may effectively reduce many unwanted non-native species, but without consistently promoting native perennial grasses or forbs, it does not build community resistance to reinvasion. More research is needed on how to promote native perennial grasses that by themselves could reduce the persistence of undesirable exotic species. Such an opportunity could exist on the new South Parcel restoration site where a few remnant patches of native grasses remain within a sea of non-native invaders some of which are very hard to control.
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Dead thatch on ground in mid summer. |
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Dense ripgut grass with non-native
wild radish in the middle. |
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A major goal of the restoration practitioner is to create a sustainable ecosystem where, within a range of climate variability and natural disturbance, species composition and ecosystem processes will stay within certain bounds. Invasive non-native species challenge our ability to achieve this goal. However, in many sites, creating plant communities with strong resistance to the establishment of invaders can contribute to this goal. CCBER’s restoration sites offer many opportunities to explore and evaluate the enormous challenge of enhancing ecological resistance and creating diverse self-sustaining ecosystems.
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Grazing exclosure plot on terrace soil site at Sedgwick. Plot has been ungrazed since 1995
and is dominated by ripgut brome grass and its
thatch. Spring 2008 photo by
Carla D'Antonio. |
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Nearby plot that has been grazed annually
since 1995 in the winter only. Very little
ripgut grass is present.
Spring 2008 photo by Carla D’Antonio. |
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