Sticklebacks
نویسندگان
چکیده
together with fire and mowing. The team found that native perennials reduced soil moisture, soil nitrogen, and light to lower levels than did exotic annuals. This ability to outcompete the exotic species for these resources means that native perennials should be able to increase in abundance. This suggests that the current rarity of native perennials at the researchers’ site is caused by natives being unable to penetrate the stands of exotic annuals and not by exotic annuals being superior resource competitors. Annual species tend to allocate fewer resources to roots and more resources to leaf and seed production, a trade-off that should make annuals faster growers and better exploiters of disturbances but weaker competitors for below-ground resources than perennials. The annuals did better under all conditions of disturbance: gophers, fire and mowing. If a trade-off between competitive ability for California grassland plants is proven, superior competitors would be slow to recover from the disturbance once driven to low densities. At another Californian site, inside a nature reserve, the two dominant native perennial bunchgrasses took 15–20 years to reappear anywhere in a field after it was abandoned to agriculture and a further 25–35 years before they obtain peak abundances, even if fields are surrounded by intact native grasslands, the researchers note. If exotic annuals were competitively dominant, re-establishment of the native flora would depend on the eradication and continued quarantine of exotics: ‘two difficult and costly ventures,’ the researchers say. But if exotic annuals are not superior competitors and dominate because of prior disturbance and the low dispersal abilities, seed production and extreme current rarity of native perennials, ‘it may be feasible to restore native California grassland flora to at least parts of its former range,’ the team say. Quick guide
منابع مشابه
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ورودعنوان ژورنال:
- Current Biology
دوره 13 شماره
صفحات -
تاریخ انتشار 2003