ORIGINAL ARTICLE: Response of semi-desert grasslands invaded by non-native grasses to altered disturbance regimes

Aim: Using a long-term data set we investigated the response of semi-desert grasslands to altered disturbance regimes in conjunction with climate patterns. Specifically, we were interested in the response of a non-native grass (Eragrostis lehmanniana), mesquite (Prosopis velutina), and native specie...

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Veröffentlicht in:Journal of biogeography 2005-05, Vol.32 (5), p.895-902
Hauptverfasser: Geiger, Erika L, McPherson, Guy R
Format: Artikel
Sprache:eng
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Zusammenfassung:Aim: Using a long-term data set we investigated the response of semi-desert grasslands to altered disturbance regimes in conjunction with climate patterns. Specifically, we were interested in the response of a non-native grass (Eragrostis lehmanniana), mesquite (Prosopis velutina), and native species to the reintroduction of fire and removal of livestock. Location: The study site is located on the 45,360-ha Buenos Aires National Wildlife Refuge (31 degree 32' N, 110 degree 30' W) in southern Arizona, USA. In 1985, livestock were removed and prescribed fires were reintroduced to this semi-desert grassland dominated by non-native grasses and encroaching mesquite trees. Methods: Plant species cover was monitored along 38, 30-m transects five times over a period of 15 years. Data were analysed using principal components analysis on the variance-covariance and correlation matrix, multivariate analysis of variance for changes over time in relation to environmental data, and analysis of variance for altered disturbance regimes. Results: Reintroduction of fire and removal of livestock have not led to an increase in native species diversity or a decrease in non-native grasses or mesquite. The cover of non-native grass was influenced by soil type in 1993. Main conclusions: Variability of plant community richness, diversity, and cover over time appear to be most closely linked to fluctuations in precipitation rather than human-altered disturbance regimes. The effects of altered grazing and fire regimes are likely confounded by complex interactions with climatic factors in systems significantly altered from their original physiognomy.
ISSN:0305-0270
1365-2699
DOI:10.1111/j.1365-2699.2004.01235.x