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Aim Native plant communities are susceptible to climate anomalies, which would favour the invasion of non-native species. However, climate anomalies may also provide opportunities for detecting non-native plants at a regional scale using remote sensing. Based on this mechanism, we propose a direct and effective remote sensing approach to map the abundance of South African Eragrostis lehmanniana Nees (Lehmann lovegrass), a highly invasive, non-native plant in the desert grasslands of southwestern North America.

Location The desert grassland of Fort Huachuca Military Reservation (31 degrees 34’N, 110 degrees 26’W) in southern Arizona, USA.

Methods Simple linear regression models were used to examine the relationships between additional (comparing to the normal level) remotely sensed greenness (delta Enhanced Vegetation Index (Delta EVI) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS)), and field actual (g m(-2)) and percentage (%) biomass of E. lehmanniana in an abnormal wet, cool period in October 2000.

Results There was a strong and positive agreement (P < 0.005) between Delta EVI and field observations (R-2 = 0.72 and 0.64 for actual and percentage biomass of E. lehmanniana, respectively). These relationships allowed us to estimate the abundance of E. lehmanniana in the desert grassland.

Main conclusions Phenology of native grass communities is quite similar to systems dominated by E. lehmanniana but responses differ when there are substantial amounts of precipitation in cool seasons. Eragrostis lehmanniana can produce significant amount of new tissues and seeds with sufficient cool season moisture, while native grasses are still in senescence or dormancy. Therefore, amplitude of Delta EVI during wet, cool seasons would indicate the abundance of E. lehmanniana. Long-term climate records denote an amplification of cool season precipitation in the southwestern USA. This regional climatic trend should allow us to monitor E. lehmanniana and possibly other non-native species frequently in this vast arid region.