Fire and competition in a southern California grassland: impacts on the rare forb Erodium macrophyllum

  • Published source details Gillespie I.G. & Allen E.B. (2004) Fire and competition in a southern California grassland: impacts on the rare forb Erodium macrophyllum. Journal of Applied Ecology, 41, 643-652.


A study was undertaken to investigate how prescribed spring burns and non-native species in a southern California grassland impact the grassland plant community, specifically examining how these factors impacted the rare forb, large-leaved filaree Erodium macrophyllum. In association with this, a glasshouse study was undertaken to assess the effects of competion from the native purple needlegrass Nassella pulchra and non-native wild oat Avena fatua on Erodium macrophyllum growth.

The glasshouse experiment was conducted at the University of California (Riverside).

A seven-factor randomized block design, replicated five times, was used. Treatments were three different densities of A.fatua and N.pulchra around a single E.macrophyllum seedling, with E.macrophyllum growing alone (as a control). Densities were two, four or six 'competitors' surrounding an E.macrophyllum seedling.

On 20 May 2002, seedlings were transplanted into soil-filled plastic pots (30 cm diameter, 28 cm deep) approximately 4 days after germinating. A E.macrophyllum seedling was planted into the centre of the pot with the appropriate density of competitors, equi-distant from each other. The pots were watered every other day. On 2 July 2002 height and width (widest point) of all E.macrophyllum plants were measured and above-ground biomass havested, dried and weighed.

All densities of A.fatua decreased average E. macrophyllum dry biomass (2 Avena plants: 10 g; 4 plants: 5 g; 6 plants: 25 g) compared with controls E. macrophyllum (average 34 g). In contrast, there was no difference in biomass between E.macrophyllum growing with N.pulchra at any of the three densities. E. macrophyllum growing with six A.fatua plants per pot resulted in the largest height-width ratio (c.1.4). No other competitors at the three densities trialled had an effect on this variable.

This study showed that the non-native A.fatua competitively suppresses E. macrophyllum, indicating that poor performance of E. macrophyllum in a field experiment in an associated field experiment was propbaly due to exotic grass competition.

Note: If using or referring to this published study, please read and quote the original paper. The original paper can be viewed at:

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