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Individual study: Effects of clipping, broadleaf herbicide and native grass density in restoration of native grasses and clovers Trifolium spp. near Winters, California, USA

Published source details

Lulow M.E. (2008) Restoration of California native grasses and clovers: the roles of clipping, broadleaf herbicide, and native grass density. Restoration Ecology, 16, 584-593

Summary

Although native clovers Trifolium species are highly diverse and often frequent in California grasslands, they are seldom seeded in grassland restoration attempts within the State. A trial was undertaken near Winters town (38°38″01′N, 122°03″05′W) to identify practical management options that may enhance growth of native bunchgrasses plugs and seeded native clovers, and to assess if native and non-native clovers respond differently to management.

The study was undertaken on grassland dominated by two non-native annuals, Italian ryegrass Lolium multiflorum and soft brome Bromus hordeaceus. In 2001, a late-spring burn (a common restoration preparation practice to reduce non-native annual grass seed) was conducted.

In autumn, 35 (1.5 x 1.5 m) plots were established and fenced to exclude rabbits and cattle. Five native bunchgrass species were planted (random plots) in February at 22 and 48 plugs/m2.
 
Native clovers (4 species) and non-native commercial varieties (4) were sown in November 2002 and 2003. Treatments (plus controls) were applied (randomized design; 7 treatment combinations, 5 replicates each):
 
1) spring clipping (by brush-cutter) twice each spring (February-April) to 6-10 cm height;
2) broadleaf herbicide (2,4-D) applied twice (December 2001; March 2002).
 
In 2001, data were collected on cover of native and non-native grasses, and non-native long-beaked stork’s-bill Erodium botrys (almost the only forb present), and in 2002-2003, including clovers.

Of planted bunchgrass species, only the two Nasella spp. established well, accounting for 98% of native grass cover in autumn 2003. Failure of the other species was attributed to a dry spring subsequent to planting. Clipping did not influence bunchgrass cover, but it enhanced growth of both native and non-native clovers.
 
E. botrys was more-or-less eradicated in herbicide-treated plots. Although sprayed prior to sowing, a strong negative residual effect was apparent on native clovers (density 55% less in no-clip/herbicide vs. no-clip/no herbicide treatment in spring 2003). Native and non-native clovers responded similarly to clipping, establishing at similar densities (around 27-30 individual/m² in no clip/herbicide; and 55-60 in clip/herbicide treatments).
 
There was no effect of bunchgrass plug-planting density (which declined to an average to 9 and 25 individuals/m2 by autumn 2003)on clovers but the higher density reduced non-native grass cover.
 
 
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://onlinelibrary.wiley.com/doi/10.1111/j.1526-100X.2007.00334.x/full