Research Summaries

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McDaniel, K. C. and J. P. Taylor.
2003. Saltcedar recovery after herbicide-burn and mechanical clearing practices. Journal of Range Management 56:439-445.

Mechanical clearing and herbicide-burn treatments were compared to evaluate saltcedar (Tamarix chinensis Lour.) control and recovery along the Rio Grande on the Bosque del Apache National Wildlife Refuge, Socorro, NM. The herbicide-burn treatment included an aerial application of imazapyr + glyphosate (0.6 lb of each active ingredient / hectare) followed 3 years later by a prescription broadcast fire that eliminated > 99% of the standing dead stems. Six years after initial herbicide application, saltcedar mortality was 93%. Mechanical saltcedar clearing entailed removing aerial trunks and stems by blading, stacking and burning debris, followed by removal of underground plant portions (roots and crowns) by plowing, raking, and burning stacked material. Saltcedar mortality averaged 70%, which was deemed unsatisfactory. Thus, root plowing, raking, and pile burning was repeated. Three years later, after the second mechanical clearing, saltcedar mortality was 97%. Costs for the herbicide-burn treatment averaged $283 per hectare, whereas the mechanical control costs were $884 per hectare for the first surface and root clearing and an additional $585 for the second root clearing. Riparian managers should consider environmental conditions and restoration strategies prior to selecting a saltcedar control approach. Although control costs were significantly lower for the herbicide-burn treatment compared to mechanical clearing in this study, the choice of methods should always consider alternative control strategies for saltcedar. Frequently, combinations of methods result in more efficient, cost-effective results.

 

Krueper, D., J, Bart, and T. D. Rich.
2003. Response of vegetation and breeding birds to the removal of cattle on the San Pedro River, Arizona. Conservation Biology 17:607-615.

In late 1987, cattle were removed from the San Pedro Riparian National Conservation Area (NCA) in southwestern Arizona. We monitored vegetation density and abundance of birds during the breeding season during 1986-1990 in riparian, mesquite grassland, and Chihuahuan desert-scrub communities in the NCA. The density of herbaceous vegetation increased four- to six-fold in riparian and mesquite grassland communities. Of 61 bird species for which sufficient data were collected, mean detections per kilometer increased for 42 species, 26 significantly, and decreased for 19 species, 8 significantly. The number of individuals of all avian species detected on surveys increased each year from 103/kilometer in 1986 to 221/kilometer in 1991, an average annual increase of 23% (p < 0.001). The largest increases occurred in riparian species, open-cup nesters, neotropical migrants, and insectivores. Species of Chihuahuan desert-scrub, in which vegetation changed the least, showed the smallest increases. Only a few of the species showed increasing regional trends for the same period, as demonstrated by the North American Breeding Bird Survey; thus, increases on the NCA were likely caused by the change in local conditions, not be regional effects. Our results suggest that removing cattle from riparian areas in the southwestern US can have profound benefits for breeding birds.