Effects of shrub removal practices in livestock systems of the Arid Chaco, Argentina
DOI:
https://doi.org/10.25260/EA.26.36.3.0.2707Keywords:
woodland, livestock production, roller-chopping, hand-cutting, woody plantsAbstract
1. The increasing abundance of native shrubs (shrub encroachment), driven by factors such as intensive logging and overgrazing, affects forests and grasslands. In the Arid Chaco, this process reduces forage availability, leading to the use of shrub-removal practices and the sowing of exotic grasses to compensate for this reduction. However, little is known about the effects of these practices on vegetation structure and the relationship between grasses and woody plants.
2. We evaluated the effects of roller-chopping and hand-cutting on tree, shrub and grass cover, the population structure of woody plants, and the relationship between woody plant density and grass cover. We considered four land-cover types: reference forest, degraded shrubland, roller-chopping areas and hand-cutting areas. The latter two were sown with Cenchrus ciliaris L. (buffel grass).
3. Roller-chopping and hand-cutting areas showed lower tree cover than the reference forest and differed from each other in shrub and grass cover. Hand-cutting areas showed lower shrub cover and higher grass cover, whereas roller-chopped areas showed intermediate grass cover and shrub cover similar to that of the reference forest and degraded shrubland. The reference forest had a higher density of tree seedlings and, together with the degraded shrubland, a higher density of adult trees. Among shrubs, adult density was lower under hand-cutting.
4. Grass cover decreased with increasing woody plant density, which explained 61% of its variation. The segmented model identified a breakpoint at 1527±314 woody individuals/ha, with a steeper decline below this value. The relationship was stronger with adult shrub density (R²=0.59) than with tree density (R²=0.30). 5. Implications. Hand-cutting favours grasses but simplifies woody vegetation, whereas roller-chopping allows greater coexistence between the woody and herbaceous layers, although without promoting the recovery of the tree component.
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