Woody Legume Community Structure

Apparently many former grasslands and savannas have changed because of anthropogenic disturbances caused by the introduction of numerous domestic grazing animals (cattle and other species), the reduction of light, fluffy fuel (grasses by herbivory), and a concomitant reduction of fire frequency (Van Auken 2000, 2009). In southwestern North America, these changes have led to encroachment of various woody species including species of Prosopis, Senegalia, and Vachellia (the latter two previously acacias). The conditions required for the establishment (encroachment), growth, and dominance of the woody plants in many of these former grasslands have been difficult to understand. Global change phenomena including increased levels of atmospheric CO2 and concomitant elevated temperature do not seem to be the main cause of the encroachment, which appears to be a management problem or phenomena (Van Auken 2000, 2009).