Authors: Stinner, D.H., Stinner, B.R., Martsolf, E.
Year: 1997
Journal: Agriculture Ecosystems and Environment
This article includes three HRM case studies, all of which have interesting and vital information. The first is an ongoing ranch management study conducted by the Noble Foundation on their demonstration ranch in Marietta, Oklahoma.
The future landscape description within the ranch’s holisticgoal “was to reverse the successional trend back to a mixture of low, medium, and high seral species occupying as much as 50% of the plant communities…”. The data presented provide a solid example of using management to modify the landscape in accord with the holisticgoal.
The figure below clearly illustrates a shift in the successional species composition within the areas monitored. In 1987, the management team implemented grazing planning (controlled recovery periods, stock density management, and timing control), fire, and animal impact.
In the figure above, we first notice a sharp-drop in low-seral species by 1991, which was accompanied by a modest increase in stocking rate. This is followed by a notable increase in high-seral species in 1994, which was accompanied by a significant increase in stocking rate. Simultaneously, deer populations increased by 100%.
This case study does not paint a full picture of what is causing the changes in successional species composition. No data is offered on specific plant physiological responses, but it is highly likely that controlled recovery periods and the prevention of plant overgrazing allowed higher seral species to recover and compete more vigorously with the “weedy” annuals described as low-seral. As perennial grasses have more well-developed root systems than annuals, repeated defoliation without recovery can stunt growth and deplete root biomass, resulting in severe moisture stress in brittle environments. The recovery of high-seral species increased forage availabiilty, thus allowing for an 80% cumulative increase in stocking rate. Such a cause-effect analysis is speculative. More data is required, especially in regards to animal performance as stocking rates increased.
In fairness, the case study article is brief and probably does not include all of the available data. In addition, many years have past since this article was written, during which time the Noble Foundation has continued its management/research program. Further follow-up is required to update the details of their work.