1. Theories of Vegetation Change Mort Kothmann Texas A&M University

2. Managing Plant Succession August 2003 October 2007 Fire + HerbivoryVegetation change

3. Plant Succession Plant succession is a result of the competitive interactions of plant species and populations. Its effects are predictable. It happens everywhere, not just on rangelands. Understanding plant succession is a key concept to designing effective grazing management.

4. Rangeland Condition Composition of plant community at a specified site relative to potential benchmark community (climax or a desired plant community) that could occur on that site Composition of plant community at a specified site relative to potential benchmark community (climax or a desired plant community) that could occur on that site

5. Ecological Site Distinctive kind of land with physical characteristics (climate, soils and topography) which differ from other sites giving rise to significantly different potential for the kinds and amount of vegetation it can produce. Distinctive kind of land with physical characteristics (climate, soils and topography) which differ from other sites giving rise to significantly different potential for the kinds and amount of vegetation it can produce. (Note: this is essentially the same definition as Range Site except that it uses ‘land’ not ‘rangeland’)

6. Ecological Site Descriptions Adaptation of “poly” climax theory Adaptation of “poly” climax theory Description of single plant community (edaphic climax) Description of single plant community (edaphic climax) Geared towards grazing interpretations Geared towards grazing interpretations Described at plant community scale and correlated to soil map units Described at plant community scale and correlated to soil map units

7. Names of Ecological (Range) Sites Based on permanent physical features: Based on permanent physical features: Soil type Soil type Topography Topography Help users remember significant rangeland in their locality Help users remember significant rangeland in their locality Clay Upland, Saline, Limestone Breaks, Claypan Savanna, Loamy Bottomland Clay Upland, Saline, Limestone Breaks, Claypan Savanna, Loamy Bottomland

8. Time Fire Frequency Grazing Pressure Probability & rate of woody plant establishment A B C Herbaceous retrogression Perennial grasses Woody plants Community Composition Time or cultural energy increments Required to drive system to new configuration Shrub driven succession Graminoid-driven succession A= Tall / mid-grasses B= Mid / short grasses C= Short grass / annuals = Transition threshold high low high low high Archer

9. Juniper Replacing Grassland Note multiple age classes of juniper and weak stand of grasses

10. Prescribed Burning

11. Fire

12. Drought – Sept 1999

13. Shrub dominated rangeland in transition towards grassland after a reclamation prescribed burn

14. Grasses Replacing Juniper following Fire Sideoats gramma

15. Seasonal Vegetation Dynamics (Aspect) The following series of slides are photographs of the same site made at 4-week intervals from early March until mid December. Note that the dominant species change as the seasons progress. In years with different weather patterns, vegetation dynamics would differ.

16. Rolling Plains – Early March

17. Rolling Plains – Late March

18. Rolling Plains – Late April

19. Rolling Plains – Late May

20. Rolling Plains – Late June

21. Rolling Plains – Late July

22. Rolling Plains – Late August

23. Rolling Plains – Late September

24. Rolling Plains – Mid October

25. Rolling Plains – Mid December