Grass Management with Fire and Disc

Finally, on the weekend of October 8, Placedo, TX received upwards of 3 inches of rain.  This was dearly needed by the cattle ranchers and the vegetation, close to reaching its last gasp.  The rain also lifted the burn ban, at least temporarily, and got me thinking about prescribed burning.

Last winter, I believe we waited too long to burn and on that particular day the humidity was too high, inhibiting the brush from carrying a consistent flame.  That was early March, and I hope that this year we are able to set a torch in January/February.

Fire is an excellent tool for range management, for it promotes native cool season grasses (which prefer such fires) and keeps woody vegetation in check.  In our particular case, we are interested in spurring lush grasses for cattle, while thinning unwanted woody plants in certain areas.  We have burned these fields during the past 15 years to mostly control  McCartney Rose (Rose Hedge), leaving the fields to grow back after the fire was out.  This simplistic method is effective for up to 2 years, but beyond that the Rose Hedge will begin for grow back with a vengeance, often out-competing the desired grasses.

Through the practice of planting food plots for deer management, I think we have unintentionally discovered a new tool to fight against the Rose Hedge.  In the areas where we have disced soil bed in preparation for such food plots, five years later these fields are nearly void of any Rose Hedge.  This observation leads me to the idea of discing a field after burning the vegetation.  The disc aerates the soil, stimulating new forb and grass growth, which in turn will benefit wildlife and cattle.  I believe that this disturbance of the soil and exposure up of the rose hedge roots causes the plant to die and prevents rapid regrowth.

Currently, we have a 100 acre section that is prepped for burning, and I hope that we are able to experiment with this new idea on a larger scale.  In order for this practice to be beneficial to both wildlife and cattle, I believe that burning should occur every 3-4 years and, if effective, be followed by discing every 9-12 years.

Woodlands Research Progress

I have been slacking with my posts, but to my credit I dont think that I am a natural born blogger.

Last week, although my birthday, was a very productive week at work.  I have been developing a distributed hydrologic model called Vflo for the Woodlands, TX watershed.  Initially I used GIS Spatial Analyst to interpret the elevation, slope, soils, and land use types for the 35 square mile watershed, which was input into 200 ft by 200 ft grid cells in Vflo.  These inputs are used to determine hydrologic parameters, such as hydraulic conductivity for each grid cell, which are used by Vflo to determine infiltration and runoff within the cell.  Runoff is then routed through the land cells and into established channel cells.

The first model I created for the Woodlands reflects Manning’s roughness values and percent impervious cover according to 2006 development data.  This model is used to represent The Woodlands as it exists today, with its excellent stormwater management design, and to compare it to the Woodlands watershed if it had been developed as a typical Houston suburban community.

Next I created new Vflo model, assuming the entire watershed was mixed forest and had zero percent impervious surfaces to represent the Woodlands before development took place.  I used raingage rainfall data and observed streamflow data for five storm events  during 1974 to represent how the Woodlands watershed responded to storm events in its undeveloped state.  The undeveloped model was calibrated to the historical storm events of, best matching the observed hydrographs.

Once my undeveloped model was calibrated to the historical storms, I was able to run these storms through the 2006 development model and directly compare the hydrographs between the two models.  As expected, the peak flows in the 2006 development model  increased and the time to peak decreased as less infiltration is allowed and more water is conveyed down the improved channels.

The next step is to develop a ‘High Intensity Woodlands” model to see how the watershed would respond to rain events if stormwater management was not a priority for the designers and engineers.  I expect that the peak flow from this model will be much greater than the 2006 development model.