Thursday, June 5, 2014

Delineating Invasive Plant Beds the Easy Way

Effective management of invasive aquatic plants requires some fundamental but previously difficult prerequisites.  First, you have to find the infestations; not easy when you can't see underwater.  Second, you have to create boundaries of the infestation; also not easy when you can't see underwater or when the plant does not behave and form perfect surface-growing patches that you can trace with your GPS.  So it used to be a game of darts using whatever tools available (e.g. rakes, manual interpretation of GPS and sonar, aquascopes, snorkeling, scribbling on paper maps) to crudely estimate the extent of invasive plant growth.  Needless to say, delineations using this technique have been crude leading to equally crude and often ineffective management.

We demonstrated one example of the differences between manual delineations of the invasive curly-leaf pondweed and more precise delineations using Lowrance HDS and BioBase automated processing.  The results are telling!

Thrid party manual delineation of the early growth stages of the invasive aquatic plant curly-leaf pondweed Potamogeton crispus (with other minor species mixed in) in a Minnesota Lake.  Delineated boundaries were presumably a result of manual interpretation of sonar and GPS.

Actual extent of vegetation growth using Lowrance and processed/mapped with BioBase to verify third party manual delineations.  Heat of colors represents percent of the water column occupied with vegetation (Biovolume).  Red represents vegetation that is close to the surface, green represents vegetation that is low-growing.  Red lines represent the boat path and source of data in the heat map.
Delineation of vegetation beds using the polygon tool in BioBase.  Estimates of the bed were conservative since care was taken to not include delineations outside of the track (extrapolation) because no data were available for growth very close to shore.  If these data were available and added to the map (manual veg coordinate feature). delineations would've been even more precise.
Shocking difference between manually delineated invasive plant beds and through the more repeatable and objective aid of BioBase.  The difference carries potentially large consequences on water volumes, herbicide volume and prescriptions, and efficacy.

Given all the economic, environmental, political, and public-relation risks of imprecise invasive aquatic plant management, can the interests of the public trust afford shotgun approaches?  Many of our BioBase users like Restorative Lake Sciences don't think so and can tell you about their experiences.  Share with us how BioBase is helping you make more informed and precise lake management decisions!