Big Prairie Broom Removal Plots: Reprise, Rationale, and Protocol

Update on Wednesday, July 28, 2011: posted new draft location map of the Big Prairie plots; Flickr collection is much nearer completion, and all plots are now represented.

Note on the above map: the plot markers are fixed and remain in place, but the locations as shown here are approximate. GPS is too imprecise for accurate mapping at this scale; the next step is old-style mapping with surveyor’s tape.

As the seasons have sped by I have made a number of posts regarding the startlingly beautiful bunchgrass prairies I first stumbled upon this spring, while mapping French broom occurrences in the southeastern highlands of Redwood. And I have made some mention of the systematic removal of broom thickets we have begun there, including the establishment of fixed, numbered plots of like dimension, tiered across the hillside.  But I have not yet really laid out the rationale for such an approach, so shall attempt to do so here.

(Note: this post is very much in media res and shall be evolving accordingly. Your comments, queries, and suggestions are very welcome!)

From my first moment of exploring the Big Prairie and its kindred, on April 14 of this year (see post of that date), it was manifest that these gems of the sky-country were not only robust, verdant, and beautifully bedecked with wildflowers, but also imperiled by a tsunami of broom which was roaring up the hillsides and smothering everything in its path.  Not mere florid prose, this; a close look at the USGS Seamless aerial photos from 2006 shows extensive areas of open grass mingled with coyote brush, where now there is no open grass at all.  Within a mere five years the broom has colonized and largely monoculturated an area easily several thousand square meters in dimension.

We began our first broom removal efforts in lower Big Prairie on April 21 (see post of that date!). To the best of our knowledge no one had ever made any such effort in that region before that day. (Way up the hill, in the area surrounding the knoll that adjoins the East Ridge Trail, one stalwart restoration volunteer had succeeded, over the course of two years of solitary effort, in pushing broom off a long stretch of that roadside and holding the line on its encroachment on the hilltop area;  but, if I recall the contours of our conversation correctly, he took one look at the broom thickets further down the prairie and saw immediately that it was too much for just one person to face.)

This first patch, Plot 1, is a relatively small outlier and nothing like the dense monoculture thickets of Plots 4 and up. It is paving the way for them, though, and is a good illustration of the restoration task here on the bunchgrass prairie.

From that first April workday these thickets, and the once and future prairie that underlies them, cried out to be mapped and documented, for they are perfect for illustrating the benefits — nay, the necessity — of removing broom from our imperiled native habitats, and perfect as well for adding to our understanding of how best to restore native grassland ecosystems that have been disturbed in this way.  The foundation of both of these goals is the documentation of vegetation change over time in fixed plots of known history, which to my knowledge has not heretofore been attempted in the exotics-removal context within Redwood Regional Park.

(There is much more to say on this, but this post remains in a fluid state and shall be continually updated for some time.)

The following diagram illustrates the photographic protocol I began to use starting with plots 4, 5, and 6, and the Flickr link which follows contains the photographic record of the plots I have uploaded to date. (There are more views to upload but all eleven current broom removal plots are now represented as of Wednesday, July 28, 2011.)

I recommend hitting the “slideshow” button for each of the sets therein, as it saves the trouble of having to click the forward button each and every time. And these are HD images that work best in full screen mode.

The entire collection of Big Prairie plot photos and videos is accessible via the above link, but Plot 10 here is probably a good example of how this plays out in practice. I established this plot on the fly in the midst of our large and v.successful volunteer work day on Memorial Day morning, May 30, 2011.  Any clear patches within its bounds had been cleared that morning;  prior to this the broom cover had been complete. In these big thickets all you really see, of course, is broom, but from known vantages with permanent plot corners to anchor them in space and begin a timeline. And as prior posts have illustrated, once the people with weed wrenches show up things begin to evolve rather quickly!

More soon!

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