Quantifying inadvertent invasive plant transport from powerline rights-of-way in New York State

Background/Question/Methods

Invasive exotic (IE) plant species have real costs to native biodiversity, ecosystem function, human health, and the economy. Personnel and equipment engaged in vegetation management may inadvertently transport propagules of IE plant species, and states are increasingly requiring that vegetation managers on powerline corridors take measures to reduce such spread. Our research goals are to (1) quantify the spread of invasive propagules during typical vegetation management operations and (2) make recommendations for cleaning protocols for vehicles and personnel.

In the summers of 2013 and 2014, we observed vegetation management crews 60 times at sites across New York State. Each time, we sampled vegetative material and soil accumulating on two vectors (one person and one vehicle) by selecting and pre-cleaning a portion of the vector, attaching an active GPS unit to record the distance traveled, and cleaning the same portion of the vector after a few hours of vegetation management activity. The sampled material was then germinated in a greenhouse and seedlings were identified. Counts of germinants in the greenhouse were scaled to whole-vector estimates (based on a field estimate of the proportion of total material on the vector that was represented by each sample).

Results/Conclusions

Samples collected in 2013 contained over 13,000 viable propagules (over 600 IE), and samples collected in 2014 contained over 11,000 viable propagules (over 2600 IE). In general, whole-vector estimates indicate that tracked mowing machines have the greatest capacity to move propagules (average per machine in 2013 was 5754; in 2014: 9966), followed by wheeled all-terrain vehicles (1863 in 2013; 1065 in 2014) and personnel (24 propagules per person in 2013, 27 in 2014). The most frequently transported IE species were purple loosestrife (Lythrum salicaria) and honeysuckle (Lonicera morrowii and L. × bella), which accounted for roughly 82% and 11% (respectively) of all IE species identified. Cleaning protocol recommendations will likely need to account for vector type, distance traveled, environmental conditions (e.g., weather, soil drainage, IE propagule pressure), and IE species life history.