The effectiveness of local and exotic vegetative buffers at reducing runoff generationand sediment production in the United States Virgin Islands PDF Download

Author: Race Stryker
Publisher:
ISBN:
Category : Buffer zones (Ecosystem management)
Languages : en
Pages : 0

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Book Description
Terrigenous sediment is a primary non-point source pollutant in the United States Virgin Islands(USVI), and is a persistent problem throughout the Caribbean. Large amounts of suspendedsediment produced by heavy rainfall can degrade seagrass beds and coral reefs, which provideecosystems services supporting fisheries and tourism of the USVI. As the impacts of climate andland use change increase, the events that cause large amounts of runoff could increase in frequencyand severity. On small islands in the Caribbean, it can take a long time for topsoil to accumulate.Even small losses of topsoil due to runoff can reduce the limited arable land which can have adisproportionate effect on agriculture and local food security.Nonpoint source pollutants present a unique challenge for land managers because they need to becontrolled across a large geographic area. One well established method for controlling runoff andsediment transport is the use of vegetated buffer zones. Vegetation can be used to directly coversoil that would otherwise erode, or it can be placed between eroding areas and waterways toreduce and filter runoff. Existing literature indicates that stem density is inversely correlated withrunoff velocity and the erosive energy of flowing water. The USVI currently does not have anywidespread erosion reduction policies or efforts to make use of buffer strips. This studyincorporated diverse ways of knowing into the design of the buffer strips and tested plantsrecommended by the community against erosion control plants conventionally used in islandecosystems to find a reef-safe landscape solution that is an effective buffer and culturally relevantsolution.We utilized runoff flumes in a randomized complete block design (RCBD) to test the effectiveness ofnative and exotic buffer vegetation in terms of their ability to slow oncoming sheet flow and reducethe concentration of sediment in the resulting runoff. The experiment tested four different covertypes: bare soil (control), weedy fallow, snake plant (Dracaena trifasciata) which is ecologicallyinvasive but considered native by some, and vetiver grass (Chrysopogon zizanioides) which is exoticecologically and culturally. The weedy fallow was the most effective buffer strip and was found tosignificantly slow the rate of sheet flow passing through the buffer strip, and reduce theconcentration of sediment in the runoff by an order of magnitude when compared to bare soil (1.3±0.5 g L-1 in bare soil runoff and 0.14 ±0.07 g L-1 in weedy fallow runoff). Vetiver grass and snakeplant did not perform as well as weedy fallow, and in some cases were not significantly differentfrom bare soil. While these cover types may have benefitted from longer establishment times, thereare costs associated with planting vetiver grass and snake plant on a large scale that make themless desirable management solutions when compared to existing practices of letting areas recruitwill fallow vegetation. This study found that the cultural practice of letting certain areas “go tobush” or recruit with fallow vegetation, is an effective and no-cost form of reef-safe landscaping thatcan be implemented widely in the USVI.