It is thought that the scouring reduces competition from native and non-native plants that would otherwise crowd it from the limited substrate or reduce its access to sunlight.
(native and non-native plants; would otherwise crowd; it; from the limited substrate) (native and non-native plants; reduce; its access to sunlight)
native and non-native plants native and non-native plants
would otherwise crowd reduce
it from the limited substrate
its access to sunlight