Understory Plants as Site Indicators

Foresters increasingly use associations of understory plants to indicate site quality for particular tree species. Some understory plants grow on a wide range of sites, but those with more specific site requirements (for example, in moisture and nutrients) are used for site classification. Understory plants tend to persist on sites regardless of past timber management, and the presence of a particular combination of understory species can indicate how well particular tree species will grow, even if those tree species are not currently found on a site. For example, if a combination of understory plants in north-central Wisconsin indicates a very dry to dry, nutrient poor site, a forester knows that site is best suited for growing jack pine, red pine, white pine, oaks, and red maple. Tree growth may not be particularly good on this poor site, but these tree species are the best adapted to it. Site type classifications have been developed for the Lake States, but their descriptions are beyond the scope of this book.