Have you ever taken a walk through a forest in the Midwest? Have you ever wondered what determines which species of trees are found where, within a given forest? The temperate forests of Eastern North America (ENA) comprise the second largest temperate forested region on Earth. Historically, regional species richness, composition and associations of tree species within ENA have largely been attributed to climatic and edaphic (soil) conditions. However, the rate and types of disturbance that have occurred within ENA forests post Euro-American settlement are increasingly being taken into account along with climatic and edaphic conditions in modeling the relative abundance of species within their respective ranges.
Determining what conditions lead to regional biodiversity and relative abundance of tree species is made all the more difficult by the propensity of species to have sporadic, disjunct, yet widespread distributions (Kentucky coffeetree, burr oak). Individual tree species may be present in a wide range of habitat conditions and specific niches that vary from region to region. For instance, the Kentucky coffeetree is found primarily in two confounding niches: dry, rocky bluff tops along major waterways and on the terraces of rivers and streams within bottomlands. These species highlight that while climatic factors are certainly a determinant of tree species richness, the biological traits and unpredictable distribution patterns of species show that other important mechanisms are likely at play.
Indigenous peoples of Eastern North America
Indigenous peoples have been present within the forests of ENA for at least 14,000 years. Indigenous cultures were horticulturist societies that practiced intensive agriculture and forest management within major river valleys of the temperate forest region, leading to the development of the Eastern Agricultural Complex, one of 10 independent centers of plant domestication on Earth. Cultures such as the Hopewell and Mississippians constructed massive earthworks including burial, ceremonial and effigy mounds, agricultural canals and reservoirs, lunar observatories and roads linking ceremonial centers. Long distance trade networks facilitated trade of goods such as ceramics and metal as well as crops. Indigenous forests management and silvicultural practices as opposed to solely foraging likely developed during the archaic period (4500 + years ago). Regular prescribed burning and human mediated dispersal occurring for thousands of years prior to the origin of the Eastern Agricultural Complex could’ve had hugely impactful effects on the ranges of many species. The value of wood products (dyes, foodstuffs, medicine, rot resistant timber,) would have incentivized Indigenous peoples to cultivate, disperse and exchange beneficial tree species. Any assumptions made about a species relative abundance or distribution, must take into account Indigenous management practices and ethnobotany.
Scope of Study
This study examines the collective impact of 10,000+ years of Indigenous inhabitation and land management practices, on the distribution and relative abundance of tree species within the Eastern Temperate Forest Ecoregion. Indigenous management activities both favored and disfavored tree species depending on a species’ ecological characteristics such as fire tolerance, shade tolerance and primary dispersal methods. While extensive studies have found that Indigenous forest management alters the species composition of forests by promoting fire intolerant, mast producing species such as oak and hickory, few studies have holistically evaluated how Indigenous forest management and silvicultural practices would have impacted the relative abundance and distribution of tree species based on their ecological characteristics and their relative value to Indigenous peoples. A variety of data sources including archeological data, herbarium records, historical accounts, pollen records and witness tree data were used to reevaluate and reinterpret the distribution, relative abundance and specific niches of tree species whose range wide distributions show strong evidence of influence by Indigenous management activities.
Findings and Conclusions
Results of the study indicate that the Indigenous peoples of ENA favored and disfavored species of trees depending on the ecological characteristics and relative value of a species to Indigenous peoples. The ranges of fire intolerant and relatively less useful species such as Eastern hemlock have likely been reduced in the lower Midwest due to historic prescribed burning regimes. The increased abundance of valuable species like the burr oak (which produces the largest acorn of any oak species in North America) and Northern Catalpa (which produces extremely rot resistant timber) within bottomlands and adjacent to major rivers is likely a product of Indigenous settlement patterns. Areas within ENA where Indigenous populations were highest will likely show the greatest evidence of their forest compositions being influenced by Indigenous peoples. Ignoring the possible impacts of Indigenous peoples on the modern biogeography of species prevents the development of a holistic and accurate assessment of a species’ relative abundance and distribution. In short, it’s very difficult if not impossible to explain the current and historic relative abundance and distribution of tree species without taking into account the history of Indigenous peoples within Eastern North America.
Ethan Iversen is a senior at the O’Neill School of Public and Environmental Affairs.
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