Agroforestry and Tree Crops

We think of forests as sources of fiber, and fields as sources of food.  We have the term agriculture which means the culture of fields.  And we have the term silviculture which means the culture of forests.  Since the development of scientific agriculture, there has been little overlap between agriculture and silviculture.  Nevertheless, going back further in time, particularly in pre-industrial cultures, forests were important sources of food.  Indigenous cultures all around the world still harvest much of their food from the forests.

A part of Green Hill Park in Worcester, MA which has been periodically burned by local youth, thereby approximating Native American agroforestry practices.

In the past 20 years, there has been increasing academic and practical interest in a new interdisciplinary field called agroforestry.  Agroforestry incorporates elements of forestry, agriculture and horticulture.  Traditional, indigenous agroforestry systems have been studied and improved in some cases.  This is particulary the case with tropical agroforestry systems.  Temperate agroforestry systems have also been studied and improved. 

One traditional practice in the Northeast that can be included under the agroforestry rubric is maple sugaring, since it produces a food product (maple products) and a fiber product (timber).  It was first developed by Native Americans and expanded by Anglo-Europeans.  It's still a relatively important industry in some parts of the Northeast. 

A large, dead standing American chestnut.  The large limb holes indicate that this tree was growing in an open pasture situation before in succumbed to the blight.

Before the demise of American chestnut forests , they were an important source of food for humans, as well as livestock that would be turned into the chestnut and oak woodlots in the fall.  This practice was commonly known as "shacking the hogs" since someone would go live in a shack where the hogs were being fattened on the chestnuts and acorns.  Of course many species of wildlife also benefited from the chestnut crops.

Around the turn of century, a new industry was emerging in Pennsylvania and New Jersey based on European chestnuts grafted to American chestnut root systems in cutover woodlots.  The grafted trees would grow rapidly and produce nuts at an early age.  Then the blight came along in the 1920s and destroyed the industry.

Black walnuts interplanted with balsam fir Christmas trees in Michigan.

Today, black walnut plantations are increasingly common in the Midwest.  Many of these are integrated with field crops such as wheat and corn.  These systems produce high quality veneer logs, nuts and annual crops.  Other agroforestry systems are being developed for riparian areas to reduce soil loss from agricultural fields, and thereby maintain water quality.  Windbreak designs are also being improved.

The Northern Nut Growers Association has been working for nearly 100 years to improve the commercial qualities of native nut trees including shagbark hickory, black walnut and butternut.  They've also been working with introduced species such as Chinese chestnut, Persian/Carpathian walnut, European hazel, plus hybrid Chinese-American chestnuts and European-American hazels.  Pecan is the only native North American nut to have achieved commercial success.

The American Chestnut Foundation and the American Chestnut Cooperators Foundation are working hard at restoring the American chesnut.  The former is doin this work by backcrosing American chestnuts with Chinese chestnuts to achieve a hybrid that is all American except for the Chinese genes which confer resistance to the blight.  The latter is doing their work by finding and propagating surviving American chestnuts that appear to have developed blight resistance on their own.

If you've ever tasted shagbark hickory nuts, you'll appreciate the potential of this native nut.  However, the long breeding cycles needed to develop the thin shells and large kernel size necessary for commercial success are a real obstacle.  Some NNGA members have done considerable work in this direction.  The black walnut likewise has been the subject of considerable breeding.  But the strong flavor makes them suitable mainly for cooking.  Korean pine is a popular and high-priced nut that can be successfully grown in our climate.