Mark S. Ashton

Morris K. Jesup Professor of Silviculture and Forest Ecology and Director of School Forests

Research Overview

Understanding the regeneration dynamic as a basis for restoration and sustainable management of forests:

I foresee that upland forests in humid regions of the world, after two centuries of dramatic decline and degradation, will become critical resources for the sustenance of global services (water, climate amelioration, recreation) and products (genetic reservoirs of new products, specialty timber and nontimber products) demanded by society. My research concentrates on the ecological adaptations by which trees of various species of these complex forest types become established naturally after disturbances that make vacancies in the growing space. The kind of knowledge gained is a key part of the basis for developing silviculture that will sustain and augment the various forest values of the future.

The importance of big scale comparisons:

The regeneration period is a critical window of time during which the future composition and development of the forest is largely determined. It is also the period during which the silviculturist has the most opportunity to restore and guide forest growth. My research has focused on understanding the most important biological and physical processes governing regeneration of species-rich moist forests. The majority of my research has been centered for over twenty years at field sites in two primary upland forest regions: 1) the American temperate moist deciduous forests (oak-hickory) of southern New England, USA; and the Asian tropical wet-evergreen forest (mixed-dipterocarp) in Sri Lanka and Malaysia. For the last ten years I have also been working at three secondary field sites 1): the boreal spruce-aspen forests of Saskatchewan, Canada; 2) the moist mixed-conifer forests of interior British Columbia; and 3) the tropical seasonally-wet forests of Panama, Central America. Sites were selected to develop common methodological protocols that would enable a better understanding of the differences and similarities of regeneration within and across major forest biomes.

Long-term experimental rationale and framework: Building the basics:

Cladistic groups (at the genus level in particular) are largely the level at which species differentiation occurs in tree species-rich forests such as those of eastern North America and the Asian moist tropics. Co-occurring species within a genus may differ in value and the products that they yield, as well as in their spatial and temporal role in biodiverse plant assemblages. I have chosen to study a series of co-occurring species that are of the same cladistic group (and often of the same successional status), because their similar morphology and growth adaptations facilitate examination of differences. Identifying these differences and their variations can provide a better understanding of evolving species specialization in relation to environment. This, in turn, provides the ecological information necessary for restoration and sustainable management of moist tree species-rich forests.

Applying this knowledge to silviculture:

My work has immediate application for the development and testing of regeneration methods in natural forests, which I am pursuing at all my sites. I have long-term plots monitoring regeneration performance in experimental canopy openings that are intended to test hypotheses concerning forest resilience in relation to disturbance and site productivity. In the tropics I am using information gleaned from New England’s experience with deforestation, and together with my information on seedling regeneration ecology of the tropics (Panama, Sri Lanka), I have embarked on a series of sequential studies with collaborators on site reforestation. Much of this information has been summarized in two seminal textbooks on silviculture and agroforestry.