Mark S. Ashton

Mark Ashton

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

Email: .(JavaScript must be enabled to view this email address)
Office: Room 22, 360 Prospect Street, New Haven, CT
Phone: 203.432.9835

Education

B.S. University of Maine, College of Forest Resources
M.F. Yale University
Ph.D. Yale University

F&ES Faculty Profile

CV [pdf]

Publications

Research Interests

My research focuses on the regeneration of forests. Areas of interest concerning forest regeneration include seedling physiological ecology in relation to light and soil water availability, forest microclimates and disturbance dynamics, soil seed banks, fire ecology and regeneration, regeneration guilds in relation to disturbance, silvicultural regeneration methods - particularly shelterwood systems - for non-timber and timber crops, restoration of complex forests, and the creation of mixed plantation analogs to natural forests.

I believe 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 non-timber 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 from this research 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 landscape-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 (Yale Myers, Connecticut); and 2) 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 in order 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 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.

Collaboration

At all my research sites I have become part of a network of colleagues and interdisciplinary teams.  I have a longstanding commitment to advising and nurturing young local scientists and practitioners.  I have received several international prizes for my research, advising and teaching. My doctoral students have all followed similar themes and experimental protocols to my own for understanding regeneration dynamics of different forest types, including complex moist forests and simpler semi-arid forests.  Their studies are based in important forest regions around the world, including the Indian Himalayas, the mangrove deltas of Papua New Guinea, the rain forests of Central Africa and the Peruvian Amazon, and the forest-steppe of Mongolia.  Lastly, teaching advanced-level graduate courses has provided me the opportunity to work with students and faculty on complex biological and social issues of forest use and protection.  To date we have studied the Panama Canal watershed, the Venezuelan high Andes, community development in La Amistad Biosphere Reserve, Costa Rica, community forest management in Oaxaca, and watershed management issues of the Ecuadorian Andes.