Ecophysiology of Woody Plants
Trees, being long-lived organisms, respond to changing environmental conditions over a period from years, to decades and even centuries. One of the most ubiquitous environmental factors influencing tree growth and crown form is wind. Wind stress alters tree growth, usually by reducing the rate of height growth and increasing radial growth in what is known as the thigmomorphogenetic response. The influence of wind and other mechanical stresses on tree growth and development has been the focus of my research since 1977. Currently, we are studying the effect of mechanical stress on the development of biomechanical properties of the wood of hybrid poplar (Populus deltoides x P. trichocarpa). We have also collaborated with Dr. Frank Ewers to investigate possible trade-offs between mechanical strength and water conductivity in the wood of these hybrid poplars. This research has been supported by grants from the USDA NRI program. I continue to work on questions related to tree growth and development in response to wind and other mechanical loading stresses.
This research is also being applied to tree nurseries and urban forestry. The strongest implications being increasing resilance to storm-induce damage in the urban and ex-urban forest.
From 1983 to 1990, I worked at the Laboratory of Tree-Ring Research at the University of Arizona. During those years, I became acquainted with the powerful tool dendrochronology provides to study cambial development and tree response to the environment. We are currently applying dendrochronology to study the rate of growth and response of both native and non-native trees growing in Michigan.
During my years in Tucson, I began to study a population of ponderosa pines on in the Santa Catalina Mountains north of the city. I was fascinated by the existence of two needle types which co-existed in the mountains. A three needle type, classified as Pinus ponderosa var. scopulorum grew at the highest elevations and a five needle type, Pinus ponderosa var. arizonica, grows at lower elevations. Where the two types come in contact (sympatric), trees with multiple needle numbers exist, suggesting the presence of a hybrid. This research was the focus of two KUAT-PBS episodes of 'The Desert Speaks' in 1996: #708 - Santa Catalina Mountains and #711 - Four Research Stories. In 1997, I began a collaborative study with Dr. Bryan Epperson, Department of Forestry, Michigan State University to investigate the population biology of these trees. Current research includes conducting a dendrochronological analysis to document stand age and structure of the contact zone between the three needle and five needle populations and a genetic analysis of the trees in the contact zone. This study is currently funded by the USDA Forest Service.
Professor Beal's Seed Viability Study
In the autumn of 1879, Professor William James Beal began what would become the longest continuously operating experiment in the world. The study was conducted with the intent to determine the length of time the seeds of some of our most common plants would remain dormant in the soil, yet germinate when exposed to favorable conditions. Professor Beal selected lots of fifty freshly grown seeds from each of twenty-one different species (Agrostemma githago, Amaranthus retroflexus, Ambrosia artemisiifolia, Anthemis cotula, Brassica nigra, Bromus secalinus, Capsella bursa-pastoris, Erechtites hieracifolia, Euphorbia maculata, Lepidum virginicum, Malva rotundifolia, Oenothera biennis, Plantago major, Polygonum hydropiper, Portulaca oleracea, Rumex crispus, Setaria glauca, Stellaria media, Trifolium repens, Verbascum thapsus, Thuja occidentalis). A total of twenty lots were prepared by mixing the seeds in moderately moist sand and placed in pint bottles. The bottles were buried on the Michigan State University campus, uncorked and placed with the mouth slanting downwards to prevent accumulation of water in the bottles.
During the first 40 years of the experiment, germination tests were performed every five years. Originally the bottles were unearthed in the autumn, but in 1919, an early winter caused the soil to freeze solid and no bottle could be extracted until the spring of 1920 (the 40th year of the study). Dr. Darlington, who took over the experiment from Professor Beal in 1915 decided to extend the duration of the experiment by increasing the period between germination tests to ten years in 1920. This frequency was observed until the 100 year of the study in 1980. It was then when Dr. Bandursky, who took over the experiment from Dr. Darlington after his retirement, decided to extend the period to twenty years. The 15th bottle was unearthed in April 2000 by Drs. Frank W. Telewski and Jan Zeevaart, 120 years after the bottles were first buried by Professor Beal. This research was featured in the MSU News Bulletin and the journal Science.
The flower of the mullein was adopted for the new garden logo during the 125th anniversary of the W. J. Beal Botanical Garden, representing the longevity of the garden and Professor Beal's contributions to botany.