Correspondence of stem growth increments to weather and reproductive behavior in Dirca palustris, an understory shrub

Growth increments in long lived woody plants have proven to be valuable records of historical climate patterns, changes in canopy characteristics, and physiological processes operating at the individual level.  Measurements of branch growth increments in Dirca palustris (eastern leatherwood), a long lived shade tolerant understory shrub were used to evaluate the effects of weather patterns, canopy harvest, and tradeoffs between reproduction and vegetative growth.  Branch growth increments dating back 5-20 years were measured on 50 mature leatherwood individuals in five Acer saccharum dominated sites in the Ottawa NF, Michigan Upper Peninsula.  As expected, growth in three sites showed increases in response to selective logging.  In a mature old growth and a second growth stand, growth reductions were visible between 1994-2000.  These are related to an initial period of unusually low spring temperatures followed by a period of unusually high spring temperatures.  Within shrubs, the patterns of growth on separate dominant branches were weakly correlated.  Flower and fruit production in a given year are weakly, but positively related to branch growth in that year.  Flower and fruit production are more strongly and positively related to vegetative growth in the previous year, suggesting that carbon balance is an important limitation on reproduction.