Growth and physiological responses of deciduous tree seedlings to three years of increased temperature and precipitation treatments

Background/Question/Methods

Predicted changes in global climate have been coupled with the prediction of northward migration of forest species, potentially altering the community structure and carbon budgets of mid-latitudinal forests.  Morphological and physiological responses of seedlings to altered temperature and precipitation may be moderated by acclimation, reducing the drive to migrate northward.   An increased understanding of plant acclimation and phenotypic plasticity is critical for developing scientific models of ecological responses to global change, because trees may acclimate to a new climate before migration becomes a necessity.  Studying the development of forest growth at the seedling level provides the opportunity to use whole ecosystem climate manipulation to test predictions of forest response to climate change and build a better understanding of how acclimation and adaptation affect the ability of species to succeed under future climate conditions.

Research question: My objective was to measure tree seedling morphology and physiology to determine if a species’ ability to acclimate to increased temperature and moisture could lead to changes in seedling growth responses and potential competitive abilities a recently disturbed stand within northeastern forests

The Forest Response to Climate Change (FoRCE) experiment was established in Central Pennsylvania in 2007.  Climate manipulations were imposed in a 2-factor design of increased temperature (~2°C) and precipitation (~20%).  Sixteen 2X2m plots were established in a recently harvested forest site and assigned one of four treatments: ambient, warmed, irrigated, and warmed+irrigated.  Seeds from 11 decidous tree species were planted in each plot and monitored for morphological and physiological responses to the imposed treatments over 3 years.

Results/Conclusions

Significant observable changes in growth and photosynthesis have occurred for most species as a result of the imposed climate manipulation treatments.  Based on our results, the imposed climate treatments are affecting the morphology and physiology of young seedlings.  Warming has advanced the timing of germination and leaf out in seedlings and has increased overall above ground growth for a subset of the 11 study species.  Photosynthetic responses, pre-day and mid-day water potential also showed species specific responses to warming and increased precipitation over the three years of study.