Abstracts |
Mycorrhizal symbioses are essential components of terrestrial ecosystems. These symbioses are intimate associations between plants and fungi where the plant fixes C, exchanging it for nutrients and water from fungal hyphae that permeate and explore surrounding soil. Perturbations, whether acute (such as disturbance or cutting) or chronic (global change, N deposition) alter mycorrhizal functioning and thereby forest dynamics. Among these dynamics are C sequestration and alleviating nutrient stresses to optimize C:nutrient ratios. We explore three areas whereby global change might alter mycorrhizae, which in turn, will affect forest dynamics. First, increasing temperatures associated with elevated atmospheric CO2 will increase soil temperature, thereby potentially increasing respiration. However, that may depend upon lags and the variation inherent in diel and seasonal variation. Second, the increased temperature will increase soil drying, and subsequently reduce the length of the growing season for mycorrhizal fungal hyphae. However, elevated CO2 will simultaneously increase water-use efficiency, thereby increasing the length of the growing season. Third, mycorrhizae increase activity and nutrient uptake with elevated CO2, negating some of the C:nutrient stress. This activity is dictated by both changing amounts of mycorrhizal hyphal growth and by shifting mycorrhizal fungal taxa, altering the strategies whereby nutrients are acquired and C allocated. This includes spatial (breadth and depth) as well as enzymatic shifts. Finally, we examine the longer-term implications of how global change can alter plant communities and plant dynamics on both ecological and evolutionary time scales. |