Nitrogen addition, not initial phylogenetic diversity, increases litter decomposition by fungal communities

• Main Authors: Anthony Stuart Amend, Kristin Leigh Matulich, Jennifer B.H. Martiny
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2015-02-01
• Series: Frontiers in Microbiology
• Subjects: Climate Change; Fungi; phylogenetic diversity; ecosystem function; nitrogen fertilization; Leaf litter decomposition
• Online Access: http://journal.frontiersin.org/Journal/10.3389/fmicb.2015.00109/full

Fungi play a critical role in the degradation of organic matter. Because different combinations of fungi result in different rates of decomposition, determining how climate change will affect microbial composition and function is fundamental to predicting future environments. Fungal response to global change is patterned by genetic relatedness, resulting in communities with comparatively low phylogenetic diversity. This may have important implications for the functional capacity of disturbed communities if lineages sensitive to disturbance also contain unique traits important for litter decomposition. Here we tested the relationship between phylogenetic diversity and decomposition rates. Leaf litter fungi were isolated from the field and deployed in microcosms as mock communities along a gradient of initial phylogenetic diversity, while species richness was held constant. Replicate communities were subject to nitrogen fertilization comparable to anthropogenic deposition levels. Carbon mineralization rates were measured over the course of sixty-six days. We found that nitrogen fertilization increased cumulative respiration by 24.8%, and that differences in respiration between fertilized and ambient communities diminished over the course of the experiment. Initial phylogenetic diversity failed to predict respiration rates or their change in response to nitrogen fertilization, and there was no correlation between community similarity and respiration rates. Last, we detected no phylogenetic signal in the contributions of individual isolates to respiration rates. Our results suggest that the degree to which phylogenetic diversity predicts ecosystem function will depend on environmental context.