Print PageArbuscular mycorrhizal associations are among the most widespread symbioses estimated to occur in over 80% of all plants. Although well studied in terrestrial habitats, they were long thought absent in wetland plants. Recent studies have shown many wetland plant species harbor arbuscular mycorrhizae (AM) fungi and dark septate endophytes (DSE). The factors that regulate AM and DSE colonization are poorly understood but this understanding is necessary to predict plant community response and ultimately ecosystem functioning to human induced stressors. To examine the effects of anthropogenic alterations on symbiotic associations in wetland plants, our study focused on the effects of water quality, hydrology, simulated hurricane exposure and sedimentation on AM and DSE colonization in coastal marsh plants. Identical plant communities of 12 marsh species were established in 144 - 200L mesocosms then treatments imposed. Treatments consisted of four levels of water quality (Control, fertilized, 3 and 6 parts per thousand salinity), three levels of water availability (flooded, flow-through and mesic), sediment application (+,-) and exposure to hurricane (+,-), yielding a total of 24 different treatment combinations. After five years, two replicate soil cores and roots of three plant species (Typha domingensis, Panicum hemitomon, and Taxodium distichum) were collected from each mesocosm.
Results/Conclusions
AM and DSE colonization was significantly affected by treatments. Hyphal and total colonization in T. domingensis and P. hemitomon were significantly affected by water quality. Hurricane exposure significantly increased colonization of AM hyphae, arbuscules, coils, and vesicles in T. domingensis. DSE hyphal and total colonization were significantly affected by hydrology in P. hemitomon. AM and DSE colonization in T. distichum was not affected by any treatment. In mixed roots extracted from soils, hyphal colonization was affected by hydrology, interaction of water quality x hurricane exposure, and interaction of hydrology x sedimentation. Arbuscular colonization decreased with increasing salinity and water availability. Vesicular colonization was affected by the interaction of water quality x hydrology x hurricane exposure and the water quality x hydrology x sedimentation. Similarly, DSE hyphal colonization decreased in the flooded compared to the mesic treatments, and was also affected by the interaction of water quality x hurricane. Spore density was significantly lower in the sediment added treatments and was also affected by the interaction of water quality x hydrology x hurricane. Our results show that natural and human induced alterations in water quality and hydrology have significant impacts on AM and DSE symbiosis in coastal marsh vegetation.
