UVM Theses and Dissertations
Format:
Print
Author:
Petipas, Renee
Dept./Program:
Biology
Year:
2011
Degree:
MS
Abstract:
Arbuscular mycorrhizal fungi occur in virtually all terrestrial ecosystems where they associate with an estimated 92% of plant families. In exchange for carbohydrates provided by their host plants, AMF enhance plant access to soil nutrients. In spite of their ubiquity, little is known about how various ecological factors affect them and about the diverse role they play in natural settings. In African savannas, ungulate herbivores and soil-engineering macro-invertebrates are known to shape plant populations and communities. These may, in turn, affect plant relationships with mycorrhizae and the degree to which plants benefit from their mycorrhizal partnerships.
Here, I examined patterns of mycorrhizal diversity, infectivity, and colonization of field collected roots in treatment plots where ungulate herbivores were allowed or excluded, and on and off termite mounds. I measured mycorrhizal species richness, mycorrhizal infectivity, and field colonization patterns in a fully factorial design from areas with or without ungulate herbivores in soils from on and off termite mounds. I also measured nutrient conditions and plant diversity in these same areas to describe indirect effects related to termites and ungulate herbivores that may influence fungal communities. In general, AMP species richness and infectivity was highest off-termite mounds, especially in samples taken from areas where herbivores were present. However, the pattern of colonization from field-collected roots was slightly different. Unfenced areas where herbivores were present had the highest colonization, but I found no effect of termite mounds. These results help to confirm the role ofboth ground-dwelling termites and ungulate herbivores as key-players across the semi-arid savanna landscape.
In addition to providing plants with scarce nutrients, AMF may also enhance drought tolerance. In some cases, the ability of AMF to provide benefits to their host plants depends on the habitats from which they come and to which they may be locally adapted. To explore this, I examined how mycorrhizal communities, collected from field sites with different edaphic conditions, affect drought tolerance in their hosts. I inoculated plants with AMF fungi collected from high clay, low nutrient off termite mound soils and low clay, higher nutrient on termite mound soils. My results indicate that arbuscular mycorrhizal fungi (AMF) are important for plants in recovering from drought. AMF-inoculated plants closed stomata more during drought and opened stomata more when fully watered. AMF inoculated plants also added more leaves post drought than nonAMF plants. Plants that were inoculated with fungi collected from termite mounds were consistently larger than plants inoculated with off-mound fungi, and significantly larger than non-mycorrhizal drought stressed plants. These results suggest AMF playa significant role in drought tolerance and that the magnitude ofthis response may depend on the fungal community present.
Here, I examined patterns of mycorrhizal diversity, infectivity, and colonization of field collected roots in treatment plots where ungulate herbivores were allowed or excluded, and on and off termite mounds. I measured mycorrhizal species richness, mycorrhizal infectivity, and field colonization patterns in a fully factorial design from areas with or without ungulate herbivores in soils from on and off termite mounds. I also measured nutrient conditions and plant diversity in these same areas to describe indirect effects related to termites and ungulate herbivores that may influence fungal communities. In general, AMP species richness and infectivity was highest off-termite mounds, especially in samples taken from areas where herbivores were present. However, the pattern of colonization from field-collected roots was slightly different. Unfenced areas where herbivores were present had the highest colonization, but I found no effect of termite mounds. These results help to confirm the role ofboth ground-dwelling termites and ungulate herbivores as key-players across the semi-arid savanna landscape.
In addition to providing plants with scarce nutrients, AMF may also enhance drought tolerance. In some cases, the ability of AMF to provide benefits to their host plants depends on the habitats from which they come and to which they may be locally adapted. To explore this, I examined how mycorrhizal communities, collected from field sites with different edaphic conditions, affect drought tolerance in their hosts. I inoculated plants with AMF fungi collected from high clay, low nutrient off termite mound soils and low clay, higher nutrient on termite mound soils. My results indicate that arbuscular mycorrhizal fungi (AMF) are important for plants in recovering from drought. AMF-inoculated plants closed stomata more during drought and opened stomata more when fully watered. AMF inoculated plants also added more leaves post drought than nonAMF plants. Plants that were inoculated with fungi collected from termite mounds were consistently larger than plants inoculated with off-mound fungi, and significantly larger than non-mycorrhizal drought stressed plants. These results suggest AMF playa significant role in drought tolerance and that the magnitude ofthis response may depend on the fungal community present.