(A)synchrony of above- and below-ground productivity in a warming tundra biome

• Main Author: Gallois, Elise
• Other Authors: Myers-Smith, Isla, Bjorkman, Anne, Street, Lorna, Doherty, Ruth
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Edinburgh 2024
• Subjects: tundra ecology; climate change; ecosystem change; phenology; carbon cycling; microclimate; polar biology; Arctic; Climate change; Tundra
• Online Access: https://hdl.handle.net/1842/41948; https://doi.org/10.7488/era/4671

Arctic and alpine tundra ecosystems are experiencing accelerated warming compared to the global average, causing significant changes in plant productivity and the timing of life histories of tundra species, with cascading effects on trophic interactions and carbon cycling. However, the sparsity of long-term and spatially-varied observations hinders our understanding of how these dynamics may continue to change in a warming tundra biome. Specific knowledge gaps, often borne from limitations on year-round travel to tundra sites, hamper our ability to accurately predict the long-term trajectory of tundra phenology change, both above-ground and below-ground. In this PhD thesis, I use above- and below-ground ecological observations across spatial and temporal scales to resolve key questions about how heterogeneous tundra landscapes may respond to future warming and ecosystem change. My findings have implications for biome-scale carbon cycling and wildlife habitats. In Chapter 2, I used a geographically varied time-lapse camera imagery to analyse tundra phenology variations across microclimates and snowmelt gradients. I found that while growing seasons were consistently longer at warmer, lower-latitude sites (11 extra days for each additional 1°C in mean summer temperature). Growing season lengths did not significantly vary across warmer or colder summers and earlier or later snowmelt timing despite warmer spring temperatures consistently advancing spring green-up. I found that early-season phenology constrained the timing of much of the mid-season phenology and early senescence, but not full senescence. Green-up, mid-season, and early senescence phenophases generally occurred earlier in warmer microclimates and tracked snowmelt, although initial community-scale bud-burst and full community senescence was not related to microclimate. Across sites, I found that green-up occurred more slowly when snowmelt was earlier and faster when snowmelt was later. If growing season length remains relatively stable across space and ...