The effect of shrinking boreal lakes on plants, soils, and microbial communities in nearshore habitats: Implications for C cycling and storage
Abstract
High latitude ecosystems are undergoing tremendous changes, including changes in the hydrology of lakes. In the Yukon River Basin of interior Alaska, there has been a long-term trend in lake shrinkage from 1980 until 2010. As lake shrinkage occurs, new sediments are exposed for colonization by terrestrial plants and microbial communities. We studied the effects of changing lake area on the ecology and biogeochemistry of nearshore terrestrial ecosystems, including plant and microbial community composition, soil carbon and nitrogen storage, and microbial activities in boreal lakes of the Yukon Flats National Wildlife Refuge. Our objective was to test whether the dynamic environments created by shrinking lakes lead to increased rates of decomposition and soil carbon losses. Historic lake area was determined using Landsat imagery. Lake margin wetland vegetation types (graminoid, deciduous shrub, and conifer forest) were sampled for soil carbon and nitrogen storage, microbial phospholipid fatty acids (PLFA for a measure of microbial community composition), and soil for lab incubations and soil enzyme assays. Wetland age (time since sediments were exposed by lakeshore retreat) and plant functional diversity were measured on 112 lake margins, while 12-20 lake margins were measured for soil organic carbon, plant NPP, and microbial characteristics. We compared these parameters among shrinking and stable lakes. Results showed that lake draining results in an increase in graminoid and shrub NPP but little change in plant functional composition. Lake draining had a clear effect on microbial community composition, with microbial communities in draining lakes dynamically changing from one plant community type to another. The decomposition rate constant (k) was lower in draining lakes, possibly due to the increased salt concentrations in draining lake soil. We assessed changes in soil C storage as a function of wetland age and found a significant loss of approximately 0.17 kg C/m2/yr among all wetland types and 20 g N/m2/yr in graminoid wetlands. Overall, wetland soils near shrinking lakes contained significantly more C and N compared to stable lakes. Changing lake hydrology impacts the ecology and biogeochemistry of nearshore terrestrial ecosystems with significant effects on soil carbon and nitrogen storage.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB123...04W
- Keywords:
-
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCES;
- 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCES;
- 1823 Frozen ground;
- HYDROLOGY