Downward Radiation and Limited Water Availability May Supress Forest Growth Across the Forest-Steppe Ecotone in Southern Siberia
Abstract
The rapid warming of southern Siberia's forest-steppe ecotone will likely alter vegetation cover, biomass and ecosystem productivity through shifts in species composition, carbon cycling, and disturbance regimes like fire frequency. Field and satellite observations already indicate that the forest-steppe ecotone is subject to changes in productivity and vegetation cover over the last two decades. We hypothesise that the location, direction and magnitude of such vegetation and productivity changes depend on regional variations in abiotic factors such as soil moisture conditions and extreme fire events, since field data indicate the dominance of drought/fire tolerant tree types against those that are more drought/fire sensitive. Here we use a multisensory approach to account for the role of landscape variability for changes in productivity and vegetation cover along various temperature and moisture gradients. We used the Theil-Sen method and Kendall's test for the detection of spatio-temporal trends over 20 years of NDVI from the Global Inventory Modeling and Mapping Studies (GIMMS) dataset, in conjunction with a vegetation cover dataset derived from multiple optical satellite sensors such as AVHRR, MODIS and Landsat, as well as abiotic factors from the TerraClimate archive. Preliminary results confirm our hypothesis as warmer conditions and limited water availability have constrained the growth in terms of NDVI and tree cover of needle-leaved evergreen stands along lake Baikal and across a longitudinal gradient of 106°E to 112°E, while needle-leaved deciduous stands have significantly decreased at 108°E to 112°E. NDVI decreases for both tree types are in accordance with the changes in tree cover, although tree cover decreases are of a lesser spatial extent. On the contrary, in regions with increased downward radiation, productivity and the coverage of drought/fire tolerant needle-leaved deciduous increased in both, stands with significantly and non-significantly negative trends in water availability. Finally, out of the climatic factors examined here, other parameters like human activities may either suppress or support forest growth and cause a significant lag effect on forest progression with uncertain feedbacks to both, climate and ecosystem resilience.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B23H2526B
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCES