Norwegian University of Science and Technology 1

Transcription

1 Norwegian University of Science and Technology 1

2 Norwegian University of Science and Technology 2

3 Arctic and alpine shrub expansion is a trend Aboveground biomass has increased in tundra ecosystems Epstein et al 2012, Myers-Smith et al 2011 Settele et al., 2014, Fifth Assessment report of the IPCC Norwegian University of Science and Technology 3

4 Arctic and alpine tundra is a giant Carbon storage 50 % of estimated global belowground Carbon (C) in Northern circumpolar permafrost regions Norwegian University of Science and Technology 4 Tarnocai et al 2009, Global biogeochemical cycles

5 Predicted soil carbon loss by 2050 Under the no acclimatization scenario In soil C stocks 0-15 cm depth Under 1 C rise in soil surface temperature Norwegian University of Science and Technology 5 Crowther et al 2016, Nature

6 Shrub expansion may increase carbon cycling Abo CO 2 Atmosphere GEP ER Above-ground Below-ground Biomass Soil R shoots R Heterotrophic R roots R Heterotrophic ER GEP = Gross ecosystem photosynthesis ER = Ecosystem respiration Norwegian University of Science and Technology 6

7 Shrub expansion may increase carbon cycling GEP ER GEP ER Above-ground Abo Above-ground Below-ground Biomass Below-ground Biomass Soil Soil GEP = Gross ecosystem photosynthesis ER = Ecosystem respiration Norwegian University of Science and Technology 7

8 Study aim Shrub C budgets compared to tundra meadow and heath C Above ground Litter C Litter C Below ground I) Compare shrub C fluxes to that of heath and meadow II) Estimate where and how much C is stored in the different communities GEP ER Heath Norwegian University of Science and Technology 8 Salix-shrubs

9 Field site and sampling Salix shrub Herb-and cryptogam snow-patch meadow Empetrum heath Norwegian University of Science and Technology 9

10 Herbivores present in the area Low-intensity sheep grazing (25 sheep per km 2 ) Voles and lemmings Ptarmigan Hare Moose Occasionally wild reindeer Norwegian University of Science and Technology 10

11 Method CO 2 fluxes Carbon sequestration Net Ecosystem Exchange = GEP + ER CO 2 -flux measurements July and August 2015 See more on the blogpost Mia Vedel Sørensen, Rozalia Kapaz and Diana Eckert, measuring in the Salix shrub community Norwegian University of Science and Technology 11

12 C pools above- and below-ground 68 cm Norwegian University of Science and Technology 12

13 Results Norwegian University of Science and Technology 13

14 Greater C fluxes in meadow and shrub communities Norwegian University of Science and Technology 14

15 Above-ground C pools More above-ground C in the shrub community Norwegian University of Science and Technology 15

16 14 % of total C 16 % of total C 51 % of total C Total ecosystem C: Meadow was twice that of the shrub community 1.5 times more C in the heath than in the shrub Norwegian University of Science and Technology 16

17 Norwegian University of Science and Technology 17

18 Norwegian University of Science and Technology 18

19 Norwegian University of Science and Technology 19

20 Norwegian University of Science and Technology 20

21 Summer C fluxes do not explain total C pools Norwegian University of Science and Technology 21

22 Discussion Summer C fluxes do not explain total C pools because of Ecosystem processes outside of the growing season Later snowmelt in shrub community? Different decomposers in the three communities? Different history? Heath Meadow Shrub Norwegian University of Science and Technology 22

23 Conclusion Shrubs might be draining the pool Norwegian University of Science and Technology 23

24 Herbivores may reduce shrub expansion More focus is needed on: Soil and below-ground processes Norwegian University of Science and Technology 24

25 Questions? Thanks to: ECOSHRUB s great field assistants and collaborators. Nansenfondet IK Lykkes fond The Norwegian research council Contact mia.vedel.sorensen@ntnu.no mi.vemde Norwegian University of Science and Technology 25