Combined effects of climate change and nitrogen deposition on subalpine grassland

Transcription

1 Federal Department of Economic Affairs, Education and Research EAER Agroscope Combined effects of climate change and nitrogen deposition on subalpine grassland Bassin S., Volk M., Gauer A., Fuhrer J. 2 th April 216

2 N deposition on subalpine grassland Proportion Sedges.4 control + 5 kg N + 1 kg N kg N + 5 kg N Year Sign. increase at +5 kg N ha -1 yr -1 Bassin, Volk, Fuhrer; 213 Is the N sensitivity of subalpine grassland modulated by climate change? 2

3 Transplantation experiment ( ) Transplantation experiment o 5 year duration o 216 grassland monoliths o from 6 different Alps, all cattle pastures (21 m.a.s.l.) Crossfactorial design o Warming = transplantation along an elevation gradient (6 levels) o Nitrogen = biweekly irrigation with NH 4 NO 3 (3 levels) o Water = irrigation with +5% of annual sum of precipitation (2 levels) 3

4 Sites of monolith origin Zurich Nardetalia Muntatsch Laret Flix Zavretta Experimental site Ardez, Engiadina Bassa Sesleretalia Nova & Creusch 5 km 4

5 Accessing the sites of origin 5

6 Elevation gradient -1.2 control m 216 grassland monoliths from 21 m a.s.l m Ardez 6

7 Experimental design N control +3 kg N +15 kg N Water: + 5% annual precip. sum N control +3 kg N +15 kg N Alp Laret Alp Muntatsch Alp Zavretta Alp Flix Alp Nova Alp Creusch a) Disentangle warming effects from drought effects b) Test for climate change mitigation options 7

8 Infrastructure along the gradient 6 meteo stations 6 N deposition sampler o bulk sampler (wet and dry) o snow lysimeter At 3 sites: within monoliths o soil temperature o volumetric soil water content o leachate water collection (lysimeter facility) 8

9 Methods Vegetation analyses Vegetation analyses Estimation of cover of functional groups Harvest (2 cm above ground) Species list for each monolith (every third year) 9

10 Results 1

11 Soil temperature ( C) Volumetric soil water content (%) Temperature and irrigation treatment Soil temperature July C Soil water content July Late snowmelt soil temp ( C) volumetric soil water content (%) Moist summer Hot & dry summer Elevation (m a.s.l.) Elevation (m a.s.l.) non-irrigated irrigated 11

12 Harvested biomass (g m -2 ) 3 2 Biomass: temperature x irrigation Biomass 213 Late snowmelt low productivity almost no warming/drought effect Wet summer almost no irrigation effect warming stimulated productivity (except hottest site) Dry & hot summer high productivity strong irrigation effect warming stimulated productivity 1 Bassin -1 S., Volk 1 M., Gauer, 2 A., Fuhrer J. 3 non-irrigated irrigated 12

13 Cover (%) Nitrogen x temperature/irrigation Fraction of sedges fraction (%) Temperature 1 change 2 ( C) 3 N N N N3 N15 N N3 N15 non-irrigated irrigated N x temperature interaction N effect weakest at high temperatures No N x irrigation interaction 13

14 Species numbers Species number additional species 215 Calcareous sites Creusch Nova Flix Muntatsch Laret Zavretta Monolith origin Reasons for species higher species numbers: o Re-find technique o Higher probability of plant invasion o Germination from seed bank and seed dispersal 14

15 Treatment effects on species numbers Difference in species numbers specie no species no N N3 N15 N N3 N15 non-irrigated irrigated Seedling establishment is stimulated by N deposition, but only in irrigated plots. 15

16 Conclusions o o o Magnitude of treatment effects depends on seasonal weather. Warming mostly increased productivity. First indications of N effects on biomass and sedges cover at +15 kg N ha -1 yr -1. o N effect on sedges is weaker in a warmer climate. o Species numbers increased, especially in irrigated & N-treated plots. better germination conditions, but no negative effect of competition by nitrophilic sedges (yet). 16

17 Thanks! Robin Giger Simon Spöhel Raphael Etterlin Manuel Schuler Claire Schabbon Lionel Epinay FOEN Federal Office for the Environment 17

18 Change in individual species presence Typical response patterns Carex ornithopoda Trollius europaeus Alchemilla hybrida change in abundance N N3 N15 N N3 N15 non-irrigated irrigated change in abundance N N3 N15 N N3 N15 non-irrigated irrigated change in abundance N N3 N15 N N3 N15 non-irrigated irrigated Agrostis capillaris Crepis aurea Selaginella selaginoides Trifolium badium Polygonum viviparum Prunella vulgaris 18