Quantifying the magnitude of species richness and its turnover on ecosystem productivity by the rate of N inputs in a temperate grassland

Transcription

1 Quantifying the magnitude of species richness and its turnover on ecosystem productivity by the rate of N inputs in a temperate grassland Yunhai Zhang et al. Thursday, June 09, 2016

2 1. Background Erisman et al., 2011 Curr. Opin. Environ. Sustain. Reactive nitrogen deposition has increased and contributed to widespread changes in the structure and functioning of natural and management ecosystems. 2

3 Projections on N deposition Globe nitrogen fertilizer (million tonnes) Production Consumption Globe Year China Europe China and Europe N fertilizer (million tonnes) Global average atmospheric N deposition will continue to increase as increasing global N fertilizer production and consumption (data from FAO 2015) due to N fertilizer is the most relative factor to be associated with atmospheric N deposition.

4 Projections on global N deposition Galloway et al Biogeochemistry 2050s 1960s 1990s 4

5 China N deposition N deposition(kg N ha 2 yr 1 ) A, 1990s Liu et al Nature Jia et al., 2014 Sci. Rep. B, 2000s It is an idea ecosystem to conduct stimulating N deposition experiments.

6 Possible pulse effects of nitrogen in theory N deposition N fertilization Smith et al., 2009 Ecology

7 It may like this

8 Suddenly

9 High frequency (more times)

10 Low frequency (fewer times)

11 High frequency (more times) Does exist same effect on plant diversity, ecological processes and ecosystem functioning? Low frequency (fewer times)

12 2. Experiment Replicate The rate of N addition The frequency of N addition

13 How many replicates? Standard deviation Aboveground biomass Species richness 25 (a) r 2 = 0.93 p< Plot number (sample order) (b) r 2 = 0.91 p< Plot number (sample order) Standard deviation At least 10 plots for every treatment. 13

14 Biomass yield(kg hm 2 yr 1 ) The level of nitrogen addition David C. Whitehead Year 2000 CABI Publishing Page 109 Fig. 5 3 N-rate(kg hm 2 yr 1 ) 14

15 The frequency of nitrogen addition Two frequency of nitrogen addition, 1). 2 N additions yr -1 (twice year -1 ) 2). 12 N additions yr -1 (monthly) Nine rates of nitrogen addition, (0, 1, 2, 3, 5, 10, 15, 20, and 50 g N m -2 yr -1 ) Control and mowing, (mowing in August for simulation hay management in the region)

16 E N 中华人民共和国 Experimental site

17 In total, 38 Treatments; 380 Plots 17

18 3. Results 3.1 Species richness 3.2 Species gain and lose 3.3 Ecosystem ANPP 3.4 Species richness contributions to ecosystem ANPP

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21 3.1 Species richness Species richness (m -2 ) (a) 2 N additions yr N additions yr -1 F: 7.5** N: 18.0*** F x N: 0.7 ns Year (Zhang et al., 2014 Global Change Biology) 9 (b) r 2 = 0.83 p<0.001 r 2 = 0.95 p< N addition rate (g N m -2 yr -1 ) Species richness (m -2 ) Rapid species loss at high rates and at low frequency of N additions.

22 3.2 Species gain and lose Gains of species Species richness Losses of species

23 3.2.1 Annual species gained and lost (Zhang et al., 2016 Functional Ecology) The annual number of gained species (a) 2 N additions yr N additions yr -1 R 2 = 0.38 P<0.1 R 2 = 0.71 P<0.05 The annual number of lost species (b) R 2 = 0.74 P<0.01 R 2 = 0.51 P< N addition rate (g N m -2 yr -1 ) N addition rate (g N m -2 yr -1 ) The rate of N addition decreased new gained species and increased lost species.

24 3.2.2 Cumulative species gained and lost Species gained for (a) 2 N = 2 N additions yr N = 12 N additions yr -1 P<0.05 Control 2 N 12 N Treatment Species lost for (Zhang et al., 2016 Functional Ecology) (b) P> Control 2 N 12 N Treatment Fewer new species gained at low frequency of N addition.

25 3.3 Ecosystem ANPP 500 (a) 350 (b) Ecosystem aboveground net primary productivity (ANPP; g m -2 yr -1 ) g N m -2 yr Ecosystem ANPP (g m -2 yr -1 ) N additions yr N additions yr -1 Similar slopes: P> Year Log 10 (N addition rate) (g m -2 yr -1 ) (Zhang et al., 2015 Scientific Reports) The rate rather than the frequency of N addition affects productivity.

26 3.4.1 Effect of N on ecosystem ANPP 1.0 (a) 1.0 (b) 1.0 (c) Effects of N on ecosystem ANPP (standardized effect size) R 2 = 0.99 P< Direct effects of N on ecosystem ANPP (standardized effect size) R 2 = 0.91 P< Indirect effects of N on ecosystem ANPP (standardized effect size) R 2 = 0.96 P< Log 10 (N addition rate) (g m -2 yr -1 ) Log 10 (N addition rate) (g m -2 yr -1 ) Log 10 (N addition rate) (g m -2 yr -1 ) Nitrogen enrichment directly and indirectly affected ecosystem production. Direct effect was smaller than the indirect effect as all rates of N as a whole.

27 3.4.2 Species richness effect Effects of N on observed species richness (standardized effect size) (a) R 2 = 0.90 P< Log 10 (N addition rate) (g m -2 yr -1 ) Effects of observed species richness on ecosystem ANPP (standardized effect size) (b) R 2 = 0.77 P< Log 10 (N addition rate) (g m -2 yr -1 ) Effect on ecosystem production from species richness was negative with diminishing return under N-enriched.

28 Effect size of lost species on ANPP response Effect of lost species on ecosystem ANPP (standardized effect size) Effect size of gained species on ANPP response (a) (b) (c) (d) Species richness contributions Lost ANPP response N 12 N N frequency R 2 = 0.49 P<0.001 Log 10 (N addition rate) (g m -2 yr -1 ) Effect of gained species on ecosystem ANPP (standardized effect size) (e) Gained ANPP response R 2 = 0.13 P< N 12 N N frequency Log 10 (N addition rate) (g m -2 yr -1 ) Effect size of inert species on ANPP response Effect of inert species on ecosystem ANPP (standardized effect size) Log 10 (N addition rate) (g m -2 yr -1 ) R 2 = 0.41 P>0.05 R 2 = 0.71 P<0.05 R 2 = 0.21 P>0.1 (f) Inert species ANPP response R 2 = 0.53 P< N 12 N N frequency Log 10 (N addition rate) (g m -2 yr -1 ) Log 10 (N addition rate) (g m -2 yr -1 ) Log 10 (N addition rate) (g m -2 yr -1 )

29 4. Conclusions Both pulse- and cumulative-effects of N affected ecological processes and functioning. The contributions to ecosystem production via new gained species decreased with the increasing N addition rate, while the contributions through inert (persisting) species was relative large and constant.

30 5. ACKNOWLEDGEMENT Thank you! 谢谢! Thanks everyone in Prof Xingguo Han s group, Dr Carly Stevens, Prof Michel Loreau and Dr Forest Isbell. Thanks Centre of Hydrology & Ecology. zhangyh670@gmail.com