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A Global Test of the Diversity-Productivity and Diversity-Stability Hypotheses Australia Hautier, Borer, Lind, Seabloom, Anderson, Harpole, Hector, Hillebrand,

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Presentation on theme: "A Global Test of the Diversity-Productivity and Diversity-Stability Hypotheses Australia Hautier, Borer, Lind, Seabloom, Anderson, Harpole, Hector, Hillebrand,"— Presentation transcript:

1 A Global Test of the Diversity-Productivity and Diversity-Stability Hypotheses Australia Hautier, Borer, Lind, Seabloom, Anderson, Harpole, Hector, Hillebrand, Mac Dougall, Meyer, Prober, Ries, Stevens + Anyone interested

2 Along the natural diversity gradient represented by 39 herbaceous-dominated plant ecosystems on five continents, plant cover at the species and ecosystem organizational levels was stabilized with increasing plant species richness, as indicated by a decrease of the temporal variability. On average, the plots with the highest diversity were about 40% more stable in time than the plots with the lowest diversity.

3 Fertilization significantly reduced species richness; on average 1.2 species (SEM = 0.4) were lost with fertilization relative to the controls. Along the reduced diversity gradient plant cover at all organizational levels was not related to species richness. The results support the diversity-stability hypothesis that greater diversity leads to greater ecosystem stability in natural systems and demonstrate that fertilization has negative effect on ecosystem stability.

4 Global Drivers of Loss of Biodiversity with Eutrophication Hautier, Hector, Anderson, Grace, Seabloom, Borer, Lind, Stevens, Harpole + Anyone interested Australia

5 Potential mechanisms explaining the loss of plant diversity with fertilization General increase in the strength of competition – aboveground for light and belowground for nutrients (Grime 1973) Increase in the strength of aboveground competition for light only (Newman 1973, Tilman 1982) Acidification (Silvertown et al. 2006) Accumulation of plant litter (Berendse 1999, Foster et al. 1998, Lamb 2008, Tilman 1993)

6 Using AMOS we made a Structural Equation Modeling to explain the changes in proportional species richness between the control and NPK+ plots. We found that once we controlled for the covariateelevation, proportional richness loss is greatest (1) where light reduction is greatest, and (2) where pretreatment evenness was low. Dead biomass had no effect on the change in species richness as well as other mechanisms such as acidification of competition for nutrients. ElevationEveness Proportion of total biomass change Proportion of dead biomass change Proportion of change in light Proportion of change in richness

7 Eurasian herbaceous species are better competitors for nutrients away from home 17 species (8 grasses & 9 forbs); 25 sites: 3 UK, 3 EU, 1 China (native sites), 16 US, 1 CA and 1 AU 3 years of treatments Ran separate analyses for introduced sites with multiple study species or just one species Analyses: Population level: LMEM with temporal autocorrelations-extracted parameter estimates; Community level (only included 10 sites that shared 5 or more study species, 5 in native and 5 in introduced): PERMANOVA and tested study species associations (positive, negative and neutral) pre- and post-treatment. Nutshell: Eurasia herbaceous species are stronger competitors in their away range and consumers likely enable their persistence in native communities. Responses (relative cover) to nutrient additions and consumer treatments differ home and away, and depending on life-form (grass or forb) Nitrogen and phosphorus increase away; no change home Fencing: no change or increase (when nutrients added) at away sites; decrease at home Grass spp. Interactions at sites with 5 or more study species tended to be positive at home but negative away. Where forbs had more negative interactions at home but positive away.

8 Relative importance of deterministic vs. stochastic community assembly increases with increasing productivity (experimental) Davies, Melbourne, Chase, NCEAS working group, all data contributors and anyone who is interested. What we see: By year three, increasing productivity created communities that deviate further from the null than communities (are more nichey) in which productivity was not increased. Further, the effect varies with baseline productivity: at low productivity sites, increasing productivity does not change community structure, while at productive sites, increasing productivity creates communities that are more deterministic. Related: increasing productivity reduced beta diversity in some treatments: NPK Other thoughts: We are hoping that the results will strengthen further in year four. We plan a second panel of graphs that include some environmental variables like temperature and rainfall that might help further explain what is going on. It would make sense to report the effects of nutrient addition on alpha and gamma diversity -- an option would be to have this paper follow up the paper that reports these results. Working title:

9 Green=controls, Black=treatments, x-axis= observed productivity in the first year, pre treatment

10 Dominant plant species drive the ecosystem response to variation in resource availability across a precipitation gradient Kimberly La Pierre, Dana Blumenthal, Cynthia Brown, Julia Klein, and Melinda Smith Submission in Summer 2012

11 Study Sites TGP SGS MIX SGS: Shortgrass Steppe (Shortgrass LTER) MIX: Mixed-grass Prairie (Saline Experimental Range) TGP: Tallgrass Prairie (Konza Prairie LTER)


13 Plant trait responses to chronic nutrient additions Kimberly La Pierre and Melinda Smith Data collected and analyzed Writing in Summer 2012 Submission in Fall 2012

14 Natural Dominants Altered Dominants Control Nitrogen Phosphorus Nitrogen and Phosphorus short-term

15 Nutrient additions alter invertebrate community structure and feeding strategy Kimberly La Pierre and Melinda Smith Data collected and analyzed Writing in Fall/Winter 2012 Submission in Spring 2012

16 PN plant biomass invertebrate herbivores K invertebrate predators invertebrate parasitoids TGP 1 3 2 4 Χ 2 =5.480, df=15, p=0.987, RFI=0.874 0.522 0.311 0.502


18 Phylogenetic, functional, and plant trait diversity: Examining potential drivers of primary production in herbaceous systems Network-wide opt-in manuscript Data collection and analysis in 2012 Write in Spring 2012

19 NutNiche A global test of niche destruction and biodiversity loss Lead: Stan Harpole (opt-in) Evidence for multiple nutrient limitation Addition of nutrients to remove limitation = niche destruction Loss of species with greater numbers of added nutrients Link to other MSs: – Hautier, Grace, et al. – Fay et al. 1/2

20 NutNiche general pattern, but site variation: not all sites show predicted response mostly multi/co-limitation (~63%); super-additive (~45%) mostly not sampling effect (~80% sites multiple additions > single) different nutrients important for different responses: – max richness effect max biomass effect covariates, not much, so far Status: rough draft To do: – composition responseget at species tradeoff assumption? – using max trt year (responses over time appear consistent but increase with time) – other? 2/2

21 N-Gradient functional response, critical loads Lead: Stan Harpole (opt-in) CBGB, CDCR, SEDG N- gradients – 0,1,5,10 g m-2 yr-1 General N10 patterns Status: need to write up soon! NutNet add-ons: – N-dep collectors – N1 treatments 1/1

22 Global Ecology SS 20: Global Environmental Challenges Require Global Ecological Research – MS for Frontiers status: some text, outline for ESA panel to do: synthesize panel results – Meeting Report (like White et al. Bio Lett) – SeSynC proposal status: draft to do: develop sociology 1/1 Organization/Network Biosphere 2 EPA EREN FunDivEurope, Biodepth-Jena LTER NEON NSF Dimensions of Diversity Numerical Terradynamic Simulation Group Nutrient Network Phenology Network TraitNet, BioMERGE ZEN seagrass network GLEON

23 (Opt-out) Answering one of the 3 original NutNet questions: Under what conditions do grazers or fertilization control plant diversity and productivity? This papers goal is to examine vertebrate herbivory x nutrient supply on plant diversity relative abundance (evenness) net primary production within the context of site and regional drivers climate soils regional productivity regional diversity NUTRIENTS AND HERBIVORES CONTROL PLANT DIVERSITY AND FUNCTION IN A GLOBAL GRASSLAND EXPERIMENT

24 Results 1.Fertilization: species richness declined and live biomass increased (p=0.0001 and p=0.001, respectively); 2.Fences: no overall effect on plot-scale richness, evenness, or biomass 3.Inside fences, NPP declines through time, but this effect is counteracted with fertilization 4.Both Bray-Curtis & Jaccard metrics show that species in plots turnover in response to both fertilization and fencing (will also test contingency on site diversity) We will also look at: 1.the association between grassland responses to fencing and fertilization among and within sites (log-ratios) 2.the relationship b/w turnover and change in biomass predictors (contingencies) – best models of change in richness, evenness, and biomass as a function of soils, climate, and site-level diversity, evenness, NPP (test of Gruner/Bolker model of additivity; Hillebrand contingencies model) Next steps: re-run with current data; make final figures; hone message; write discussion

25 What are the biogeographic patterns of species invasions? Biological Invasions (Seabloom et al.) Mainly focuses on observational data Rejected from PNAS April 2012 – positive reviews but there were concerns about site selection criteria and land use history (e.g., agriculture and grazing) Currently preparing for submission to Ecology or Global Change Biology (Other suggestions welcome) Main changes will be adding in land use and grazing data from Cini and Suzannes survey, adding in site selection survey data, and removing the bimodal graph.

26 Nutrient addition caused a loss of 0.6 native species per year but had no effect on exotic diversity Nutrient addition caused exotic cover to increase 6% per year but had no effect on native cover Have had first round of reviews by all authors with no major hiccups from anyone Still a bit undecided about target journal Are native and exotic species functionally distinct? Biological Invasions (Seabloom et al.)

27 What are the effects of fertilization and herbivory on spatial and temporal turnover of species composition Damschen, Gruner, Hillebrand, Lind, Wragg, Wright, Yang Adler, Bakker, Cavender-Barres, Dev, Orrock, Sullivan

28 Three motivating questions NF Y1 NF Y3 C Y1 C Y3 Spatial heterogeneity – mean similarity within treated plots relative to mean similarity within control plots Spatial turnover– mean similarity between treated plots and control plots relative to mean similarity within control plots Temporal Turnover– mean similarity between treated plots in Y1 and Y3 control plots relative to mean similarity within control plots in Y1 and Y3 t-values (>2 ~significant) Heterogeneity within treatments Log RatioFertFenceFert*Fence JaccardY2..2.632 BrayY2... JaccardY3... BrayY3... Spatial Turnover between treatments JaccardY2... BrayY23.298.. JaccardY3... BrayY32.149.. Temporal turnover between treatments JaccardY22.498.. BrayY2.. JaccardY3-- BrayY3..2.32

29 To do Re-run with this years data – Are lack of effects in Y3 due to limited sample size Test important question: What controls between site variability Predictor variables: – Site fertility (Y0 mean productivity) – Site sensitivity (Log response of productivity to trts) – Species Pool – Evenness, site α

30 Grassland Soil Stoichiometry at the Global Scale Currently working on a manuscript draft explaining the abundance and stoichiometry of soil organic matter in relation to climate and vegetation using NutNet observational data The distribution of soil stoichiometric ratios is an order of magnitude larger than previously reported Redfield-like ratios for soil; this is largely due to large variation in phosphorous as reflected in C:P and N:P ratios

31 C and N are highly correlated with little relationship between C and P and N and P despite a previous meta-analysis reporting these relationships In addition, we see strong relationships between climate (temperature and precipitation) with SOM and very weak relationships between productivity or diversity These different factors may make it difficult to apply cornerstones of ecological stoichiometry like the Redfield ratio to grassland soils at the global scale

32 species response to treatments: competition-defense v growth-defense 32 Eric Lind Elizabeth Borer Eric Seabloom Peter Adler Jonathan D. Bakker Dana Blumenthal Mick Crawley Kendi Davies Jennifer Firn Dan Gruner Stan Harpole Yann Hautier Helmut Hillebrand Johannes Knops Brett Melbourne Brent Mortensen Anita C. Risch Martin Schuetz Carly Stevens Peter Wragg

33 33

34 34

35 Effects of primary production and producer diversity on consumer biomass Lind, Borer, Kay, Wolkovich, Wright, Gruner, Yang, LaPierre, others…. Does primary productivity predict "secondary productivity"?


37 Native-Exotic Richness Relationship (NERR) 32 Nutnet sites: native grasslands from four regions (Australia, Central, Intermountain, and Pacific. Four sections: Scale-dependent relationships between native and exotic richness (four scales: subplot 1m 2, plot, site, and region). Drivers of NR and ER: independent or interactive? [Jenn Firn] Scale-dependent heterogeneity (Davies et al. 2005, 2007; Melbourne 2006): the impacts of CV on the NERR slope. Species associations: are species pairs more positively or negatively associated with each other, than expected by chance (Fridley et la. 2004, 2007)? [Joe Bennett]

38 Australia Pacific Central Intermountain f Native richness (fine-scale 1 m -2 ) Exotic richness (fine-scale 1 m -2 ) frequency NS Negative slopes Positive slopes

39 Fixed effects F values (df as subscript), P value INT_richF 1, 460 =0.68, P< 0.50 MAPF 1, 8 =1.34, P< 0.30 MATF 1, 8 =6.14, P< 0.04 MAP_VARF 1, 8 =13.90, P< 0.006 Temp_VARF 1, 8 =0.09, P< 0.80 Int_rich MAP_VAR F 1, 460 =3.15, P< 0.08 MAP MAT F 1, 8 =6.80, P< 0.04 MAP_VAR Temp_Var F 1, 8 =3.55, P< 1.0 Plot-level native richness [random intercepts due to site (σ 2 site ), and block within site (σ 2 block ). Full model AICc =2261; simplified model with StepAIC function AICc=2247] Fixed effects F values (df as subscript), P value Nat_richF 1, 456 =3.21, P< 0.08 MAPF 1, 12 =0.93, P< 0.40 MAP_VARF 1, 12 =5.68, P< 0.04 MATF 1, 12 =5.47, P< 0.04 Temp_VARF 1, 12 =3.48, P< 0.09 Nat_rich MAP F 1, 456 =0.00006, P< 1.0 Nat_rich MAP_VAR F 1, 456 =12.94, P< 0.0004 Nat_rich Temp_VAR F 1, 456 =0.07, P< 0.80 MAP MAT F 1, 12 =7.31, P< 0.02 Nat_rich x MAP x MATF 1, 456 =13.74, P< 0.0002 Plot-level introduced richness {random intercepts due to region (σ 2 region ), site within region (σ 2 site ), and block within site within region (σ 2 plot ). Full model AICc =1593; simplified model with StepAIC function AICc=1584 Fixed effects F values (df as subscript), P value MAPF 1, 21 =0.91, P< 0.40 MATF 1, 21 =2.72, P< 0.20 Temp_VARF 1, 21 =12.75, P< 0.002 MAP x MATF 1, 21 =2.05, P< 0.20 MAP Temp_VAR F 1, 21 =3.98, P< 0.06 Site-level native richness [random intercepts due to region (σ 2 region ), and site within block (σ 2 site ). Full model AICc =273; simplified model with StepAIC function AICc=256] Fixed effects F values (df as subscript), P value NAT_richF 1, 14 =1.83, P< 0.20 MAPF 1, 14 =0.70, P< 0.50 MATF 1, 14 =2.86, P< 0.20 MAP_VARF 1, 14 =8.5, P< 0.01 Temp_VARF 1, 14 =0.80, P< 0.40 MAP x MATF 1, 14 =4.80, P< 0.05 Nat_rich Temp_VAR F 1, 14 =2.47, P< 0.15 Nat_rich MAP F 1, 14 =0.24, P< 0.70 Nat_rich MAT F 1, 14 =0.05, P< 0.90 Nat_rich MAP x MAT F 1, 14 =0.61, P< 0.50 Nat_rich MAP x Temp_VAR F 1, 14 =2.98, P< 0.20 Site-level introduced richness [random intercepts due to region (σ 2 region ), and site within region (σ 2 site ). Full model AICc =236; simplified model with StepAIC function AICc=227]

40 Proportion of significant correlations ** A. Site-level species associations - natives vs. exotics B. Plot-level species associations - natives vs. exotics ** contrasts the proportion of significant asstns that are positive vs those that are negative

41 A global study of below-ground allocation patterns in grasslands Proportional root allocation should decline when growth is limited by above-ground resources (e.g. light), and increase when growth is limited by below-ground resources (e.g. water and nutrients). Extracted roots from 21 sites (8 more expected this summer) Plan to do a full analysis and write much of a paper this week (hope that the additional sites do not change the main results substantially)

42 Specific hypotheses Proportional root allocation will decline as total production increases – With increasing number of nutrients added – Inside herbivore exclosures (high litter accumulation leading to light limitation) Flexibility in allocation will decline with decreasing soil moisture availability (interaction between nutrient addition and site-level mean rainfall)

43 Manuscript 1: Strong abiotic controls over seed removal in a continent-wide study Status: analyses completed, ms drafted, submit after current round of comment by co-authors (Ecology is target journal) Authors: Orrock, Brudvig, Firn, MacDougall, Yang, Melbourne, Baker, Bar-Massada, Borer, Crawley, Damschen, Davies, Gruner, Kay, Lind, McCulley, Seabloom.

44 Manuscript 2: Contingency in consumer- mediated invasion Status: introduction drafted, analyses in progress. Pending completion of analyses, send discussion draft to co-authors by September, submit ms by November Objective: examine how the role of consumers in affecting exotic plant abundance varies as a function of abiotic constraints (e.g. temperature, precipitation) Authors: Orrock, Firn, Bakker, Blumenthal, Borer, Brown, Brudvig, Buckley, Chu, Cleland, Cottingham, Crawley, Damschen, Davies, Firn, Frater, Gruner, Kay, Kirkman, Klein, Knops, LaPierre, Leakey, Li, Lind, MacDougall, McCulley, Melbourne, Moore, Morgan, Nelson, Prober, Seabloom, Stevens, Wolkovich, Wright, Yang

45 Manuscript 3: Biofuel potential of three semi- natural grasslands Objective: examine the energy produced by plant biomass derived from grasslands in CA, MO, and SC Authors: Orrock, Watling, Brudvig, Damschen, Borer, Seabloom, Baker Status: analyses need to be re-visited, ms drafted, revise discussion, send to co-authors, then submit (Ecological Applications is target journal)

46 Working Title: What limits productivity in grasslands worldwide? Co-Leads: Phil Fay, Suzanne Prober, John Knops (opt-out paper) Hypotheses: 1.Nitrogen is a globally significant limitation on productivity at most sites 2.Nitrogen response of Productivity is independent of climate 3.Phosphorus limitation prominent on old, weathered soils 4.Additional nutrient (co-)limitation in some cases/places

47 Nutrient response to rainfall and temperature MAT.NChi P=0.003 MAP.NChi P<0.001 MAP.PChi P<0.001 MAT.KChi P= 0.009 Random model:site_code + site_code.year_trt + site_code.block + site_code.year_trt.block + site_code.plot + Variance structures: differing variance between sites; differing variance between pots within sites each year Currently: Fine-tuning hypotheses and statistical models Investigating covariance of nutrient effects with climate/grazing intensity variables. Need to investigate soil property effects.

48 Currently: Fine-tuning hypotheses and statistical models Investigating covariance of nutrient effects with climate/grazing intensity variables. Need to investigate soil property effects.

49 Nutrient response to rainfall MAP*N*P P=0.005, adjusted for grazing coefficient Random model:site_code + site_code.year_trt + site_code.block + site_code.year_trt.block + site_code.plot + Variance structures: differing variance between sites; differing variance between pots within sites each year

50 History of Grazing & Cultivation Survey Surveys completed for 39 sites Information from survey – Whether there is grazing currently & when started – Whether or not & when site was cultivated – Management activities w/in plots – What herbivores present & relative abundance in evolutionary, ecological, recent historic times – Timing of influential climatic events – What is the level of current and recent historic grazing (nil, low, medium, high)

51 Evolutionary History of Vertebrate Grazing and Plant Invasions What is the role played by evolutionary histories of grazing on the relative success of native and introduced plant species? Is recovery from exotic invasion with grazing exclusion influenced by the evolutionary history of grazing?

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