Monitoring tropical forests in a changing world

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1 Monitoring tropical forests in a changing world Martin Sullivan School of Geography University of Leeds Credit: Lan Qie

2 Tropical forests Home to ~ 50 % of terrestrial biodiversity Store ~ 180 billion tonnes of carbon in aboveground biomass Credit: Lan Qie

3 Credit: Lan Qie

4 How I ended up studying tropical forests Credit: Lan Qie

5 How I ended up studying tropical forests

6 How I ended up studying tropical forests From: Sullivan et al PLOS One From: Sullivan et al Biological Invasions

7 How I ended up studying tropical forests From: Sullivan et al Biological Conservation

8 ForestPlots.net

9 100 m Forest inventory plots Typically 1 ha Measure tree diameter Tag trees so we can track them through time 100 m Credit: Sophie Fauset, Richard Primack

10 Estimating how much carbon trees store Use allometric equations to estimate aboveground biomass from measured diameters These are based on destructive measurements of biomass where trees have been cut down, chopped up and weighed. Including tree height can improve allometric models, but is time-consuming to measure Credit: Lan Qie

11 Estimating tree height If we have measured the height of some trees we can build models to relate tree height to tree diameter Can use published models to predict height How many trees do we need to sample to outperform these models Credit: JF Bastin

12 Estimating tree height Sample size Sullivan et al. (2018) Methods in Ecology and Evolution

13 Estimating tree height Sample size Sullivan et al. (2018) Methods in Ecology and Evolution

14 Estimating tree height Sullivan et al. (2018) Methods in Ecology and Evolution

15 Conserving forests for their carbon Incentivised by schemes such as REDD+

16 If we protect the forests with the most carbon, do we also protect the most biodiverse forests?

17 If we protect the forests with the most carbon, do we also protect the most biodiverse forests? Depends on the diversity-carbon relationship If positive then we have a win-win situation If negative then there are difficult tradeoffs If no relationship then both need to be considered, but may be synergies

18 Biodiversity could enhance ecosystem function Niche complementarity diverse communities can exploit available resources more efficiently Selection effects diverse communities are more likely to contain species that contribute strongly to ecosystem functioning Credit: The Jena Experiment

19 Evidence from tropical forests Review by van der Sande et al. (2017) Biotropica Some evidence for positive effects of taxonomic diversity But also evidence for a publication bias towards publishing positive relationships

20 Are diversity and carbon related in tropical forests? 360 forest inventory plots with high quality species identifications Cover the major forest blocs of Amazonia, the Congo basin and Borneo Combined effort of 115 people from 22 countries

21 Diversity and carbon are unrelated across the tropical forest biome Sullivan et al Scientific Reports

22 Diversity and carbon are unrelated across the tropical forest biome even after accounting for climate, soil and spatial autocorrelation South America Africa Asia Sullivan et al Scientific Reports

23 The diversity-carbon relationship is scale dependent Among 0.04 ha subplots within 1 ha plots Sullivan et al Scientific Reports

24 The diversity-carbon relationship is scale dependent Among 0.04 ha subplots within 1 ha plots Among 1 ha plots Sullivan et al Scientific Reports

25 Scale dependency could be driven by saturating selection effects The probability of sampling a species that contributes strongly to ecosystem function increases through the range of species richness found in 0.04 ha subplots But saturates at diversity levels found in 1 ha plots Sullivan et al Scientific Reports

26 Tropical forests continue to take in carbon In both Africa and Amazonia there is a trend towards forests increasing in their biomass This means that forests act as a carbon sink

27 Tropical forests continue to take in carbon Why? Appears to be a global driver sink in both South America and Africa CO 2 fertilisation is an obvious candidate Support for a global driver would be strengthened if there was a carbon sink in the forests of Asia

28 Is there a carbon sink in Borneo? Lan Qie assembled a network of 71 plots, some first surveyed in 1958

29 Is there a carbon sink in Borneo? Yes! In interior forests there is a sink of similar magnitude to Africa and Amazonia Qie, Lewis, Sullivan et al. (2017) Nature Communications

30 Is there a carbon sink in Borneo? Yes! But not near edges In interior forests there is a sink of similar magnitude to Africa and Amazonia But fragmentation could stop the sink Qie, Lewis, Sullivan et al. (2017) Nature Communications

31 Is there a carbon sink in Borneo? Yes! But not near edges In interior forests there is a sink of similar magnitude to Africa and Amazonia But fragmentation could stop the sink This could be driven by compositional shifts towards lighter wooded pioneer species near edges Qie, Lewis, Sullivan et al. (2017) Nature Communications

32 The carbon sink is also vulnerable to extreme climate events The 1997/98 El Niño paused the sink Due to a pulse in mortality But increase productivity afterwards forest recovering? Qie, Lewis, Sullivan et al. (2017) Nature Communications

33 Can we use extreme climate events to infer responses to climate change? Field experiment in an annual grassland in California

34 Can we use extreme climate events to infer responses to climate change? Field experiment in an annual grassland in California

35 Can we use extreme climate events to infer responses to climate change? Field experiment in an annual grassland in California Water addition to extend or intensify the winter rainy season 10 years of data Do initial responses predict long-term responses?

36 Can we use extreme climate events to infer responses to climate change? Control plots, normal years Control plots, wet years Initial years of water addition Longterm water addition

37 Plant productivity higher when rainy season extended Control plots, normal years Control plots, wet years Initial years of water addition Longterm water addition Sullivan et al. (2016) Global Change Biology

38 Short-term and long-term rainy season extension has the opposite effect on plant species richness Sullivan et al. (2016) Global Change Biology

39 Short-term and long-term rainy season extension has the opposite effect on plant species richness with cascading effects on higher trophic levels Sullivan et al. (2016) Global Change Biology

40 What is the ecological mechanism? Initial water addition Nitrogen fixing forbs More nitrogen

41 What is the ecological mechanism? Initial water addition Nitrogen fixing forbs More nitrogen 2 nd year water addition Winter annual grasses More litter

42 What is the ecological mechanism? Initial water addition Nitrogen fixing forbs More nitrogen 2 nd year water addition Winter annual grasses More litter 3 10 years water addition Annual forbs

43 Can we use extreme climate events to infer responses to climate change? Species interactions may lead to complex long-term responses Intra-specific adaptation individuals and species less sensitive to long term than short term exposure Shifts in species composition ecological acclimation

44 Responses to spatial variation in climate a window into long-term responses? Examine spatial patterns in forest dynamics and relate to spatial variation in climate Previous work looking at inter-annual variation has found a strong effect of minimum (nighttime) temperature temperature increases respiration

45 Responses to spatial variation in climate a window into long-term responses? Examine spatial patterns in forest dynamics and relate to spatial variation in climate Previous work looking at inter-annual variation has found a strong effect of minimum (nighttime) temperature temperature increases respiration My results indicate daytime temperature is more important direct and indirect effects on photosynthesis Temperature sensitivity 2.5 fold greater from inter-annual variation than from spatial variation

46 Predicting forest responses to environmental change Responses to inter-annual variation are likely to provide an upper bound to changes over long time-scales While responses to spatial variation likely provide a lower bound Long-term spatio-temporal datasets such as ForestPlots will be crucial for understanding how short-term responses translate into longer term ones

47 Collaborative effort with Oliver Phillips Simon Lewis The EGC cluster The Rainfor, AfriTRON and T- Forces networks