1. Ecosystem Services in French Guiana old-growth rainforests
IUFRO Landscape Ecology in Tartu /08/2015
Ecosystem Services in French Guiana old-growth rainforests
The geomorphological landscapes are key-factors for predicting spatial variation of ecosystem services in undisturbed tropical rainforests
This presentation focuses on the spatial variation of ecosystem services in undisturbed rainforest in relation with the geomorphology. It is based on a study that took place in French Guiana.
S.Guitet – IRD, UMR Amap, Montpellier (France)

2. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
French Guiana : a part of Guiana Shield covered by natural old-growth rainforest with few recent anthropic disturbances …
French Guiana is a part of Guiana Shield that is located in the northern Amazonian forest. This territory of eighty thousand square-kilometers is covered by old-growth forest and remains quite undisturbed. There are only 2 hundred and fifty thousand inhabitants but the demographic rate is very high so that harvesting as well as mining are planned to increase during the next decades.
… but high demographic rate and many conflictual issues regarding land-uses
V. Gond et al. (2011) Broad-scale spatial pattern of forest landscape types in the Guiana Shield. International Journal of Applied Earth Observation and Geoinformation, Volume 13, Issue 3, , 357–367.
Geomorphological landscapes and ecosystem services in French Guiana rainforest

3. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
coastal plains
Moderate reliefs but a high geomorphodiversity that shapes various landscapes …
multi-concave
multiconvex
tablelands
At the first glance, the relief appears to be quite moderate and homogeneous in this small part of Amazonian forest. But the Digital Elevation Model provided by SRTM reveals a significant variability of landforms that is the source of great variability of landscapes. Using statistical spatial analyses, we were able to define twelve types of geomorphological landscapes belonging to five main categories : coastal plains and large valleys, multiconcave reliefs on large inland watershed, multiconvex reliefs on moderate hills, plateaus and small mountains up to eight hundred meters of altitude.
mountains
S.Guitet al. (2013) Landforms and landscape mapping, French Guiana (South America). Journal of Maps, Volume 9,
Geomorphological landscapes and ecosystem services in French Guiana rainforest

4. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
… and that explains large scale patterns of forest composition
Variograms of floristic composition
Family : 36% of variance Taxa (mainly genus) : 33%
S.Guitet al. (2015) Geomorphological landscapes features explain floristic patterns in French Guiana rainforest. Biodiversity and Conservation, Volume 24, 1215:
We demonstrated in previous studies that this geomorphodiversity explains a large part of large scale patterns of forest composition at species and families levels, for trees. In fact, the increase in the dissimilarity of composition, that you can see on the variograms on the top-right, is almost totally explained by the influence of geomorphological landscapes changes.
Geomorphological landscapes and ecosystem services in French Guiana rainforest

5. ? 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Ecosystem Services :
Carbon regulation, Timber production, Biodiversity ?
Geomorphological landscapes
Forest composition and diversity
Soil filtering
(niche effect, edaphic and physical filter)
Soil-systems
Pedogenesis
(soil evolution and transformation)
In fact geomorphological landscape features are usually assumed to be good proxies for soil-systems because morphogenesis and pedogenesis share the same processes which are erosion, weathering, sedimentation, landslides. This can explain a part of the effect of geomorphological landscapes on forest composition and diversity through soil filtering. Therefore we can logically suppose that geomorphological landscapes directly or indirectly influence Ecosystem Services but what is the extent of this influence ? and do the changes in diversity involving significant changes for production and regulation services ?
Geomorphological landscapes and ecosystem services in French Guiana rainforest

6. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Estimating diversity of trees communities with rapid assessments at large scale (111 transects at 33 sites)
29 botanical plots x 1 ha
(6,349 trees)
111 forestry surveys (20m x 2-3km = 123,906 trees)
Accuracy
- family
- genus
- species
Reliability
- per DBH
- per group
Simulations of floristic composition (Monte-Carlo)
To test these hypotheses we used rapid assessments based on forestry surveys located in thirty three sites that represent the main geomorphological features for the region and compute different indicators for ecosystem services. Firstly we used a sub-sample of forest inventories coupled with botanical plots to estimate the accuracy and reliability of the forestry data. We then developed a method based on Monte-Carlo simulations to compute diversity indices taking into account the taxonomic uncertainties and we produced indicators for biodiversity as supporting service. We used the same method to estimate indicators of timber stocks that is the main provisioning service in the region.
Estimates for diversity indices (σ/β, Fisher, Entropy…)
0,08% <uncertainties< 11%
Estimates for timber stocks (commercial, harvestable…)
1% <uncertainties< 6%
S.Guitet al. (2014) Estimating tropical tree diversity indices from forestry surveys: a method to integrate taxonomic uncertainty. Forest Ecology and Management, Volume 328, 270:281.
Geomorphological landscapes and ecosystem services in French Guiana rainforest

7. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Estimating carbon stock in above-ground biomass (AGB) with rapid assessments at large scale (111 transects)
29 botanical plots x 1 ha
(6,349 trees)
111 forestry surveys (20m x 2-3km = 123,906 trees)
Wood density WSGplot=f(vernacular) Monte-Carlo simulations
Diameter
DBHtree=f(DBHclass) Monte-Carlo simulations
Htree=f(DBH)
Exponential sub-model
In a second time, we used the same forestry data to estimate carbon stocks in above ground biomass as an indicator of the main regulation service. We computed aboveground biomass with the widely used pan-tropical allometry proposed by Chave and colleagues and regional sub-model to estimate tree height from diameters. We used the Monte Carlo method previously developed to estimate the wood density which is one of the parameters used in the pan-tropical allometry. We also propagated the uncertainties in diameter measurements using similar approaches.
AGB = f (DBHtree, Htree, WSGplot)
Model 4 - Chave et al 2014
uncertainties< 11%
S.Guitet al. (in review) Spatial structure of above-ground biomass limits accuracy of carbon mapping in rainforest but large scale forest inventories can help to overcome
Geomorphological landscapes and ecosystem services in French Guiana rainforest

8. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Estimating soil organic carbon stock (SOC) with rapid assessments at large scales (445 soil samplings)
24 soil profiles (>1.5m depth)
421 soil cores (1.2m depth)
Pedotransfer functions  mean SOC by WRB class
Random Forest models  Spatial distribution of soil types (WRB)
Model of spatial distribution for SOC
Last of all, we also completed the evaluation of the regulation service by computing soil organic carbon stocks on the forest survey areas. In a first step we developed a spatial model to predict soil types distribution from geomorphological, geological and climatic variables using four hundred soil surveys done on the forest inventories areas. We then estimated the mean carbon stocks for the four main soil types by applying pedotransfert functions on twenty four soil profiles and we computed the total carbon stocks on each forest surveys by combining these two models.
Soil Organic Carbon stocks
uncertainties≈25%
S.Guitet al. (in prep.)
Geomorphological landscapes and ecosystem services in French Guiana rainforest

9. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Potential (119 usable species DBH>55cm)
Actual (13 commercial species DBH>55cm)
a a b c
a ab c b
Number of trees per hectare
PROVISIONING SERVICES : highest timber stocks on tablelands
Effective (4 main harvested sp. DBH>55cm)
Long-term (4 main harvested sp. DBH>20cm)
The four indicators computed for provisioning service were compared between landscapes using test of Tukey with a confidence level of 95%. It showed that timber stocks are significantly higher on tablelands than on other types of geomorphological landscapes. If we consider the hundred and nineteen usable species, the potential of timber production is also lower on plains but this difference is non-significant if we only consider the actual commercial species or the main harvested species.
a ab c b
a a b a
Number of trees per hectare
Geomorphological landscapes and ecosystem services in French Guiana rainforest

10. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Fisher Alpha
Simpson diversity (Alpha Entropy order 2)
a b a a
a b a c
SUPPORTING SERVICES : Richness in mountains, originality in plains
Beta Entropy order 1
Beta Entropy order 2
The four indicators computed for biodiversity as supporting service show that local diversity estimated with Fisher Alpha or with Simpson diversity is significantly higher on mountains than on other type of landscapes whereas plains have significantly higher beta-diversity indices and therefore greatly contribute to the regional diversity because of more original compositions.
a b ab c
a a a b
Geomorphological landscapes and ecosystem services in French Guiana rainforest

11. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
REGULATION SERVICES : Highest carbon stocks in old and stable landscapes
a b c d
a a a b
The two indicators computed for regulation service show the lowest carbon stocks on plains for both soil and above ground biomass. Soil organic carbon stocks are also significantly higher on mountains and tablelands than on multiconvex reliefs.
based on GLM and randomForest
Soil Organic Carbon spatial model
Above-ground biomass spatial model
based on Kriging-regression
Geomorphological landscapes and ecosystem services in French Guiana rainforest

12. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
MULTIVARIATE ANALYSIS BETWEEN LANDSCAPES AT THE TRANSECT LEVEL
Positive correlations between local diversity, carbon stock and production – Negative correlation with originality
High local variability of SE but significant differences between landscapes and reliefs
48% of the variance of SE is explained by the landscapes types (10 classes) – 37% by the reliefs categories (4 classes)
mountains
tablelands
hills
plains
α diversity
β diversity
C stocks
This Principal Component Analysis highlights the relations between indicators and shows that indicators of carbons stocks are negatively correlated with the beta-diversity and positively correlated with indicators of alpha-diversity. On the contrary, indicators of timber provisioning seem to be independent from diversity indices but highly correlated with carbon stock in biomass. The projection of forest surveys on the first axes shows that a high variability exists at the site scale and within landscapes types. However geomorphological classes explain a significant part of the variance: more than one third if we consider the 4 main categories of reliefs and half if we consider the ten precise classes of landscapes represented here.
timber production
Principal Component Analysis (normalized) :
two first axes = 76% of the variance
Geomorphological landscapes and ecosystem services in French Guiana rainforest

13. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Most diverse or most original communities are less attractive for timber production (limitation effect)
Beta-Entropie 1 for originality of composition , Fisher-Alpha for local richness, density of harvestable trees (DBH>55cm) in main commercial species for timber production
The most diverse communities stock more carbon in soil and biomass
Correlation between Carbon stock indices and Fisher-Alpha for the 33 sites (C total - F=13, df=31, p<0.001)
originality
Local richness
More precisely, we can see on bi-variate analyses that the most diverse and the more original compositions correspond generally to the less attractive communities regarding timber provisioning services. We can also see that the correlation between carbon stocks and alpha diversity is highly significant even if we aggregated the forest surveys by sites. The positive correlation between local richness and carbon stock for such high values in hyper-diverse rainforest is quite surprising. One hypothesis is that high diversity may increase the net primary productivity by limited-competition and lead to carbon accumulation in biomass and soils in old-growth forests.
Timber production
Geomorphological landscapes and ecosystem services in French Guiana rainforest

14. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
High diversity and carbon stocks in mountain forests are not due to highest productivity
54 permanent sub-plots (1 – 1,56 ha) at 9 sites with periodic measurements on all trees with DBH>10cm for 4 to 13 years long (GUYAFOR network - size of the points = duration)
To test this hypothesis we compared the forest dynamic between landscapes using an independent network of 54 permanent plots regularly inventoried during the past 4 to 13 years.
We effectively found a significant effect of landscapes on growth rate and especially significant differences between mountains and other landscapes. But in fact, this effect is the opposite than expected. Mountain forests which exhibit the highest diversity and highest carbon stocks have also lower growth rate than the other type of forest.
As a consequence, the relation between carbon stocks and diversity is not due to current productivity but more probably to long-term accumulation of both species and carbon stocks. On mountains the climatic stability during the quaternary was probably favorable for the species diversification as well as for carbon accumulation in soil whereas on lower reliefs like plains and hills especially, species diversity and carbon stocks should have been reduced during the most extreme precipitation changes, few thousand years ago with still visible consequences.
Mortality rate effect : F=33,15 – Df=1 – p<0,001
Landscape effect : F=4,89 – Df=3 – p<0,01 (ANOVA)
Mountains effect : t=-2,915 – p<0,01 (LM)
Tree density effect : F= 20,40 – Df=1 – p<0,001
Landscape effect : F=4,92 – Df=3 – p<0,01 (ANOVA)
Mountains effect : t=-2,076 – p<0,05 (LM)
Geomorphological landscapes and ecosystem services in French Guiana rainforest
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15. 1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
There are important variations of Ecosystem Services at the regional scale in hyper-diverse and old-growth rainforests
CV % for production / % for carbon / % for diversity
Most attractive communities for timber provisioning are neither the most diverse nor the most original ones
If correctly planned, harvesting may have low impact on regional trees diversity
There is a positive correlation between alpha-diversity and carbon stocks in old-growth rainforest
Not due to limited-competition but rather to long-term stability and accumulation
Geomorphological features are efficient indicators to predict these variations
Because they are effective proxy for both inherent soil properties and long-term dynamics
Geomorphological landscapes and ecosystem services in French Guiana rainforest

16. Many thanks for your attention !
1-Context 2-Hypothesis 3-Methods 4-Results 5-Conclusions
Many thanks for your attention !
Other contributors : P. Couteron, D. Sabatier, B. Hérault, O. Brunaux
Fundings : European Union (PO-FEDER), French Minister for Environment (ECOTROP)
Geomorphological landscapes and ecosystem services in French Guiana rainforest