Table 1 The association of environmental conditions and the variation in the tree species composition of Amazonian forests

From: The biogeography of the Amazonian tree flora

Rank	Environmental predictor	R²	AdjR²_Cum	F	AIC
RDA Model 1: [PCoA axis 1] ~ 14 environmental predictors
1	Soil base cation concentration (SB)	0.27	0.27	764.6	-6438.3
2	Temperature seasonality	0.09	0.36	280.2	-6699.1
3	Podzol	0.04	0.4	122.7	-6816.5
4	Elevation (ALOS_3D)	0.03	0.42	86	-6898.9
5	Maximum climatological water deficit (MCWD)	0.01	0.44	47.4	-6943.8
6	Soil pH	0.01	0.45	44.1	-6985.6
7	Precipitation seasonality	0.01	0.45	26.2	-7009.7
8	Total annual rainfall	0	0.46	13.2	-7020.9
9	Mean annual temperature	0	0.46	13.3	-7032.3
10	Flooded	0	0.46	13.1	-7043.3
11	Topographic diversity (TopoDiver)	0	0.47	8.1	-7049.4
12	Groundwater table depth (WTD)	0	0.47	3.7	-7051.1
13	Multi-scale topographic index (MTPI)	0	0.47	5.8	-7054.9
14	Temperature range	Forward selection procedure stopped (not selected)
RDA Model 2: [PCoA axis 2] ~ 14 environmental predictors
1	Flooded	0.42	0.42	1450.4	-6988.9
2	Podzol	0.01	0.43	39.9	-7026.5
3	Topographic diversity (TopoDiver)	0.01	0.44	44	-7068.1
4	Precipitation seasonality	0.01	0.45	40.8	-7106.6
5	Soil base cation concentration (SB)	0.01	0.46	21.4	-7126
6	Mean annual temperature	0.01	0.46	26.9	-7150.8
7	Temperature range	0	0.47	14.9	-7163.7
8	Elevation (ALOS_3D)	0	0.47	25.9	-7187.5
9	Maximum climatological water deficit (MCWD)	0	0.48	7.3	-7192.9
10 to 14	Multi-scale topographic index (MTPI), soil pH, temperature seasonality, total annual rainfall, groundwater table depth (WTD)	Forward selection procedure stopped (not selected)
RDA Model 3: [PCoA axis 1: PCoA axis 2] ~ 14 environmental predictors
1	Flooded	0.21	0.21	470.9	-4694.5
2	Soil base cation concentration (SB)	0.18	0.39	520.2	-5149.5
3	Maximum climatological water deficit (MCWD)	0.04	0.43	132.5	-5275.6
4	Podzol	0.03	0.46	88.4	-5360.1
5	Soil pH	0.02	0.48	69.8	-5426.8
6	Precipitation seasonality	0.01	0.48	17.5	-5442.3
7	Temperature range	0.01	0.49	17.9	-5458.2
8	Mean annual temperature	0.00	0.49	14.9	-5471.1
9	Topographic diversity (TopoDiver)	0.00	0.49	10.1	-5479.3
10	Elevation (ALOS_3D)	0.00	0.50	13.4	-5490.7
11 to 14	Total annual rainfall, temperature seasonality, multi-scale topographic index (MTPI), groundwater table depth (WTD)	Forward selection procedure stopped (not selected)
RDA Model 4: residuals[RDA model: [PCoA axis 1:PCoA axis 2] ~ 93 MEMs] ~ 14 environmental predictors
1	Flooded	0.094	0.09	209.4	-6171.3
2	Soil base cation concentration (SB)	0.047	0.14	110.8	-6277.4
3	Podzol	0.016	0.16	39.3	-6314.4
4	Temperature range	0.005	0.16	13.2	-6325.6
5	Elevation (ALOS_3D)	0.002	0.16	3.1	-6326.7
6	Mean annual temperature	0.001	0.16	3.8	-6328.5
7 to 14	Temperature seasonality, total annual rainfall, precipitation seasonality, maximum climatological water deficit (MCWD), topographic diversity (TopoDiver), multi-scale topographic index (MTPI), soil pH, groundwater table depth (WTD)	Forward selection procedure stopped (not selected)

The results of RDA models relating PCoA scores and 14 environmental predictors. The first model adjusts only the PCoA axis 1, the second model adjusts only the PCoA axis 2, the third model adjusts both PCoA axis at once, and the fourth mode uses the residuals of the RDA model relating the PCoA scores and the spatial predictors (93 selected Moran’s Eigenvector Maps MEMs) to adjust the 14 environmental predictors. PCoA axes scores were obtained from the pair-wise Bray–Curtis dissimilarities among 2,023 forest-inventory plots. Predictors are ordered from lowest to highest AIC. The R² and F statistics were estimated using permutation tests under a forward selection procedure.

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Table 1 The association of environmental conditions and the variation in the tree species composition of Amazonian forests

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