Nitrogen fixation rate of Acacia mangium Wild at mid rotation in Brazil is higher in mixed plantations with Eucalyptus grandis Hill ex Maiden than in monocultures

Table 3 Allometric equations of the N content in above-ground tree compartments for Acacia mangium in the monoculture (100A) and the mixed stand (50E:50A–Acacia) and for Eucalyptus grandis in the monoculture (100E) and the mixed stand (50E:50A–Eucalyptus), at 39 months after planting

Treatment	Compartment	Model	R ²	RMSE	n
100A	Leaves	NC = −21.569 + 958.799 × CBH²	0.930	11.025	22
	Branches	NC = −9.932 + 347.379 × CBH²	0.813	6.620	23
	Bark	NC = − 6.984 + 278.289 × CBH²	0.911	3.633	22
	Wood	NC = − 1.912 + 226.421 × CBH²	0.962	1.902	21
100E	Leaves	NC = 466.196 × CBH²	0.919	8.556	10
	Branches	NC = 200.301 × CBH²	0.896	4.368	9
	Bark	NC = 99.924 × (DBH² × Ht)	0.864	4.947	9
	Wood	NC = 343.156 × CBH²	0.955	4.611	10
50E:50A–Acacia	Leaves	NC = − 10.827 + 669.620 × CBH²	0.954	4.279	23
	Branches	NC = − 3.566 + 224.583 × CBH²	0.896	2.324	21
	Bark	NC = − 4.152 + 226.401 × CBH²	0.932	1.873	18
	Wood	NC = − 2.235 + 227.968 × CBH²	0.928	1.838	20
50E:50A–Eucalyptus	Leaves	NC = 767.453 × CBH²	0.960	11.034	10
	Branches	NC = − 24.394 + 298.559 × CBH²	0.953	4.691	9
	Bark	NC = 32.459 × (DBH² × Ht)	0.788	2.275	8
	Wood	NC = 32.319 + 88.979 × (DBH² × Ht)	0.879	3.529	9

NC N content in g tree⁻¹, CBH circumference at breast height in m, DBH diameter at breast height in m, Ht tree height in m. RMSE root-mean-square error, n: number of sample used to fit the model. All the regressions were significant (p < 0.001, except for bark for 50E:50A–Eucalyptus: p = 0.011)

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