Density reduction in loblolly pine (Pinus taeda L.) stands to increase tree C assimilation: an approach with the dual δ13C and δ18O isotope signatures in needles

Table 4 Effect of planting density and thinning intensity (indicated by p values) on specific leaf area, foliar N content, foliar δ¹³C, and δ¹⁸O in loblolly pine (Pinus taeda L.) trees

Fixed factors	Planting density				Thinning treatments
Fixed factors	Planting density				Initial density of 1111 stems ha⁻¹	Initial density of 1729 stems ha⁻¹	Initial density of 1729 stems ha⁻¹	Two different initial densities
	2964 vs 494	2964 vs 1111	2964 vs 1729	2964 vs 2346	No-thinning vs moderate thinning (55% density removal)	No-thinning vs light thinning (36% density removal)	No-thinning vs heavy thinning (71% density removal)	Moderate thinning at 1111 trees ha⁻¹ vs heavy thinning at 1729 trees ha⁻¹
Specific leaf area (cm² gm⁻¹)	0.021	0.383	0.463	0.423	0.629	0.099	0.043	0.737
Foliar N content (g m⁻²)	0.681	0.985	0.099	0.604	0.373	0.844	0.165	0.597
δ¹³C	0.452	0.929	0.903	0.143	0.102	0.578	0.042	0.313
δ¹⁸O	0.025	0.543	0.650	0.940	0.059	0.583	0.002	0.192

Note. The effects of planting density and thinning intensity were analyzed separately as the thinning treatments were applied in two planting density treatments. The three sites were treated as random effects in the model

ISSN: 1297-966X