Table 1.

Characterization of carbon and nitrogen contents of the gravel plain non-vegetated (NV) soil, speargrasses rhizosheath (RS) and rhizosphere (RH); values are expressed as mean of three replicates ± standard deviation.

Variable	Unit	ANOVA (p)	NV	RH	RS
Organic matter	%	0.0008	0.066 ± 0.002 (a)	2.869 ± 0.723 (b)	0.140 ± 0.076 (a)
Total C	µg/mg	<0.0001	2.030 ± 0429 (a)	17.185 ± 2.962 (b)	2.199 ± 0.886 (a)
POC	µg/mg	0.0008	0.332 ± 0.010 (a)	14.344 ± 3.616 (b)	0.698 ± 0.382 (a)
PIC	µg/mg	0.0197	1.698 ± 0.421 (a)	2.842 ± 2.130 (b)	1.502 ± 0.622 (ab)
Total N	µg/mg	0.0021	0.038 ± 0.100 (a)	0.418 ± 0.100 (b)	0.056 ± 0.021 (a)
PON	µg/mg	0.0074	0.043 ± 0.002 (a)	0.357 ± 0.099 (b)	0.056 ± 0.018 (a)
PIN	µg/mg	<0.0001	0.005 ± 0.004 (a)	0.0611 ± 0.008 (b)	0.0006 ± 0.002 (a)

Results of ANOVA tests are reported (p value); different letters indicate the significant difference across samples (Tukey’s multiple comparisons test, p < 0.05). The other physicochemical parameters measured are listed in Supplementary Table S4.

POC particulate organic carbon, PIC particulate inorganic carbon, PON particulate organic nitrogen, PIN particulate inorganic nitrogen, NV non vegetated, RH rhizosphere, RS rhizosheath.