3.3 Linkage between plant traits with rhizosphere and soil properties
Correlation analysis indicated (Table 3) that all plant traits were positively correlated with soil organic carbon (r=0.69~0.76, p<0.05), and C:P (r=0.72~0.85, p<0.05) and total porosity (r=0.78~0.91, p<0.05); and negatively correlated with bulk density (r=-0.96~-0.88, p<0.01). Among these plant traits, shoot and total biomass were positively correlated with total nitrogen (r=0.71 and 0.69, p<0.05). In addition, all plant traits were positively correlated with rhizosphere total nitrogen (r=0.81~0.96, p<0.01), and total phosphorus (r=0.70~0.89, p<0.05) and N:P (r=0.71~0.93, p<0.05); and negatively correlated with C:N (r=-0.68~-0.85, p<0.05). Plant height, shoot and total biomass were positively correlated with rhizosphere organic carbon (r=0.71 and 0.69, p<0.05).
Table3 Pearson correlation coefficients between plant growth indices with non-rhizosphere and rhizosphere soil properties (n = 9)
Root organic carbon, C:N,C:P were positively correlated with soil organic carbon, and C:N (r= 0.67~0.78, p<0.05); total nitrogen (TN), and total phosphorus (TP) were positively correlated with total porosity (r=0.73 and 0.67, p<0.05); N:P was positively correlated with bulk density and pH (r=0.72 and 0.78, p<0.05). There was a significant positive correlation between C:P, bulk density, pH and soil C:N (r=0.77, 0.78, 0.72 and 0.82, p<0.05); TP was negatively correlated with soil C:N (r=0.80, p<0.01), were positively correlated with C:P,N: P (r=-0.68 and 0.68, p<0.05).
Root total phosphorus was positively correlated with rhizosphere total nitrogen (r=0.67, p<0.05); root total nitrogen and total phosphorus were positively correlated with total phosphorus (r=0.83 and 0.93, p<0.01); root C:P was negatively correlated with total phosphorus (r=-0.91, p<0.01); root total phosphorus was positively correlated with rhizosphere soil organic carbon (r=0.72, p<0.05), root organic carbon, C:N, C:P and N:P were negatively correlated with rhizosphere organic carbon (r=-0.92~ -0.72, p<0.05); root total nitrogen and total phosphorus was positively correlated with C:N (r=0.96 and 0.83, p<0.01), and root C:P was negatively correlated with C:N (r=0.80, p<0.05); root C:P and N:P were positively correlated with C:P (r=0.74 and 0.98, p<0.05); N:P was positively correlated with root N:P (r=0.73, p<0.05).
There was a significant positive correlation between shoot total nitrogen and organic carbon and rhizosphere total nitrogen (r=0.73 and 0.82, p<0.05); shoot total nitrogen and total phosphorus positively correlated with (r=0.88 and 0.86, p<0.01), and shoot C:N,C:P was a negative correlation with total phosphorus (r=-0.93 and -0.78, p<0.05); shoot total phosphorus and total phosphorus was positively correlated with (r=0.68 and 0.86, p<0.05), and shoot C:P and N:P were negatively correlated with rhizosphere soil organic carbon (r=-0.86 and -0.75, p<0.05); shoot total nitrogen and phosphorus was positively correlated with C:N (r=0.82 and 0.69, p<0.01), and shoot C:N was negatively correlated with C:N (r=-0.96, p<0.01); shoot C:P and N:P was positively correlated with C:P (r=0.76 and 0.76, p<0.05), and shoot total phosphorus was significantly negatively correlated with (r=-0.78, p<0.05).
Fig. 5 RDA of the relationships among plant traits, soil properties, and their stoichiometric characteristics for different plant species. TN, soil total nitrogen; TP, soil total phosphorus; SOC, soil organic carbon;S-C/N, soil C/N ratio; S-C/P, soil C/P ratio; S-N/P, soil N/P ratio; PH, soil pH; BD, bulk density; e , total porosity; PTN, plant total nitrogen; PTP, plant total phosphorus; POC, plant organic carbon; P-C/N, plant C/N ratio; P-C/P, plant C/P ratio; P-N/P, plant N/P ratio; RTN, root total nitrogen; RTP, root total phosphorus; ROC, root organic carbon; R-C/N, root C/N ratio; R-C/P, root C/P ratio; R-N/P, root N/P ratio; H, Plant height; Tc, total coverage; Ab, aboveground biomass; Rb, root biomass; B, total biomass.
RDA shows that the accumulation of the first two axes in different plant growth indexes (>93%) (Fig. 5). The changes of plant trait properties (Ms , Ed+Ms , Fe+Ed+Ms ) were mainly explained by the first axis, and those of other plants were mainly determined by the second axis. Bulk density is negatively correlated with Fe , Fe+Ed , Ed , Fe+ Ms , Fe+Ed+Ms(r=-0.99~0.69, p<0.05), and positively correlated with Ms ,Ed+Ms (r=0.89 and 0.96, p<0.01); total porosity was positively correlated withFe , Ed , Fe+Ed , Fe+ Ms , Fe+Ed+Ms(r=0.91,0.79,0.95,0.93 and 0.73, p<0.05); TN and SOC were positively correlated with Fe , Fe+Ed , Fe+Ms(r=0.74,0.92,0.76; r=0.75,0.80,0.79, p<0.05); TP and N:P were positively correlated with Fe+Ed (r=0.77 and 0.80, p<0.05). Bulk density is positively correlated withFe+Ed (r=0.71, p<0.05), total porosity was significantly negatively correlated with Ms and Ed+Ms(r=-0.91 and -0.81 p<0.05); Ms was positively correlated with TN (r=0.97, p<0.05)and negatively with TN, TP, SOC and N:P (r=-0.92~0.74, , p<0.05);Ed+Ms had negative correlations with TN, TP, SOC, and N:P (r=-0.91~-0.70, p<0.05); Fe+Ed+Ms was negatively correlated with TN and N:P (r=-0.84,-0.83, p<0.05), and positively correlated with C:N (r=0.70, p<0.05)