3.2 Carbon, nitrogen, phosphorus content and stoichiometry of plant and soil
Fig. 3 Content and stoichiometric characteristics of organic carbon, total nitrogen, and total phosphorus in plant root and shoot fractions and rhizosphere soils with different gravel contents. Error bars refer to standard deviation Different lowercase letters indicate significant differences among different gravel soils (p<0.05).
As shown in Fig. 3, OC, TN, TP, C: N, C:P, and N:P of different soils have significant differences(p<0.05). TP of shoot, root and rhizosphere decreased in the order of low˃medium˃high gravel content; TN was larger for low than for medium and high gravel contents; organic carbon content showed no significant difference among different gravel soils (p˃0.05). C:N of rhizosphere soil was larger for high than for medium and low gravel contents; TP of shoot and root fractions decreased in the order of high˃medium˃low gravel content; N:P of shoot and root fractions was larger for high than for medium and low gravel contents.
Fig. 4. Content and stoichiometric characteristics of organic carbon, total nitrogen, and total phosphorus in plant root and aboveground fractions and rhizosphere soils for different plant species. Error bars refer to standard deviation; respectively. Different lowercase letters indicate significant differences among different plant species (p<0.05). Fe, Festuca elata ; Ed, Elymus dahuricus ; Ms, Medicago sativa ; Fe+Ed, Festuca elata plus Elymus dahuricus ; Fe+Ms, Festuca elata plus Medicago sativa ; Ms+Ed, Medicago sativa plus Elymus dahuricus ;Fe+Ms+Ed,Festuca elata plus Medicago sativa plus Elymus dahuricus .
Fig. 4 illustrates the contents and stoichiometric characteristics of OC, TN and TP of plant shoot, root fractions and rhizosphere soils among different plant species. For plant shoot fraction, TN content was the largest and the lowest for Ms (30.76 g kg-1) and Fe (11.40 g kg-1), respectively; TP content of Ed (2.23g kg-1), Ms (2.13g kg-1), Fe+Ed (2.19g kg-1),Fe+Ms (1.81g kg-1), Ed+Ms (1.92g kg-1) were significantly larger than that of Fe(1.57g kg-1) and Fe+Ed+Ms (1.55g kg-1); OC content was the lowest for Ms+Ed(422.99 g kg-1) among plant species. C:N was significantly different (p<0.05), while C:P was not statistically significant (p˃0.05). N:P of Ms (14.71g kg-1) and Ms+Ed (14.01g kg-1) was significantly higher than that of Fe (7.42g kg-1) and Fe+Ed (8.21g kg-1). For plant root fraction, TN, TP, C: N, C:P and N:P had significant differences(p<0.05), among which the OC content of Ms(468.35 g kg-1) and Fe+Ms (469.38g kg-1) was larger than that of Fe (406.33g kg-1) and Fe+Ms+Ed (408.22g kg-1). The OC, TP, C:N and C:P of rhizosphere soils showed no significant differences among plant species exceptFe+Ms .