3.4. Linkages between soil CNP stoichiometry and enzyme
stoichiometry
There was a negative linear
correlation between enzyme C: N ratio and soil C: N ratio in 0-20 and
20-40 cm soil layers (p < 0.01), but a positive linear
correlation in 40-60 cm soil layers (p < 0.05) (Fig.
3). Enzyme C: P ratio had a negative linear correlation with soil C: P
ratio in 0-20 and 40-60 cm soil layers (p < 0.01), but
a positive linear correlation in 20-40 cm soil layer (p< 0.01). Enzyme N: P ratio had a negative linear correlation
with soil N: P ratio in 0-20 cm soil layer (p < 0.01),
but a positive linear correlation in 20-40 and 40-60 cm soil layers
(p < 0.01).
In AG (Fig. 4a), RDA analysis showed that enzyme activity (βG, NAG, and
ACP) and enzyme stoichiometry (enzyme C: P and N: P ratio) were mainly
associated with soil nutrient
elements (TC, TN, TP, SOC, NH4+-N,
NO3--N, and AP,
positively) and soil stoichiometry
(soil C: N and C: P ratio,
negatively). Among them, TP and
NH4+-N had significant effects on
biological factors (p < 0.01), indicating that they
were the main factors driving AG enzyme activity and enzyme
stoichiometry variation. In WM (Fig. 4b), RDA analysis showed that
enzyme activity (βG and NAG) and enzyme stoichiometry (enzyme C: P and
N: P ratio) were mainly related to soil nutrient elements (TN, TP, SOC,
NH4+-N,
NO3--N, and AP, positively) and soil
stoichiometry (soil C: N, C: P, and N:P ratio, negatively). Among them,
TP and WSA (2-1 mm) had significant effects on biological factors
(p < 0.01). In PC (Fig. 4c), RDA analysis showed that
enzyme activity (βG, NAG, and ACP) and enzyme stoichiometry (enzyme C: P
and N: P ratio) were mainly related to soil nutrient elements (TC, TN,
TP, SOC, NH4+-N,
NO3--N, and AP, positively) and soil
stoichiometry (soil C:P and N:P ratio, positively). Among them,
NO3--N had significant effects on
biological factors (p < 0.01). Meanwhile, the enzyme
C:P and N:P ratios were negatively associated with enzyme C:N ratios in
all land use patterns.
4. Discussion