Data from: Contrasting responses of phosphatase kinetic parameters to nitrogen and phosphorus additions in forest soils

1. Global changes include increasing nitrogen (N) and phosphorus (P)
deposition, which affect microbial nutrient demand and biogeochemical
cycles. The responses of P-mineralizing enzymes to these global change
components are poorly defined and are not specified in forest soils
differing in P content. 2. We chose one site in a P-rich and two sites in
P-poor forests and established sixteen 20 × 20 m plots at each site.
Control, either N only, P only, or combined N and P, were randomly
distributed through each forest site with 4 replicates. We investigated
the effects of N and P additions over four years on the
phosphomonoesterase potential activity (Vmax), its half-saturation
constant (Km), and its catalytic efficiency (Vmax/Km). 3. Without N and P
additions, the enzyme kinetic parameters Vmax, Km, and Vmax/Km were higher
in P-rich than in P-poor forest soils. These parameters increased with
soil pH, SOC, TN, and TP contents increased. 4. Remarkably, P additions
caused the Vmax and Km to increase in P-rich soils, but had no effect on
Vmax/Km. P additions to P-poor soils resulted in a decrease in the Vmax/Km
via the inhibitory effects of inorganic P on the Vmax. N additions had no
effect on the Vmax/Km in P-rich and P-poor soils because of the similar
increases in the Vmax and Km. The effects of combined N and P and P only
additions to P-poor soils on the Vmax and Km were similar, but were
stronger than the effects of N only or P only additions on the P-rich
soils. 5. Phosphatase kinetic parameters were positively related to the
availability of N and P in P-rich soils, but inorganic P inhibited
phosphatase activity and caused a decrease in the catalytic efficiency in
P-poor soils. More microbial community groups could contribute to the
secretion of a broader spectrum of iso-enzymes under combined additions of
N and P in P-rich soils. We conclude contrast responses of phosphatase
kinetics to P and N inputs in P-rich and P-poor forest soils, while
long-term N deposition might mitigate P limitation by increasing
phosphatase secretion.