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

Abstract

Abstract1. 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 four replicates. We investigated the effects of N and P additions over 4 years on the phosphomonoesterase potential activity (V max ), its half-saturation constant (K m ) and its catalytic efficiency (V max /K m ).3. Without N and P additions, the enzyme kinetic parameters V max , K m and V max /K m 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 V max and K m to increase in P-rich soils, but had no effect on V max /K m . P additions to P-poor soils resulted in a decrease in the V max /K m via the inhibitory effects of inorganic P on the V max . N additions had no effect on the V max /K m in P-rich and P-poor soils because of the similar increases in the V max and K m . The effects of combined N and P and P only additions to P-poor soils on the V max and K m 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.

Land Subsidence in a Coal Mining Area Reduced Soil Fertility and Led to Soil Degradation in Arid and Semi-Arid Regions

“…Soil organic carbon (SOC) was measured using the colorimetric method after digestion with K 2 Cr 2 O 7 /H 2 SO 4 at 165 °C in an oil bath [28]. Water-extractable dissolved organic carbon (DOC) was extracted with distilled water (1:5 v:v) and measured with a TOC (total dissolved organic) analyzer (Liqui TOC II, Elementar, Germany) [29]. The semimicro Kjeldahl method was used for the determination of total nitrogen (TN).…”

Functional traits along a transect

“…Zhang, Yang, et al. () compared phosphatase activity in different forests and revealed the diverse responses to experimental soil nutrient addition. These studies established a link between soil microbes or enzymes with soil functions, providing insights into responses of soil microbial diversity to both climate and soil factors.…”

Rhizosphere Soil Microbial Properties on Tetraena mongolica in the Arid and Semi-Arid Regions, China

“…A conductivity meter was used to measure the soil electrical conductivity (EC) of the air-dried samples. Soil water content (SWC) was determined by drying soil samples at 105 °C for 24 h. The total nitrogen (TN) was determined by the Kjeldahl method [ 16 ]. The level of available phosphorus (AP) in the soil was determined by the molybdenum-blue method.…”