Evaluation of sensitivity of soil respiration to temperature in different forest types and developmental stages of maturity using the incubation method

To calculate and predict soil carbon budget and cycle, it is important to understand the complex interrelationships involvedin soil respiration rate (Rs). We attempted to reveal relationships between Rs and key environmental factors, suchas soil temperature, using a laboratory incubation method. Soil samples were collected from mature deciduous (MD),mature coniferous (MC), immature deciduous (ID), and immature coniferous (IC) forests. Prior to measure, soils werepre-incubated for 3 days at 25°C and 60% of maximum water holding capacity (WHC). Samples of gasses were collectedwith 0, 2, and 4 h interval after the beginning of the measurement at soil temperatures of 5, 15, 25, and 35°C (at 60% WHC).Air samples were collected using a syringe attached to the cap of closed bottles that contained the soil samples. The CO2concentration of each gas sample was measured by gas chromatography. Rs was strongly correlated with soil temperature(r, 0.93 to 0.96; P < 0.001). For MD, MC, ID, and IC soils taken from 0-5 cm below the surface, exponential functionsexplained 90%, 82%, 92%, and 86% of the respective data plots. The temperature and Rs data for soil taken from 5-10 cmbeneath the surface at MD, MC, ID, and IC sites also closely fit exponential functions, with 83%, 95%, 87%, and 89% ofthe data points, respectively, fitting an exponential curve. The soil organic content in mature forests was significantlyhigher than in soils from immature forests (P < 0.001 at 0-5 cm and P < 0.005 at 5-10 cm) and surface layer (P = 0.04 at0-5 cm and P = 0.12). High soil organic matter content is clearly associated with high Rs, especially in the surface layer.We determined that the incubation method used in this study have the possibility for comprehending complex characteristicof Rs.