Response of Soil Respiration to Soil Temperature and Moisture in a 50-Year-Old Oriental Arborvitae Plantation in China

Xinxiao Yu,Xiaoping Wang,Guodong Jia,Hailong Wu,Chunping Li,Xizhi Li,Jixin Cao,Tianshan Zha,Zhuo Pang,Bin Wu,Guopeng Chen,Jack Anthony Gilbert

doi:10.1371/journal.pone.0028397

Abstract

China possesses large areas of plantation forests which take up great quantities of carbon. However, studies on soil respiration in these plantation forests are rather scarce and their soil carbon flux remains an uncertainty. In this study, we used an automatic chamber system to measure soil surface flux of a 50-year-old mature plantation of Platycladus orientalis at Jiufeng Mountain, Beijing, China. Mean daily soil respiration rates (Rs) ranged from 0.09 to 4.87 µmol CO2 m−2s−1, with the highest values observed in August and the lowest in the winter months. A logistic model gave the best fit to the relationship between hourly Rs and soil temperature (Ts), explaining 82% of the variation in Rs over the annual cycle. The annual total of soil respiration estimated from the logistic model was 645±5 g C m−2 year−1. The performance of the logistic model was poorest during periods of high soil temperature or low soil volumetric water content (VWC), which limits the model's ability to predict the seasonal dynamics of Rs. The logistic model will potentially overestimate Rs at high Ts and low VWC. Seasonally, Rs increased significantly and linearly with increasing VWC in May and July, in which VWC was low. In the months from August to November, inclusive, in which VWC was not limiting, Rs showed a positively exponential relationship with Ts. The seasonal sensitivity of soil respiration to Ts (Q10) ranged from 0.76 in May to 4.38 in October. It was suggested that soil temperature was the main determinant of soil respiration when soil water was not limiting.

Highlights

Forests store,45% of terrestrial carbon and are important components of the global carbon cycle
Pinus tabulaeformis in China’s eastern part of Loess Plateau [21], 3.4–5.6 in a temperate mixed hardwood forest [26], 4.1 for Despite seasonal differences in the control of Ts and volumetric water content (VWC) over Rs, both temperature-only quadratic and logistic models accounted for 82% of the variation in hourly Rs
The quadratic equation well fitted the data in measurement time period and expressed the dynamics of soil respiration at high temperature better than logistic model (Fig. 3), it did not fit the low-temperature data well and would potentially overestimate soil respiration at low temperature (Fig. 2)

Summary

Introduction

Forests store ,45% of terrestrial carbon and are important components of the global carbon cycle. They absorb ,30% of anthropogenic carbon emission from fossil fuel combustion and land-use change every year [1]. Understanding the carbon dynamics of soil respiration in different forest ecosystems and their responses to climatic factors is critical for estimating the future global carbon budget. Soil respiration is often related to soil temperature [7], or soil temperature and soil water content [8], [9]. Low soil water content limits respiration by limiting microbial contact with available substrate and by causing dormancy and/or death of microorganisms [10]. Many studies have been done to quantify the soil respiration of different ecosystems and to understand the responses of respiration to environmental variables [6], [11], [12], [13], [14], [15]

Methods

Results

Conclusion