Quantifying Components of Soil Respiration and Their Response to Abiotic Factors in Two Typical Subtropical Forest Stands, Southwest China

<div><p>Separating the components of soil respiration and understanding the roles of abiotic factors at a temporal scale among different forest types are critical issues in forest ecosystem carbon cycling. This study quantified the proportions of autotrophic (<i>R</i>_A) and heterotrophic (<i>R</i>_H) in total soil (<i>R</i>_T) respiration using trenching and litter removal. Field studies were conducted in two typical subtropical forest stands (broadleaf and needle leaf mixed forest; bamboo forest) at Jinyun Mountain, near the Three Georges Reservoir in southwest China, during the growing season (Apr.–Sep.) from 2010 to 2012. The effects of air temperature (AT), soil temperature (ST) and soil moisture (SM) at 6cm depth, solar radiation (SR), pH on components of soil respiration were analyzed. Results show that: 1) SR, AT, and ST exhibited a similar temporal trend. The observed abiotic factors showed slight interannual variability for the two forest stands. 2) The contributions of <i>R</i>_H and <i>R</i>_A to <i>R</i>_T for broadleaf and needle leaf mixed forest were 73.25% and 26.75%, respectively, while those for bamboo forest were 89.02% and 10.98%, respectively; soil respiration peaked from June to July. In both stands, CO₂ released from the decomposition of soil organic matter (SOM), the strongest contributor to <i>R</i>_T, accounted for over 63% of <i>R</i>_H. 3) AT and ST were significantly positively correlated with <i>R</i>_T and its components (<i>p</i><0.05), and were major factors affecting soil respiration. 4) Components of soil respiration were significantly different between two forest stands (<i>p</i><0.05), indicating that vegetation types played a role in soil respiration and its components.</p></div

Analysis of the differences of the same component respiration of the two forests using analysis of variance (ANOVA).

<p>Analysis of the differences of the same component respiration of the two forests using analysis of variance (ANOVA).</p

Components of soil respiration and ratios of their contributions to total soil respiration in the two forest stands.

<p>Components of soil respiration and ratios of their contributions to total soil respiration in the two forest stands.</p

The relationship between air temperature and total soil respiration, heterotrophic respiration and autotrophic respiration, for the two forest stands.

<p>The relationship between air temperature and total soil respiration, heterotrophic respiration and autotrophic respiration, for the two forest stands.</p

The dynamic variation of the monthly average values of total soil respiration, heterotrophic respiration and autotrophic respiration for the two forest stands.

<p>The dynamic variation of the monthly average values of total soil respiration, heterotrophic respiration and autotrophic respiration for the two forest stands.</p

The dynamic variation of monthly average values of abiotic environmental factors of the two forest stands.

<p>The dynamic variation of monthly average values of abiotic environmental factors of the two forest stands.</p

The relationship between soil temperature and total soil respiration, heterotrophic respiration and autotrophic respiration, respectively, for the two forest stands.

<p>The relationship between soil temperature and total soil respiration, heterotrophic respiration and autotrophic respiration, respectively, for the two forest stands.</p

The relationship between soil organic matter and both air and soil temperatures for the two forest stands.

<p>The relationship between soil organic matter and both air and soil temperatures for the two forest stands.</p

Experimental treatments.

<p>Experimental treatments.</p

Yield, biomass and water use efficiency (WUE) of cultivar mixture cropping treatments and pure stands of winter wheat as well as the mid-parent superiority (MS) and better-parent superiority (BS) of mixture stands under one time irrigation (W1) and two times irrigation (W2) conditions in 2009/2010.

<p>Yield, biomass and water use efficiency (WUE) of cultivar mixture cropping treatments and pure stands of winter wheat as well as the mid-parent superiority (MS) and better-parent superiority (BS) of mixture stands under one time irrigation (W1) and two times irrigation (W2) conditions in 2009/2010.</p