Experimental throughfall reduction barely affects soil carbon dynamics in a warm-temperate oak forest, central China

Area of Science:

• Forest ecology
• Soil science
• Biogeochemistry

Background:

• Changing precipitation patterns significantly influence forest soil carbon (C) cycling.
• Understanding forest ecosystem responses to altered precipitation is crucial for predicting future carbon dynamics.

Purpose of the Study:

• To investigate the effects of reduced precipitation on soil respiration (total, heterotrophic, and autotrophic), soil microbial biomass, and fine root biomass in a Chinese oak forest.
• To determine the impact of a simulated ~30% annual precipitation reduction on key soil C cycling processes.

Main Methods:

• A throughfall reduction (TFR) experiment was implemented using rain-out shelters to exclude ~50% of throughfall during the growing season (May-September) from 2013 to 2016.
• Measurements included total soil respiration (SR), heterotrophic soil respiration (HR), autotrophic soil respiration (AR), soil microbial biomass, and fine root biomass.
• Soil moisture was monitored to assess treatment effects.

Main Results:

• Reduced soil moisture during TFR did not affect microbial biomass or heterotrophic soil respiration.
• Total soil respiration, autotrophic soil respiration, and fine root biomass increased during TFR only in a naturally dry year; they were unaffected in other years.
• Annual rates of SR, HR, and AR remained unaffected by the TFR treatment over the study period.

Conclusions:

• Mild, consistent reductions in growing season precipitation do not significantly alter soil organic matter decomposition in this oak forest ecosystem.
• The studied forest ecosystem demonstrated resilience to moderate precipitation reduction, with responses observed only under naturally severe drought conditions.
• A soil moisture threshold of approximately 10 vol% was identified as critical for regulating soil respiration in this soil type.