Seasonality, Rather than Nutrient Addition or Vegetation Types, Influenced Short-Term Temperature Sensitivity of Soil Organic Carbon Decomposition

Abstract

The response of microbial respiration from soil organic carbon (SOC) decomposition to environmental changes plays a key role in predicting future trends of atmospheric CO2 concentration. However, it remains uncertain whether there is a universal trend in the response of microbial respiration to increased temperature and nutrient addition among different vegetation types. In this study, soils were sampled in spring, summer, autumn and winter from five dominant vegetation types, including pine, larch and birch forest, shrubland, and grassland, in the Saihanba area of northern China. Soil samples from each season were incubated at 1, 10, and 20°C for 5 to 7 days. Nitrogen (N; 0.035 mM as NH4NO3) and phosphorus (P; 0.03 mM as P2O5) were added to soil samples, and the responses of soil microbial respiration to increased temperature and nutrient addition were determined. We found a universal trend that soil microbial respiration increased with increased temperature regardless of sampling season or vegetation type. The temperature sensitivity (indicated by Q10, the increase in respiration rate with a 10°C increase in temperature) of microbial respiration was higher in spring and autumn than in summer and winter, irrespective of vegetation type. The Q10 was significantly positively correlated with microbial biomass and the fungal: bacterial ratio. Microbial respiration (or Q10) did not significantly respond to N or P addition. Our results suggest that short-term nutrient input might not change the SOC decomposition rate or its temperature sensitivity, whereas increased temperature might significantly enhance SOC decomposition in spring and autumn, compared with winter and summer.

Phosphorus rather than nitrogen enhances CO2 emissions in tropical forest soils: Evidence from a laboratory incubation study

“…Tian et al (2016) demonstrated that N addition does not influence soil microbial CO 2 emission from a topsoil in a laboratory incubation. Several field studies also reported lower soil microbial CO 2 emissions with N addition compared to controls due to changes in microbial composition (Bowden, Davidson, Savage, Arabia, & Steudler, 2004;Mo et al, 2008;Phillips & Fahey, 2007;Qian et al, 2016;, but here no changes were observed. The response of CO 2 emission to N addition might also be related to soil C substrate availability.…”

“…Our result is supported by some previous studies. For example, Mori et al (2016) found that CO 2 emission rates in tropical forest soils were stimulated by P addition at high C concentrations (1 mg C/g soil was added as glucose) but not at low C conditions (0.1 mg g −1 soil), whereas Qian et al (2016) reported that there was no response of soil microbial CO 2 emission to P addition. Indeed, in this study, the EV-RT soil in Puerto Rico with the highest C content (7.21%) showed the strongest response to P addition among the four soils.…”

“…Nutrient availability may regulate microbial physiology and activity and eventually influence ecosystem C cycling (Jing et al, 2017;Mackenzie, Ver, & Lerman, 2002). However, although many fertilization experiments have been conducted in the field, there are limited studies on soil microbial CO 2 emissions in response to P addition (Cleveland, Townsend, & Schmidt, 2002;Qian, He, & Wang, 2016). Microbial biomass tends to be limited by P in tropical soils (Cleveland et al, 2002;Turner & Wright, 2014;Waring, Averill, & Hawkes, 2013;Warren et al, 2015).…”

“…One laboratory experiment also found that P accelerates leaf litter decay in a tropical dry forest, whereas added N retards it (Powers & Salute, ). However, Qian et al () incubated soils with five different vegetation types at different temperatures for 5–7 days and found that microbial respiration does not significantly respond to inorganic N or P addition. The effects of P and N additions are site specific in tropical forests and more studies are needed to reveal the underlying factors influencing soil microbial activities and soil CO 2 emissions.…”

Response of Vegetation to Changes in Temperature and Precipitation at a Semi-Arid Area of Northern China Based on Multi-Statistical Methods

“…Furthermore, the two to four month lag length of NDVI in response to temperature for distinct sub-watersheds reveals that the vegetation may not have a synchronous response to temperature changes. As vegetation mainly accumulates nutrients and organic matter in spring and grows in summer and autumn [29], the distinct dominant and diversity of the vegetation types would be the main cause of different legacy effect for NDVI in response of the temperature. The agricultural area (upstream) presented a faster responce to temperature than the forest conservation area in the midstream and forest-urban mixed area in the downstream, which may be due to the short growth cycle and rapid growth rate of the crops [30].…”