Soil Organic Carbon Mineralization and its Temperature Sensitivity Along a Vegetation Restoration Gradient in Subtropical China

Background and aims Soil organic carbon (SOC) mineralization produces important CO2 flux from terrestrial ecosystems which can provide feedbacks to climates. Vegetation restoration can affect SOC mineralization and its temperature sensitivity (Q10), but how this effect is related to soil moisture remains uncertain. Methods We performed a laboratory incubation using soils of different vegetation restoration stages (i.e., degraded vegetation [DS], plantation [PS], and secondary natural forest [SFS]) maintained under different moisture and temperature conditions to explore the combined effects of vegetation restoration and soil moisture on SOC mineralization and Q10. Results We found that cumulative SOC mineralization in PS and SFS were about 11.7 times higher than that in the DS, associated with higher SOC content and microbial biomass. Increased soil moisture and temperature led to higher SOC mineralization in the SFS and PS. However, in the DS, soil moisture did not affect SOC mineralization, but temperature enhancement solely increased (158.7%) SOC mineralization at the 60%MWHC treatment. Furthermore, significant interactive effect of vegetation restoration and soil moisture on Q10 was detected. At the 60%MWHC treatment, Q10 declined with vegetation restoration age. Nevertheless, at the 30%MWHC treatment, Q10 was lower in the DS than that in the PS. Higher soil moisture did not affect Q10 in the PS and SFS, but enhanced Q10 in the DS. Conclusions Our results highlight that the responses of SOC mineralization and Q10 to vegetation restoration were highly dependent on soil moisture and substrate availability, and vegetation restoration reduced the influence of soil moisture on Q10.

Deciphering the Effects of Waste Amendments on Particulate Organic Carbon and Soil C-Mineralization Dynamics

It is important to understand the dynamics of soil carbon to study the effects of waste amendment inputs on soil organic carbon decomposition. The aim of this study was to evaluate the effect of waste amendment carbon input on the soil organic carbon (SOC) content, soil particulate organic carbon (POC) content and soil organic carbon mineralization rate dynamics. A 60-day experiment was carried out in the laboratory. The following treatments were compared: (1) CK: soil without amendments; (2) FW1: soil with food waste compost (soil/food waste compost = 100:1); (3) FW2: soil with food waste compost (soil/food waste compost = 100:2); (4) GW1: soil with garden waste compost (soil/garden waste compost = 100:0.84); (5) GW2: soil with garden waste compost (soil/garden waste compost = 100:1.67); (6) FGW1: soil amendments mixture (soil/food waste compost/garden waste compost = 100:0.5:0.42); (7) FGW2: soil amendments mixture (soil/food waste compost/garden waste compost = 100:1:0.84); the inputs of amendment carbon to FW1, GW1 and FGW1 were 2.92 g kg−1, the inputs of amendment carbon to FW2, GW2 and FGW2 were 5.84 g kg−1. The results showed that the addition of waste amendments increased the amount of cumulative mineralization from 95% to 262% and accelerated the rate of soil mineralization. After adding organic materials, the change in the soil organic carbon mineralization rate could be divided into two stages: the fast stage and the slow stage. The dividing point of the two stages was approximately 10 days. When equal amounts of waste amendment carbon were input to the soil, there was no significant difference in SOC between food waste and garden waste. However, SOC increased with the amount of amendment addition. However, for POC, there was no significant difference between the different amounts of carbon input to the garden waste compost treatments. SOC and POC were significantly correlated with the cumulative emissions of CO2.