Conversion of Natural Evergreen Broadleaved Forests Decreases Soil Organic Carbon but Increases the Relative Contribution of Microbial Residue in Subtropical China

Abstract

It has been recognized that land use change affects soil organic carbon (SOC) dynamics and the associated microbial turnover. However, the contribution of microbial residue to SOC storage remains largely unknown in land use change processes. To this end, we adopted a “space for time” approach to examine the dynamics of SOC and amino sugars, which was a biomarker of microbial residue C, in different natural forest conversions. Three typical converted forests were selected: an assisted natural regeneration (ANR) and two coniferous plantations of Cunninghamia lanceolata (Lamb.) Hook (Chinese fir) and Pinus massoniana Lamb. (pine) each. All of these were developed at the same time after the harvest of an old natural forest and they were used to evaluate the effects of forest conversions with contrasting anthropogenic disturbance on SOC and microbial residue C, along with the natural forest. Natural forest conversion led to an approximately 42% decrease in SOC for ANR with low anthropogenic disturbance, 60% for the Chinese fir plantation, and 64% for the pine plantation. In contrast, the natural forest conversion led to a 32% decrease in the total amino sugars (TAS) for ANR, 43% for the Chinese fir plantation, and 54% for the pine plantation at a soil depth of 0–10 cm. The ratios of TAS to SOC were significantly increased following natural forest conversion, with the highest ratio being observed in the Chinese fir plantation, whereas the ratios of glucosamine to muramic acid (GluN/MurA) were significantly decreased in the two plantations, but not in ANR. The contents of SOC, individual amino sugar, or TAS, and GluN/MurA ratios were consistently higher at a soil depth of 0–10 cm than at 10–20 cm for all of the experimental forests. Redundancy analysis showed that microbial residue C was significantly correlated with SOC, and both were positively correlated with fine root biomass, annual litterfall, and soil available phosphorus. Taken together, our findings demonstrated that microbial residue C accumulation varied with SOC and litter input, and played a more important role in SOC storage following forest conversion to plantations with higher anthropogenic disturbance.

Chemodiversity of Dissolved Soil Organic Matter from Amazon Rainforest as Influenced by Deforestation

“…For the deforested sites, the lowest values of microbial carbon biomass and microbial respiration correspond to the lowest abundance of labile and microbial-derived compounds [ 43 ]. This finding is consistent with the work done by Yang et al [ 44 ] and Zhou et al [ 45 ], who reported similar trends in the chemodiversity of DOM influenced by environmental factors [ 46 ].…”

Effects of Warming and Increased Precipitation on Soil Microbial Residues on the Qinghai–Tibet Alpine Meadows

“…It is generally considered that fungal residues are more difficult to decompose than bacterial residues; therefore, the primary reason for the decrease in the ratio of GluN/MurA in the warming treatment was the changes in microbial community structure (Yang et al, 2019). Besides, increased precipitation can change the community structure of microorganisms, and 220 the increases of soil moisture can make the bacterial-dominated soil microbial community structure evolve toward the fungus-dominated structure.…”

Microbial Biomass Is More Important than Runoff Export in Predicting Soil Inorganic Nitrogen Concentrations Following Forest Conversion in Subtropical China

“…A large number of Land 2022, 11, 295 2 of 15 studies have examined the effects of forest conversion on important ecosystem services and processes [5][6][7]. The conversion of natural forests to forest plantations often causes soil degradation [8][9][10], especially the decline of nitrogen (N) availability [11][12][13]. Nitrogen is a common limiting nutrient element for ecosystem productivity [14] and is available to plants mainly in inorganic form (i.e., NH 4 + and NO 3 − ) in the soil.…”