Aggregate-associated soil organic carbon fractions in sub-tropical soil
undergoing vegetative restoration
Abstract
Precise assessment of soil organic carbon (SOC) storage requires
understanding how vegetation and soil physicochemical properties differ
in SOC fractions. Therefore, we aimed to analyze the dynamics of
aggregate-associated, liable organic carbon (LOC) fractions
corresponding to depth to clarify the effect of vegetation and soil
properties on water stable aggregate (WSA) mineral adsorption in
subtropical, red soil with five vegetation restoration regimes. The
results showed that the large macro-aggregate fraction dominated the
degraded red soil, which had the highest content of dissolved organic
carbon (DOC). WSA-associated, easily oxidized organic carbon (EOC)
varied from 6.26 to 20.02 g/kg and was not affected by vegetation types.
Schima superba pure forest (SP) significantly increased DOC (0.38
g/kg on average) and particulate organic carbon (POC, 7.92g/kg on
average), which had the highest biomass. Along with soil depth,
WSA-associated POC declined, while exhibiting a growth trend with
decreasing particle size, e.g., the highest POC was found in silt + clay
fraction. The RDA ordination indicated that soil porosity and TN were
the main soil parameters that explained the most variance. Meanwhile,
the vegetation biomass, except for litter, were all significantly
positively correlated with silt + clay fractions. Leaf biomass played
the most important role on DOC in macro-aggregate with a 53.42%
contribution. For aggregate-related POC, the largest contribution was
from the interactions between branch biomass and pH (47.78%) followed
by TN (35.1%) of micro-aggregate-related POC. Leaf biomass, silt + clay
fractions, and TN can be used as indicators to evaluate the impact of
vegetation restoration on WSA-associated SOC fractions. Broad leaved
forest or combined with indigenous coniferous species was a better
choice for SOC sequestration improvement in the study area.