Water extractable organic C and total N: The most sensitive indicator of soil labile C and N pools in response to the prescribed burning in a suburban natural forest of subtropical Australia

Abstract

Soil labile carbon (C) and nitrogen (N) pools are important indicators of soil fertility that are sensitive to environmental disturbance. However, few studies have periodically examined the long-term dynamics of soil labile C and N pools following prescribed burning and their implications on nutrient cycling in forest ecosystems. In this study, 0–5, 5–10, and 10–20 cm soil depths were sampled multiple times, spaning six years across a series of prescribed burning sites in a eucalypt natural forest of subtropical Australia. Water extractable organic C (WEOC) and total N (WETN), hot water extractable organic C (HWEOC) and total N (HWETN), microbial biomass C (MBC) and N (MBN) were analysed and correlated with the post-fire recovery time and other major environmental factors. Prescribed burning had long-lasting impact on WEOC and WETN for nearly 12 years following the burning. The lengthy recovery time was associated with the slow recovery in the forest floor of organic layers, which significantly diminished upon the burning. This was longer than the proposed 8–10 year burning cycle in Toohey Forest, and necessitated extending the burning cycle or reducing burning intensity to preserve the soil fertility. The WEOC and WETN were the most sensitive indictors of burning disturbances on soil labile C and N pools in this forest ecosystem. The MBC & MBN, and HWEOC & HWETN, however, did not show consistent patterns of recovery. More studies are needed to differentiate between the burning impacts and the seasonal impacts in the context of intensifying climate change and urban developments.