Comparing forest carbon fluxes at locations with different land-use histories and restoration strategies

We compared carbon fluxes at locations differing in land-use history and forest restoration strategies, i.e., planted and naturally regenerating forests. We (1) quantified the carbon (C) input from litterfall, (2) measured total soil respiration and its component fluxes, and (3) identified the abiotic and biotic factors influencing C input by litterfall and C release from the soil.

We established four plots each in planted and naturally regenerating Leptospermum scoparium (mānuka; Myrtaceae) forests of similar age in warm, temperate New Zealand. Litterfall and total soil respiration were measured over one year. Organic layer and mineral soil samples were analysed for physical, chemical, and biological characteristics.

Annual litterfall C input in planted forests on former agricultural land was more than double that of naturally regenerating forests, which was partly explained by higher soil nutrient availability. Annual mean soil respiration was 28% higher in planted than naturally regenerating forests. Total soil respiration in both forest types was positively correlated with root carbon stocks. The interaction of soil temperature and soil water content affected seasonal patterns of total soil respiration in both planted and naturally regenerating L. scoparium forests.

We found that soil and vegetation characteristics associated with land-use histories and restoration strategies affected C fluxes in young L. scoparium forests. The low number of plots may limit generalisability. However, this study lays the foundation for further comparative work in planted and naturally regenerating forest systems.