Impact of long-term warming on soil aggregate stability and soil organic carbon stabilisation in a subalpine meadow
Natasha H. Blaesbjerg, Leah Moore, Elizabeth M. Wandrag, Mark J. HovendenContext
Soil aggregation is crucial for soil organic carbon (SOC) stabilisation, yet its response to climate warming in minimally managed systems is not fully understood.
Aims
This study was conducted to evaluate impacts of short-term (2 years) and long-term (10-years) warming on SOC dynamics in organic soils.
Methods
We employed open-top chambers to achieve a 2°C warming effect in a subalpine meadow in Tasmania, Australia (mean SOC, 0.14 kg kg−1; mean pH, 5). Soil samples were analysed seasonally for water-stable aggregates (WSA) and aggregate-associated SOC content across three size fractions: large macroaggregates (>2.00–5.6 mm), small macroaggregates (0.25–2 mm) and microaggregates (0.053–0.25 mm). Linear models were fitted to assess the effect of warming duration and sampling season.
Key results
Aggregate mean weight diameter, whole soil WSA and distribution of WSA across size fractions were all stable after 2 and 10 years of warming. Accordingly, no significant changes in response to warming were observed in whole soil SOC content or aggregate-associated SOC content. However, aggregate stability varied between sampling seasons and there was a significant effect of sampling season on aggregate-associated SOC content that increased with warming duration.
Conclusions
This study demonstrated that, despite apparent stability, warming affected the dynamics of aggregate-associated SOC by altering the amplitude of the seasonal variation.
Implications
Seasonal reconfiguration of carbon pools can have implications for long-term maintenance of SOC stocks, and we suggest future studies focus on this aspect across organic soils from other regions under similar conditions.