Abstract
•Available phosphorus (P) content in soil increased from plantation until deciduous broadleaved forest.•The labile (easily available for plants) P content decreased during forest succession.•Available P was gradually transformed to stable pools during forest succession from plantation to evergreen broadleaved forest.•Phosphorus utilization in forest ecosystems shifts during succession from acquiring to recycling process.
Although phosphorus (P) is a limiting nutrient for plant growth in subtropical forests, the effects of forest succession on soil P dynamics, which in turn influences P availability, are unclear. The objective was to access the impacts of forest succession on P fractions of different availability (Hedley sequential fractionation) in highly weathered subtropical soils. We compared the P dynamics and availability under the chronosequence of forest succession from four stages: i) Cunninghamia lanceolata plantation, ii) through mixed broadleaf-conifer, iii) deciduous broadleaved, and finally iv) evergreen broadleaved forest. The soil P was dominated by stable P fractions (69–76%) in all successional stages. Forest succession increased total P content from plantation (199 mg kg−1) to evergreen broadleaved forest (253 mg kg−1), whereas P reached the peak in deciduous broadleaved forest and then remains stable due to balance between input with litter and litter decomposition and tree uptake. Stable P (non-available P) increased for 31–39% with forest succession because soil acidification led to more Fe and Al (oxyhydr)oxides strongly bounding P. Moderately labile P (moderately available P) contents under deciduous and evergreen broadleaved forests were higher than under plantation and mixed forest due to organic matter accumulation. However, labile (easily available) P content was reduced 35–50% by succession because of P removal by plant uptake. Available P content reached the peak under deciduous broadleaved forest (64–81 mg kg−1) and decreased again, indicating that forest ecosystem transit from P acquiring to P recycling system (litter input and plant uptake of mineralized P). Fine root biomass was the primary driver that controlled total, moderately labile and stable P contents during forest succession. Available P increased with soil organic carbon (SOC), suggesting that organic matter is crucial to maintain P availability. The C/P ratio of litter was the primary driver decreasing available P because litter decomposition released P is the main source determining P availability in soil. The increase of moderately labile P following forest succession played a crucial role for accumulation of available P. These results suggest that forest succession increases soil P availability until deciduous broadleaved forest. Therefore, strong measures to facilitate succession to the deciduous broadleaved forest stage should be a key approach to increase long-term soil P availability in subtropics.