Dynamics of soil and foliar phosphorus fractions in a secondary tropical forest under altered seasonal precipitation patterns

Understanding how altered precipitation patterns affect the dynamics of phosphorus (P) fractions in both soil and foliage is crucial for predicting climate-induced changes in plant growth and community structure, especially within tropical forests with P-impoverished soils.

We conducted a nine-year precipitation experiment in a secondary tropical forest, simulating delayed (DW) and wetter wet season (WW) to reflect potential precipitation changes. We analyzed P fractions in soil (0–10 cm and 10–20 cm) and foliage of four dominant trees, and investigated the correlations among these P fractions and photosynthesis.

DW treatment reduced soil P bioavailability and induced foliar P redistribution, while WW treatment increased soil pH and NH₄⁺-N content but had little influence on soil P form. DW treatment generally reduced foliar total P levels and diminished various P fractions with notable species-specific disparities. Moreover, DW treatment variably reduced area-based photosynthetic carbon assimilation rates (A_area), exhibiting species-specific effects, while WW treatment inconsistently elevated A_area across species. The structural equation model revealed that A_area was directly influenced by foliar P fractions and photosynthetic nutrient efficiency, and indirectly by precipitation treatment on soil properties and P fractions.

Altered seasonal precipitation patterns affect soil bioavailable P forms and/or soil chemical properties, and thereby influence foliar P fractions allocation and photosynthesis of dominant trees. Soil and foliar P fractions responses to precipitation treatments varied across different sampling months, underscoring the complexity of P cycle and suggesting tree acclimation and resilience. These insights improve our understanding of climate effects on nutrient cycles and resilience.