Root morphology and seedling growth of three tree species in southern China in response to homogeneous and heterogeneous phosphorus supplies

Abstract

Trees adjust their root morphological characteristics to respond heterogeneous phosphorus conditions, and root length and root-to-shoot ratio will increase to improve phosphorus nutrient absorption in heterogeneous phosphorus soils. This study examined the responses of root morphology and seedling growth to homogeneous and heterogeneous phosphorus (P) supplies in three major tree species (Cunninghamia lanceolata, Pinus massoniana, and Phoebe zhennan) in southern China. Pot experiments including two homo-P and five hetero-P supplies with different P dosage levels were conducted across three species. Root length, root average diameter, root biomass, aboveground biomass, root-to-shoot ratio, P accumulation, P-efficiency ratio, and increments in height and diameter of seedlings were quantified. Roots of the three species showed symmetric and asymmetric growth in response to homo-P and hetero-P supplies, respectively. The root biomass and average diameter were greater in the P-rich patch than in the P-poor patch, and roots in the P-poor patch were thinner and longer than their opposite counterparts. The root length and biomass were higher in hetero-P treatments than in homo-P treatments at an equivalent P dosage. The heterogeneity magnitude was negatively correlated with the aboveground biomass and positively correlated with the root biomass and root-to-shoot ratio. The P-efficiency ratio was negatively correlated with the dose of added P. The growth responses include a comprehensive adjustment in the root morphology and root-to-shoot ratio. The root growth pattern can change to adapt to lower P availability in soil, and the root-to-shoot ratio will increase to optimize nutrient partitioning and improve P-nutrient absorption in hetero-P soils.