Plant Traits Variably Respond to Plant-Soil Interactions during Secondary Succession on the Loess Plateau

Knowledge of plant photosynthesis, biomass, and stress resistance could contribute to exploring the growth and restoration of vegetation. However, the response of these plant traits to plant-soil interactions at different successional stages remains poorly understood, which limits the understanding of secondary succession. A greenhouse experiment was designed to test the effects of rhizosphere soils collected from early- (EarlySoil), mid- (MidSoil), and late-successional (LateSoil) plant communities on plant traits of early-, mid-, and late-successional species (EarlySp, MidSp, and LateSp, respectively). We found that plant traits reacted in a specific direction to plant-soil interactions at different successional stages. Specifically, compared with treatments of plants growing in their own soil, the net photosynthetic rate and single-photon avalanche diode significantly increased in LateSp-EarlySoil (treatment of plants growing in soil) (20%-31%) and LateSp-MidSoil (10%-18%); the maximum quantum efficiency of photosystem II increased in MidSp-EarlySoil (1%) and LateSp-MidSoil (4%); belowground soluble sugar concentrations decreased in LateSp-EarlySoil (33%) and LateSp-MidSoil (45%); leaf, stem, and root biomass increased in MidSp-EarlySoil (76%-123%), LateSp-EarlySoil (180%-342%), and LateSp-MidSoil (83%-137%), and in turn they decreased in EarlySp-MidSoil (40%-73%) and EarlySp-LateSoil (53%-67%). The results indicated that soil conditioned by pre-successional species (early- or mid-successional species) would be conducive to plant functional traits of subsequent successional species (mid- or late-successional species). Constrained redundancy analysis and path analysis suggested that water-soluble ammonium N, total N, and available N concentrations were key soil factors affecting early-, mid-, and late-successional species, respectively. Our findings confirm the directionality of succession and provide new information for plant population dynamics during secondary succession.