Abstract
PurposeIn plant-soil systems, phosphorus partitioning during the annual cycle related to nitrogen partitioning remains largely unknown. The present study aims at assessing the soil-plant P allocation patterns of four tree species along four phenological stages and its relationship with tissues and soil N concentrations.MethodsCryptomeria japonica, Larix kaempferi, Fagus crenata and Robinia pseudoacacia trees were selected to sample coarse roots, sapwood, foliage, litter and soil during four phenological stages where total and Olsen extractable P and nitrogen content were measured respectively.ResultsIntra- and inter plant tissue nitrogen correlated well with phosphorus during the four phenological stages, especially root nitrogen. Fagus and Robinia were phosphorus limited, Larix was nitrogen limited and Cryptomeria co-limited. All species reabsorbed phosphorus and nitrogen from foliage prior to leaf abscission and stored nitrogen in roots and sapwood. Phosphorus storage was solely found in sapwood of Robinia. Soil dissolved ammonium correlated positively with nitrogen reabsorption efficiency during the green leaf stage, while single soil nutrient variables did not correlate with phosphorus reabsorption efficiency.ConclusionsPlant tissues nitrogen partitioning correlated well with their respective phosphorus partitioning and the increase of soil NH4+ correlated positively with nitrogen reabsorption efficiency, regardless of tree species during the green leaf stage. The results of this study show the intricate relationship that exists between nitrogen and phosphorus in the soil-plant continuum as well as the tree species specific internal cycling of these nutrients.
Highlights
The availability of nitrogen (N) and phosphorus (P) is a driving force of plant community composition (Aerts and Chapin 2000; Kolb and Evans 2002; Güsewell and Gessner 2009) and their limitation or imbalance in forest ecosystems can reduce plant growth and photosynthetic activity (Güsewell and Gessner 2009; Zhang et al 2014; Luo et al 2015)
Soil dissolved ammonium correlated positively with nitrogen reabsorption efficiency during the green leaf stage, while single soil nutrient variables did not correlate with phosphorus reabsorption efficiency
Total C content of the top 30 cm was significantly lower in L. kaempferi (LK) and significantly higher in C. japonica (CJ) plots than in R. pseudoacacia (RP) and Fagus crenata (FC) (P < 0.05)
Summary
The availability of nitrogen (N) and phosphorus (P) is a driving force of plant community composition (Aerts and Chapin 2000; Kolb and Evans 2002; Güsewell and Gessner 2009) and their limitation or imbalance in forest ecosystems can reduce plant growth and photosynthetic activity (Güsewell and Gessner 2009; Zhang et al 2014; Luo et al 2015). N and P cycles are linked in soils, where microorganisms, fungi and plants produce enzymes that mineralize organically bound nutrients (Olander and Vitousek 2000; Turner 2008). P demand and P mineralization form a slow strongly regulated single pathway cycle and when P demand exceeds P mineralization, the production of phosphatase enzymes is stimulated, resulting in higher P mineralization rates (Keller et al 2012; Paul 2015; McQuillan et al 2020) while high phosphate levels repress phosphatase activity. If sufficient organic P is available in soils, plant P demand will be mostly met by P mineralization but never exceed it (Olander and Vitousek 2000). N mineralization may exceed plant demand, leading to N saturation, as the comparably fast multi-pathway regulatory cycle between plant N demand and N
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