Dynamics of phosphorus nutrition, allocation and growth of young beech (Fagus sylvatica L.) trees in P-rich and P-poor forest soil

Abstract

To investigate how long-lived forest trees cope with low soil phosphorus (P) availabilities, we characterized P nutrition of beech (Fagus sylvatica, L.) in soils from P-rich and P-poor beech forests throughout an annual growth cycle. Young trees were excavated with intact soil cores in mono-specific beech forests, kept under common garden conditions, and used for 33P labeling, analyses of P uptake, P content and biomass during five phenological stages (dormancy in winter, bud swelling in early spring, mature leaves in early and late summer, and senescent leaves in fall). Seasonal allocation patterns showed that young, emerging leaves were preferred sinks for P under P-poor conditions, thereby keeping foliar P concentrations at levels similar to those of trees grown in P-rich soil. Phosphorus concentrations in stems and roots of trees from the P-poor conditions were lower than those from P-rich conditions. Coarse roots were the main P storage tissue, supplying inorganic P to newly formed leaves, originating from the inorganic and organic P pools under low and high P conditions, respectively. Beech trees in P-poor soil exhibited net biomass increment early in the annual growth along with a strong P deficit, which was replenished by enhanced uptake in late summer and fall. Trees in P-rich soil grew until late summer, and showed a moderate P decline in organic pools and recovery late in fall, which coincided with elevated P uptake from soil. Beech in P-poor soil produced more biomass per unit of P but at a slower growth rate than those in P-rich soil, thereby exhibiting similar P-use efficiencies. Temporal decoupling of growth and P acquisition in combination with internal P trade-off between storage tissues and leaves facilitated flexible acclimation of beech to a wide range of soil P availabilities.

Towards a more physiological representation of vegetation phosphorus processes in land surface models

“…The extent to which plants can alter their biomass allocation in response to P limitation is key to their growth response. Observed responses include increased root biomass (Keith et al ., ), faster root turnover (Laliberté et al ., ), and seasonal decoupling of growth and P acquisition (Zavišić & Polle, ). An ecosystem‐level C budget study showed that plants can respond to reduced P availability via a shift in internal C allocation, with little change in canopy biomass and total productivity but an enhanced root growth (Keith et al ., ).…”

“…More efficient internal P recycling is another strategy for plants to respond to external P limitation (Adams, ; Zavišić & Polle, ). As plants age, a larger proportion of the P utilised in new growth is obtained from remobilisation rather than uptake (Jin et al ., ; Lang et al ., ).…”

“…This fraction of P retranslocation increases during later growth stages and under P‐deficient conditions (Aerts, ). There is evidence that coarse roots can be a significant storage for P to supply inorganic P to newly formed leaves (Zavišić & Polle, ). Both leaf (Hayes et al ., ; Lang et al ., ) and root P (Shane et al ., ) can be redistributed before senescence.…”

“…Plants trade C for N and P at different exchange rates (Raven et al ., ), leading to different symbiotic associations and possibly different trajectories of nutrient recycling (Zechmeister‐Boltenstern et al ., ). Furthermore, it has been shown that plants may need to maintain photosynthetic capacity to provide sufficient C for exudation and symbiotic association under P deficiency (Zavišić & Polle, ). This observation contradicts assumptions incorporated in some existing models that nutrient limitation directly down‐regulates photosynthesis, but it remains unclear whether this is a plastic or an adaptive response, and whether the level of carbon investment for P acquisition can be maintained as P deficiency increases.…”

Measurements of 18O‐Pi uptake indicate fast metabolism of phosphate in tree roots

“…; Spohn et al . ; Zavišić & Polle ). P i bound to Fe and/or Al oxy(hydr)oxides in the soil (Prietzel et al .…”