Chinese fir root response to spatial and temporal heterogeneity of phosphorus availability in the soil

Deficiency in availability of phosphorus (P) in forest soils of southern China, where Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) stands have been established, greatly affects Chinese fir productivity. Deploying clones with high P-use efficiency could be a more attractive option than P fertilization to enhance the commercial productivity of Chinese fir. Thus, an understanding of the adaptive responses of roots to spatiotemporal variability of P, which is often ignored in previous studies, is essential. In this study, we report the root responses of a Chinese fir clone with high P-use efficiency to the spatially heterogeneous P availability in soil during various periods of time when P availability was controlled. The results showed significantly (p < 0.05) more root proliferation in the form of root length, root surface area, root volume, and root dry matter accumulation in P-replete than in P-poor patches when the patch persisted for a short period of time (50 days). As the patches persisted longer (100-200 days), root proliferation in P-replete patches appeared to decline. P-replete patches that persisted for short (50 days) and long (200 days) periods resulted in high root P accumulation, whereas P-replete patches that persisted for 100-150 days resulted in lower root P accumulation than other patches. It seems that the observed responses in the roots of the Chinese fir clone to heterogeneous P availability might include a comprehensive adjustment of root growth and intraroot P translocation in patches so as to maintain internal P homeostasis, as well as a trade-off between energy cost and production of new roots when the patch persists longer. Key words: Chinese fir, P-use efficiency, phosphorus plaques, root, nutrient heterogeneity. La carence en phosphore disponible (P) dans les sols forestiers du sud de la Chine oU des peuplements de sapin de Chine (Cunninghamia lanceolata (Lamb.) Hook.) ont ete etablis a un impact important sur la productivite de cette essence. Le recours a des clones a forte efficacite d'utilisation du P pourrait etre une option plus attrayante que la fertilisation en P pour ameliorer la production commerciale du sapin de Chine. Par consequent, il est essentiel de comprendre la variation spatiotemporelle du P, ce qui a souvent ete ignore dans les etudes precedentes. Nous presentons dans cet article les resultats d'une etude de cas realisee avec un clone de sapin de Chine a forte efficacite d'utilisation du P. L'etude portait sur la reaction des racines a l'heterogeneite spatiale de la disponibilite du P dans le sol pendant differentes periodes de temps durant lesquelles la disponibilite du P a ete controlee. La proliferation des racines en termes de longueur, de surface, de volume et d'accumulation de matiere anhydre etait significativement plus grande (p Mots-cles : sapin de Chine, efficacite d'utilisation du P, plaques de P, racine, elements nutritifs.
Introduction Phosphorus (P) is an essential plant nutrient that is indispensable in terrestrial ecosystems (Cordell et al. 2009). Plants absorb P as orthophosphate; however, orthophosphates can easily bind to iron, [...]