Importance of Physiological Integration of Dwarf Bamboo to Persistence in Forest Understorey: A Field Experiment

1 Sasa spp., dwarf bamboo which dominate the undergrowth of temperate forests in Japan occur as clonal fragments in which ramets in light gaps to are connected to those in shaded understoreys by long rhizomes. We test whether persistence under shaded conditions is supported by translocation of assimilates from illuminated ramets. A dense population of Sasa palmata growing at an open site, was exposed to two light conditions (homogeneous: open-open and heterogeneous: open-shaded) and two rhizome connection treatments (intact and severed) in a full factorial design. 2 Ramet mass, and the mass of many parts of the clonal fragments, was much lower in the shade than in the open, but this effect was less marked when the rhizome connection was intact than when it was severed. Clone parts in shade may therefore be supported by translocation from connected clone parts in the open, with such physiological integration enhancing persistence where light supply is heterogeneous as in the gap-understorey continuum. 3 Above-ground biomass was reduced sooner than that below ground. Clonal fragments of S. palmata recover via dormant buds on rhizomes, whose longer persistence would therefore enhance performance of the clonal fragment. 4 Specific leaf area (SLA) was greater in shade than in the open, irrespective of rhizome connection, suggesting that individual leaves show morphological plasticity independently of only physiological integration.