GROWTH OF FLOATING-LEAVED AND SUBMERGED PLANTS IN ARTIFICIAL CO-CULTURED MICROCOSMS: MORPHOLOGICAL RESPONSES TO VARIOUS WATER FLUCTUATION REGIMES

摘要

Hydrocharis dubia can alternate between a rooted floating-leaved and a free-floating form, so given increasinglyfrequent precipitation extremes, it is not expected to be more negatively impacted by rapid water fluctuations than bygradual ones and may adapt water fluctuations by alteration of life forms. However, the opposite may be true forNymphoides peltata, with only a rooted floating-leaved form. We designed an experiment combining six water depthtreatments (constant shallow, constant deep, and two rapidly and two gradually fluctuating treatments) with three speciescombinations(N. peltata–H. dubia, N. peltata–Ceratophyllum demersum, and H. dubia–C. demersum) to investigate plantresponses to depth fluctuations and their co-cultured species. The total mass of N. peltata was considerably lower in therapidly- than in the gradually-fluctuating treatments. However, total mass of H. dubia in the rapidly-fluctuating treatmentswas similar to or higher than in the gradually-fluctuating ones. Rapid fluctuations had a negative impact on the growth of C.demersum than gradual fluctuating. The floating-leaved species demonstrated divergent adaptive strategies to different waterfluctuation patterns. In addition to expanding leaf blades, H. dubia can adapt to changing water depths by changing its lifeform. However, N. peltata, which mainly relies on morphological plasticity, such as petiole elongation, to adapt to water risemay reduce its abundance in communities subjected to increasingly frequent floods. The growth of submerged C. demersum,either co-occurring with H. dubia or with N. peltata, may be repressed by high flooding rates.