关键词: 优势种群, 天然林, 生态位宽度, 生态位重叠, 生态位相似性比例

Abstract: This paper studied the effects of different combinations of cutting frequency (once every 14, 21, and 28 days) and stubble-remaining height (15, 25 and 35 cm) on the output of Ipomoea aquatica Forsk planted on floating-mats in a eutrophicated river of Shanghai. After cutting, the plants could still grow healthily during its whole lifecycle. The tiller number after 110 d growth was 5 times of the control, with the longest root length, average root length, and average root system diameter being 27.55 cm, 11 cm, and 15 cm, respectively. The fresh root biomass per plant was 146 g, and the roots per square meter floating mat could adsorb 3.36 kg suspended particulates. With increasing cutting frequency, the sprout growth rate had a trend of increasing first and decreased then, and the variation range was 0.54-3.7 cm·d^-1, compared with 1.63 cm·d^-1 of the control (no-cutting). Appropriate cutting could promote sprout growth rate. The biomass harvested per unit time had the similar variation trend as sprout growth, and the biomass growth rate was 3.83-37.9 g·m^-2·d^-1. The dry biomass output was the highest (2112 g·m^-2) in treatments cutting every 28 days and stubble-remaining height at 25 cm and 35 cm, and the stem/leaf ratio was higher in treatments cutting every 14 days and stubble-remaining height at 15, 25, and 35 cm, and cutting every 21 days and stubble-remaining height at 15 cm and 25 cm. To comprehensively consider the biomass output and quality as well as the management convenience of floating-mats, cutting every 21 days and stubble-remaining height at 15 cm was the best cutting regime, under which, the average sprout growth rate was 1.88 cm·d^-1, stem/leaf ratio was less than 1, and total biomass was 1966 g·m^-2.

Key words: Dominant populations, Natural forest, Niche breadth, Niche overlap, Niche similarity