梁子湖优势沉水植物冬季种子库的初步研究

初步研究了梁子湖6种优势沉水植物如黄丝草、金鱼藻、菹草、黑藻、苦草和穗状狐尾藻等在冬季的广义种子库（种子、芽苞、断枝等），包括它们的繁殖特性、种子在小、结构及萌发时的衰减曲线等问题，主要结果为：（1）在梁子湖不同区域内，种子库大小不相同，满江湖、前江大湖、中湖和管理局网围内种子库分别为714.4粒／m^2、107.5粒／m^2、331.9粒／m^2和159.3粒／m^2。种子库的大小受到现实的种群数量、投鱼强度、人类干扰等因素的影响。（2）黄丝草、金鱼藻、菹草种九的种子库占有明显优势，全湖平均分别为198.8粒／m^2、91.7粒／m^2和21.4粒／m^2。（3）每一种植物种群广义种子库的构成和比例具有差异，金鱼藻、菹草、苦草、黑藻四种植物种子库中，无性繁殖体占有主要的地位；黄丝草、穗状狐尾藻两种植物种子库中，种子占有很大的比例，上述六种植物均可用种子和无性繁殖体来产生幼苗，补充到肿群中去。（4）种子库一般存在冬季休眠（菹草为夏眠），春季种子库萌发，尤其在3月和4月是种子库萌发的高峰期。

A PRELIMINARY STUDY OF WINTER SEED BANK OF DOMINANT SUBMERGED MACROPHYTES IN LAKE LIANGZI

Seed bank plays an important role in the re - establishment of disturbed vegetations. Soil cores were sampled from substrate of Lake Liangzi in Winter (Feb. 1998), and seed densities (general seed bank, including seed, brood - bud, shoot fragments) of Potamogeton maackianus, P. crispus, Ceratophyllum demersum, Hydrilla verticillata, Vallisneria spiralis and Myriophyllum spicatum, which were the dominant submerged macrophytes of the lake, were estimated by germination methods. The main results are as follows. (1 ) The seed densities varied in different fegions in Lake Liangzi, being 714. 4 seeds/m2 in Manjianghu region and 107. 5 seeds/m2 in QianJiang region. But in Zhonghu region and within the palisade region of Lake Liangzi Management, the seed densities were 331. 9 seeds/ m2 and 159. 3/m2, respectiively. (2) In the community of submerged macrophytes, seed banks of P. maackianus, C. demersum and P. crispus dominated the whole seed bank, with a density of 198. 8, 91. 7 and 21.4seeds/m2 (3) The general seed banks of each plant population had different structure and ratio. For C. demersum,P. crispus, V. spiralis and H. verticillata, the vegetative reproduction units were the most important,but for P. maackianus and M. spicatum, the ratio of seeds was the highest. All of the six studied species could produce seedlings by seeds and vegetative reproduction units,which resulted in an increase in quantity of the populations. (4) The seed banks are usually dormant in Winter (except P. crispus ). In Spring, the seed banks began to germinate and the germination Peak occurres from March to April. (5) The submerged macrcphytes seed banks are very complex. Human activities,population size of each plant and fish density can influence greatly the dispersal of seeds and the structure and densities of the seed banks.