苏北海滨湿地互花米草两种繁殖方式研究

Abstract

在江苏盐城新洋港滩涂由海向陆建立样地：光滩（Mudflat）、零星米草斑块（SAP）、稳定米草滩下边缘（SAFI）、2003年米草定居处（SAF03）、1989年米草定居处（SAF89）、碱蓬滩（SS）及禾草滩（Grass flat），在每个样地分别建立6个样方，构建原地栽培系统（长1 m×宽1 m×深0.7 m），其中3个用于无性繁殖体栽培，3个用于有性繁殖体栽培，对互花米草的种子萌发、无性分株及实生苗的定居、生长、繁殖进行了研究。结果表明：（1）受海浪物理冲刷、淹水胁迫、受潮浸频率及土壤水分的影响，实验系统各样地种子萌发率均较低，只有样地SAFI处互花米草种子萌发率为17.8%，显著高于其他样地（<em>P</em> < 0.01）。SAP、SAFI、SAF03、SAF89和Grass flat处实验最初栽培的互花米草无性分株植株存活率较高（大于60.0%）且样地间差异性不显著（<em>P</em> > 0.05）；Mudflat处无性分株存活率极低（7.8±2.2）%，SS处无性分株全部死亡（0.0%）。无性分株和实生苗相比较，除Mudflat和SS样地二者存活率接近，其余样地的无性分株成活率均远高于有性分株。（2）互花米草无性分株在SAP、SAFI和SAF89样地中的株高、叶长、叶数、叶宽和叶厚均较高；实生苗在SAFI处长势较好，其他样地植株矮小、基径细或者死亡。无性分株生长指标显著高于实生苗。（3）各样地成功定居的无性分株均有结实植株，而实生苗只有Mudflat 和SAFI处结实。样地Mudflat、SAP、SAFI、SAF03、SAF89和Grass flat 无性分株分蘖数分别为21.7、23.0、25.5、6.8、9.0和4.1，实生苗的分蘖数除在Mudflat处达到14.0外，在其他样地均未分蘖。（4）各样地互花米草的无性分株单株生物量显著大于实生苗。两种繁殖方式地上生物量分配都呈现出向海陆两边递减的趋势，而地下生物量分配表现出相反的情况。综合对比各项指标，可以看出，在研究区内互花米草无性繁殖方式的定居成功率、生长、繁殖等指标均优于有性繁殖方式。研究区内互花米草种群的维持和扩张以无性繁殖方式为主。;Landward sampling sites along an intertidal zone in Xingyanggang (Mudflat, <em>Spartina alterniflora</em> patch (SAP), <em>S. alterniflora </em>flat infra-edge (SAFI), <em>S. alterniflora </em>flat 2003(SAF03), <em>S. alterniflora </em>flat 1989(SAF89), <em>Suaeda salsa </em>(SS), Grass flat) were selected, 6 sampling plots were set to build 6 situ planting systems (1m length × 1m width × 0.7m depth) at every sampling site, and 3 systems for ramet planting and other 3 for seedling planting. The <em>S. alterniflora</em> seed germination, ramet, seedlings growth and propagation were investigated during the growing seasons of <em>S. alterniflora</em>. The results showed that: (1) Stressed by physical erosion of seawater, waves, tidal flooding and soil water, the seed germination rate in all of sampling sites was low, which was the highest at SAFI (17.8%, <em>P</em> < 0.01). The ramet survival rate was greater (> 60.0%) at SAP、SAFI、SAF03、SAF89 and Grass flat than Mudflat (7.8%)and SS (0.0%); the ramet survival rate was much greater than seedling survival rate at SAP、SAFI、SAF03、SAF89 whereas was similarly low at Mudflat and SS. (2) Stem height, leaf length, leaf number, leaf width and leaf thickness of ramet at SAP, SAFI and SAF89 of wwere higher than that of other sites; seedling grew well at SAFI, while grew small or even died at other sites. Totally ramet grew much better than seedling. (3) All the survived ramet successfully settled and fructified, while only the survived seedling at Mudflat and SAFI fructified. The tillers of ramet was of 21.7 at Mudflat, 25.5 at SAP, 23.0 at SAFI, 6.8 at SAF03, 9.0 at SAF89 and 4.1 tillers per ramet at Grass flat, respectively; while seedling did not tiller (tillers per seedling <1.0) at most sites except at Mudflat (with 14.0 tillers per seedling). (4) The individual ramet biomass was significantly greater than individual seedling biomass at all sampling sites. Above-ground biomass allocation of two reproductive modes decreased toward sea and toward land, respectively, while the underground biomass allocation showed the opposite situation trend. Generally, in the study area the asexual propagules performed better than sexual ones at index of settlement, growing and reproduction, indicating that asexual propagules played more important role than sexual ones during the <em>S. alterniflora</em> salt marsh development.