为了评价亚高山地带木本植物种子萌发对策及其与生活史关联,该文对青藏高原东缘61种常见木本植物的种子萌发特征以及种子萌发与种子大小、扩散方式、海拔及生境的关系进行了调查分析。结果表明:1)61种植物的种子萌发率呈现偏斜、双峰分布。6种植物(9.8%)的种子萌发率大于80%,13种(21.3%)的萌发率在60%-80%之间,9种(14.8%)的萌发率在40%-60%之间,8种(13.1%)的萌发率在20%-40%之间,25种(41%)的萌发率小于20%,其中8种植物的种子萌发率为零,显示了该生境中木本植物的种子以休眠、低萌发率或连续稳定的萌发对策占优势,以避免不利的环境因素。2)种子扩散方式是决定61种木本植物种间萌发率变异(R^2=24.1%,P〈0.001)和萌发开始时间变异(R^2=21.3%,P〈0.01)的主要因素;种子大小、母体植株的海拔和生境对种子萌发率和萌发开始时间几乎没有影响(p〉0.05);风扩散的种子比脊椎动物扩散和无助扩散的种子有更高的萌发率(F=9.219,P〈0.001)和较早的萌发开始时间(F=6.772,P〈0.01)。说明植物生活史特征如种子萌发与扩散方式之间存在固有而紧密的联系,扩散能力强的种子(如风扩散)由于能散布到较远而空旷的生境,可能避免了各种有害因素或个体竞争,因而种子以较强的萌发能力进行拓殖:扩散能力弱的种子(如无助扩散)由于其散布距离较近,种子以休眠或降低萌发的方式来避免个体或同胞竞争以及各种有害因素,以获得最大的生态利益并确保物种延续。
Aims Seed germination is a crucial plant life history stage related to seedling establishment, survival, fitness and life history expression. Our objectives were to determine: 1) seed germination characteristics of common woody species from the eastern Qinghai-Tibet Plateau and 2) whether differences in seed germination among species are related to seed size, dispersal mode, and mother plant altitude and habitat. Methods We surveyed seed germination of 61 species under an alternating temperature regime (20 ℃/5 ℃; 12 h light/dark). We used one-way ANOVA to determine the effects of seed size, dispersal mode, altitude and habitat on final germination percentage and initial germination time, the least significant difference test (LSD) to survey the extent of differences in final germination percentage and initial germination time among dispersal categories and correlation analysis to determine the relationship between seed size and germination. Important findings Final germination percentages of the species displayed a skewed bimodal distribution, and this implies that dormancy and low and/or continuous germination are the main germination strategies to escape adverse factors. Variances in final germination percentages and initial germination time among species were largely dependent upon dispersal mode, but a few were influenced by seed size, habitat and altitude. Wind-dispersed seeds had higher mean germination percentage (60.6%) and earlier initial germination time (9 d) than those of vertebrate-dispersed (23.4%, 23 d) and unassisted-dispersal seeds (29.5%, 17 d). Findings indicate intrinsic association between life-history characteristics such as seed germination and dispersal mode.