黄土丘陵沟壑区主要物种植冠种子库动态及其生态策略

植冠种子库是植物适应环境并应对外界干扰的种子生态策略之一,研究了黄土丘陵沟壑区12种主要植物植冠种子库动态,结果表明:杠柳不具有植冠种子库,其他11种植物均具有植冠种子库;除了黄刺玫种子在翌年5月达到脱落高峰,其他植物大部分种子在冬季脱落,其中杠柳、达乌里胡枝子、茭蒿、黄柏刺和水栒子的大部分种子脱落集中偏早,铁杆蒿和土庄绣线菊的大部分种子脱落集中偏晚;植冠宿存对大部分植物种子的萌发特性表现为促进作用;但不同植物种子的萌发时滞对植冠宿存响应差异较大;9种植物种子在植冠上宿存至翌年2月底,其种子活力仍能维持达60%以上;该区植物表现出不同的植冠种子库策略,通过不同的方式来减少干扰的威胁,提高成功萌发与更新的几率,它们或具有较大规模的宿存量、或调控种子萌发特性、或提高种子维持活力的百分比。此外,全面了解该区植物形成植冠种子库的机理及对应的生态策略还有待于全面、深入的研究。

Dynamics and ecological strategies of aerial seed bank of main species in the hill-gully Loess Plateau

Delayed seed dispersal, leading to form an aerial seed bank, is one way to deal with disturbances in the special environment. Previous studies on aerial seed bank have focused on the fire-prone and arid desert habitats. However, there are few studies on aerial seed storage in the eroded slope habits, where lack of available soil water due to low soil water holding capacity caused by water erosion and drought. The dynamics of aerial seed banks, the seed germination and viability characteristics of 12 main species were studied in the hill-gully Loess Plateau, then the aerial seed bank strategies were analyzed which adapt the disturbances in the study region. The results showed that the seeds of Periploca sepium can''t form aerial seed bank with no seed stored on plants until the end of the next February. While the seeds of the Rose xanthina can form the persistent aerial seed bank with seeds stored on plants until the next October. The other 10 species excepted Periploca sepium and Rose xanthina also can form aerial seed bank, which density are not significant high with percentages of seeds stored on plants below 5% up to the next May. Most seeds of the other 11 species dispersed during the winter, except the seeds of the Rose xanthina dispersed intensively until the next May. The seeds of the Periploca sepium, Lespedeza davurica, Artemisia giraldii, Berberis virgetorum and Cotoneaster multiflorus dispersed intensively earlier among 12 species while the seeds of the Artemisia gmelinii and Spiraea salicifolia dispersed intensively later among 12 species. Delayed seed dispersal promoted the ability of seed germination for most species. The cumulative percentage of seed germination rate reached the peak in December for Artemisia giraldii, Artemisia gmelinii and Hippophae rhamnoides, and at the end of the next February for Sophora davidii, Potentilla chinensis, Syringa oblata, Spiraea salicifolia, and in the next May for Lespedeza davurica. However, delayed seed dispersal reduced the ability of seed germination for the Berberis virgetorum. The seeds stored on plants belonged to different species need different time for seeds beginning to germinate. The seeds of nine species can retain on plants until the end of the next February, of which the percentage of seed with viability reached up to 60%. The percentages of the seeds with viability from five species were increased after stored on plants until the end of the next February. There were different aerial seed bank strategies for the species to deal with disturbances in the study region. The seeds avoided threaten from uncertainties of the erosion environments, then germinated and regenerated successfully by storing more seeds on the canopy, regulating the seed germination and increasing the percentage of viable seeds. Moreover, it''s uncertain that weather the seeds can form aerial seed bank in different environments or in different years. The aerial seed bank types of some species varied as the environmental condition changed, which indicated that the aerial seed bank dynamics of some species had variability. Thus, more studies should be done in this field.