植冠与土壤种子库储存种子的萌发特性及策略

为明确黄土丘陵沟壑区植物种子库如何调控种子萌发来提高个体适合度,选择研究区7种具有种子库的主要物种为研究对象,以刚成熟和室内储存种子为对照,比较植冠宿存(5个宿存期)和土壤埋藏(5a埋藏期)对植物种子萌发特性的影响,探讨植冠种子库与土壤种子库储存下的种子萌发策略。结果表明:7种植物种子经过不同种子库储存后萌发特性表现出明显的种间差异,黄刺玫(Rosa xanthina)和水栒子(Cotoneaster multiflorus)种子萌发力表现为植冠宿存不变型、土壤储存增强型,土壤储存明显提高水栒子种子萌发速率;达乌里胡枝子(Lespedeza davurica)和狼牙刺(Sophora davidii)种子萌发力表现为植冠宿存增强型、土壤储存减弱型,种子萌发历时表现为植冠宿存延长型,土壤种子库储存还可加快达乌里胡枝子萌发速率、缩短萌发历时;茭蒿(Artemisia giralaii)和铁杆蒿(Artemisia gmelinii),种子萌发率随植冠宿存时间先升高后降低,随土壤储存时间先降低后升高,土壤储存可推迟其萌发,铁杆蒿种子萌发速率在植冠与土壤储存后均加快;紫丁香(Syringa oblata)种子萌发率随植冠宿存先升高后降低,土壤储存明显加快其种子启动萌发与速率。在黄土丘陵沟壑区,植物种子经过植冠或土壤种子库储存,或增加、加快、提早萌发充分利用有利条件提高占据性,或减少、减缓、推迟萌发分摊不利条件的风险;而且该区植物植冠与土壤储存后种子萌发特性间的关系,体现各自适应环境与应对干扰的分工与协作策略,主要表现为:单一主导型和相辅相成型。

Seed germination characteristics and strategies of seeds stored in canopy and soil seed banks

To determine how seeds improve their individual fitness by regulating their germination characteristics, we selected seven species with obvious canopy and soil seed banks in the hill-gully Loess Plateau. Effects of the duration of canopy storage (five storage periods) and soil storage (burial periods of five years) on seed germination were analyzed, which were compared with seeds of just matured or stored in laboratory as control. And the germination strategies of seeds after storage in canopy seed bank and soil seed bank were discussed. Our results indicated that the seed germination characteristics of the seven species were obviously different after storage. For Rosa xanthina and Cotoneaster multiflorus, storage improved the seed germination ability of the soil seed bank but had no effect on that of the canopy seed bank, and the seed germination rates of the soil seed bank of the C. multiflorus was considerably increased. For Lespedeza davurica and Sophora davidii, storage improved the seed germination ability of the canopy seed bank but weakened that of the soil seed bank. Meanwhile, the seed germination lasting times of the canopy seed bank were prolonged after storage, whereas the seed germination rate and seed germination lasting times of the soil seed bank were accelerated and shortened for L. davurica, respectively. For Artemisia giralaii and A. gmelinii, seed germination percentages initially increased but then declined as the duration of canopy storage increased, whereas the seed germination rate initially declined and then increased. Storage of the soil seed bank also delayed the seed germination for both species, whereas storage of both the canopy and soil seed banks increased the seed germination rates of A. gmelinii. For Syringa oblate, seed germination percentages initially increased but then declined as the duration of canopy storage increased, and storage of the soil seed bank both increased the germination rates and promoted seed germination. In conclusion, seeds from the hill-gully Loess Plateau either (1) took full advantage of favorable conditions to finish regeneration in right time quickly by increasing germination percentage, speeding up seed germination rate and germinating at high concentration during the early stages of storage or (2) shared the risk of unfavorable conditions by reducing germination percentage, slowing down seed germination rate and deferring seed germination through seed storage in the canopy or soil seed bank. In addition, the relationship between seed germination characteristics of the canopy storage and that of soil seed bank storage indicated that plant use the division and cooperation storages of canopy and soil seed bank to adapt environments and to respond disturbance, which strategies mainly presented as single-dominant and tow-complementary patterns.