Bastida Fernando, Talavera Salvador
Departamento de Ciencias Agroforestales, Escuela Politécnica Superior, Universidad de Huelva, Palos de la Frontera, Spain.
Ann Bot. 2002 Apr;89(4):427-34. doi: 10.1093/aob/mcf065.
Cistus species are obligate seeding, early colonizers that follow disturbance, particularly fire, in Mediterranean ecosystems. We studied seed release, seed dispersal and soil seed populations in stands of Cistus ladanifer and C. libanotis. Seed release started in mid- to late summer (C. ladanifer) or in early autumn (C libanotis), and continued for a very extended period: 8-10 months in C. ladanifer, and for a mean of 16 months in C. libanotis. The xerochastic capsules of both species released seeds by successive dehiscence of the locules. All capsules begin to dehisce simultaneously at the start of the seed release period, but in C. libanotis capsule fragmentation replaced dehiscence early in the seed release period. In plants of both species, seed shadows were characterized by a peak of density beneath the plant canopy and a very short tail of much lower densities, indicating that seeds are concentrated beneath mother plants when dispersed. Nevertheless, in late May, at the onset of the fire season, soil seed densities beneath plant canopies were low compared with densities expected from seed shadows, but were apparently high enough to allow recovery of the stands if a disturbance, such as fire, had taken place. Seed-eating Bruchidae in summer and granivorous ants during the seed release period were apparently the main causes of seed losses. Results suggest that in both Cistus species, the staggered seed release could constitute an efficient risk-reducing trait. The plant pool of seeds existing throughout most of the year could be a relevant component of Cistus seed banks.
岩蔷薇属植物是专性种子植物，是地中海生态系统中受干扰（尤其是火灾）后最早的定居者。我们研究了岩蔷薇和黎巴嫩岩蔷薇林分中的种子释放、种子传播和土壤种子种群。种子释放始于夏末至秋中（岩蔷薇）或初秋（黎巴嫩岩蔷薇），并持续很长一段时间：岩蔷薇为8 - 10个月，黎巴嫩岩蔷薇平均为16个月。这两个物种的耐旱性蒴果通过小室的连续开裂来释放种子。在种子释放期开始时，所有蒴果同时开始开裂，但在黎巴嫩岩蔷薇中，蒴果破碎在种子释放期早期就取代了开裂。在这两个物种的植株中，种子阴影的特征是植株冠层下方密度峰值和密度低得多的极短尾部，这表明种子在传播时集中在母株下方。然而，在5月下旬火灾季节开始时，与种子阴影预期的密度相比，植株冠层下方的土壤种子密度较低，但如果发生火灾等干扰，显然足以使林分恢复。夏季的食种子豆象科昆虫和种子释放期的食谷蚂蚁显然是种子损失的主要原因。结果表明，在这两种岩蔷薇属植物中，交错的种子释放可能是一种有效的降低风险特征。全年大部分时间存在的种子植物库可能是岩蔷薇种子库的一个相关组成部分。
