内蒙古草原3种针茅属植物不同组织水平的生物量生殖分配

 植物资源的生殖分配是链接进化生态学和功能生态学的纽带。该文从4个组织水平上研究了针茅属(Stipa) 3种植物克氏针茅(S. krylovii)、大针茅(S. grandis)和贝加尔针茅(S. baicalensis)的生物量生殖分配以及株丛和种群水平上可育散布体的数量和生物量。结果表明: 1) 3种针茅属植物在不同组织水平上的生物量生殖分配呈现明显分异。在株丛水平上, 克氏针茅和大针茅的株丛生物量分配到生殖枝的比例分别为44.3%和47.9%, 均显著高于贝加尔针茅的35.7%。在生殖枝水平, 克氏针茅的生殖枝生物量分配到穗器官的比例为30.3%, 显著低于大针茅的42.9%和贝加尔针茅的48.4%。在穗器官水平, 大针茅穗生物量分配到散布体的比例(63.9%)最高, 克氏针茅(49.9%)次之, 贝加尔针茅(39.1%)最低。在散布体水平, 贝加尔针茅的可育散布体生物量占散布体总生物量的比例为92.3%, 显著高于克氏针茅的67.2%和大针茅的71.3%。2) 尽管3种针茅属植物在不同组织水平上的生物量生殖分配存在显著差异, 但从最终可育散布体占株丛生物量的比例看, 克氏针茅为6.1%, 贝加尔针茅为6.3%, 大针茅为9.5%; 三者在生物量生殖分配上表现出明显的趋同效应。3) 3种针茅属植物生物量生殖分配的限制性环节存在显著差异。生殖枝向穗的生物量分配是克氏针茅和大针茅生殖分配的限制性环节, 株丛向生殖枝的生物量分配或穗器官向散布体的分配是贝加尔针茅生物量生殖分配的限制性环节。从可育散布体的数量和个体生物量看, 克氏针茅采取了倾向于拓展空间的增加散布体数量的策略, 而大针茅和贝加尔针茅逐步进化出了趋向于提高个体竞争能力的增加散布体个体生物量的策略。

BIOMASS REPRODUCTIVE ALLOCATION AT DIFFERENT ORGANIZATIONAL LEVELS OF THREE STIPA SPECIES IN INNER MONGOLIA GRASSLAND OF CHINA

Aims Resource allocation plays a central role in linking life history evolution and functional plant ecology. Stipa species are widely distributed in the Inner Mongolia grassland of China; however, their resource allocation patterns are not well addressed. We selected three Stipa species, S. krylovii, S. grandis and S. baicalensis and examined their reproductive allocation patterns at four organizational levels. We focused on two specific questions: 1) do these Stipa species exhibit similar or different reproductive allocation patterns at the same organizational level and 2) which step of biomass repro-ductive allocation is limiting the plant performance of each species? Methods We conducted this experiment in three sites dominated by S. krylovii, S. grandis and S. baicalensis, respectively, in Inner Mongolia grassland in 2007. At each site we investigated the density, height and biomass of reproductive tillers and vegetative tillers of each species in ten quadrats (1 m×1 m). We randomly sampled 50 reproductive tillers of each species and analyzed reproductive allocation at different organizational levels. Important findings Three Stipa species exhibited significant divergence in reproductive allocations at different organizational levels. At the bunch level, S. krylovii and S. grandis allocated more biomass to reproductive tillers than S. baicalensis. At the reproductive tiller level, S. krylovii allocated less biomass to reproductive tillers than S. grandis and S. baicalensis. At the spike level, S. grandis and S. krylovii allocated about 60% and 50% biomass to diaspore, respectively, while S. baicalensis allocated about 40% biomass to diaspores. At the diaspore level, S. grandis and S. krylovii allocated about 70% and S. baicalensis allocated about 90% biomass to fertilized diaspores. Despite these differences, the fraction of fertilized diaspore biomass in bunch biomass exhibited convergence. The species had different bottlenecks in reproductive allocation. Stipa grandis and S. krylovii were limited by the allocation of biomass from reproductive tillers to spikes, while S. baicalensis was limited by the allocation of biomass from bunch to reproductive tiller or by the allocation from spike to diaspores. Our experiment suggests these species have developed different life history strategies.