种群密度对沙米异速生长的影响

植物各器官之间的异速生长关系决定了植物的生活史对策,进而影响种群内个体之间的共存和生物多样性的维持。传统方法无法区分植物性状对其的响应是环境造成的,还是由于个体大小差异造成的,而异速生长分析能够解决这一问题。为此,本研究利用异速生长分析方法,通过模拟沙米在退化草地恢复过程中不同的种群密度(16, 44.4, 100和400株/m²),研究其各器官之间的异速生长关系。结果表明,沙米各器官之间都具有显著的异速生长关系:其中根和地上、根和主茎、叶和根、主茎和地上等器官生物量之间的变化不随种群密度的变化而变化,属于表观可塑性;根和茎、茎和地上、叶和茎等器官生物量之间的异速生长及生物量比值均受种群密度的显著影响,属于真正可塑性,这表明种群密度变化的确影响了沙米的生长变化。研究同时发现,沙米叶和地上生物量之间的异速指数仅在44.4株/m²种群密度下接近于0.75,即叶生物量与个体大小呈3/4次幂关系,符合生态代谢理论,而在其他密度时异速指数与0.75有显著差异(P<0.001),表明环境变化可能会导致沙米生长策略发生改变。种群密度对沙米繁殖和其他器官之间的异速生长关系影响不显著,表明在不同种群密度下,沙米仍保持相同的繁殖策略;然而种群密度在沙米生育期对繁殖和其他器官之间的异速常数和个体大小均产生了极显著的影响。因此,在探讨繁殖器官与个体大小的关系时,还需要关注植物生育期的变化,只有生育期相同的时候,才能比较不同研究之间的差异。

Effect of population density on the allometric growth of Agriophyllum squarrosum

The allometric relationships between plant organs determine the strategies of life history,affecting the coexistence and biodiversity of species.Traditional methods are not able to distinguish the responses of plant traits to environmental or genetic differences but allometric analysis can help solve this problem.Allometric analysis was used to study the relationships between different organs of Agriophyllum squarrosum by simulating different population densities of A.squarrosum (16,44.4,100 and 400 plants/m2) during the restoration of degraded grassland.The results showed that there are significant allometric relationships between organ pairs.Changes in root vs.aboveground biomass,root vs.main stem biomass,leaf vs.root biomass and main stem vs.aboveground biomass were not influenced by population density,indicating ‘apparent plasticity’ The allometric relationships of root vs.stem,stem vs.aboveground,leaf vs.stem biomass and their respective biomass ratio were significantly affected by population density,reflecting ‘real plasticity’.The allometric index of leaf vs.aboveground biomass at 44.4 plants/m2 was approximately 0.75,while the allometric indices at other plant densities were significantly different from 0.75 (P＜0.001),suggesting that environmental changes resulted in changes in growth strategy of A.squarrosum.The influence of population density on the allometric relationships between reproductive and other organs is not significant,indicating that A.squarrosum will adopt the same strategy under different densities,but that density differences will result in different allometric scaling and size of individual reproductive organ during different periods of reproductive development.It is important to consider changes in plant growth stages when investigating the relationships between reproductive organs and individual plants.