Balestri Elena, Lardicci Claudio
Department of Biology, University of Pisa, Pisa, Italy.
PLoS One. 2013 Aug 19;8(8):e72598. doi: 10.1371/journal.pone.0072598. eCollection 2013.
Dune plants are subjected to disturbance and environmental stresses, but little is known about the possible combined effects of such factors on growth and spatial colonization. We investigated how clones of Sporobolusvirginicus, a widespread dune species, responded to the independent and interactive effects of breakage of rhizomes, breakage position and burial regime. Horizontal rhizomes were severed at three different internode positions relative to the apex to span the range of damage by disturbance naturally observed or left intact, and apical portions exposed to two burial scenarios (ambient vs. increased frequency) for three months in the field. The performance of both parts of severed rhizomes, the apical portion and the remaining basal portion connected to clone containing four consecutive ramets, was compared with that of equivalent parts in intact rhizomes. Apical portions severed proximal to the third internode did not survive and their removal did not enhance branching on their respective basal portions. Severing the sixth or twelfth internode did not affect survival and rhizome extension of apical portions, but suppressed ramet production and reduced total biomass and specific shoot length. Their removal enhanced branching and ramet production on basal portions and changed the original rhizome growth trajectory. However, the gain in number of ramets in basal portions never compensated for the reduction in ramet number in apical portions. Recurrent burial increased biomass allocation to root tissues. Burial also stimulated rhizome extension only in intact rhizomes, indicating that disturbance interacts with, and counteracts, the positive burial effect. These results suggest that disturbance and recurrent burial in combination reduces the regeneration success and spread capacity of S. virginucus. Since global change leads to increasingly severe or frequent storms, the impact of disturbance and burial on clones could be greater in future and possibly prevent colonization of mobile dunes by the species.
沙丘植物会受到干扰和环境压力，但对于这些因素对生长和空间定殖可能产生的综合影响却知之甚少。我们研究了一种广泛分布的沙丘物种—— Virginiasporobolus 的克隆体如何应对根茎断裂、断裂位置和掩埋方式的独立及交互作用。相对于顶端，在三个不同的节间位置切断水平根茎，以涵盖自然观察到的或保持完整的因干扰造成的损伤范围，并将顶端部分在田间暴露于两种掩埋情况（环境掩埋与增加掩埋频率）下三个月。将切断根茎的两部分（顶端部分和与包含四个连续分株的克隆体相连的剩余基部部分）的表现与完整根茎中相应部分的表现进行比较。在第三节间近端切断的顶端部分无法存活，去除它们并没有增强各自基部部分的分枝。切断第六节间或第十二节间并不影响顶端部分的存活和根茎延伸，但抑制了分株产生，减少了总生物量和特定茎长。去除它们增强了基部部分的分枝和分株产生，并改变了原来的根茎生长轨迹。然而，基部部分分株数量的增加从未弥补顶端部分分株数量的减少。反复掩埋增加了对根组织的生物量分配。掩埋还仅在完整根茎中刺激了根茎延伸，表明干扰与掩埋的积极作用相互作用并抵消了这种作用。这些结果表明，干扰和反复掩埋共同降低了 Virginiasporobolus 的再生成功率和扩散能力。由于全球变化导致风暴越来越严重或频繁，干扰和掩埋对克隆体的影响在未来可能会更大，甚至可能阻止该物种在移动沙丘上定殖。
