Experimental investigation of the origin of fynbos plant community structure after fire

火灾后凡波斯植物群落结构起源的实验研究

• 批准号: NE/H000801/1
• 负责人: Jonathan Silvertown
• 金额: $ 5.8万
• 依托单位: The Open University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH000801%2F1
• 关键词: Experimental; investigation; origin; fynbos; plant

In an ongoing investigation of the relationship between plant communities and hydrology in fynbos habitat in the Cape of South Africa (www.open.ac.uk/fynbos)., we are testing the hypothesis that plant species in fynbos communities segregate on fine-scale hydrological gradients. We have already shown that this occurs in meadow plant communities in England (Silvertown et al. 1999. Nature 400: 61-63) and have now demonstrated the same phenomenon also occurs in fynbos. This is an important discovery because it shows that quite different plant communities (with almost no plant families in common) are structured by the same fundamental mechanism. It is also surprising because fynbos habitats are fire-driven ecosystems that burn and regenerate naturally after fire and one might expect this disturbance to over-ride any fine-scale hydrological influence. Fires occur in the S Hemisphere summer (Nov - Apr) with a periodicity of 15 - 50y, but are unpredictable. A fire has just occurred at one of our field sites and we wish to take advantage of this unpredicted event to set-up a long-term experiment to test two hypotheses: A. Within-plot hydrological differences influence the structure of communities by controlling seedling establishment after fire, B. Seedling response to hydrology is influenced by root competition. The hypotheses will be tested by extracting soil monoliths (blocks of soil) with intact soil seed banks from different locations along the known hydrological gradient and transferring these to wetter and drier locations within the site. Control monoliths will be dug up and replaced in their original locations. A root barrier treatment (with controls) will be used in the experiment to determine the effect of root competition on plant performance along the soil moisture gradient. If hypothesis A is correct, then seedling mortality ought to be greater in translocated monoliths than controls and the ultimate species composition of monoliths should be influenced by their post-fire location on the hydrological gradient. Hypothesis B will be supported if competition treatments alter the effect of hydrology on distribution. Results will be incorporated into a spatial model that will be used to determine whether the effects measured in the experiment are sufficient to generate the patterns of species distribution observed late in post-fire succession. The sensitivity of the model outputs to a range of patterns of seed dispersal and changes in hydrology will be tested.

在一项关于南非开普省fynbos栖息地植物群落与水文学之间关系的持续调查中(www.Open.ac.uk/fynbos)，我们正在验证fynbos群落中的植物物种在细微尺度的水文梯度上进行隔离的假设。我们已经证明，这发生在英格兰的草甸植物群落中(Silvertown等人。1999年。自然400：61-63)，现在已经证明同样的现象也发生在fynbos中。这是一个重要的发现，因为它表明完全不同的植物群落(几乎没有共同的植物科)是由相同的基本机制构成的。这也是令人惊讶的，因为fynbos的栖息地是火驱动的生态系统，火灾后会自然燃烧和再生，人们可能会认为这种干扰会压倒任何细微规模的水文影响。火灾发生在S半球夏季(11-4月)，具有15-50年的周期性，但不可预测。我们的一个野外地点刚刚发生了一场火灾，我们希望利用这一不可预测的事件来建立一个长期的实验来检验两个假设：a.小区内的水文差异通过控制火灾后的苗木建立来影响群落结构；b.苗木对水文的反应受到根系竞争的影响。这些假设将通过从已知水文坡度的不同位置提取具有完整土壤种子库的土壤整体(块土壤)并将其转移到场地内更潮湿和更干燥的位置来检验。控制块将被挖出来，并在原来的位置进行更换。在试验中将使用根屏障处理(与对照)，以确定根竞争对沿土壤水分梯度的植物表现的影响。如果假设A是正确的，那么移位整体的幼苗死亡率应该比对照更大，整体的最终物种组成应该受到它们在火灾后在水文坡度上的位置的影响。如果竞争处理改变了水文对分布的影响，假设B将得到支持。结果将被合并到一个空间模型中，该模型将用于确定在实验中测量的影响是否足以产生在火灾后演替后期观察到的物种分布模式。将测试模型输出对一系列种子传播模式和水文变化的敏感性。