Department of Bioscience, Aarhus University, Vejlsøvej 25, Silkeborg, Denmark.
PLoS One. 2013 Apr 11;8(4):e60992. doi: 10.1371/journal.pone.0060992. Print 2013.
The ecological success of a plant species is typically described by the observed change in plant abundance or cover, but in order to more fully understand the fundamental plant ecological processes, it is necessary to inspect the underlying processes of survival and colonization and how they are affected by environmental conditions. A general ecological hypothesis on the effect of environmental gradients on demographic parameters is proposed and tested. The hypothesis is that decreasing fitness or competitive ability along an environmental gradient is associated with an increasing importance of survival for regulating the abundance of the species. The tested hypothesis is related to both the stress gradient hypothesis and whether the importance of competition increases along productivity gradients. The combined effect of nitrogen and glyphosate on the survival and colonization probability of two perennial grass species, Festuca ovina and Agrostis capillaris, which are known to differ in their responses to both glyphosate and nitrogen treatments, is calculated using pin-point cover data in permanent frames. We found that the relative importance of survival increased with the level of glyphosate for the glyphosate sensitive A. capillaris and decreased for the glyphosate tolerant F. ovina. Likewise, increasing levels of nitrogen increased the importance of survival for the relative nitrophobic F. ovina. Consequently, the proposed hypothesis was corroborated in this specific study. The proposed method will enable predictions of the effects of agricultural practices on community dynamics in a relatively simple setup eliminating the need to quantify all the interaction among the species in the plant community. The method will be immediately useful for the regulation of non-cultivated buffer strips between agricultural fields and semi-natural and natural biotopes such as hedgerows and waterways.
植物物种的生态成功通常通过观察植物丰度或盖度的变化来描述，但为了更全面地理解基本的植物生态过程，有必要检查生存和定植的潜在过程以及它们如何受到环境条件的影响。本文提出并检验了一个关于环境梯度对种群参数影响的一般生态学假设。该假设是，沿着环境梯度，适应度或竞争力的降低与生存对调节物种丰度的重要性增加有关。所检验的假设与胁迫梯度假说以及竞争的重要性是否随着生产力梯度的增加而增加有关。利用永久框架中的精确覆盖数据，计算了氮和草甘膦对两种多年生草本植物——羊茅（Festuca ovina）和鸭茅（Agrostis capillaris）的生存和定植概率的综合影响。这两种植物对草甘膦和氮处理的反应不同。我们发现，对于草甘膦敏感的鸭茅 A. capillaris，随着草甘膦水平的增加，生存的相对重要性增加，而对于草甘膦耐受的羊茅 F. ovina，生存的相对重要性降低。同样，氮水平的增加增加了相对耐氮的羊茅 F. ovina 生存的重要性。因此，在这项具体研究中，提出的假设得到了证实。该方法将使我们能够在相对简单的设置中预测农业实践对群落动态的影响，从而无需量化植物群落中所有物种之间的相互作用。该方法将立即对农业田与半自然和自然生物区（如树篱和水道）之间非耕作缓冲带的管理有用。
