Martinod Kylie L, Gorchov David L
Department of Biology, Miami University, Oxford, OH 45056, USA.
AoB Plants. 2017 Feb 13;9(2):plx006. doi: 10.1093/aobpla/plx006. eCollection 2017 Mar.
It has been hypothesized that invasive plant species with extended leaf phenology (ELP) elevate generalist herbivore populations, increasing herbivory on native plants (apparent competition). This hypothesis assumes that consumption of the invasive is associated with periods of ELP, the invasive is a major component of the herbivore's diet, and that it is more nutritious than native plants during periods of ELP. We tested these assumptions by estimating the proportion of the white-tailed deer diet comprised of , an invasive shrub with ELP, quantifying the seasonal pattern of deer browse on this invasive shrub, and comparing its nutritional quality to leafless woody stems. In the Miami University Natural Areas in southwest Ohio we quantified the frequency of leafy twigs of woody species 0.3-2.1 m high in three habitats (deciduous forest, forest, and forest-field edge). Monthly we quantified deer browse on marked twigs, and estimated the mass of leaf and stem tissue consumed with allometric relationships using diameter and length of unbrowsed twig portions. We estimated the percent of the annual deer diet comprised of by dividing the sum of these estimates by the product of deer abundance (estimated by pellet-based distance sampling) and consumption estimates from the literature. Crude protein of stems and leaves was determined by C:N analyser. In each habitat the frequency of was greater than all other woody species combined. We estimated comprised 14-47 % of the annual deer diet. Deer browsed each month, but consumption was high in early spring and late summer. Crude protein of leafy twigs of in early spring was 12.9 %, much higher than leafless twigs of native species on-site. These findings support the assumptions of the hypothesis that invasive plants with ELP impact native plants via deer-mediated apparent competition.
有假说认为，具有延长叶物候期（ELP）的入侵植物物种会使多食性食草动物种群数量增加，从而增加对本地植物的食草作用（表观竞争）。该假说假定，对入侵植物的取食与ELP时期有关，入侵植物是食草动物饮食的主要组成部分，并且在ELP时期其比本地植物更具营养价值。我们通过估计白尾鹿饮食中由一种具有ELP的入侵灌木[此处原文缺失该入侵灌木名称]组成的比例、量化鹿对这种入侵灌木的季节性啃食模式，并将其营养质量与无叶木本茎进行比较，来检验这些假设。在俄亥俄州西南部的迈阿密大学自然保护区，我们在三种栖息地（落叶林、[此处原文缺失一种森林类型名称]森林和林缘）中对高度为0.3 - 2.1米的木本物种的带叶嫩枝出现频率进行了量化。每月我们对标记的[此处原文缺失该入侵灌木名称]嫩枝上的鹿啃食情况进行量化，并使用未被啃食嫩枝部分的直径和长度通过异速生长关系估计消耗的叶和茎组织质量。我们通过将这些估计值的总和除以鹿的丰度（通过基于粪便颗粒的距离抽样估计）与文献中的消耗估计值的乘积，来估计鹿全年饮食中由[此处原文缺失该入侵灌木名称]组成的百分比。[此处原文缺失该入侵灌木名称]茎和叶的粗蛋白由碳氮分析仪测定。在每个栖息地，[此处原文缺失该入侵灌木名称]的出现频率高于所有其他木本物种的总和。我们估计[此处原文缺失该入侵灌木名称]占鹿全年饮食的14 - 47%。鹿每月都会啃食[此处原文缺失该入侵灌木名称]，但在早春和夏末啃食量较高。早春时[此处原文缺失该入侵灌木名称]带叶嫩枝的粗蛋白含量为12.9%，远高于当地无叶本地物种的嫩枝。这些发现支持了该假说的假设，即具有ELP的入侵植物通过鹿介导的表观竞争影响本地植物。
