Who will win where and why? An ecophysiological dissection of the competition between a tropical pasture grass and the invasive weed Bracken over an elevation range of 1000 m in the tropical Andes
Who will win where and why? An ecophysiological dissection of the competition between a tropical pasture grass and the invasive weed Bracken over an elevation range of 1000 m in the tropical Andes
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DOI：
10.1371/journal.pone.0202255
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发表时间：
2018-08-13
期刊：
影响因子：
3.7
通讯作者：
Scheibe, Renate
中科院分区：
文献类型：
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作者：
Knuesting, Johannes;Brinkmann, Marie Clara;Scheibe, Renate
在热带农业中，生长旺盛的蕨类植物入侵牧场，与普通牧草竞争，造成严重问题。由于受到这种杂草的侵扰，牧场在几年后就会被遗弃，其致命的后果是，生物多样性丰富的热带森林逐渐被清理出来，成为新的放牧区。在这里，我们提出了两种植物的广泛的生理比较，这两种植物是热带厄瓜多尔安第斯草原上的主要竞争对手，种植的饲草狗尾草和杂草蕨菜(Pteridium Arachnoideum)。研究区的卫星数据表明，随着海拔的升高，蕨类植物的竞争力增强。利用野外测量数据，在海拔1800~2800m的海拔梯度上模拟了两种植物的年生物量生产量，以衡量它们的竞争力。模型表明，随着海拔的升高，两种植物的生物量生产量向蕨类植物转移，在1800m以上，蕨类植物的生物量能够超过草的生长。在温室试验中，分别分析了海拔梯度、温度和紫外线辐射等假定的关键变量对植物生长的影响。与C3植物蕨菜相比，低温和紫外线照射对C4植物的碳素吸收的抑制作用更强。蕨类植物对温度较不敏感的光合作用及其对紫外线辐射的有效保护有助于高原牧场杂草的成功。蕨菜而狗尾草的田间样品中，作为紫外线清除剂的类黄酮含量随着海拔的升高而增加。将模拟与温室和田间测量相结合，可以解释一种常见杂草在旱地牧场的入侵生长。狗尾草的性能随着海拔的升高而下降，这是由于较低温度下的次优光合作用以及无法适应其细胞紫外线屏蔽。
In tropical agriculture, the vigorously growing Bracken fern causes severe problems by invading pastures and out-competing the common pasture grasses. Due to infestation by that weed, pastures are abandoned after a few years, and as a fatal consequence, the biodiversity-rich tropical forest is progressively cleared for new grazing areas. Here we present a broad physiological comparison of the two plant species that are the main competitors on the pastures in the tropical Ecuadorian Andes, the planted forage grass Setaria sphacelata and the weed Bracken (Pteridium arachnoideum). With increasing elevation, the competitive power of Bracken increases as shown by satellite data of the study region. Using data obtained from field measurements, the annual biomass production of both plant species, as a measure of their competitive strength, was modeled over an elevational gradient from 1800 to 2800 m. The model shows that with increasing elevation, biomass production of the two species shifts in favor of Bracken which, above 1800 m, is capable of outgrowing the grass. In greenhouse experiments, the effects on plant growth of the presumed key variables of the elevational gradient, temperature and UV radiation, were separately analyzed. Low temperature, as well as UV irradiation, inhibited carbon uptake of the C4-grass more than that of the C3-plant Bracken. The less temperature-sensitive photosynthesis of Bracken and its effective protection from UV radiation contribute to the success of the weed on the highland pastures. In field samples of Bracken but not of Setaria, the content of flavonoids as UV-scavengers increased with the elevation. Combining modeling with measurements in greenhouse and field allowed to explain the invasive growth of a common weed in upland pastures. The performance of Setaria decreases with elevation due to suboptimal photosynthesis at lower temperatures and the inability to adapt its cellular UV screen.