Age structure, growth performance and composition of native and invasive Salicaceae in Patagonia
Age structure, growth performance and composition of native and invasive Salicaceae in Patagonia
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DOI：
10.1007/s11258-014-0362-7
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发表时间：
2014-09-01
期刊：
影响因子：
1.7
通讯作者：
Leyer, Ilona
中科院分区：
文献类型：
--
作者：
Thomas, Lisa K.;Leyer, Ilona
在巴塔哥尼亚北部，由于外来植物入侵，河岸生态系统发生了很大变化。非本地柳树和杨树的建立对洪堡柳（该地区唯一的本地洪泛区树种）的影响尚不清楚。为了阐明建立过程并评估杨柳科类群之间是否可能发生种间竞争以及本地物种是否可以长期共存，我们分析了阿根廷里奥内格罗混合成年林中主要四个类群的年龄结构和生长性能。可以检测到 20 个林分内的所有四个类群的平均年龄 < 15 年，这表明频繁和严重的干扰导致现有植被被清除并随后建立了定居点。同一林分的树木表现出相同的年龄结构，表明涉及所有类群的联合建立事件。可以证明入侵柳树具有显着更好的生长性能（断面积、树冠直径）。在总共 88 个研究样地中分别考虑上游和中游，S. humboldtiana 在中游河段更为常见，而入侵柳树则表现出相反的模式，表明下游定向入侵过程。结果表明，成熟混合林中的竞争压力会影响洪堡虎。然而，这些林分通常会被河流动力移除，形成新的沉积坝和岛屿。这些过程使洪堡种子能够频繁发芽，这可以弥补其较差的生长性能和入侵柳树和杨树的潜在影响。
In northern Patagonia, riparian ecosystems are highly modified due to alien plant invasions. The establishment of non-native willows and poplars has unknown effects for Salix humboldtiana, the only native floodplain tree species in this region. To clarify establishment processes and to assess whether interspecific competition among the Salicaceae taxa may occur and therefore whether the native species can coexist in the long term, we analysed age structure and growth performances of the dominant four taxa within mixed adult forest stands along the Rio Negro, Argentina. Low mean ages of < 15 years for all four taxa within 20 stands could be detected and suggest frequent and severe disturbances resulting in the removal of existing vegetation and subsequent creation of sites for establishment. Trees of the same stand showed the same age structure indicating joint establishment events with all taxa involved. A significant better growth performance (basal area, crown diameter) could be proved for the invasive willows. Considering the upper and middle river separately in a total of 88 studied plots, S. humboldtiana was more frequent at the middle river stretch, while invasive willows showed an opposing pattern suggesting a downstream directed invasion process. The results showed that competition pressure in mature mixed stands could affect S. humboldtiana. However, these stands are usually removed by river dynamics creating new sediment bars and islands. These processes enable S. humboldtiana seeds to germinate frequently which may compensate for its inferior growth performance and potential impacts by the invasive willows and poplars.