Spatial variation in tree demography associated to domestic herbivores and topography: Insights from a seeding and planting experiment
Spatial variation in tree demography associated to domestic herbivores and topography: Insights from a seeding and planting experiment
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与家养食草动物和地形相关的树木人口统计的空间变化：来自播种和种植实验的见解
DOI：
10.1016/j.foreco.2014.09.036
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发表时间：
2015
影响因子：
3.7
通讯作者：
A. Cingolani
中科院分区：
文献类型：
--
作者：
D. Renison;M. Chartier;M. Menghi;P. Marcora;R. C. Torres;M. Giorgis;I. Hensen;A. Cingolani
热带和亚热带高山森林主要位于峡谷内。两种替代的，往往面临的解释已提出这种模式：非生物环境条件有利于树木建立只有在沟壑，或沟壑较少受到放牧和火灾的负面影响，建立在其他网站。在这里，我们提出了一个混合的解释和假设，非生物的环境条件与空间变化是重要的，在早期幼苗建立和放牧是主要的决定因素，在后期阶段，通过其负面影响的生存和生长的较大的树苗。我们在科尔多瓦山脉上游（阿根廷中部）的三个对比鲜明的地点（一个峡谷、一个山谷和一个山脊）播种了302,400粒种子，种植了360株优势树种的树苗。我们监测播种地块5年，直到幼苗达到种植树苗的高度，我们监测种植树苗12年。我们使用矩阵乘法整合了生命阶段，这导致了模拟17年树木早期发育的数据。结果表明，由于仅在河谷放牧，沟谷和山脊地的幼苗建植率较低，河谷地的幼苗建植率较高，差异为负。种植树苗生存增加，但增长下降，从峡谷到山谷和山脊网站在没有大型食草动物，而生存和增长大幅降低，在大型食草动物的存在。矩阵乘法表明，网站之间的差异是5.0倍，更重要的是放牧时，整合到第5年，但放牧的大型草食动物是5.4倍，更重要的是在整个17年期间进行评估时，网站之间的差异。我们的结论是，有可能是一个强大的影响，放牧限制高山地森林的网站，如峡谷，大型食草动物不太频繁，并显示如何相对重要性的网站特性和放牧的变化，作为一个结果的长度和不同的生命阶段的监测。
Tropical and subtropical high mountains forests are mainly situated within ravines. Two alternative and often confronted explanations have been proposed for this pattern: that abiotic environmental conditions are favourable for tree establishment only within ravines, or that ravines are less affected by grazing and fires which negatively affect establishment in other sites. Here we propose a mixed explanation and hypothesize that abiotic environmental conditions associated to spatial variation are important during early seedling establishment and that grazing is the main determinant during later stages through its negative effect on survival and growth of larger saplings. We sowed 302,400 seeds and planted 360 saplings of the dominant tree species from the upper Córdoba Mountain range (Central Argentina) with and without grazing in three contrasting sites: a ravine, a valley and a ridge. We monitored seeding plots 5 years until the seedlings reached the height of the planted saplings and we monitored the planted saplings for 12 years. We integrated life stages using matrix multiplications, which resulted in data simulating 17 years of the trees’ early development. Our results showed that seedling establishment was lower in the ravine and ridge sites and higher in the valley site with negative differences due to grazing only in the valley. Planted sapling survival increased but growth decreased from ravine to valley and ridge sites in the absence of large herbivores, while both survival and growth were substantially lower in the presence of large herbivores. Matrix multiplications indicated that differences between sites were 5.0 times more important than grazing when integrating up to year 5, but grazing by large herbivores was 5.4 times more important than differences between sites when assessed across the whole 17 year period. We conclude that there could be a strong influence of grazing in restricting high montane forests to sites like ravines where large herbivores are less frequent and show how the relative importance of site characteristics and grazing changes as a result of the length and the differing life stages which are monitored.