A comparison of fynbos and non-fynbos coenoclines in the lower Gamtoos River Valley, southeastern Cape, South Africa
A comparison of fynbos and non-fynbos coenoclines in the lower Gamtoos River Valley, southeastern Cape, South Africa
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南非开普省东南部甘图斯河谷下游的凡波斯和非凡波斯共斜岩的比较
DOI：
10.1007/bf00044900
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
B. Campbell
中科院分区：
文献类型：
--
作者：
R. Cowling;B. Campbell
研究了凡波斯山和非凡波斯群岛的结构属性和生长形式的相对重要性模式，以检验前者的结构变化较小的假设，因为低水平土壤养分的压倒性影响将在凡波斯群岛的大量结构趋同中显现出来。共斜层沿着相同的环境梯度排列，即海拔、降雨量和土壤湿度不断增加，气候变化不断减少。结果表明，整个凡波斯共斜植被在结构上是一个小叶硬叶灌木丛，下层是禾本科植物，而上层通常是一个大叶（类蛋白质）灌木。 Fynbos结构在很大程度上被解释为对低水平土壤养分的反应。非凡波斯植被范围从低海拔的混合肉质硬叶和多刺的大叶灌木丛到梯度上端的高大的中生森林。非凡波斯结构是根据土壤湿度和气候的变化来解释的。对共斜线沿线地点样本植物区系的生物地理亲和力的分析表明，凡波斯植被以开普植物空间特有的类群为主，尽管植物空间混合在较低海拔地点很明显。凡波斯群斜层的当地特有程度相对较高；几乎所有特有种都是 Cape fynbos 类群，其发病率随着海拔的升高而增加。这些数据表明，凡波斯植被在开普省东南部有着悠久的历史，高海拔地区可能是开普省类群在不利气候时期的避难所。非凡波斯植被范围从干燥的亚热带汤加兰-庞多兰灌木丛（具有强烈的卡鲁-纳米布成分）到温带非洲山地森林。地方性水平低于凡波斯群斜层，并随着海拔的升高而降低。在低海拔的两个共斜层中发现的大量喀螨特有植物表明，喀螨植被在过去可能更为广泛，可能是在末次冰期期间，当时比现在的全新世间冰期要干燥得多。
Patterns in the relative importance of structural attributes and growth forms along fynbos and non-fynbos coenoclines were studied to test the hypothesis that there would be less structural variation in the former because the overriding influence of low levels of soil nutrients would be manifest in a great deal of structural convergence in fynbos. The coenoclines were ranged along identical environmental gradients of increasing altitude, rainfall and soil moisture and decreasing climatic variability. Results showed that along the entire fynbos coenocline vegetation was structurally a small-leaved sclerophyllous shrubland with a graminoid understorey and, usually, a large-leaved (proteoid) shrub overstorey. Fynbos structure was interpreted largely as a response to low levels of soil nutrients. Non-fynbos vegetation ranged from mixed succulent-sclerophyllous and spiny large-leaved thicket at lower altitudes to tall mesic forest at the upper end of the gradient. Non-fynbos structure was explained in terms of variations in soil moisture and climate. An analysis of the biogeographical affinities of sample floras at sites along the coenoclines showed that fynbos vegetation was dominated by taxa endemic to the Cape phytochorion, although phytochorological mixing was pronounced at the lower altitude sites. The level of local endemism in the fynbos coenocline was relatively high; nearly all endemics were Cape fynbos taxa and their incidence increased with increasing altitude. These data indicate that fynbos vegetation has had a lengthy history in the southeastern Cape and that high altitude sites would have comprised a refuge for Cape taxa during unfavourable climatic periods. Non-fynbos vegetation ranged from dry subtropical Tongaland-Pondoland thicket with a strong Karoo-Namib component to temperate Afromontane forest. Levels of endemism were lower than the fynbos coenocline and decreased with increasing altitude. The high number of karroid endemics found in both coenoclines at low altitudes suggests that karroid vegetation would have been more widespread in the past, probably during the last glacial which was considerably drier than the present Holocene interglacial.