Monsoon forests in north-western Australia. II : Forest-savanna transitions
Monsoon forests in north-western Australia. II : Forest-savanna transitions
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澳大利亚西北部的季风森林。
DOI：
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发表时间：
1992
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通讯作者：
D. Bowman
中科院分区：
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作者：
D. Bowman
应用划分分类程序TWINSPAN对144个样带上1000多个样方(10°20m)的树种有无数据进行了分析，以确定湿季风林、交错带和稀树大草原的湿润或干燥组合。排序表显示，这6个植被类型之间存在连续的区系变化，尽管乔木物种丰富度在不同组合之间差异极大。与周围稀树草原相比，干湿季风林具有更高的树干密度、更大的断面积、更多的树种、更高的凋落物盖度和更低的草地盖度。湿润季风林土壤的水分显著高于周围稀树草原，但在干燥季风林-稀树草原边界上，土壤水分没有显著差异。湿润和干燥的季风林土壤都比周围稀树草原的土壤肥沃，尽管这两个林层内部和之间的养分浓度有很大的差异。与稀树大草原相比，森林的肥力更高可能反映了更好的营养积累，而不是表明季风林仅限于天然肥沃的地点。一半的湿润季风林边界具有分隔森林和稀树草原的交错带样方，而只有18%的干燥季风林边界具有这样的结构和区系中间样方。研究发现，湿润和干燥森林交错带的树种数量有限。与毗邻的森林相比，潮湿的森林交错带总体上更接近于周围的稀树草原。干旱森林交错带在环境上介于干燥森林和稀树草原之间。与周围的热带大草原相比，潮湿和干燥的森林造成的火灾损失都较小。与大多数湿润季风林的土壤控制不同，干燥森林通常仅限于防火壁龛。在没有土壤或地形不连续的边界上，干湿林、交错带和稀树草原的分布被认为反映了这些组合之间的动态关系。
Presence-absence data for tree species in over 1000 quadrats, 10 ° 20m, on 144 transects were analysed by the divisive classificatory program TWINSPAN in order to define wet or dry monsoon forest, ecotone and savanna assemblages. A sorted table revealed that there was continuous floristic variation among these six vegetation types, although the abundance of tree species varied highly significantly between assemblages. Both wet and dry monsoon forests have higher stem densities, greater basal area, more tree species, higher litter cover and lower grass cover than surrounding savannas. Wet monsoon forest soils have significantly more moisture than surrounding savanna, but on the dry monsoon forest-savanna boundary there is no significant difference in soil moisture. Both wet and dry monsoon forest soils are more fertile than those in surrounding savannas, although there is considerable variation in the concentration of nutrients within and between the two forest formations. The greater fertility of the forest probably reflects superior nutrient accretion compared with the savanna, rather than indicating that monsoon forests are restricted to inherently fertile sites. Half the wet monsoon forest boundaries sampled had ecotonal quadrats separating forest from savanna, while only 18% of the dry monsoon forest boundaries had such structurally and floristically intermediate quadrats. A limited number of tree species was found to dominate both wet and dry forest ecotones. Wet forest ecotones are overall environmentally more similar to the surrounding savanna than the adjoining forests. Dry forest ecotones are environmentally intermediate between the dry forest and savanna. Both wet and dry forests have less fire damage than surrounding savannas. In contrast to the edaphic control of most wet monsoon forests, dry forests are typically restricted to fire protected niches. The distribution of both wet and dry forest, ecotone and savanna on boundaries with no edaphic or topographic discontinuities is thought to reflect a dynamic relationship between these assemblages.