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Abstract：
In the strongly seasonal, but annually very wet, parts of the tropics, low-water availability in the short dry season leads to a semi-deciduous forest, one which is also highly susceptible to nutrient loss from leaching in the long wet season. Patterns in litterfall were compared between forest with low (LEM) and high (HEM) abundances of ectomycorrhizal trees in Korup National Park, Cameroon, over 26 months in 1990-92. Leaf litter was sorted into 26 abundant species which included six ectomycorrhizal species, and of these three were the large grove-forming trees Microberlinia bisulcata, Tetraberlinia bifoliolata and Tetraberlinia moreliana. Larger-tree species shed their leaves with pronounced peaks in the dry season, whereas other species had either weaker dependence, showed several peaks per year, or were wet-season shedders. Although total annual litterfall differed little between forest types, in the HEM forest (dominated by M. bisulcata) the dry-season peak was more pronounced and earlier than that in the LEMforest. Species differed greatly in their mean leaf litterfall nutrient concentrations, with an approx. twofold range for nitrogen and phosphorus, and 2.5-3.5-fold for potassium, magnesium and calcium. In the dry season, LEM and HEM litter showed similar declines in P and N concentration, and increases in K and Mg; some species, especially M. bisculcata, showed strong dry-wet season differences. The concentration of P (but not N) was higher in the leaf litter of ectomycorrhizal than nonectomycorrhizal species. Retranslocation of N and P was lower among the ectomycorrhizal than nonectomycorrhizal species by approx. twofold. It is suggested that, within ectomycorrhizal groves on this soil low in P, a fast decomposition rate with minimal loss of mineralized P is possible due to the relatively high litter P not limiting the cycle at this stage, combined with an efficient recapture of released P by the surface organic layer of ectomycorrhizas and fine roots. This points to a feedback between two essential controlling steps (retranslocation and mineralization) in a tropical rain forest ecosystem dominated by ectomycorrhizal trees.
摘要：
在强烈的季节性，但是每年都非常潮湿，热带地区的一部分，在短暂的旱季中，水的可利用性低导致半落叶林，在漫长的雨季中，也极易因浸出而失去养分。在Korup国家公园中，比较了低（LEM）和高（HEM）外生菌根树丰度的森林，喀麦隆,1990-92年超过26个月。凋落叶分为26种丰富的物种，其中包括6种外生菌根物种，这三棵是形成大林的树木，双叶四叶和多叶四叶。较大的树种在旱季落叶明显高峰，而其他物种的依赖性较弱，显示每年有几个高峰，或者是雨季的脱落者。尽管森林类型之间的年度垃圾总量差异不大，在HEM森林（以M.bisulcata为主）中，旱季高峰比LEM森林更明显，更早。物种的平均落叶养分浓度差异很大，大约有一个。氮和磷的两倍范围，钾的2.5-3.5倍，镁和钙.在干旱的季节，LEM和HEM凋落物的P和N浓度下降相似，钾和镁的增加；一些物种，尤其是M.bisculcata,表现出强烈的干湿季节差异。外生菌根的凋落物中P（而不是N）的浓度高于非外生菌根。外生菌根物种中N和P的重移位比非外生菌根物种低大约。双重。有人建议,在磷含量低的土壤上的外生菌根林中，一个快速的分解速率与最小的损失的矿化P是可能的，由于相对较高的垫料P不限制周期在这个阶段，结合外生菌根和细根的表面有机层对释放的P的有效捕获。这表明在以外生菌根树为主的热带雨林生态系统中，两个基本控制步骤（重移位和矿化）之间存在反馈。
