Data from: Litter removal in a tropical rain forest reduces fine root biomass and production but litter addition has few effects

Many old-growth lowland tropical rain forests are potentially nutrient limited, and it has long been thought that many such forests maintain growth by recycling nutrients from decomposing litter. We investigated this by continuously removing (for ten years) freshly fallen litter from five (45 m x 45 m) plots, adding it to five other plots, there were five controls. From monthly measures over one year we show that litter removal caused lower: fine root (≤2 mm diameter) standing mass, fine root standing length, fine root length production and fine root length survivorship. Litter addition did not significantly change fine root mass or length or production. Nutrient concentrations in fine roots in litter removal plots were lower than those in controls for nitrogen (N), calcium (Ca) and magnesium (Mg), concentrations in fine roots in litter addition plots were higher for N and Ca. Chronic litter removal has resulted in reduced forest growth due to lack of nutrients, probably nitrogen. Conversely, long-term litter addition has had fewer effects.

成熟原始低地热带雨林普遍存在潜在养分限制，长期以来学界普遍认为，多数此类森林依靠分解凋落物（litter）循环获取养分以维持自身生长。为此我们开展了为期十年的野外控制实验：于5块面积为45米×45米的样地中持续移除新鲜凋落物，将移除的凋落物施加至另外5块同规格样地，并设置5块未做处理的对照样地。基于为期一年的月度监测数据，我们发现：凋落物移除会显著降低细根（fine root，直径≤2毫米）的现存生物量、现存根长、根长生产速率以及根长存活率；而凋落物添加则未对细根生物量、根长及细根生产速率产生显著影响。与对照样地相比，凋落物移除样地内细根的氮（N）、钙（Ca）及镁（Mg）养分浓度均显著降低；而凋落物添加样地内细根的氮（N）与钙（Ca）养分浓度则有所升高。长期持续移除凋落物会因养分（大概率为氮素）匮乏导致森林生长量下降；与之相对，长期施加凋落物的生态效应则相对微弱。