Contrasting effects of nitrogen availability on plant carbon supply to mycorrhizal fungi and saprotrophs -: a hypothesis based on field observations in boreal forest
Contrasting effects of nitrogen availability on plant carbon supply to mycorrhizal fungi and saprotrophs -: a hypothesis based on field observations in boreal forest
复制标题
DOI：
10.1046/j.1469-8137.2003.00867.x
复制
发表时间：
2003-10-01
期刊：
影响因子：
9.4
通讯作者：
Högberg, P
中科院分区：
文献类型：
--
作者：
Högberg, MN;Bååth, E;Högberg, P
土壤微生物被认为是碳限制的，而植物生产力通常是氮限制的。北方森林土壤中大量的有机碳是由于低温、土壤酸度和植物残体对微生物活性的负面影响。我们研究了沿着90 m长的天然土壤供氮梯度上的微生物活性、生物量和群落组成。在该梯度上，植物种类组成变化很大，森林生产力变化3倍，土壤pH变化3个单位。然而，在土壤中，微生物活性、生物量和群落组成都有显著的差异。在整个梯度的领域土壤呼吸没有显着的变化。也没有微生物量C测定熏蒸提取变化，而其他估计的活动和生物量显示出微弱的增加，增加氮供应和土壤pH值。同时，磷脂脂肪酸主要归因于菌根真菌急剧下降，而细菌生物量增加。我们假设，低氮供应和植物生产力，因此，低凋落物C供应腐养生物与高植物C供应菌根真菌，而相反发生在高N供应。这应该意味着，氮的供应对这些功能群的微生物碳的影响作用在相反的方向。
Soil microorganisms are considered C-limited, while plant productivity is frequently N-limited. Large stores of organic C in boreal forest soils are attributed to negative effects of low temperature, soil acidity and plant residue recalcitrance upon microbial activity.We examined microbial activity, biomass and community composition along a natural 90-m-long soil N supply gradient, where plant species composition varies profoundly, forest productivity three-fold and soil pH by three units.There was, however, no significant variation in soil respiration in the field across the gradient. Neither did microbial biomass C determined by fumigation-extraction vary, while other estimates of activity and biomass showed a weak increase with increasing N supply and soil pH. Simultaneously, a phospholipid fatty acid attributed mainly to mycorrhizal fungi declined drastically, while bacterial biomass increased.We hypothesize that low N supply and plant productivity, and hence low litter C supply to saprotrophs is associated with a high plant C supply to mycorrhizal fungi, while the reverse occurs under high N supply. This should mean that effects of N availability on C supply to these functional groups of microbes acts in opposing directions.