Zeller B, Colin-Belgrand M, Dambrine E, Martin F, Bottner P
INRA, Centre de Nancy, Ecosystémes Forestiers, 54280 Champenoux, France e-mail:
CNRS-UPR 8481 CEFE, Bp 5051, F-34033 Montpellier, France, , , , , , FR.
Oecologia. 2000 Jun;123(4):550-559. doi: 10.1007/PL00008860.
The decomposition and the fate of N- labelled beech litter was monitored in a beech forest (Vosges mountains, France) over 3 years. Circular plots around beech trees were isolated from neighbouring tree roots by soil trenching. After removal of the litter layer, N-labelled litter was distributed on the soil. Samples [labelled litter, soil (0-15 cm depths], fine roots, mycorrhizal root tips, leaves) were collected during the subsequent vegetation periods and analysed for total N and N concentration. Mass loss of the N-labelled litter was estimated using mass loss data from a litterbag experiment set up at the field site. An initial and rapid release of soluble N from the decomposing litter was balanced by the incorporation of exogenous N into the litter. Fungal N accounted for approximately 35% of the N incorporation. Over 2 years, litter N was continuously released and rates of N and mass loss were equivalent, while litter N was preferentially lost during the 3rd year. Released N accumulated essentially at the soil surface. N from the decomposing litter was rapidly (i.e. in 6 months) detected in roots and beech leaves and its level increased regularly and linearly over the course of the labelling experiment. After 3 years, about 2% of the original litter N had accumulated in the trees. N budgets indicated that soluble N was the main source for soil microbial biomass. Nitrogen accumulated in storage compounds was the main source of leaf N, while soil organic N was the main source of mycorrhizal N. Use of N-labelled beech litter as decomposing substrate allowed assessment of the fate of litter N in the soil and tree N pools in a beech forest on different time scales.
在一片山毛榉森林（法国孚日山脉）中，对氮标记的山毛榉凋落物的分解及归宿进行了为期3年的监测。通过土壤挖沟，将山毛榉树周围的圆形地块与相邻树根隔离开来。去除凋落物层后，将氮标记的凋落物分布在土壤上。在随后的植被生长期间采集样本[标记凋落物、土壤（0 - 15厘米深度）、细根、菌根根尖、树叶]，并分析总氮和氮浓度。利用在该田间地点设置的凋落物袋实验的质量损失数据，估算氮标记凋落物的质量损失。分解的凋落物中可溶性氮的初始快速释放，通过向凋落物中掺入外源氮来平衡。真菌氮约占氮掺入量的35%。在两年时间里，凋落物氮持续释放，氮和质量损失速率相当，而在第三年，凋落物氮优先损失。释放的氮主要在土壤表层积累。在根和山毛榉树叶中迅速（即6个月内）检测到来自分解凋落物的氮，并且在标记实验过程中其含量有规律地线性增加。3年后，约2%的原始凋落物氮积累在了树木中。氮预算表明，可溶性氮是土壤微生物生物量的主要来源。储存化合物中积累的氮是叶片氮的主要来源，而土壤有机氮是菌根氮的主要来源。使用氮标记的山毛榉凋落物作为分解底物，能够在不同时间尺度上评估山毛榉森林中凋落物氮在土壤和树木氮库中的归宿。
