Wallander Håkan, Göransson Hans, Rosengren Ulrika
Department of Microbial Ecology, Lund University, 223 62 Lund, Sweden.
Oecologia. 2004 Mar;139(1):89-97. doi: 10.1007/s00442-003-1477-z. Epub 2004 Jan 16.
Nutrient uptake by forest trees is dependent on ectomycorrhizal (EM) mycelia that grow out into the soil from the mycorrhizal root tips. We estimated the production of EM mycelia in root free samples of pure spruce and mixed spruce-oak stands in southern Sweden as mycelia grown into sand-filled mesh bags placed at three different soil depths (0-10, 10-20 and 20-30 cm). The mesh bags were collected after 12 months and we found that 590+/-70 kg ha(-1) year(-1) of pure mycelia was produced in spruce stands and 420+/-160 kg ha(-1) year(-1) in mixed stands. The production of EM mycelia in the mesh bags decreased with soil depth in both stand types but tended to be more concentrated in the top soil in the mixed stands compared to the spruce stands. The fungal biomass was also determined in soil samples taken from different depths by using phospholipid fatty acids as markers for fungal biomass. Subsamples were incubated at 20 degrees C for 5 months and the amount of fungal biomass that degraded during the incubation period was used as an estimate of EM fungal biomass. The EM biomass in the soil profile decreased with soil depth and did not differ significantly between the two stand types. The total EM biomass in the pure spruce stands was estimated to be 4.8+/-0.9 x 10(3) kg ha(-1) and in the mixed stands 5.8+/-1.1 x 10(3) kg ha(-1) down to 70 cm depth. The biomass and production estimates of EM mycelia suggest a very long turnover time or that necromass has been included in the biomass estimates. The amount of N present in EM mycelia was estimated to be 121 kg N ha(-1) in spruce stands and 187 kg N ha(-1) in mixed stands. The delta13C value for mycelia in mesh bags was not influenced by soil depth, indicating that the fungi obtained all their carbon from the tree roots. The delta13C values in mycelia collected from mixed stands were intermediate to values from pure spruce and pure oak stands suggesting that the EM mycelia received carbon from both spruce and oak trees in the mixed stands. The delta15N value for the EM mycelia and the surrounding soil increased with soil depth suggesting that they obtained their entire N from the surrounding soil.
林木对养分的吸收依赖于外生菌根（EM）菌丝体，这些菌丝体从菌根根尖生长到土壤中。我们通过将菌丝体生长到放置在瑞典南部三种不同土壤深度（0 - 10厘米、10 - 20厘米和20 - 30厘米）的装满沙子的网袋中，来估算纯云杉林以及云杉 - 橡树混交林无根样本中外生菌根菌丝体的产量。12个月后收集网袋，我们发现云杉林中纯菌丝体的产量为590±70千克·公顷⁻¹·年⁻¹，混交林中为420±160千克·公顷⁻¹·年⁻¹。两种林分类型中网袋中外生菌根菌丝体的产量均随土壤深度降低，但与云杉林相比，混交林中的产量往往更集中在表层土壤。还通过使用磷脂脂肪酸作为真菌生物量的标志物，测定了从不同深度采集的土壤样本中的真菌生物量。子样本在20℃下培养5个月，将培养期间降解的真菌生物量用作外生菌根真菌生物量的估计值。土壤剖面中的外生菌根生物量随土壤深度降低，两种林分类型之间没有显著差异。到70厘米深度，纯云杉林中的外生菌根总生物量估计为4.8±0.9×10³千克·公顷⁻¹，混交林中为5.8±1.1×10³千克·公顷⁻¹。外生菌根菌丝体的生物量和产量估计表明其周转时间非常长，或者生物量估计中包含了坏死物质。云杉林中，外生菌根菌丝体中的氮含量估计为121千克·公顷⁻¹，混交林中为187千克·公顷⁻¹。网袋中菌丝体的δ¹³C值不受土壤深度影响，表明真菌的所有碳都来自树木根系。从混交林中收集的菌丝体的δ¹³C值介于纯云杉林和纯橡树林的值之间，这表明混交林中的外生菌根菌丝体从云杉和橡树中都获取了碳。外生菌根菌丝体及其周围土壤的δ¹⁵N值随土壤深度增加，表明它们的全部氮都来自周围土壤。
