Ohtonen Rauni, Fritze Hannu, Pennanen Taina, Jumpponen Ari, Trappe Jim
Department of Biology, University of Oulu, FIN-90571 Oulu, Finland e-mail:
Finnish Forest Research Institute, FIN-01301 Vantaa, Finland, , , , , , FI.
Oecologia. 1999 May;119(2):239-246. doi: 10.1007/s004420050782.
We studied microbial community composition in a primary successional chronosequence on the forefront of Lyman Glacier, Washington, United States. We sampled microbial communities in soil from nonvegetated areas and under the canopies of mycorrhizal and nonmycorrhizal plants from 20- to 80-year-old zones along the successional gradient. Three independent measures of microbial biomass were used: substrate-induced respiration (SIR), phospholipid fatty acid (PLFA) analysis, and direct microscopic counts. All methods indicated that biomass increased over successional time in the nonvegetated soil. PLFA analysis indicated that the microbial biomass was greater under the plant canopies than in the nonvegetated soils; the microbial community composition was clearly different between these two types of soils. Over the successional gradient, the microbial community shifted from bacterial-dominated to fungal-dominated. Microbial respiration increased while specific activity (respiration per unit biomass) decreased in nonvegetated soils over the successional gradient. We proposed and evaluated new parameters for estimating the C use efficiency of the soil microbial community: "Max" indicates the maximal respiration rate and "Acc" the total C released from the sample after a standard amount of substrate is added. These, as well as the corresponding specific activities (calculated as Max and Acc per unit biomass), decreased sharply over the successional gradient. Our study suggests that during the early stages of succession the microbial community cannot incorporate all the added substrate into its biomass, but rapidly increases its respiration. The later-stage microbial community cannot reach as high a rate of respiration per unit biomass but remains in an "energy-saving state," accumulating C to its biomass.
我们研究了美国华盛顿州莱曼冰川前沿原生演替时间序列中的微生物群落组成。我们沿着演替梯度，在20至80年区域的非植被区土壤以及菌根植物和非菌根植物树冠下采集了微生物群落样本。使用了三种独立的微生物生物量测量方法：底物诱导呼吸（SIR）、磷脂脂肪酸（PLFA）分析和直接显微镜计数。所有方法均表明，非植被土壤中的生物量随演替时间增加。PLFA分析表明，植物树冠下的微生物生物量大于非植被土壤中的微生物生物量；这两种土壤类型的微生物群落组成明显不同。在演替梯度上，微生物群落从以细菌为主转变为以真菌为主。在演替梯度上，非植被土壤中的微生物呼吸增加，而比活性（单位生物量的呼吸）降低。我们提出并评估了用于估算土壤微生物群落碳利用效率的新参数：“Max”表示最大呼吸速率，“Acc”表示添加标准量底物后样本释放的总碳量。这些参数以及相应的比活性（以单位生物量的Max和Acc计算）在演替梯度上急剧下降。我们的研究表明，在演替早期，微生物群落无法将所有添加的底物纳入其生物量，但呼吸作用迅速增加。后期的微生物群落单位生物量的呼吸速率无法达到那么高，但保持在“节能状态”，将碳积累到其生物量中。
