Moore-Kucera Jennifer, Dick Richard P
Department of Horticulture, Oregon State University, Corvallis, OR 97331, USA.
Microb Ecol. 2008 Apr;55(3):500-11. doi: 10.1007/s00248-007-9295-1. Epub 2007 Aug 31.
The impact and frequency of forest harvesting could significantly affect soil microbial community (SMC) structure and functioning. The ability of soil microorganisms to perform biogeochemical processes is critical for sustaining forest productivity and has a direct impact on decomposition dynamics and carbon storage potential. The Wind River Canopy Crane Research Forest in SW, WA, provided a unique opportunity to study a forest chronosequence and the residual effects of harvesting on the SMC in comparison to old-growth forests. The objective of this study was to determine the effect of clear-cutting and stand age on temporal dynamics of SMC and physiological stress markers using phospholipid fatty acid (PLFA) profiling. Soil microbial PLFA profiles were determined seven times over 22 months (Nov. 02 to Sep. 04) in old-growth coniferous forest stands (300-500 years) and 8 (CC8)- or 25 (CC25)-year-old replanted clear-cuts. PLFA patterns of the SMC shifted because of clear-cutting, but seasonal temporal changes had greater shifts than differences among stand age. The microbial biomass (total PLFA) and bacterial, fungal, and selected other PLFAs were significantly reduced in CC8 but not in CC25 sites relative to the old-growth sites. An increase in stress indicators [PLFA ratios of saturated/monsaturated and (cy17:0 + cy19:0)/(16:1omega7 + 18:1omega7)] in late summer was related to water stress. Although the canopy and litter input are quite different for a 25-year clear-cut compared to virgin old-growth forest, we conclude that the composition of the microbial communities, 25 years after clear-cutting, has recovered sufficiently to be much more similar to old-growth forests than a recent clear-cut at this Pacific Northwest forest site. The study shows the potential of PLFA analysis for profiling microbial communities and their stress status under field conditions, but wide temporal shifts emphasize the need for sampling over seasons to fully interpret ecosystem management impacts on microbial populations.
森林采伐的影响和频率可能会显著影响土壤微生物群落(SMC)的结构和功能。土壤微生物进行生物地球化学过程的能力对于维持森林生产力至关重要,并且对分解动态和碳储存潜力有直接影响。华盛顿州西南部的风河树冠起重机研究林提供了一个独特的机会,来研究森林时间序列以及与原始森林相比采伐对SMC的残留影响。本研究的目的是使用磷脂脂肪酸(PLFA)分析来确定皆伐和林分年龄对SMC时间动态和生理应激标志物的影响。在原始针叶林林分(300 - 500年)以及8年(CC8)或25年(CC25)树龄的重新种植的皆伐林地中,在22个月(2002年11月至2004年9月)内进行了七次土壤微生物PLFA分析。由于皆伐,SMC的PLFA模式发生了变化,但季节性时间变化的幅度大于林分年龄之间的差异。相对于原始林地,CC8林地中的微生物生物量(总PLFA)以及细菌、真菌和其他选定的PLFA显著减少,但CC25林地中没有。夏末应激指标[饱和/单不饱和PLFA比率以及(cy17:0 + cy19:0)/(16:1ω7 + 18:1ω7)]的增加与水分胁迫有关。尽管与原始原始森林相比,25年树龄的皆伐林地的树冠和凋落物输入有很大不同,但我们得出结论,皆伐25年后,微生物群落的组成已充分恢复,与该太平洋西北地区森林站点最近的皆伐林地相比,更类似于原始森林。该研究表明了PLFA分析在野外条件下对微生物群落及其应激状态进行分析的潜力,但较大的时间变化强调了需要在多个季节进行采样,以充分解释生态系统管理对微生物种群的影响。