Bell Colin W, Acosta-Martinez Veronica, McIntyre Nancy E, Cox Stephen, Tissue David T, Zak John C
Department of Biological Sciences, Texas Tech University, Lubbock, TX, 79409-3131, USA.
Microb Ecol. 2009 Nov;58(4):827-42. doi: 10.1007/s00248-009-9529-5. Epub 2009 May 23.
Global and regional climate models predict higher air temperature and less frequent, but larger precipitation events in arid regions within the next century. While many studies have addressed the impact of variable climate in arid ecosystems on plant growth and physiological responses, fewer studies have addressed soil microbial community responses to seasonal shifts in precipitation and temperature in arid ecosystems. This study examined the impact of a wet (2004), average (2005), and dry (2006) year on subsequent responses of soil microbial community structure, function, and linkages, as well as soil edaphic and nutrient characteristics in a mid-elevation desert grassland in the Chihuahuan Desert. Microbial community structure was classified as bacterial (Gram-negative, Gram-positive, and actinomycetes) and fungal (saprophytic fungi and arbuscular mycorrhiza) categories using (fatty acid methyl ester) techniques. Carbon substrate use and enzymic activity was used to characterize microbial community function annually and seasonally (summer and winter). The relationship between saprophytic fungal community structure and function remained consistent across season independent of the magnitude or frequency of precipitation within any given year. Carbon utilization by fungi in the cooler winter exceeded use in the warmer summer each year suggesting that soil temperature, rather than soil moisture, strongly influenced fungal carbon use and structure and function dynamics. The structure/function relationship for AM fungi and soil bacteria notably changed across season. Moreover, the abundance of Gram-positive bacteria was lower in the winter compared to Gram-negative bacteria. Bacterial carbon use, however, was highest in the summer and lower during the winter. Enzyme activities did not respond to either annual or seasonal differences in the magnitude or timing of precipitation. Specific structural components of the soil microbiota community became uncoupled from total microbial function during different seasons. This change in the microbial structure/function relationship suggests that different components of the soil microbial community may provide similar ecosystem function, but differ in response to seasonal temperature and precipitation. As soil microbes encounter increased soil temperatures and altered precipitation amounts and timing that are predicted for this region, the ability of the soil microbial community to maintain functional resilience across the year may be reduced in this Chihuahuan Desert ecosystem.
全球和区域气候模型预测,下个世纪干旱地区的气温将升高,降水事件虽会减少但规模会增大。尽管许多研究探讨了干旱生态系统中气候变化对植物生长和生理反应的影响,但较少有研究关注干旱生态系统中土壤微生物群落对降水和温度季节性变化的反应。本研究考察了湿润年份(2004年)、平均年份(2005年)和干旱年份(2006年)对奇瓦瓦沙漠中海拔荒漠草原土壤微生物群落结构、功能及相互关系,以及土壤土壤性质和养分特征后续反应的影响。利用(脂肪酸甲酯)技术将微生物群落结构分为细菌(革兰氏阴性菌、革兰氏阳性菌和放线菌)和真菌(腐生真菌和丛枝菌根)类别。每年和季节性地(夏季和冬季)利用碳底物利用和酶活性来表征微生物群落功能。腐生真菌群落结构与功能之间的关系在各季节保持一致,与任何给定年份内降水的规模或频率无关。每年较凉爽的冬季真菌对碳的利用超过较温暖的夏季,这表明土壤温度而非土壤湿度强烈影响真菌的碳利用以及结构和功能动态。丛枝菌根真菌和土壤细菌的结构/功能关系在不同季节显著变化。此外,冬季革兰氏阳性菌的丰度低于革兰氏阴性菌。然而,细菌对碳的利用在夏季最高,冬季较低。酶活性对降水规模或时间的年度或季节性差异均无反应。在不同季节,土壤微生物群落的特定结构成分与总微生物功能脱节。微生物结构/功能关系的这种变化表明,土壤微生物群落的不同成分可能提供相似的生态系统功能,但对季节性温度和降水的反应不同。随着土壤微生物面临该地区预计会出现的土壤温度升高、降水数量和时间变化,奇瓦瓦沙漠生态系统中土壤微生物群落全年维持功能恢复力的能力可能会降低。