Department of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China.
Phytopathology. 2010 Jun;100(6):593-600. doi: 10.1094/PHYTO-100-6-0593.
Bacterial populations (CFU) have been shown to oscillate in wavelike patterns after nutrient impulses in previous studies. The amplitudes and periods of oscillations could possibly be used as indicators of soil health analogous to the stability and resilience of biological populations widely accepted as indicators for ecosystem health. Limited plant and animal disease outbreaks can also be viewed as a manifestation of a healthy soil ecosystem. Two pot experiments were carried out to verify whether damping-off of beet seedlings by Pythium ultimum, measured as area under the disease progress curve (AUDPC), fluctuated over time after incorporation of organic materials into organic versus conventional soils, and to investigate whether daily dynamics of AUDPCs were linked to the dynamics of microbial populations and chemical parameters. AUDPCs oscillated significantly over time when Pythium bioassays were initiated daily after addition of ground grass and clover shoots (GC) into unplanted soils. Similar oscillations with significant harmonics of AUDPC were also observed in composted manure (CM)-amended soils but with smaller amplitudes than in GC-amended soils. The AUDPC harmonics in amended soils had periods similar to those of CFU of copiotrophic bacteria. Cross-correlation analysis demonstrated that periodic fluctuations of P. ultimum infections (AUDPCs) did not coincide with those of copiotrophic CFU but were shifted in phase. It appears that competition or antagonism from some fast-growing bacteria influenced pathogen infections, because these bacterial populations were growing and dying. Soil chemical variables, including pH, dissolved organic carbon, and NO(3)(-)-N, and NH(4)(+)-N contents, changed significantly in the initial 7 days after a nutrient impulse into soils. These changes were cross-correlated with copiotrophic CFU with time lags of approximately 1 to 2 days but were seldom associated with daily changes in AUDPCs. Organically managed soils always had lower AUDPC ratios of amended to nonamended treatments, indicating that organic materials showed stronger suppressive abilities to P. ultimum in organic than in conventional soils. The oscillations in AUDPCs and copiotrophic CFU in amended organic soil also had smaller amplitudes than in amended conventional soil. These results suggested that organically managed soils had a greater resistance and resilience to the disturbance of the amendments and, therefore, could be considered healthier than conventionally managed soils.
在先前的研究中，已经表明细菌种群（CFU）在受到营养脉冲后会呈波状波动。 振荡的幅度和周期可能可以用作类似于广泛接受的生物种群稳定性和恢复力的土壤健康指标，这些指标被认为是生态系统健康的指标。 有限的植物和动物疾病暴发也可以看作是健康土壤生态系统的表现。 进行了两项盆栽实验，以验证在将有机材料掺入有机与常规土壤中后，由终极腐霉引起的甜菜幼苗猝倒（以病害进展曲线下的面积（AUDPC）衡量）是否随时间波动，以及调查AUDPC 的日动态是否与微生物种群和化学参数的动态有关。 当在添加地面草和三叶草芽（GC）后每天开始进行腐霉生物测定时，AUDPC 随时间显着波动。 在添加了堆肥肥料（CM）的土壤中也观察到了类似的具有显着谐波的 AUDPC 振荡，但幅度比 GC 土壤小。 修饰土壤中 AUDPC 的谐波具有与富营养 CFU 相似的周期。 互相关分析表明，腐霉感染的周期性波动（AUDPC）与富营养 CFU 的波动不一致，而是相位错开。 似乎某些快速生长的细菌的竞争或拮抗作用影响了病原体的感染，因为这些细菌种群正在生长和死亡。 土壤化学变量，包括 pH，溶解有机碳和 NO3（-）-N 和 NH4（+）-N 含量，在养分脉冲进入土壤后的最初 7 天内显着变化。 这些变化与富营养 CFU 随时间的滞后约 1 至 2 天具有交叉相关性，但很少与 AUDPC 的日常变化相关。 有机管理的土壤对添加和未添加处理的 AUDPC 比值总是较低，表明有机材料对有机土壤中的终极腐霉具有比常规土壤更强的抑制能力。 改良有机土壤中 AUDPC 和富营养 CFU 的波动幅度也比改良常规土壤小。 这些结果表明，有机管理的土壤对修正案的干扰具有更大的抵抗力和恢复力，因此可以被认为比常规管理的土壤更健康。
