Agroecology Institute, College of Life Sciences, Zhejiang University, Zijingang campus, Hangzhou, China.
Mycorrhiza. 2011 May;21(4):269-77. doi: 10.1007/s00572-010-0331-5. Epub 2010 Jul 21.
The biomass-density relationship (whereby the biomass of individual plants decreases as plant density increases) has generally been explained by competition for resources. Arbuscular mycorrhizal fungi (AMF) are able to affect plant interactions by mediating resource utilization, but whether this AMF-mediated interaction will change the biomass-density relationship is unclear. We conducted an experiment to test the hypothesis that AMF will shift the biomass-density relationship by affecting intraspecific competition. Four population densities (10, 100, 1,000, or 10,000 seedlings per square meter) of Medicago sativa L. were planted in field plots. Water application (1,435 or 327.7 mm/year) simulated precipitation in wet areas (sufficient water) and arid areas (insufficient water). The fungicide benomyl was applied to suppress AMF in some plots ("low-AMF" treatment) and not in others ("high-AMF" treatment). The effect of the AMF treatment on the biomass-density relationship depended on water conditions. High AMF enhanced the decrease of individual biomass with increasing density (the biomass-density line had a steeper slope) when water was sufficient but not when water was insufficient. AMF treatment did not affect plant survival rate or population size but did affect absolute competition intensity (ACI). When water was sufficient, ACI was significantly higher in the high-AMF treatment than in the low-AMF treatment, but ACI was unaffected by AMF treatment when water was insufficient. Our results suggest that AMF status did not impact survival rate and population size but did shift the biomass-density relationship via effects on intraspecific competition. This effect of AMF on the biomass-density relationship depended on the availability of water.
生物量-密度关系（即个体植物的生物量随着植物密度的增加而减少）通常可以通过资源竞争来解释。丛枝菌根真菌（AMF）能够通过调节资源利用来影响植物的相互作用，但这种 AMF 介导的相互作用是否会改变生物量-密度关系尚不清楚。我们进行了一项实验，以测试 AMF 通过影响种内竞争来改变生物量-密度关系的假设。将四个种群密度（每平方米 10、100、1000 或 10000 株紫花苜蓿）的紫花苜蓿种植在野外小区。浇水（1435 或 327.7 毫米/年）模拟了湿润地区（水分充足）和干旱地区（水分不足）的降水。杀菌剂苯菌灵被用于抑制一些小区中的 AMF（“低 AMF”处理），而不在其他小区中使用（“高 AMF”处理）。AMF 处理对生物量-密度关系的影响取决于水分条件。在水分充足的情况下，高 AMF 增强了个体生物量随密度增加而减少的趋势（生物量-密度线斜率更大），但在水分不足的情况下则没有。AMF 处理不影响植物存活率或种群大小，但确实影响绝对竞争强度（ACI）。在水分充足的情况下，高 AMF 处理的 ACI 明显高于低 AMF 处理，但在水分不足时，AMF 处理对 ACI 没有影响。我们的结果表明，AMF 状态不会影响存活率和种群大小，但会通过对种内竞争的影响来改变生物量-密度关系。AMF 对生物量-密度关系的这种影响取决于水分的可利用性。
