图4. 双稳态植被格局及植物-微生物互惠共生的作用。a、b为植被斑块的景观图, 其中互惠共生类型A和B (在这种情况下, 丛枝菌根与外生菌根植物)的丰富度表示为色块的灰度。a所呈现的景观中, 双稳态植被状态是存在的, 一块植被要么是A主导要么是B主导, 而b则是两种互惠共生类型的随机混合。c、d互惠共生关系的分布可以用从beta分布中提取的5,000个随机数(代表5,000个景观斑块)的频率分布来说明:$f(y:\mu, phi)=cy^{\mu\varphi-1} (1-y)^{(1-\mu)\varphi-1}$ (y表示A的百分比, μ作为集中趋势, ?为离散系数)。c图所示的双峰大体可以描绘a图色块的频率分布, 而d图的单峰分布可以描绘b图色块的频率分布。e图表示A和B的初始成分(小点)随着时间的推移而分化成两种不同的稳定状态(大点, 紫色表示EMF, 绿色表示AMF)。图c、d、e摘自Lu和Hedin (2019)。

Fig. 4. Bistable vegetation patterns and the role of plant-microbe mutualism. a, b. An illustration of a landscape with patches of vegetation, where the abundance of mutualistic interaction A and B (in this case, Arbuscular mycorrhizal vs. ectomycorrhizal symbioses) is denoted by the darkness of the gray hue. a presents a landscape where bistable vegetation states is found where you either find a patch of vegetation extremely high or extremely low in one type of mutualism, whereas b has a mixture of both mutualistic type in each patch. c, d. The distribution of mutualist abundance can be illustrated using the frequency distribution of 5,000 random numbers (representing 5,000 landscape patches) drawn from a beta distribution: $f(y:\mu, phi)=cy^{\mu\varphi-1} (1-y)^{(1-\mu)\varphi-1}$ (y indicates percentage of A, μ as the central tendency, and ? as the dispersion coefficient). e. Patches that have different founding composition (small dots) of A and B will over time diverge into two alternative stable states (larger dot, EMF indicated in purple and AMF indicated in green). Panels c, d, e are reproduced from figures published in Lu & Hedin (2019).