Département de biologie, Université de Sherbrooke, Sherbrooke (Qc), J1K 2R9, Canada.
Ann Bot. 2022 Jan 8;129(1):29-36. doi: 10.1093/aob/mcab121.
In 2019, Daou and Shipley produced an operational definition of 'generalized' soil fertility (FG) for plant community ecology and quantified FG using a structural equation model (SEM) invoking a single latent variable. We evaluate a critical assumption of this model: that FG is generalizable to any combination of plant species; i.e. that any combination of plant species will respond in the same direction to the soil 'fertility' gradient in terms of growth.
We grew nine widely different species singly in each of 25 soils from southern Quebec, Canada, whose FG value had been previously quantified. The original SEM was tested using every possible combination involving from four to nine species.
The assumption was rejected due to a subset of three species that responded to a second latent dimension. We then proposed an alternative model that includes FG plus a second latent variable that measures species' deviations from FG due to specific adaptations to soil pH. This alternative model was consistent with every combination of up to eight species. The predictions of FG when ignoring this second dimension and when using the new model were extremely correlated (r =0.98).
The initial unidimensional model of Daou and Shipley was successful in non-acid soils but not in soils with extreme pH and when species specifically adapted to such extreme soils were included. The alternative two-dimensional model takes into account these exceptions and is consistent with the notion of shared physiological niche responses along a gradient of generalized soil fertility.
2019 年，Daou 和 Shipley 为植物群落生态学提出了“广义土壤肥力（FG）”的操作定义，并使用结构方程模型（SEM）量化了 FG，该模型调用了一个单一的潜在变量。我们评估了该模型的一个关键假设：FG 可推广到任何植物物种组合；即任何植物物种组合将根据生长方面的土壤“肥力”梯度以相同的方向做出响应。
我们在加拿大魁北克省南部的 25 种土壤中单独种植了 9 种广泛不同的物种，这些土壤的 FG 值此前已被量化。原始 SEM 利用涉及 4 到 9 种物种的每种可能组合进行了测试。
由于三个物种的子集对第二个潜在维度做出响应，该假设被拒绝。然后，我们提出了一种替代模型，该模型包括 FG 加上第二个潜在变量，该变量用于测量物种由于特定的土壤 pH 适应性而偏离 FG 的程度。该替代模型与多达 8 种物种的所有组合都一致。当忽略第二个维度和使用新模型时，FG 的预测非常相关（r=0.98）。
Daou 和 Shipley 的初始单维模型在非酸性土壤中是成功的，但在 pH 值极端的土壤中和包含专门适应此类极端土壤的物种时则不然。替代的二维模型考虑到了这些例外情况，并与沿着广义土壤肥力梯度共享生理生态位响应的概念一致。
