Laboratory for Analytical and Environmental Chemistry, Earth System Sciences Research Unit, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussel, Belgium.
Philos Trans R Soc Lond B Biol Sci. 2010 May 12;365(1545):1405-16. doi: 10.1098/rstb.2009.0300.
The idea that entropy production puts a constraint on ecosystem functioning is quite popular in ecological thermodynamics. Yet, until now, such claims have received little quantitative verification. Here, we examine three 'entropy production' hypotheses that have been forwarded in the past. The first states that increased entropy production serves as a fingerprint of living systems. The other two hypotheses invoke stronger constraints. The state selection hypothesis states that when a system can attain multiple steady states, the stable state will show the highest entropy production rate. The gradient response principle requires that when the thermodynamic gradient increases, the system's new stable state should always be accompanied by a higher entropy production rate. We test these three hypotheses by applying them to a set of conventional food web models. Each time, we calculate the entropy production rate associated with the stable state of the ecosystem. This analysis shows that the first hypothesis holds for all the food webs tested: the living state shows always an increased entropy production over the abiotic state. In contrast, the state selection and gradient response hypotheses break down when the food web incorporates more than one trophic level, indicating that they are not generally valid.
在生态热力学中，熵产生对生态系统功能的限制这一观点相当流行。然而，到目前为止，这些说法几乎没有得到定量验证。在这里，我们检验了过去提出的三个“熵产生”假说。第一个假说是，熵产生的增加可以作为生命系统的特征。另外两个假说则提出了更强的限制。状态选择假说指出，当一个系统可以达到多个稳定状态时，稳定状态将显示出最高的熵产生率。梯度响应原理要求当热力学梯度增加时，系统的新稳定状态总是伴随着更高的熵产生率。我们通过将这些三个假说应用于一组常规食物网模型来检验它们。每次，我们计算与生态系统稳定状态相关的熵产生率。这一分析表明，第一个假说适用于所有测试的食物网：生命状态总是比非生命状态具有更高的熵产生率。相比之下，当食物网包含多个营养级时，状态选择和梯度响应假说就失效了，这表明它们并不普遍适用。
