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CAS Workshop on Ecosystem Succession Theory and Practice of Ecological Restoration 生态恢复过程中的多样性、复杂性与稳定性 常杰
葛滢 （浙江大学生命科学学院，杭州310012） 摘要：生物多样性与生态系统稳定性之间的关系是经过大量讨论的长盛不衰的论题。在两种对立的观点中，多样性导致稳定性是比较传统的观念，但多样性与稳定性无关甚至负相关这一新观点由于反潮流，更加吸引人。持这个观点的一些人甚至认为以往的多样性导致稳定性的观点是迎合保护生物学的需要，或是为生态宣传服务的。如果新观点正确，那末对于恢复生态学来说，不必追求高的生物多样性就能够得到更稳定的生态系统，甚至保持较低的生物多样性反而更加有利，恢复生态就比现在考虑的简单得多；但是如果新假说是错误的，那么其危害性很强：阻碍生态恢复的正确方向和损害全球的生物多样性。最近30年来，多样性与稳定性无关甚至负相关的观点由于有模型和试验支持，似乎越来越占上风。然而事实的确像新观点那样吗？我们发现，尽管新假说看来更加有理论和实验支持，但存在认识误区，本文从三个方面对此进行批驳。 （1）多样性和复杂性概念的准确定位。支持多样性与稳定性无关甚至负相关观点模型研究表明，在一定范围内，随着系统中组分联结的增加，系统稳定性增强，但超过一定程度时，完全联结组分再增加会导致系统稳定性降低。一些人由此推断系统的稳定性随着系统复杂性的增加而降低。这是对复杂性的理解错误造成的：按照系统科学理论，具有同样多样性的系统可能有不同程度的复杂性，系统组分联结程度很低和很高时系统的结构复杂性都低，在组分中度联系状态复杂性最高。这反证了复杂性与稳定性正相关的论点系统的稳定性的变化趋势恰好与复杂性一致。我们的假说是：系统的状态与多样性没有直接关系，而与复杂性直接相关，因而应该以复杂性-稳定性关系取代目前的多样性-稳定性关系研究。 （2）对于稳定性和干扰的准确理解。有些观点认为像热带雨林这样多样性高的复杂的系统完全被砍伐后的恢复比温带和寒冷森林这些多样性低的生态系统的恢复缓慢和困难，所以推论为多样性并不导致稳定性。但实际上这种完全去掉生态系统基本结构的方式不再是通常意义上的干扰，而应该称为移除。此时的恢复是指生态系统的再生能力，而不是通常意义上系统的稳定性恒定性和弹性。从轻微干扰到完全移除，生态系统恢复能力的变化是非线性的，并且在临界点上下发生突变（catastrophe）。复杂性高的系统在临界点以上的恢复能力高于复杂性低的系统，而在临界点以下的再生能力低于复杂性低的系统。 （3）多样性与复杂性之间有共同趋势。虽然从理论上推理系统可能有多样性高、组分联系过强导致复杂性低的状态，但在现实的自然生态系统中，高多样性往往导致生态位分化细致，内生隔离导致复杂性增加，因而高多样性通常具有高复杂性。人工生态系统或人类强度控制的生态系统有可能出现组分联系过少或过多导致复杂性降低的情况，从而降低系统的稳定性。 综上所述，在生态恢复中，提高一个地区的多样性仍然是十分重要的。需要注意的是在人工配置系统时，系统组分的连结需要一定时间才能建成，需要促进其联系，但也不能人为的使系统组分联结过于紧密，从而保持高的复杂性和稳定性。 关键词：生物多样性；生态复杂性；生态恢复；突变；再生 On the biodiversity, eco-complexity and the
stability of ecosystem in ecological restoration Chang
Jie Ge Ying (College of Life Science, Zhejiang University, Hangzhou 310012, China) Abstract: The debate on the
relationship between biodiversity and stability of ecosystem deepens
recently. Between the two viewpoints, higher levels of biodiversity
benefits to ecosystem stability is the early one, now it challenged
by a new view, which said theres no relationship between
biodiversity and ecosystem stability, or high diversity even cause
instability. If the new view is right, it means that the ecological
restoration and the conservation biology become easy and, the
decrease of global biodiversity is not a disaster. While if it is
wrong, it will produce great harmful influence. Although the new
view seems support by models and experiment, but we find it confuse
in concepts of diversity, complexity and stability,
here we debate the view by three points. 1. The correct understanding of biodiversity and
complexity. One base of the new view in model is the stability of
the ecosystem increase with the linking of the components (such as
species) increasing, but turn to decrease after the linking
intensity too strong afterward, so it was deduced that the stability
of an ecosystem do not relate to diversity directly. That is an
incorrect understanding on the concepts of diversity and complexity,
according to systematic theory, same diversity can have
different complexity in a system, and structural complexity is
maximized when part of the nodes linked. It means that the
stability and complexity has the same trend. It cannot deduce the
relationship between diversity and stability from the models like
this. 2. The correct understanding of stability and disturbance. Disturbance and stability are not the linear properties, catastrophe occurs as the intensity of disturbance change, and the stability response to disturbance is nonlinear, from constancy/resistant stability to regeneration after a critical point when disturbance intensity to the ecosystem from low to high. For the resistant stability, higher complex ecosystem > lower one, but it contract for the regeneration ability, i.e. lower complex ecosystem > higher one.
3. Theres similar trend between complexity and diversity.
Although it can be deduced that high diversity may has low
complexity theoretically, while in actual world, the ecosystem with
higher diversity almost always have higher complexity by means of
identification, mainly biological isolation. However,
high diversity with low complexity may occur in the artificial or
strongly controlled ecosystem by human being.
According the priciples above, it is important to rebuilt
high biodiversity in ecological restoration. While it should avoid
the components have neither too weak nor too strong linking when we
restore an ecosystem, so as to keep high complexity and stability. Key words:
biodiversity; complexity; ecological restoration; catastrophe;
regeneration
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