Long-term oscillations in grassland productivity induced by drought
Long-term oscillations in grassland productivity induced by drought
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DOI：
10.1046/j.1461-0248.2002.00293.x
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发表时间：
2002-01-01
期刊：
影响因子：
8.8
通讯作者：
Knops, JMH
中科院分区：
文献类型：
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作者：
Haddad, NM;Tilman, D;Knops, JMH
干旱等干扰对生态系统功能有直接影响，但对干扰的长期动态后果知之甚少。在这里，我们发现一次大干旱干扰了草原草地的平均年产量，并引起了9年的振荡，周期为2年。这种模式出现在未被操纵的人类实验中。这是两项长期研究的一部分。通过直接和间接的测试，我们可以否定振荡是由气候或食草动物外部施加的假设。微弱的证据支持振荡是内部产生的假设，由凋落物和氮依赖于生产力的反馈引起。这一假设得到了另外两项长期研究的结果的支持，其中燃烧和分别添加氮消除了植物生产中的2年振荡。然而，更直接的证据未能支持凋落物假说。最后，但未经验证的假设是由观察提出的生产倾向于同步在优势植物之间。干旱可能使植物间的生产动态同步；每两年更大的分配给地上的增长。无论具体的机制如何，我们的研究结果表明，单一的干扰可能对植物生产的动态产生长期的影响。
Disturbances such as drought have immediate impacts on ecosystem functioning, but little is known about long-term dynamic consequences of disturbance. Here, we show that a major drought perturbed prairie grassland from nearly constant average annual production, and induced 9 years of oscillations with a 2-year period. This pattern occurred in unmanipulated plots in man. widely separated fields that were part of two different long-term studies. Using direct and indirect tests, we could reject the hypothesis that the oscillations were externally imposed by climate or herbivores. Weak evidence supported the hypothesis that oscillations were internally generated, caused by a litter and nitrogen dependent feedback on productivity, This hypothesis was supported by the results of two other long-term studies, in which burning and, separately, nitrogen addition eliminated the 2-year oscillations in plant production. However, more direct evidence failed to support the litter hypothesis. A final, but untested hypothesis was suggested by the observation that production tended to be synchronized amongst dominant plants. Drought may have synchronized production dynamics amongst plant,; with biennially greater allocation to above-ground growth. Regardless of the specific mechanism, our results show that a single disturbance may have long-lasting effects on the dynamics of plant production.