Disturbance, resource pulses and invasion: short-term shifts in competitive effects, not growth responses, favour exotic annuals
Disturbance, resource pulses and invasion: short-term shifts in competitive effects, not growth responses, favour exotic annuals
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DOI：
10.1111/j.1365-2664.2011.01988.x
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发表时间：
2011-08-01
影响因子：
5.7
通讯作者：
Callaway, Ragan M.
中科院分区：
文献类型：
--
作者：
Besaw, Levi M.;Thelen, Giles C.;Callaway, Ragan M.
1.增加资源的可用性和资源脉冲往往会促进外来入侵植物的入侵，但增加资源供应的相对重要性与不同的生活史的入侵者可能会有所不同。同样不清楚的是，资源的增加是否会使入侵者的增长超过他们的本土邻居，或者改变竞争的结果。了解不同的入侵生活史对资源供应的反应机制将有助于控制最重要的物种。我们发现，空中下降的野火阻燃剂山间草原提供了一个非常高的脉冲的N和P，并导致显着增加的丰富的年度外来入侵者已经存在于系统中。田间试验表明，延缓剂对外来一年生植物的影响与本地多年生禾草相似，但对本地一年生植物没有影响.在温室试验中，外来种和本地种对阻滞剂的生长反应与平均竞争效应或反应的强度无关。同时，克每克竞争效应差异很大，物种和治疗。N引起的竞争相互作用的强度的变化是更好的预测比生长反应的影响，在该领域的阻滞剂。例如，Centaurea stoebe，一种入侵的多年生杂类草，当单独生长时，比任何其他物种都更倾向于对阻滞剂的反应，但阻滞剂显著地改变了与这种入侵者的竞争结果，有利于外来的一年生植物和本地的丛生草Pseudoroegneria spicata。合成与应用。我们的研究结果表明，一个极端的营养脉冲并没有创造条件，入侵者超过本地邻居或其他外来物种，而是改变了竞争激烈的竞争环境的方式，导致社区组成的相当大的变化。鉴于阻燃剂滴在景观上的微小规模，我们的研究结果并不表明改变阻燃剂用于对抗野火的方式，但确实表明，局部的后阻燃剂杂草控制可能是重要的，使阻燃剂滴不会成为外来入侵的点源。此外，我们的研究结果表明，在高氮条件下，入侵者与年度生活史应优先控制。
1. Increased resource availability and resource pulses often promote invasion by exotic invasive plants, but the relative importance of increased resource supply for invaders with different life histories is likely to vary. It is also unclear whether increased resources allow invaders to outgrow their native neighbours or alter the outcome of competition. Understanding mechanisms by which different invasive life histories respond to resource supply will help to target the most important species to control.2. We found that aerially dropped wildfire retardant on intermountain grassland provided a very high pulse of N and P and caused dramatic increases in the abundance of annual exotic invaders already present in the system. Field experiments with retardant stimulated similar shifts to dominance by exotic annuals and decreases in native perennial grasses, but elicited no responses by native annual species.3. In a greenhouse experiment, the growth response of both exotic and native species to retardant was not related to the intensity of mean competitive effects or responses. Concomitantly, gram per gram competitive effects differed substantially among species and treatments. N-caused shifts in the strength of competitive interactions were far better predictors than growth responses of the effects of retardant in the field. For example, Centaurea stoebe, an invasive perennial forb, grew disproportionally more than any other species in response to retardant when grown alone, but retardant significantly shifted competitive outcomes with this invader in favour of exotic annuals and the native bunch grass Pseudoroegneria spicata.4. Synthesis and applications. Our results indicate that an extreme nutrient pulse did not create conditions whereby invaders outgrew native neighbours or other exotics, but instead altered the competitive playing field in ways that resulted in considerable changes in community composition. Given the minuscule scale of retardant drops on the landscape, our results do not suggest changing the way retardant is used to combat wildfire but do suggest that localized post-retardant weed control may be important so that retardant drops do not become point sources for exotic invasion. Furthermore, our results suggest that under high N conditions, invaders with annual life histories should be prioritized for control.