Photosynthetic tolerance to non-resource stress influences competition importance and intensity in an invaded estuary.
Photosynthetic tolerance to non-resource stress influences competition importance and intensity in an invaded estuary.
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DOI：
10.1002/ecy.2214
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发表时间：
2018-06
期刊：
影响因子：
4.8
通讯作者：
Long Tang;Amelia A. Wolf;Yang Gao;Cheng-Huan Wang
中科院分区：
文献类型：
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作者：
Long Tang;Amelia A. Wolf;Yang Gao;Cheng-Huan Wang
为了阐明环境和生物相互作用对植物生长的作用，关于竞争的强度和重要性是否在环境梯度上稳定、增加或减少，一直存在着长期的生态学争论。在中国河口进行了一个非资源胁迫梯度的实验，研究了土壤盐度（1.4‰ ~ 19.0‰）对原生芦苇和入侵互花米草竞争作用的影响。我们将这些影响与光合活性的测量联系起来，以进一步阐明竞争相互作用和入侵驱动因素背后的潜在生理机制。实验表明，虽然两个物种的生物量在另一个物种的存在下下降，但竞争并没有随着时间的推移改变任何一个物种的光合活性。在低盐条件下，芦苇表现出较高的光合活性，包括较低的叶绿素酶活性、较高的叶绿素含量、较高的气孔导度和较高的净光合速率。在这种条件下，芦苇经历了低竞争强度，导致高生物量生产和竞争排斥S。互花S的情况正好相反。互花米草：随着盐度的增加，芦苇的竞争强度增加，光合活性、生物量、竞争优势度和竞争对芦苇生长的重要性降低; alterniflora稳定。这些结果表明，S。在高盐区，互花米草的入侵很可能发生并扩大。竞争性质的变化沿着非资源压力梯度之间的竞争对手可能由于光合耐盐性的差异而有所不同。随着胁迫水平的增加，较不耐受物种的生长驱动力从竞争变化为非资源胁迫因素，而竞争对于较耐受物种的生长一直很重要。阐明竞争强度和重要性的指标，以及将这些竞争结果与生理机制联系起来，对于理解，预测和调解未来入侵物种的影响至关重要。
In an attempt to clarify the role of environmental and biotic interactions on plant growth, there has been a long-running ecological debate over whether the intensity and importance of competition stabilizes, increases or decreases across environmental gradients. We conducted an experiment in a Chinese estuary to investigate the effects of a non-resource stress gradient, soil salinity (from 1.4‰ to 19.0‰ salinity), on the competitive interactions between native Phragmites australis and invasive Spartina alterniflora. We linked these effects to measurements of photosynthetic activities to further elucidate the underlying physiological mechanism behind the competitive interactions and the driver of invasion. The experiments revealed that while biomass of both species decreased in the presence of the other, competition did not alter photosynthetic activity of either species over time. P. australis exhibited high photosynthetic activity, including low chlorophyllase activity, high chlorophyll content, high stomatal conductance and high net photosynthetic rate, at low salinity. Under these conditions, P. australis experienced low competitive intensity, leading to high biomass production and competitive exclusion of S. alterniflora. The opposite was observed for S. alterniflora: while competitive intensity experienced by P. australis increased with increasing salinity, and photosynthetic activity, biomass, competitive dominance and the importance of competition for P. australis growth decreased, those of S. alterniflora were stable. These findings demonstrate that S. alterniflora invasion driven by competitive exclusion are likely to occur and expand in high salinity zones. The change in the nature of competition along a non-resource stress gradient differs between competitors likely due to differences in photosynthetic tolerance to salinity. The driver of growth of the less-tolerant species changes from competition to non-resource stress factors with increasing stress levels, whereas competition is constantly important for growth of the more-tolerant species. Incorporating metrics of both competition intensity and importance, as well as linking these competitive outcomes with physiological mechanisms, is crucial to understanding, predicting, and mediating the effects of invasive species in the future.