Alexander H M, Mihail J D
Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA e-mail:
Plant Science Unit, 108 Waters Hall, University of Missouri, Columbia, MO 65211, USA, , , , , , US.
Oecologia. 2000 Feb;122(3):346-353. doi: 10.1007/s004420050040.
The effect of seed and seedling mortality on plant population dynamics depends on the degree to which the growth and reproduction of surviving individuals can compensate for the deaths that occur. To explore this issue, we sowed seeds of the annual Kummerowia stipulacea at three densities in sunken pots in the field, which contained either field soil, microwaved field soil, or microwaved field soil augmented with oospores of three Pythium species. High sowing density reduced seedling establishment and seedling size, but these effects were independent of the soil treatment. In the oospore-augmented soil, seed and seedling survival was low. The surviving plants were initially smaller but, at maturity, average plant size was greatest in the oospore-augmented soil, compared to the other treatments. Total population seed production was unaffected by soil treatment, suggesting that the effect of disease was limited to the seedling stage, with surviving plants released from intraspecific competition. To test the hypothesis that the surviving plants in the oospore-augmented soil were more disease-resistant, seeds from each of the sowing density-soil type treatments were sown in a growth chamber inoculation study. No evidence for selection for resistance was found. A second inoculation experiment revealed that oospore inoculum reduced plant numbers and mass regardless of whether field or microwaved soil was used, suggesting that results from the field experiment were not dependent on the use of microwaved soil. The findings of this study indicate that the ecological effects of disease on individual plants and on plant populations are not necessarily equivalent.
种子和幼苗死亡率对植物种群动态的影响取决于存活个体的生长和繁殖能够补偿所发生死亡的程度。为了探究这个问题，我们在田间的下沉花盆中以三种密度播种一年生鸡眼草的种子，花盆中装有田间土壤、经微波处理的田间土壤或添加了三种腐霉菌卵孢子的经微波处理的田间土壤。高播种密度降低了幼苗的定植率和幼苗大小，但这些影响与土壤处理无关。在添加卵孢子的土壤中，种子和幼苗的存活率较低。存活的植株最初较小，但成熟时，与其他处理相比，添加卵孢子的土壤中植株的平均大小最大。土壤处理对种群种子总产量没有影响，这表明病害的影响仅限于幼苗期，存活的植株摆脱了种内竞争。为了检验添加卵孢子的土壤中存活植株更抗病这一假设，在生长室接种研究中播种了每种播种密度 - 土壤类型处理的种子。未发现有选择抗性的证据。第二项接种实验表明，无论使用田间土壤还是经微波处理的土壤，卵孢子接种物都会减少植株数量和生物量，这表明田间实验的结果并不依赖于经微波处理的土壤的使用。本研究结果表明，病害对个体植物和植物种群的生态影响不一定相同。
