PLANT WINNERS AND LOSERS DURING GRASSLAND N-EUTROPHICATION DIFFER IN BIOMASS ALLOCATION AND MYCORRHIZAS
PLANT WINNERS AND LOSERS DURING GRASSLAND N-EUTROPHICATION DIFFER IN BIOMASS ALLOCATION AND MYCORRHIZAS
复制标题
草地富营养化过程中的植物赢家和输家在生物量分配和菌根方面存在差异
DOI：
10.1890/07-1394.1
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发表时间：
2008-10-01
期刊：
影响因子：
4.8
通讯作者：
Allen, Edith B.
中科院分区：
文献类型：
--
作者：
Johnson, Nancy Collins;Rowland, Diane L.;Allen, Edith B.
人类活动向大气中释放大量含氮化合物。干湿沉积将空气中的氮 (N) 分布到原始的生态系统中。这种富营养化过程显着改变了原生草原的物种组成；通常，少数嗜氮植物物种占据主导地位，而许多其他物种则消失。功能平衡模型预测，与对氮富集响应下降的物种相比，嗜硝草物种应对氮富集做出响应，地上生物量分配更大，根和菌根分配减少。菌根反馈假说认为，菌根真菌群落的组成可能会影响植物群落的组成，并预测氮富集可能会导致菌根真菌和植物的物种组成发生相互变化。我们通过比较四种草生态类型（三个物种）的生物量分配和菌根功能的实验来检验这些假设，其中两种生态类型增加了生物量和覆盖率，另两种则减少了生物量和覆盖率，以响应雪松溪和孔扎长期生态研究草原的长期氮富集实验。当地草生态型在各自地点的土壤中生长，并接种从施肥（FERT）或未施肥（UNFERT）地块收集的全土接种物。我们的结果强烈支持功能平衡模型。在这两个草原系统中，嗜氮草种都长得更高，分配给芽的生物量多于根，并且与它所取代的草种相比，形成的菌根更少。我们的结果并不完全支持这样的假设：氮诱导的菌根真菌群落变化是伴随氮富营养化的植物群落变化的驱动因素。 FERT 和 UNFERT 土壤接种物对草的生长的影响不同，但这随着地点和草生态类型的不同而以预期和意外的方式变化，这表明周围土壤肥力或其他因素可能与菌根反馈相互作用。
Human activities release tremendous amounts of nitrogenous compounds into the atmosphere. Wet and dry deposition distributes this airborne nitrogen (N) on otherwise pristine ecosystems. This eutrophication process significantly alters the species composition of native grasslands; generally a few nitrophilic plant species become dominant while many other species disappear. The functional equilibrium model predicts that, compared to species that decline in response to N enrichment, nitrophilic grass species should respond to N enrichment with greater biomass allocation aboveground and reduced allocation to roots and mycorrhizas. The mycorrhizal feedback hypothesis states that the composition of mycorrhizal fungal communities may influence the composition of plant communities, and it predicts that N enrichment may generate reciprocal shifts in the species composition of mycorrhizal fungi and plants. We tested these hypotheses with experiments that compared biomass allocation and mycorrhizal function of four grass ecotypes ( three species), two that gained and two that lost biomass and cover in response to long-term N enrichment experiments at Cedar Creek and Konza Long-Term Ecological Research grasslands. Local grass ecotypes were grown in soil from their respective sites and inoculated with whole-soil inoculum collected from either fertilized (FERT) or unfertilized (UNFERT) plots. Our results strongly support the functional equilibrium model. In both grassland systems the nitrophilic grass species grew taller, allocated more biomass to shoots than to roots, and formed fewer mycorrhizas compared to the grass species that it replaced. Our results did not fully support the hypothesis that N-induced changes in the mycorrhizal fungal community were drivers of the plant community shifts that accompany N eutrophication. The FERT and UNFERT soil inoculum influenced the growth of the grasses differently, but this varied with site and grass ecotype in both expected and unexpected ways suggesting that ambient soil fertility or other factors may be interacting with mycorrhizal feedbacks.