USDA-ARS, Grassland, Soil, and Water Research Laboratory, Temple, TX, USA.
Department of Biology, University of North Florida, Jacksonville, FL, USA.
Glob Chang Biol. 2018 Apr;24(4):1771-1781. doi: 10.1111/gcb.14032. Epub 2018 Jan 28.
Continuing enrichment of atmospheric CO may change plant community composition, in part by altering the availability of other limiting resources including soil water, nutrients, or light. The combined effects of CO enrichment and altered resource availability on species flowering remain poorly understood. We quantified flowering culm and ramet production and biomass allocation to flowering culms/ramets for 10 years in C -dominated grassland communities on contrasting soils along a CO concentration gradient spanning pre-industrial to expected mid-21st century levels (250-500 μl/L). CO enrichment explained up to 77% of the variation in flowering culm count across soils for three of the five species, and was correlated with flowering culm count on at least one soil for four of five species. In contrast, allocation to flowering culms was only weakly correlated with CO enrichment for two species. Flowering culm counts were strongly correlated with species aboveground biomass (AGB; R = .34-.74), a measure of species abundance. CO enrichment also increased soil moisture and decreased light levels within the canopy but did not affect soil inorganic nitrogen availability. Structural equation models fit across the soils suggested species-specific controls on flowering in two general forms: (1) CO effects on flowering culm count mediated by canopy light level and relative species AGB (species AGB/total AGB) or by soil moisture effects on flowering culm count; (2) effects of canopy light level or soil inorganic nitrogen on flowering and/or relative species AGB, but with no significant CO effect. Understanding the heterogeneity in species responses to CO enrichment in plant communities across soils in edaphically variable landscapes is critical to predict CO effects on flowering and other plant fitness components, and species potential to adapt to future environmental changes.
大气 CO 持续富集可能会改变植物群落组成，部分原因是改变了其他限制资源的可利用性，包括土壤水分、养分或光照。CO 富集和改变资源可利用性对物种开花的综合影响仍知之甚少。我们在 CO 浓度梯度（从工业化前到预计 21 世纪中叶水平，跨度为 250-500μl/L）的不同土壤上，对 10 年来以 C 为主的草原群落中 10 个物种的开花茎和分株产量以及开花茎/分株的生物量分配进行了量化。CO 富集解释了 5 个物种中 3 个物种开花茎计数变化的 77%，并且与 5 个物种中的 4 个物种的至少一个土壤上的开花茎计数相关。相比之下，分配给开花茎的与 CO 富集的相关性仅对两个物种较弱。开花茎计数与物种地上生物量（AGB；R =.34-.74）密切相关，这是物种丰度的一个衡量标准。CO 富集还增加了冠层内的土壤水分并降低了光照水平，但不影响土壤无机氮的可用性。跨土壤拟合的结构方程模型表明，开花存在两种特定物种的控制形式：（1）通过冠层光照水平和相对物种 AGB（物种 AGB/总 AGB）或通过土壤水分对开花茎计数的影响来介导 CO 对开花茎计数的影响；（2）冠层光照水平或土壤无机氮对开花和/或相对物种 AGB 的影响，但 CO 无显著影响。了解土壤中植物群落中物种对 CO 富集的反应异质性，对于预测 CO 对开花和其他植物适应成分的影响以及物种适应未来环境变化的潜力至关重要。
