Division of Biology, Kansas State University, Manhattan, Kansas 66506, USA.
Ecology. 2010 Jul;91(7):2132-40. doi: 10.1890/09-1242.1.
The flowering of grasses is a process critical to plant population dynamics and genetics, herbivore performance, and human health. To better understand the climate factors governing grass flowering, we analyzed the patterns of culm production over 25 years for three perennial tallgrass prairie species at Konza Prairie in Kansas, USA. The three species (Andropogon gerardii, Sorghastrum nutans, and Schizachyrium scoparium) all utilize the C4 photosynthetic pathway and were measured annually at the same locations for the past 25 years in an annually burned watershed. Culm production of all three species increased with higher growing-season soil moisture and precipitation but differed in their responses to water availability at different times during the growing season. Relative to Andropogon, Sorghastrum responded more to precipitation early in the growing season, and Schizachyrium responded more to precipitation late in the growing season. Flowering by each species also revealed a threshold relationship with late-season soil moisture at approximately 1 m depth, which likely is a proxy for season-long water balance. Although flowering can be influenced by conditions antecedent to the current growing season, neither soil moisture nor precipitation during the previous year influenced flowering over the 25-year period. Flowering culm production averaged 9% and 7% of total graminoid aboveground net primary production (ANPP) in the uplands and lowlands, respectively. Interannual variation in ANPP correlated only with Sorghastrum flowering, suggesting a predominant role of the species in ANPP responses to climate.
草本植物的开花过程对植物种群动态和遗传学、食草动物的表现以及人类健康至关重要。为了更好地理解控制草本植物开花的气候因素，我们分析了美国堪萨斯州 Konza 草原三种多年生高草草原物种 25 年来茎秆产量的模式。这三种物种（Andropogon gerardii、Sorghastrum nutans 和 Schizachyrium scoparium）均利用 C4 光合作用途径，在过去的 25 年中，每年在同一地点、每年燃烧的流域中进行测量。所有三种物种的茎秆产量都随着生长季节土壤湿度和降水的增加而增加，但对生长季节不同时间水分供应的反应不同。与 Andropogon 相比，Sorghastrum 对生长季节早期的降水反应更敏感，而 Schizachyrium 对生长季节后期的降水反应更敏感。每种物种的开花也显示出与生长季节后期土壤湿度（约 1 米深）的阈值关系，这可能是长期水分平衡的代表。尽管开花可能受到当前生长季节之前条件的影响，但在前一年中，无论是土壤湿度还是降水都没有在 25 年的时间内影响开花。开花茎秆产量分别占高地和低地地上净初级生产力（ANPP）的 9%和 7%。ANPP 的年际变化仅与 Sorghastrum 的开花相关，表明该物种在 ANPP 对气候的响应中起着主要作用。
