Data from: Precipitation and environmental constraints on three aspects of flowering in three dominant tallgrass species

Flower production can comprise up to 70% of aboveground primary production in grasslands. Yet we know relatively little about how the environment and timing of rainfall determine flower productivity. Evidence suggests that deficits or additions of rainfall during phenlologically relevant periods (i.e. growth, storage, initiation of flowering, and reproduction) can determine flower production in grasslands.
We used long-term data from the Konza Prairie LTER to test how fire, soil topography, and precipitation amounts during four phenologically relevant periods of the growing season constrain three aspects of flowering in three dominant C4 grass species. Specifically, we examined the probability of flowering, flowering stalk density, and individual flowering stalk biomass for Andropogon gerardii, Schizachyrium scoparium and Sorghastrum nutans.
We found that each of the three species responded to the amount of precipitation during phenologically relevant periods in unique ways. All aspects of A. gerardii flowering were sensitive to precipitation during the flowering stalk elongation period (June 20 – Aug 3). The probability of S. nutans flowering was partly determined by precipitation during the rapid growth phase (April 21 – June 4), whereas flowering stalk density of this species depended on rainfall during flowering stalk elongation (June 20 – Aug 3). In contrast, all aspects of flowering of S. scoparium were relatively independent of rainfall during any period.
Our results demonstrate that three functionally similar, codominant C4 grass species respond differently to phenologically relevant precipitation periods. As a result, drought during any phenological window during the growing season can adversely impact biomass and flowering production of grasslands via species-specific reductions in flowering stalk density and biomass.

草原地上初级生产力中，开花产物占比可达70%之多。然而目前我们对环境与降雨时序如何调控开花生产力的认知仍较为有限。已有研究表明，在与物候相关的关键时段（即生长、储能、开花启动及生殖阶段），降雨的盈亏均可决定草原的开花量。
本研究依托康扎草原长期生态研究站点（Konza Prairie LTER）的长期监测数据，探究火干扰、土壤地形以及生长季内四个物候相关时段的降水量如何制约三种优势C4草本植物的开花表现。具体而言，我们针对大须芒草（Andropogon gerardii）、小须芒草（Schizachyrium scoparium）与拟高粱（Sorghastrum nutans）三个物种，分别考察了其开花概率、花茎密度以及单花茎生物量三个开花相关指标。
研究结果显示，三种草本对物候相关时段降水量的响应模式各具特异性。大须芒草的所有开花指标均对花茎伸长期（6月20日至8月3日）的降水量敏感。拟高粱的开花概率部分受快速生长阶段（4月21日至6月4日）的降水量调控，而其花茎密度则取决于花茎伸长期（6月20日至8月3日）的降雨情况。与之相反，小须芒草的所有开花表现均相对不受任意时段降雨的影响。
本研究结果表明，三种功能性状相似的共优C4草本植物，对物候相关降水时段的响应存在显著差异。由此可见，生长季内任意物候窗口发生的干旱，均可通过物种特异性的花茎密度与单花茎生物量降低，对草原的生物量及开花产出产生负面影响。