Climate drives phenological reassembly of a mountain wildflower meadow community.
Climate drives phenological reassembly of a mountain wildflower meadow community.
复制标题
气候驱动山地野花草甸群落的物候重组。
作者：
Elli J. Theobald;Ian K. Breckheimer;J. HilleRisLambers
由物种丰度或栖息地占用变化驱动的空间群落重组是对人为全球变化的一种有据可查的反应，但如果环境驱动群落成员之间生活事件时间的差异性变化，群落也可以暂时重组。与空间群落重组非常相似，当关键物种相互作用在时间上集中时（例如开花期间的植物传粉者动态），时间重组可能特别重要。先前的研究已经记录了气候变化驱动的物种特异性物候变化，这意味着时间重组（我们称之为“物候重组”的过程）是可能的。然而，很少有研究记录环境变化驱动的社区成员时间共现的变化，这可能是因为整个社区的数据集很少存在。我们通过量化分布在雷尼尔山陡峭环境梯度的大型地块网络中雷尼尔山（美国华盛顿）共生的 48 种亚高山野花物种的开花物候与气候之间的关系来解决这一差距；我们研究的六年（包括有记录的最早和最晚的融雪年份）气候的巨大时空变化为各个物种的气候物候关系提供了可靠的估计。我们利用这些关系来研究 2015 年我们站点经历的“气候变化模拟”条件所驱动的群落共花组成的变化。我们发现重点物种的开花时间和持续时间对多种气候因素（融雪、温度和土壤湿度）非常敏感。出现了一些一致的反应，包括更早的融雪和更温暖的生长季节，推动所有焦点物种更早地开花。然而，物种间物候对这些气候驱动因素的敏感性差异足够大，以至于在2015年的气候变化模拟条件下发生了物候重组。物候重组的一个意想不到的驱动因素是气候变化方向和幅度的细尺度变化，导致物候重组在季节的早期和晚期以及积雪持续时间最短的地形位置（即低海拔和景观中的山脊）最为明显。由于物候重组可能对多种类型的生态相互作用产生影响，因此未能监测物种特定物候变化对群落层面的影响可能会低估气候变化的影响。
Spatial community reassembly driven by changes in species abundances or habitat occupancy is a well-documented response to anthropogenic global change, but communities can also reassemble temporally if the environment drives differential shifts in the timing of life events across community members. Much like spatial community reassembly, temporal reassembly could be particularly important when critical species interactions are temporally concentrated (e.g., plant-pollinator dynamics during flowering). Previous studies have documented species-specific shifts in phenology driven by climate change, implying that temporal reassembly, a process we term "phenological reassembly," is likely. However, few studies have documented changes in the temporal co-occurrence of community members driven by environmental change, likely because few datasets of entire communities exist. We addressed this gap by quantifying the relationship between flowering phenology and climate for 48 co-occurring subalpine wildflower species at Mount Rainier (Washington, USA) in a large network of plots distributed across Mt. Rainier's steep environmental gradients; large spatio-temporal variability in climate over the 6 yr of our study (including the earliest and latest snowmelt year on record) provided robust estimates of climate-phenology relationships for individual species. We used these relationships to examine changes to community co-flowering composition driven by 'climate change analog' conditions experienced at our sites in 2015. We found that both the timing and duration of flowering of focal species was strongly sensitive to multiple climatic factors (snowmelt, temperature, and soil moisture). Some consistent responses emerged, including earlier snowmelt and warmer growing seasons driving flowering phenology earlier for all focal species. However, variation among species in their phenological sensitivities to these climate drivers was large enough that phenological reassembly occurred in the climate change analog conditions of 2015. An unexpected driver of phenological reassembly was fine-scale variation in the direction and magnitude of climatic change, causing phenological reassembly to be most apparent early and late in the season and in topographic locations where snow duration was shortest (i.e., at low elevations and on ridges in the landscape). Because phenological reassembly may have implications for many types of ecological interactions, failing to monitor community-level repercussions of species-specific phenological shifts could underestimate climate change impacts.