Rangeland vegetation in the Great Basin, United States, is frequently disturbed by natural- and human-caused wildfires that facilitate the establishment and dominance of introduced annual weeds such as cheatgrass (Bromus tectorum) and medusahead wildrye (Taeniatherum caput-medusae [L.] Nevski). Ecological resilience and resistance of native and seeded-non-native plant communities in this region, however, appear to follow topographic patterns associated with slope, aspect, and elevation. Currently, resistance and resilience concepts are being used to prioritize rangeland restoration efforts based on soil-climate classification. We hypothesized that probabilistic patterns of shorter-term weather effects on seedbed microclimate might also be correlated with these perceived spatial patterns of resistance and resilience over space. We used a 39-yr gridded weather dataset to estimate seedbed temperature and water potential at seeding depth as a function of slope and aspect using the Simultaneous Heat and Water (SHAW) model. Seedbed temperature and water potential were then used as input to hydrothermal germination response models to generate indices of seedbed favorability for initial germination and emergence and to estimate cumulative germination response as a function of topography and planting date for the very-fast-germinating cheatgrass, fast-germinating bottlebrush squirreltail (Elymus elymoides [Raf] Swezey), and slower-germinating Idaho fescue (Festuca idahoensis Elmer). Topographic mapping of seedbed favorability showed distinct seasonal patterns associated with both slope and aspect. Southern exposures are likely to facilitate both prewinter germination for early-fall-planted seeds and relatively more midwinter germination for seeds planted later in the fall, but these exposures are also less subject to midwinter frost effects. Northern exposures were likely to delay germination into later winter and early spring and thus avoid potential exposure to a higher probability of winter frost mortality. Microclimatic simulations of this type may provide new metrics for improving our understanding of the mechanistic causes of observed patterns of ecological resistance and resilience over space.

美国大盆地的牧场植被经常受到自然和人为引起的野火的干扰，这些野火促进了引入的一年生杂草的建立和优势地位，如杂草（Bromus tectorum）和medusahead wildrye（Taeniatherum caput-medusae [L.] Nevski）。但是，该地区本地和种子非本地植物群落的生态适应力和抗逆性似乎遵循与坡度，坡向和海拔相关的地形格局。当前，基于土壤-气候分类，抗性和复原力概念被用于优先进行牧场恢复工作。我们假设短期天气对苗床小气候的影响的概率模式也可能与这些感知的空间抗性和复原力空间模式相关。我们使用39年的网格天气数据集，使用“同时加热和水（SHAW）”模型，根据坡度和坡向估算播种深度的苗床温度和水势。Elymus elymoides [Raf] Swezey）和发芽较慢的爱达荷州羊茅（Festuca idahoensis）Elmer）。苗床适宜性的地形图显示出与坡度和坡度相关的不同季节模式。南方暴露可能促进早秋播种的种子在冬季前发芽，而秋季晚些时候播种的种子则促进相对更多的仲冬发芽，但是这些暴露也较少受到仲冬霜冻的影响。北方暴露很可能将发芽推迟到冬季的晚些时候和春末，从而避免潜在的暴露，从而使冬季霜冻死亡的可能性更高。这种类型的微气候模拟可能会提供新的度量标准，以提高我们对观测到的生态抗性和空间弹性模式的机理的理解。