The Importance of Biologically Relevant Microclimates in Habitat Suitability Assessments

Predicting habitat suitability under climate change is vital to conserving biodiversity. However, current species distribution models rely on coarse scale climate data, whereas fine scale microclimate data may be necessary to assess habitat suitability and generate predictive models. Here, we evaluate disparities between temperature data at the coarse scale from weather stations versus fine-scale data measured in microhabitats required for a climate-sensitive mammal, the American pika (Ochotona princeps). We collected two years of temperature data in occupied talus habitats predicted to be suitable (high elevation) and unsuitable (low elevation) by the bioclimatic envelope approach. At low elevations, talus surface and interstitial microclimates drastically differed from ambient temperatures measured on-site and at a nearby weather station. Interstitial talus temperatures were frequently decoupled from high ambient temperatures, resulting in instantaneous disparities of over 30°C between these two measurements. Microhabitat temperatures were also highly heterogeneous, such that temperature measurements within the same patch of talus were not more correlated than measurements at distant patches. An experimental manipulation revealed that vegetation cover may cool the talus surface by up to 10°C during the summer, which may contribute to this spatial heterogeneity. Finally, low elevation microclimates were milder and less variable than typical alpine habitat, suggesting that, counter to species distribution model predictions, these seemingly unsuitable habitats may actually be better refugia for this species under climate change. These results highlight the importance of fine-scale microhabitat data in habitat assessments and underscore the notion that some critical refugia may be counterintuitive.气候变化背景下的栖息地适宜性预测，对于生物多样性保护至关重要。然而，当前的物种分布模型（species distribution models）多依赖粗尺度气候数据，而评估栖息地适宜性并构建预测模型时，或许需要细尺度的微气候数据。本研究针对对气候敏感的哺乳动物北美鼠兔（Ochotona princeps）所需的微生境，对比了气象站获取的粗尺度温度数据与微生境中实测的细尺度温度数据之间的差异。我们在经生物气候包络法（bioclimatic envelope approach）判定为适宜（高海拔）与不适宜（低海拔）的已占用碎石堆生境中，收集了为期两年的温度数据。在低海拔区域，碎石堆表面与间隙的微气候与现场及附近气象站测得的环境温度差异显著。碎石堆间隙的温度常与高温环境温度脱节，导致二者的瞬时温差超过30℃。微生境温度还呈现极强的空间异质性：同一碎石堆斑块内的温度测量值之间的相关性，并不高于远距离斑块间的温度测量值。一项操控实验表明，夏季植被覆盖可使碎石堆表面降温最高达10℃，这或许是造成该空间异质性的原因之一。最后，低海拔区域的微气候相较于典型高山生境更为温和且波动更小，这意味着与物种分布模型的预测相悖，在气候变化背景下，这些看似不适宜的生境，实则可能成为该物种的优质避难所。本研究结果凸显了细尺度微生境数据在栖息地评估中的重要性，同时也印证了一个观点：部分关键避难所的存在可能与直觉相悖。