Pioneer mosses are among the dominant vegetation in the early stages of xeric successions. Recent climate warming may have a significant effect on the productivity of these mosses, thereby affecting successional processes. In this study, we investigated the effects of temperature changes on the productivity of Racomitrium japonicum, a pioneer moss species commonly found on open ground in Japan. We examined the microclimate (moss temperature and water content) of a natural R. japonicum stand in Higashi-Hiroshima City, western Japan, and related them to the climate records of the weather station to create a model for estimating microclimate from past climatic data. We also examined the effects of environmental factors (light, temperature, and water) on photosynthesis in the laboratory to construct a production model. Using these models, we estimated the net primary production (NPP) over the last 10 years (2009–2018) based on the climatic data (air temperature and precipitation) recorded at the weather station of Higashi-Hiroshima City. The estimated NPP showed negative values in summer, which indicated that respiratory carbon loss exceeded photosynthetic carbon gain. In contrast, NPP was positive in the spring and winter seasons throughout the 10 years. Autumn NPP varied widely, showing both positive and negative values. The annual NPP also showed considerable year-to-year variations. Additionally, we examined the effects of temperature conditions on NPP assuming annual temperature changes of 0 °C (present temperature), + 1 °C, and + 2 °C. The results indicated that NPP decreased with increasing temperature, except in the winter season. The findings of this study suggest that climate warming has a large impact on the NPP of R. japonicum; however, the impact can be both positive and negative depending on the season. The results also suggest that future climate warming is likely to decrease NPP on an annual basis.

先驱苔藓是旱生演替早期的主要植被之一。最近的气候变暖可能对这些苔藓的生产力产生重大影响，从而影响演替过程。在这项研究中，我们调查了温度变化对Racomitrium japonicum生产力的影响，Racomitrium japonicum 是一种在日本空地上常见的先锋苔藓物种。我们检查了天然R. japonicum的小气候（苔藓温度和水分含量）站在日本西部的东广岛市，并将它们与气象站的气候记录相关联，以创建一个模型，用于根据过去的气候数据估算小气候。我们还在实验室中检查了环境因素（光、温度和水）对光合作用的影响，以构建生产模型。使用这些模型，我们根据东广岛市气象站记录的气候数据（气温和降水量）估算了过去 10 年（2009-2018 年）的净初级生产量 ( NPP )。估计的NPP在夏季显示负值，这表明呼吸碳损失超过光合碳增加。相比之下，NPP10年间春冬季节均呈正增长。秋季NPP变化很大，既有正值也有负值。年度NPP也显示出相当大的年度变化。此外，假设年温度变化为 0 °C（当前温度）、+ 1 °C 和 + 2 °C，我们研究了温度条件对NPP的影响。结果表明，除冬季外，NPP随温度升高而降低。本研究结果表明，气候变暖对日本刺参的NPP影响较大; 但是，根据季节的不同，影响可能是正面的，也可能是负面的。结果还表明，未来气候变暖可能会逐年减少NPP 。