Tsuga, a genus of conifers in the subfamily Abietoideae of the pine family, plays an important role in subalpine and lowland moist coniferous forests as well as broad–leaved forests. Previous studies suggest that Tsuga is a good indicator of climate change and has received wide attention. However, the most important climate variables driving the distribution of Tsuga have not been clearly identified.

In a study published in Ecological Indicators, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and their collaborators sought to identify the climate factors that shape Tsuga's distribution, identify climate thresholds, and elucidate distribution dynamics in the context of significant climate changes over the last 1,070 thousand years.

The researchers applied the maximum entropy (MaxEnt) model by combining Tsuga distribution data with abundant pollen fossil data to estimate the present, past, and future potential distribution regions of the species in East Asia, eastern North America, and western North America.

They found that precipitation was the most crucial climate variable affecting Tsuga distribution, with different regions showing sensitivity to either summer or winter precipitation. The survival of Tsuga was strongly influenced by winter and summer temperatures.

In addition, the seasonal precipitation requirements of Tsuga varied in different regions. In East Asia, summer precipitation and winter temperatures exhibited a strong impact on Tsuga distribution, while winter precipitation, annual precipitation, and winter temperature played key roles in North America, eastern North America, and western North America, respectively.

The result indicated that the decrease in summer precipitation and winter temperature may have led to the extinction of Tsuga in Europe. In East Asia, the potentially suitable area for Tsuga was larger during relatively cold periods. In North America, the potentially suitable area expanded during relatively warm periods.

The researchers suggested that special attention should be paid to monitoring the natural growth status of Tsuga populations. They also suggested tailored conservation approaches, especially ex situ conservation measures, artificial introduction and cultivation.

"It is crucial to prioritize the assessment of the impact of precipitation changes on the distribution of Tsuga," said LI Shufeng of XTBG.