Moisture-Limited Tree Growth for a Subtropical Himalayan Conifer Forest in Western Nepal

Chir pine (Pinus roxburghii Sarg.) is a common tree species with ecological and economic importance across the subtropical forests of the central Himalayas. However, little is known about its growth response to the recent warming and drying trends observed in this region. Here, we developed a 268-year-long ring-width chronology (1743–2010) from western Nepal to investigate its growth response to climate. Based on nearby available meteorological records, growth was positively correlated with winter (November to February; r = 0.39, p r = 0.67, p r = 0.65, p r = −0.48, p < 0.05) suggests the influence of warming-induced evapotranspiration on tree growth. Spring droughts lasting 4–6 months constrain Chir pine growth. These results are supported by the synchronization between droughts and very narrow or locally missing rings. Warming and drying tendencies during winter and spring will reduce forest growth and resilience and make Chir pine forests more vulnerable and at higher risk of growth decline and dieback.This work was supported by the National Natural Science Foundation of China (41661144040 and 41525001). S.R.S. was supported by the Chinese Academy of Sciences President’s International Fellowship Initiative (2018PC0040). B.D. was supported by the Open Research Fund of Key Laboratory of Tibetan Environmental Changes and Land Surface Processes, Chinese Academy of Sciences. E.L. was supported by China Scholarship Council (201704910338). J.J.C. thanks the support of the CGL2015-69186-C2-1-R project (Spanish Ministry of Economy)