Biotic- and abiotic-driven variations of the night-time sap flux of three co-occurring tree species in a low subtropical secondary broadleaf forest

Although several studies on the night-time water use of different plant species have been reported, comparative studies under the same climatic conditions of a region are scarce. A recent study by Wang et al. published in AoB PLANTS aimed to analyse the inter- and intra-specific variations in night-time water use in relation to environmental factors and to tree morphological features.

The authors used Granier-style sap flux sensors to monitor the sap flow of three co-occurring tree species in a low subtropical secondary broadleaf forest in South China. All examined environmental factors except wind speed exerted significant influence on the daytime sap flows of Schima superba, Castanopsis hystrix and Michelia macclurei, but the impacts of all factors, including wind speed, on the night-time sap flux were trivial. The morphological features of the trees, except tree height, significantly affected the daytime water use, but no morphological features significantly affected the night-time water use. A principal component analysis showed that there were more intra-specific than inter-specific variations in water transport. The results also indicated that sap flow was mainly used for water recharge at night, and that night-time water use and the percentage of night/day (Q_n/Q_d) of photosynthetic stem species (Castanopsis. hystrix and Michelia. macclurei) were greater than those of non-photosynthetic stem species (Schima. superba).