title: Water-use advantage for lianas over trees in tropical seasonal forests.
abstract: Lianas exhibit peak abundance in tropical forests with strong seasonal droughts, the eco-physiological mechanisms associated with lianas coping with water deficits are poorly understood. We examined soil water partitioning, sap flow, and canopy eco-physiological properties for 99 individuals of 15 liana and 34 co-occurring tree species in three tropical forests that differed in soil water availability. In the dry season, lianas used a higher proportion of deep soil water in the karst forest (KF; an area with severe seasonal soil water deficit (SSWD)) and in the tropical seasonal forest (TSF, moderate SSWD), permitting them to maintain a comparable leaf water status than trees in the TSF or a better status than trees in the KF. Lianas exhibited strong stomatal control to maximize carbon fixation while minimizing dry season water loss. During the dry period, lianas significantly decreased water consumption in the TSF and the KF. Additionally, lianas had a much higher maximum photosynthetic rates and sap flux density in the wet season and a lower proportional decline in photosynthesis in the dry season compared with those of trees. Our results indicated that access to deep soil water and strong physiological adjustments in the dry season together with active wet-season photosynthesis may explain the high abundance of lianas in seasonally dry forests.
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla Yunnan, 666303, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Chen
authors.forename: Kun-Fang
authors.initials: KF
authors.lastname: Cao
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Schnitzer
authors.forename: Ze-Xin
authors.initials: ZX
authors.lastname: Fan
authors.forename: Jiao-Lin
authors.initials: JL
authors.lastname: Zhang
authors.forename: Frans
authors.initials: F
authors.lastname: Bongers
mesh_terms: D000704:Analysis of Variance; D002681:China; D002940:Circadian Rhythm / Q000502:physiology; D065928:Forests; D010788:Photosynthesis; D012621:Seasons; D012987:Soil; D014197:Trees / Q000254:growth & development / Q000502:physiology*; D014329:Tropical Climate; D055548:Vapor Pressure; D014867:Water / Q000378:metabolism*
chemical_list: D012987:Soil; D014867:Water
keywords: competition; drought tolerance; dry season growth advantage; sap flow; stable isotope; water relations; water source; water-use efficiency