In a study published in Tree Physiology, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences tried to evaluate how lianas differ in their ecological adaptation strategies when facing habitats with contrasting precipitation.
The researchers conducted a comparison of 25 leaves and stem traits concerning leaf anatomy, morphology, physiology, and stem hydraulics for 36 liana species from two contrasting habitats, 17 from a tropical seasonal rainforest in Xishuangbanna, and 19 from a valley savanna ecosystem in Yuanjiang, Yunnan Province, Southwest China.
They found that savanna lianas exhibited a relatively conservative (slow) resource (water and nutrient) use strategy (e.g., higher leaf dry matter content, wood density, vessel density, carbon isotope composition (δ13C), photosynthetic water use efficiency, the ratio of nitrogen to phosphorus).
In contrast, rainforest lianas showed a relatively acquisitive (fast) strategy (higher phosphorus, hydraulically weighted vessel diameter, theoretical hydraulic conductivity, leaf size, nitrogen, and potassium).
Moreover, the associations among water-related traits were found to be tighter in savanna than in rainforest lianas, suggesting a stronger limitation of water supply to the trait. Savanna lianas are able to regulate water transport and use water more efficiently than tropical seasonal rainforest lianas.
Surprisingly, savanna and rainforest lianas did not differ in either area-based or mass-based light-saturated photosynthetic rates. Conservative water and nutrient use of savanna lianas did not result in lower photosynthetic carbon assimilation.
The results revealed that the ecological strategies of lianas differed in habitats with contrasting water availability.
Zhang Jiaolin, principal investigator of the study said, enhanced water and nutrient use efficiencies might have contributed to the ecological success of lianas in dry and hot habitats like savanna ecosystems.
Yun-Bing Zhang et al, Higher water and nutrient use efficiencies in savanna than in rainforest lianas result in no difference in photosynthesis, Tree Physiology (2021). DOI: 10.1093/treephys/tpab099