Water‐use advantage for lianas over trees in tropical seasonal forests

Abstract

SummaryLianas exhibit peak abundance in tropical forests with strong seasonal droughts, the ecophysiological 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.

The Responses of Plant Leaf CO2/H2O Exchange and Water Use Efficiency to Drought: A Meta-Analysis

“…Drought had a marked improvement on lianas' WUE, but the effect was not significant for trees, shrubs, and herbs ( Figure 1). The Gs of lianas and trees decreased more than shrubs and herbs, indicating their superior adaptation to drought, as they benefit from strong stomatal control to avoid excessive water loss during water deficits [43]. Lianas had smaller reductions in Pn and Gs (Figure 1) than trees, which is consistent with previous research that they have better access to deep soil water than co-occurring trees [43].…”

“…The Gs of lianas and trees decreased more than shrubs and herbs, indicating their superior adaptation to drought, as they benefit from strong stomatal control to avoid excessive water loss during water deficits [43]. Lianas had smaller reductions in Pn and Gs (Figure 1) than trees, which is consistent with previous research that they have better access to deep soil water than co-occurring trees [43]. Lianas had the largest increase in WUE, suggesting this plant type has an advantage over trees due to a smaller proportional decline in Pn and a larger decline in Tr during drought.…”

Evaluating climber cutting as a strategy to restore degraded tropical forests

“…Natural variation in weather may have a stronger impact on recovery than specific restoration strategies (Garrido-Pérez et al, 2008;Martínez-Garza et al, 2013;Wilson, 2015). Wind damage can be exacerbated by climber cutting (Garrido-Pérez et al, 2008); and water limitation and higher canopy openness resulting from drought events in seasonally dry forests may have strong consequences for the competitive balance between trees and climbers (Chen et al, 2015). Thus, further studies are necessary to understand the consequences of climate change on climber proliferation and their management in forest remnants (Schnitzer and Bongers, 2002).…”

Biodiversity of Lianas

“…The unique distribution of lianas may be explained by the ability of lianas to grow more than competing trees during the dry season, which may confer a competitive advantage for lianas ). This hypothesis is now supported empirically by a number of studies that show that lianas are more physiologically active than trees during the dry season relative to the wet season Zhu and Cao 2009 ;Wyka et al 2013 ;Alvarez-Cansino et al 2015 ;Chen et al 2015 ), and thus the pattern of liana distribution appears to be controlled predominantly by the ability of lianas to grow when their tree competitors are largely dormant. By contrast, lianas may be in much lower abundance in aseasonal, wet forests, where water is rarely limiting and radiation is relatively low year-round, and thus lianas gain no such advantage .…”

“…Lianas also have extraordinarily large vessel elements modifi ed for highly effi cient water movement, which enables them to effectively supply water to their leaves (e.g., Wyka et al 2013 ). Lianas may also have deep and effi cient root and vascular systems, which allow them to acquire more soil water and nutrients and suffer less water-stress during the dry season compared to many tree species (Restom and Nepstad 2004 ;Andrade et al 2005 ;Chen et al 2015 ). Thus, the unique anatomical and physiological traits of lianas may allow them to exploit seasonal forests more effectively than can trees, thus explaining their large-scale, among-forest distribution.…”