Weak relationships between leaf phenology and isohydric and anisohydric behavior in lowland wet tropical forest trees

Abstract

Wet tropical forest trees display a wide range of leaf phenology dynamics. However, the interrelation between deciduousness, water status, and leaf and stem characteristics have been poorly investigated compared with dry forests. We studied wet forest trees to answer the following questions: (1) do water regulation modes (iso/anisohydric behavior) of evergreen species differ from those found in deciduous species? (2) Does leaf water potential (ΨL) influences leaffall and emergence dynamics? (3) Are leaf and stem characteristics consistent across evergreen and deciduous trees? We evaluated vegetative phenology, ΨL, and leaf and stem characteristics of six evergreen and three deciduous species monthly for 2 yr. Species exhibited different leaffall and emergence dynamics, as well as different water regulation modes, independent of their deciduousness. Thus, the relationship between leaf phenology and water regulation behaviors appears to be a species‐specific property rather than a functional group attribute. ΨL had no direct influence on the dynamics of leaffall and/or emergence, indicating that this process is not modulated by water availability alone. Individual groups of evergreen and deciduous species could not be identified using principal component analysis (PCA), but a decoupling was observed in the leaf and stem economics spectra. The lack of an interrelation between deciduousness and iso/anisohydry, as well as the independence of leaf and stem trade‐offs, emphasizes that more systematic measurements of vegetative phenology and ecophysiological characteristics are necessary to advance our knowledge of leaf habit and water regulation behaviors based on the functional traits of wet forest plants.

Drought and frost resistance vary between evergreen and deciduous Atlantic Forest canopy trees

“…These species did not have hydraulic segmentation (Oliva Carrasco et al 2015) and avoid low temperatures, both mechanisms consistent with their winter deciduousness. The absence of a dry season is likely to promote greater phenological diversity, increasing the possibility of intermediate iso-or anisohydric behaviour (Braga et al 2016) and probably explains the weak relationship between leaf phenology and isohydricity (Fig S4). Thus, brevideciduous species exhibited hydraulic segmentation as evergreens, but also other hydraulic traits such as the safety margin that were similar to the deciduous species.…”

Leaf phenology and morphofunctional variation in Myrcia amazonica DC. (Myrtaceae) in gallery forest and “campo rupestre” vegetation in the Chapada Diamantina, Brazil

“…As such, even with greater transpiration rates, as compared to gallery forest plants, the ''campo rupestre'' population did not demonstrate exceptionally low water potential levels and was able to maintain a high photosynthetic rate. The populations of M. amazonica demonstrated seasonal variations in their W, suggesting anisohydric behavior, exhibiting stomatal sensitivity to seasonal evaporative demands and soil humidity without, however, show rigid control of W during the year (Martinez-Vilalta et al 2014;Braga et al 2016). In addition to the extremes of isohydry (plants whose tight control of transpiration allows constant seasonal W values) and anisohydry, a third manner of water status regulation was proposed based on the premise that anisohydric species can also demonstrate isohydrodynamic behavior.…”

“…Studies of morphofunctional traits have examined leaf renewal, leaf age, and wood density associated with habitat heterogeneity (Goulart et al 2005;Lemos Filho et al 2008;Toledo et al 2012;Capuzzo et al 2012). Attributes such as phenology, leaf age, gas exchange, photosynthetic pigments, water potential, wood density, and leaf morphological attributes (thicknesses, succulence, density, and leaf mass per area) have been correlated with environmental conditions such as irradiance, VPD, and water balance (Rosado and de Mattos 2007;Meinzer et al 2009;Rosado et al 2013;Rossatto et al 2013;Braga et al 2016).…”

Isotopic composition of leaf carbon (δ13C) and nitrogen (δ15N) of deciduous and evergreen understorey trees in two tropical Brazilian Atlantic forests

“…This site has a gently undulating topography ranging from sea level to 370 m asl. The vegetation of the 1900-mm site is classified as lowland wet forest (Braga et al 2016). The soil is dystrophic red-yellow podzolic with sandy clay texture (Lima et al 2011).…”