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Summary Conifers prevail in the canopies of many terrestrial biomes, holding a great ecological and economic importance globally. Current increases in temperature and aridity are imposing high transpirational demands and resulting in conifer mortality. Therefore, identifying leaf structural determinants of water use efficiency is essential for predicting physiological impacts due to environmental variation.Using synchrotron‐generated microtomography imaging, we extracted leaf volumetric anatomy and stomatal traits in 34 species across conifers with a special focus onPinus, the richest conifer genus.We show that intrinsic water use efficiency (WUEi) is positively driven by leaf vein volume. Needle‐like leaves ofPinus, as opposed to flat leaves or flattened needles of other genera, showed lower mesophyll porosity, decreasing the relative mesophyll volume. This led to increased ratios of stomatal pore number per mesophyll or intercellular airspace volume, which emerged as powerful explanatory variables, predicting both stomatal conductance and WUEi.Our results clarify how the three‐dimensional organisation of tissues within the leaf has a direct impact on plant water use and carbon uptake. By identifying a suite of structural traits that influence important physiological functions, our findings can help to understand how conifers may respond to the pressures exerted by climate change.
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Respiratory temperature responses of tropical conifers differ with leaf morphology
Abstract Photosynthetic traits suggest that shade tolerance may explain the contrasting success of two conifer taxa, Podocarpaceae and Pinaceae, in tropical forests. Needle‐leaved species fromPinus(Pinaceae) are generally absent from tropical forests, whereasPinus krempfii, a flat‐leaved pine, and numerous flat‐leaved Podocarpaceae are abundant. Respiration (R) traits may provide additional insight into the drivers of the contrasting success of needle‐ and flat‐leaved conifers in tropical forests.We measured the short‐term respiratory temperature (RT) response between 10 and 50°C and foliar morphological traits of three needle‐ and seven flat‐leaved conifer species coexisting in a tropical montane forest in the Central Highlands of Vietnam containing notable conifer diversity. We fit a lognormal polynomial model to each RT curve and extracted the following three parameters:a(basalR), andbandc(together describing the shape of the response).Needle‐leaved species (Pinus kesiya,Pinus dalatensisandDacrydium elatum) had higher rates of area‐basedRat 25°C (R25‐area) as well as higher area‐based modelled basal respiration (a) than flat‐leaved species (P. krempfii,Podocarpus neriifolius,Dacrycarpus imbricatus,Nageia nana,Taxus wallichiana,Keteeleria evelynianaandFokienia hodginsii). No significant differences were found between needle‐ and flat‐leaved species in mass‐basedR25(R25‐mass) or in the shape of the RT response (bandc); however, interspecific differences inR25‐mass,Rat nighttime temperature extremes (R4.1andR20.6) and leaf traits were apparent.Differences inR25‐areaandasuggest that needle‐leaved foliage may be more energetically costly to maintain than flat‐leaved foliage, providing new insight and additional support for the hypothesis that shade tolerance is an important driver of Podocarpaceae success and Pinaceae absence in the majority of tropical forests.Interspecific differences inR25‐massand leaf traits highlight that varying ecological strategies are employed by conifers to coexist and survive in the Central Highlands of Vietnam. Ultimately, these data further our understanding of current conifer biogeographical distributions and underscore the need for additional studies to elucidate the effects of extreme temperature events on the continued survival of conifers in this unique forest. A freePlain Language Summarycan be found within the Supporting Information of this article.
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- Award ID(s):
- 2001949
- PAR ID:
- 10450228
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Functional Ecology
- Volume:
- 35
- Issue:
- 7
- ISSN:
- 0269-8463
- Page Range / eLocation ID:
- p. 1408-1423
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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