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  1. ; ; ; ; ; ; ( , Functional Ecology)
    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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  2. ; ; ; ; ; ; ; ; ; ; et al ( , Ecological Informatics)
    null (Ed.)
    Full Text Available 
  3. ; ; ; ; ; ; ; ( , Global Change Biology)
    Abstract

    Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosynthesis are linked at different spatial scales across the growing season. We examined seasonal relationships between ChlF and photosynthesis at the leaf, canopy, and ecosystem scales and explored how leaf‐level ChlF was linked with canopy‐scale solar‐induced chlorophyll fluorescence (SIF) in a temperate deciduous forest at Harvard Forest, Massachusetts,USA. Our results show that ChlF captured the seasonal variations of photosynthesis with significant linear relationships between ChlF and photosynthesis across the growing season over different spatial scales (R2 = 0.73, 0.77, and 0.86 at leaf, canopy, and satellite scales, respectively;P < 0.0001). We developed a model to estimateGPPfrom the tower‐based measurement ofSIFand leaf‐level ChlF parameters. The estimation ofGPPfrom this model agreed well with flux tower observations ofGPP(R2 = 0.68;P < 0.0001), demonstrating the potential ofSIFfor modelingGPP. At the leaf scale, we found that leafFq’/Fm’, the fraction of absorbed photons that are used for photochemistry for a light‐adapted measurement from a pulse amplitude modulation fluorometer, was the best leaf fluorescence parameter to correlate with canopySIFyield (SIF/APAR,R2 = 0.79;P < 0.0001). We also found that canopySIFandSIF‐derivedGPP(GPPSIF) were strongly correlated to leaf‐level biochemistry and canopy structure, including chlorophyll content (R2 = 0.65 for canopyGPPSIFand chlorophyll content;P < 0.0001), leaf area index (LAI) (R2 = 0.35 for canopyGPPSIFandLAI;P < 0.0001), and normalized difference vegetation index (NDVI) (R2 = 0.36 for canopyGPPSIFandNDVI;P < 0.0001). Our results suggest that ChlF can be a powerful tool to track photosynthetic rates at leaf, canopy, and ecosystem scales.

     
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  4. ; ; ; ; ; ; ; ; ; ( , Ecology and Evolution)
  5. ; ; ; ; ; ; ; ; ; ; et al ( , Global Change Biology)