Covariance of sun and shade leaf traits along a tropical forest elevation gradient

Foliar trait adaptation to sun and shade has been extensively studied in the context of photosynthetic performance of plants, focusing on nitrogen allocation, light capture and use via chlorophyll pigments and leaf morphology; however, less is known about the potential sun-shade dichotomy of other functionally important foliar traits. In this study, we measured 19 traits in paired sun and shade leaves along a 3,500-m elevation gradient in southern Peru to test whether the traits differ with canopy position, and to assess if relative differences vary with species composition and/or environmental filters. We found significant sun-shade differences in leaf mass per area (LMA), photosynthetic pigments (Chl ab and Car), and δ13C. Sun-shade offsets among these traits remained constant with elevation, soil substrates, and species compositional changes. However, other foliar traits related to structure and chemical defense, and those defining general metabolic processes, did not differ with canopy position. Our results suggest that whole-canopy function is captured in many traits of sun leaves; however, photosynthesis-related traits must be scaled based on canopy light extinction. These findings show that top-of-canopy measurements of foliar chemistry from spectral remote sensing approaches map directly to whole-canopy foliar traits including shaded leaves that cannot be directly observed from above.Fil: Martin, Roberta E.. Arizona State University; Estados UnidosFil: Asner, Gregory P.. Arizona State University; Estados UnidosFil: Bentley, Lisa Patrick. Sonoma State University; Estados UnidosFil: Shenkin, Alexander. University of Oxford; Reino UnidoFil: Salinas, Norma. Oxford Social Sciences Division; Reino Unido. Pontificia Universidad Católica de Perú; PerúFil: Huaypar, Katherine Quispe. Universidad Nacional San Antonio Abad del Cusco; PerúFil: Pillco, Milenka Montoya. Universidad Nacional San Antonio Abad del Cusco; PerúFil: Ccori Álvarez, Flor Delis. Universidad Nacional San Antonio Abad del Cusco; PerúFil: Enquist, Brian J.. University of Arizona; Estados UnidosFil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Malhi, Yadvinder. University of Oxford; Reino Unid

Scale dependence of canopy trait distributions along a tropical forest elevation gradient

Average responses of forest foliar traits to elevation are well understood, but far less is known about trait distributional responses to elevation at multiple ecological scales. This limits our understanding of the ecological scales at which trait variation occurs in response to environmental drivers and change. We analyzed and compared multiple canopy foliar trait distributions using field sampling and airborne imaging spectroscopy along an Andes-to-Amazon elevation gradient. Field-estimated traits were generated from three community-weighting methods, and remotely sensed estimates of traits were made at three scales defined by sampling grain size and ecological extent. Field and remote sensing approaches revealed increases in average leaf mass per unit area (LMA), water, nonstructural carbohydrates (NSCs) and polyphenols with increasing elevation. Foliar nutrients and photosynthetic pigments displayed little to no elevation trend. Sample weighting approaches had little impact on field-estimated trait responses to elevation. Plot representativeness of trait distributions at landscape scales decreased with increasing elevation. Remote sensing indicated elevation-dependent increases in trait variance and distributional skew. Multiscale invariance of LMA, leaf water and NSC mark these traits as candidates for tracking forest responses to changing climate. Trait-based ecological studies can be greatly enhanced with multiscale studies made possible by imaging spectroscopy.Fil: Asner, Gregory P.. Carnegie Institution for Science. Department of Global Ecology; Estados UnidosFil: Martin, Roberta E.. Carnegie Institution for Science. Department of Global Ecology; Estados UnidosFil: Anderson, Christopher Brian. Carnegie Institution for Science. Department of Global Ecology; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kryston, Katherine. Carnegie Institution for Science. Department of Global Ecology; Estados UnidosFil: Vaughn, Nicholas. Carnegie Institution for Science. Department of Global Ecology; Estados UnidosFil: Knapp, David E.. Carnegie Institution for Science. Department of Global Ecology; Estados UnidosFil: Bentley, Lisa Patrick. University of Oxford; Reino UnidoFil: Shenkin, Alexander. University of Oxford; Reino UnidoFil: Salinas, Norma. University of Oxford; Reino Unido. Pontificia Universidad Católica de Perú; PerúFil: Sinca, Felipe. Carnegie Institution for Science. Department of Global Ecology; Estados UnidosFil: Tupayachi, Raul. Carnegie Institution for Science. Department of Global Ecology; Estados UnidosFil: Quispe Huaypar, Katherine. Universidad Nacional de San Antonio Abad del Cusco; PerúFil: Montoya Pillco, Milenka. Universidad Nacional de San Antonio Abad del Cusco; PerúFil: Ccori Álvarez, Flor Delis. Universidad Nacional de San Antonio Abad del Cusco; PerúFil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Enquist, Brian J.. Arizona State University; Estados UnidosFil: Malhi, Yadvinder. University of Oxford; Reino Unid

Leaf-level photosynthetic capacity in lowland Amazonian and high-1 elevation, Andean tropical moist forests of Peru

We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (Vcmax), and the maximum rate of electron transport (Jmax)), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (Ma, Na and Pa, respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO2-fixing enzyme Rubisco. Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil [P] and leaf Pa were key explanatory factors for models of area-based Vcmax and Jmax but did not account for variations in photosynthetic N-use efficiency. At any given Na and Pa, the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests