A theory of plant function helps to explain leaf-trait and productivity responses to elevation

• Published in: The New phytologist Vol. 226; no. 5; pp. 1274 - 1284
• Main Authors: Peng, Yunke, Bloomfield, Keith J., Prentice, Iain Colin
• Format: Journal Article
• Language: English
• Published: England Wiley 01.06.2020; Wiley Subscription Services, Inc
• Subjects: Acclimation; Acclimatization; Adaptation; Carbon cycle; Carbon Dioxide; Carboxylation; Ecosystem; elevation transect; First principles; Leaves; Nitrogen; optimality; Optimization; Phosphorus; Photosynthesis; plant functional traits; Plant Leaves; Primary production; Soil; Temperature; Variance analysis; primary production; optimality; photosynthesis; acclimation; temperature; adaptation; elevation transect; plant functional traits
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.16447

• Several publications have examined leaf-trait and carbon-cycling shifts along an Amazon–Andes transect spanning 3.5 km in elevation and 16°C in mean annual temperature. Photosynthetic capacity was previously shown to increase as temperature declines with increasing elevation, counteracting enzyme-kinetic effects. Primary production declines, nonetheless, due to decreasing light availability. We aimed to predict leaf-trait and production gradients from first principles, using published data to test an emerging theory whereby photosynthetic traits and primary production depend on optimal acclimation and/or adaptation to environment. • We re-analysed published data for 210 species at 25 sites, fitting linear relationships to elevation for both predicted and observed photosynthetic traits and primary production. • Declining leaf-internal/ambient CO₂ ratio (χ) and increasing carboxylation (V cmax) and electron-transport (J cmax) capacities with increasing elevation were predicted. Increases in leaf nitrogen content with elevation were explained by increasing V cmax and leaf mass-per-area. Leaf and soil phosphorus covaried, but after controlling for elevation, no nutrient metric accounted for any additional variance in photosynthetic traits. Primary production was predicted to decline with elevation. • This analysis unifies leaf and ecosystem observations in a common theoretical framework. The insensitivity of primary production to temperature is shown to emerge as a consequence of the optimisation of photosynthetic traits.