25 research outputs found

    Intraspecific N and P stoichiometry of Phragmites australis: geographic patterns and variation among climatic regions

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    Geographic patterns in leaf stoichiometry reflect plant adaptations to environments. Leaf stoichiometry variations along environmental gradients have been extensively studied among terrestrial plants, but little has been known about intraspecific leaf stoichiometry, especially for wetland plants. Here we analyzed the dataset of leaf N and P of a cosmopolitan wetland species, Phragmites australis, and environmental (geographic, climate and soil) variables from literature and field investigation in natural wetlands distributed in three climatic regions (subtropical, temperate and highland) across China. We found no clear geographic patterns in leaf nutrients of P. australis across China, except for leaf N:P ratio increasing with altitude. Leaf N and N:P decreased with mean annual temperature (MAT), and leaf N and P were closely related to soil pH, C:N ratio and available P. Redundancy analysis showed that climate and soil variables explained 62.1% of total variation in leaf N, P and N:P. Furthermore, leaf N in temperate region and leaf P in subtropical region increased with soil available P, while leaf N:P in subtropical region decreased with soil pH. These patterns in P. australis different from terrestrial plants might imply that changes in climate and soil properties can exert divergent effects on wetland and terrestrial ecosystems

    Photosynthetic traits of tree species in response to leaf nutrient content in the central Amazon

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    Rainforest tree species are often found on poor soils where essential nutrients may be in low concentrations. Here, we determine the effect of nutrients (N, P, Ca, Mg and K) in photosynthetic traits in five rainforest tree species from central Amazonia. Gas exchange parameters were measured with an infrared gas analyzer in four saplings (1–3 m tall) per species using two leaves per plant. Data on gas exchange and leaf nutrient content (N, P, K, Ca and Mg) were collected between August and November, 2010. Specific leaf area (SLA) and leaf thickness (LT) were also determined. Potential photosynthesis per unit mass (Apot-mass), maximum carboxylation velocity of Rubisco (Vc-max) and electron transport rate (Jmax) were responsive to variation in leaf nutrient content per unit mass. On a mass basis, P content was positively correlated with N, Mg, and K content; Mg content was positively correlated with K content. However, no correlation was found between the content of P, Mg, K and Ca, or between Ca, Mg, K and N. SLA and LT were strongly related to Apot-area, Vc-max and Jmax (per unit area). Our study shows in situ evidence on the effect of leaf nutrients on Apot-mass, Vc-max and Jmax (per unit mass) of tree saplings in the central Amazon. The magnitude of changes in photosynthetic capacity of juvenile trees in the forest understory depends not only on N and P use efficiency, but also on the availability of K, Mg and Ca, in decreasing order. © 2015, Brazilian Society of Plant Physiology
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