Comparison Of Carbon Sequestrated Capacity Of Mangrove Species With Different Leaf Structure:from Leaf To Stand Level Study

Mangroves are type of the special dicotyledon plants which grows in tropical and subtropical intertidal zone.In adapting to harsh interdial environments,such as high temperature and high salt,different morphological structures selected by the nature leads to the optimal function traits,such as optimal carbon accumulation rates of leaves.There are naturally two different palisade and spongy mesophyll tissue types of leaves,including the bifacial and isobilateral on dicotyledon plants,which can be also found in mangroves.In current study,we aimed to test the contribution of the different anatomic leaf structures to plant carbon accumulation rates.We hypothesized that,1)two different survival strategies were preferred in leaf economic spectrum due to the difference of function and structure between isohedral leaves and bifacial leaf,.;2)the isobilateral leaf with similar palisade tissue structure on both sides lead to two folds of carbon gain of the bifacial leaf,due to photosynthesis on both sides of isobilateral leaf.We measured leaf anatomic structure based on palisade proportion of leaf transection of totally 29 mangrove species.The leaf economic spectrum of mangrove species with two different structures was analyzed from anatomical structure,morphological,photosynthetic and fluorescence characteristics.Three different mangrove species as representatives of different leaf anatomical structures,Sonneratia apetala(isobilateral leaf),Kandelia obovale(incomplete leaf)and Avicennia marina(bifacial leaf),were selected to study carbon sequestration rates and leaf angles at the bunch level from the leaf perspective.A one-year study on stand level carbon accumulation was carried outwith monitoring the stem sap flow,daily photosynthesis,and the net primary productivity(NPP)with different leaf anatomical structure was estimated.The main results are as follows.1.Among the total 29 species studied,12 of them belongs to isobilateral leaf,occupying nearly half of totally mangrove species in China,which was higher than the percentages of the terrestrial plants.On branch level,leaf angle of isobilateral leaf plants were about 1.7 times higher than bifacial leaf plants among the 29 mangrove species tested.In this paper,we classified mangrove species from the perspective of leaf structure,and studied the characteristics of leaf economic spectrum.From the perspective of leaf economic spectrum,the isobilateral leaf of mangrove species were more inclined to the rapid investment-income type,while bifacial leaf species were more inclined to the slow investment-income type.2.In the greenhouse,both sides of Sonneratia leaf had higher diurnal assimilation rate(A)and photosynthetic capacity than both sides of Avicernia,which resulted in higher growth rates for the stands.The optimum leaf angle of Sonneratia plants for photosynthetic in greenhouse was within 45?90°,for Avicennia was within 0-45°,comparing to the natural leaf angle of Sonneratia(58.01±4.46°)abd of Avicennia(7.28±5.84°)to the earth surface in the field condition.The vertical leaf angle of Sonneratia suggested the ability of minimizing the photo inhibition and increasing light transmittance under strong light especially at noon,which contributing to high A during the whole day period.3.By monitoring the annual water use and combining the photosynthesis on stand level,we found that NPP of individual Sonneratia stand was 770.22±43.6 gCO2 m-2 a-1,which was about 1.18 folds as much as Avicennia,654.15±42.6 gCO2 m-2 a-1.The NPP of Kandelia was only 40.53%of that of p Sonneratia,which was only 312.17±17.13 gCO2 m-2 a-1.Avicennia was inclined to a more conservative water use strategy,while the Sonneratia was inclined to a survival strategy of high consumption and high productivity.Based on the current results from leaf level and stand level,the carbon accumulation of Sonneratia with isobilateral leaf was proved to be approximately 1.2 folds to the bifacial leaf Avicennia.4.We accidentally found that there is a special transional type of isobilateral leaf in mangroves.The incomplete isobilateral leaf represented by Kandelia showed no low carbon sequestration ability from the leaf level to the stand level,indicating different adaptating stratage of mangroves.In this study,the carbon sequestration rate and leaf economic spectrum of different leaf structure mangrove species were discussed from the aspects of leaf structure,plant photosynthesis and plant level carbon sequestration capacity.The adaptive strategies of mangrove plants were also discussed according to the leaf economic spectrum.The mechanisms of high productivity of mangrove forest were revealed from the level of physiology and ecology.The canopy level NPP and the carbon sequestration efficiency at the extrapolation community level need further combination in futurestudies.The evidence of enzyme activity,chloroplast structure and the evolution of different leaf structures might also contribute to carbon assimilation of leaf structures.