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Partnerships for enhanced engagement in research (PEER)
Cycle 4 (2015 Deadline)

Functional diversity of interrelated photosynthesis and water use of Central Amazonian trees

PI: Tomas Domingues (, University of São Paulo
U.S. Partner: Pierre Gentine, Columbia University
Project Dates: November 2015 - October 2018

Project Overview

4-445 Tree Canopy Measurements
Team member Maquelle Garcia takes measurements at the top of the tree canopy (photo courtesy of Dr. Domingues).

This project will generate novel understanding on the diversity of plant traits related to water use and photosynthesis. The functional diversity present in a given community is a key dimension of biodiversity that effectively modulates how forests respond to disturbances, such as logging, precipitation, and temperature extremes or the increase in carbon dioxide concentration. It also determines the extent of the feedback between forest and climate, therefore informing us on possible consequences of forest mortality or land use change. To better predict the resilience of the forest and its capacity to provide ecosystem services, it is essential to evaluate the current spectrum of functional diversity, still a major unknown component in biodiversity research. Dr. Domingues and his colleagues will use a new approach looking at the carbon and water cycles as fundamentally coupled at both the leaf and tree level. In order to achieve a qualitative and quantitative assessment of water and carbon strategies by Amazonian trees, they will continuously monitor both the transport of water in tree trunks and the continuous expansion and contraction of the tree’s bole diameter, which relates to water storage, mobilization of photosynthetic products, and growth. This will be complemented by leaf-level measurements of photosynthetic apparatus and hydraulics to comprehend the individual link of photosynthesis with water usage. This novel dataset will demonstrate the coupling between transport of water and carbon within trees and how it relates to forest productivity. The new data will be applied to broader scales by using land-surface and ecosystem models to simulate the interaction between forest and atmosphere at different scenarios of functional diversity. This step will be achieved by collaboration with U.S. Government-supported partner Pierre Gentine, who is implementing a soil-plant-atmosphere-continuum model able to reproduce the carbon and water relationship in the Community Land Model. Brazilian students will also receive much-needed training in computational modeling.

The proposed research will shed light on the role of biodiversity not only in maintaining and improving quality of life for inhabitants of the Amazon region but also for improving water security in other areas. By characterizing current variability in water and carbon use strategies expressed by Amazonian trees, it is possible to assess how much biodiversity loss within this group is tolerable, without seriously compromising ecosystem functioning. The information to be generated by this project will help in evaluating ecosystem integrity in areas where disturbance has already occurred. For example, it will be possible to assess disparities between pristine forest and secondary vegetation, in terms of ecosystem response to water stress whether from bottom up (soil to leaves induced by dry soil conditions) or top down (from leaves to soil induced by dry or hot weather conditions), according to species composition of the community. As a result, plant communities can be evaluated in terms of resilience to further climatic extremes. The products of this research will also aid in guiding species selection for vegetation restoration efforts. For example, such information will be of great value to local community initiatives focusing on production of tree saplings for reforestation programs or ecosystem improvement actions.

Summary of Recent Activities

The project activities were in full swing in the first quarter of 2018 with intense data collection in the field and discussion of the scientific results being carried out. PhD student Maquelle Garcia and research assistant Alacimar Guedes are spending a considerable amount of their time in the forest performing detailed gas exchange and plant hydraulic measurements. A new, detailed and exciting data set on the responses of plant water use and carbon uptake is taking shape and will be related to site micrometeorological variables (air temperature, humidity, energy budget, and precipitation). The PI, Dr. Domingues, visited the group and the field site in February and April. The objective of the first visit was to evaluate field equipment and also to participate in Maquelle's qualifying exam, which she accomplished with great success. The second visit was during a meeting of project partners (AFEX project - Amazon Fertilization Experiment, led by Prof. Carlos Alberto Quesada of INPA and Iain Hartley of Exeter University). During both visits, intense discussion of the data collection and analysis took place. All partners involved are very satisfied with the development of the project and are very enthusiastic about it. Students are engaged and building a solid career with the support from this PEER project.

Maquelle Garcia is starting a collaboration with Prof. Bart Kruijt from Wageningen University in the Netherlands. He was quite impressed with Maquelle´s data set and the team is now working on data comparison with data collected by Prof. Kruijt's group at Caxiuanã Forest (another research site in the Amazon). They are making plans for Maquelle to visit Prof. Kruijt in the Netherlands later this year.

During May the team plans to install a system designed to quantify the emission of light from the leaves. Such light emission is called fluorescence, the small fraction of the sunlight that is absorbed by the leaves and does not contribute to photosynthesis but instead is emitted back into the atmosphere. This emission rate is dependent on how water stressed the plants are. The plan is for the majority of the equipment to be purchased by colleagues from Oak Ridge National Lab, and the PEER project will support the purchase of solar panels, stationary batteries, and installation fittings.

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