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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 (tdomingu@gmail.com), 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

During the first quarter of 2017, Dr. Domingues and his team continued monitoring various photosynthesis-related parameters at their research plot and conducting preliminary analyses. In particular, they have looked at the response of assimilation rates of various tree species to temperature, carbon dioxide levels, and relative humidity. Another achievement during this period was the installation of 25 sap-flow sensors that measure the velocity of water being transported within tree trunks. The first field technician hired to work on this effort (Maquelle Garcia) has now become a PhD student at INPA and is developing her thesis work within the scope of the project. A replacement is now in place: Alacimar Guedes. He is an enthusiastic young researcher who has completed his Master’s course on forestry and has tree climbing skills, so he makes an excellent addition to the group. On the down side, the new photosynthesis analyzer system unfortunately presented some problems once it was deployed in the field earlier this year. Apparently the new model does not handle the high tropical moisture levels well, and during periods of high relative humidity some water condensed inside the console, preventing some of the air valves from operating normally. This was a surprise even to the manufacturer, but the unit was sent away for maintenance and should arrive back in Manaus later in June.

Dr. Domingues has met with co-PI Prof. Rafael Oliveira at the Universidade de Campinas to discuss how to analyze the dendrometer and sap flow data. They are developing some strategies that will also be discussed with their U.S. partner Dr. Pierre Gentine when the PI visits New York (tentatively in December 2017). Once the photosynthesis system is returned to Manaus, the team will resume making their monthly gas exchange measurements. Manual dendrometers are being manufactured in the lab at INPA and will be installed on trees during the group’s next field trip (June 19 -24). The automated dendrometers (TreeHuggers) that were ordered recently will be installed in August. Sap flow measurements are being stored in the data loggers of the sensors and are being retrieved monthly. A pressure bomb has been ordered and once it arrives, monthly determinations of the water status of leaves will be performed.


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