- Author: Ben Faber
So what happens to an avocado tree when it runs out of water? The stomata close and stops transpiring. When water no longer evaporates from the leaf surface, it heats up. If it gets hot enough, and it will, the leaf sunburns and dies. It stopped photosynthesizing long before that, because the process is temperature sensitive. Avocado is an “upper story, late successional” tree which is more affected by drought than faster growing, weedy species. So read about what happens to a forest as temperatures increase.
by: Olof Lönnehed
University of Gothenburg
olof.lonnehed@science.gu.se
Trees get overheated in a warmer rainforest
The ability of rainforests to store carbon can decrease in pace with climate change. This is due to photosynthesis rates in the leaves of rainforest species falling at higher temperatures and the trees' natural cooling systems failing during droughts. Increased heat threatens especially the species that store most carbon. This has been shown in a new thesis from the University of Gothenburg.
Some species of trees are able to handle rising heat in the tropics by sucking up large quantities of water to their leaves and transpiring through wide-opened pores in their leaves. These are mainly fast-growing trees that establish themselves early as a rainforest grows up. The same cannot be said for the trees that make up the canopy of rainforests in old growth forests. They grow slower, but get bigger and taller, and their leaves do not have the same ability to cool themselves via transpiration.
Water powers the ‘air conditioning' of the leaves
“The tropics have not experienced Ice Ages and have thus had a relatively stable climate historically as well as seasonally. With climate change, it has started to get warmer and then we have seen that some species of trees are showing increased mortality rates, but we have not really known why before,” says Maria Wittemann, who wrote the thesis.
She has studied several species of tree that can be roughly divided into early successional species, which establish themselves early in a new rainforest, and late successional species, which grow slower but grow considerably bigger, and are thus a larger carbon sink over the long term. A clear difference is how the trees in the two groups handle heat. The early successional species open the pores wider in their leaves, through which they transpire large amounts of water, thus keeping down the temperature in their leaves – similar to an air conditioning system. The late successional species do not open their pores as much, and therefore it's more difficult for them to stay cool.
More sensitive to drought
“We found large temperature differences in the leaves in our measurements. There could be a difference of 10 degrees Celsius between late successional species and early successional species growing in the same location. The late successional species had more difficulty coping with abnormally high temperatures. These trees had a higher mortality rate,” says Maria Wittemann.
However, the early successional species' profuse transpiration through their leaves also requires a lot of water. During a period of drought, the researchers noted that early successional species became more vulnerable to the heat and dropped their leaves. Their reduced consumption of water meant that late successional species were more resistant to drought.
“Our results show that photosynthesis rates in rainforest trees falls when the temperature rises in their leaves, which occurs mainly in late successional species. The proteins and membranes in their leaves, that are essential for photosynthesis, fail, and eventually the trees die due to carbon starvation because they cannot convert enough carbon dioxide from the air. This affects the entire ecosystem. We know, for example, that some animals eat the fruits of the late successional species,” says Maria Wittemann.
Co-operation with a local university
Previous research shows that the situation is worst in the Amazon. It is estimated that this carbon sink will be transformed into a carbon source by as early as 2035. In African rainforests, climate change has not gone as far.
Research at the University of Gothenburg is being conducted in high-elevation forests in Rwanda in collaboration with the University of Rwanda. The trees have been studied in situ, but seeds have also been planted in climate chambers in Gothenburg to study their development at different temperatures.
“We are working with various stakeholders in Rwanda. There is not much rainforest left in Rwanda and when they plant new trees, they want to know which indigenous species will be able to survive in a warmer climate,” says Maria Wittemann.
Facts about the study: The sensitivity of trees to climate change was studied by planting tree species adapted to a cooler climate in Rwanda's elevated tropical rainforests at three locations with different climates at different altitudes. One step down the elevation gradient corresponds to a possible future climate. The field experiment is called Rwanda TREE (TRopical Elevation Experiment) and consists of 20 species and 5,400 trees. To learn more about Rwanda TREE, visit the website www.rwandatree.com or watch the film https://www.youtube.com/watch?v=EkDvbwisqlQ.
- Author: Ben Faber
Terrestrial laser scanning data show that trees move their branches in a diurnal pattern, settling down for the night – as if falling asleep. So far, however, researchers have been uncertain as to why this happens.
A new study utilising time-series of terrestrial laser scanning measurements shows that changes in the water status of leaves and branches causes branches to move downward at night, up to 20 cm depending on the tree species. Leaves and branches replenish their water storage during the night, increasing their weight and causing them to droop down. Terrestrial laser scanning is a remote sensing technique that can produce a 3D representation of the surroundings with millimetre accuracy. With repeated measurements, it is possible to study small structural changes in the environment, such as the movement of branches.
“By monitoring the movement of tree branches, we can gain insight into how water moves inside the tree. Climate change reduces the availability of water and increases drought stress, so it is important to understand the movement of water in trees in order to understand changes in forest health,” Postdoctoral Researcher and the lead author of the article Samuli Junttila from the University of Eastern Finland says.
In the laboratory, the researchers found that tree branch position followed changes in tree water status also over a longer time period. These findings also have practical applications. For example, laser scanning could be used to monitor plant water status in a greenhouse to automate watering regimes and save valuable resources.
The study was conducted at the University of Eastern Finland in collaboration with the Finnish Geospatial Research Institute and the University of Helsinki. The study was conducted within the UNITE Flagship Programme funded by the Academy of Finland.
https://www.mdpi.com/1999-4907/13/5/728
- Author: Ben Faber
ADVANCES IN CITRUS WATER MANAGEMENT WORKSHOP
Date: May 4, 2022
With: UC Davis, UC Riverside, UC Cooperative Extension
Location: UC Riverside - Palm Desert Center, Palm Desert, CA
WORKSHOP AGENDA
9:30 – 10:00 am: Registration
Morning Session – (10:00 am – 12:00 pm)
Block A - Basic principles & information for irrigation management – Moderator: S. Rios
10:00 – 10:15 am: Welcome and Updates for the Citrus production industry (A. Lopez Lopez,
Government of Baja California)
10:15 – 10:45 am: Soil-plant-water relations for Citrus (B. Faber, UCCE Ventura County)
10:45 – 11:15 am: Water Budgeting: where to find the relevant information and
how it all works together (K. Bali, UC ANR)
11:15 – 11:45 am: Methods and tools for irrigation scheduling in Citrus (D. Zaccaria, UC Davis)
11:45 – 12:00 pm: Questions & Answers
12:00 – 12:30 pm LUNCH BREAK
Afternoon Session: 12:30 – 2:30 pm
Block B - Information developed through research efforts – Moderator: E. Scudiero
12:30 – 1:00 pm: Results from the CDFA-funded research project (2018-2020) on Citrus ET/Kc
(D. Zaccaria, UC Davis)
1:00 – 1:30 pm: Strategies for Citrus irrigation management with limited water supply (B. Faber,
UCCE Ventura County)
1:30 – 2:00 pm: FRET – Forecast ETo from the National Weather Service (R. Snyder, UC Davis)
2:00 – 2:30 pm Questions & Answers
2:30 pm WORKSHOP ADJOURN
List of speakers/presenters and email contacts:
- Angel Lopez Lopez – Government of Baja California: alopezl@baja.gob.mx
- Sonia Rios – UCCE Riverside County: sirios@ucanr.edu
- Ben Faber – UCCE Ventura County: bafaber@ucdavis.edu
- Khaled Bali – UC Kearney Agricultural REC: kmbali@ucanr.edu
- Daniele Zaccaria – UC Davis: dzaccaria@ucdavis.edu
- Elia Scudiero – UC Riverside: elia.scudiero@ucr.edu
Rick Snyder – UC Davis: rlsnyder@ucdavis.edu
/span>- Author: Ben Faber
Western Water Systems: Update Join us for a free webinar offering an update on Western Water Systems
Date: Wednesday – February 3, 2021 Time: 1:00P Eastern/12:00 Central/11:00 Mountain/10:00 Pacific
Kristiana Hansen - Economic Impacts from Water Reductions in Agriculture: Examples from the Colorado River Basin Associate Professor in Agricultural & Applied Economics | University of Wyoming
Tapan Pathak - Climate Change Trends and Impacts on Specialist in Climate Adaptation in Agriculture | University of California Division of Agriculture and Natural Resources
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JOIN us via:
Future webinar topics include: Climate Risk and Tools for Management, Credit Conditions in Agriculture, and much more!
Archives of over 100 past AIUT webinar presentations are available on the site for viewing or download.
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- Author: Ben Faber
Please register for Nitrogen Management Plan Self-Certification Webinar on Tuesday and Wednesday, November 17/18, 2020 9:00 AM - 12:00 PM PST at:
https://attendee.gototraining.com/r/2352520986463929090
This workshop is intended for growers, and their representatives, who are looking to learn more about nitrogen management planning and/or intend to self-certify their plans. It is also a good education on how nitrogen works in our environment and how it can be managed. The program is sponsored by CA Department of Food and Agriculture, University of CA Cooperative Extension and the Ventura County Irrigated Lands Group.
Attendees must participate in both sessions to receive education credit and qualify to take the online certification test after the final webinar session.
After registering you will receive a confirmation email containing information about joining the training.
This workshop will open a half hour early at 8:30am, to allow attendees to test their connection and access the GoTo Training webinar link.
Email organizer: training@lwa.com
Image of nitrogen deficient avocado leaf on left