Posts Tagged: rain

Learning from the Rain

Rain is wonderful stuff. If it comes and washes the accumulated salts of the last several years out of the root zones of citrus and avocado, that's a good thing. But what happens if there is a little too much rain? In the winter of 2005, Ventura got over 40” of rain, which is 100% more of what is normal. The last time big rains occurred prior to that was in the winter of 1997-98. That year the rains were evenly spaced on almost a weekly basis through the winter and into the late spring and over 50" fell. That year we had major problems with both citrus and avocados collapsing from asphyxiation. The same occurred in 2005, but not so pronounced.

Most rainfall years are not average, usually it is more or less than average. And sometimes the rains come, and flooding happens throughout California. The winter of 1861/62 saw such flooding that the harbor at Goleta was filled in.

In 2023, we had a lot more rain than we normally see and in Carpinteria it rained 4 inches in July!!!!!! And with the rain we saw mudslides and buried orchards, and with wet soil and winds we saw avocado trees being blown over.

And then came the winter of 2023/24, and there was more rain and more devastation (mudslides, buried orchards, etc.). But in general, trees look good. The consequences of low rainfall and the resulting greater application of salty irrigation water is leaf burn and often Botryosphaerias. After two wet rainy winters, we see much less of this kind of damage.

But there's been more subtle damage going on, especially avocados. It's been particularly hard on young trees with poorly developed root systems and orchards on flat ground. Asphyxiation has happened with the soils being too wet. Excluding air reduces root function, especially in the uptake of iron. It also allows ethylene to accumulate. Ethylene is a plant growth regulator that accelerates maturity. When roots sense ethylene, it causes leaf and fruit drop. The combined lack of oxygen and accumulation of ethylene leads to iron chlorosis and leaf drop. These are characteristic symptoms of asphyxiation and wet soils.

What other problems have we seen with rain, and what can be done to prepare for the unexpected?  Learning from the Rain

https://ceventura.ucanr.edu/newsletters/Topics_in_Subtropics102527.pdf

 

rain

Lawn-pocalypse! Surviving Drought

Ah, summer! The season of sunburns, pool parties, and… lawn droughts. If your once lush, green carpet now looks like a crunchy brown doormat, you're not alone. Let's dive into why your yard is staging a dramatic death scene and what you can do to...

Bermuda grass and weeds overtaking drought stressed turf grass.

A patch of former lawn, mostly dead, with a few green weeds and Bermudagrass

Too Much Rain? A Blog Refrain

A repeat post from the recent past

water puddling

Mulch and TOO Much Rain

What Can Happen With Too Much Rain? Watch that Mulch!!!

Rain is wonderful stuff. If it comes and washes the accumulated salts of the last several years out of the root zones of citrus and avocado, that's a good thing. But what happens if there is a little too much of the good stuff? In the winter of 2005, Venture got over 40” of rain, which is 200% of what is normal. The last time big rains occurred prior to that was in the winter of 1997-98. That year the rains were evenly spaced on almost a weekly basis through the winter and into the late spring and over 50" fell. That year we had major problems with both citrus and avocados collapsing from asphyxiation. The same occurred in 2005, but not so pronounced.

Rain is good, right?

In 2003 we had a lot more rain than we normally see and in Carpinteria it rained 4 inches in July!!!!!! In some young trees with poorly developed root systems, we have seen some collapse from asphyxiation.  Avocados tend to be more susceptible than citrus, and some rootstocks more than others. Even big trees collapsed.

Asphyxiation is a physiological problem that may affect certain branches, whole limbs or the entire tree. Leaves wilt and may fall, the fruit withers and drops and the branches die back to a greater or lesser extent. The condition develops so rapidly that it may be regarded as a form of collapse. Usually, the larger stems and branches remain alive, and after a time, vigorous new growth is put out so that the tree tends to recover. Young trees can be harder hit, but sunburn damage from lack of leaves may be more of a problem.

Asphyxiation is related to the air and water conditions of the soil. The trouble appears mainly in fine-textured or shallow soils with impervious sub-soils. In 1997-98, this even occurred on slopes with normally good drainage because the rains were so frequent. When such soils are over-irrigated or wetted by rains, the water displaces the soil oxygen. The smaller roots die when deprived of oxygen. When the stress of water shortage develops, the impaired roots are unable to supply water to the leaves rapidly enough and the tree collapses. The condition is accentuated when rainy weather is followed by winds or warm conditions.

It doesn't take standing water to have asphyxiation occur.

Mulch is good, right?

It can get spread awfully thick

Mulch does lots of good things, like reducing erosion, controlling weeds, improving infiltration, increasing organic matter to control root disease, reducing soil temperatures, reducing evaporation loss and therefore improving soil moisture content. Ah, but that is a problem when there is a lot of rain. It can lead to asphyxiation, just because of that last point. In rainy conditions, there needs to be a period of air entry into the soil and mulch because it reduces evaporative loss can keep the soil TOO wet, leading to asphyxiation.

Asphyxiated tree that has been overmulched and is now recovering after whitewashing.

So what do you do? With a thick layer of mulch when there is too much rain? You pull it away several feet from the base of the tree, so that sun can dry out the soil. It's a lot of work, especially after you have put a lot of work into spreading it.

The roots need to dry out and it can only happen if exposed to light and wind and ambient temperature

On flat ground, your avocados are planted on mounds or berms. And the soil texture is somewhat sandy and well drained. In that case, unless we get rain like 1997-98 when Ojai got nearly 50 inches and it rained just about every week from November through April and it seemed everything was under water, most trees should be all right. But, this last rainfall year I saw cases where unbermed, heavy soil avocado plantings had severe asphyxiation problems. So be forewarned.

 

Climate-Change Resources

University of California UC ANR Green Blog (Climate Change and Other Topics) https://ucanr.edu/blogs/Green/index.cfm?tagname=climate%20change (full index)

Examples:

     -  Save Trees First: Tips to Keep Them Alive Under Drought https://ucanr.edu/b/~CdD 

     - Landscaping with Fire Exposure in Mind: https://ucanr.edu/b/~G4D

     - Cities in California Inland Areas Must Make Street Tree Changes to adapt to Future Climate  https://ucanr.edu/b/~oF7

Drought, Climate Change and California Water Management Ted Grantham, UC Cooperative Extension specialist (23 minutes) https://youtu.be/dlimj75Wn9Q

Climate Variability and Change: Trends and Impacts on CA Agriculture Tapan Pathak, UC Cooperative Extension specialist (24 minutes) https://youtu.be/bIHI0yqqQJc

California Institute for Water Resources (links to blogs, talks, podcasts, water experts, etc.) https://ciwr.ucanr.edu/California_Drought_Expertise/

UC ANR Wildfire Resources (publications, videos, etc.) https://ucanr.edu/News/For_the_media/Press_kits/Wildfire/ (main website)

      -UC ANR Fire Resources and Information https://ucanr.edu/sites/fire/ (main website)

            -Preparing Home Landscaping https://ucanr.edu/sites/fire/Prepare/Landscaping/

UC ANR Free Publications https://anrcatalog.ucanr.edu/ (main website)

- Benefits of Plants to Humans and Urban Ecosystems: https://anrcatalog.ucanr.edu/pdf/8726.pdf

 -Keeping Plants Alive Under Drought and Water Restrictions (English version) https://anrcatalog.ucanr.edu/pdf/8553.pdf

  (Spanish version) https://anrcatalog.ucanr.edu/pdf/8628.pdf

-  Use of Graywater in Urban Landscapes https://anrcatalog.ucanr.edu/pdf/8536.pdf

-  Sustainable Landscaping in California https://anrcatalog.ucanr.edu/pdf/8504.pdf

 

Other (Non-UC) Climate Change Resources

Urban Forests and Climate Change. Urban forests play an important role in climate change mitigation and adaptation. Active stewardship of a community's forestry assets can strengthen local resilience to climate change while creating more sustainable and desirable places to live. https://www.fs.usda.gov/ccrc/topics/urban-forests

Examining the Viability of Planting Trees to Mitigate Climate Change (plausible at the forest level) https://climate.nasa.gov/news/2927/examining-the-viability-of-planting-trees-to-help-mitigate-climate-change/

Reports and other information resources coordinated under the auspices of the United Nations and produced through the collaboration of thousands of international scientists to provide a clear and up to date view of the current state of scientific knowledge relevant to climate change. United Nations Climate Action

Scientific reports, programs, action movements and events related to climate change. National Center for Atmospheric Research (National Science Foundation)

Find useful reports, program information and other documents resulting from federally funded research and development into the behavior of the atmosphere and related physical, biological and social systems. Search and find climate data from prehistory through to an hour ago in the world's largest climate data archive. (Formerly the "Climatic Data Center") National Centers for Environmental Information (NOAA)

Think tank providing information, analysis, policy and solution development for addressing climate change and energy issues (formerly known as the: "Pew Center on Global Climate Change"). Center for Climate & Energy Solutions (C2ES)

Mapping Resilience: A Blueprint for Thriving in the Face of Climate Disaster. The Climate Adaptation Knowledge Exchange (CAKE) was launched in July 2010 and is managed by EcoAdapt, a non-profit with a singular mission: to create a robust future in the face of climate change by bringing together diverse players to reshape planning and management in response to rapid climate change. https://www.cakex.org/documents/mapping-resilience-blueprint-thriving-face-climate-disaster

Cal-Adapt provides a way to explore peer-reviewed data that portrays how climate change might affect California at the state and local level. We make this data available through downloads, visualizations, and the Cal-Adapt API for your research, outreach, and adaptation planning needs. Cal-Adapt is a collaboration between state agency funding programs, university and private sector researchers https://cal-adapt.org/

Find reports, maps, data and other resources produced through a confederation of the research arms of 13 Federal departments and agencies that carry out research and develop and maintain capabilities that support the Nation's response to global change. Global Change (U.S. Global Change Research Program)

The Pacific Institute is a global water think tank that combines science-based thought leadership with active outreach to influence local, national, and international efforts to develop sustainable water policies. https://pacinst.org/our-approach/

Making equity real in climate adaptation and community resilience policies and programs: a guidebook. https://greenlining.org/publications/2019/making-equity-real-in-climate-adaption-and-community-resilience-policies-and-programs-a-guidebook/ 

Quarterly CA Climate Updates and CA Drought Monitor Maps (updated each Thursday) https://www.drought.gov/documents/quarterly-climate-impacts-and-outlook-western-region-june-2022

 

 

 

 

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