Giant Sequoias need their space
Standing among dozens of majestic Giant Sequoias Saturday, researcher Rob York said the overall health of Giant Sequoias is “poor” because of overgrowth and too much competition from other trees.
York was one of many presenters during the NorCal Society of American Foresters field meeting Saturday in Mountain Home State Demonstration Forest above Springville. Approximately 70 people attended the two-day conference.
A University of California at Berkeley professor, Dr. York said he was asked to evaluate the health of Giant Sequoias in the Sequoia National Monument and Kings Canyon National Park.
“Most of the groves are in poor condition,” he said as he stood among the giant trees of which some are thousands of years old. Many of the old giants show scares from lightning strikes and fires many, many years ago.
However, it is the lack of fires the past 100 years that is degrading the health of the groves, said York.
While he said more fire is needed, he admitted there are challenges to that today in that there is too much undergrowth in many of the groves. He said other disturbances of the groves - logging – can be effectively used to improve the health of the groves that then can allow the use of more intense fires.
Researches Doug Piirto and Josh Soderlund, both of Cal Poly, San Luis Obispo, gave results of a 20-year study in Mt. Home State Forest looking at the impacts thinning or thinning and burning may have on groves.
Soderlund said there was more tree mortality in the controlled plots where no treatments were done and that shows that without thinning or burning, the health of the trees will deteroriate.
They also said that thinning allowed for more diversity of other species and the thinned and burned plots had more seedlings of other species of trees, but not Giant Sequoias. Many said the thinned and burned plots did not open up the grove as much as needed.
One of the conclusions they had was that Sequoia groves need to be treated at least every 10 years.
York’s study looked more at the Sequoias and their chance for regeneration. He said an ideal situation would be one large tree for every half acre and in a healthy grove, there would be several smaller Sequoias growing.
“What does it take for regeneration of Giant Sequoias? It’s gap size,” he answered. “The bigger the gap, the bigger the seedlings,” he added.
He said the gap also allows for healthier trees in that the Giant Sequoia is not competing as much for water and nitrogen.
York said young Sequoias grow very fast, but competition greatly influences that growth. “If you want to maintain growth, you need thinning by year 10.”
On the National Monument, York said the groves need “disturbance. There is no question about that.”
He said “disturbance” can be fire or controlled logging.
“You need lots of and lots of disturbance to create young trees.”
Sequoia National Forest Supervisor Kevin Elliott said how to manage those groves will be a major focus of the Sequoia National Monument Management Plan expected to be released in a few weeks.
He said “restoration” of the groves is a key part of the plan, but that restoration will mean different things to different people.
York also addressed climate change and what impact that may have on Sequoia groves. He said the groves generally can be found at the line where it rains about half the time and it snows the other half.
“That’s the sweet spot,” he said for the groves.
“So, there is concern if the snowline moves higher,” he added, explaining that later snowmelt is needed for Giant Sequoia regeneration.