Climate Change: Does “No Seedlings” Really Mean “No Future Forests”?

Matthew posted a link to this Grist article before, and I think it’s worthy of its own discussion.


The driving force here is that the rising global temperature is wiping out seedlings. In many spots around the U.S. West, summer temperatures are already high enough to cook young trees before they can develop thick protective bark. Others have become so dry that seedlings shrivel before their roots can grow deep enough to reach groundwater. Both circumstances can thwart forest regeneration. Mature trees can survive in these areas long after they stop reproducing. But when fires wipe out these forests and seedings can’t get a foothold, they are replaced with grasses and dense brush.

Some of us remember reforestation problems on dry sites before climate change (I think people would say it was occurring then, we just didn’t know about it.)  Here is what we thought then… first you need seed.  And ponderosa pines have intermittent seed crops.  So grasses/forbs/shrubs may have reclaimed the site (sucked up the sun and soil moisture) by the time Mom and Dad ponderosa got together, not leaving any openings for baby trees to take hold.  Then there are seed predators of various kinds.  Then there’s soil moisture at the right time.  And critters that munch on seedlings.  You can go out to various sites today and see a range of  ponderosa (and in my hood, Doug fir, regeneration) from none to lots.

Back in those days, it was OK, and even desirable, to assist seedlings in “getting a foothold.”  As I’ve said numerous times, in the 80’s, we learned about seed collection, nursery practices, seedling treatment in transit, vermiculite slurries, vexar tubing, and so on.  We used to travel around and examine cone crops and numbers of filled seed to select good sites to produce seed. The whole thing as down to.. dare I say… a science.

What was interesting to me is how different conceptions and research methods can yield the same, or different conclusions.
Here are some concepts (not observations):

(1) if forests won’t grow back without help, then we must just get used to fewer forests.

(2) the absence of natural regeneration (over some time period)  means that trees won’t otherwise grow well if planted.

What physiologists and silviculturists (applied forest ecologists) used to tell us through logic and observation (seeds must come from somewhere), we now can validate via regression models.


While annual climate was an important driver of postfire regeneration, our findings also highlight that the nature of a fire event strongly influences postfire regeneration. For example, the combined relative influence of annual climate variables on tree recruitment in our boosted regression tree (BRT) models was 24% for ponderosa pine and 34% for Douglas-fir (SI Appendix, Fig. S3), while the relative influence of distance to seed source, which is largely determined by fire severity, was 32% for ponderosa pine and 21% for Douglas-fir (SI Appendix, Fig. S3). The importance of seed tree availability in determining postfire regeneration has been demonstrated across forest types in the western United States (e.g., refs. 1720, and 46),

TSW readers tend to be out and about in the woods. Take a look next time (in a place where there are parent trees producing seed) and check out whether there is natural regeneration. I did that in my neighborhood and came up with the above photo. I also live in the fringe of ponderosa pine habitat on the Front Range of Colorado.  In this photo you can see parent trees, cones on the ground, and many seedlings. It’s something we can pay attention to, and maybe learn something by sharing what we see in different parts of the west.

3 thoughts on “Climate Change: Does “No Seedlings” Really Mean “No Future Forests”?”

  1. There are some interesting and promising (nursery) studies that are employing a technique called ‘bio-priming,’ which uses pre-exposure to a priming agent, such as heat, water-deprivation, etc., which might help plants to develop (latent) abilities that would improve their tolerance-potential, possibly enabling them to withstand subsequently harsher stresses.

  2. Concept #3….are traditional scientific conclusions and widely accepted management practices still relevant under climate change?

    Personally, we abandoned the well established notion of treating juniper like a weed (i.e., either liquidate it or ignore it) decades ago after touring a neighbor’s five-decade program of converting south-slope, pure juniper stands to Ponderosa Pine (using seed from seasonal cone collectors on the Malheur NF). Not so much because it was “new” knowledge but because it confirmed personal observations from our own ranch of the shading effect of junipers on native grasses and conifer seedlings. Now, we treat juniper like a tree and apply a mix of harvest, thinning and extensive pruning in order to provide site conditions conducive to establishing perennial plants, hardwood shrubs and conifer.

    Now, over a decade later, we are observing what appears to be same relationship emerging on our high elevation summer pasture between conifers and certain perennial grasses.

  3. Your approach is right on the money. I’ve been around for a few years and it may be new in your local BUT it is certainly based on accepted scientific plant physiology principles. For lack of a better name we might call it accelerated or managed Forest Succession.?

    Congratulations, You have done a great job of applying the fundamental principles of science to solve a problem.


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