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Must we continue to bring in exotics?

A couple weeks back I posted about a collaborative research project that I am involved with to identify seed sources of two Mediterranean fir species (Turkish fir and Trojan fir) for use as Christmas trees in various locations around the country. The post prompted a question from Monta Zengerle who asked, “Must we continue to bring in exotics to satisfy the nursery trade?” Since our intended purpose is Christmas trees and people move plants around the world for purposes other than nursery stock, I’ve broadened the question to “Must we continue to bring in exotics?” for this discussion.

Not all exotic species introductions are man caused. This dock washed ashore in Oregon following the Japanese tsunami carrying all kinds of critters with it.

The answer, of course, is “No.” As human beings the only things we absolutely have to do are eat, sleep, and breathe. But the reality is much of the food and fiber production around the world, as well as our amenity plantings, are based on exotics plants. Human agricultural history is largely the story of plant importation and subsequent breeding. As Thomas Jefferson famously observed, “The greatest service which can be rendered any country is to add a useful plant to its culture.” However, it is doubtful that Jefferson considered kudzu or purple loosetrife could be among those plants added to our culture. Today we have a different understanding and realize that along with the economic benefits of plant exploration and importation comes the possibility of unintended and serious ecological consequences. And we’ve realized this for some time. People that deal with plant introductions on a regular basis talk about ecological errors and economic errors. If we allow importation of a plant that later turns out to be ‘bad actor’, we’ve made an ecologically harmful decision; if we ban a useful plant that ultimately would have turned out to be non-invasive, we’ve suffered an economic loss. Fortunately, only a small percentage of exotic species become naturalized and only small percentage of naturalized species become invasive. The underlying challenge is we cannot predict with 100% certainty which plants will be invasive in a new environment and which won’t. Ecologists are working on it and we can certainly begin to judge the invasive potential of new introductions. In the meantime, we are left with the imperfect calculation of whether the potential economic upside outweighs any potential environmental risk.

‘Top-work’ on noble fir in Oregon to maintain a single terminal leader. Turkish fir typically require less top-work.

So let’s look at our current project as a case study. What’s the upside? Christmas tree growers in the U.S. produce roughly 20 million trees annually. That’s a potential economic impact of hundreds of millions of dollars and seasonal and full-time employment for workers on over 13,000 farms from North Carolina to Washington State. A major issue for growers in virtually all of the principle growing regions is phytophthora root rot. Previous work at Oregon State University indicates that Turkish fir is highly resistant to this pathogen. By identifying seed sources with phytophthora resistance and superior Christmas tree characteristics (tree form, needle color, post-harvest needle retention), we will enable growers to continue or expand production and give consumers an additional choice for their holiday tree.

Native noble fir (left) is highly susceptible to root rot. Turkish fir (right) is much more resistant.

What’s the down side? As I mentioned, predicting invasiveness is difficult. That said, firs have several characteristics that make them unlikely invaders. Most firs have a relatively long juvenility period (age before they produce seed) which means they have a long period between generations. Secondly, most fir species produce seed crops sporadically as opposed to producing heavy seed crops year after year. Ecologically, firs are pretty wim
py; growing best on moisture, well-drained sites and unlikely to aggressively colonize disturbed areas. Lastly, the best predictor of invasiveness is invasiveness – a plant that has become invasive in one location is a candidate to become a repeat offender in a similar environment. Among conifers, the greatest issues with invasives have been pines (genus Pinus), in the southern hemisphere. In fact, all of the documented cases of invasives in the pine family (Pinaceae) are Pinus species; none were Abies. Based on all this, the likelihood of Turkish fir or Trojan fir becoming ecological problems appears very small, while the potential to add a useful plant to our culture is clear.

Exotic giant sequoias at Hoyt arboretum, Portland, OR.

Richardson, D.M. and Rejmánek. 2004. Conifers as invasive aliens: a global survey and predictive framework. Diversity and Distributions 10:321-331.

Rime and Reason

This weekend I got to take a leisurely drive to the northern end of Michigan’s Upper Peninsula with my daughter so she could check out Michigan Tech University. Lots to see along the 488 mile drive from DeWitt to Houghton, including a moose, lots of snowmobiles, and the world famous ‘Yooper tourist trap’. (For the uninitiated, people that live in the U.P. are known as Yooper’s, while those of us that live beneath the Mackinac Bridge are known as ‘Trolls’) Once we got along the Lake Superior side of the U.P. we drove through a short section of freezing fog that produced rime on the surrounding forest. Our tight schedule and road conditions prevented me from stopping to get photos but I found several on Wikimedia commons that illustrate the phenomenon.

Here’s a recent TV weather blog that provides some additional photos and information rime and hoar frost, which is a related winter weather phenomenon. Rime forms when air temperatures are below freezing drop below the dew point as the water condenses and freezes, the ice crystals accumulate on the windward side of trees, fences, and other objects. Another similar phenomenon is hoar frost. Hoar frost looks similar to rime but is lighter and not associated with freezing fog. It forms when surfaces cool below the dew point and ice crystals accumulate. Here are some examples of hoar frost we experienced a couple years ago here at MSU.

Good Stuff

Boy oh boy, what a fun day! People yelling at me from the left and from the right. But hey, I didn’t start doing what I do to make everyone happy. With that said….Nah, I don’t feel like attacking anyone today. Instead, let’s look at a good renewable fertilizer: Cotton seed meal. It’s got a reasonably good ratio of nitrogen to phosphorus and potassium — slow release of course. Basically a waste product given a meaningful purpose. And look at the label — no mycorrhizae or other gimmicks. Just pure, unadulterated, cotton seed meal. This is what I want on my garden.

Living with lichens

We often hear that the US needs to boost its investment in science education to keep up with rest of the world. While we often think in terms of physics and chemistry when we think of science, we need to remember biology and ecology fit in the mix, too.

I bring this up because of a call a received a while back from a homeowner. The gentleman was concerned /borderline distraught that he would have to remove a prized maple tree from his front yard because it had “peculiar growths all over the trunk”. I told him it was difficult to diagnose a tree problem sight unseen but if he could send me some images, it might help me out.

The photo did indeed make ‘the problem’ obvious.

The growths were lichens. Lichens do not harm trees but I’m sure an unscrupulous tree service could have easily convinced the homeowner his tree needed come out had he not contacted me first. Lichens are actually two organisms; a fungus and an algae that form a symbiotic relationship and function very much like one organism The algae part of the lichen is photosynthetic, and therefore they are able to produce their own energy and do not take any resources away from the tree. In fact, lichens often grow on non-living substrates such as wood, concrete, tombstones, benches and so on. If a homeowner observes a dead tree or dead branch covered with lichens on it, this is a coincidence; the lichens did not cause the branch or the tree to fail. The tree trunk or branch simply provides a porous surface for the lichen to attach. Lichens are often fairly inconspicuous, but in some moist areas, such as the Pacific Northwest, they may form a mat that completely coats branches.

Fast facts about lichens

Lichens grow in some of the most inhospitable places on earth from deserts to tundras.

Lichens are commonly grayish-green, but may also be yellow or red, depending of the type of algae associated with the fungus.

Lichens are sensitive to air pollution, and researchers are investigating their use as a bio-indicator of air pollutants such as sulfur dioxide and ozone.

Lichens are fascinating organisms, if you are taking a liking to lichens try these websites:
http://www.nmnh.si.edu/botany/projects/lichens/
http://www.ucmp.berkeley.edu/fungi/lichens/lichens.html

Thomas Knight and the Water Wheel

Classes have begun, and this semester (and every spring semester) I have the opportunity to teach our introduction to horticulture class, otherwise known as Plant Propagation (Hort 1001). We usually have about 120 students, and I don’t want to brag or anything, but it is just about the best class out there. Watching the students learn about seeds, cuttings, and grafting in the labs is one of the most motivating things about my job (and it doesn’t hurt that the greenhouses are about 70 degrees while it’s 0 outside). But, as you might expect, there is a lecture too. Believe it or not, the lecture isn’t half bad. In fact, students actually ask questions in class. This past Tuesday during a lecture on seeds one of the students asked how the roots know how to grow down when they exit the seed. The answer is geotropism. Geotropism is a response by a plant to gravity. Some parts of a plant grow towards a gravitational pull (roots), and some grow away from it (shoots). One of the coolest experiments ever was a study done by a gentleman named Thomas Knight in the very early 1800s where he set up a water wheel which had seeds planted along the edges. As the wheel spun and the plants grew they responded both to the Earth’s gravity and to the force created by the spinning wheel. You can see the results below.

Knight also did some very interesting work showing that buds from older plants retained their physiological age when grafted onto younger plants. Basically that means that if you graft a bud from a mature ‘Honeycrisp’ apple onto a young seedling, that bud will produce a new shoot which produces ‘Honeycrisp’ apples before the rest of the tree produces apples.

Usually when we think of horticulture we think of L. H. Bailey – and we should – but let’s never forget Thomas Knight either.

Pussy Riot: How far should we go to eliminate destructive alien species?

A short article in our Sunday paper caught my eye this weekend. New Zealand economist Gareth Morris has launched a campaign to eliminate domestic cats from the country in order to preserve native bird populations. According to Morris and his supporters, cats represent a serious threat to many rare and endangered bird species in New Zealand, which has the highest rate of cat ownership in the world. Ironically, one of the reasons the article our paper caught my eye is I have been considering adopting a feral cat from a local program to control mice in our barn.

So, what do you think? Are cats useful companions and mousers or do you agree with Morris that they are ‘natural born killers’ that need to be eliminated?

Balance

By this time most of you have probably read all about Mark Lynas, the anti-GMO activist who decided that GMOs are actually a net benefit to society. I’ve been asked by a few people to comment on how I feel about Mr. Lyna’s changing sides. I think they expect me to be jumping up and down for joy. But that’s not how I feel at all. I’m happy when anyone decides to let research lead them to a conclusion rather than politics or gut feelings, but in this case it also makes me nervous. This is because some people tend to travel too far towards one side or another. I’m just as fearful of the damage that people who are radically pro-GMO may cause as I am of radically anti-GMO activists. And, in my opinion, this guy just seems to be radical. Saying that you have research that supports one side of an argument is fine, but in almost all cases there is research that supports the other side too, and you ignore it at your own peril. Balance people — Balance.

Where did the 10-20-30 rule come from? Is it adequate?

We’ve been having an interesting discussion over on the Urban Forestry group on LinkedIn on the origins and suitability of the 10-20-30 rule for tree diversity in urban forests. For those that aren’t familiar, the 10-20-30 rule is a guideline to reduce the risk of catastrophic tree loss due to pests. The rule suggests an urban tree population should include no more than 10% of any one species, 20% of any one genus, or 30% of any family.

The first published reference to the 10-20-30 rule (often referred to as just the 10% rule) was by late Dr. Frank Santamour, Research Geneticist at the US National Arboretum in his paper Trees for urban planting: Diversity, uniformity, and common sense, which was presented at the 1990 Metropolitan Tree Improvement Alliance (METRIA) conference. While Santamour is commonly credited with the 10% rule he notes in his paper, “I am not sure who first propounded the “10% rule”, nor am I sure that anyone would want to take credit for it, but it is not a bad idea.”

The other question on the LinkedIn discussion is whether the 10-20-30 rule is adequate to ensure genetic diversity in urban and community forests. My personal is opinion is that the rule is inadequate but far preferable than the status quo in most communities. If we consider the current issue with emerald ash borer (EAB) in North America, following the 10-20-30 rule means we would accept the loss of 1/5^th of our urban canopy since both of the commonly planted ash species (Fraxinus pennsylvanica or F. americana) are highly susceptible to EAB. On the other hand, many community tree populations the US currently include 30% or more maples, so 10-20-30 would actually be an improvement.

A limitation to the 10-20-30 guideline that Santamour acknowledges is that the rule does not afford protection against insects with a broad host range such as gypsy moth or Asian long-horned beetle. However, while these pests can, and have, caused widespread damage they do not appear to threaten nearly total annihilation of an entire species or genus ala specialists such as chestnut blight, Dutch elm disease or EAB. Moreover, a wide diversity of species is still a better defense even against generalist pests, unless you happen to get lucky and plant a monoculture of the one tree they won’t destroy.

One of the inherent challenges in the 10-20-30 rule is implementation. What is the tree population in question? Are we talking about a city? A neighborhood? A block? If there are 10 trees on a block do they all need to be different species? Some have proposed corollaries to 10-20-30 such as the “Look around rule” (or “Look around, fool!” if you prefer the Mr. T version). This guide states if you’re getting ready to plant a tree; look around and if you already see that tree, plant something else. The problem with diversity on a very small scale is we can end up with the ‘menagerie effect’ – one of these, one of that, one of those – that often lacks aesthetic appeal. Ultimately this becomes a challenge for urban foresters and designers working together; how do we incorporate diversity guidelines within established design principles.

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Over-Interpreting

One of the things that scientists need to be able to do is to figure out what the research that they conduct means without over-interpreting it. This isn’t as easy as it seems, for example, if a particular pesticide at a particular dose kills mice, then should it also kill humans? Without testing we really don’t know – though we certainly have suspicions. If we allow our suspicions to take over and we say that, based on the mouse data, the pesticide necessarily does or doesn’t affect humans then we’re over-interpreting. Most (dare I say all?) scientists have been guilty of over-interpreting their results – or the results of others — at one time or another in their careers. It’s a hazard that comes with the job. Unfortunately it’s a hazard that comes with journalists jobs too — often over-interpreting what scientists say. Recently I had the opportunity to see an online lecture (a TED lecture) on this very topic and thought it was worth sharing.

Planting Edibles in Cities

The snow has just started falling and I’m already thinking about what I’m going to be planting next spring. Most of my plantings won’t be at my own house, they’ll be out in the cities of St. Paul and Minneapolis. We’ll be looking at all kinds of fun stuff like growing trees in various new types of containers, adding compost to planting holes in different circumstances, and even pruning methods. But one of the big things that we’re starting to look at are new trees for the urban environment. Cities have always spent time considering what they plant, but with the emerald ash borer ravaging the Midwest, now they’re thinking even harder. And because of the local food movement, suddenly the cities are at least considering trees like apples and hazelnuts on a trial basis (sure, there are some places that use them here and there, but they’re less than common). Of course, if this movement stalls, the cities would be upset at having so many “messy” plants around (that’s their big concern about edibles right now), but I don’t think it will. I’m actually pretty optimistic about using fruits and nuts on public property. Sure, some plants will fail because they get too many diseases or insects, or because they’re weak wooded, but some will make it too. I think hazelnut has a great chance in the right place (it would be too bushy for most boulevards….). Do any of you have a favorite edible that you think might work well in a city? Let me know, maybe we’ll try it!