Pawpaw, Asimina triloba, is a small understory tree very common in Appalachian forests. The fruit, prized by people and possums alike, has a custardy texture and flavor. The fruit, as well as the tree, is called Hoosier banana, at least in Indiana. Pawpaw is a member of the family Annonaceae, an important family of mainly tropical trees and shrubs. Pawpaw has many tropical characters, from its strange purple flowers to its broad, undissected leaves.

Here are some photos of the amazing flowers and young fruit of pawpaw. Click the pictures for really big images. The purple flower is especially glorious at full screen.

Have you every looked closely at tree leaves in spring?  Our eyes are drawn to showy flowers and flitting birds, but a close look at emerging leaves shows some astonishing beauty. The most interesting thing about spring leaves is the intricate folding.  Leaves are often folded in half (as in redbud and hickory) or have complicated, compact folding schemes (as in oak and ash). Watching leaves emerge from their tight folding in buds to become full-grown leaves is fascinating.

Next time you are outside, have a look at some growing leaves. Visit the same plants over a few days and you will be amazed at the rapid changes you see.

Here are a few pictures of spring leaves in development (I will add more later).  Click on the pictures to see a high-resolution version.

bitternut hickory, Carya cordiformis. Leaflets are folded in half as the rachis (leaf stem) grows.

Yellow buckeye, Aesculus flava. Leaves emerge with the flowers. Leaflets are tightly rolled.

Eastern redbud, Cercis canadensis. Leaves are folded in half as they emerge, quickly unfolding.

northern red oak, Quercus rubra. Bright red leaves are compactly folded along sinuses. The leaves transition from red to green as they unfold.

Two pictures of green ash, Fraxinus pennsylvanica.  Leaflets are folded in half and folded against the rachis, spreading and unfolding as they develop.

Sumatra oak, Quercus sumatrana the southernmost oak, Sumatra, Indonesia. The buttresses and surface roots are typical of many tropical trees. Photograph by Tom Kimmerer

Most people eat a few pecans year round, but pecan consumption peaks at the holidays. At this time of year, you can usually get new harvest pecans from the fall harvest. This year, though, pecan production is well down, and there are not enough current year pecans to meet demand. Not to worry, though. Pecan farmers still have plenty of nuts stored from last year, and they are perfectly good. Properly stored, pecans will keep for years.

Why the meager crop this year?  Part of the reason is the dry spring in many pecan producing areas in Texas. But the major reason is tree biology.

Pecans, like many nut-bearing trees, are mast-fruiting species. These trees bear heavy crops in alternate years, or at greater intervals. Mast fruiting is probably a result of two factors.

The first is resource availability. A tree that bears a very heavy crop in one year may not have the resources to bear heavily the following year. Heavy mast years tend to occur over wide ranges of a species’ range.  Since 2007 was an exceptionally good year for pecans, it is no surprise that production was down this year.

The second reason that trees don’t bear heavy crops every year has to do with seed predation.  If trees bear heavy crops every year, predators such as squirrels, weevils and birds will have a reliable source of food to support large populations.  By bearing heavy crops at irregular, unpredictable intervals, trees can avoid building up large populations of predators. 

More on mast fruiting in a future post.

Species in this post:

pecan, Carya illinoinensis, Juglandaceae.  Sometimes described as C. illinoensis, but this is an invalid name.

Meager pecan crop saved by last year’s nuts | Business news | Chron.com – Houston Chronicle

Whitebark pine, Pinus albicaulis, is one of the most characteristic species of high mountains in western North America, and one of the most unusual pines.  Whitebark pine populations are declining steeply throughout the northern Rocky Mountains. The Billings Gazette has an excellent article about the decline of whitebark pine in the northern Rockies. In the Greater Yellowstone Ecosystem, whitebark pine populations have declined from 7% to 24%. In a sign of things to come more than half the trees monitored since 2002 have died. In a monitored area in the panhandle of Idaho, 98% of the trees have died.  Whitebark pine is a species at risk in Canada and a species of special concern in Washington. The cause of the decline is a complex mixture of disease, insects, fire suppression and climate change.

The loss of whitebark pine threatens other species in the Rockies. Grizzly bears depend heavily on the fatty seeds of whitebark pine for fall nutrition. While grizzlies can find other food sources to replace the pine nuts, a lack of seeds may force the bears to wander to lower elevations and come in more contact with humans.

Whitebark pine is also a critically important species for birds, notably Clark’s nutcracker.  Whitebark pines, unlike all other North American pines, have closed cones that have to be pried open by animals. Clark’s nutcracker pries open the cones to get at the rich seeds, dropping many of the seeds in their travels. 

The loss of whitebark pine would be a tragedy for mountain ecosystems throughout the West. But efforts to study and restore the species are fraught with challenges. Most populations of whitebark pine are in roadless areas and at very high elevations. Getting to stands to study them, or to restore populations, is not easy.  Because whitebark pine is not a commercial species, having no timber value, it is hard to come by research funds or restoration money. Centuries of effort will be required to restore whitebark pines, and climate change may quickly overwhelm efforts and restoration.

There will be a lot more information about this interesting and significant species as we develop the species pages at Trees, Climate and People.

Picture: whitebark pine, Pinus albicaulis. Picture by Paul Bolstad.
Map: Whitebark pine, Pinus albicaulis, range

BillingsGazette.com :: Trees on the brink: Whitebark pine face series of threats

Universiti Putra Malaysia (UPM) will create a model forest to include 400 species of Malaysian forest trees on a 27 hectare site near the campus in Serdang and on a 48 hectare site at the Bintulu campus in Sarawak.  The project will receive nearly $400,000 in funding from Mitsubishi Corporation. Deputy Dean Dr. Mohamad Azani Alias said that the purpose of the project is to plant trees of species that are rare and endemic, found only in certain states.  This promises to be an important project for the future of Malaysian trees.  With over 9,000 species in Peninsular Malaysia, the tree flora of Malaysia is incredibly rich, but many species are poorly known and their conservation status is uncertain.   By creating a refuge near campus for these uncommon species, UPM will be able to increase its efforts in the conservation and biology of rare tree species.  With climate change creating uncertain effects on tree distribution, conservation of rare and endemic species is particularly important.

Note: I am a former visiting lecturer at UPM.

Picture: Canopy shyness in upland dipterocarp forest, Malaysia. Picture by Tom Kimmerer

A private company, GreenTrees, is creating long-term contracts with landowners in the Lower Mississippi River Alluvial Valley, including Western Kentucky, to plant forests of cottonwood and other hardwoods. The purpose of the project is to create value through a combination of biomass production for industry and carbon sequestration opportunities. Carbon sequestration will create income streams through trading in carbon cap and trade markets.

In exchange for leasing the land to GreenTrees, landowners receive up-front payments, timber harvest income, recreational income, carbon-based income, and appreciating property values, as well as federal and state conservation incentives and payments.  Landowners can engage in these kinds of activities on their own, but they can’t tap into the up-front income offered by GreenTrees.

The Lower Mississippi River Alluvial Valley was a richly forested region until the 20th century, when bottom-land farming of soybeans cleared vast areas of land.  These lands are in the long run more valuable for carbon storage and watershed protection than crop production.

Stay tuned for more information on this interesting development.

Green-Trees.com

Cross posted at Sustainable Kentucky and Tree Trends.

The beautiful Dawes Arboretum in Newark, OH, lost  many trees last weekend in the high winds at the edge of Ike.  Winds up to 70 mph knocked down exposed trees, and when those trees came down, they took other trees with them.

Dawes lost 32 trees from their collection, including many sugar maples (Acer saccharum).  A 100-ft tall white oak (Quercus alba), estimated at 200 years old, cam down, taking out several Silician firs.

In areas of the arboretum where proper pruning had been completed, there was much less damage.

Links:

• 200-year-old white oak at Dawes among many trees felled in storm | newarkadvocate.com | The Newark Advocate
• Dawes Arboretum

Jordan, one of the driest countries in the world, has long produced valuable olive trees irrigated by spring and well water. Prolonged drought in southern Jordan now threatens to kill up to 30,000 trees around the southern city of Karak. Farmers have no access to irrigation water as springs and wells dry up.

Jordan is one of the 10 most water-poor nations. The only major river, the Jordan, has turned to a small stream after tributaries were diverted by Israel for agriculture. Rainfall, and rain-fed springs and wells, are the only water source for the nation.

It appears likely that climate change, reducing rainfall in this already-dry region,  is interacting with political disputes over water to cause the death of these valuable trees.

Links:

• JORDAN: Drought may claim thousands of olive trees
• Jordan River Dispute. ICE Case Study 6

Hurricane Ike knocked down trees from Texasto Northern New York over the weekend. Here in central Kentucky, we had no rain, but strong winds up to 60 mph knocked down trees throughout the region. Falling trees knocked down power lines, leaving more than 39,000 homes without power, according to the Lexington Herald-Leader.

I looked at many downed trees and broken limbs this morning around Lexington. All of the downed trees that I saw had major stem defects and all of the broken limbs had significant decay. Although we often blame power outages on downed trees during storms, we really should blame downed neglected trees. In a major storm, like Ike in Houston, even healthy trees will be broken or uprooted. However, in more moderate winds, most of the trees that fall or break have major decay and other defects. The power outages and economic loss in many storm-damaged communities represents the long-term cost of deferred maintenance on city forests.

Update:  According to Governor Steve Beshear, more than 550,000 Kentuckians were without power Sunday, including 90% of northern Kentucky customers of Duke Energy.

Cross posted at Sustainable Kentucky/Green Kentucky and Tree Trends.