Category Archives: Observing Our Land

The Physics of Sap

by Barbara Walvoord

from Lathrop Lamp Post, March 30, 2017

A bruised branch we see in the woods these days is likely to be oozing sap.  As we drive through our countryside, smoke rising from a shack along the road tells us the inhabitants are “sugaring.” Those of us who don’t do our own “sugaring” trek to the Hadley Sugar Shack for pancakes drowned in real maple syrup.

Behind this common New England scene lie some amazing physics.  Sap flows because of carbon dioxide–yes, that gas we have too much of, causing climate change.  But inside a tree, carbon dioxide is essential. A tree has a problem–it has to get nutrients and water to its branches and roots, especially in spring when it’s trying to nourish new shoots and buds.  It can’t burn coal for electricity, as we do to move heat and water through our homes.  Instead, a tree uses the properties of carbon dioxide, and the spring changes in temperature, to push around the life-giving sap.

Sap flows through a portion of the outer tree trunk called sapwood. Sapwood consists of actively growing cells that conduct water and nutrients (sap) from the roots to the branches of the tree. During the Continue reading The Physics of Sap

Lathrop’s Resilient Forests

by Barbara Walvoord

From Lathrop Lamp Post March 9, 2017

Walking in our beautiful Lathrop forests gives us a sense of peace and timelessness.  Yet great stresses lie ahead for New England forests: buildings and roads; invasive plants, insects, and diseases; heavy deer browse; and climate change.  In a 2016 booklet, “Increasing Forest Resiliency for an Uncertain Future,”  the authors, from U Mass, U Vermont, and the USDA, identify these stresses and help landowners increase their forests’ “resiliency,” which the authors define as “The capacity of a forest to respond to a disturbance by resisting damage or stress and recovering quickly.”  Resilient forests have a diversity of tree and plant species, adaptable plants, a mix of old and young trees, ample deadwood, a variety of tree arrangements from dense to sparse, and ample regeneration of species, especially those adapted to future climate conditions (

Three recommendations from the booklet are especially salient for Lathrop: Continue reading Lathrop’s Resilient Forests

Building in the Wetlands has Begun!

by Barbara Walvoord

(from Lathrop Lamp Post of March 16, 2017)

At Lathrop, we human residents are mapping and flagging our wetlands so as NOT to build on them.  If our plans involve wetlands, our town Conservation Commissions, backed by state and local laws, will require us to submit descriptions and diagrams, notify abutters, post a notice in the newspaper, and appear at a hearing.

Meanwhile, ignoring the flags and the paperwork, Lathrop’s red-winged blackbirds, early harbingers of spring, newly returned from wintering in the south, are busy building their homes in our wetlands.

red-winged blackbird. By Andy Reago & Chrissy McClarren – Red-winged Blackbird, CC BY 2.0,

The nest is what Habitat for Humanity would call a “woman build.”  The nest site is low to the ground or water surface, among clustered stems of plants like cattails, alder, goldenrod, or blackberry.  Our builder weaves stringy plant material around several close, upright stems to make a platform.  Around and over this, she adds more wet Continue reading Building in the Wetlands has Begun!

Lathrop’s Vernal Pools

by Barbara Walvoord

(from Lathrop Lamp Post, Feb. 2, 2017)

Vernal pools are a unique and threatened habitat.  Lathrop’s east campus is very fortunate to have two just off the wide woods path, and one just off the southwest corner of the mid-woods meadow (map, see

A vernal pool, by definition, has no permanent above-ground outlet. It fills with seasonal rains, and it dries up in late summer, at least every few years.  That drying eliminates fish, who otherwise would gobble down small critters like fairy shrimp, wood frogs, and mole salamanders who can survive only in a vernal pool. Many other creatures use vernal pools for food or habitat.  

Jefferson salamander. . Photo by Virginia State Parks staff (SH Jefferson Salamander Uploaded by AlbertHerring) [CC BY 2.0 (], via Wikimedia Commons
Jefferson salamander. . Photo by Virginia State Parks staff (SH Jefferson Salamander Uploaded by AlbertHerring) [CC BY 2.0 (, via Wikimedia Commons
Some creatures spend their whole life in the vernal pool, laying eggs in the bottom that can survive both drying and freezing.  Others spend part of their life cycle in the surrounding forest. Marching to the pool to breed, many are crushed crossing roads. Continue reading Lathrop’s Vernal Pools

It’s a Mini-tree! It’s a Wildflower! It’s a Moss! It’s a Fern!

by Barbara Walvoord

(Originally printed in Lathrop Lamp Post Jan. 19, 2017)

Walking in our woods in winter, I often see these strange plants that look like miniature evergreen trees. Wondering about their name, I looked in my tree book. Nope.  Hmm.  My wildflower book.  Nope.  So I asked north campus resident Helen Armstrong, who knows a heap about native plants, and she said, it’s Lycopodium obscurum, commonly called tree club moss, though my web sources classify it as a fern or “fern ally.”

The ancestors of our tree club moss were100 feet tall, growing 300 million years ago in the swamps of the Carboniferous geological period, rising among the early amphibians, spiders, and 800 types of cockroaches, and then falling, eventually to form coal. Continue reading It’s a Mini-tree! It’s a Wildflower! It’s a Moss! It’s a Fern!

Secret Tunnels Revealed at Lathrop

By Barbara Walvoord

(First appeared in the Lathrop Lamp Post Jan. 12, 2017)

There are secret tunnels all over the world–in Egyptian tombs, medieval buildings, prisons, battlefields, and under walls meant to keep people in or out.

Tunneling seems part of our DNA: When our grandchildren found a huge snowbank left by snowplows near our townhome, they set about digging a tunnel  into it. 

Our grandchildren only got a few feet, but there are yards, perhaps miles, of secret tunnels all over Lathrop land.  When the snow is deep, these tunnels, made by mice or shrews, are invisible to us.  But as snow partially melts, the tunnels become visible, and we can see how extensive is the under-snow life on our land. Continue reading Secret Tunnels Revealed at Lathrop

The Castle Abandoned, the Workers Dead, the Queen in Hiding

by Barbara Walvoord

Walking Lathrop land a few days ago, Sharon and I found this paper wasps’ nest hanging from a tree.

It looks like a tragedy from the tales of King Arthur.  This was once an elegant castle, with many chambers, many workers, and a pampered queen who was waited on foot and foot, never needing to  work–just lay eggs and bully all the other wasps so they know who’s boss. 

Now, in this winter photo, the nest is abandoned, full of holes, its walls shredding in the wind.  Its inhabitants are dead, including all the males and all infertile females.  The only survivors are some pregnant females, hiding out in the bark of a tree somewhere, trying to survive the cold. 

But the real story behind this wasps’ nest is a story of survival, regeneration, and nature’s rhythms.  If a mated female survives the winter (and many don’t), she will emerge in spring homeless. She doesn’t return to her abandoned castle, but starts a new home.  She chews wood and mud to build a tiny house with a few chambers, where she lays her eggs. When the larvae hatch,  she feeds and cares for them until they get old enough to shop, clean, do the dishes, bring her everything she needs, and build more chambers on the castle–all without having a sex life. Toward the end of summer, however, the colony starts producing fertile females and males, who then mate.  The guys then die, along with the unmated females, leaving only mated females, who leave the nest to hibernate,  and the cycle begins again. Continue reading The Castle Abandoned, the Workers Dead, the Queen in Hiding