Archive for February 6th, 2007


The  following article was taken from the San Francisco Chronicle, dated January 27, 2007. I found it to be quite fascinating.  All the trees in the lower part of the picture grew up under the shadow of a rock.  This provided them with shelter, protection and even more nutrients than if they had grown up alone.  I can see a perfect correlation between this and our walk with God.  Jesus is our ROCK.  And if we stay close to the ROCK, we will grow and flourish, just as these trees have. 

Moss grows on the north sides of trees. Everyone who sets foot beyond a trailhead knows that. But there’s more to that ecological truism than providing two-footed adventurers with an organic compass. There is no place where this north-side microecology is more intriguingly displayed than in Yellowstone’s “buddy” rocks. In the northern part of the park, away from the geysers and bubbling mud pots that gather the big crowds, there is a boulder-strewn bench above the Yellowstone River. Some of the rocks there are the size of the motor homes cruising by, but most are between wolf and bison size and have a Douglas fir tucked up beside them so close that the tree seems to have an embracing branch around the rock. To a geologist, these rocks say the valley was recently, as geologists measure time, visited by a glacier. With all the volcanic action in Yellowstone, the park’s glacial history doesn’t get much notice, but not long ago the area we now call a national park was covered by an ice shield several thousand feet thick. When the ice finally melted and retreated back to the Beartooth Mountains, it left the rocks behind. Technically, the boulders are called glacial erratics. This is debris that fell into the slooow-moving ice in one place, only to be deposited in another place when the ice melted. The ice retreated from this area 13,000 years ago. The trees that grow in the northwest shadows of these rocks know and care nothing of glaciers, though. They “know” only survival, and here survival is chancy at best. The plateau is exposed, windy and dry. Much of Yellowstone’s north country is sage grassland just like it. Were it not for the shelter of the rocks, there would be no trees here at all. The boulder field is above 7,000 feet. At that altitude the atmosphere is less dense and doesn’t filter sunlight well. Exposed tiny tree shoots can be burned and dried easily in summer and torn by wind-rocketed ice crystals in winter before they can spread their limbs. But these trees have big buddies that stand up to the wind and sun for them. Life-giving moisture, precious and spare in the Rockies, is more abundant in the shade of the rocks. Exposed big rocks also tend to absorb and hold heat better than does open ground. This leaves the ground at their bases ice-free longer than open ground. Just as sand accumulates in river eddies, bits of plant and animal matter accumulate in the lee of the rocks and provide vital nutrients to seedlings setting down roots. So seeds have a better chance of germinating and surviving their first vulnerable years if they fall on the northern side of one of the buddy rocks. Douglas fir seeds, smaller than a grain of rice, have sails on them that catch the wind. Wind currents speed up as they rush over the leading edge of a rock but slow again in the rock’s lee. Simple physics, really, but a reality that increases the chances of a fir seed landing in the haven of a buddy rock. The trees here do not grow quickly. Some have been buddied up as you see them for a hundred years or more. In that time they have seen many bison and elk pass. The relationship between the park’s large mammals and trees is far from benign. In some parts of the park, the animals are as dangerous as fire or insects. Elk and bison are tree rubbers. Male elk scrape the velvet from their antlers and sharpen the tines by rubbing them against rocks and trees, most often removing the tree’s bark with the velvet. Bison scratch off their summer and winter fur each season by rubbing against whatever is handy, usually trees. But, for reasons no one has been able to sort out, Yellowstone’s buddy trees show no signs of having been victimized by elk or bison. Somehow, big brother rock has protected them from the beasts as well as the weather. Look closely at the photograph above. Every tree you see there has a buddy. Even the protoforest in the background is sheltered by the hill. Yet as obvious and intriguing as the field of buddy rocks is, millions of park visitors pass it every year without noticing. It’s like the way moss grows on trees. We can know and not notice. Freelance writer “Digger” Jerry George sends his journal “letters” home to the Bay Area from Yellowstone National Park — or wherever he happens to be observing nature. E-mail him at home@sfchronicle.com.   

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