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Water: The Lifeblood of the Forest In the summer, water reigns supreme
and the forest biomass As the local glacial ice melted 12,000 years ago, Paleo-Indians followed caribou herds annually as they migrated through present-day Durand Valley, across a tundra-like treeless landscape. The forest vegetation we see today was then just beginning to take shape—slowly—as plants and trees “migrated” from the south with the warming climate. Maples for example, showed up here approximately 8,000 years ago. A key factor in the increase of species was, along with the warming climate, the availability of liquid water. How water flows through the earth and atmosphere, at any location, governs the biological nature of the landscape. In our location today—halfway between the equator and the north pole—the climate is moist and temperate with much of the year warm enough for water to flow and nourish. With a wide range in temperature from summer to winter, animal and plant species found here have adapted to seasonal extremes with strategies that call for fighting or fleeing when water—therefore food—and favorable weather become scarce.Water, in the liquid form, is scarce in the winter, hence the relative lack of plant and animal activity. In the summer, water reigns supreme and the biomass of the forest increases dramatically. In the spring and summer months, streams and bogs define much of the trailside landscape along Pasture Path and the Four Soldiers Path. The coolness of mountain stream water helps cold-blooded fish and aquatic insects because colder water holds more dissolved oxygen. The warmer the water, the less oxygen it can hold.Warm water tends to have excessive algal growth, which decays and takes away oxygen, making slow running water cloudy and brown. This isn’t a problem here—abundant overhanging vegetation along the stream bed and spring-fed water, help keep streams cool. However, as our climate continues to warm here in northern New Hampshire (three degrees Fahrenheit in the last 100 years) mountain stream water will warm, too, causing changes in water quality. Water quality also depends on current. The steeper the slopes, the more oxygen in the water. Like a giant mixer moving air into the water, the flow over the rough terrain not only oxygenates the water but also picks up soil run-off and nutrients from decomposing plants and animal matter. An efficient solvent, moving water can create a mix of vital, invisible, dissolved nutrients, also known as liquid soil, even though it appears clear. A good indicator of this “healthy” water is the presence of stream insects, usually found under rocks and logs. Caddisfly, stonefly, and mayfly larvae indicate a healthy stream because they can’t tolerate pollution. These insects also provide food for fish, birds, and amphibians. Streams concentrate the essential ingredients of life within their waters. Intermittent streams are those with discernible channels, that show evidence of annual soil deposition or scouring, but do not flow year- round. They occasionally leave stagnant puddles and pools in the drier season. There are several intermittent streams along the Four Soldiers Path. Forest mammals use intermittent stream beds as travel corridors, within and between watersheds. Food is often abundant in these areas, as are good locations for dens. Intermittent rivers or stream banks remain cooler than surrounding hill slopes, so they may act as thermal refuges for fisher, marten, and other secretive boreal species. Bats are even more closely associated with riparian areas because they require pools of water from which to drink, they also eat insects associated with aquatic and riparian environments. Dragonflies can be seen whizzing down Carlton Brook on mid-summer evenings, riding the flow of cooler air sinking down to the valleys as night approaches. Intermittent streams, however, have been abused. They were not consistently protected from land-use disturbance in the past. Tractors occasionally used them as skid roads, and trees were commonly yarded across them. These sites frequently accumulated large volumes of logging debris and, so, were likely to support intense fires when the debris piles were burned. The logged areas along the Four Soldiers Path near the “Eye of the Needle” spur at the height of lanf were harvested appropriately, limiting damage. Vernal pools are intermittent pools that provide habitat for a short period of time. In the fall and winter, vernal pools fill with water from rising groundwater, runoff, rain, melting snow, and seasonal flooding. By mid-August, they are generally dry. By definition, however, vernal pools are not found in dry streambeds. Dense stands of trees can delay warming of the pool water and slow evaporation. Because of dry or low water conditions and winter freezing, vernal pools are free of predatory fish. These fish-free waters are perfect habitat for amphibian and invertebrate species that have evolved to take advantage of the relative safety of vernal pools. Some of these animal species, such as spring “peepers,” require vernal pools for their life cycle and are found nowhere else.
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