Sunday, March 13, 2011

Needle Grass

What’s happening: New leaves on oriental poppies, south facing hollyhocks, dandelions and June grass; small leaved soapwort and yellow evening primrose leaves turning green.

What’s green: Evergreen, yucca, grape hyacinth, Jupiter’s beard, gypsum phacelia, pink evening primrose, winecup, tansy and tumble mustard. broom senecio, snakeweed, black-eyed Susan, chrysanthemum leaves; cheat and needle grass.

What’s grey, blue-grey or grey-green: Piñon, four-winged salt bush, stickleaf, yellow alyssum and winterfat leaves.

What’s red/turning red: Cholla, Madonna lily, golden spur columbine, beardstongue, creeping mahonia leaves; rose and young tamarix stems.

What’s yellow/turning yellow: Globe and weeping willow branches.

What’s blooming inside: Bud on pomegranate; new growth on asparagus fern

Animal sightings: Rabbit; small brown birds back in peach.

Weather: Clouds that hovered for several days finally dropped some water Monday night; snow lingers in Jemez and Sangre de Cristo; 12:09 hours of daylight today.

Weekly update: The first sign of spring on the prairie is new growth at the base of the needle grass. Sandy brown tops still dominate the horizon, but new shoots are emerging among stalks that themselves are greening below.

Even so, there’s probably more going on underground than above at this time. As the perennials increase their photosynthesis, mycorrhizal fungi gather round the roots to absorb carbon. In exchange, they pass through phosphorus they’ve extracted from the soil that’s needed by the grass to produce DNA, RNA, cell walls and energy transport systems.

The symbiosis is as old as land plants. They’ve found fossils of fungus associated with other plants in the Rhynie chert beds of Scotland that date back 400 million years ago. By the Miocene, when grasses were emerging, the mycorrhizae had assumed their modern form. Hesperostipa comata migrated from the neotropics into our region before the end of that era.

While the cool season bunch grass is dependent on the existence of the small organisms, the range of the fungi is limited by the presence of phosphorus. The structure of the plants varies by the amount of the available mineral. However, they cannot tolerate the high levels introduced by farmers.

The fungi also die when animals eat the blades, thereby decreasing the volume of carbon fed to them. Gabor J. Bethlenfalvay and Suren Dakessian compared plants growing in adjacent protected and unprotected areas on a recovering range. They found leaves on grazed plants only appeared around the perimeter of the crown, while uneaten plants produced full tufts with “hundreds of well developed leaf blades.”

They also found phosphorus levels were lower in the ungrazed soil, a measure of the presence of vesicular-arbuscular mycorrhizal fungi. When the tiny organisms disappear, there’s nothing left to provide vital nutrients. The shallow, fibrous roots decline in weight, though not as much as the greens they support.

Ranchers are told it’s safe to graze their animals on needle grass in early spring, when it’s one of the earliest plants available, and again in fall, when it’s resumed growth after the monsoons. The stalks cure well, and are considered good winter feed.

Most cattle and sheepmen move their animals when seeds develop in late spring, usually early May here. Not only do the seeds have harpoon points that break off when they embed themselves in skin and wool, but they’re carried by long tails that twist with moisture.

After the seeds are ripe, the grasses go dormant during the heat, and their protein levels drop. It’s then that continued grazing destroys life above and below ground, to little benefit of the mammals.

Once the grass dies, it takes at least ten years to come back, even when carefully seeded and watered. After that initial period, stands still only expand slowly.

In my yard, the overgrazed sections may never revive. One reason may be that, despite the long life expectancy of the seed, not many actually accumulate in the soil. In addition, those seeds that do survive need cold to emerge and possibly fire. Robert Blank and James Young found seeds germinate better when the soil is heated more than 500 degrees or they are exposed to smoke.

Only some of those conditions will be met here.

Bethlenfalvay, Gabor J. and Suren Dakessian. “Grazing Effects on Mychorrhizal Colonization and Floristic Composition on a Semiarid Range in Northern Nevada,” Journal of Range Management 37:312-316 :1984.

Blank, Robert R. and James A. Young. “Heated Substrate and Smoke: Influence on Seed Emergence and Plant Growth,” Journal of Range Management 51:577-583:1998.

Dick-Peddie, William A. New Mexico Vegetation, 1993, on needle grass as neotropic-tertiary flora.

Wikipedia. On-line entry for “Arbuscular Mycorrhiza.”

Zlatnik, Elena. “Hesperostipa comata,” 1999, in United States Forest Service, Fire Effects Information System, available on-line.

Photograph: Needle grass at the edge of my drive with greening stalks and new sprouts, 12 March 2011.

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