Sunday, February 22, 2015

Estremaduran Oak

Weather: Last rain 2/11.

What’s still green: Juniper, piñon, and other evergreens, yuccas, rose stems; leaves on grape hyacinth, Japanese honeysuckle, alfilerillo. In the warm days green is pushing up along roadsides.

What’s gray: Salt bushes, winterfat, snow-in-summer.

What’s reddened: Cholla, twigs on peach, apricot, apple, sandcherry and sandbar willow; purple aster leaves.

What’s yellowed: Young stems on globe and weeping willows; arborvitae have browned.

What’s blooming indoors: Zonal geraniums.

Animal sightings: Small birds.

Weekly update: The Estremadura is the part of western Spain that was home to the conquistadors and some of the people who moved here in 1588. It’s town names include Albuquerque, Guadalupe, Trujillo, and Herrera del Duque.

I’ve been reading about it to see if its environment influenced the attitudes of early Spanish explorers and settlers.

It’s a dry plain surrounded by mountains with one main river winding through the center, the Tagus and one flowing in the south, the Guadiana. A little over 18 inches of rain fall a year, most of it coming in winter.

Here we get about 12 inches, with most of it coming in the summer monsoons and some in the winter snows.

Nature has responded to the Estremadura’s Mediterranean climate with trees that have wide branching habits, extensive root systems, and leaves that fall in summer. The one provides shade that slows evaporation. The second holds dry soil from blowing away and traps water wherever it lands. The third carpets the ground in summer, at the same time it reduces stress on defoliating plants.

At one time, the Estremadura was covered by woodland. The most common landscape today is the bosque Mediterráneo dominated by evergreen Holm oaks (Quercus ilex). To the south, where the climate is warmer, cork oak (Quercus suber) grows in the shade of the mountain ranges.

When trees are felled in large numbers, dense scrub intrudes. Brooms (Cistus), lavenders, and mastics (Pistacia lentiscus) replace Holm oaks. Scrub thickets, strawberries and heather supercede cork.

When that second generation protective scrub is removed, single species like brambles, heathers and gorse advance. These are more tolerant of drought, poor soils, and bush fires.

Along the mountainous perimeter, deciduous trees grow in the bosque de montaña. Melojos (Quercus pyrenaica) are most common, but there also are chestnut groves and clumps of Portuguese oak (Quercus faginea).

Near the Tagus and its more permanent tributaries riparian species grow. In the higher elevations, the bosque en galería sports willows, osiers, and alders. Aspen and ashes replace them at lower levels. In the lower bosque de ribera bushes, oleanders, tamujo brooms (Flueggea tinctoria), and vines grow under elms.

The most important Estremaduran landscape is the dehesa, an open pasture that supports cattle and cereal production. The primary wild plants are winter annuals that bloom in spring, the purple viper’s bugloss, tolpis, andryala, corn marigold, and yellow chamomile. The first is a borage, the rest members of the composite family.

The dehesa may originally have been created by wild fires, but the open savannah has been maintained for thousands of years by humans. The oaks, especially the cork oak, have adapted. The latter produces a thick coat of bark every year to protect itself.

The only oaks I’ve seen in this area were Gambel oaks in the area of Bandolier. It was 13 years after the Cerro Grande Fire had scorched the bark. The tops had died back, and new growth risen from the roots.

Notes: Instituto de Educación Secundaria les Dr.Fernández Santana. "Vegetation of Extremadura," school web site.

Photographs: Quercus gambelii near Bandolier, 4 July 2013. The first was taken on a slope at 8,159'. The clump in the last was at 7,344'. The others were on flatter land at 7,047'.

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