Giant sequoias reach full height when they are between and years old. Can you imagine living that long? They can grow to be around feet tall and 30 feet wide. They are the largest living trees in the world! Because they grow so tall, sequoias grow bigger branches and thicker trunks to help them keep their balance. You can tell if a giant sequoia is mature if the top of the tree looks rounded, like this one.
Also, most of the low branches break off and fall to the ground, so the trunks are bare for to feet or more. Death of a Sequoia. Many old giant sequoias die after they fall to the earth in powerful storms. The trunk of a dead sequoia tree might lie on the forest floor for hundreds of years. Although the tree is dead, the trunk is teeming with life! Some theorize that older trees are less susceptible to ozone damage then younger trees. Older trees generally have lower levels of stomatal conductance, and therefore allow less ozone into the leaves, reducing the risk of injury.
Plants receiving less than optimal exposure to direct sunlight may experience a greater risk of injury from ozone or other air pollutants. With lowered light exposure, the plants are less able to compensate for the decreased photosynthesis and increased respiration levels caused by pollutants, so they absorb more pollutants and suffer more injuries.
Since giant sequoia is a shade intolerant species, it performs poorly in many urban areas, where buildings create large shadows and cloud cover may be greater than in rural regions. The higher temperatures common to urban areas are usually not a serious problem unless accompanied by extreme water shortages. Increased precipitation levels caused by urbanization may benefit giant sequoias. Soil compaction hurts them by decreasing the aeration and changing the drainage patterns of the soil, leaving the soil excessively wet or anaerobic.
Giant sequoia is generally propagated by seeds, which are subjected to cold stratification for about two months before being planted. Seeds should be planted approximately one-eighth-inch deep, and seedlings should not be exposed to direct sunlight for at least sixty days following germination.
This species is occasionally propagated through cuttings, which should be taken from young trees preferably under age twenty. The cuttings should be treated with the growth hormone IBA indolebutyric acid and placed on a mist bench to keep them moist. Photograph by RGT. Due to its majestic stature, giant sequoia should only be planted in areas with abundant space, such as in parks, on campuses, or in large gardens.
In such situations, a mature tree can be a strong focal point. Used in mass, giant sequoias can provide privacy, screening, or wind shelter near a building or home. Their shade can help lower energy use in nearby buildings. Giant sequoias, because of their great potential size, can also create problems in the landscape.
Falling limbs can damage buildings and other vegetation or injure people. The shallow roots may cause damage to sidewalks, home foundations, sewers, roads, and driveways, or could trip pedestrians. Mature plants may grow into power lines or buildings if not given adequate clearances to allow them to reach their full natural heights.
A variety of wildlife species utilize giant sequoias for food and habitat. Groves provide ideal habitat for such threatened or endangered species such as the spotted owl, pine martens, and fishers. Height growth up to 24 inches in one year is not uncommon. Sequoias have remarkably shallow roots. Despite their shallow roots, sequoias are resistant to toppling because roots spread out over large areas, sometimes up to half an acre in well drained soils. Of the mixed conifer species, the giant sequoia is the most resistant to damage from fire.
The wood is resistant to termites and other wood-eating organisms. This resistance to fire, insects, and disease accounts for their longevity and ability to grow to such mammoth proportions.
However, trees planted in nurseries and outside the giant sequoia's natural range are more susceptible to disease and insect damage. The wood from huge old-growth giant sequoia trees does not make good lumber, despite the its resistance to decay, because it is brittle and has little strength. Nevertheless, sequoias were logged in the 's and their wood was used for fenceposts and shake shingles.
Since the 's, most of the groves of giant sequoia have been protected by California state parks and Yosemite, King's Canyon, and Sequoia National Parks so that all Californians may enjoy their stately grandeur. Unfortunately, protection of groves from fire has reduced the regeneration of giant sequoia and pines, and led to an increase in the amount of California white fir.
Prescribed fire and mechanical seed bed preparation is one option for regenerating some groves, although such treatment is generally not consistent with National Park policy. Young growth sequoias, unlike old growth sequoias, have wood properties similar to young growth redwood and is suitable for lumber.
There have been successful plantations of the sequoia outside its natural range. In fact, the tree has grown vigorously when planted around the world. The seeds are quite susceptible to drought. You can put a glass plate or some plastic foil over the pot, but you have to be careful not to kill them by making things too wet.
Small germinated sequoias die rather easy because of overwatering. I can tell you: it's a very sad thing to see baby sequoias wither away! To keep the ground moist but not wet, it's ideal to use a garden sprayer instead of a watering can. You can sow them all year round, but because the plants in temperate regions like Europe will grow best in summer, it might be best to do the sowing in early spring. Seeds that germinated here Belgium around Christmas, have not grown noticeably until spring.
How long does it take the seeds to germinate? Well, first of all it should be said that giant sequoia seeds have a very low chance of germinating. If a few from some twenty to fifty seeds germinate, you're already successful With bought seeds, the germination rate is higher but it's highly probable that more than half of the seeds will do nothing. The seeds germinate at the earliest a couple of days after sowing, but still can after months. Don't think things will not work out: patience is a virtue!
When a seed germinates, the first thing you see is a tiny, rhubarb colored stem, loop shaped.
0コメント