Which side of the tree's rings are dense and which side is sparse?

The tree rings on the shady side facing north are obviously dense, while those facing south are sparse. The south side of the trunk is exposed to more sunlight and grows rapidly in the radial direction, so the direction can be identified in the field by the density of annual rings.

I. Concept

Concentric rings on the cross section of perennial woody plants. Trees and shrubs common in temperate zones, usually once a year. In temperate regions, the boundaries of tree rings are obvious. In the tropics, because the climate changes little in a year, the annual rings are not obvious.

Second, the causes

Tree rings are produced by the annual activities of the cambium. The mild climate and abundant rainfall in spring are beneficial to the growth of trees. This is because the cambium cells divide vigorously, the newborn cells are large and obvious, and the ducts are large and many. Therefore, the wood looks light in color and soft in texture.

After summer, as the temperature rises. Rainfall decreases, especially in autumn, the weather is getting colder and colder, the rainfall is less, the cambium activity is weakened, and the shape of splinter cell becomes smaller. In addition, the cell wall is thick and there are few ducts, so the wood looks dense and hard, and the color is dark.

Third, the influencing factors of width

1. Genus of tree species: Poplar and Populus tomentosa have wide annual rings, while Boxwood and Cornus officinalis have narrow annual rings.

2. Tree age: The annual rings formed by trees are wider and wider at the initial stage of growth, but gradually narrow with the growth of tree age.

3. Living environment conditions: For example, the average annual ring width of the shrub Betula platyphylla in Greenland at 73 degrees north latitude is less than 0.05 mm, but in a botanical garden in Central Europe, the average annual ring width of the same kind of small Betula platyphylla is 1.6 mm.

1904 One day, Douglas visited a farmer's house, and an old stump in the yard caught his attention. The surface of this old stump has blackened with age. He carefully observed its annual rings and found that one ring was very narrow, which he thought was caused by the long-term drought that ended in 1883. There is also a 1 1 ring outside this ring.

He asked the host if the exact time when he saw the tree was 1894. The host was very surprised because what he said was not bad at all. Through this incident, Douglas realized that checking the types of tree rings can tell the local meteorological conditions in the past.

Soon, a new scientific field-dendrochronology was established in his factory. Tree chronology is a subject that studies the past meteorological types with tree rings as the time standard. Dagrass also established the annual ring research laboratory at the University of Arizona.

First, the application of tree rings.

1. Calculate the age.

Tree rings represent the periodic changes in the growth environment of trees, usually followed by an annual change cycle, so tree rings also represent the growth in a year. According to the tree rings, we can infer the age of trees, which can be used to examine the age of forests.

2. Understand the climatic conditions for one year.

The width of tree rings can help us understand the experience of trees and the relationship between trees and the local environment and climate at that time. Under favorable climatic conditions, trees grow well, xylem increases more, annual rings are wider, and vice versa.

For example, the initial rings of trees are generally wide, indicating that the trees at that time were young and vigorous; Sometimes, after a tree has many narrow rings, it suddenly appears wide rings, which shows that the environment and climate are suitable for the growth of the tree in those years when the rings are wide. Eccentric rings indicate that the environment on both sides of the tree is different. Usually, the southern side of the northern hemisphere is warmer than the northern side, so the rings on one side are wider.

Second, the classification of tree rings:

1. Early wood (spring wood)

Wood forms early in the growing season. Early wood is crisp and light in color because of its large cell gap and few cell fibers.

2. Late timber (summer timber, autumn timber)

Wood forms in the late growing season. Late wood has small cell gap, many fiber components and many cell deposits, so it is dark in color and dense in texture. From early wood to late wood, it changes gradually with the seasons. Although the texture and color are different, there is no obvious boundary. But last year's late wood is obviously different from the early wood of that year, and there are obvious boundaries to form tree rings.

Step 3 jump

In a tree ring, the boundary between early wood and late wood is obvious, and the color changes suddenly from early wood to late wood. Such as Pinus yunnanensis, Pinus massoniana, Hemlock, Larix gmelinii and so on.

Step 4: Gradient

In a tree ring, the boundary between early wood and late wood is obvious, and the color changes gradually from early wood to late wood, such as fir and spruce wood.

5. Special case-fake tree rings

Multiple annual rings produced on the stems of woody plants in a year. The emergence of artificial tree rings is due to the characteristics of plants and the influence of external environment. The former, such as citrus plants, can produce three annual rings a year, while the latter, such as abnormal climate or insect pests, appears many times of alternating cold and warm or falling leaves, which makes the cambium activity fluctuate obviously, causing many times of growth and changes and forming many concentric rings.

References:

Baidu encyclopedia-annual rings