/me? tn = baiduimage & ampct=20 1326592。 lm=- 1。 Cl = 2 & ampF7 can reduce water evaporation. Pine trees are evergreen, some of which are shrubs. Bark is scaly, with needle-shaped leaves and spherical fruits. The seeds are called pine nuts and can be eaten. Wood and resin are widely used. There are more than 100 kinds of pine trees in the world, all of which are fast-growing trees. In addition to the need for some shade at the seedling stage, people like light and fertile and moist soil during the growing period. The native native varieties in our province are Pinus armandii, Pinus tabulaeformis, Pinus bungeana, Pinus massoniana, Pinus Bashan and juniper, and the imported varieties at home and abroad are Larix principis-rupprechtii, Cedar, Pinus yunnanensis and Pinus sylvestris var. mongolica. Pinus sylvestris var. mongolica, Pinus elliottii and Pinus taeda. These tree species have different biological characteristics, some like warm and humid climate, and some like mild and cold climate. Some are cold-tolerant and drought-tolerant, while others are not cold-tolerant and afraid of drought. This paper mainly introduces the suitable cultivation range of several pine trees. L Pinus armandii, also known as Pinus armandii and Pinus pentaphylla, can be planted in Qinba Mountain area and some mountainous hills in Weibei. The annual average temperature should be lower than 15℃, and the annual precipitation should be 600-1500mm. It has strong adaptability to soil and can grow on mountain cinnamon soil, red yellow soil and red lime soil. However, the requirements for soil moisture are strict, and it is not resistant to drought, barren, saline-alkali and poor drainage. Pinus armandii is cold-tolerant, and can grow normally at the low temperature of -7- 10℃ or at the absolute low temperature of -3 1℃. Huashan pine tree is tall, with green needles and many cones. It is also a kind of dried fruit tree with rich nutrition and delicious taste. 2. Pinus massoniana, also known as Pinus tabulaeformis and Abies fargesii, is the main afforestation tree species in subtropical areas, and is only planted in some places such as the southern slope of Bashan Mountain and Qinling Mountains. Suitable for warm and humid climate, it grows in the place where the annual average temperature is 13-22℃ and the annual precipitation is more than 800 mm, and it is not tolerant to low temperature. Young tree needles will wither in winter at-15℃. Pinus massoniana is not strict with soil requirements, is drought-resistant and barren, and can grow in clay, sandy soil, gravel soil and thin soil layers or cracks on sunny slopes. I like acidic and slightly acidic soils, and the mountains with PH value of 4.5-6.5 grow best. Pinus massoniana, with its fast growth, long life, strong adaptability, tall and straight tree potential and majestic vigor, is not only the main pioneer tree species for afforestation in barren hills, but also an excellent tree species for creating scenic forests and convalescent forests. 3. Pinus tabulaeformis, also known as Pinus tabulaeformis and Pinus thunbergii, has the widest adaptability and can grow from south to north in Shaanxi Province. It is the best pine variety to adapt to continental climate. Cold-resistant, drought-resistant, low temperature of-25℃, can grow in the northern part of northern Shaanxi with precipitation of 300-400 mm. Pinus tabulaeformis is not strict with soil, and prefers slightly acidic and neutral soil. It will not grow well in alkaline soil above 7.5. Salt-tolerant alkaline soil, but it grows well in limestone mountain area, with deep soil layer, high water content of organic matter, abundant precipitation and good drainage. Therefore, Pinus tabulaeformis is one of the main coniferous tree species for windbreak, sand fixation and soil and water conservation in the loess hilly and gully region of northern Shaanxi. 4. Pinus sylvestris var. mongolica. Pinus sylvestris var. mongolica is the main fast-growing timber tree species in Northeast China, and it is also an excellent tree species for shelter forest and "greening all around". In 1960s, it was introduced into Yulin area of our province and grew well. Strong cold resistance, can withstand the low temperature of MINUS 40-50℃. At the same time, it is also a tree species with strong drought resistance, which has low requirements for soil moisture and well-developed roots and can make full use of soil moisture. The soil requirement is not high, and it is suitable for growing on aeolian sandy soil, gravelly coarse sandy soil, sandy soil, chernozem and albic soil. It is not conducive to the growth of alkaline soil with PH greater than 8 and places with salt content greater than 0. 1% or waterlogging. According to the requirements of suitable environmental conditions, Pinus sylvestris var. Quercus mongolica, as a tree species for sand prevention, sand fixation, gully control and "all around" greening, is only suitable for large-scale planting in northern Shaanxi. 5. Cedar, also known as Himalayan pine and Himalayan cedar, is tall and majestic. It is a precious timber tree species and a world-famous ornamental tree species. Cedar is a subtropical tree species, which is suitable for growing in a warm and humid climate. The annual rainfall is 600- 1000 mm, and the soil is deep, fertile and loose, acidic or slightly acidic. However, it can grow in cohesive loess, barren soil and exposed rock, and is not suitable for growing in low-lying stagnant water or places with too high groundwater level. Otherwise, it will grow poorly and even die. Poor anti-smoking ability, vulnerable to tobacco injury. Cedar is suitable for planting in Guanzhong and southern Shaanxi. Cedar is mainly supplied from other provinces because of its low seed bearing and low cutting survival rate, so it is used for landscaping and street tree planting every year. There are many natural types of cedar, which can be divided into three types according to tree type and branching: thick-leaved cedar, drooping cedar and upturned cedar. Pinaceae is the largest family in gymnosperms, with 10 genus and more than 230 species, including more than 90 species of Pinaceae, which is the largest genus in the whole gymnosperms. Pine is the most important forest tree species in the northern hemisphere. Except Sumatran pine distributed at 2 degrees south latitude, all other species naturally grow on the Yuan Ye, a mountain and river from the equator to 72 degrees north latitude. Especially in temperate regions, pine trees are not only varied, but also often form vast forests, so pine trees are known as "the mother of forests in the northern hemisphere". Pine trees are very adaptable to the land environment. They can tolerate the low temperature of -60℃ or the high temperature of 50℃, can grow in bare mineral soil, sandy soil, volcanic ash, calcareous soil, limestone soil and various soils from calcareous soil to red soil, and are drought-tolerant, barren and sunny, so they are famous pioneer trees. The most obvious feature of pine trees is that their leaves are needle-shaped, usually in bundles of 2, 3 or 5 needles. For example, the leaves of Pinus tabulaeformis, Pinus massoniana and Pinus taiwanensis are in bundles of 2 needles, the leaves of Pinus bungeana are in bundles of 3 needles, and the leaves of Pinus koraiensis, Pinus armandii and Pinus pentaphylla are in bundles of 5 needles. Pine is a monoecious plant, and its spore leaves are arranged like cones, forming female cones and male cones. Single or 2 14 female cones are attached to the top of new branches, and most male cones gather in the lower part of new branches. Pine cones usually bloom in spring and summer, but after the pollen reaches the female cones, it will not germinate until the early summer of the following year, so that the female flowers will fertilize and develop into cones (commonly known as pinecones or cones, not fruits). The cones mature after autumn, and the seed scales open, and each seed scale has two seeds. Pinus species are mostly tall and straight trees with good materials and many columns. Korean pine, the "king of wood" in the northeast of China, tall Pinus ponderosa (up to 75 meters) widely distributed in the west of North America, the fastest growing pine radial pine originated in the coastal area of California, slash pine originated in the southeast of the United States, Caribbean pine originated in the Caribbean of America, and Pinus densiflora widely distributed in the west and north of Eurasia. , are famous timber trees. The ornamental value of pine trees is obvious to all. In China, beautiful images of pine trees can be seen from the royal classical gardens to the homes of modern residents, such as Pinus tabulaeformis and Pinus bungeana in Beihai and Summer Palace, and Pinus pentaphylla widely used in stump bonsai. Some famous mountain resorts are famous for their majestic mountains and pine trees. Huangshan pine in Huangshan, Huashan pine in Huashan and Meiren pine in Changbai Mountain ... all amaze tourists. China is one of the countries with the richest gymnosperms in the world. From the perspective of Pinaceae, it can be fully explained that China is a veritable "hometown of gymnosperms". In China's vast mountainous Yuan Ye, there are not only lush pine, larch, spruce and fir forests, but also many extremely precious and rare Pinaceae trees hidden in some deep mountains and forests. Among the first batch of rare and endangered plants under special state protection, there are 39 species of Pinaceae, accounting for110 of the total (389 species). Among them, Cryptomeria fortunei is listed as the first-class key protected plants, Abies baishanzu and Pinus yunnanensis 17 species are listed as the second-class key protected plants, and Taxodium mexicana and Pinus sylvestris var. mongolica/0 species are listed as the third-class key protected plants.