Habits of ornamental trees

Section 1 Biological characteristics of various organs of ornamental trees

First, the concepts of growth and development.

Growth-Plants undergo cell division, differentiation and expansion, resulting in irreversible increase in volume and weight (quantitative change).

Development-structural and functional changes (qualitative changes) based on the differentiation of cells, tissues and organs.

The relationship between the two: growth is the foundation of development, growth is eternal, development and growth are inseparable, and both are irreversible. Nutritional growth and reproductive development.

Life cycle-the whole process from embryo formation to seed growth, flowering, fruiting and death.

Annual cycle (phenology)-the life cycle experienced in a year.

Second, the correlation between the growth and development of ornamental trees

1, life cycle of trees

(1) Seed stage (embryo stage)-seed dormancy (physiological dormancy, short-term dormancy) in which fertilized eggs form zygote seeds.

(2) The emergence of juvenile stage-seed germination-flower primordium) varies with plant species. Lagerstroemia indica and rose for one year; Peach, plum and apricot for 5 years; Ginkgo biloba for 20-30 years. Genetic instability, easy to be influenced by external environment, high plasticity, introduction, cultivation, domestication and directional culture.

(3) Adolescence

At the initial flowering stage, the characters of flowers and fruits gradually stabilize, the plants gradually grow and the vitality is vigorous; Plants in this period did not fully display the standard characteristics of this species or variety. It blossoms and bears fruit every year, and the number is very small.

(4) maturity (adulthood)

A, the plant has matured in all aspects, the characters of flowers and fruits are stable, and the number of flowers and fruits is large.

Reach the peak of production.

B, viewing peak, the highest economic benefits, strong resistance. Genes are conservative and not easily shaken.

C, the best time to collect seeds and flowers.

D, strengthen management, prevent premature aging, control the number of flowers and fruits, and prolong adulthood.

(5) Aging period (old age) A. Plant growth is declining year by year, with less flowering and fruiting, poor quality, easy occurrence of diseases and insect pests, and finally death. B, some of them are very ornamental.

2. Regularity of life cycle changes of trees

(1) Centrifugal growth and centrifugal alopecia

1. Centrifugal growth-growth with rhizome as the center, roots facing the ground, and buds on the ground facing away from the ground, expanding its space from the root neck to both ends.

2. Centrifugal exposure-the root system is self-thinning, and the root cap is naturally pruned by centrifugation.

(2) Centripetal renewal and death

Due to centrifugal growth and centrifugal baldness, the center of gravity of the branch tip moves outward and droops, the growing point is farther and farther away from the center, the transportation distance is long and the growth potential is slow. The extended branches of the central trunk are branched or curved. It is called truncation or capping. Long-lived budding tree species grow on the bending height of main branch-long branch-crown renewal-tree. From the outside to the inside, slowly retract, and the dominant position moves down. This kind of regeneration and withering is generally caused by (tree crown)

From the outside to the inside (bore), from the top (top) to the bottom (part) until the root neck, so it is called centripetal renewal and centripetal death. The speed and centripetal regeneration of centrifugal baldness are related to tree species, environmental conditions and cultivation techniques.

(3) Regeneration characteristics of different types of trees

A, where there are no latent buds, there are only centrifugal growth and centrifugal nudity, and there is no centripetal renewal, such as pine.

B, in the tree species with only the terminal bud and no lateral bud, only the terminal bud grows centrifugally without lateral branches. There is no centripetal renewal, such as palm.

C, bamboo root tiller renewal, bamboo whip bud tiller renewal.

D, shrubs-centrifugal growth time is short, some shrubs can be regenerated centripetally, and most of them are regenerated by stems and roots. Such as: boxwood, pittosporum, green bud tree species.

E. Lianas, such as wisteria, have fast centrifugal growth at the top, and the main vine is prone to baldness.

The regeneration method is beneficial to the management of ancient and famous trees, considering hidden buds and proper pruning.

3. Life cycle of seedlings

Two different stages of development:

Larval stage: growth-oriented, with obvious morphological and anatomical characteristics.

Characteristics of adult (mature) stage:

(1) When the juvenile period is not over, it can't be accepted as a flower, that is, it can't blossom by any artificial measures, but this stage can be shortened, such as early flowering and fruiting by grafting.

(2) Flowering is the most obvious feature of trees entering sexual maturity, but the end of juvenile stage is not necessarily consistent with the first flowering.

(3) The growth stage is the coexistence of reproductive growth and vegetative growth.

(4) Growth is eternal, and development is accompanied by growth.

(5) Distinguish two stages morphologically.

4. Life cycle of asexual trees

(1) has passed the juvenile stage, and there is no process of sexual maturity. If there are induction conditions (girdling, fertilization, pruning), flowers can be formed at any time, that is, only mature period and aging period.

(2) The germination age of rhizome is young, but the age outside the crown is old.

(3) Cuttings and scions should generally be extracted from the periphery and mature.

(4) The vitality is weaker than that of seedlings.

Third, the annual cycle of ornamental trees.

1, annual cycle and phenology of trees

Annual growth cycle-the regular changes of the morphology and physiological functions of trees with the change of environmental cycle in a year.

Phenology-a biological activity phenomenon in which plants grow and develop according to certain laws with the change of seasons in a year's growth cycle. Focusing on the change of appearance is an intuitive expression of tree rings and an important basis for tree ring division. Periodicity and timeliness are restricted by the inherent genetic factors of plants, and the arrival and process of each phenological period are influenced by environmental factors.

Phenological period-a specific period in a year when the growth and development stages of plants begin and end with climate change.

2. Annual cycle of deciduous trees

(1) growth period: budding is the sign of starting to grow; Vegetative growth and reproductive growth;

Roots grow before germination.

(2) Growth goes into dormancy.

A, natural defoliation is a sign of dormancy (defoliation);

B, the accumulation of nutrients in tissues and the maturity of tissues;

C, before and after defoliation, what are the changes that are beneficial to the cold resistance and overwintering of trees? Before defoliation: photosynthesis and respiration are weakened; Chlorophyll is decomposed, and some N and K are transferred to the branches. After defoliation: with the decrease of temperature, the fat and tannin in tree cells increase; Cell fluid concentration and protoplasm viscosity increased; The primary membrane forms a lipid layer, and its permeability decreases.

D, autumn shows that it is not ready for wintering;

E, temperate trees that enter dormancy in different days begin from late summer to Sunday to early autumn; Some buds appear long before the leaves fall; Generally, branchlets, thin short branches and early buds enter early; The lower buds of long branches stop early, the terminal buds can continue to grow, and the upper lateral buds may not germinate because of the apical advantage; The cortex and xylem fall asleep early, and the cambium is the latest, so the branches and stems on the ground that are easy to be frozen fall asleep late, and the root diameter is the latest, which is easy to be frozen; Young trees fall asleep later than adult trees; Suffering from drought, waterlogging, pests and diseases will cause early defoliation and even re-growth.

(3) The dormant period becomes the growth period.

When t is greater than 3℃ and the accumulated temperature is constant, the bud will expand. Physiological activity is earlier; With proper temperature and humidity, sap begins to flow and bleed, walnuts and grapes; At this time, the cold resistance is reduced, and T reduces the freezing injury until it is dead.

(4) Natural dormancy (deep dormancy or mature dormancy) during relative dormancy: determined by physiological process or genetic characteristics. A certain low temperature condition and a period of time (the north tree moves south). Forced dormancy: the outside world lacks the conditions needed for growth.

3. Phenology of evergreen trees

The climate is complex and the life span of leaves is uncertain. Broadleaf: leaf age of Cinnamomum camphora and Photinia fraseri1y. Magnolia grandiflora is about1y. ; Needle: Cedar 2 y., Podocarpus is longer)

Fourth, the growth and development law of various organs.

(1) root

1, factors affecting root growth

Soil temperature: variable temperature layer/growth layer/constant temperature layer (30-90℃)

Soil water content: 60-80% of the maximum water capacity.

C. Soil permeability: oxygen and carbon dioxide

D, land nutrition (nutrients): generally not a limiting factor, not very strict; Root fertilizer; Primitive soil; Artificial soil and artificial matrix: peat, vermiculite (good water retention and air permeability), perlite and sawn timber.

E. Organic nutrients in the tree: (The accumulation of organic nutrients and endogenous hormones in the tree is the internal cause of root growth) When the land conditions are good, the total root system depends on the amount of organic nutrients in the tree.

F others: land type, land thickness, parent rock differentiation, groundwater level, etc.

(2) Annual growth dynamics of root system

A, three peaks: when the root system begins to grow in spring (small), when the aboveground part growth tends to stop in summer (large),

Before falling leaves in autumn (small)

B, the growth dynamics of the root system in the annual cycle, depends on: tree species, the combination of roots and spikes, the growth results of the aboveground parts of the year, the temperature, moisture, ventilation and inorganic nutrition of the land.

C, the dynamic change of day and night growth-root growth and the number of hairy roots are more at night than during the day.

(3) The life cycle of roots (lateral or dichotomous) is locally self-thinning and renewing. Cork baldness. Seasonal intermittent death of large roots and horizontal basement uplift.

(4) metamorphosis of roots

A. Plate roots: Tropical trees form plate roots between stems and root necks. For example, banyan trees and wild lychees.

B. Respiratory roots: roots that protrude from the ground or float on the water surface to breathe, such as knee-shaped respiratory roots of Pinus tabulaeformis and Taxodium distichum.

C, attached roots: adventitious roots used to climb other things. Such as: Roche, Ling Xiao.

D, aerial rooting: The vertical roots of banyan trees downward from the big branches are the most.

E. parasitic roots: roots planted in parasitic tissues to absorb water and nutrients. Such as mistletoe and mistletoe.

(5) Several conditions related to root system

A neck: true root neck-the root neck of seedlings, which develops from hypocotyl.

Pseudo-root neck-asexual propagation seedlings have no true root neck, which is equivalent to the true root neck position of seedlings.

Rootstock is an active part of tree organs, which enters dormancy later than the aboveground part and leaves dormancy earlier, so it should not be buried too deep in the soil or exposed too high above the ground.

B. Rooting: Adventitious buds formed on horizontal roots take root and form new plants.

Influencing factors of tillering: easy to occur-the humidity and air permeability of the land, when the humidity of the land is suitable and the air permeability is good; It is closely related to the growth of aboveground parts (when the aboveground parts are damaged; The lush growth period with less aboveground parts)

According to the relationship with tree growth, B mycorrhiza can be divided into ectomycorrhiza and endomycorrhiza.

Ectomycorrhiza: Most of them occur on woody plants. The end of the small root is covered with a layer of white fluffy mycelium called cap, and its mycelium may sometimes extend into the root tissue, but it is usually in the intercellular space, not into the cells.

D. Endophytic mycorrhiza: There are both herbaceous plants and woody plants. Mycelia invades a certain number of cells in the root cortex, showing a twisted state, making the root hypertrophy or tumor-like.

(2) The growth of buds

(1) Concept: The important organs formed by trees to adapt to adverse environment and prolong life activities are the precursors of branches, leaves and flowers.

(2) Function: the basis for the growth, flowering and fruiting, regeneration and rejuvenation of trees, maintaining the characteristics of mother plants and vegetative reproduction.

(3) Several related concepts:

A fixed bud: the terminal bud, axillary bud or latent bud (the most basal bud of a tree or some secondary buds on the upper part) appears in a certain position, which is called fixed bud. B. Adventitious buds: They often appear on root cutting, re-cutting or old branches.

C. Bud order: the order in which fixed buds are arranged on the tree according to certain rules. (leaf order)

D. Heterogeneity of buds: Due to the different internal (internal nutritional status) and external (environmental) conditions during the development of buds formed in the same year, buds in different parts of the same branch have different properties such as size and fullness.

E. Early maturity and late maturity of buds (germination in the next spring): the former does not need low temperature, as long as conditions are available in that year, such as peaches.

F. Germination ability and branching ability: Germination ability refers to the germination ability (germination rate) of buds on the parent tree. Branching ability refers to the ability of buds on the mother tree to grow long branches.

G. Latency of buds (life span of latent buds): When the branches are stimulated (when the upper or nearby parts are damaged and some branches fall off) or when the branches outside the crown are weak, the ability of latent buds to produce new shoots is related to whether the aboveground parts of trees can be updated and strengthened.

abstract

Buds are the basis of branches, stems and reproductive organs. Only robust buds can have robust growth and development. In order to cultivate robust buds, the most fundamental way is to cultivate robust tree potential. In order to promote the development of local buds, pruning, coring or carving can be used.

(3), the growth of trunk and branches

(1) branch type

According to the growth habits of branches and stems, they can be divided into vertical growth (tight-holding type, spreading type, drooping type, longyou type, etc. ), climbing growth (woody vines) and creeping growth (ground cover plants: Sabina vulgaris, Forsythia suspensa, Yingchun and Huangxin). Quality: vegetative branches (flower buds), flowering and fruiting branches (flower buds and leaf buds).

(2) Branching methods Branching of various trees has certain regularity, and under sufficient space conditions, they grow into different crown shapes (few species are unbranched).

A, racemose branching (uniaxial branching) formula: gymnosperms are the most.

B, axial branches: such as peaches, apricots, plums and pears. Angiosperms are the most common.

C. Pseudodichotomy (another way of axial branching): such as clove and paulownia.

(3) Top dominance: Aralia elata and pine trees have strong top dominance, and the central trunk is durable.

(4) drying and layering

A dryness: the strength of the central trunk of a tree and its duration. For example, cedar, Metasequoia glyptostroboides and Magnolia grandiflora have strong dryness; The trunks of plum trees, peach trees and shrubs are not strong.

B stratification: the main branches are distributed on the central trunk or the secondary branches are distributed on the main branches to form an obvious hierarchical structure; Recurrence in young trees over the years; Tree species with strong apical dominance and weak branching ability have obvious stratification; Tree species with obvious stratification: Pinus thunbergii, Pinus massoniana, Ginkgo biloba, Magnolia grandiflora and Loquat, almost one layer a year, which can be used as one of the basis for determining the age of trees; The dryness and layering of different tree species are different: the dryness and layering of trees will change under different cultivation conditions (group planting, single planting and artificial pruning).

The interaction between apical dominance and bud heterogeneity. (the strength of the top advantage and the length of the maintenance period are reflected in whether the stratification is obvious. It has a layered crown, which is conducive to ventilation and light transmission. )

(5) Growth characteristics of branches: they become longer and thicker. Indicators for measuring the growth intensity of trees:

Annual growth (thickness and length achieved in one year)

Growth potential (growth rate of elongation and thickening in a certain period)

A. Prolonging the initial growth period-vigorous growth period-slow growth period and stopping growth period proceed in a slow-fast-slow rhythm, and the growth curve is S-shaped.

B. the result of division, differentiation and expansion of thickening growth cambium.

The coarse growth peak is slightly later than the long growth peak, and the stopping time is later; The lower the main branch level, the later the thickening peak and the greater the thickening amount; Each branch is thickened once (annual ring); Stop from top to bottom, with the root neck at the latest; In order to promote thickening, branches and leaves must be preserved.

(6) Factors affecting the growth of new shoots

1. Varieties and rootstocks;

B, storing nutrients (organic nutrients);

C, endogenous hormones;

D, the position and conditions of the mother branch (late advantage);

E. environment and culture conditions.

(7) The advantages of the main branches of the crown forming the central trunk and extending branches gradually weaken (the terminal buds become flowers, wither or the branches bend), and the crown becomes round, dull and then widened.

(4) Leaves

A, leaf color (at the beginning of flowering and leaf spreading, after flowering)

B, the cause of falling leaves

C, leaf curtain-leaves are concentrated in the crown, reflecting the total leaf area of the crown. (evergreen, deciduous)

D. Three physiological functions of leaves: respiration, transpiration and photosynthesis.

(5) Flowers

(1) Factors and theories affecting flower bud differentiation

A, the growing point cells in the bud must be in a physiologically active state;

B, the relationship between the inheritance of seedling trees and the first flowering; (Genetic genes are the basis of flower bud differentiation)

Relationship between vegetative growth of branches and flower bud differentiation

D, the supply of nutrients is the material basis of flower bud formation; (C/N ratio theory, cell fluid concentration theory, nitrogen metabolism direction theory, flower hormone theory)

E, the regulation of endogenous hormones is the premise of flower bud formation.

F, the relationship between leaves, flowers, fruits and flower bud differentiation;

G, minerals, root growth and flower bud differentiation are obviously positively correlated. When most elements are quite lacking, it will affect flowering.

H, the influence of light;

First, the influence of temperature;

J, water: too much water is not conducive to flower bud differentiation, and moderate drought in summer is beneficial to the formation of tree flower buds;

Relationship between cultivation techniques and flower bud differentiation.

Synthesis: Three Conditions for Flower Bud Formation

A, the growing point is in a state of division but not excessive prosperity;

B, depending on the effective assimilation products, at a certain place and for a certain time.

Interaction, and the balance of endogenous hormones (internal cause);

C, the conditions are right.

(2) the process of flower bud differentiation

Physiological differentiation: metabolic pattern changes; Morphological differentiation 1-6 weeks; It is a critical period of differentiation.

Morphological differentiation: in the early stage of differentiation-forming calyx primordium (the direction of differentiation will not be reversed)-forming petal primordium-forming stamen primordium-forming pistil primordium.

Sexual cell formation: there was no low temperature and high temperature to form early flower buds in that year; Late-maturing flower buds must undergo low temperature and form when the temperature is higher in the next year.

(3) flower bud differentiation type

Differentiation type of the current year: early-maturing flower buds formed and opened in the current year, born on annual branches. Hibiscus, Lagerstroemia indica

Differentiation types in winter and spring: longan and litchi.

Summer-autumn differentiation type: late-maturing flower buds, open in summer and autumn in the following year, born on branches over two years old. Plum blossom, Magnolia grandiflora, Spring Festival,

More than one year differentiation type: more than one year differentiation, more than one year opening. Rose, jasmine, tamarisk

(4) Methods of controlling flower bud differentiation

Investigate the types of flower bud differentiation-analyze the critical period of flower bud differentiation-analyze the nutritional and environmental conditions during this period-and take reasonable cultivation measures.

(6) Fruit

Ornamental trees for fruit viewing: exotic, abundant, large and colorful.

(1) concept:

Parthenogenesis-such as Hubei begonia (fruits and seeds can develop normally)

Parthenogenesis-such as seedless grapes and seedless persimmons (the sublayer is mature, but there are no seeds)

Fruit setting-the result of ovary development after pollination and fertilization is called fruit setting.

Physiological fruit drop-not the phenomenon of flower drop caused by machinery and external force.

(2) Problems

A. What is abortion? What causes miscarriage?

B. Early flowering and young fruit shedding: due to incomplete pollination and fertilization, there is too much water or zinc deficiency; Fruit drop in June: malnutrition (nitrogen application before flowering and phosphorus application after flowering) fruit drop before harvesting: the energy produced by embryo growth hormone is reduced, the characteristics of tree species, poor ventilation and light transmission, and environmental impact;

The direct cause of fruit drop: insufficient auxin or imbalance between organs can improve the fruit setting rate of weak trees by spraying urea before flowering, and applying nitrogen fertilizer at the end of the first year is also beneficial to improve the fruit setting rate. Boron has a good effect on pollen germination and fertilization, and spraying a certain concentration of borax before germination or flowering can improve the fruit setting rate.

C. Time of fruit ripening. This stage begins with fertilization and ovary enlargement until the fruit is fully mature.

D. Cultivation measures to improve the economic value and ornamental value of fruits.

E. Factors affecting the fruit-bearing of trees: climate and weather conditions, light, land, flowering habits (dioecious and dioecious trees prevent some tree species from self-pollination), and biological factors (natural enemies and anthracnose are one of the important reasons for early fruit drop and yield reduction of Camellia oleifera).

Fourthly, the correlation between the growth and development of ornamental trees.

(1) Correlation of organs

Terminal bud and lateral bud: remove terminal bud, expand crown, remove lateral bud, and protect top advantage.

Root tips and lateral roots (apical dominance)

Fruits and branches vegetative organs and reproductive organs (unity of opposites)

(2) Correlation between roots and aerial parts

When the root system is solid, the branches are in a state of dynamic balance (at middle and young age, the horizontal distribution of the root system exceeds the crown width, and the root depth is less than the tree height).

2. Physiological characteristics and cultivation of trees

Nutritional changes in (1) annual cycle

A. nutritional metabolism types: n metabolism and c metabolism, two major sources of nutrition.

B. nutrient distribution centers and vigorous growth sites.

C. Consumption and accumulation

Excessive growth and consumption of branches and leaves are not conducive to flower bud differentiation, fruit development and deterioration of light conditions.

In autumn, the temperature drop is a good opportunity to improve the storage nutrition level of trees (low consumption, still vigorous photosynthesis, high soil temperature, topdressing outside the roots, inorganic promoting organic).

(2) Nutritional characteristics of life cycle

Young trees: accumulation (small old trees, site conditions)

Adult tree: the age when the storage level is low.

Strong old trees: soil strength decline+tree conduction tissue obstacle

(3) culture

Good management of trees is the premise, so that the standing nutrient level will be improved year by year, inorganic promotes organic, and organic stresses inorganic.

Pre-stage: metabolism n.

Mid-term: expanding and stabilizing storage metabolism

Late stage: further improve storage metabolism.

Section 2 Ecological Habits of Ornamental Trees

I. Concept of environment

Environment: The ground and space where trees live is called environment.

The factors that constitute the living environment of trees are called environmental factors. Environmental factors usually include the following

Column 5 Category:

Climate factors: including light, temperature, humidity, air, etc.

Soil factors: including soil organic matter, inorganic matter, soil physical and chemical properties and soil microorganisms.

Topographic factors: including mountains, plains and slopes, slopes, etc.

Biological factors: including animals, plants and microorganisms.

Man-made factors: including people's utilization, development, protection and destruction of tree resources.

Ecological factors: Among the environmental factors, the factors that directly and indirectly affect the life of trees are called ecological factors.

Trees and environment are the unity of interaction. When studying the relationship between trees and environment, we should not only understand the characteristics of trees themselves, but also understand their environment and their relationship. When studying the relationship between trees and ecological factors, we must have the following basic concepts.

1. Comprehensive action

The ecological factors in the environment are closely related to each other and play a comprehensive role. The change of any ecological factor will cause the changes of other factors to varying degrees. For example, the change of light intensity can cause the change of temperature and humidity factors.

2. Leading factors

All ecological factors are necessary for tree life, but under certain conditions, 1-2 must play a leading role, which is the leading factor. In the process of tree growth and development, the dominant factors are not constant.

3. Irreplaceability and adjustability of ecological factors

No one ecological factor can be replaced by another. However, in some cases, when a certain factor is insufficient, it can be adjusted by increasing or strengthening other factors, and similar ecological effects can still be obtained.

4. Ecological factor stage

Ecological factors play different roles in different development stages of trees. For example, short sunshine time is the leading factor leading to the fall of deciduous trees in autumn.

5. All kinds of trees in the ecological amplitude have a certain adaptation range to the living conditions and the changing intensity of ecological factors, and beyond this limit, they will cause growth discomfort or death.

Second, the concept

Ecological characteristics: because trees grow under certain environmental conditions for a long time, they have formed requirements and adaptability to this environmental condition, which is called ecological characteristics. (Ecological characteristics)

Habitat: the microenvironment in which plants live.

Third, climate factors and trees.

1, temperature

(1) Three basic temperatures for the growth of trees: minimum temperature (4℃-6℃), optimum temperature (24℃-30℃) and maximum temperature (30℃-40℃, not exceeding 50℃).

(2) Accumulated temperature, effective accumulated temperature and active accumulated temperature of tree growth.

(3) the change of temperature and the growth of trees

(4) temperature and tree distribution

(5) Technical measures to prevent low temperature and high temperature hazards

I. Day and night temperature changes

Daily range (daily amplitude): the difference between the highest value and the lowest value in a day.

Temperature cycle: adaptability of plants to day and night temperature changes.

◆ Plants native to continental climate zones grow and develop best when the daily variation range is 10℃- 15℃.

Plants are born when the daily range of plants native to marine climate zone is 5℃- 10℃.

Growth is the best.

B, the sudden change of temperature

Frostbite: T & gt0℃

Freezing injury: T=0℃

Freezing injury: T 14h, such as Tang Changpu.

Short-day plants 7.2): such as Amorpha fruticosa, Hippophae rhamnoides, Tamarix chinensis, etc.

(4) Tree species with strong saline-alkali tolerance

VII. Other environmental factors

(1) topographic factors

Topographic factors include altitude, slope direction, slope position, slope, mountain and river trend and topographic relief.

Aspect: It affects the time and intensity of sunshine. On the north slope, the sunshine time is short, the temperature is low and the humidity is high. Generally, more shade-tolerant and moisture-tolerant trees grow. The south slope has long sunshine time, high temperature and low humidity, and many xerophytic trees grow. For example, Pinus tabulaeformis in the low mountainous areas of North China is mostly distributed on shady or semi-shady slopes, while only some drought-tolerant shrubs grow on sunny slopes.

Altitude: a pattern of vertical distribution

(B), biological factors

1. Trees grow together with other animals, plants and microorganisms and are closely related to each other. Different kinds of animals, plants and microorganisms have beneficial or harmful effects on the distribution, growth and reproduction of trees.

2. Different tree species often inhibit or promote each other because of their different requirements and adaptability to living conditions. Even in a simple forest composed of the same tree species, different individuals and their relationships with weeds and shrubs inhibit or promote each other. The determination of tree species mixing type, afforestation density, tending and cutting, and seedling raising measures in production are all based on the interaction theory between tree species.

Verb (abbreviation of verb) human factors

People are restoring forests and destroying them. The most terrible thing is to destroy yourself.

Section 3 Urban Environment and Ornamental Trees

(a) Overview of the urban environment

1. Urban climate: Microclimate conditions vary greatly and are greatly influenced by human activities.

(1) Urban underlying surface: the cement, asphalt and site conditions are poor, so it is difficult for groundwater to enter, and the surface water is drained.

(2) Urban air industry and automobile pollution

(3) Urban population precipitation is discharged through pipelines, the air is dry, the surface temperature is high, the air is a high heat island effect, and the temperature difference between day and night is small.

2. The nature of urban land has basically changed, and there is some pollution.

3, building positioning and combination

The combination of buildings in different directions forms light, land and air flow downward, and there is a certain space and microclimate. Therefore, in the greening of residential areas, appropriate tree species should be selected according to the temperature, humidity and lighting conditions of the formed space.

(2) Environmental characteristics of urban planting areas

In addition to nature reserves, according to the general situation of urban ecological environment and greening, the tree planting environment is divided into four categories: old city, new city, near-effect area and near-effect scenic spot.

1. Features of the old city: the building area is large and narrow, there are few academic schools, rainwater is not easy to penetrate, and it is easy to accumulate water. For example, Nanjing has buildings on both sides. In summer, the radiation is strong, the road absorbs more heat, and the air convection performance is poor. Even at night, heat is not easy to dissipate, air pollution, land hardening, poor ventilation and drainage performance.

2. Features of the new urban area: Most of them occupy the original urban farmland and grassland, and the topsoil has great influence. The middle and lower layers are generally primitive farmland soil and construction waste, and the soil layer is generally deep, which is suitable for tree growth. For example, Yangzi Petrochemical has high planting density and good initial effect. After a few years, it will be crowded. It is necessary to transplant scattered seedlings and pay attention to pruning.

3. Near-effect area (near-effect green space) Forest parks or highways and railways are afforested, with less buildings, more vegetation and low temperature. Natural soil, that is, cultivated land soil, is deep and fertile. Plain cities should also consider the role of groundwater, and air and water pollution are serious. The area is large and it is impossible to change soil. Choose native tree species and plant them locally. For example, there are more than 300 meters of scenic belts on both sides of Shanghai-Nanjing Expressway, and Metasequoia glyptostroboides and poplar trees are planted on both sides of Zhu Lin Avenue Ring Road, which is extensive in management.

4. Attractions

(1) Due to the differences of mountains, rivers, lakes and islands, the ecology of mountain scenic spots has laws to follow.

(2) According to the influence of groundwater level, harmful salt and seasonal changes, whether the water is dead water or living water, the ecology of water scenic spots is different.

(3) Natural scenic spots: natural land with lush plants, such as Sun Yat-sen Mausoleum.