dune-fixing afforestation

1 planning and design of sand-fixing afforestation

1. 1 forest belt planning and design

The design content includes the strike, width, spacing, structure and mixed type of forest belt.

1. 1. 1 forest belt trend

1.1.1.1The basic forest belt for preventing wind, blocking sand and fixing sand should be located at the junction of the front edge of the sand dune and the edge of quicksand outside the farmland forest network and the farmland oasis, and the direction of the forest belt should be perpendicular to the sand dune flow direction.

1. 1. 1.2 farmland shelterbelt network (including grazing shelterbelt network), rectangular grid should be used in the main wind damage area, and square grid can be used in the main wind damage area. The strike of the main forest belt should be perpendicular to the main wind direction, or the deviation angle should not be greater than 45. The secondary forest belt should be perpendicular to the main forest belt; For example, due to the limitation of topography, the main and secondary forest belts can have a certain deviation angle. Low-lying areas can "follow the water"; Flat areas can "follow the road"; In the wind erosion hilly area, the main forest belt can be laid along the contour line, and the auxiliary forest belt can be connected with the greening of the upper and lower slopes and the greening of the river bank to form a forest network.

1. 1. 1.3 The windbreak belt along the coastline should be set perpendicular to the main wind damage direction, or it can be set according to the natural distribution trend of beaches along the coastline.

1. 1.2 width of forest belt

1. 1.2. 1 The basic trunk forest belt for windbreak and sand fixation can adopt single belt or double belt respectively. Multi-belts can be used in areas with serious wind and sand hazards. The general bandwidth is 50 ~ 100 m, and the bandwidth in the frontier area of large-scale quicksand invasion can reach 200 ~ 1000 m, and the allowable bandwidth in the area bordering oasis and sand dunes is 30 ~ 50 m.

1. 1.2.2 farmland shelterbelt network, with the main bandwidth of 8 ~ 12m (3 ~ 4 rows of trees) and the sub-bandwidth of 4 ~ 6m (1 ~ 2 rows of trees). In areas with less land and more people, the main bandwidth can be 5 ~ 6m, and the secondary bandwidth can be 3 ~ 4m.

1. 1.2.3 The coastal windbreak belt should be determined according to the sea breeze intensity and beach conditions, generally 20 ~ 100~200m wide, and the maximum can reach 100~200m. ..

1. 1.3 forest belt spacing

1. 1.3. 1 windbreak and sand fixation trunk forest belt, single belt, double belt or multi-belt can be used, and the spacing should be 50 ~100 m.

1. 1.3.2 farmland shelterbelt network, and the spacing between shelterbelts shall be calculated as 15 ~ 20 times of the average height of main tree species in their prime. At the intersection of the main forest belt and the auxiliary forest belt, only a gap with a width of 20m is left on one side for convenient passage. The grid area of forest network is generally 15 ~ 20hm2, and the maximum is not more than 30hm2, and the severe sandstorm area is controlled below 15~20hm2.

1. 1.3.3 coastal shelterbelt can be set with a main shelterbelt at the offshore front, or the second and third shelterbelts can be set at intervals of 100 ~ 300m behind the first coastal shelterbelt.

1. 1.4 forest belt structure (Figure 6- 1)

1. 1.4. 1 porous. The spacing of forest belts is 10 ~ 15 times the height of trees, which is suitable for farmland shelterbelts and coastal shelterbelts in areas with severe wind erosion.

1. 1.4.2 compact. The spacing of forest belts is 8 ~ 10 times of the height of trees, which is suitable for afforestation in tuyere, wind and sand fixation, and forest belts on both sides of railway and highway trunk lines.

1. 1.4.3 ventilation type. The spacing of forest belts is 1.5 ~ 20 times the tree height, which is suitable for farmland shelterbelts and coastal windbreaks in moderate and mild wind erosion areas. See figure 6- 1.

Fig. 6- 1 Structure of Forest Belt

1. 1.5 mixed forest belt

1. 1.5. 1 mixed forest belt: trees and shrubs are combined in proportion to form a forest belt with a tight structure or a sparse structure, which is suitable for areas with severe drought and wind damage.

1. 1.5.2 Arbor mixed forest belt: it consists of two layers of trees, the upper layer is a light-loving tree species, and the lower layer is a shade-tolerant associated tree species. Two light-loving tree species can also be arranged on both sides of the forest belt to form a ventilated forest belt, which is suitable for agricultural land or coastal sand belt.

1. 1.5.3 Shrub mixed forest belt: the forest belt is composed of shrubs as a biological sand barrier.

1. 1.5.4 comprehensive mixed forest belt: a comprehensive forest belt with mixed trees and shrubs, light-loving, shade-tolerant and associated trees. Suitable for windbreak and sand fixation, trunk forest belt and tuyere afforestation.

1.2 tuyere greening design

Set a belt-shaped sand barrier perpendicular to the main wind direction, with a width of 1 ~ 2m and a spacing of 20 ~ 30m. A compact mixed forest of trees and shrubs can be built in the sand barrier, with a spacing of 0.5m and a row spacing of 1.0m, which is staggered; Plant-row mixed or block mixed, the ratio of arbor to irrigation is 1∶ 1, shrubs are planted on the windward side, and trees are planted on the back side.

1.3 map greening design

1.3. 1 Sandy land with low or stable wind erosion and semi-mobile sand dunes can be directly planted in pieces to completely fix sand.

1.3.2 For mobile sand dunes, sand barriers should be set up first to slow down the wind speed and fix the quicksand, and then afforestation should be done in sections. Planting tree forest belts in the lowlands between leeward slopes and hills to prevent quicksand from moving forward; Plant shrubs at the foot of windward slope to reduce sand dunes.

1.3.3 The plant spacing of flaky afforestation should be determined according to tree species and site conditions. Plants are usually arranged in a needle shape.

2. Selection of afforestation tree species for sand fixation

2. 1 tree species selection principle

2. 1. 1 Select excellent tree species and native tree species suitable for local growth.

2. 1.2 Tree species with flood tolerance, salt tolerance and wind resistance should be selected for afforestation along the coast and lake.

2. 1.3 shrubs should be selected with good windbreak and sand fixation effects, strong drought resistance, fear of sand burial, flourishing foliage, strong tillering ability, high strip (or firewood) yield and good quality.

2.2 Main Afforestation Tree Species in Northern Sandstorm Area

2.2. 1 Trees: poplar, willow, elm, Mongolian Scotch pine, etc.

2.2.2 Shrubs: Salix psammophila, Misha, Hippophae rhamnoides, Artemisia, Hedyotis diffusa, Caragana korshinskii, Amorpha fruticosa, Calligonum mongolicum, Salix psammophila, Lycium barbarum, etc.

2.3 Main Afforestation Tree Species in Ancient River Sandy Land in Yellow River Flooding Area

2.3. 1 Trees: poplar, willow, elm, Ailanthus altissima, Robinia pseudoacacia, Platycladus orientalis, Paulownia, etc.

2.3.2 Shrubs: Amorpha fruticosa, Lespedeza, Salix psammophila, Vitex negundo, etc.

2.4 Main Afforestation Tree Species in Southeast Coastal Sandy Areas of China

2.4. 1 Trees: Casuarina equisetifolia, Acacia, Metasequoia glyptostroboides, Cryptomeria fortunei, Torch, Platycladus orientalis, Poplar, Melia azedarach, Quercus acutissima, Sapium sebiferum, etc.

2.4.2 Shrubs: willow, Rosa roxburghii, Nitraria tangutorum, hibiscus, oleander, etc.

3 Sand fixation and afforestation construction

3. 1 afforestation and soil preparation

3. 1. 1 soil preparation time

3. 1. 1. 1 Planting arbor forests, in areas with moderate and mild wind erosion in the north, grass beaches, hard hills, fixed sand dunes, etc. Soil preparation should be carried out in the late autumn and early winter of the previous year and afforestation should be carried out in the spring of the following year. It is not suitable for afforestation in mobile sand dunes and semi-mobile sand dunes to avoid wind erosion. Areas with severe wind erosion can be planted in spring. The southern region can prepare soil before afforestation.

3. 1. 1.2 When planting pure shrubs, afforestation can be carried out with land preparation; It takes the same time to build a mixed forest of arbor and shrub as to prepare soil for arbor forest.

3. 1.2 general soil preparation method

3. 1.2. 1 Afforestation can be carried out in strips on a large area of desert land with complete and gentle slope, and the bandwidth is1.0 ~1.5m. After raking the flat surface, dig holes and plant trees on it, and arrange them in zigzag according to the designed plant spacing. Mechanical ditching can be used as a belt when conditions permit.

3. 1.2.2 For afforestation in desert land with broken terrain and steep slope, fish scale pits can be used for soil preparation, with pit diameter of 1.0 ~ 1.5m, pit depth of 0.6~0.8m and pit spacing of 3 ~ 5m, which are arranged in zigzag.

3. 1.2.3 hole-shaped soil preparation can be used for shrub cultivation. According to the designed row spacing, dig holes at fixed points, with a hole diameter of not less than 0.6m and a pit depth of 0.3~0.6m, depending on the root system of seedlings.

3. 1.3 preparation method of special soil

3. 1.3. 1 silt turning and sand pressing for soil preparation. The sandy land of the ancient river channel in the Yellow River Flooding Area has a shallow sand layer (0.5~0.6m) and silt underneath. Before afforestation, the lower silt can be turned up manually or mechanically and pressed on the sandy soil with a thickness of 0.3~0.4m, and then afforestation can be carried out on the silt.

3. 1.3.2 exotic soil preparation: in the southeast coastal mudflats and places with high ground temperature in summer, the pits should be dug according to the plant spacing first, and then trees should be planted with low-temperature exotic soil.

3.2 Afforestation

3.2. 1 Select seedlings.

3.2. 1. 1 Bare-root seedlings shall comply with the provisions of GB6000; Container seedlings should conform to LY1000-91.

3.2. 1.2 broadleaf tree species should be 1 ~ 2-year-old seedlings, with plant height above 1.5m, taproot length of 30cm, ground diameter above 2.0cm and taproot length of 25 ~ 30cm. Conifer species should be 2 ~ 3-year-old container seedlings or plant seedlings with complete terminal buds. Shrub seedlings should be 1 ~ 2 years old.

3.2. 1.3 The quality of seedlings should be well controlled. Roots and seedlings should not be damaged during seedling raising, and relatively complete capillary roots should be maintained; After the conifer seedlings are raised, they should be planted with the seeds. When transporting seedlings from other places, the seedlings should be picked in days and transported to the afforestation site on the same day, no more than 2 days at most. For seedlings that can't be planted in time, it is necessary to make a good fall, and set up light and wind protection measures to prevent exposure or heat accumulation.

3.2.2 Planting techniques

3.2.2. 1 Broad-leaved trees are dug and planted in Yichun in autumn.

Shrub seedlings or coniferous arbor seedlings in 3.2.2.2 have small roots and are usually planted with narrow slits in spring or rainy season.

When container seedlings or coniferous seedlings are used for afforestation in 3.2.2.3, soil preparation should be done in advance, afforestation should be done when the water content is good in spring, or planting should be done before and after rain in beginning of autumn. Broad-leaved tree seedlings in arid and semi-arid areas can be cut down for afforestation.

The planting depth of 3.2.2.4 Fengkou afforestation should exceed the maximum wind erosion depth in that year, reaching the wet sand layer of sandy land, and sand ridges should be planted around the planting holes to increase ground roughness and reduce wind erosion.

When building coastal windbreaks in 3.2.2.5, exotic soil should be used and planted deeply in time.

3.3 afforestation by inserting (pressing) strips

3.3. 1 bar selection

Select annual new strong strips, insert (press) them, and keep the spare branches moist. Generally, the strip length is 0.4~0.7m, and the ground diameter is 1 ~ 2cm. The tall pole is 2.5 ~ 4m long and 3 ~ 6cm thick.

cut

The cuttings should be exposed to the ground for 3 ~ 4 cm, 1 ~ 2 bud eyes to prevent the bud eyes from being planted upside down; The afforestation of tall stalks should be buried 0.8 ~ 1.2m underground and1.5 ~ 3m above ground; When planting horizontal stems, the covering thickness should be 10cm.

3.4 aerial seeding afforestation

3.4. 1 pre-broadcast investigation and planning

3.4. 1.65438+

3.4. 1.2 according to the possible benefits of aerial seeding afforestation, determine the specific aerial seeding range, measure and plan the aerial seeding area near the main wind direction, bury the navigation mark piles, and draw the aerial seeding operation map (scale11000) and the location map of the seeding area (scale 1/20)

3.4.2 Design of broadcast width and flying height

3.4.2. 1 The length, sowing width and flying height of one-way or round-trip flight belt shall be determined according to sowing conditions. The designed sowing width of large seeds is 50 meters and the flying height is 50 ~ 70 meters; Small seeds, such as Artemisia sphaerocephala, have a designed sowing width of 40m and a flying height of 50-60m.

If the broadcast width in 3.4.2.2 is wide, the overlap rate should be increased by 20% ~ 30% on the basis of the above width.

During aerial seeding in 3.4.2.3, the crosswind speed should not exceed 5.4m/s and the crosswind angle should not exceed 40℃ (small seeds should not exceed 20℃). Wind speed of aerial seeding along and against the wind: the large seeds shall not exceed 6 ~ 8m/s, and the small seeds shall not exceed 6m/s. ..

3.4.3 Preparation before broadcasting

3.4.3. 1 Selection of sand-fixing plants by aerial seeding. In quicksand areas, plants with wind erosion resistance, sand burial resistance, rapid growth, strong natural reproduction and high economic value should be selected for aerial seeding, such as Artemisia, Taraxacum mongolicum and flower sticks. Sowing amount per hectare: Tanlang12 ~18kg, Huabao15 ~ 23kg, Artemisia sphaerocephala 7.5 ~15kg.

Large-scale seed treatment in 3.4.3.2. In order to solve the displacement problem of small seeds and easy-to-drift seeds, loess should be wrapped around the seeds to make large seed pills which are 2 ~ 3 times heavier than the seeds, so as to ensure the uniform distribution of seeds and improve the area rate of aerial seeding.

Prevention and control of seed diseases and insect pests in 3.4.3.3. Before sowing, the seeds should be soaked with liquid medicine which is harmless to people and animals to prevent and control the three pests of rats, rabbits and insects.

3.4.3.4 should set up obvious signs on the ground according to the planned scope and width of air broadcasting.

The sowing date of 3.4.3.5 should be in the rainy season of summer and autumn, and the weather forecast should be made 7 ~ 15d before the effective rainfall.

3.4.4 Management after broadcasting

The sowing area should be managed by special personnel, and it is forbidden for people and animals to enter the sowing area for grazing, as well as activities such as mowing grass and digging roots to destroy seedlings and trees.

4. Tending management of sand-fixing afforestation

After sand fixation and afforestation, young forest tending management should be strengthened, and young forest replanting, weeding, intertillage management and young forest management and protection should be carried out in time. All management work shall be carried out in accordance with the relevant provisions in Part I of GB/T 16453.2. ..

Second, understanding and implementation

Sand-fixing afforestation refers to the construction of main windbreak and sand-fixing forest belt, farmland shelterbelt, coastal windbreak forest belt, tuyere afforestation and sheet-like sand-fixing afforestation in sandstorm area. This section mainly introduces the planning and design, tree species selection, construction and management of sand-fixing afforestation. Planting density must be considered in combination with water conditions, and large density cannot be pursued alone. Aerial seeding afforestation is a method of aerial seeding, which is suitable for some sparsely populated areas or areas in urgent need of large-scale vegetation and lack of labor. It has the characteristics of high speed, high efficiency and low cost.

Because this section is the key to prevent wind erosion, compared with the original standard, it has changed a lot:

(1) Delete the introduction of "sand-fixing afforestation" in the original standard 5, including main windbreak and sand-fixing forest belt, farmland shelterbelt, coastal windbreak forest belt, tuyere afforestation and flaky sand-fixing afforestation.

(2) On the basis of the original standard of windbreak and sand fixation, it is changed to windbreak and sand fixation. Highlight its dual role of blocking and fixing sand.

(3) According to the original standard 5.1.1.2 "Farmland shelterbelt network (including grazing shelterbelt network), the direction of the main shelterbelt should be perpendicular to the main wind direction, or the deviation angle should not be greater than 30 ~ 45. The secondary forest belt should be perpendicular to the primary forest belt, and the primary forest belt and the secondary forest belt can have a certain deviation angle due to the limitation of topography and geomorphology. Low-lying areas can "follow the water"; Flat areas can "follow the road"; In the wind erosion hilly area, the main forest belt can be laid along the contour line, and the auxiliary forest belt can be connected with the roadside greening and river bank greening on the up and down slopes to form a forest network. Changed to "farmland shelterbelt network (including grazing shelterbelt network), the main wind damage area should use rectangular grid, and the main wind damage area can use square grid. The strike of the main forest belt should be perpendicular to the main wind direction, or the deviation angle should not be greater than 45. The secondary forest belt should be perpendicular to the primary forest belt, and the primary forest belt and the secondary forest belt can have a certain deviation angle due to the limitation of topography and geomorphology. Low-lying areas can "follow the water"; Flat areas can "follow the road"; In the wind erosion hilly area, the main forest belt can be laid along the contour line, and the auxiliary forest belt can be connected with the greening of the upper and lower slopes and the greening of the river bank to form a forest network. That is, "rectangular grid should be used in the main wind disaster area and square grid can be used in the main wind disaster area", and the use of rectangular grid and square grid is distinguished. As the wind direction is the main configuration parameter in the design of forest belt, forest network or shelter forest system, the deviation degree of the main forest belt direction from the main wind direction is changed from "not more than 30 ~ 45" to "not more than 45". When the square forest network forms an angle of about 45 with the wind direction, the cross-sectional area with protective effect is the largest. The reason is that when the wind direction intersects the forest belt obliquely, the cross-sectional area of the wind passing through the forest network increases due to the interaction between two adjacent forest belts. Forest nets are generally square, but not necessarily square (mostly rectangular). When the wind direction is oblique to the forest network, the protection efficiency is not inferior to that when the wind direction is orthogonal to a single forest belt, and when the length of two adjacent forest belts is not far apart, the protection efficiency remains unchanged. Therefore, it can be considered that the protective effect of the forest net is significant when the wind direction is perpendicular to the forest net, and it is also significant when the wind direction is oblique to the forest net, which makes the standard more accurate.

(4) The original standard 5.1.1.3 "Coastal windbreaks should be set according to the natural distribution trend of beaches and coastlines" was revised to "Coastal windbreaks should be set perpendicular to the main wind damage direction, or can be set according to the natural distribution trend of beaches and coastlines". The design of windbreak forest that should be perpendicular to the main wind damage direction has been added.

(5) The original standard 5. 1. 1.2. 1 "windbreak and sand-fixing trunk forest belt" can adopt single belt or double belt respectively. Multi-belts can be used in areas with serious wind and sand hazards. Generally, the bandwidth is 50 ~ 100 m "instead of" windbreak and sand fixation and basic trunk forest belt ",and single belt or double belt can be used respectively. Multi-belts can be used in areas with serious wind and sand hazards. Generally, the bandwidth is 50 ~ 100 m, the bandwidth in the front area of large-scale quicksand invasion can reach 200 ~ 1000 m, and the allowable bandwidth in the area bordering oasis and sand dunes is 30 ~ 50 m ". The new standard greatly increases the width of windbreak belt and enhances the effect of sand prevention and fixation.

(6) The original standard 5. 1. 1.2.2 "Farmland Shelterbelt Network" should have a main bandwidth of 8 ~ 12m and a sub-bandwidth of 4 ~ 6m. In sparsely populated areas, the main bandwidth of 5 ~ 6m and the sub-bandwidth of 3 ~ 4m can be changed to "farmland shelterbelt network", and the main bandwidth should be 8 ~ 4m.

(7) The original standard 5. 1. 1.2.3 "Coastal windbreak belt" should be determined according to the intensity of sea breeze and beach conditions, with a general width of 10 ~ 20m and a maximum of 100 ~ 200m "and changed to" coastal windbreak belt ".

(8) On the basis of the original standard 5. 1. 1.3.2, "the grid area of forest network is generally 15 ~ 20hm2, with the maximum not exceeding 30hm2, and the area of severe sandstorm is controlled below 15~20hm2".

(9) The original standard (5. 1. 1.4. 1) added coastal shelterbelts to the applicable types of sparse forest belt structure.

(10) In the original standard 5. 1. 1.5, "four mixed types are arbor-shrub mixed, arbor mixed, shrub mixed and comprehensive mixed" was deleted, because it is introduced below.

(1 1) Delete "beneficial to the development of agriculture, forestry and animal husbandry" in the original standard 5.2. 1.

(12) Delete the original standard 5. 1. 1.2 "Tree species should be barren-resistant, drought-resistant, wind-resistant, sand-cutting-resistant, sand-burying-resistant, fast-growing, well-developed root system, many branches, large crown width, easy reproduction, pest-resistant, quick-acting and economical in improving sandy land. The tree species selected in the north must be cold-resistant and the tree species selected in the south must be high-temperature-resistant. It is changed to "Tree species with waterlogging tolerance, salt tolerance and wind resistance should be selected for afforestation along the coast and lake", which simplifies the language of the new standard.

(13) Delete several poplars in the original standard 5.2.2. 1, namely "(Populus cathayensis, Populus euphratica, Populus simonii, Populus hopeiensis, Populus hopeiensis, Populus Hezuo and Populus Daguan)".

(14) The original standard 5.3.2. 1. 1 "First-class and second-class seedlings are required, but exotic seedlings are not allowed" was changed to "Bare-root seedlings should conform to GB6000 and container seedlings should conform to LY1000-9/kloc-0. Among them, GB6000 refers to the seedling quality classification of main afforestation tree species, and LY1000-91refers to container seedling raising technology.

(15) Delete the classification of cutting (pressing) afforestation technology in the original standard 5.3.3 "including cutting, layering, tall stalks and lying stalks".

Third, examples.

Farmland shelterbelt network is an ecosystem project that gives consideration to ecological, economic and social benefits, is an ecological barrier for agriculture and water conservancy, and is also a fundamental measure to realize the comprehensive management of fields, forests, ditches, roads and canals and maintain the ecological balance of the plain. Doing a good job of farmland forest network is the need to establish an ecological agricultural area, and it is also the basic work to ensure stable and high yield of grain and cotton in agricultural areas.

Theory and Practice of Farmland Shelterbelt Construction on the South Bank of the Yellow River in Ordos City

1. Natural conditions

The south bank of the Yellow River in Ordos City belongs to a typical continental climate, and the degree of continental climate is 75%. The annual average precipitation is 300mm, which is mostly concentrated from June to September, accounting for 70% of the annual precipitation. The annual evaporation is 2 160 mm, the annual average sunshine hours are 3 194h, the annual average temperature is 6.5℃, the highest extreme temperature is 40.2℃, and the lowest is -32℃. The number of windy days with an annual average wind speed greater than 2.7m/s is more than 180, and the number of sandstorm days is 27, with the longest of 38 days, which mostly occurs from 165438+ 10 to April of the following year, mainly from the northwest wind. Frost-free period 120 ~ 140 days, with large temperature difference between day and night. Meadow soil, saline soil, swamp soil and aeolian sandy soil are mainly distributed along the river.

2. Planning and design of sand fixation and afforestation

(1) Structure selection of farmland shelterbelt. According to the size and distribution of light-transmitting pores and wind-proof characteristics, the structure of forest belts is usually divided into three types: sparse, ventilated and tight.

1) Sparse structure type: tall trees and shrubs, and shrubs are mostly arranged on one or both sides of the forest edge. Its longitudinal section has relatively evenly distributed light holes. Where there is no suitable shrub species, it can be replaced by planting trees on the side. The porous structure forest belt can reduce the slow wind speed, and there will be no wind erosion in the forest belt and near the forest edge, which is suitable for construction in areas with serious sandstorms. The minimum weak wind zone appears on the downwind side for 3-5h, the wind speed is reduced by 53%-56%, and the relative effective windproof distance is 25H(H is the width of forest belt, in m, the same below).

2) Ventilation structure type: In the pure forest belt of a single tall tree species, the canopy is tightly airtight and the lower part is light-permeable. Wind energy smoothly passes through the macropores between the lower trunks, forming many ventilation pipes. Narrow forest belts can be mixed by plants or rows, and wide forest belts can be mixed by belts or rows. The minimum weak wind zone appears on the downwind side for 3-5h, and gradually increases with the distance. The relative effective windproof distance is 30H, and the average wind speed decreases by 24.7%. The shelterbelt with ventilation structure has the largest protection range, especially when the main wind is not vertical (the deflection angle is not more than 30 ~ 45), which is very suitable for crop planting.

3) Tight structure type: Three or two kinds of trees and shrubs are selected for mixed forest belt, which is wide, tight from top to bottom, opaque and windproof. Interrow, zonal and zonal mixing can be adopted, trees and shrubs can be mixed between plants or between rows, or shrubs can be arranged beside forest belts. The minimum weak wind zone appears on the downwind side of 1 ~ 3h, and the wind speed decreases by 59.6% ~ 68. 1%. When the relative effective windbreak distance is 10H, the average wind speed decreases by 30. 16% within 30 hours. For farmland shelterbelts, the structure is compact and not suitable for crop planting, and the windproof distance is the smallest, so they are generally not used.

After the above comparison, combined with the actual situation of the comprehensive agricultural development land management project area, it is determined that the ventilation structure forest belt is adopted in this area.

(2) Selection of farmland shelterbelt configuration mode.

1) Allocation model of farmland shelterbelt in Yellow River diversion irrigation area. The farmland shelterbelt in the irrigation area of Yellow River Diversion adopts the allocation mode of forest along the road and forest along the canal, and occupies as little land as possible. Trees are usually planted along irrigation canals, roads and ridges. Planting 1 ~ 3 rows of trees on both sides of the tractor-ploughing road and the main branch canal to form a main forest belt perpendicular to the main wind direction or with a deviation angle of not more than 30 ~ 45; Plant 1 row of trees on the side of the kitten canal and on the ridge of the field with the spacing of 1.5m to form a secondary forest belt. The main forest belt is perpendicular to the secondary forest belt, and the grid area of shelter forest is 250 ~ 400 mu.

2) Allocation mode of farmland shelterbelt in pure well irrigation area.

A. forest-road-forest structure. 1 ~ 2 rows of trees are planted on both sides of the tractor-ploughing road. The main road is 6m wide and the auxiliary road is 4m wide. The distance between the main forest belts is 300~400m, and the distance between the auxiliary forest belts is 500m. The main forest belts are vertical to the auxiliary forest belts.

Advantages: convenient construction, less land occupation, fast growth of trees and good road protection effect.

Disadvantages: first, the forest belt is a serious threat to the land, and the contradiction between forest farmers is great; Second, the contradiction between forestry and animal husbandry is great and management is difficult; Third, it is not conducive to mechanized operations. This configuration mode has a low saving rate and is generally not used.

B. forest road structure. The forest bandwidth covers an area of 2.5 ~ 4m, the main road is 6m wide and the auxiliary road is 4m wide. Ditching for afforestation. The depth of the tree ditch is 60 ~ 70 cm based on the horizon, the width of the ditch bottom is 2 ~ 3 m, and the width of the upper mouth is 2.5 ~ 4 m. The ridge on one side of the farmland. The main forest belt spacing is 300 ~ 400 meters, and the secondary forest belt spacing is 500 meters. The main forest belt is vertical to the secondary forest belt.

Advantages: first, it is easy to cultivate and manage, especially convenient for irrigation, which can improve the survival rate and preservation rate of afforestation; Second, it can reduce the threat of forest belts; Third, the tree ditch can also play a role in drainage.

Disadvantages: there is a forest side, which slightly affects mechanical farming.

C. road-forest-road structure. The areas of roads, forests and roads are 4.5m, 2.5 ~ 4m and 4.5m respectively, all of which are planted by ditching. The depth of the tree ditch is 60 ~ 80 cm based on the horizon, the bottom width is 2 ~ 3 meters and the top width is 2.5 ~ 4 meters. 2 ~ 3 rows of trees are planted in the tree ditch. The distance between forest belts is 500 meters.

Advantages: First, it is easy to cultivate and manage, which can improve the survival rate and preservation rate of afforestation; Second, effectively reduce the threat of forest belts, and the contradiction between trees and crops for water, fertilizer and glory is not prominent; Third, it eased the contradiction between forestry and animal husbandry; Fourth, effectively avoid the damage to trees in the process of farmers' farming; Fifth, it is convenient for mechanized farming; Sixth, the means of production and agricultural products are convenient and smooth.

Disadvantages: The planned roads occupy more land.

According to the analysis of afforestation effect, the allocation mode of farmland shelterbelt should adopt scheme 2 and scheme 3.

3. Tree species selection of farmland shelterbelt

(1) Tree species selection: usually choose tall trees with deep roots and high economic value. Such as Xinjiang poplar, Salix matsudana and Pinus sylvestris var. mongolica. Quercus mongolica and Pinus tabulaeformis.

(2) seedling size: The seedling size of arbor is more than 3.5m high (2.5m above ground when planting), with DBH of 3 ~ 5cm, and there is no frost damage, plant diseases and insect pests, mechanical damage and other high-quality seedlings. In the same tree ditch, the DBH of seedlings should be the same.

(3) Soil preparation: The Yellow River Diversion Irrigation Area and farmland land leveling, canal repair, road repair and other projects are carried out at the same time, which is generally completed in autumn, and afforestation is carried out with excavation in the following spring. In autumn, the well irrigation area is combined with road construction to excavate the tree ditch, and the loose soil at the bottom of the ditch is flat and the slope is neat. In the spring of the following year (afforestation in early April), the planting pit was dug by hanging lines and drawing lines, and the planting pit was dug by lines. The specifications are generally 60cm×60cm×60cm, and the spacing between plants is 2 m× 2 m. While digging holes, trees are planted.

(4) Afforestation: water the nursery once before emergence, and soak it in water for 3-5 days after transportation to the project area. When planting, draw a planting depth (60cm) line on the saplings with paint, then set the height of the aboveground part at 2.5m, and paint the incision to prevent water loss, so as to take it away with planting.

(5) Replanting: If a forest belt is short of trees and broken, it will definitely affect the expected structure of the forest belt and reduce the protective effect, so replanting must be carried out in time. What seedlings are missing, what seedlings are replenished, how much is missing, and how much is replenished.

4. Farmland shelterbelt tending management measures

(1) Implement forest right in time. After the completion of farmland shelterbelt project, adhere to the principle of "who operates and benefits", and auction or contract farmland shelterbelt to units or individuals. The property right of forest trees belongs to the purchaser, and the forest right certificate is issued by the forestry department to protect the interests of the shelter forest contractor. When the shelter forest is renewed and utilized, the contractor (or purchaser) of the shelter forest and the land contractor next to the shelter forest will share the forest income in a ratio of 7: 3, so that farmers can also get some benefits, but the renewal and utilization can only be implemented after the approval of the relevant departments.

(2) Strengthen young forest tending management. Young trees must be cared for in time to ensure the normal growth and development of trees. Tending management includes watering, loosening soil and weeding, pruning, germination, management and protection, pest control and so on. L ~ 3 times a year, 1 year, watering in winter when it freezes, twice a year in the second to third years, and pruning in the third year only removes abnormal branches and combined branches. The height under the branch is 65438+ 0/3 of the height of the tree.

(3) Strengthen management and protection measures. By ditching afforestation, the contradiction between farmers and foresters was basically solved. However, with the development of animal husbandry in agricultural areas, the contradiction between forest and animal husbandry is more prominent, and livestock deforestation incidents occur from time to time, so it is necessary to strengthen management and protection measures. First, strengthen the construction of forest protection team and send forest guards with strong sense of responsibility and diligent night care; Second, investigate and deal with deforestation cases in a timely manner and increase penalties; The third is to reward the well-managed project area and fully mobilize the enthusiasm of cadres and masses in the project area to love forest protection; The fourth is to bind the trunk with willow branches and other materials or apply white brush medicine to prevent livestock from eating. From 2004 to 2007, the trunk was bound with asbestos mesh cloth in the agricultural comprehensive development project area of Dalat Banner, with low cost and excellent protection effect.