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Section 5 Manual Update
With the improvement of the forest management level, all cutting sites have been artificially updated. Manual update basically uses the method of updating seedlings. The seedling renewal has the advantages of saving seeds, high preservation rate, early closure of young forests, easier management of tending and management, as well as the advantages of becoming forests and materials.
The success or failure of the renewal of Larix principis-rupprechtii plantation is closely related to the site conditions. Larch is a shallow root species, more than 80% of the roots are horizontal roots, hi fat, hi water, hi light is extremely strong. About 30 years old larch pure forest, because of its high density and rapid growth in the early stage, inhibited the regeneration ability of the undergrowth (half shrubs) and herbaceous plants in the forest, especially the pure larch forest where the barren mountain (relatively thin afforestation land) originated. After logging, still use larch as the main artificial reforestation, often affected by the effects of land degradation, renewal performance is not good, once encountered adverse environmental conditions such as water, nutrient supply is insufficient, easy to form a small old tree, or dead plant death This will have a great impact on the cultivation of the next generation of commercial forests. In the larch forests of the natural secondary forests with poplar and birch-like natural forests and fertile lands, artificial larch was planted after harvest. The growth of the young trees is still good. The main reason is that the logging land is fertile and the forest is generally dry. There are more undergrowth or herbaceous plants, more litter and more complex, will not destroy the physical and chemical properties of the soil and cause land degradation. This type of site to create larch commercial forest, can generally be used as two or three. However, considering the strategic direction of long-term development of forestry, it is of far-reaching significance and broad prospects to create renewal of coniferous and broad-leaved forest (patterns) in the larch cutting sites.
First, the advantages of mixed forest
(i) Prevention of land degradation
Due to the launch of the “Tianbao†project, the Mengzi Forest Management Bureau mainly focuses on harvesting pure larch forests. After the harvest, the tree species are still used for manual regeneration in the current year or the following year. The type of sandy loam (originally barren hills) in the access area is updated. The effect is poor, the main manifestation is: in the more drought conditions, the survival rate of young trees is low, even if the young trees have survived, the high growth is very slow, and there is no obvious advantage, the basal diameter of young trees from 5 to 6 years is less than 3M The tree height was 70-80M, and the annual high growth was less than 8M. Lateral branches developed, and some of the lateral branches grew significantly higher than the main branch height. Because there is no top advantage, the tree is flat, so it is called a small old tree. In 1999, the "Research on land erosion prevention and control technology for larch plantations" applied by the Mengzi Forestry Bureau was approved by the Hebei Provincial Forestry Bureau and a project was carried out (unfinished). The existing preserved saplings were pruned. , binding, righting (repairing lateral branches, erecting main branches, binding and fixing), interplanting of seabuckthorn and larch to increase the fertility of afforestation land, creating a coniferous and broad-leaved mixed forest, mixing needles and needles (larch and birch mixed) Pine; larch, spruce and other ways mixed show superiority. Therefore: Overcome land degradation, prevent soil from deteriorating, and create a mixed forest is the best way. The mixed tree species must first select the deep-rooted tree species to maximize the fertility of the deep soil and alleviate the drawbacks of the lack of surface fertility.
(B) Mixed forests help promote ecological balance
As we all know, maintaining biodiversity is the best hope in the development of forestry. Continuous cultivation of single larch will not only cause land degradation, but more importantly, the actual effect will directly affect productivity. Many research data from our country also show that Chinese fir and Pinus massoniana Plantation forests such as pine and other tree species, the second generation of forest productivity decreased by 30% compared to the first generation, even reached 50%, all these statements show that artificial pure forest is not conducive to the sustainable use of forest land and the continuous improvement of forest management efficiency . The basic conditions that constitute the forest include forests, shrubs, herbs, wild animals, and microorganisms. After a typical larch plantation enters middle-age forests, the growth of the shrubs is inhibited. When the density is high, shrubs under the canopy are almost Extinction has inhibited the regenerative capacity of herbaceous plants, resulting in the formation of “Qingtang†stands for most larch pure forests, and has formed the most unfavorable factor in maintaining species diversity. With the reduction of plant species, the species of wild animals and microorganisms also decreases with the changes in forest structure. According to statistics, the total area of ​​disease and insect pests in the Mengfu Forest Management Bureau has been more than 181,000 hectares (times) in the past 40 years, including 113,000 hectares (middle), which occurred mainly in artificial coniferous pure forests. The spread of pests and diseases in pure forests has increased the number of new insect species. The harm has become increasingly serious. The coniferous pure forest has almost lost its self-control ability. Adjustment of the structure of forest species and the formation of large-scale coniferous and broad-leaved mixed forests in the forest area can overcome the coniferous pure forest. The vulnerability to pests and diseases. Although the total area of ​​disease and insect pests in the Bureau was more than 181,000 hectares (times), only 0.13 million hectares (times) occurred in the mixed forests in the last two years, accounting for 0.71% of the total area. The causes of pests and diseases in the mixed forests occurred in mixed forests. The main reason is that 2 or 3 times of tending, cutting and retaining needles, make the proportion of conifers account for more (80% or more). Therefore, the construction of a mixed forest to promote appropriate mixed ratio can overcome the above similar problems.
Second, the mixed forest application model
To build a mixed forest of Larix principis-rupprechtii (model), the mixed proportion and model should be comprehensively determined according to the site conditions and various factors of the cutting site, including the fertility status of the felling site, soil texture, elevation, aspect, slope, and mixed tree species.
(a) Tree species selection
In the cutting plots where the altitude is appropriate and the soil is fertile, the choice of broad-leaved trees such as larch and birch should be selected. The maturation period is basically the same, and larch and poplar (real seedlings) are mixed, and the maturation period is basically consistent. In the relatively dry and poorly soiled felling areas, Scotch pine and birch trees are selected as mixed trees. Because of the high altitude, land fell severely degraded cutting sites. Choose sea buckthorn or Caragana korshinskii and Lespedeza as a companion species.
(B) The mixed mode is divided into three major categories based on site conditions.
1 The cutting plot with good elevation and good site conditions is suitable for large strip mixed arrangement. Use larch 1m × 1m × 5 lines + hardwood 1m × 2m × 5 lines or larch 1m × 2m × 10 lines + hardwood 1m × 2m ×10 lines, and the mixed ratio is basically kept at 5:5.
2 Pairs of cutting lands with less site conditions (avoiding heavy ploughing), and mixed trees with Pinus sylvestris and birch trees. Pinus sylvestris 1m × 2m × 3 rows + birch trees 1m × 2m × 3 or dumplings Pine 1m × 2m × 5 lines + birch 1 m × 2m × 5 lines. The main purpose of mixing small and medium-sized belts is to increase the amount of litter, change the physical and chemical properties of the soil, increase the content of organic matter in the forest land, and prevent soil degradation.
3 Larch or spruce was selected as the main tree species in the land with high altitude and land degradation, mixed with shrubs (Hippophae rhamnoides, Caragana korshinskii, or Lespedeza davidiana), and the main tree species spacing was 1.5 m×2m + associated species 1.5 m×2 m, which reduced the main tree species. The initial planting density increases the associated tree species, regulates the forest environment, and promotes the growth of major tree species.
Third, artificially updated planting density
According to the forestry experience of many years of afforestation, the initial planting density is generally between 330 and 440 plants/mu. This is mainly to give full play to the mass effect of the main tree species in the young period, and the density is appropriately increased, followed by the control of a certain insurance factor. There is room for the selection and utilization of land resources, but it is only appropriate to reduce the density of afforestation sites with severe land degradation, promote the supply of water and fertilizers, and ensure the normal growth of forest trees.
IV. Artificially updating seedlings and young forest tending techniques (refer to Chapter 4 Afforestation)
Chapter 7 Diseases, Insects, and Infestations of Larix principis-rupprechtii
Section 1 Major diseases of Larix principis-rupprechtii
Forest diseases refer to a series of pathological changes in the physiology, organization and morphology of trees caused by the invasion of pathogenic organisms or adverse environmental conditions in the process of growth and development of forest trees, which results in the slow growth of forest trees, deformity, and even death, resulting in economic losses. And affect the ecological environment, this phenomenon is called forest disease.
There are many pathogenic factors of forest diseases, which are generally divided into biological agents and non-biological agents. Pathogenic biological factors are fungi, bacteria, mycoplasma, viruses, viroids, parasitic seed plants, parasitic algae, parasitic nematodes, and parasitic mites. All plant diseases caused by biological factors are infectious and are therefore called infectious diseases (or infective diseases). Pathogenic abiotic factors refer to unfavorable environmental conditions that cause forest trees to go beyond tree adaptation. For example, low temperature can cause freezing damage, high temperature and strong light can cause sunburn, and lack of trace elements can cause deficiency of the disease. Forest diseases caused by non-biological factors are not contagious and are often referred to as non-infectious diseases (or non-invasive diseases). This type of pathogen mainly interferes with the normal physiological process of forest trees, so it is also called a physiological disease.
No matter what kind of forest diseases, there is a pathogenesis. The physiological, organizational, and morphological pathological changes caused by pathogenic effects on forest trees are called lesions. The process by which forest trees gradually show morbidity through a series of lesions is called the pathological process of forest trees (also known as pathological procedures). The presence or absence of pathological processes is an important indicator to identify whether or not forest trees have been damaged.
Symptoms of tree disease: Symptoms of forest diseases include symptoms and conditions. The condition refers to the abnormal state of the forest. Disorder refers to the characteristics of the pathogen in the diseased area. General fungal diseases have both symptoms and symptoms. Viruses and thymic plastopathies only have symptoms and do not show symptoms. Physiological diseases have no symptoms at all. In a nutshell, the morbid characteristics of forest trees after their illness are collectively referred to as the symptoms of forest diseases. Usually refers to the characteristics that can be observed by the naked eye. The types of disease symptoms of forest trees include yellowing, mosaics, spots, anthrax, ulcers, rot, rot, dead shoots, withering, leafy malformations, sores, tumours, branches, plexiflora, white powder, coal, rust , mildew, carcass, bacteria pus, lipid or flow plastic.
Forest disease diagnosis: Forest disease diagnosis includes forest tree disease investigation, symptom observation, pathogen microscopic examination, artificial induction test, serological reaction, and treatment effect inspection. These methods and measures are also the basic methods for studying forest diseases.
The main diseases of Larix principis-rupprechtii are larch early deciduous disease and larch shoot disease.
First, larch early defoliation
(I) Distribution and hazards
This disease is mainly distributed in Northeast China and North China in China. It was discovered in 1963 in the Mengbian Forestry Bureau of Hebei Province. The disease was the most serious planted forest and it was an important leaf disease of larch.
After larch leaves are sick, they can be defoliated about 40 days earlier, so it is called early larch larvae disease. The annual growth rate of tree stands increased by 21.3%, the DBH growth decreased by 74.4%, and the volume growth decreased by 21.3%.
(b) symptoms
The disease occurs in the leaves of various larch, first appeared in the tip or middle of the leaves 2 to 3 yellow spots, and gradually expanded to reddish brown spots, after the spots on the birth of small black spots, pathogenic spore devices. In severe cases, all needles turn brown, and the entire canopy is like a fire. By mid-August or late August, a large amount of fallen leaves will fall about 40 days earlier than normal trees. If the disease occurs for several consecutive years, it will seriously affect the growth of trees. The needles that fall on the ground form a large black spot, which is the ascendant cavity of the germ.
(c) Pathogens
The disease was caused by the Mycosphaerella larici-leptolepis -Ito et Al. The bacteria produces two spores, viz. spores and ascospores. The sporoderm is smaller than the ascidian cavity and is black and round. It was born under the epidermis of the leaf, and later it protrudes from the epidermis. The size is 85-90 microns. Sporophytes, colorless, short rods, 3.4 to 5.1 × 0.8 to 1.0 μm in size. The sub-cystic cavity is black, round or near-circular, with a diameter of 68 to 119 microns. It is buried under the epidermis of the overwintering diseased leaves and protrudes slightly after absorbing water. Ascospores are colorless, transparent, rod-shaped or cylindrical, with 8 ascospores, colorless ascospores, twin cells, long ovals, and fine ridges at the central septum, with a size of 13.6–17.0×2.7–3.4 μm.
(D) the incidence of the law
In the Mengzi Forestry Bureau of Hebei Province (Waichang County, northern Hebei Province), the diseased bacterium was wintered in fallen leaves. In the spring of the following year, ascospores are formed in ascospores and produce ascospores. In the middle of June, ascospores began to disperse, and from late June to early July, the ascospores spewed up. Ascospores spread with the airflow, in the case of larch needles, invaded by stomata after germination, over a few days the leaves became lesions, and gradually turned red-brown. From late July to late August, small black spots were generated on the lesions, which were sexual spores. The leaves began to fall in the middle and late August, and sometimes new leaves appeared after September. After entering October, the new leaves were frozen to death. After the diseased leaves landed, they were born with slightly larger black spots than the sporozoites, ie, the ascospore cavity. The sexual spores have no invasive ability, and only the ascospores can infect them, so the disease occurs once a year.
The occurrence of disease and its degree of harm are closely related to the ecological and environmental factors. After the larch leaves, the temperature is about 20°C, and the air humidity is more than 75%, which is conducive to the invasion of bacteria. Therefore, in the years when the temperature is low, humidity is high, and the amount of rainfall is large, the onset is early and serious. The large-scale larch pure forest has a serious disease, and the coniferous and broad-leaved mixed forest has a low incidence. Density of dense forest stands more than dense forest. The incidence of wormwood and undergrowth coverage greater than 90% of the total coverage of the stand was smaller, and the incidence of wood failure in the forest and the trail of pressed wood was relatively heavy. The disease becomes lighter when the forest age is more than 20 years old. After thinning, thinning trees are generally lighter than uncultivated diseases.
(V) Control methods
1. The forest management measures strongly promote the establishment of coniferous and broad-leaved mixed forests to avoid making large areas of pure forest. Strengthen young forest tending and timely cutting and cutting trees after closing.
2, physical and mechanical measures in the onset of artificial control of the fire to be ground material, both control of defoliation, but also increase soil fertility.
3, chemical control measures of the occurrence of the forest can be placed Pentachlorophenol and pentachlorophenol sodium or chlorothalonil smoke agent control, but also can be used 10% chlorothalonil oil agent or net dry oil agent for low-level spray on the ground or aircraft. The conditional area can be sprayed with 50% Dyson ammonium 600-800 times or 36% Mannson manganese 200-300 times, the effect is better. In the young forests that are not closed, biological pesticide polyoxin can be sprayed 150 times, Xingnong 660B 150 times or kasugamycin 400 times.
Second, larch shoot disease
(I) Distribution and hazards
Larch blight was first discovered and identified in Japan in 1939. The disease was discovered in China in 1970 and became popular in 1973. Domestic distribution in Liaoning, Jilin, Heilongjiang, Inner Mongolia, Hebei: Zhangjiakou City (Chongli County, Yu County), Shandong and other places, the Northwest has also been found. The disease is an important shoot disease of artificial larch, resulting in shoots, serious damage, rapid development, and some standoff rates of up to 100%, is a dangerous infectious disease, was listed as a national quarantine in 1980 ( The disease has not been found in the forest area of ​​the Mongol Forest Management Bureau.)
(b) Symptoms
The disease is harmful to the new shoots of 1-35-year-old larch seedlings and plantation forests. Saplings 6-15 years old are severe and widespread. The onset usually begins in early July and is most pronounced in the middle and late July. It usually starts from the main tip and then spreads downward from the top of the canopy. The tip of the diseased department is whitish green, and the top part is bent into a hook-like shape, becoming a purple-brown or gray-brown, and gradually defoliating downwards from the curved part. Afterwards, the young shoot shrinks, the stem becomes thin, and the resin often overflows. There is a cluster of leaves at the top and withered purple gray. In the late onset, the new shoots had been lignified, and the diseased branches did not bend and droop, but all the needles fell off. In the spring of the following year, the original shoots were replaced by lateral buds. If the incidence of consecutive years is to form plexiforms, the high growth stops, old trees form or all die.
From the end of August to June of the following year, spindle-shaped black spots, which are the sub-capsules of germs, grow on the shoots, especially on the branches and depressions of the curved part. He buried at the beginning and broke through the host epidermis at the time of maturity in June. After more than ten days of illness, he had dense round near-black spots on the back of the top leaves, namely the conidia of the pathogen and a small number of immature ascospores. Sometimes there are black round small projections on the diseased branches, ie pathogenic spores.
(c) Pathogens
The disease is caused by Botryia phaeria (Sawada) Shang. Ascendicular saccules are spherical or oblate spheroids, single or several clustered together beneath the epidermis, measuring 170-500 microns in diameter and 130-300 microns in size. The orifices are slightly prominent, with multiple ascospores and pseudosidelinings in the cavity. The ascus is colorless and rod-shaped, with a size of 120 to 140 microns and 25 to 45 microns. The top is round and the base has a handle. Ascospores are colorless, single cells, elliptic to spindle-shaped, and are 24 to 36 microns in size by 6 to 9 microns.
Conidia are of the type Macrosphoma. The conidia are spherical or oblate spheroidal, born under the epidermis and leaves of the shoots. They are slightly open to the eye. They are 120 to 245 microns in diameter and 170 to 210 microns in size. The conidial stems are straight and 3 to 7 microns in length. Conidia are colorless, single cells, elliptic to spindle-shaped, and are 24 to 30 microns in size by 6 to 9 microns in size.
Sporulators are also produced at the same time when the conidial device matures. The sexual spores are short-barreled, 3 to 6 micrometers and 1 to 2 micrometers. They are colorless and can be seen from January to February of the following year, but they do not have the ability to infect.
(IV) Incidence of disease
Ascospores and conidia are the primary sources of infection for this disease. The bacteria used hyphae, conidia, and immature ascospores to overwinter under the epidermis of new shoots and dead leaves at the top. In the middle and late June, the ascospores begin to mature. From late June to early August, large numbers of ascospores and conidia are scattered and propagated. During this period, the spore dispersal increases rapidly with rainfall.
Ascospores are transmitted by the wind, and conidia are poured onto the trees by rain. After drying, they spread with the wind. They can also spread by the reverse splash of rainwater.
In late June, ascospores spread to new shoots. After germination, they were invaded by wounds. After about 15 days of incubation, they developed symptoms. Near mid-July, they produced conidiospoiesis on diseased branches. Conidia mature and then infect nearby shoots causing reinfection. After the conidia have matured, they are re-infected several times. After the sexual cells are coordinated, an ascendant cavity is generated in the diseased part of the shoot.
Frostbite, frost damage, and the stand in the tuyere, due to many wounds, the bacteria are easy to infect, and the disease is heavy. Under optimum temperature, when the relative humidity is 100%, ascospores and conidia are easy to germinate, and when the relative humidity is less than 92%, the spores of germs do not germinate. Therefore, in the years of heavy rainfall in June, July and August, serious diseases occurred. Generally, on the windward side of forest margin, 6-15 years old larch young plants are the most affected.
(v) Control methods
1. Strengthen quarantine to prevent pathogens from spreading seedlings, scions, cuttings, small diameter materials, shoots, etc. Must be confirmed to be disease-free and can be transported.
2. Clearing Infestation Larch windbreak near the nursery is often a habitat for pathogens and other tree species should be replanted. Seedlings must be strictly inspected before going uphill, and the diseased seedlings must be burned and buried in time.
3. Avoid afforestation of larch forest at the tuyere to create needles, broad mixed forests, and avoid creating large areas of pure forest.
4. Chemical control In the diseased forest area, spray 60% thiophanate-methyl 500-600 times solution from June to August, or spray 75% chlorothalonil 500-1000 times solution, or spray 40% thiram 800-fold solution, Or spray 65% ​​on behalf of the Zinc 400 times, or spray 30ppm solution of the medical treatment, spray once every half a month, spray a total of 3 to 4 times. It can also be smoked once in July with sodium pentachlorophenol or ketandan.
III. Investigation and forecast of major diseases
(I) Investigation of the condition
1. Line investigation In August of each year, when there are obvious symptoms, a full-scale disease investigation is conducted using the diagonal method in the disease area to determine the extent of the disease, the degree of the disease and the area of ​​the disease.
2. Standard survey
(1) The standard establishment is to set up representative forest sites for disease occurrence. A standard site should be set every 500 to 1,000 mu. The standard site size should not be less than 100 forest trees.
(2) Detailed investigation In the standard area, 50 to 100 larch trees were randomly selected and each tree was investigated according to the grade standards of each tree, and the rate of diseased plants and the index of disease were calculated.
Larch larvae disease classification criteria for each wood disease
level
Representative value
Grading standards
1
0
Health-free or individual yellow needles
2
1
Canopy below 1/4 of tree canopy
3
2
Crown 1/4 to 1/2 needle yellow
4
3
Crown 1/2 to 3/4 coniferous yellow or brown
5
4
Crowns 3/4 above yellow or brown
Larch shoot disease per wood disease grade standard
level
Representative value
Grading standards
1
0
Healthy disease-free or individual shoot incidence
2
1
Up to 25% of canopy shoots
3
2
Crown incidence of 26% to 50% of shoots
4
3
Crown incidence of 51% to 75% of shoots
5
4
More than 76% of canopy shoots onset
Investigation of the number of diseased plants
Infected strain rate = ───────×100%
Survey the total number of trees
Σ (represents each disease level × number of plants in this stage)
Sensation Index = ─────────────────×100%
Survey total number of plants × highest representative value
3. Summary of illness investigation
(1) Occurrence area statistics for the early larvae of L. tuberculosis with a sensitivity index of 25 or more to calculate the area of ​​occurrence, larch shoot disease with a sensitivity index of 5 or more to calculate the area of ​​occurrence
(2) Hazard level
1 Larch early defoliation: Light (+) susceptibility index 25-40; Medium (+ +) susceptibility 41-65; Heavy (+ +) sensibility index 66 or more
2 Litter blight: light (+) disease index 5 to 20; middle (+ +) disease index 21 to 40; heavy (+ +) disease index above 41
(3) According to the summary of the investigation results, draw the disease distribution map and write out the condition report.
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