Podzol

Boreal Lin Zhibei Under development soil . Widely distributed in Eurasia North and North America In the north, things are continuous strip, Southern Hemisphere Only in the mountain vertical zone. About 9% of the earth's land area. In Chinese, mainly distributed in Greater Khingan Range North and The Qinghai Tibet Plateau The edge of the mountain. In the cold wet coniferous forest, the soil was in the wet state, thus creating conditions for reductive leaching; fungi as the main microbial decomposition of forest litter, resulting in Fulvic acid The advantage of the large number of organic acid , and the lack of neutralization, the soil solution remains Acidic Strong acid. Under strong acid condition, the soil organic acid chelate leaching and deposition, the formation of podzoluvisols.
Podzol

Podzol brief introduction

Low temperature and humid climate and cold temperate coniferous forest vegetation under strong acidity, the underlying development of iron aluminum deposited soil. China also bleached soil. stay Eurasia North and Canada showed a continuous zonal distribution in Chinese Greater Khingan Range The southeast edge of the north and Qinghai Tibet Plateau Alpine vertical strip
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Small area distribution. In the cold wet coniferous forests, the upper layer of soil with deep litter layers (01) and litter decomposition in half (02). The formation of strong acidic organic acid decomposition of litter, destruction of the humus, silicate, iron and aluminum oxides state downward eluviation and deposition, the formation of the ashable layer gray white, silica enrichment (A8sub>2). On the surface there is often stagnant water, soil in the wet state, and accompanied by anaerobic reduction, ferrous leaching, away from the phenomenon of iron, with rust markings in grey soil. A dark sombric horizon (Bh) and the iron and aluminum oxides deposited layer (Bir). Podzoluvisols with coarse stick texture features, with a strong acid reaction (pH4.0 ~ 5.5), low base saturation, the basic characteristics of different obvious profile. If the A2 layer is more pale, bottom layer (B layer), combined humus iron and aluminum plate, called podzol. U.S.A The soil taxonomy called lime soil. Podzolized soil distribution area is important Chinese forest production base, where the weather is cold and wet, shallow soil, low fertility, not a large area of agricultural reclamation, local plant Wheat sowed in spring , Potato . Is also a sub class podzoluvisols podzoluvisols categories under. Podzolized soil can be divided into podzolic brown podzolic gleyic podzoluvisol, and three sub categories (according to the classification method of China scientists designated). The ashing subgroup ashing degree of strong, profile configuration is 0 - AH - E - Bsh - C, there was a continuous profile and the gray ashable layer and obvious. iron Aluminum deposition, humus has certain deposition. Located in high altitude or high latitude area.

Podzol geographical distribution

Podzolized soil is widely distributed in the northern hemisphere in the northern, northern Eurasia and North America, the zonal distribution stretches, including Europe and
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Norway, Sweden, Finland, Poland and the former Soviet Union in parts of Europe, Asia and Siberia, Canada and the United States are distributed in North central. In the southern hemisphere latitudes due to the corresponding water occupied, lack of broad podzol development area, so there is no podzoluvisols distribution, according to statistics, the total area of the soil in the worldwide distribution of about 12 million 830 thousand square kilometers, accounting for world 9.3% of the total land area, in addition, there are also the distribution of alpine regions around the world, the area of about 9 million square kilometers, accounting for 6% of the total land area of the world, before Soviet Union In the podzol area is the largest, accounting for more than 50% of the area of class podzoluvisols.
Podzoluvisols smaller Chinese, has been found only in northern Greater Khingan Range and Qinghai Tibet Plateau alpine and sub Alpine vertical belt. But the area is not a good statistics.

Podzol Soil conditions

Podzol climate

Podzoluvisols distribution in the cold temperate humid climate zone, the southern boundary and roughly North latitude A 50 degree line, climate The characteristics of winter is long and cold, the seasonal changes of temperature
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Great, rainfall concentrated in summer. The eastern and western regions of Eurasia Continental climate has a great difference, the west is often wet and warm climate, the annual average temperature at 0 degrees Celsius; the western continent warmer, the annual average temperature is 4 to 5 DEG C, Eastern low, low to -7 ~ -8 C, from west to East descending; the average temperature in January, the -5 -15 degrees centigrade, Eastern -18 ~ -20 degree; the average temperature of July, north of 10 to 12 DEG C, 16 ~ 20 degrees south. The annual precipitation decreased from west to East, West Coast more than 1000 mm, 300 mm to 600 mm in the Middle East, 300 to 400 mm, the northeast of at least 200 ~ 300 mm. In North America podzolized soil distribution area, January average temperature at -20 Deg. C, July average temperature of 16 degrees to 18 degrees, the annual precipitation in North and West is 250 to 500 mm, up to 500 ~ 1000 mm in the east. In the China podzolized soil distribution area, the annual average temperature of -1 to -5 DEG C, January temperature of -30 DEG C, the absolute temperature is -50 degrees, more than 10 DEG C temperature for 1500 ~ 1700 degrees, annual rainfall of 400 to 500 mm, dry <1.0, frozen layer depth of 2 - 3 meters.
Although the cold temperate zone Precipitation Not much, but the low temperature of winter cold, snow is very thick, greatly reduces water evaporation Effect of permafrost are widely distributed, surface moisture adequate for leaching and incubation effect.

Podzol vegetation

The podzolic coniferous forest vegetation in the main tree species, such as Picea , Abies , Pine , Larch Etc.. stay Eurasia In Western Europe, the forest composition is relatively simple, with spruce and pine constitute a single landscape, to the east by the Siberia pine, spruce, larch, pine and other alternative short Siberia. More complex in North American coniferous forest. Good drainage area of spruce and fir; poor drainage area is black fir, pine, larch and tamarack Jiekeshi. In Chinese, Greater Khingan Range northern coniferous forest in Rhododendron Larix and Pinus sylvestris or, southwest mountain, subalpine fir, spruce and Rhododendron in the southern part of the main components of broadleaf ashing, increased, a mixed forest belt. Because the area podzol soil freezing period is relatively long, freezing and thawing of plant roots, and in the coniferous forests of the light is not enough, resulting in the understory herbaceous vegetation is sparse, groundcover plants mostly mosses and lichens or ferns and other lower plants, forests are often caused by Swamp The phenomenon of.

Podzol The topography, parent material

Podzolized soil distribution area terrain is mostly mountainous and hilly and plain, generally mild slope, soil parent material for the Pleistocene glacial deposits, and sandstone, mudstone, clay and limestone weathering, in Chinese also have the parent material for the volcano. In general, the strong permeability of sand soil podzoluvisols most rapid growth.

Podzol The soil forming process

Podzoluvisols biggest feature is a spodic horizon, so the soil forming process is mainly the ashable layer formation and deposition layer forming process.

Podzol The ashable layer formation process

In the cold wet coniferous forest, slow to microbial decomposition of organic matter, Litter Year after year layer thickening, and peat layer development, its content can be more than two times its own weight, thus creating favorable conditions for leaching. Containing tannin, resin, wax and so on is difficult to decompose more coniferous litter, resulting in semi decomposed litter in surface accumulation, and the material base content rarely, organic acid can not litter decomposition which is completely neutralized by acid base, the environment is very strong, suitable for fungal life, microorganisms in fungi, on the one hand, the organic matter mineralization and release of various base, while producing fulvic acid, which is the main conditions of ashing deposition process. Fulvic acid is very strong, the dissociation degree, strong hydrophilicity, infiltration of soil solution, because the substitution of hydrogen ions, the base was replaced and leaching. In the low temperature and moisture conditions, organic matter decomposition slow release base do not neutralize fulvic acid, hydrogen ion with free infiltration water poured into the residual mineral soil layer below to cause of the ashing process, ashing process can be divided into the following four stages:
The first stage, carbonate leaching stage decomposition of hydrogen ions into the mineral soil, first interact with soil carbonates, caused by decomposition of calcium and magnesium base, the formation of fulvic acid and fulvic acid calcium magnesium, with water to lower leaching section;
The second stage, the decomposition of exchangeable cations leaching stage when carbonate decomposition and leaching, fulvic acid to interact with soil minerals in the exchangeable base, the base is hydrogen ion substitution leaching, and make continuous and dispersed clay leaching ;
The third stage, iron, aluminum, manganese leaching decomposition stage in cold wet anaerobic conditions, iron and manganese was reduced to Fe++, Mn++ and the infiltration of humic acid complexes and leaching, iron oxide and manganese oxide black red and yellow into Fe++, Mn++ leaching, under humic matter the soil layer, the color gradually became shallow. As a result of continuous acid leaching results, surface of fine particle leaching caused by soil texture become coarse, iron and manganese in continuous reduction leaching at the same time, because the soil colloid gradually saturated with hydrogen, and kaolinite damage, the formation of soluble iron, aluminum, silicon and other fulvic acid complex salt with colloidal solution or solution under the condition of leaching and precipitation, non crystalline silica powder, forming a layer of white flake structure leaching ashing or structure.

Podzol The formation of illuvium

From the ashable layer leaching fulvic acid calcium, magnesium, iron, manganese and other inorganic acid salts and a small part of the salt and iron, aluminum and silicate colloid until the lower, due to neutralization of acid solution is more and more abundant and the base salt deposition, the permeability of upper fungal decomposition process consumes a lot the oxygen and ash layer caused by the wet state, the soil in the lack of oxygen, anaerobic microbial activity and condensed matter deposition sol layer makes various salts deposited down the formation of reddish brown or reddish brown, and even the formation of iron pan or clay layer. In the deposition layer, due to poor ventilation, possibly with gray white or gray green gley layer is formed. In general, formed in the spodic layer at the same time, also for the humification process.
The world is horizontal zonal distribution podzoluvisols huge, north-south span, many mountain vertical zone spectrum in distribution, the regional differences of the natural conditions of formation of podzolic soil is also great. Therefore, soil properties reflect the soil forming process also has many differences. For example, China Greater Khingan Range At the north end of the former Soviet Union and North America and podzoluvisols podzoluvisols differ, and is also different Chinese podzol mountain area, northern Greater Khingan Range is located in high latitude region, lower altitude (800 meters below), cold climate, affected by permafrost backwater, the leaching effect is weak, although the Bt layer, but sombric horizon does not grow, while in the southwest mountain area, high altitude, cold climate, rainfall, soil clay is slightly down, but no clay humus deposition, leaching and deposition effect is strong, more than the formation of humus bleached soil. Because of regional differences, the classification index and soil names are different, for example, soil classification index of soil classification system in the United States in all soil layers and bleaching ash deposit, free iron and carbon percentage percentage ratio is less than 6, the cation exchange capacity of podzolic soil is very low, the ashable layer cation exchange the amount of about 7 mol (+) per kilogram of soil, the former Soviet Union from 0.8 to 12 per cent Moore (+) per kilogram of soil. Base saturation is low, about 29% of the United States, the former Soviet Union was 20 - 29%, some level of base saturation is often less than 10%, and the northern Greater Khingan Range China podzolized soil cation exchange capacity (high ash layer is 19 ~ 22 per cent (+) mol / kg soil) high base saturation (ashable layer <40%, high up to 70 there is a big difference between ~ 85%). In naming, traditionally called Podzol However, China called bleached soil (Bleachedpodzolicsoil), which also reflects some substantial differences in various regions on the causes of podzoluvisols.

Podzol The main characters

Podzol Diagnostic horizon and characteristics

The United States is a feature of lime soil coarse dark surface, bleaching layer and ash deposit of all sub layers, usually free iron and carbon percentage percentage ratio is less than 6. Spodic horizon is a diagnostic layer of podzoluvisols.

Podzol Morphological character

Podzol profile difference, soil type O-Ah-E-Bsh-C. The surface is dark litter layer (O); organic matter deposition (Ah); gray leached layer (E), this layer containing silica white powder, flake structure, forest vegetation in some bleaching layer was pink in acid Shrub Under a grey; Illuvium (Bsh) yellow brown, with iron manganese cutans, some duripan and iron pan; lower for frost weathering products section, in 30 - 50 cm appears frozen layer or clastic rocks.

Podzol Physicochemical properties

1 the surface of the organic content is high, up to 400 grams per kg, down sharply. In the composition of humus in the fulvic acid and Hu Min acid and fulvic acid ratio of less than 1, in the bottom layer can be lower than 0.3.
2 the soil is acidic reaction, pH is often less than 5.5 or 5.
3 exchangeable acidity is higher and higher up to 10 per cent more than Moore (+) per kilogram of soil, and the ashable layer most, up to 15 mol% (+) per kg, soil exchangeable hydrogen exchange accounted for more than 40 of acid - 50%, and the leached layer and the bottom layer of about 10 ~ 13%.
4 cation exchange capacity is low, generally less than 12 mol% (+) per kilogram of soil, and the northern end of the Greater Khingan Range China bleached soil is higher, up to 19 - 22 mol% (+) per kg. Base saturation is low, generally less than 29%, while the China podzol <40% mountain podzolized soil amounted to 70 to 85%.
All 5 have obvious loss of oxide in the whole section, especially in Ah and E layer is the most significant, in addition to calcium, magnesium, silicon and other large leaching, iron and aluminum have distinct eluviation and deposition.
6 the content of clay from the surface down significantly, some deposited layer clay content is about two times the ashable layer, texture has obvious mutation. Clay minerals have obvious variation along the profile. Soil thin section microscopic observation found: primary minerals such as feldspar, mica and other Donglie, suffered in the weathering in sericitization, iron and water, resulting in secondary clay mineral alteration, the formation of new clay minerals and clay minerals, along the profile also had great variation, ash layer and surface layer of montmorillonite and the bottom is mainly kaolinite and hydromica, vermiculite and chlorite, illustrate the podzol formation process, the hydromica, vermiculite, montmorillonite, kaolinite, from 2 to 1: 1: 1 types of alteration process . In addition, the water storage capacity of podzoluvisols is limited, so for most crops, natural soil is thin podzol.

Podzol classification

The Chinese podzoluvisols, only the separation of a normal and a normal subclass podzoluvisols podzoluvisols Soil type The United States, soil classification in soil under the class divided into Aquod, iron dust, dust and four normal soil humus Subclass Then, on the basis of Diagnosis Layer properties and biological climate division unearthed, such as Orthod subclass divided into Placic Orthod, fragipan Orthod, frozen soil, normal normal normal development, weak tropical soil lime soil. Now all sorts of classification Divided into four Subclass :
1 podzoluvisols (Typicpodzolicsoil) frozen Orthod equivalent to American soil classification (Cryorthods), typical podzol soil classification in the United Nations (Orthicpodzols), unsaturated podzoluvisol (Dystricpodzoluvisols). Has the typical characteristics of podzoluvisols.
2 podzoluvisols (Podzoluvisols) equivalent of the classification of frozen soil humus (Cryohumod), the United Nations classification (Humicpodzols), saturated humic podzol podzoluvisol (Eutricpodzoluvisols). The distribution in forest thinning, herbaceous plant development zone. Its characteristic is in the water depth of 50 cm, increase the content of soil organic matter, Hu Min acid increased, a large amount of substitution, base saturation increase, reduce acid.
3 gleyic podzoluvisol (Glegicpodzolicsoil) equivalent to the United States the classification of partially frozen Aquod (Crya-quods), the United Nations classification gleyic podzoluvisols (Glegicpodzols). The upper layer of soil gleyization characteristics appear, the lack of Placic in spodic horizon or in the. The profile is O-Ah-Eg-Bgs-Cg.
4 brown podzolic soil equivalent to the normal dust subclass is part of the normal soil (Orthod), the United Nations classification Haplic podzol (Leplicpodzols). The ashing process is weak, profile configuration of O-Ah-E-Bs-C, no obvious gray level, pale brown, iron and aluminum deposition obviously, humus deposition is not obvious in distribution altitude With a slightly lower latitude area.

Podzol Utilization and improvement

The world's most natural forest podzolized soil distribution area, as Forest , Pasture Dry grass (haylend) and planting crops, and Chinese podzolic soil distribution area is China important production base of forestry. In forest harvesting, should minimize soil damage, so as not to cause soil erosion and reduce soil fertility. Because of the cold wet climate, shallow soil, strong acid, structure Poor, Botany Nutrient deficiency, low fertility, generally not in large area of agricultural.