In which regions of our country are dark brown earth soils distributed, and what crops are suitable for planting there?

Dark brown earth is a zonal soil formed under a temperate humid monsoon climate and mixed coniferous-broadleaf forests, and is an independent soil type separated from brown forest soil after the founding of China. Total K content is 15.7-19.3, the profile configuration is O-AB-Bt-C, humus accumulates in the surface layer, and the entire profile shows a medium to slightly acidic reaction, with a base saturation of 60-80%. The clay and iron-manganese contents in the middle of the profile are both higher than those of the eluvial horizons above and below it. Dark brown earth is also known as dark brown forest soil, and was once called brown podzolic soil and gray-brown earth. It was not until 1960, after the first national soil survey, that it was formally established as dark brown forest soil, namely dark brown earth.

So, in which regions of our country is dark brown earth mainly distributed? What crops are suitable for planting there?

Distribution regions of dark brown earth in our country

Dark brown earth is widely distributed, with a total area of 40.19 million hm², and is the largest type of forest soil by area in Northeast China. It is mainly distributed in the Lesser Khingan Mountains, the Changbai Mountains, the Wanda Mountains and the eastern slope of the Greater Khingan Mountains, extending north to Heilongjiang, west to the central part of the Greater Khingan Mountains, east to the Ussuri River on the border, and south to the Tieling and Qingyuan area of Liaoning Province and the Siping-Tonghua line.

To the north (upward), dark brown earth transitions to brown coniferous forest soil, and to the south (downward) it transitions to brown earth. Specifically, it is distributed below an altitude of 800m on the eastern slope of the Greater Khingan Mountains, below 900m in the Lesser Khingan Mountains, and below 1100m in the Wanda Mountains and the Changbai Mountains, and is one of the largest forest soils by area in Northeast China. Dark brown earth is also widely distributed above brown earth in the vertical zonation spectra of other mountainous areas across the country.

Due to its specific regional distribution, dark brown earth is often accompanied by special compositional conditions. The average annual temperature is between -1~5°C, the annual accumulated temperature of ≥10°C is 2000~3000°C, the soil freezing depth is 1~2, and can reach as deep as 3m, with a freezing period of 120~200 days. In some areas the seasonal frozen layer is especially pronounced. The annual rainfall is 600~1100mm, and the frost-free period is 115~135 days, belonging to a temperate humid climate zone.

The natural vegetation in the dark brown earth region is mainly mixed coniferous-broadleaf forest dominated by Korean pine. Because of the humid climate, there are many plant species, totaling more than 2000. The coniferous species mainly include shade-tolerant and semi-shade-tolerant species such as Korean pine, Manchurian fir, Siberian spruce and red-barked fir. There are many species of deciduous broadleaf trees, mainly including white birch, black birch, maple birch, Mongolian oak, spring elm, Manchurian walnut, yellow sandalwood and Manchurian ash. The understory shrubs and herbs are lush; common shrubs include Manchurian hazel, mock orange, Siberian ginseng, euonymus and lilac. Common herbaceous plants include horsetail, wheel-leaved lily, silverline grass and the genus Pyrola. Now, although the proportion of secondary forest is gradually increasing, it is still the main forest region of Northeast China. The terrain of this region is mainly mountainous.

Crops suitable for planting in dark brown earth

As a forestry base, dark brown earth should mainly be used for developing forestry. Larch, Korean pine, Manchurian ash and Manchurian walnut, which like fertilizer and moisture, should generally be planted on typical dark brown earth or meadow dark brown earth with a medium-to-thick humus layer in the middle and lower parts of mountain slopes. Korean pine in particular is a tree species with excellent timber quality and has high soil requirements, and is most suitable for planting on meadow dark brown earth and typical dark brown earth. Spruce, birch and others have strong adaptability and can tolerate poor soil, and can be planted on bleached dark brown earth and podzolic dark brown earth with poorer soil conditions.

In order to solve part of the food and vegetable supply in forest regions, consideration can be given to appropriately reclaiming a certain area on meadow dark brown earth, gleyed dark brown earth and typical dark brown earth with a thicker humus layer, to plant crops and vegetables.

For planted crops, cold-tolerant and early-maturing crop varieties can be chosen, such as wheat and potatoes, cabbage, radish and Chinese cabbage. Diversified management can also be developed according to the characteristics and advantages of mountainous areas, such as sericulture, beekeeping and fruit tree planting, so as to comprehensively utilize and develop mountain resources.

In addition, the dark brown earth region is also more suitable for developing ginseng cultivation. Actively developing edible fungus production, such as artificially cultivating high-grade edible fungi such as reishi and valuable medicinal materials, is also an effective way to comprehensively develop and rationally utilize the dark brown earth region.