Density control technology of Pinus sylvestris var. mongolica flaky shelterbelt in hilly and mountainous areas of northern North China
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图 1 Before density adjustment
(Location: Midokou Township, Weichang County, Fengning City, Hebei Province, photographed: June 2017)
图 2 After density adjustment
(Location: Midokou Township, Weichang County, Fengning City, Hebei Province, photographed: June 2018)
表 1
Climate zones Temperate semi-arid zone, temperate sub-humid zone Average annual precipitation/mm 340-560mm Average annual evaporation/mm 1, 400~1, 900mm Average annual temperature/℃ □.9~6.2 C Maximum temperature/℃ 17~22℃ Minimum temperature/℃ -13~ -19 C Average annual wind speed/ m/s 3~5 m/s Note: Precipitation, evaporation, air temperature and wind speed in the table are average values over the 1980-2010 period. The climatic data were obtained from local national weather stations. 
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表 2 Basic information of the demonstration area
Province County Township Climate zones Longitude Latitude Elevation/m Hebei Province Weichang County Yudaokou Town Cold temperate continental monsoon climate 117°12'27.6″E 42°18'57.4″N 1230
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表 3 Topographical conditions
Elevation Topography Slope gradient Slope direction Slope position □ < 100 m ■ Flat lands ■ Flat (0-5%) □ Sunny □ Up □ 101-500 m □ Hillside □ Gentle (6-15%) □ Shady □ Middle □ 501-1, 000 m □ Hilly slopes □ Slope (16-25%) □ Half-sunny □ Down ■ 1, 001-1, 500 m □ Slopes □ Steep (26-35%) □ Half-shady ■ 1, 501-2, 000 m □ Valley floor □ 2, 001-2, 500 m □ Sand dunes □ 2501-3, 000 m ■ Flat sandy land □ Cultivated land that slopes gently
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表 4 Soil condition
Soil types Soil texture Effective soil layer thickness Organic matter content of surface soils Soil hardness Soil gravel content ■ Aeolian sandy soil ■ Sandy soil □ 0-20 cm □ High (> 3%) □High ■ Light gravelly soil (1-5%) □ Calcium chestnut soil ■ Sandy loamy soil □ 20-50 cm ■ Medium (1-3%) ■ Medium □ Medium gravelly soil (5-10%) □ Brown calcium soil □ Loamy soil □ 50-100 cm ■ Low (< 1%) ■ Low □ Gravelly soil (10-30%) □ Cinnamon soil □ Clay □ 100-200 cm □ Light gravel (30-50%) □ Saline-alkali soil ■ > 200 cm □ Medium gravel (50-70%) □ Others: □ Heavy gravel soil (> 70%)
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表 5 Vegetation status
Vegetation types Community coverage Vegetation degradation status ■ Planted forest: (Pinus sylvestris Plantation) □ < 5% □ Light □ Sandy vegetation: (what kind of community) ■ 5-15% □ Moderate □ Bush: (what kind of community) ■ 15-25% □ Severe □Grassland: (what kind of community) ■ 25-40% □ Artificial forest with dead treetops □Meadow: (what kind of community) □ > 40% □ Artificial forest with dead trees □Others:
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表 7 For specific technologies, please fill in the relevant information by selecting the technology category below.
Technological flow The main points of the technology Implementation time 1. Forest tree classification The trees are divided into target trees, auxiliary target trees and density-regulating trees with the proportions of 30%, 30% and 40%, respectively. The target trees are required to be strong, well branched, and evenly distributed to form the backbone of the stand; the auxiliary target trees are required to be young, strong and distributed among the target trees, preferably in the middle of two target trees, to complement and continue the ecological function of the target trees; the density- regulating trees regulate the permeability of the stand. 2. Classification of density-regulating trees Density-regulating trees are classified as Class I (dominant): large height, generally sticking out above the forest canopy; Class II (sub-dominant): slightly inferior to Class I, with a uniform and superior canopy; Class III (medium): medium growth, with the canopy below those of Classes I and II; Class IV (suppressed): backward growth, with the canopy squeezed; Class V (dying): extremely backward growth, completely under the canopy, with sparse branching or withered. 3. Management measures (1) Density-regulating trees that affect the target trees are to be felled, and auxiliary target trees that affect the target trees are to be eliminated by pruning and other measures. The management measures to the target trees are limited to pruning of dead branches and branches with severely reduced lower growth, felling of the dead, diseased and decayed wood, and functionally decayed stands.
(2) Density-regulating trees that affect the secondary target trees are to be felled. The management measures of the secondary target trees are limited to pruning, felling of the dead, diseased and decayed wood, and functionally declining stands.
(3) Adjust the number and shape of density-regulating trees according to the overall structural and functional requirements of the stand, with the principle of felling Class V and Class IV trees first and protecting Class I and Class II trees.
(4) From dense to sparse: harvesting intensity of stems ≤ 15%; space among stands < 3 times of the nutrient area per plant; average diameter at breast height of stand ≥ 6 cm, the number of plant per unit area after nurturing is not lower than the lower limit of the number of plants suitable for retention in the stand.
(5) From sparse to dense: when the gap between stands is > 3 times the nutrient area/plant, replanting should be carried out; replanting species can be chosen from lemon and larch, with a total proportion of < 30%.6 to 8 years after stand closure 4. Others The litters should be left in site, and shrubs and herbaceous should be protected; logging wood is collected by cart to avoid causing mechanical damage to the woodland. Schedules or annexes (where relevant technical parameters indicators are available, schedule or annex information may be added here).
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表 8
Labour costs 5625 RMB/ha Machinery costs 0 RMB/ha Cost of materials 3750 RMB/ha Water cost (if irrigation was required) 0 RMB/ha Total cost 9375 RMB/ha
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