Analysis On Protection Benefit Of Main Forest Types In Yudaokou Area

The winter wind and sand are frequent in Yudaokou pasture,and the climate is bad.The pasture is gradually degenerated and desertified.The construction of sand-fixing forest has effectively prevented wind and sand,and obviously improved the local ecological environment.In order to explore the law of protection benefit of typical forests in Bashang area of Chengde,the shelterbelt of Larix principis-rupprechtii.and four types of protection forests(I pure forest of Pinus sylvestris var.mongolica,II pure forest of Larix principis-rupprechtii,III mixed forest of Pinus sylvestris var.mongolica and Larix principis-rupprechtii and IV mixed forest of Pinus sylvestris var.mongolica and Ulmus pumila)on Yudaokou pasture were taken as the research objects,and the way combining with field investigation,indoor test and wind tunnel test were used to study the windbreak effect of the Larix principis-rupprechtii shelterbelt and the microclimate benefits and soil improvement benefits of the four different shelters.The main conclusions were as follows:1)The Shelterbelt of Larix gmelinii has obvious wind-proof regularity.In the horizontal direction,the minimum wind speed appeared at 1H after the belt,and the windproof efficiency was most,but with the increase of horizontal distance,the wind speed gradually increased and the windproof efficiency gradually decreased,and after 10 H,the trend slowed down.The wind speed reduction area formed in the range of 1H to 10 H on the leeward side of the forest belt was the main protected area and the action scope of the forest belt.The reduction range of wind speed in 1H-10 H region was 15%-55%,in 10H~15H region,the wind speed decreases by 8%~15%,but in 15H-20 H region,the reduction of wind speed was relatively small,about 2%-8%.Until 20 H after the forest,the wind speed basically restored to the level of the wind speed in the wilderness,and its windbreak efficiency was only 2.16%.In the vertical direction,the trend of windproof efficiency of after the pasture shelter forest was 0.3 m >0.5 m>1 m>2 m,and the distribution of wind speed is opposite to that of windbreak efficiency,which was 0.3 m<0.5 m<1 m<2 m.2)Four different shelter forests had obvious effects of cooling and increasing humidity and the law of cooling and increasing humidity was consistent,that was IV > III > I > II.The daily variation trends of air temperature and relative humidity of air at different heights(0.3m,1m and 2m)in each forest were basically the same.The daily variation of temperature first showed an upward trend,reaching its maximum at 14:00,and then gradually decreasing,but the air temperature at 18:00 was still higher than at 8:00.While the daily variation trend of relative humidity of air and air temperature was opposite,that was,it first showed a downward trend,reaching a minimum at 14:00,and then gradually increased,but the relative humidity of air at 18:00 was still lower than at 8:00.In vertical height,the air temperature in each forest was 0.3m < 1m < 2m,while the relative humidity of air showed the opposite change rule,that was,0.3m > 1m > 2m.3)Four different shelter forests had obvious soil improvement effects on soil texture and physical and chemical properties,but the improvement effects of each forest were different,and the improvement of topsoil was the most significant.In 0-10 cm,10-20 cm and 20-40 cm soil layers,the I and II forests were loam sandy soil,and they were sandy soil in the soil layers of 40-60 cm,but the whole was loam sandy soil.In 0-10 cm and 10-20 cm soil layers,the III forest was sandy loam soil,and in 20-40 cm and 40-60 cm soil layers,it was loam sandy soil,but the overall was sandy loam.The each soil layer of the IV forest was all sandy loam,and the whole was also presented as sandy loam.Generally speaking,the improvement of soil texture is the best of IV forest,the third forest is second,and the I and II stands are worse.Different protective forests had obvious improvement effects on soil physical and chemical properties,but the improvement of surface soil is the most significant.Compared with CK,the rules of each nutrient index in each forest were consistent,which showed as follows: IV > III > I > II,the soil bulk density was expressed as: II>I>III>IV,and the soil pH was expressed as: IV>II>I>III.But with the deepening of soil depth,the physical and chemical properties showed certain regularity,and the difference between soil layers decreased.4)There were obvious correlations among the factors of soil physical and chemical properties.There was a extremely significant positive correlation between soil particle size <0.25 mm and soil organic matter,total nitrogen,alkali nitrogen and available potassium,and a significant positive correlation with soil total phosphorus,total potassium and available phosphorus.Soil bulk density was significantly negatively correlated with total phosphorus,total potassium,alkali nitrogen,available phosphorus and available potassium.Soil organic matter was significantly positively correlated with total nitrogen,total potassium,alkali nitrogen and available potassium,and positively correlated with total phosphorus and available phosphorus,but did not reach significant levels.There was no significant correlation between soil pH and other factors.