Ecological Effects Of Mixed Forests With Different Age In Saline Land In Yellow River Delta

Yellow River Delta has special geographical location and environmental conditions,it is also an important objective of the "Twelve-Five" plan for the development of national and local governments.But the soil salinization of this area is very high,and the ecological environments are relatively fragile.So it is a difficult task to create a good environment for the economic development of the region.One of the important measure to improve the ecological environment in this region is to construct mixed forest.In this study,taking the mixed forests with different age in Haikou county in Yellow River as the objects,we studied the effects of mixed forests with different age on the improvement of the microclimates The following is the main research results of this study:(1)The illuminations inside and outside the mixed forest with 2 year old were almost the same.The illuminations inside and outside the mixed forest with 8 year old and 27 year old were quite different.The difference of illuminations inside and outside the mixed forests with 8 year old were smaller than that of the mixed forest with 27 year old;The temperatures inside and outside mixed forests with 2 years old and 8 years old the temperature were no significant difference.The temperature inside mixed forest with 27 year old was lower than that outside by nearly 1 degrees,which meant the mixed forests with elder age played a greater role in reducing the temperature.The mixed forest with 2 year old had little change in air humidity between inside and outside.The humidity inside the mixed forests increased with the addition of age;the soil temperatures inside the 3 kinds of mixed forest with different age in soil surface,10cm and 20cm layers were all smaller than that outside.With the increase of tree age,mixed forest in the soil surface temperature,the soil temperatures inside the 3 kinds of mixed forest with different age in soil surface,10cm and 20cm layers gradually decreased.Soil temperature and soil 10cm 20cm temperature gradually reduced.The soil surface temperature inside and outside the mixed forests had larger difference and he soil temperature in 10cm and 20cm layer had smaller,which showed the mixed forests had greater influence on the surface soil temperature than that in deeper soil.(2)The mixed forest with 2 years old had small effect on windproof.The mixed forests with 8 years old had better effect on windproof.The wind velocities inside and outside the mixed forests were quite different and had best windbreak effect on the leeward side of 1H tree height.The mixed forest with 27 years old had very difference in wind velocity outside and inside the mixed forests.It also had best windbreak effect on the leeward side of 1H tree height.The windbreak effect 1H tree height is best,27 year old mixed forest wind speed reduction effect is obvious.A dropping wind zones were formed in the area of 1H to 15H of tree height.When the horizontal distance was more than 20H of tree height,the wind velocity rose again.(3)Evaporation inside and outside the mixed forest with 2 years old were almost the same,while evaporation inside and outside the mixed forests with 8 years old and 27 years were quite different.The older mixed forest had larger effect on reducing potential evaporation.With the addition of age,the evaporation inside the mixed forests reduced.The mixed forest with younger age had smaller influence on evaporation area,while the mixed forests with old age had larger influences in the leeward of 1H tree height.With the increase of the distance from the mixed forest,the influence of the mixed forests on evaporation gradually decreased.(4)The characteristics of mixed forests such as crown canopy,canopy density,average DBH,and tree height have positive relations with those factors like illumination,air temperature,soil temperature,wind velocity,potential evaporation.