The Water Conservation Capacity Of Major Plantations In Northern Mountain Area Of Hebei Province

In order to protect the upstream water source of Beijing and improve the eff-iciency of water conservation,beginning in 2009,Beijing cooperates with Hebei Province to start the construction project of ecological water resources protection forest.Selection of plantation stands with strong water conservation capacity in afforestation will be more in line with the objectives of conservation forest construction,and it is also very important for the eco-hydrological function of the upstream catchment area.In order to select the plantation stands with better water conservation capacity,6 main plantations in mountainous areas of northern Hebei Province were divided into research objects,through field investigation,sampling and laboratory experiments,the characteristics of vegetation,litter and soil were studied and compared.Finally,the plantations with better water conservation capacity was evaluated and selected through subjective and objective comprehensive weight method,in order to provide theoretical basis for local artificial forest construction and clear direction for the artificial forest transformation work in this area.The main conclusions of this study are as follows:(1)There are 19 species,18 genera and 11 species in the Pinus tabulaeformis pure forest,which is the largest variety of all plantations.Carex lanceolata Boott,Selaginella tamariscina(P.Beam)Spring and Vitex negundo L.var.heterophylla(Franck)Rend.are dominant species of understory herbaceous plants and shrubs.The diversity index of understory herbs was higher than that of understory shrubs,among them,The Pinus tabulaeformis x Armeniaca sibirica mixed forest and the Larix gmelinii x Armeniaca sibirica mixed forest are the largest herbaceous and shrub diversity indices.(2)The litter thickness of each plantation ranged from 3.90 mm to 9.10 mm,and the litter volume ranged from 1.23 t/hm2 to 2.68 t/hm2.The thickness,volume and water holding capacity of undecomposed litter layer in each plantation were larger than those of semi-decomposed litter layer.The water holding capacity of litter is a dynamic process that satisfies the correlation function,and the water holding process can be divided into three stages.Water holding capacity of litter mainly depends on the volume and water holdup,and the maximum water holding capacity and effective interception capacity of litter in the Populus pure forest are the largest,5.50 t/hm2 and 4.48 t/hm2,respectively.(3)The infiltration characteristics were negatively correlated with soil bulk density and clay,and positively correlated with total porosity,non-capillary porosity,sand and organic matter.The principal component equation X,which characterizes the infiltration capacity of soil,and the principal component equation Y,which characterizes the physical and chemical properties of soil,X and Y satisfies the quadratic function.The soil infiltration ability of tabuliformis x Armeniaca sibirica mixed forest is the strongest.Kostiakov formula is more suitable for describing the infiltration process of plantation lands in this study area.The maximum soil water holding capacity of Pinus tabuliformis x Armeniaca sibirica mixed forest is 877.93 t/hm2,and the effective water holding capacity is 160.47 t/hm2,which is the largest among all plantations.(4)Soil layer plays an important role in water conservation capacity of plantations.The score of water conservation ability of plantations from high to low is the tabuliformis x Armeniaca sibirica mixed forest(0.1843),the Larix gmelinii × Armeniaca sibirica mixed forest(0.1694),the Pinus tabulaeformis pure forest(0.1677),the Platycladus orientalis x Armeniaca sibirica mixed forest(0.1649),the Populus pure forest(0.1552),the tabuliformis × Larix gmelinii mixed forest 0.1474).The Pinus tabuliformis ×Armeniaca sibirica mixed forest can be selected on the sunny slope of mountain area,and the Larix gmelinii x Armeniaca sibirica mixed forest can be selected on the shady slope of mountain area.