| The water resources are short of water,and there is less precipitation and uneven distribution in the Taihang Mountain area.The function of water conservation plays an important role in regulating droughts and floods in the region.Therefore,6 forest stands of the typical ecological and economic protection forests of Malus pumila forest,Castanea mollissima forest and ecological protection forest Quercus variabilis forest,Robinia pseudoacacia forest,Pinus tabuliformis forest,shrub forest in low mountain area of Taihang Mountain were selected as research objects.The water conservation function was evaluated by the principal component analysis of the indicators of plant diversity under the forest,the hydrological effect of the litter layer,the hydrological effect of the soil layer,and the surface runoff of the soil layer.The evaluation results can provide technical support for the construction of vegetation types in the Taihang Mountains.The main findings are as follows:(1)From the standpoint of undergrowth plant diversity,it was found that there were 40 undergrowth plants,belonging to 23 families and 27 genera,including 12species and 12 genera of shrubs,and 28 species,25 species of 14 families.Among the shrub layers,Lespedeza bicol and Vitex negundo appeared in all stands except for Malus pumila forest and Castanea mollissima forest,and were dominant populations in the herb layer,the dominant status of Selaginella sinensis,Cleistogenes caespitosa,and Carex rigescens was obvious.The shrub layer diversity index of each stand was as follows:Robinia pseudoacacia forest>Pinus tabuliformis forest>Quercus variabilis forest>shrub forest,and the herb layer diversity index was Malus pumila forest>shrub forest>Castanea mollissima forest>Quercus variabilis forest>Pinus tabuliformis forest>Robinia pseudoacacia forest.(2)The total reserves of litter in each stand ranged from 5.35 t/hm~2 to 24.64t/hm~2,and the litter accumulation under the forest was represented by Pinus tabulaeformis forest(24.64t/hm~2)>Quercus variabilis forest(16.62t/hm~2)>Castanea mollissima forest(10.52t/hm~2)>Robinia pseudoacacia forest(7.29t/hm~2)>shrub forest(6.28t/hm~2)>Malus pumila forest(5.35t/hm~2).Except for the Malus pumila forest,the amount of the semi-decomposed layer of litter in each stand was greater than that of the non-decomposed layer.The maximum water holding capacity of litter layer in each forest varied within the range of 9.56t/hm~2~38.94t/hm~2,and the litter storage capacity of each stand was in the range of 7.46t/hm~2 to 19.14t/hm~2.The maximum water holding capacity and the effective storage capacity of Pinus tabulaeformis forest are the greatest,and the ability of the shrub forest to hold water is the weakest.Through regression analysis,the relationship between the water holding capacity at different layers of the forest litter and the soaking time was analyzed,and the relational formula was:Q=aln(t)+b.The water absorption rate and immersion time of the litter of each stand were fitted and analyzed.The relationship was:V=kt~n.(3)The mean values of soil bulk density of each stand were shrub forest(1.41g/cm~3)>Pinus tabulaeformis forest(1.39g/cm~3)>Malus pumila forest(1.38g/cm~3)>Castanea mollissima forest(1.36g/cm~3)>Robinia pseudoacacia forest(1.34g/cm~3)>Quercus variabilis forest(1.31g/cm~3).The average soil total porosity varied from 38.49%to 47.26%in each stand,which was the highest total porosity in the Malus pumila forest and the smallest in the shrub forest.The maximum water holding capacity of each stand in the forest showed that the water holding capacity of Malus pumila forest was the strongest,being 472.60t/hm~2,and the shrub forest was the weakest,being 384.90t/hm~2.The average water holding capacity of different stand types showed that the water holding capacity of Malus pumila forest was the strongest,which was 137.27t/hm~2,and the shrub forest was the smallest,being 105.83t/hm~2.There was a positive correlation between the size of non-capillary porosity and the effective water holding capacity of the forest.(4)With the increase of rainfall,the variation of runoff with shrub forest was the largest,and it appeared in July when the rainfall was relatively large.The flow of other forests fluctuate more gently.The order of runoff of each stand was shrub forest(10.6mm)>Robinia pseudoacacia forest(3.56mm)>Quercus variabilis forest(3.00mm)>Pinus tabulaeformis forest(2.98mm)>Malus pumila forest(2.54mm)>Castanea mollissima forest(2.35mm).The runoff coefficient is the highest in the shrub forest,which is 8.45%,and the Castanea mollissima forest is the smallest,2.03%.Different cover treatments were conducted on the surface of Malus pumila forest and Castanea mollissima forest.Cover materials increased soil moisture and slowed surface runoff.During the whole investigation period,the water retention effect of water contained in the grass cover was the most significant,and the soil moisture content under different cover showed Grass Curtain>Grass>Clearing>Ground Cloth.(5)Through the principal component analysis comprehensive evaluation on the main water conservation indicators of each stand type,the comprehensive scores were ranked as follows:Castanea mollissima forest(1.964)>Malus pumila forest(1.048)>Pinus tabulaeformis forest(0.893)>Quercus variabilis forest(0.307)>shrub forest(-2.173)>Robinia pseudoacacia forest(-2.479). |
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