Effect Of Super Absorbent Polymers On Forestation In Gneiss Rocky Mountainous Area Of North China

Water is a limiting factor for revegegation in gneiss rocky mountainous area of north China.It is key for revegegation there to take effective dought-resistance measures of forestaton and to increase water utilization efficiency.The application of Super Absorbent Polymers(SAP) is an important technology to hold water and fight drought.Ailanthus altissima,Prunus sibirica and Quercus variabilis were selected as trial species.Through indoor laboratory,potted plant and forestation in gneiss rocky mountainous area,the water absorption and holding-water capability were studied.By systematically analyzing the effects of SAP on the soil water-physical properties,forest growth and eco-physiological and photosynthetic characteristics and demonstrating the influence of SAP on forestation,we can decide the suitable type and dosage of SAP to local nature condition,and provide the scientific foundation for the application of it on forestation.The results were as follows:(1) The water absorption capacity of SAP was negative correlation with the ion concentration in the solution.The water absorption and velocity capacity of small grain SAP were more higher than big grain SAP.the second water absorption capacity was declined more or less.With concentrations of SAP increasing,the soil bulk density and soil water evaporation velocity declined.Though soil maximum hygroscopic water and the wilting coefficient tend to increase as dosages of SAP increased,the amplitude was low,so the soil available water capacity augmented obviously.(2) Results showed that soil water content was always higher and declined slower than control experiment after applying SAP.Application of SAP can improve growth and chlorophyllous content and affect photosynthesis rate,transpiration rate and stomatal conductance of Ailanthus altissima and Prunus sibirica length and numbers of roots,biomass and root hat ratio of Ailanthus altissima and Prunus sibirica were higher than that of CK,but the growth of collar diameter between the treated and CK were not different from each other remarkably.(3) Results showed that soil water content and forestation survival rate of Ailanthus altissima and Quercus variabilis after applying SAP of different dosages,but the growth of collar diameter and height between the treated and CK were not different from each other remarkably.The soil water content and forestation survival rate of 30g per tree were highest and CK was lowest.In range 0～30g,the soil water content increased with dosage of SAP increasing,while the dosage exceed 30g per tree,the soil water content decreased instead.Additionally,Application of water-retaining agent could improve water utilization rate through impacting on the daily rhythm of photosynthesis rate and transpiration rate.Considering forestation cost and the survival rate,30g per tree was an ideal dosage for Ailanthus altissima in gneiss rocky mountainous area.