Effects Of Microtopography On Soil Quality Of Quercus Acutissima Plantation In Stony Mountain

To explore the effects of microtopography on soil quality of Quercus acutissima plantation in stony mountains,we investigated soil physical,chemical and biological properties under different microtopography in a Q.acutissima forest and a Q.acutissima and P.thunbergii mixed forest in Haizhou District of Lianyungang City.Based on principal component analysis and correlation coefficient method,the minimum data set were established for soil quality evaluation.The objective of this project is to clarify the influence of microtopography on soil fertility and quality of Q.acutissima plantation and provide a theoretical basis for rational utilization of forest land resources and improvement of plantation quality.The main results are as follows:(1)Soil physical properties varied among different microtopography.Among five types of microtopography in the Q.acutissima forest,the shady convex slope had lowest soil bulk density,which was 1.19 g/cm~3.In Q.acutissima and P.thunbergii mixed forest,the shady convex slope land had lowest soil bulk density,which was 1.10 g/cm~3.Moreover,soil bulk density in the Q.acutissima forest was 20%,19%and 8%higher than that in the Q.acutissima and P.thunbergii mixed forest for gentle slope,shady concave slope and shady convex slope,respectively.For gentle slopes,sunny concave slope and shady convex slope,total porosity,capillary porosity and water content in mixed forests were higher than or at least equal to those of pure forests.In general,the soil physical properties of the Q.acutissima and P.thunbergii mixed forest were better than those of the Q.acutissima forest.(2)There were significant differences in soil chemical properties among different micro-topography.The soil chemical properties were better in the sunny convex slope of the Q.acutissima forest,and also in the shady concave slope of the Q.acutissima and P.thunbergii mixed forest.Among five types of microtopography in the Q.acutissima forest,the sunny concave slope had highest soil organic matter content,total nitrogen content and total potassium content;the depression micro-terrain had higher soil total phosphorus and alkali-hydrolyzable nitrogen content than the convex microterrain;and the sunny slope had higher soil potassium shady slopes.In the Q.acutissima and P.thunbergii mixed forest,the shady concave slope had highest soil organic matter,alkali-hydrolyzable nitrogen and available potassium contents,and two types of terrains in the shady slope had higher soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen and available potassium contents than other terrains.Comparing the two forest types,the content of total phosphorus and potassium in the Q.acutissima forest was higher,and the contents of carbon and nitrogen in the Q.acutissima and P.thunbergii mixed forest were higher.In general,the soil chemical properties of the mixed forest of Q.acutissima and P.thunbergii mixed forest were better than those of the pure forest.(3)There were significant differences in soil biological properties among different microtopography,and the soil biological properties in shady concave slope were the best in both forest types.Among the five types of microtopography in the Q.acutissima forest,the shady concave slope had highest soil microbial biomass carbon and nitrogen content,catalase,urease and acid phosphatase activities.In the Q.acutissima and P.thunbergii mixed forest,the shady concave slope had highest soil microbial biomass carbon and nitrogen content,catalase,invertase and acid phosphatase activities.Compared with the Q.acutissima forest,the soil microbial biomass carbon of the Q.acutissima and P.thunbergii mixed forest had higher soil microbial biomass carbon in shady convex slope,higher nitrogen content of soil microbial biomass and invertase activity in sunny concave slope,shady concave slope and shady convex slope,and higher(or similar)catalase and acid phosphatase activities in all five micro-terrains.In general,the soil biological properties of the mixed forest of the Q.acutissima and P.thunbergii mixed forest were better than those of the Q.acutissima forest.(4)Microtopography affected the understory soil quality index via its effects on 6 key soil indicators,i.e.soil pH,organic matter content,total phosphorus content,available phosphorus content,catalase activity and microbial biomass nitrogen content.The soil quality index in the five microtopography of the Q.acutissima forest ranged from 0.46 to 0.54,and the highest value appeared in the sunny concave slope.The soil quality index of the Q.acutissima and P.thunbergii mixed forest ranged from 0.48 to 0.59,and highest value appeared in the shady convex slope.The soil quality only in the microtopography of the sunny slope and depression was higher in the pure forest than that in the mixed forest.It may be due to fact that the mixed forest has good light source heterogeneity,moderate canopy closure,more difficult litter degradation,thicker humus,and stronger metabolic activity of soil microbial community than pure forest,and better soil physical properties and soil nutrient levels than pure forest.Therefore,the Q.acutissima and P.thunbergii mixed forest is more conducive to the improvement of soil quality.This suggested that further attention should be paid to the influence of topographic factors on soil quality in the future vegetation construction process.