Study On The Relationship Between Soil Enzyme Activities And Soil Nutrients Of Casuarina Equisetifolia And Slash Pine In Costal Sandy Area

Soil enzyme,the most active biological substances in the process of ecosystem material circulation and energy flow,reflects the metabolic cycle dynamics of soil nutrients to a certain extent,which can directly reflect the status of material transformation in the soil.This experiment is based on the theoretical basis of the soil enzymology.We regard soil enzyme activity and soil nutrient content as a whole to study the soil environment of the Casuarina equisetifolia,and connecting with the Slash Pine done related research and comparison.By studying the different growing period' s(casuarina 10 a,23 a,33 a,wetland pine 15 a,23 a,34 a)stand soil nutrient content,soil enzyme activity(urease,invertase and acid phosphatase,catalas and polyphenol oxidase),reveals the influence on soil ecological environment of Casuarina equisetifolia and Slash Pine in the process of growth.Correlation analysis on soil enzyme activity and main chemical properties of soil showed that soil enzyme activity plays an important role in soil fertility and soil quality evaluation.The findings are as follows:1.Soil enzyme activity is very sensitive to environmental changes.Soil enzyme research results achieved by different measurement methods are lack of comparability,so standardization of soil enzyme activity measurement method is imperative.The enzyme activity values measured with the mixed wet soil can better reflect its actual size,and air-dried soil activity determination result is low.The under drop of the enzyme activity measured in the soil drying condition is:80.28%of the urease,41.41%of the invertase,71.81%of the phosphatase and 31.71%of the polyphenol oxidase.The soil enzyme incubation time is appropriately for urease 24h,the invertase 24h,the phosphatase 24h,the polyphenol oxidase 2h.2.The distribution in the soil profile studies on soil enzymes show that most of soil enzymes has obviousvertical distribution characteristics.Urease,invertase and acid phosphatase activity values of Casuarina equisetifolia and Slash Pine decrease with soil depth,especially topsoil or subsoil decline most obvious.Among them,a larger decline in Casuarina equisetifolia surface soil invertase(57.15%)and the Slash Pine subsoil acid phosphatase(59.68%).Catalase and polyphenol oxidase overall trend was enhanced with soil depth.Its activity value significantly increase between 0 to 10 cm and 10 to 20 cm soil.In Casuarina equisetifolia forest and Slash Pine forest,total soil elements(total nitrogen,total phosphorus,total potassium)and effective element(hydrolysis nitrogen,phosphorus,available potassium)content decrease with increasing depth of the soil.It shows 0?10cm>10?20cm>20?30cm>30?40cm.The most obvious decline is total nitrogen(casuarina 82%,the slash pine 83.33%)and the minimum change is total potassium.The soil pH value increases gradually for slight easing of soil acidic.As the soil depth increasing,microbial activity reducer and the number of nutrient supply fewer.Therefore,in addition to the total potassium,avaible potassium,pH value,the rest of the index value in the soil differences are very significant.3.Choose 10a,20a and 33a Casuarina equisetifolia to study the change of soil enzyme activity at its different plant ages and analyze the difference and significance of the soil enzyme activity value.The difference of forest land's soil acid phosphataese and polyphenol oxidase activity value is not significant,though the plant ages are different.When it is 23 years old,there are significant difference with other years in Urease,Invertase,Catalase.Five kinds of soil enzymes activity value reach the peak when the plants are 23 years old,also do the content of Organic Matter,Total N,Hydrolytic N.The element content and pH value of other nutrient decline with Casuarina equisetifolia's plant age increase.4.15 years Slash Pine forest land's soil urease,Invertase,Acid phosphataese,Catalase activity value is bigger than 23 years' and 34 years' is smaller than 23 years'.Polyphenol oxidase activity value is the biggest when it is 23 years old.The Catalase activity value is quite different with other ages when it is 15,while the other 4 have great changes when it is 34.Slash Pine forest soil Organic Matter and Total N content are the biggest when it is 23,while other nutrient element declines with the plant age increase.5.The changes of Hydrolytic enzyme activity value in one year are as below:Urease from 0.00816 to 0.05429mg/g,Invertase from 0.857 to 1.449mg/g,Acid phosphataese from 0.598 to 1.017mg/g.Except that soil Polyphenol oxidase activity value is a litter lower in summer when the plants grow quickly,Urease,Invertase,Acid phosphataese's value changes almost the same as plant growth cycle,which means it is the higgest in summer,lower in spring and autum,the lowest in winter.Catalase activity value is 2.231.17ml/g,the biggest when it is in spring,after spring it declines and to be the lowest,that is 1.17ml/g in winter.To the contrary,Polyphenol oxidase activity value is 0.173mg/g,the lowest in summer and 0.225mg/g,the higgest in winter.Due to the small range of temperature the whole year in Changle and the condition of Casuarina equisetifolia living in costal areas,the range of soil enzyme activity value is small in different seasons except that for Urease's value there is a big decline in autum and winter.6.Compare the soil nutrient and enzymes between Casuarina equisetifolia and Slash Pine pure forest who have almost the same plant age.The content of all nutrient elements in Casuarina equisetifolia are a little bigger than in Slash Pine at the same age,that is to say 23 year old Casuarina equisetifolia nutrient content is larger than Slash Pine's and 33 years old Casuarina equisetifolia latger than 34 years old Slash pine.There are Nitrogen-fixing Rhizobium in the roots of Casuarina equisetifolia,so its urease avtivity value is much bigger than Slash Pine forest's.So are invertase,acid phosphataese,catalase and polyphenol oxidase.So Casuarina equisetifolia is more suitable to grow in costal sand land than Slash Pine.7.The result of correlation analysis between soil enzymes and nutrient shows that except catalase,there are some relation between other enzymes and organic matter,N,P and K.Specially,there are close relation between organic matter content and enzyme activity,which have positive correlation with urease,invertase and acid phosphataese.The correlation values are 0.877**,0.943**and 0.818**in Casuarina equisetifolia.Slash Pine' s are 0.895**,0.970**and 0.967**.By multivariate regression analysis and building the regression equation of soil enzymes and nutrient,we can find that organic matter,total N,total P and total K have significant influence on 5 kinds of soil enzyme activity.So they are good index to expect enzymes activity.Besides,there are close correlation between soil enzymes.There are positive correlations among urease,invertase and acid phosphataese activity value,that is 0.903**,0.740**and 0.833**in Casuarina equisetifolia.Slash Pine' s are 0.952**,0.883**and 0.952**.From this we can know,there are interaction between certain enzymes and jointly promote the circulation and transformation of an element.As the evaluation index of soil fertility,single soil enzyme activity value doesn' t have good feasibility.So it is better to use the enzymes who have some certain correlations.