| Cunningmia lanceolata is one of the main timber species in southern China,but during the past 20 years,we can find that long-term operating Cunningmia lanceolata had made the forest ecological fragile and sensitive.This paper mainly studied the variation characteristics of soil indicators of the Cunningmia lanceolata and the mixed plantation including Cunningmia lanceolata and Taxus chinensis.We select 3 kinds of mixed plantation which are different planting years of Taxus chinensis mixed with the Cunninghamia lanceolata as the research object,which named 2005 mixed plantation,2006 mixed plantation and 2007 mixed plantation respectively.At the same time,Bying the methods of surveying and sampling the sample plot to proceed soil sampling investigation for each of these three kinds of forest we choose the same year of Cunninghamia lanceolata as a reference to study soil physical-chemical properties and enzyme activity of the mixed plantation in the horizontal and vertical changes of characteristics.The main results are as follows:1 The soil test results of physical-chemical properties from different slope aspects of mixed plantation consists of the Taxus chinensis and Cunninghamia lanceolata indicated that:the bulk density of Yin slope aspect were higher than the value of Yang slope aspect.At the same time,we can knew from the significant difference between the porosity of Yin and Yang slope aspect that one of the important factors to influence the soil porosity was slope aspect;there was not a significant difference on water holding capacity between different slope direction of mixed plantation,so slope direction was not important factor to change the condition of soil moisture physical.The significant difference value of soil organic matter,total phosphorus,total nitrogen and phosphorus in different slope direction of mixed forest in 2006 were 0.00,0.00,0.009,0.012 respectively;the significant difference value of the total potassium in different slope direction of mixed forest both of in 2005 and 2007 were 0.00;the significant difference value of the total phosphorus,total potassium and rapidly-available potassium in different slope direction of the pure forest were 0.016,0.00,0.017 respectively.The rest of nutrient element indexes of these four kinds of forests not had obvious difference between Yin and Yang slope direction.The results showed that the slope direction was not the main cause for the change of soil nutrients elements.2 The soil test results on different age of mixed plantation consists of the Taxus chinensis and Cunninghamia lanceolata indicated that:the experimental date show that with the increase of mixed planting' s age,the change of chemical and physical properties of soil reflected the basic trend to downward after rising.The data of the 2006 mixed planting covering the capillary porosity,the maximum water-holding capacity,the least water-holding capacity,the capillary water holding capacity,the organic matter,the total nitrogen,the total phosphorus and hydrolysis nitrogen which content were all higher than mixed forest in 2007 and in 2005.While only the content of soil bulk density,total porosity,capillary pore,total potassium,available potassium were lower than mixed forest in 2007 and in 2005.At the same time,with the increase of the mixed forest age,the activity of soil urease and invertase were decreased,while with increasing years of planting,the activity of phosphatase was going down after growing first.n summary,the Soil texture of mixed forests in 2006 are higher than in 2005 and in 2007.3 The research of soil chemical properties about the mixed forest and the pure forest indicated that all of the soil organic matter,total nitrogen,total phosphorus and total potassium of the mixed plantation and the pure forest had extremely significant even significant differences,the difference values were 0.018,0.00,0.005 respectively,while there were no significant differences about the effective phosphorus,hydrolysis nitrogen and available potassium in the soil.Research showed that most of the nutrition indexes of mixed forest were lower than the pure forest's,and indicated that mixture plantation was more need to strengthen the management of fertilization.4 Activity of different slope direction soil enzyme from Cunninghamia lanceolata and Taxus chinensis mixed forest showed that:The soil urease activity of Yang slope direction was greater the Yin slope direction' s,the invertase activity of Yin slope direction was lower than Yang slope direction' s,while the phosphatase activity of Yang slope direction was higher than Yin slope direction' s as a whole;the research of enzymatic activity between the pure forest and the mixed forest indicated that there was not obvious difference about urease,and the invertase activity of the mixed forest was higher than the pure forest' s,while the phosphatase activity appeared the opposite trend.The strength of the enzyme activity may have close relationship with its roots.5 The vertical distribution analysis on soil physical-chemical properties of the study site showed that,the soil bulk density increased along the soil profile,this may attributed to the function of roots from Cunninghamia lanceolata and Taxus chinensis;the porosity changed significantly,which showed that soil depth deeply influenced porosity;the maximum water holding capacity,minimum water holding capacity and capillary water holding capacity decreased with the increasing soil depth,so the soil organic matter,total nitrogen,soluble nitrogen and rapidly available K.total P increased and then decreased both in 0-40 cm and 40-60 cm,while available P showed the trend along the whole soil profile.6 The vertical distribution analysis on soil enzyme activity of the study site showed that,With the soil layer increasing,the activity of invertase showed a downward trend;the activity of urease was decreased in 0-40cm,but firstly increased and then decreased in 40-50 cm and 50-60 cm;the activity of phosphatase showed a downward trend as a whole,while the mixed forest in 2006 is firstly increased and then decreased in 30-40 cm and 40-50 cm,the mixed forest in 2007 was firstly increased and then decreased in 0-20 cm and 20-50 cm,the mixed forest in 2005 showed a falling trend as a whole.We can know from these data that with the soil layer increasing,three kinds of enzyme activity all showed a trend of decline. |
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