| Four stand types were selected in the Tangjiapu experimental forest area in Changde city,Hunan Province: young oil-tea camellia×gardenia stand,young oil-tea camellia ×old oil-tea camellia× gardenia stand,old oil-tea monocropping stand and young oil-tea camellia monocropping stand.Soil samples were collected outdoors and soil quality was analyzed indoors.Soil physical and chemical properties,mineral element content and correlation among four stand types of camellia oleifera plantations were determined respectively in different soil layers(0-20 cm,20-40 cm,40-60 cm)and different slopes(hill bottom,hillside and hilltop).The results showed that:(1)There are some differences in soil physical properties of the four stand types,and the total soil porosity decreases with the increase of soil layer and slope.The soil moisture content and bulk density increased gradually,but did not reach significant differences in the surface layer and 40-60 cm soil layer.With the increase of soil layer,the maximum field capacity decreases first and then increases and reaches a maximum in the 40-60 cm soil layer.The young camellia-gardenia stand model significantly increased the maximum field water capacity in the soil layer of 20-40 cm and 40-60 cm.p H value ranged from 2.12 to5.13,which is acidic soil,and increases gradually with the deepening of soil layer and slope.Compared with the other three stand types,the young camellia-gardenia stand model significantly improved soil physical properties in soil bulk density,total soil porosity,moisture content and maximum field capacity.The young oil-tea×old oil-tea×gardenia stand model can also improve the above physical indicators,although the effect is not as good as the young oil-tea×gardenia stand model.And the effect of young oil tea is better than that of young camellia oleifera×old camellia×gardenia stand model.(2)The chemical properties of different stand types were also significantly different.The four stand types all are gradually decreasing with the increase of soil layer and slope,and the contents of organic carbon,organic matter,ammonium nitrogen and available potassium.In terms of soil layer,there are significant differences between the surface layer of these chemical indicators and the 40-60 cm soil layer.Nitrate nitrogen decreases gradually with the increase of soil layer,and increases gradually with the increase of slope in the planting system containing new oil-tea(new oil-tea-gardenia stand model and new oil-tea-monoculture model).However,the available phosphorus in the soil,including the planting system of old oil tea(new oil tea-old oil tea-gardenia stand model,old oil tea monocultural model),increases gradually with the slope.The new oil-tea--old oil-tea--gardenia stand model and the new oil-tea--gardenia stand model can improve the soil layer of 40-60 cm.Compared with other two kinds of forest stand,the new differential-old-gardenia forest model,and a new differential-gardenia stand model significantly increased the soil organic matter,organic carbon,nitrate nitrogen,ammonium nitrogen,but in terms of available k,effective phosphorus,although is a best new camellia-gardenia stand,but the old oil-tea soil available potassium,effective phosphorus content was significantly higher than the new differential-old camellia-gardenia stand model content.The correlation shows that there were antagonistic effects between different elements in camellia oleifera soil,such as Fe and Mg,Ca were significantly or negatively correlated(p < 0.01,P < 0.05),and there were also interactions such as Na,Mg,Ca,which were significantly or positively correlated(p < 0.01,P < 0.05).The soil nutrients of camellia oleifera were also positively correlated with the elements in the soil.The organic matter,organic carbon,available phosphorus and available potassium in the soil were significantly or positively correlated with Na and Mg respectively(p < 0.01,P < 0.05).(3)There are also significant differences in soil mineral elements among the four stand types.With the increase of soil layer and slope,Mg,Al and Na in the soil decreased gradually,and significant differences were achieved in surface layer and40-60 cm soil layer.The content of Ca,Fe,decreased with the increase of slope.In terms of soil layer,the new oil-tea--gardenia stand model,new oil-tea--old oil-tea--gardenia stand model decreased with the increase of soil layer no matter at the bottom of the mountain,the hillside or the top of the mountain,while the content of new oil-tea monoculture model and old oil-tea monoculture model decreased first and then increased.Among the four stand types,the best stand model for improving mineral elements of Mg,Al,Ca and Fe is the new oil-tea-gardenia stand model,followed by the new oil-tea-old oil-tea-gardenia stand model.Only in terms of Na content,although it is still the new oil tea--gardenia stand model,the effect is the best.However,the monoculture effect of old oil tea was greater than that of new oil tea--old oil tea--gardenia stand.The correlation indicated that there were antagonistic effects between different elements in camellia oleifera soil,such as Fe,Mg and Ca were significantly or negatively correlated(p < 0.01,P < 0.05).There are also interactions,such as Na,Mg and Ca,which are highly significant or significantly positive correlated(p<0.01,p<0.05).Soil nutrients are also significantly positively correlated with elements.Soil organic matter,organic carbon,available phosphorus and available potassium were significantly or positively correlated with Na and Mg respectively(p<0.01,p<0.05).(4)According to the analysis of soil mineral elements,physical properties and chemical properties,the comprehensive effect of fuzzy membership function analysis was ranked as follows: old oil tea monoculture model < new oil tea monoculture model < old oil tea-new oil tea-gardenia stand model < new oil tea-gardenia stand model. |
