Roots And Soil Properties Under Caragana Intermedia Plantations In Alpine Sandy Land

The Gonghe Basin is located in an Alpine and arid region,where desertification is extremely serious.In order to further control desertification,the Caragana intermedia plantations has been planted in large areas.The Caragana intermedia plantations have an important impact on local vegetation restoration and soil improvement with the increase of plantations age.Took C.intermedia plantations of 3 years,5 years,10 years,16 years and 30years old as the research object near the Sand Control Experimental Station of Qinghai Province,so as to reveal the distribution characteristics and turnover rate of the C.intermedia plantations in different plantations age.Take moving sand dunes as control,the soil bulk density,organic matter,and nutrient contents such as nitrogen,phosphorus,and potassium were measured,so as to reveal their changes with the age of stands.The key research results are as follows:?1?The roots length,surface area and biomass of fine roots,medium roots and coarse roots increased with age and decreased with the deepening of soil layer.According to the overall analysis,60%of the roots of C.intermedia plantations were distributed in the soil layer of 0?40 cm,and 22%of the roots were distributed in the shallow soil layer of 40?60 cm,and18%of the roots were distributed in the soil layer of 60?80 cm.Roots of all ages plantations are suitable for absorbing shallow soil moisture that supplemented by rainfall.The roots of C.intermedia plantations continuously extends to the deep soil with the increase of plantations age.However,due to the precipitation is intercepted and absorbed by the shallow roots,resulting in the deep soil become more and more dry.The roots is unable to get the the required water for growth in the deep layer,and then it will be distributed to the shallow layer,indicating that the roots of the C.intermedia plantations grow gradually become shallow,adapting to the Alpine and dry environment environment with a shallow distribution strategy.?2?The fine root biomass showed obvious characteristics of vertical distribution and seasonal dynamic variation.About 41%of the living roots and 39%of the dead roots are distributed in the 0?20 cm soil layer,38%of the living roots and dead roots are distributed in the soil layer of 20?40 cm,21%of the living roots and 23%of the dead roots are distributed in the soil layer of 40?60 cm.The peak of living fine roots biomass appeared in June and August or June and September,and reached the maximum in August or September,the peak of dead fine roots biomass Appeared in August and September,and also reached the maximum in August or September.The net productivity of C.intermedia plantations in different plantations age was 37.31,54.54,65.38,102.89,and 147.61 g?m^-2?a^-1,the turnover rates was 0.53,0.66,0.56,0.73 and 0.78 times?a^-1,the annual mortality was 6.58,7.60,14.54,27.91,38.62 g?m^-2?a^-1.The net productivity,annual mortality and turnover rate of fine roots increased with the increase of plantation age,the turnover rate decreased with the deepening of the soil layer.?3?Compared to the soil of the moving sand dunes,the soil properties of C.intermedia plantations of 3 years and 5 years old have no change significantly,however,with the increase of plantations age,the soil properties has changed significantly.The soil bulk density of plantations of 16 years and 30 years old decreased significantly?P<0.05?,the roots length,surface area and biomass were significantly negatively correlated with soil bulk density?P<0.05?,content of soil organic matter and total nitrogen of the plantations increased significantly?P<0.05?,especially in shallow soil depth with a large amount of roots,the roots length,surface area and biomass was significantly positively correlated with soil organic matter and total nitrogen?P<0.05?,the total phosphorus and total potassium of soil there were no significant increase,the roots length,surface area and biomass was poor correlation with total phosphorus and total potassium.The roots length and surface area of fine roots and medium roots were significantly negatively correlated with soil bulk density?P<0.01?and significantly positively correlated with organic matter among fine root,medium root and coarse root,the roots length,surface area and biomass of coarse roots were significantly positively correlated with total nitrogen?P<0.01?.