| The objective of this study was to investigate the fine root dynamics of Caragana korshinskii Kom, a shrub species widely planted to control soil erosion and land desertification in the semiarid area of China, in a5-year-old plantation in the Loess Plateau area of Northwest Shanxi, China, using the minirhizotron technique. The minirhizotron tubes were installed at two horizontal distances (0cm and50cm) from the plant stems in the top100-cm of soil. Based on the data sampled in the growing season (from April to September) of2009, we analyzed the spatial-temporal patterns of fine roots in the plantation, and the relationships of RLD, RAD, RLDgr, RADgr,RLDdr and RADdr with the environment factors such as air temperature, soil temperature, rainfall and soil water content. Fine root biomass was measured using soil corer method, and the fine root productivity was estimated.The results showed that (1) there were certain differences in both vertical distribution patterns and seasonal change trends of fine roots between the two horizontal sites, and the obvious difference was that the values of RLD in the upper0-60cm soil layers at the0cm horizontal site were greater than those at the50cm horizontal site, and that the values of RLD (RAD) measured in every month for the former were larger than those for the latter. Therefore the RLD and RAD for the former (4.04mm/cm2and4.67mm2/cm2) were significantly larger than those for the latter (3.07mm/cm2and2.99mm2/cm2). For0cm horizontal site or50cm horizontal site, the seasonal change course of RLD was significantly and positively related with air temperature and soil temperature, respectively.(2) There were also certain differences in the growth and death rates of fine roots between the two horizontal sites, and the obvious difference was that the active layer was in0-50cm soil at the0cm horizontal site while it was in50-100cm soil at the50cm horizontal site. The RLDgr(RADgr) showed a diminishing seasonal trend at0cm horizontal site, and the RLDdr (RADdr) showed a common seasonal trend with the peak value at the50cm horizontal site in the middle period of growing season. The values of RLDgr(RADgr) at the0cm and50cm horizontal sites were0.43mm/cm2·d and0.26mm/cm2·d (0.50mm2/cm2·d and0.39mm2/cm2·d), respevtively. The values of RLDdr (RADdr) at the0cm and50cm horizontal sites were0.45mm/cm2·d and0.30mm/cm2·d (O.51mm2/cm2·d and0.49mm2/cm2·d). For the50cm horizontal site, the seasonal change course of RLDgr was significantly and positively related with air temperature and soil temperature, respectively, and the vertical change course of RADgr (RADdr) was significantly and positively related with soil temperature.(3) At the plantation level, the maximum value of RLD (RAD) appeared in40～50cm soil layer while the minimum value in60～70cm soil layer in the100cm soil profile. The RLD (RAD) showed a common seasonal trend with the peak value in the middle period of growing season. The total averages of RLD and RAD of fine roots in the growing season were3.55mm/ cm2and3.83mm2/cm2. The RLDgr (RADgr) showed a diminishing seasonal trend and the RLDdr (RADdr) showed an increasing seasonal trend. The total averages of RLDgr and RADgr of fine roots in the growing season were0.34mm/cm2·d and0.45mm2/cm2·d. The total averages of RLDdr and RADdr of fine roots in the growing season were0.37mm/cm2·d and0.50mm2/cm2·d. The seasonal change course of RLD (RAD) was significantly and positively related with air temperature and soil temperature, respectively.(4) The SRL (specific root length) of the fine roots of Caragana korshinskii was11.81m/g in the plantation. The annual production of fine roots was0.052g-cm-2·a-1, the annual death rate of fine roots was0.056g cm-2·a-1. The turnover rate was about1.30a-1.The above results showed that the horizontal distribution of the fine roots of young Caragana korshinskii was characterized by appearing mainly around the taproots, and the seasonal change trend of RLD was highly consistent with the change of temperature factor. |
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