Investigations of soil microbial diversities in the Tarim desert highway shelter forest lands drip鄄irrigated with saline water with methods of Biolog鄄eco, PLFA and PCR鄄DGGE, and evaluation of the soil fertility qualities using integrated fertility index (IFI) method, were conducted in this work; the relationship between soil microbial diversity and IFI values were also revealed. The main results are below: (1) Notable differences on diversities of carbon metabolism, genetic gene and fatty acid were found among the sandy soils drip鄄irrigated with different saline water (F > F 0.05) ; The water with higher mineralization reduced the soil microbial activity. (2) The notably significant differences of soil IFI values were found among the forest lands with different plantation times (F > F 0.01) ; Meanwhile, the vertical variation of IFI values at the different soil layers were also markable (F >F 0.05) , the value at 0-5 cm was the least, and the IFI value decreased with increase of mineralization of the saline water. (3) There were power function relationships between the soil IFI values and the soil microbial diversities of carbon mechanism, fatty acid, but polynomial relationship existed in the IFI value and the soil microbial genetic gene. So, microbe population would contribute greatly to increase soil fertility in the Tarim desert highway shelter forest lands under saline water drip鄄irrigation.
Water and nitrogen (N) are two primary factors controlling plant growth in desert ecosystems. Most studies have focused on water stress resulting from the low rainfall and high evaporation rates in arid areas. However, irrigation has become the main strategy for vegetation recovery in the southern rim of Tarim Basin. Many studies have shown that irrigation is most effective when nutrients are not limited, and fertilization is most effective when plants are not water鄄stressed. In addition, N not only affects drought tolerance through changing dry matter partitioning, but also plays an important role in ecosystem functioning and vegetation succession. Therefore, the combined effects of water and N on vegetation recovery and reconstruction in this area should be evaluated. We conducted a pot experiment to study characteristics of N allocation, use, and resorption, and growth of Calligonum caput鄄medusae Schrenk seedlings under different irrigation treatments (4.6, 6.1, 7.7, 9.2, 13.0 kg / plant per irrigation event). The results showed that the amounts of both N and dry matter per whole plant significantly increased with increasing amounts of irrigation. However, C. caput鄄medusae Schrenk seedlings were infected with powdery mildew at the high irrigation level (13.0 kg / plant). During the early growth stage, irrigation promoted dry
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