摘 要 ：测定了不同石漠化等级的西南喀斯特生态系统的土壤容重和土壤有机碳。结果表明：西南喀斯特生态系统的土壤容重为0.91~1.37 kg cm-3，土壤有机碳含量变化较大，为8.1~58.9 g kg-1。在0~40 cm的土层中，没有发生石漠化的生态系统的有机碳储量达16.91 kg m-2，伴随着石漠化程度的加剧，土壤有机碳储量急剧下降，极度退化土壤的有机碳储量只有0.52 kg m-2。在1999-2005年间，中国西南石漠化(约550000 km2)导致的有机碳流失通量年增加量超过28 Tg。同时，探讨了喀斯特石漠化过程中土壤有机碳流失的去向，喀斯特石漠化过程土壤有机碳对生态恢复的限制作用，利用土壤容重推算土壤有机碳的可靠性。
Abstract:To achieve foreign protein expression in the chloroplast of Phaeodactylum tricornutum, a chloroplast transformation vector was constructed. The sequences rns-trnI and trnA-rnl from P. tricornutum chloroplast genome were cloned and used as homologous recombination elements. Chloramphenicol acetyltransferase gene (CAT) expression cassette conferring chloramphenicol resistance was employed as selection marker, and green fluorescent protein gene (GFP) as reporter gene. Based on the TA cloning vector pMD19-T, CAT and GFP expression cassette were cloned in between the two homologous recombination elements. The resultant chloroplast transformation vector was transferred into the chloroplast of P. tricornutum by electroporation method. Transplastomic P. tricornutum cells were obtained upon chloramphenicol selection and reporter GFP could be detected in the chloroplasts, indicating that chloroplast expression system was successfully achieved.