＜正＞ The desertification of northern China,with its extensive distribution and rapidgrowth rate,has become the major prob-lem for regional environmental and socialeconomical development.Until 2000,thetotal area of desertified land was 3.857×10~5 km~2,and it continues to spread at3595 km~2 y-1（1）.To prevent further de-sertification,the Chinese governmentused biotechnology and engineeringmeasures（2,3）;however,the results wereinsignificant.In the late 1990s,the Chi-nese central government envisioned thebenefits of returning farmland to forestry
展开▼
