The cutting reproduction technique of Salix oritrepha and its application on degraded grasslands restoration

Abstract

Salix oritrepha is one of the most adaptable perennial woody plants found to date in the Maqu alpine regions. We use the cutting reproduction technique with the S. oritrepha and apply the straw checkerboard technique (SCT) to restore degraded alpine grasslands. Cuttings of S. oritrepha with different cutting positions (hardwood 0.5 to 1 [0.2 to 0.4 in] and 1 to 1.5 cm [0.4 to 0.8 in]; softwood 0.3 to 0.5 cm [0.12 to 0.2 in]; and root 0.5 to 1 cm [0.2 to 0.4 in] in diameter) and lengths (15 and 20 cm [5.9 to 7.8 in]) were treated with different cultivating methods in field and potted culture experiments (April of 2005 to October of 2007). One year old plants were transplanted to sand dunes with no precautions and sand dunes with SCT in April of 2008, and harvested in October of 2012. The results indicate that the hardwood cuttings (1 to 1.5 cm [0.2 to 0.4 in] in diameter and 20 cm [7.8 in] in length) which were potted in a vinyl house, cut in a vinyl house, and covered with a plastic membrane in the field, were the best cutting cultivation methods. However, it is noteworthy that the plants potted in a vinyl house show better growth performance in sand dunes with SCT than plants cut in a vinyl house and covered with a plastic membrane in the field cultivated. The vinyl-house potted method (1 to 1.5 cm [0.4 to 0.8 in] in diameter and 20 cm [7.8 in] in length,) promoted plant height, total dry weight, survival rate of cuttings, and preservation rate, and, concomitantly, increased the soil's organic carbon (C), available nitrogen (N), and soil microbial biomass C and N, resulting in a significant improvement in both the microenvironment and the stability of the dune surface (0 to 30 cm [0 to 11.8 in]). The contribution of the soil's organic C and available N to soil fertility (compared with sand dunes with no precautions) ranged from 43% and 54% in the sand dunes with SCT, and increased to 83% and 86% in vinyl-house potted method cultivated plants grown in the sand dunes with SCT. The microbial biomass C and N varied from 18% and 38% in the sand dunes with SCT and increased to 40% and 85% in vinyl-house potted method cultivated plants grown in sand dunes with SCT (0 to 10 cm [0 to 3.9 in], similar to that of 10 to 20 cm [3.9 to 7.8 in] and 20 to 30 cm [7.8 to 11.8 in] in soil depths). These findings suggest that the sand dune fixation of vinyl-house potted method cultivated S. oritrepha (hardwood 1 to 1.5 cm [0.4 to 0.8 in]; length 20 cm [7.8 in]) with the SCT is considered an effective strategy to restore degraded grasslands in the alpine regions of China.