Sand-fixing characteristics of Carex brunnescens and its application with straw checkerboard technique in restoration of degraded alpine meadows

Abstract

Carex brunnescens (Pers.), a typical clonal species, is considered to be the only herb found to date that can develop on sand dunes in Maqu alpine region of northwestern China. However, the characteristics that C. brunnescens resists to harsh alpine environment have not been documented. In this study, we conducted a field investigation to determine the morphological, reproductive, and sand-fixing characteristics of C. brunnescens. Concomitantly, we transplanted the belowground rhizomes of C. brunnescens to sand dunes and compared the abilities to restore degraded alpine meadows among sand dunes that had no further treatment (SD+N), sand dunes that had straw checkerboard technique but no transplanted rhizomes of C. brunnescens (SD+SCT), and sand dunes that had both SCT and transplanted rhizomes of C. brunnescens (SD+SCT+P). We found that belowground vertical rhizomes and horizontal rhizomes (including branching rhizomes and main rhizomes) of C. brunnescens were highly developed and that population reproduction was dominated by horizontal rhizomes. C. brunnescens exhibited a significant sand-fixation effect under following conditions: population density was 145–156 ramets/m2, vegetation cover was 31.2%–39.3%, total length of belowground rhizomes was 11,223 cm/m2, total length of belowground first-order roots was 9161–10,524 cm/m2, fresh weight of aboveground part was 198.5–212.6 g/m2, and fresh weight of belowground part was 578.8–612.4 g/m2. It should be particularly noted that SD+SCT+P treatment (sand dunes that had both straw checkerboard technique and transplanted rhizomes of C. brunnescens) was the best and SD+N (sand dunes that had no further treatment) was the worst in terms of following biotic indicators: total number of reproductive ramets, total number of belowground rhizomes, and fresh weight of aboveground and belowground parts of C. brunnescens, contents of soil organic carbon, available nitrogen, microbial biomass carbon, and microbial biomass nitrogen. It implies that applying SCT in sand dunes and transplanting belowground rhizomes to sand dunes with SCT could improve both soil fertility and growth of C. brunnescens. These results suggest that the SCT-promoted high reproductive abilities of belowground rhizomes of C. brunnescens can successfully facilitate the establishment of ramets and can thus be an effective strategy to restore degraded vegetation in Maqu alpine region of northwestern China.