关键词: 黑土, 保护性耕作, 土壤崩解速率, 水土流失, 土壤侵蚀

Abstract: We selected typical croplands in the black soil region of Northeast China to analyze the characteristics of biocrusts during the growing season, including species composition, thickness, coverage, and biomass (chlorophyll content). We collected bareground soil and biocrusts samples with chlorophyll content of 5-15, 15-25, 25-35, and 35-50 mg·g^-1, and measured the soil disintegration rate and soil maximum disintegration ratio of each sample using a force gauge in the laboratory. The results showed that: 1) biocrusts dominated by algae and moss were frequently developed in the croplands, with Stigeoclonium and Bryum capillare as the most common species, respectively. The thickness and biomass of algal crusts were significantly lower than moss crusts, with a successional trend from algal crusts to moss crusts. 2) The coverage, thickness, and biomass of biocrusts in croplands were negatively correlated with the frequency and intensity of tillage disturbance. For instance, the values of those characterisitics were only 27.8%, 1.52 mm, and 6.49 mg·g^-1 on average, respectively, in traditional tillage croplands, and increased to 83.5%, 2.74 mm, and 34.16 mg·g^-1, respectively, in the croplands with conservational tillage. 3) Biocrusts considerably reduced the disintegration of surface soil, particularly in the layer of biocrusts. Compared to the bareground soil, the soil disintegration rate of biocrusts, with four levels of biomass (with chlorophyll content of 5-15, 15-25, 25-35, and 35-50 mg·g^-1), was reduced by 43.1%, 50.1%, 55.5%, and 59.8%, respectively, while the soil maximum disintegration ratios were reduced by 11.4%, 17.7%, 33.2%, and 36.6%, respectively. 4) Soil disintegration rate and maximum disintegration ratio were significantly and negatively correlated with the biomass and thickness of biocrusts, indicating that the impacts of biocrusts on soil disintegration were primarily caused by the improvements in physical properties of surface soil. In conclusion, biocrusts were frequently deve-loped in croplands in the black soil region of Northeast China, owing to less disturbance following the conversion from traditional tillage to conservational tillage. They had the potential to protect surface soil against disintegration and improve soil anti-scourability, which was critical for soil conservation in croplands in this region.

Key words: black soil, conservational tillage, soil disintegration rate, water and soil loss, soil erosion