黄土丘陵区生物结皮坡面产流产沙与其分布格局的关联

生物结皮在黄土丘陵区退耕地广泛发育,并在干扰等因素下形成不同分布格局。为明确生物结皮分布格局对坡面产流产沙的影响,采用模拟降雨试验研究了生物结皮条带状、棋盘状和随机3种分布格局对坡面产流产沙的影响,借助景观生态学方法,计算了生物结皮斑块的分布格局指数,解析了生物结皮分布格局与坡面产流产沙的关联。结果表明,（1）生物结皮分布格局显著影响坡面初始产流时间、径流率和土壤侵蚀速率。相同盖度条件下,生物结皮坡面的随机分布格局较带状和棋盘式分布格局显著降低了坡面径流量和产沙量,其径流率与土壤侵蚀速率分别是带状格局的71.7%、12.9%,是棋盘格局的89.6%、31.8%。（2）坡面径流率与生物结皮斑块最大斑块指数、斑块连结度呈极显著负相关,与分离度呈极显著正相关,与景观分裂指数呈显著正相关。（3）土壤侵蚀速率与生物结皮斑块最大斑块指数、斑块连结度呈显著负相关,与景观分裂指数、分离度呈显著正相关。（4）坡面径流率（Y₁）和土壤侵蚀速率（Y₂）与分离度（SPLIT,Splitting Index）的关系式为：Y₁=1.116+0.017SPLIT,R²：0.957;Y₂=22.767+17.936SPLIT,R²：0.801。（5）以上结果表明分布格局主要是通过影响生物结皮在坡面的分离度进而影响坡面产流产沙,随着生物结皮斑块分离度增大,生物结皮斑块破碎度增大,坡面产流产沙增多。从分布格局的角度解析了生物结皮对产流、产沙的影响,量化了生物结皮坡面径流率与侵蚀率与格局指数之间的关系,为量化认识生物结皮的水土保持功能提供了科学依据。

Correlation between runoff and sediment yield from biological soil crustal slope and its distribution patterns in the Hilly Loess Plateau Region

Biological soil crusts (biocrusts), which are widely distributed in the revegetated grasslands and forms various distribution patterns due to the disturbance, are a major influence factor on runoff and sediment yield in the Hilly Loess Plateau Region, China. In order to clarify the effect of biocrusts distribution patterns on the runoff and sediment yield from the slope surface, the runoff and sediments yield from three distribution patterns of biocrusts (zonation, chessboard, and random) were investigated by using the simulated rainfall experiments. In addition, the pattern index of the biocrusts patch was calculated by means the landscape ecology method. The association between the biocrusts distribution pattern and runoff and sediment yield on the slope was analyzed. The results showed that (1) biocrusts distribution pattern significantly affected the initial runoff time, runoff rate and soil erosion rate from the slope. Under the same coverage conditions, the random distribution of biocrusts significantly reduced the runoff and sediment yield of the slope compared to the zonal and checkerboard pattern. The runoff rate and soil erosion rate of random distribution pattern was 71.7% and 12.9% of the zonation pattern, 89.6% and 31.8% of the chessboard pattern. (2) The runoff rate on the slope surface was extremely significantly negatively correlated with the Largest Patch Index (LPI) and Patch Cohesion Index (COHESION) of biocrusts patch. It was extremely significantly positively correlated to the Splitting Index (SPLIT) and significantly positively correlated with the Landscape Division Index (DIVISION). (3) soil erosion rate was negatively correlated with the LPI and COHESION of biocrusts patch. It was positively correlated with the DIVISION and SPLIT. (4) The relationship between runoff rate (Y₁) and soil erosion rate (Y₂) and SPLIT was: Y₁=1.116+0.017SPLIT, R²: 0.967; Y₂=22.767+17.936SPLIT, R²: 0.801. (5) The results of the study showed that the distribution pattern mainly affected the separation of biocrusts on the slope surface and then affected the runoff and sediment yield. The biocrusts patch fragmentation degree and the runoff and sediment yield increased along with the increase of the biocrusts patch SPLIT. This study analyzes the effects of biocrusts on runoff and sediment yield from the perspective of the distribution pattern, quantifies the relationship between runoff rate and erosion rate and pattern index of biocrusts slopes, which provides a scientific basis for quantifying the function of biocrusts on soil and water conservation.