果园植被盖度季节变化监测及生物措施因子测算

Monitoring of seasonal variation of vegetation cover and evaluation of biological-control factor in orchards of China

生物措施因子(B)能够定量衡量植被覆盖对土壤侵蚀的抑制作用.本文采用照相法对全国5个水力侵蚀分区的18个小流域的果园植被覆盖季节变化进行监测,并计算了植被盖度和郁闭度,最后计算果园B值.结果表明:果园郁闭度受人为活动影响小,季节变化呈"几"字形分布.果园的绿色盖度和总盖度因地表下垫面的管理不同而表现出不同的季节变化规律.在林下未清理的果园中,各水力侵蚀分区的绿色盖度呈"几"字形分布;5个水力侵蚀分区中,西北黄土高原区植被总盖度呈"几"字型分布,其余几个分区植被覆盖总盖度呈"一"字形分布,随季节变化不明显.在林下清理的果园中,所有水力侵蚀分区的植被盖度季节变化无规律性.东北黑土区果园B因子最小,平均值为0.0066,西北黄土高原区果园B因子平均值最大,为0.1212,北方土石山区、南方红壤区和西南土石山区果园B因子平均值相差不大,分别为0.0548、0.0627和0.0639.

Biological-control factor（ B） can quantitatively reflect the effect of vegetation on soil erosion. Vertical photography method was used to monitor the seasonal changes of orchard coverage in 18 small watersheds,covering all five water erosion zones in China. The canopy coverage and ground green coverage were then calculated,and the B values were estimated. The result indicated that the orchard canopy coverage varied with season and distributed with a bell shape. The trend of ground green coverage and total coverage changed with season and was affected by the land management. For the orchard where the land surface was not treated and the weeds could grow freely,the distribution of the green coverage season change for all five soil erosion zones had a bell shape. The total coverage in the Northwest Loess Plateau area changed with season with a bell shape as well.The total coverage in the other four areas did not vary with the season and almost kept constant. For the orchard where land surface was cleaned up from time to time,the green coverage and total coverage in all five water erosion areas irregularly varied with season. The average B value of orchards in Northeast black soil area was the minimum with a value of 0. 0006,while that in the Northwest Loess Plateau area was the maximum（ 0. 1212）. The average orchard B values in the Northern rocky earthy area,the Southern red soil area and the Southwest rocky earthy area were not significantly different and were 0.0548,0.0627 and 0.0639,respectively.