密云水库库滨带植被水土保持作用的研究

Effect of Different Types of Vegetations on Soil and Water Conservation in the Miyun Reservoir Buffer Zone

以裸露荒坡地为对照,在密云水库库滨带不同植被中设置径流试验小区,研究植物生物学特性及其动态变化对坡地水土流失防治的影响,结果得出,不同恢复植被中,人工草地建植1年后,植株密度可达545.0×10^4株/hm^2,植被覆盖度与0～30 cm土层地下生物量最高可达92.3%～97.7%和2 238.8 kg/hm^2;雨季玉米植株高度与地上生物量在各类型植被中最高,可达133.3 cm和11 035.3 kg/hm^2,此时自然恢复地植被地上、地下生物量相对最低。坡地水土流失与降雨有关,降雨量越大,水土流失越严重,但无论降雨量大小,人工草地水土保持效果最佳,保水、固土能力可达92.3%～93.2%和99.8%～99.9%,其次是围封1年后的自然恢复植被,保水、固土能力为83.3%和98.7%;玉米作物水土保持效果最差,保水、固土能力仅为8.9%和18.5%。

Miyun Reservoir is the biggest watering base for Beijing＇s people,and it has 4.375 billion m3 of whole reservoir capacity,188 km^2 of water area and 15 788 km^2 of watershed.However,there have been many barren slopes in the reservoir buffer zone,half of which were used for maize,since water level declined in the 1980s.The soil eroded area was increasing due to less vegetation.So experiment was conducted on the effect of different types of vegetations on soil and water conservation after artificial grasses and maize planting on the barren slopes,and comparison was made with the barren slopes in the reservoir buffer zone,for promoting soil and water conservation in the Miyun Reservoir.Based on studies on biological and dynamic characteristics of plants in the experimental plots,results were obtained as follows.On the one hand,grass density was the highest with 5450 thousand per ha after artificial grassland was planted for one year,and its cover and underground biomass in soil of 0-30 cm were 92.3%-97.7% and 2238.8 kg/ha.In the rainy season,maize height and above-ground biomass were the highest with 133.3 cm and 11035.3 kg/ha.Meanwhile,the above-ground and underground biomass of natural vegetation were the least among three types of vegetations.On the other hand,soil and water loss in the reservoir buffer zone was related to rainfall,and soil erosion and surface runoff increased with the increase of rain fall.No matter what rainfall was,the difference between vegetations was significant to soil and water conservation.The artificial grassland was most effective to preventing surface runoff and soil loss on the slope in the reservoir buffer zone with 92.3%-93.2% of water conserved and 99.8%-99.9% of soil conserved.Then the next was the vegetation after being fenced for one year with 83.3% of water conserved and 98.7% of soil conserved.The least one was maize which had capacities of soil and water conservation of only 18.5% and 8.9%.