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在两个干旱年份里(1986—1987年和1987—1988年)对加利福尼亚 San Joaquin 试验区蓝栎(Quercus douglasii Hook & Arn.)、韦氏栎树(Quercus Wislizenii DC)和加利福尼亚松(Pinus sabiniana Dougl.)树冠下以及邻近的无遮盖草场上的季节性牧草产量进行了测定。生长季节早期和中期的牧草产量变化不一,与无遮盖草场相比,树冠下的牧草草量在第一年没有增加,第二年每公顷增加60—150公斤。在这两个年份里,蓝栎树冠下牧产的最高定期产量比无遮盖草场大约每公顷高1,000公斤。在本研究的第一年和第二年韦氏栎树树冠下牧草的最高定期产量分别比无遮盖草场大约每公顷高700和1,000公斤。加利福尼亚松树冠下牧草的最高定期产量在第一年大约比无遮盖草场每公顷高500公斤,而在第二年与无遮盖草场的牧草产量相近。
Quercus douglasii Hook & Arn., Quercus Wislizenii DC, and Pinus sabiniana Dougl in San Joaquin, California were studied in two drought years (1986-1987 and 1987-1988) .) Seasonal herbage yields were measured under the canopy and in the adjacent uncovered meadow. Pasture yields varied in the early and mid-season growing seasons, with no increase in forage grass under the canopy in the first year compared to the uncovered pasture and an increase of 60-150 kg per hectare the following year. In both years, the highest regular yield of herds under the blue oak tree was about 1,000 kg higher per hectare than the uncovered meadows. In the first year and the second year of this study, the highest regular yield of canopy grass under canopy oak was about 700 and 1,000 kg higher than unmasked pastures, respectively. The highest regular production of understory grasses under California pine trees was about 500 kg more per hectare in the first year than in the uncovered pasture and similar to pasture production in the uncovered pasture in the second year.