不同栽植代数杉木林养分吸收、积累和利用效率的比较

利用第一代以及与第一代连栽的第二代杉木林的40多年定位连续测定的生物量和养分数据,分析了第一和第二代杉木林在养分吸收、积累、利用效率的差异。结果表明:同一生育阶段第二代杉木体内N、P、K、Ca、Mg浓度分别比第一代高2.85—3.48,0.16—0.25,1.86—2.72,2.10—2.50,0.77—1.31 g/kg;第一代7、20、25年生时的养分积累量分别比第二代多9.14%,2.01%,0.22%,而11、16年生时则分别比第二代少6.72%,3.44%,杉木连栽不一定导致第二代林乔木层养分积累减少;第一代1—7年生的年均吸收养分量比第二代多7.94%,8—11,12—16,17—18、21—25生分别比第二代少13.04%,2.52%,7.93%和14.58%;1—7,8—11,12—16,17—20,21—25年生时,每生产1 t干物质所需养分,第二代比第一代分别多1.28、3.19、4.28、4.09、4.09 kg;杉木连栽可导致第二代林的养分吸收量增多,养分利用效率降低。

Nutrient uptake, accumulation, and utilization efficiency comparisons in plantations containing different generations of Chinese fir

The differences in nutrient absorption, accumulation, and utilization efficiency were analyzed at the first and the second rotations in Chinese fir (Cunninghamia lanceolata) plantations using a 40 year database of biomass and nutrient levels from Huitong National Research Station of Chinese Fir Plantation Ecosystem in Hunan Province, Central South University of Forestry and Technology, China. The results showed that the N, P, K, Ca, and Mg concentrations in the second rotation were 2.85-3.48, 0.16-0.25, 1.86-2.72, 2.10-2.50, and 0.77-1.31 g/kg higher than in the first rotation, respectively. The nutrient accumulation of the first generation was 9.14%, 2.01% and 0.22% higher than that of the second generation at 7, 20, and 25 years old,respectively, while that of was 6.72% and 3.44% lower than that of the second generation at 11 and16 years old, respectively. Chinese fir continuous planting does not necessarily lead to the second generation of forest tree layer nutrient accumulation decreased. Annual absorption of nutrients in the first rotations (1-7 years old) was 9.14% higher than the second rotations at the same age. However, at the ages of 8 to 11, 12 to 16, 17 to 18, and 21 to 25, they were 13.04%, 2.52%, 7.93%, and 14.58% less than the second rotations, respectively. In the same age classes, the second rotations required1.28, 3.19, 4.28, 4.09, and 4.09 kg more nutrients for each year class, respectively, to produce 1 ton of dry matter compared to the first rotations. These results indicate that successive rotations bring about an increase in nutrient uptake, and a decrease in nutrient use efficiency in the second rotations across the central south subtropical regions.