论文部分内容阅读
为探究尾巨桉乔木层养分随林龄变化的趋势,对闽南山区连续年龄序列(2年、3年、4年、5年、6年)尾巨桉(Eucalyptus urophylly×E.grandis)人工林乔木层的养分积累、分配和循环特征进行了研究.结果表明:(1)尾巨桉各组分中氮(N)的含量最高,其次是钾(K)、钙(Ca)、镁(Mg),最低的为磷(P).(2)尾巨桉养分贮量随林龄增长而增加,各林龄5种养分元素的总贮量依次为753.26、882.07、1 010.22、1 087.51、1 704.79 kg hm-2,其中树干的养分贮量最大,枝的贮量最小.(3)各年龄段人工林对5种养分元素的年净积累量分别为383.37、392.25、424.21、400.89、505.36 kghm-2a-1.(4)各林分养分年吸收量随林龄增加而增加,而养分归还量则呈相反趋势.(5)林分对营养元素的利用系数分别为0.51、0.44、0.42、0.37、0.30,随林龄增加而逐渐减小;循环系数分别为0.18、0.19、0.24、0.24、0.16;周转时间分别为8.76、9.75、7.58、9.39、17.47年.因此,尾巨桉在生长初期对养分的利用效率较小,中期归还给林地的养分多,到了后期对养分利用增加的同时,归还速率也变小,容易引起林地养分的匮乏,在尾巨桉生长初期和后期中应通过施肥、增加林下植被种类和数量来维持林地地力.
In order to explore the trend of tree layer nutrient changes with age in Eucalyptus urophylla, the effects of different age groups (2 years, 3 years, 4 years, 5 years and 6 years) of Eucalyptus urophylly × E. grandis The results showed that: (1) The content of nitrogen (N) was the highest in all components of Eucalyptus urophylla, followed by potassium (K), calcium (Ca), magnesium ), And the lowest was phosphorus (P). (2) The nutrient storage of Eucalyptus urophylla increased with the increasing of age, and the total storage of five nutrient elements in each age were 753.26,882.07,1 010.22,1 087.51, 1 704.79 kg hm-2, of which the trunk had the largest nutrient reserves and the branches had the least reserves. (3) The annual net net accumulation of five nutrient elements in the plantation was 383.37,392.25,424.21,400.89, 505.36 kghm-2a-1. (4) The annual uptake of nutrients in each forest increased with the increase of age, while the return of nutrients showed the opposite trend. (5) The utilization factors of nutrient elements in the stand were 0.51, 0.44, 0.42,0.37,0.30, with the age increasing and gradually decreased; the coefficient of circulation were 0.18,0.19,0.24,0.24,0.16; turnaround time was 8.66, 9.75, 7.88, 9.39, 17.47 years. Therefore, Eucalyptus urophylla Eucalyptus urophylla had less nutrient utilization efficiency in the early stage of growth, more nutrients were returned to the forest land in the middle period, and the rate of returning was also smaller with the increase of nutrient utilization in the late stage, which easily led to the lack of nutrients in the forest. In the early and late stages of growth, the fertility of the forest should be maintained to increase the species and quantity of understory vegetation.