架空线下速生超高树木树高生长规律研究

Tree height growth rhythm of fast-growing ultra-high trees under overhead line

采用树干解析法,考虑立地条件(Ⅰ:山脚山腰厚土型,Ⅱ:山顶山脊薄土型)和林木起源(1:第1代林,2:第2代林)等因素,对架空线下速生桉和湿地松优势木的高生长规律进行研究,结果表明:速生桉高生长高峰期第1代林为栽后前4年、第2代林为栽后前3年,高峰期平均年高生长Ⅰ-1、Ⅱ-1、Ⅰ-2、Ⅱ-2分别为4.13 m、3.5 m、5.0 m、4.5 m;速生桉林木起源相同时,树高生长Ⅰ>Ⅱ;速生桉第2代林前期生长快,后期生长速度显著减弱,第1代林前期生长速度不如第2代林,但后期速度降低也慢,6年生时,树高排序为Ⅰ-1>Ⅰ-2>Ⅱ-1>Ⅱ-2;立地条件对湿地松的树高生长影响很大,24年生湿地松树高Ⅰ(19.5 m)>Ⅱ(13.5 m);湿地松树高生长高峰Ⅰ为前11年,树高可达16.0 m,Ⅱ为前9年,树高为9.0 m;速生桉和湿地松的树高生长曲线均服从以树高为因变量、年龄为自变量的多项式模型,除速生桉Ⅱ-1为2次多项式外,其他均为3次多项式,相关系数(R2)均在0.995以上。通过树高生长模型可预测架空走廊树木随时间的生长高度,结合导线弧垂变化规律,可构建超高树木安全距离预警系统,提前排除超高树木隐患,有效提高架空线路的运行安全性。

Tree height growth rhythm of fast-growing Eucalyptus and dominant tree of Pinus elliottii under overhead line, considering the site conditions（ Ⅰ ： the foot of a hill or hillside, thick soil type, Ⅱ ： the top of a mountain or ridge, thin soil type） and trees origin（1： the first generation forest, 2： the second generation forest） factors, was studied by stem analysis. The results showed that the first 4 years after planted is the fast height growth period of the first generation forest of fast-growing Eucalyptus, and the first 3 years after planted is the fast height growth of the second. During the fast height growth period, 4.13 m, 3.5 m, 5.0 m, 4.5 m was the average annual growth of Ⅰ-1、 Ⅱ-1、 Ⅰ-2、 Ⅱ-2. Tree height growth of the same generation forest of fast-growing Eucalyptus： Ⅰ〉Ⅱ.The second generation of fast-growing Eucalyptus on the early period grow faster, w hile the growth rate decreased dramatically on the late period. The growth rate of the first generation on the early period is slower than that of the second, but that decreased more gently. The height order of fast-growing Eucalyptus at six years： Ⅰ-1〉Ⅰ-2〉Ⅱ-1〉Ⅱ-2. Site conditions had a great influence on tree height growth of Pinus elliottii, for example, the height of 24 years＇ Pinus elliottii： Ⅰ（19.5 m）〉Ⅱ（13.5 m）; The early 11 years are the fast height growth period of Pinus elliottii at Ⅰ, which can up to 16.0 m height, while the early 9 years are the fast period at Ⅱ, tree height of 9.0 m. The height growth curve models of fast-growing eucalyptus and Pinus elliottii were 3 times polynomial, in addition to the fast-growing Eucalyptus Ⅱ-1 as 2 times polynomial, with height as the dependent variable and age as independent variable, and the correlation coefficient（R^2） are above 0.995. Building the safe distance of high trees warning system can eliminate ultra-high tree hazards in advance to improve the running safety of overhead line effectively, through predicting height of growth over time by tree height growth model of bridge way and combining with the change rule of conductor sag.