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受林冠截持影响后形成的林下穿透雨的数量和空间分布会影响林地的入渗、产流、蒸发等水文过程和林木生长及枯落物分解等生态过程,因而精细的森林水文功能评价和森林生态系统经营都需要准确描述林下穿透雨的空间变异规律。在宁夏六盘山香水河小流域设立了面积为30 m×30 m的华北落叶松人工林样地,均匀布设了40个截面面积230.58 cm2的雨量收集器,测定了2015年生长季(5—10月)34次降雨事件的穿透雨量。结果表明,研究期间林外总降雨量567.0 mm,林下总穿透雨量483.5 mm,占同期雨量的85.3%。随着次降雨量增加,林内次穿透雨率呈现先快速增加后趋于稳定的变化。穿透雨量在林内存在较大空间变异,其变异程度随次降雨量增加先快速下降后趋于稳定。林下穿透雨空间分布受树木特征(穿透雨收集器上方的林冠叶面积指数和冠层厚度、穿透雨测点离最近树干的距离)的影响,且其影响随次降雨量大小而变,当次降雨量<10 mm时,穿透雨量与叶面积指数显著负相关;当次降雨量在10—20 mm时,穿透雨量与距最近树干距离显著正相关,与冠层厚度显著负相关;当次降雨量>20 mm时,穿透雨量与3个树木特征均不显著相关。考虑到研究区次降雨量集中在0—10 mm,在95%或90%的置信区间下,若将测定的次穿透雨数值误差控制在10%以内时,在30 m×30 m样地内至少需布设13或9个本研究所用大小的收集器;满足次穿透雨数值误差在5%以内时,至少需布设26或23个这样的收集器。
The quantity and spatial distribution of under-ground penetrating rain formed by the canopy interception affect the ecological processes of infiltration, runoff, evaporation and other hydrological processes and forest tree growth and litter decomposition in forest so that the fine forest hydrological function Evaluation and management of forest ecosystem need to accurately describe the spatial variation of under-penetration of rain forest. A sample of Larix principis-rupprechtii plantation with the area of 30 m × 30 m was set up in the Xiangshuihe small watershed of Liupanshan in Ningxia. 40 rainfall collectors with a cross-sectional area of 230.58 cm 2 were evenly laid. The growing season of 2015 Month) 34 rainfall events through the rainfall. The results showed that during the study period, the total rainfall outside the forest was 567.0 mm, the total penetrating rain under the forest was 483.5 mm, accounting for 85.3% of the rainfall over the same period. With the increase of sub-rainfall, the rate of penetration through rain forest increased rapidly and then stabilized. Penetration of rainfall in the forest there is a large spatial variability, the degree of variation increases rapidly with the increase of rainfall at first, then tends to be stable. The spatial distribution of under-penetration rains is affected by the tree characteristics (canopy leaf area index and canopy thickness penetrating the rain collector, the distance of the penetrating rain measuring point from the nearest trunk), and its effect varies with the amount of rainfall When rainfall is less than 10 mm, there is a significant negative correlation between rainfall penetration and leaf area index. When the rainfall is 10-20 mm, there is a significant positive correlation between rainfall penetration and the distance to the nearest trunk, and the thickness of the canopy Negative correlation; when the rainfall> 20 mm, there was no significant correlation between rainfall penetration and the three tree characteristics. Considering that the rainfall in the study area is concentrated in the range of 0-10 mm, and the 95% or 90% confidence interval is within 30 m × 30 m when the numerical error of measured penetration is within 10% At least 13 or 9 collectors of the size used in this study shall be laid; at least 26 or 23 such collectors shall be laid to meet the numerical error of penetration penetration of less than 5%.