摘要
光照是森林更新动态中极为关键的环境因子。本研究在东北天然次生林中选择样地 ,应用地统计学理论结合实验生态学方法 ,定量分析林分光照空间异质性特征 ,同时进行林下播种水曲柳 (Fraxinusmandshurica)的更新实验 ,探测更新格局特征。通过空间关联性分析 ,研究探讨是否林分光照的空间变异对水曲柳更新有重要影响作用。研究结果表明 :1)生长季林分平均光照仅为全光照的 4 .2 %～ 4 .6 % ,在空间分布上呈现非常明显的异质性特征 ,空间自相关变异 (6 2 .5 %～ 78.2 % )主要体现在 10 .9～ 12 .4m的尺度上。 2 )林分光照不同的空间样点上 ,水曲柳更新幼苗发生数量和秋季幼苗存活数量均存在显著差异 ,光照相对强的微生境中 ,更新苗发生数量较多且存活率高 ,而在光照较弱的微生境中则更新较差 ,更新具有十分明显的空间格局。 3)更新格局与林分光照空间异质性特征紧密关联。在光照空间异质性程度较高、空间变异较复杂的条件下 ,更新相应呈现出较复杂的空间格局 ,自相关的变异表现在较小尺度范围 (2 .12～ 6 .97m)。在光照空间异质性程度较低、空间变异复杂性较小的条件下 ,更新格局的复杂程度明显变小 ,空间自相关变异 (>83% )表现在较大的尺度上 (30m) ,对更新格局起主要的影响作用 ,随机变异的影响很小
Understory light availability is a major environmental factor affecting the growth and survival of many forest species. The spatial heterogeneity of light availability most likely influences forest regeneration dynamics and determines stand-level spatial patterns of seedling regeneration. However, the implications of heterogeneity in understory light availability on regeneration patterns have not been carefully investigated. We examined spatial patterns of understory light availability and Manchurian ash (Fraxinus mandshurica) seedlings within two experimental plots in secondary hardwood forests at the Silviculture Research Station of Northeast Forestry University, northeastern China (127°30′-127°34′E,45°21′-45°25′N). Our objectives were to compare spatial patterns of understory light with seedling distribution patterns to determine whether patterns of seedling regeneration were linked to spatial patterns of understory light availability. Understory light availability was measured at 297 sample points in a regular grid-based spatial sample design. The minimum interval distance between measurements was 0.5 m and the maximum interval distance was 30 m. Light levels were measured at a height of 70 cm using an LAI-2000 Plant Canopy Analyzer at each point. Seedlings were counted at 193 sown grid subplots (20 cm×20 cm) in each plot (30 m×30 m) during the growing season. Semivariograms from geostatistical analysis methods were used to quantify the spatial variations of understory light availability and seedling distributions. We also examined the statistical relationships between light availability and seedling regeneration at different spatial scales. The results demonstrated that there was significant spatial patterning of both understory light availability and seedling regeneration. The transmittance of light to the ground within stands was 40.2%-52.3% after the growing season and only 4.2%-4.6% during the growing season. According to theoretical model parameters, understory light availability was significantly spatially autocorrelated over scales at 10.9-12.4 m, and spatially structured variance accounted for 62.5%-78.2%. Seedling density in each subplot differed significantly among microsites with significantly higher numbers of seedlings in high-light microsites than in low-light microsites. Seedling regeneration showed strong spatial patterning. Patterns of seedling regeneration were strongly linked to spatial heterogeneity of light availability. In stands with more spatially heterogeneous light availability patterns had more complex patterns of seedling distribution patterns and were spatially autocorrelated at smaller scales (2.12-6.97 m). In stands with lower complexity of light spatial distribution patterns, the patterns of seedling regeneration were relatively simple. Regeneration patterns were significantly spatially autocorrelated (>83%) at slightly larger scales (30 m) with little random variation (<17%). Our results confirmed that the spatial heterogeneity of understory light availability is a critical factor influencing the performance of seedling regeneration of Manchurian ash.
出处
《植物生态学报》
CAS
CSCD
北大核心
2004年第4期468-475,共8页
Chinese Journal of Plant Ecology
基金
国家自然科学基金资助项目 ( 3 0 0 70 13 2 )
国家自然科学基金重点项目 ( 3 0 13 0 160 )
关键词
林分光照
空间异质性
更新
水曲柳
森林
Understory light availability, Spatial heterogeneity, Regeneration, Fraxinus mandshurica, Spatial analysis
