Kouki Jari, Hokkanen Tatu
Department of Zoology, University of Helsinki, P. Rautatiekatu 13, SF-00100, Helsinki, Finland.
Finnish Forest Research Institute, P.O. Box 18, SF-01300, Vantaa, Finland.
Oecologia. 1992 Feb;89(2):176-181. doi: 10.1007/BF00317216.
Needle litterfall of a Scots pine was caught over 24 years (1962-1986) with litter-traps in a Scots pine stand in southeastern Finland. The age of the trees averaged 111 years in 1962. The stand was naturally recruited and only minor silvicultural treatments occurred during its history. Litterfall showed great year-to-year variation, the minimum being 18 g/m (in 1968) and maximum 213 g/m (in 1973). There was no overall trend in the amount of litterfall, and the age of the stand was thus not important in determining the needle fall. We used time domain time series analysis (ARIMA) and standard climatic data (temperature, precipitation) to investigate the relationship of litterfall to climatic factors. Mean July temperature was clearly correlated with needle litterfall. High temperature in July coincided with enhanced litterfall in the same and the next year. Litterfall enhanced litterfall in the same and the next year. Litterfall increased also after high temperatures during March-April, but only in the same year. In addition to these the litterfall had a 4-year self-dependency. This is approximately the same as the mean longevity of needles in the study area. Altogether the time series model we propose covers about 90% of the variance of the original time series.
在芬兰东南部的一片苏格兰松林中，通过落叶收集器对苏格兰松的针叶凋落物进行了为期24年（1962 - 1986年）的收集。1962年这些树木的平均树龄为111年。该林分是自然更新的，在其生长过程中只进行了少量的造林抚育措施。凋落物量呈现出很大的逐年变化，最小值为18克/平方米（1968年），最大值为213克/平方米（1973年）。凋落物量没有总体趋势，因此林分年龄在决定针叶凋落方面并不重要。我们使用时域时间序列分析（ARIMA）和标准气候数据（温度、降水量）来研究凋落物与气候因素之间的关系。7月平均温度与针叶凋落物量明显相关。7月的高温与同年及次年凋落物量增加相吻合。3 - 4月高温后凋落物量也会增加，但仅在同年。此外，凋落物量具有4年的自相关性。这与研究区域内针叶的平均寿命大致相同。我们提出的时间序列模型总共涵盖了原始时间序列约90%的方差。
