Thimonier A, Dupouey J L, Bost F, Becker M
Unite d'Ecophysiologie forestière - Equipe Phytoécologie, Institut National de la Recherche Agronomique, 54280 Champenoux, France.
New Phytol. 1994 Mar;126(3):533-539. doi: 10.1111/j.1469-8137.1994.tb04252.x.
Surveys of ground layer vegetation are a reliable tool for monitoring spatial and temporal variations of the forest environment. In 1991, 47 vegetation plots first sampled in 1972 in a forest of the Lorraine Plain, North-East France, were resampled. This beech-oak forest had both acidic and calcareous soils depending on the thickness of alluvial deposits above the calcareous bedrock. The mean number of species per sample increased from 32 to 39 during this period and the frequency of nitrophilic species increased throughout the forest. On acidic soils, acidophilic species increased in frequency, while on calcareous soils there were no systematic changes. Multivariate statistical analysis clearly distinguished two gradients in this set of vegetation samples: acidity and nitrogen availability of soils. Along the first gradient, a shift of the plots towards a more acidic state occurred during the past 19 years on acidic soils only. Along the second one. a strong eutrophication happened on both acidic and calcareous soils, indicating an enrichment in nitrogen of forest ecosystems. Possible causes of these changes are discussed, namely sylviculture changes, aging of the stands and pollution. Atmospheric nitrogen inputs seem to be the most probable cause of eutrophication.
地面层植被调查是监测森林环境时空变化的可靠工具。1991年，对1972年首次在法国东北部洛林平原一片森林中采样的47个植被样地进行了重新采样。这片山毛榉 - 橡树林根据钙质基岩上冲积层的厚度，既有酸性土壤也有钙质土壤。在此期间，每个样本的平均物种数量从32种增加到39种，嗜氮物种在整个森林中的频率都有所增加。在酸性土壤上，嗜酸物种的频率增加，而在钙质土壤上则没有系统性变化。多变量统计分析清楚地在这组植被样本中区分出两个梯度：土壤的酸度和氮有效性。沿着第一个梯度，仅在酸性土壤上，样地在过去19年中向更酸性状态转变。沿着第二个梯度，酸性和钙质土壤上都发生了强烈的富营养化，表明森林生态系统的氮含量增加。讨论了这些变化的可能原因，即造林变化、林分老化和污染。大气氮输入似乎是富营养化最可能的原因。
