Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Lancaster LA1 4AP, United Kingdom.
Environ Pollut. 2013 Aug;179:218-23. doi: 10.1016/j.envpol.2013.04.008. Epub 2013 May 18.
National-scale plant species richness data for Great Britain in 1998 were related to modelled contemporary N deposition (N(dep)) using a broken stick median regression, to estimate thresholds above which N(dep) definitely has had an effect. The thresholds (kg N ha⁻¹ a⁻¹) are 7.9 for acid grassland 14.9 for bogs, 23.6 for calcareous grassland, 7.8 for deciduous woodland and 8.8 for heath. The woodland and heath thresholds are not significantly greater than the lowest N(dep), which implies that species loss may occur over the whole range of contemporary N(dep). This also applies to acid grassland if it is assumed that N(dep) has substituted for previous N fixation. The thresholds for bog and calcareous grassland are both significantly above the lowest N(dep). The thresholds are lower than the mid-range empirical Critical Loads for acid grassland, deciduous woodland and heath, higher for bogs, and approximately equal for calcareous grassland.
1998 年英国全国范围的植物物种丰富度数据与当代模拟氮沉降（N(dep)）相关，使用断裂棒中位数回归来估计 N(dep)肯定产生影响的阈值。这些阈值（kg N ha⁻¹ a⁻¹）分别为酸性草地 7.9、沼泽地 14.9、钙质草地 23.6、落叶林地 7.8 和石南荒地 8.8。林地和石南荒地的阈值并不显著高于最低的 N(dep)，这意味着在整个当代 N(dep)范围内可能会发生物种损失。如果假设 N(dep)替代了以前的氮固定，那么酸性草地也适用。沼泽地和钙质草地的阈值均明显高于最低的 N(dep)。这些阈值低于酸性草地、落叶林地和石南荒地的中范围经验临界负荷，高于沼泽地，与钙质草地大致相等。
