Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790, Helsinki, Finland.
Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790, Helsinki, Finland.
Environ Pollut. 2020 Jun;261:114054. doi: 10.1016/j.envpol.2020.114054. Epub 2020 Feb 6.
Mosses take up nitrogen (N) mainly from precipitation through their surfaces, which makes them competent bioindicators of N deposition. We found positive relationships between the total N concentration (mossN%) of common terrestrial moss species (feather mosses Pleurozium schreberi and Hylocomium splendens, and a group of Dicranum species) and different forms of N deposition in 11-16 coniferous forests with low N deposition load in Finland. The mosses were collected either inside (Dicranum group) or both inside and outside (feather mosses) the forests. Deposition was monitored in situ as bulk deposition (BD) and stand throughfall (TF) and detected for ammonium (NH-N), nitrate (NO-N), dissolved organic N (DON), and total N (N, kg hayr). N deposition was lower in TF than BD indicating that tree canopies absorbed N from deposition in N limited boreal stands. However, mossN% was higher inside than outside the forests. In regression equations, inorganic N in BD predicted best the mossN% in openings, while DON in TF explained most variation of mossN% in forests. An asymptotic form of mossN% vs. TF N curves in forests and free NH-N accumulation in tissues in the southern plots suggested mosses were near the N saturation state already at the N deposition level of 3-5 kg hayr. N leachate from ground litterfall apparently also contributed the N supply of mosses. Our study yielded new information on the sensitivity of boreal mosses to low N deposition and their response to different N forms in canopy TF entering moss layer. The equations predicting the N deposition with mossN% showed a good fit both in forest sites and openings, especially in case of P. schreberi. However, the open site mossN% is a preferable predictor of N deposition in monitoring studies to minimize the effect of tree canopies and N leachate from litterfall on the estimates.
苔藓主要通过其表面从降水吸收氮 (N)，这使它们成为氮沉积的生物指示剂。我们发现，在芬兰低氮沉积负荷的 11-16 个针叶林中，常见的陆生苔藓物种（羽藓 Pleurozium schreberi 和 Hylocomium splendens，以及一组 Dicranum 物种）的总氮浓度（苔藓 N%）与不同形式的 N 沉积之间存在正相关关系。这些苔藓要么在森林内部（Dicranum 组），要么在森林内部和外部（羽藓）收集。沉积在现场作为总沉积（BD）和林内穿透雨（TF）进行监测，并检测铵（NH-N）、硝酸盐（NO-N）、溶解有机氮（DON）和总氮（N，kg hayr）。TF 中的沉积量低于 BD，这表明树冠从 N 限制的北方林的沉积中吸收了 N。然而，苔藓 N% 在森林内部高于外部。在回归方程中，BD 中的无机 N 最佳预测了开阔地的苔藓 N%，而 TF 中的 DON 则解释了森林中苔藓 N%的最大变化。森林中苔藓 N%与 TF N 曲线的渐近形式和南部样地中组织内自由 NH-N 的积累表明，在 3-5 kg hayr 的 N 沉积水平下，苔藓已经接近 N 饱和状态。地面凋落物淋出液显然也为苔藓提供了 N 供应。我们的研究提供了关于北方苔藓对低氮沉积的敏感性及其对进入苔藓层的树冠 TF 中不同 N 形式的反应的新信息。用苔藓 N%预测 N 沉积的方程在森林和开阔地都表现出很好的拟合度，尤其是在 P. schreberi 中。然而，开阔地的苔藓 N% 是监测研究中预测 N 沉积的更好指标，可以最大限度地减少树冠和凋落物淋出液中 N 对估计的影响。
