Mass-loss rates from decomposition of plant residues in spruce forests near the northern tree line subject to strong air pollution

Abstract

Mass-loss rates during the early phase of decomposition of plant residues were studied for a period of 3 years in Norway spruce forests subjected to air pollution by Cu-Ni smelters on the Kola Peninsula, northwest Russia. Litterbags were deployed in two main patches of forests at the northern tree line, between and below the crowns of spruce trees older than 100 years. The study results demonstrated the dependence of the decomposition rates on the initial concentrations of nutrients and the C/N and lignin/N ratios in plant residues. Lower rates of mass loss in forests subject to air pollution may be related to low quality of plant residues, i.e. high concentrations of heavy metals, low concentrations of nutrients, and high lignin/N and C/N ratios. The increased losses of Ca, Mg, K, and Mn from plant residues in these forests compared to the reference were, probably, related to leaching of their compounds from the residues. The relatively high rates of heavy metal accumulation in the residues were most likely related to uptake of pollutants from the atmosphere, as well as to the lower mass-loss rates. The present study results demonstrate that the forest patchiness should be taken into account in assessment and predictions of decomposition rates in Norway spruce forests. Mass-loss rates of plant residues below the crowns of old spruce trees were significantly lower than those in the patches between the crowns. This was explained by the high C/N and lignin/N ratios in the residues of evergreens which contribute significantly to litterfall below the crowns and by lower soil temperature during winter and spring below the crowns. In addition, a lower amount of precipitation reaching the forest floor below the dense, long crowns of old Norway spruce trees may result in considerably lower washing out of the organic compounds from the residues. Lower mass-loss rates below the crowns of old spruce trees may be part of the evidence that the old-growth spruce forests can continue to accumulate carbon in soil.

Linking Forest Vegetation and Soil Carbon Stock in Northwestern Russia

“…In Sweden, the decomposition rate was much higher under birch than under spruce and pine resulting in lower carbon stocks in the organic horizon [50]. Similar differences in the mass-loss rates between the residues of birch leaves and conifer needles have been shown for forests in the northern taiga of Russia [38,48], but no statistical difference in carbon stock in the organic horizons was found between the birch and coniferous forests in this study. Although the carbon content and the C/N ratio were significantly lower in the organic horizons of birch forests, the horizon mass in birch and coniferous forests was comparable or the horizon mass was even greater in birch forests.…”

“…The dependence of the mass-loss rate on the initial concentrations of nutrients, the C/N and lignin/N ratios in plant residues have been demonstrated earlier for forests in northwestern Russia [38]. The mass-loss rate of bilberry leaves was 1.3-1.5 and 2-4 times higher than that of lingonberry and green mosses, respectively, which was associated with differences in the content of nutrients.…”

“…The higher carbon stock in the mineral layers of spruce forests compared to that of pine forests could be explained by the higher spruce needle litter quality, including a lower C/N ratio than in pine needles [38,48]. The amount of precipitation below the crowns of Scots pine trees, especially the amount of water flowing down along the trunks, was considerable, by several times greater compared to that in the Norway spruce forests in the northern taiga of Russia [49].…”

Sustainable Management of Central Appalachian Red Spruce

“…Similarly, soil organisms can also be negatively impacted from air pollution and acid deposition. A decline in soil organisms can impede leaf litter decomposition and impact nutrient cycling [53]. However, air pollution levels have declined since the Clean Air Act of 1970 [54].…”

Содержание Лигнина И Целлюлозы В Опаде И Подстилке Ненарушенных И Подверженных Техногенному Загрязнению Северотаежных Сосновых Лесов

“…Будучи устойчивым к разложению компонентом, лигнин влияет на скорость разложения опада и, следовательно, затрагивает механизмы взаимодействия с организмами почвы и преобразования питательных веществ [4]. Содержание лигнина и целлюлозы в химическом составе лесного опада, прежде всего, зависит от разновидности растений, но и климатические, и экологические факторы также могут привести к значительным качественным и количественным изменениям в опаде и подстилке [1,7].…”