Fine roots in stands of Fagus sylvatica and Picea abies along a gradient of soil acidification

doi:10.1016/j.envpol.2005.01.042

Environmental Pollution

Volume 137, Issue 3, October 2005, Pages 574-579

https://doi.org/10.1016/j.envpol.2005.01.042 Get rights and content

Abstract

Root length of naturally grown young beech trees (Fagus sylvatica L.) was investigated in 26 forest plots of differing base saturation and nitrogen deposition. The relative length of finest roots (<0.25 mm) was found to decrease in soils with low base saturation. A similar reduction of finest roots in plots with high nitrogen deposition was masked by the effect of base saturation. The formation of adventitious roots was enhanced in acidic soils. The analysis of 128 soil profiles for fine roots of all species present in stands of either Fagus sylvatica L., Picea abies [Karst.] L. or both showed a decreased rooting depth in soils with ≤20% base saturation and in hydromorphic soils. For base rich, well drained soils an average rooting depth of 108 cm was found. This decreased by 28 cm on acidic, well drained soils. The results suggest an effect of the current soil acidification in Switzerland and possibly also of nitrogen deposition on the fine root systems of forest trees.

Introduction

Soil acidification has accelerated in Europe during the last decades, not only in Northern Europe with its sensitive geology (Falkengren-Grerup et al., 1987) but also in Switzerland (Blaser et al., 1999, Braun and Flückiger, 2004). This is mainly due to anthropogenic input of acidifying compounds. The concern on acidification effects has led to the definition of critical loads for acid deposition which take into account the buffering capacity of the soils and the ecological effects (Sverdrup and Warfvinge, 1993, UN/ECE, 2004). The anthropogenic acidification is caused by sulphur and—with increasing significance—oxidized and reduced nitrogen (EMEP, 2001). The nitrogen compounds are, however, not only effective in acidification but also cause eutrophication of ecosystems, with corresponding ecological consequences (Achermann and Bobbink, 2003).

The effect of nutrient availability on the mass allocation to roots has been shown to depend on the type of nutrient: in birch and Norway spruce, N, P and S limitation lead to increased, Mn, and Mg and K limitation to decreased dry matter partitioning to the roots (Wikström and Ericsson, 1995). As acidification is reducing the availability of Mg and K, this pattern suggests a decreased allocation to the roots in acidified soils. Eutrophication by increased nitrogen deposition leads to excess nitrogen taken up which is stored in the form of amino acids and may then act as a sink for carbohydrates in the shoots (Näsholm, 1991, Wallenda et al., 1996). As a consequence, the allocation of mass to the roots may be decreased, especially in Mg-limited plants (Ericsson, 1995). The aim of the present study was to examine if the described effects can be observed in the field, being of ecological significance for water and nutrient uptake of trees.

Section snippets

Forest plots

The datasets presented here originate from a network of permanent forest observation plots in Switzerland (Braun et al., 1999) with pure stands of Fagus sylvatica (L.), Picea abies [L.] Karst. or both tree species in mixture, with an age range of 65–175 years and an altitude range of 260–1870 m asl. In some plots also Abies alba, Fraxinus excelsior, Quercus robur, Quercus petraea, Pinus sylvestris or Larix decidua make up a substantial proportion of the biomass. Soil samples were taken using an

Young beech trees

Neither total root length nor the root/shoot ratio were related to soil base saturation. However, the relative length of the roots with a diameter of <0.25 mm (finest roots) decreased with decreasing soil base saturation (Fig. 1, Table 2). A similar negative correlation with N deposition was not significant in the multivariate model (Fig. 2, Table 2) although it became significant when base saturation was removed from the model. This indicates a strong relationship between base saturation and N

Discussion

The results suggest that the current status of soil acidification and maybe also nitrogen deposition in Switzerland are affecting the roots of forest trees. The reason why the nitrogen effect is unclear is the large proportion of nitrogen compounds in acid deposition; soils with low base saturation are most often found in regions with high N deposition.

The rooting depth presented here cannot be attributed to a single tree species in mixed stands. Moreover, the uncensored dataset is too small to

Conclusions

Fine roots of Fagus sylvatica are impaired by low base saturation. Both the length of the finest, physiologically most active roots as well as rooting depth are decreased. A simultaneous effect of nitrogen deposition is masked by a correlation between soil acidification and N deposition. The observed effects may have consequences for tree stability.

Acknowledgements

The present work was supported by the governments of the cantons AG, BE, BL, BS, SO, ZH and ZG as well as by the Federal Office of Environment and Landscape. We thank B. Achermann, H. Balsiger, J. Froelicher, Dr H. Kasper, U. Meier, A. Morier, Dr M. Winkler and Dr R. Volz for their support and their interest in our work. Dr J. Heeb assessed most of the soil profiles. We thank also Dr Ch. Schindler for statistical advice and B. Rihm for modelling the nitrogen deposition.

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Fine roots in stands of Fagus sylvatica and Picea abies along a gradient of soil acidification

Abstract

Introduction

Section snippets

Forest plots

Young beech trees

Discussion

Conclusions

Acknowledgements

Forest Ecology and Management

Chemosphere

Forest Ecology and Management

Fine root turnover in forest ecosystems in relation to quantity and form of nitrogen availability: A comparison of two methods

Oecologia

Empirical critical loads for nitrogen

Bodenkundliche Kartieranleitung

Soil acidification in southern Switzerland between 1987 and 1997: A case study based on the critical load concept

Environmental Science & Technology

Bodenversauerung in Waldbeobachtungsflächen der Schweiz

Bulletin BGS

Growth of mature beech in relation to ozone and nitrogen deposition: An epidemiological approach

Water, Air and Soil Pollution

Forest damage by the storm “Lothar” in permanent observation plots in Switzerland: The significance of soil acidification and nitrogen deposition