1. 2Laboratory of Bedrock Geology, Nature Research Centre
Dovilė Čiuldienė1, Gražina Skridlaitė2, Gailė Žalūdienė2, Cecilia Askelsson3, Kęstutis Armolaitis1
1Institute of Forestry of Lithuanian Research Centre for Agriculture and Forestry
2Laboratory of Bedrock Geology, Nature Research Centre
3 Department of Physical Geography and Ecosystem Sciences, Lund University
European Geoscience Union General Assembly, April, Vienna Austria
Soil Sustainability researches in Lithuanian alien forest stands
Mineralogical composition studies
Introduction
Mineral chemical compositions were determined in the Laboratory of Bedrock Geology of Nature Research Centre. They were analyzed in cooperation with dr. Gražina Skridlaitė. Soil samples were taken from B and C horizons in three replicates per forest stand. Mineral composition was analyzed by a Scanning Electron Microscopy (SEM) (Fig.1) (Table 2).
Results
Global warming could enlarge the expansion of Northern red oak and European larch into Lithuanian forests. At present, Northern red oak is considered as invasive species in Poland and at invasive stage in the Lithuanian forests (Riepšas and Straigytė, 2008). Meanwhile, European larch grew naturally in Lithuania in the sixteenth century and was reintroduced 200 years ago.
It is well documented that mineral weathering is one of the major factors which influences the soil nutrient stocks and
soil sustainability. But how these non-native tree species contribute to he mineral weathering process is still not understood.
Table 1. Mean dendrometric characteristics of the European larch and Northern red oak forest stands
Table 2. Mineral composition in the Northern red oak forest stands with adjacent perennial grassland and in the differently aged European larch plantations.
Fig. 1. Determination of K-feldspar using Scanning Electron Microscopy
However, the finest clay fraction mainly consisted of small secondary clay minerals and few primary minerals, therefore minerals were identified by the percentage of oxides (%) and mineral formula was adjusted using a mineral recalculation program “Mineral Recalculation Software”( uk / earth-research / Tindle / AGTWebPages / AGTSoft.html).
Aim of the study
The main goal of this study was to determine the mineral weathering rates in alien forest stands using a PROFILE soil chemistry model.
What did we find?
Study sites
B horizons of the studied glaciofluvial deposits contained in average 35% of quartz, 20% of both illite and muscovite; ~10% of feldspar and hornblende. C horizons consisted of 30% illite, 20% quartz and muscovite, and 10% hornblende and feldspar in average.
Depth of the clayey loam is one of the main factors influencing weathering rates.
However, a 30% higher sum of cations (Ca + Mg+ K) weathering rate in the soil under the Northern red oak than in adjacent perennial grassland was estimated. Meanwhile, the aforementioned parameter in the differently-aged European larch plantations does not differ much.
This study was carried out in the 47 and 157-year-old European larch (Larix decidua Mill.), year-old Northern red oak (Quercus rubra L.) plantations and in adjacent perennial grassland. The soils were Luvisols with clayey loam at different depths. The soils were developed from glaciofluvial deposits in both the studied plantations (Table 1). A
Model description
PROFILE model is a steady state soil chemistry model which is used to calculate a soil weathering rate (Warfvinge and Sverdrup, 1992). This model requires: data of climate (mean annual temperature & precipitation), chemical parameters of wet & dry atmospheric depositions, forest plantation dendrometric & chemical (wood, foliage litterfall) characteristics, soil physical parameters (density, textural classes) and soil mineral composition. The model estimates a weathering rate of Ca2+, Mg2+ and K+ through the soil profile (0-80 cm) in mmolc m-3 per year.
The PROFILE model was adopted in cooperation with dr. Cecilia Akselsson (Dept. of Physical Geography & Ecosystems Science, Lund university). B
Conclusions
The obtained results showed that over the 100 year the mineral weathering process was in equilibrium in the European larch plantations. However, the Northern red oak has accelerated mineral weathering rates in comparison with the adjacent perennial grassland.
Acknowledgement This research was funded by a grant (no. LEK-19/2010) from the Research Council of Lithuania and also was supplemented by the long-term research programme “Sustainable forestry and global changes”, implemented by the Lithuanian Research Centre for Agriculture and Forestry.
Fig. 2. The weathering rates of base cations in the Northern red oak (A) and European larch (B) plantations. The depth of clayey loam was in the Northern red oak and in European larch plantations.