Drainage ditches enhance forest succession in a raised bog but do not affect the spatial pattern of tree encroachment.

Joanna Nowakowska,Jerzy Szwagrzyk,Anna Gazda,Andrzej Tomski

doi:10.1371/journal.pone.0247760

Joanna Nowakowska, Jerzy Szwagrzyk + Show 2 more

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https://doi.org/10.1371/journal.pone.0247760

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Abstract

The study was conducted in the raised bog Kusowo (Baltic region, West Pomerania, Poland). Along a transect line crossing two open mires affected by forest succession we analysed tree age distribution. One of those mires had been drained in the past years and still retained some open ditches, while the other one was located far from the ditches. Every 10 meters along the transect line one tree was drilled at the root collar in order to determine its age. We also conducted phytosociological analyses and short-term water level measurements in the sample plots. We expected faster tree encroachment in the undisturbed part of the open mire. The results showed, that there were no significant differences in water table level and in soil moisture indicator values between the formerly drained and undisturbed open mire. There were also no statistically significant differences in tree encroachment between the disturbed and undisturbed mires. Location and the age distribution of the trees suggest that changes in the tree growth conditions cannot be directly explained by the general decreasing of water level in the bog, although periods following drainage works were associated with more numerous establishment of young trees, in the drained part of the bog as well as in the part not directly affected by drainage ditches.

Highlights

Peat bogs are among the most important ecosystems for water retention [1], they are able accumulate large amounts of water during heavy rains or snowmelt, and discharge the water slowly
The results showed, that there were no significant differences in water table level and in soil moisture indicator values between the formerly drained and undisturbed open mire
Water table level ranged from 0 to -45 cm; the average value was closest to the ground surface in case of the undisturbed mire, and slightly deeper and much more variable in the disturbed mire and in the whole area of the reserve (Fig 1A)

Summary

Introduction

Peat bogs are among the most important ecosystems for water retention [1], they are able accumulate large amounts of water during heavy rains or snowmelt, and discharge the water slowly. They play a large role in carbon storage [2, 3]; peat bogs and other wetlands at the global scale contain more carbon than forests do. There is an urgent need to understand the processes shaping their structure and species composition to maintain peat bogs in the landscapes strongly affected by global changes and by various forms of human.

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