Accelerating ecological restoration of drastically disturbed land

1
Accelerating ecological restoration of
drastically disturbed land by promoting early
establishment of microbial function Julie
Williamson, Davey Jones, Mark Nason, Edwin Rowe.
Institute of Environmental Science, University of
Wales Bangor, WALES. LL57 2UW.

• The effect of amendment type and time on soil
  properties under planted small birch was tested
  by Anova.
• Soil mineral N (NH4N NO3N) was much higher in
  the amended plots than the control potentially-
  mineralisable N and microbial N were far greater
  in the sewage-paper mix treatment and increased
  over time, compared with the other treatments.
  Basal respiration was also stimulated by the
  organic mix. A decrease in mineral N and basal
  respiration over time was consistent with
  ecological succession. Actinomycete CFUs were
  similar in all treatments (Table 2).
• Soil properties under planted birch amended with
  sewage-paper mix most closely resembled those of
  large natural birch trees relative to total C in
  each case, microbial biomass and basal
  respiration quotients were very similar. The
  range of actinomycete CFUs was similar in natural
  and planted birch (Tables 1, 2).
• Table 2. Soil biochemical properties of small
  birch trees planted in slate waste amended with
  organic or mineral amendments, sampled after 1, 7
  and 13 months. Numbers followed by the same
  letter within a row are not significantly
  different (P gt 0.05). n 9.

• Introduction
• Quarries and minesites are examples of extreme
  disturbance. Frequently, soil-forming material is
  scarce and ecological restoration is the only
  viable option. Establishing soil microbial
  function is critical and a key objective of our
  study. At Penrhyn slate quarry in North Wales we
  examined soil microbial function under
  populations of naturally established birch
  (Betula pubescens) with that under young planted
  birch.
• Hypotheses
• microbial biomass and nutrient cycling
  capability increase with tree size in natural
  tree populations
• organic amendments promote earlier
  establishment of microbial function than
  inorganic ones in planted trees
• organic amendments result in a soil similar in
  microbial and biochemical properties to soil
  under naturally established trees.
• Methods
• Naturally established groves of similar-sized
  birch (Fig. 1) growing in undisturbed slate waste
  were selected and ranked according to tree height
  (range 20 - 1000 cm). Six replicate groves were
  selected for each tree height class.
• Nearby, seedling birch were planted into slate
  waste with 1) no amendment, 2) slow-release NPK
  (151010) fertiliser prills or 3) digested
  sewage cake de-inked paper pulp mix. NPK
  fertiliser was applied to deliver N at a rate
  equivalent to the predicted N-mineralisation of
  sewage in the first year. Slate waste was sampled
  after one, seven and 13 months. There were nine
  replicate plots for each fertiliser level.
• Soil samples were taken from 0-15 cm depth.
• Results
• The effect of tree size in natural populations on
  soil properties was tested in two ways
• Anova showed that soil organic matter (total C),
  microbial biomass and microbial activity (basal
  respiration and amino acid mineralisation rates)
  all increased dramatically in large trees
  compared with small trees. Similarly,
  actinomycete (late-succession bioindicator)
  phospholipid fatty acid (PLFA) levels also
  increased (Table 1).
• Individual tree heights were closely related to
  their basal stem area (R2 90, data not shown).
• Regression analysis showed that variations in
  soil organic matter, microbial biomass and
  microbial activity, and actinomycete PLFA were
  closely related to the summed basal stem areas
  for each grove of naturally established trees.
  Actinomycete colony-forming units (CFU)
  correlated weakly with PLFA data (P 0.048) but
  were highly variable and not significantly
  related to tree size (Table 1).

• Conclusions
• Soil organic matter, microbial biomass and
  activity increased with tree size in natural tree
  populations. Naturally established birch provided
  a model against which we compared soil function
  under planted birch.
• The organic amendment effectively immobilised N
  in slate waste as microbial N and
  potentially-mineralisable N, whilst providing
  mineral N at a similar rate to NPK fertiliser.
  Immobilisation ensured a continued slow release
  of nutrients to sustain tree growth. The organic
  amendment was therefore suitable for ecological
  restoration.
• Soil properties under birch planted in slate
  waste amended with the organic mix were similar
  to those existing in slate naturally colonised by
  large birch. The organic amendment accelerated
  the process of soil genesis.
• Actinomycete PLFA proved a successful indicator
  of soil genesis in naturally established trees
  but actinomycete CFUs were too variable.
• Acknowledgements This is an EU LIFE Environment
  funded project, with industry sponsors A.
  McAlpine Slate Ltd. Thanks to Dr R. Bardgett
  (Lancaster University) and Dr P. Hobbs (Institute
  for Grassland and Environmental Research) for
  PLFA extraction and analysis.

Fig.1 A grove of medium-sized naturally
established birch trees.