The role of soil nutrients and physicochemical properties in a twenty-year brownfield grassland restoration experiment

Abstract

Agricultural intensification has caused considerable habitat and biodiversity loss
across global, regional and local scales. Species-rich hay meadows have readily been
replaced by less diverse plant communities as a result. Grassland restoration efforts
have long sought to reverse these effects through soil surface amendments that aim
to improve soil nutrient conditions and physicochemical properties. Brownfield sites,
including decommissioned landfills, present a unique set of environmental conditions
and remain under-utilised in ecological restoration. Few studies have assessed such
conditions, and the long-term effects of restoration treatments on soil conditions and
plant community composition. This study investigates the effects of grassland
restoration techniques on soil nutrients and physicochemical properties across a
twenty-year period, following the transfer of green hay from Cynosurus cristatus –
Centaurea nigra (MG5) grasslands to a clay-capped landfill. Various combinations of
compost-amendments and power-harrowing were established in treatment plots and
sampled alongside the MG5 donor plots. Soil nutrient concentrations were determined
using an aqua regia-method coupled with inductively coupled plasma optical emission spectroscopy (ICP-OES). Soil pH, Al, Fe, Na, K and P concentrations significantly differed over time, between treatments but correlated poorly with species diversity and richness. Nutrient availability was consistent with high biomass production, high soil organic matter content and low species diversity in compost-amended plots. Relieving soil compaction and increasing nutrient availability did not produce a plant community comparable to the species-rich donor plots. The overall success of restoration techniques was likely inhibited by underlying abiotic (e.g. soil structure, nutrient leaching) and biotic (e.g. microbial activity, biomass turnover, plant functional traits) factors that could not be quantified within the scope of this research. The interplay between these factors is exceedingly complex and understanding the synergy of plant-soil interactions requires comprehensive monitoring in future long-term grassland restoration projects.

Date of Award	17 Jun 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	David Watson (Supervisor)