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Project title

Interrelationships between soil nitrogen, soil microbial communities and grassland stability in upland ecosystems.

Primary Funding Agency

Environmental Protection Agency

Co-Funding Organisation(s)

n/a

Lead Organisation

University College Dublin (UCD)

Lead Applicant

Nicholas Clipson

Project Abstract

Grasslands are a major ecosystem in temperate zones including Ireland and are valuable in terms of agriculture environment and ecology. In Ireland a common feature of upland areas such as the Wicklow Hills is plant-species rich semi-natural grasslands dominated by Agrostis capillaris. The past few decades have seen a trend towards agricultural intensification with i'improvementi of semi-natural grasslands a common occurrence. During improvement semi-natural grasslands are converted to plant species-poor mesotrophic grasslands dominated by Lolium perenne and Trifolium repens through re-seeding fertilisation and liming. Although intensification is central to the productivity of Irish grasslands concerns have been raised regarding the impacts of agricultural improvement on environmental processes particularly the basic functioning of grasslands. In this study a range of biochemical and molecular techniques were used to elucidate microbial community response to grassland management regimes both in field and microcosms situations. An area of typical Nardo-Galion (U4a) grassland at Longhill Co. Wicklow was chosen for part of this study. This site comprised mainly unimproved U4a grassland (soil pH 4.0 approx.) and an area of agriculturally improved Lolio-Plantiginion (MG7b) grassland (pH 6.5 approx.) enclosed in one corner with a gradient of improvement (zone of floristic transition) between. Community structure of the ammonia oxidising bacteria a key functional group in N-cycling was investigated. Differences in AOB community structure in U4a and MG7b grasslands and across the gradient were evident implying a response to improvement practices. Phylogenetic analysis also revealed that the majority of AOB species present belonged to the genus Nitrosospira. Further AOB analysis involved the use of two microcosm experimental systems investigating: (1) NH4NO3 addition plant species (A. capillaris and L. perenne) and lime; and (2) the effects of synthetic sheep urine plant species (A. capillaris and L. perenne) and time on AOB community structure. Microcosm studies revealed that addition of ammonium nitrate (NH4NO3) had a major influence over AOB community structure but plant species alone had little effect except when plant species interacted with NH4NO3. Lime appeared to have relatively little effect on overall community structure yet positively influenced the abundances of some AOB ribotypes. Synthetic sheep urine (SSU) addition also had an effect in determining AOB community structure with many AOB ribotypes responding negatively to SSU application. Notably plant species type was an important consideration as to the extent to which SSU affected AOB community structure.

Grant Approved

�75,000.00

Research Hub

Natural Environment

Research Theme

Sectoral Impacts on Biodiversity

Start Date

01/01/2003

Initial Projected Completion Date

n/a