Derelict land - a broken ecosystem ?
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Derelict land : "Land that has become damaged by industrial or other development and beyond beneficial use without treatment".
The natural colonisation by vegetation on the slopes of two adjacent oil-shale spoil heaps was investigated at Philpstoun, in West Lothian Scotland - 1992 & 2004.
North facing and south facing slopes opposite each other divided by a canal facing due north and south (see figures below) - very different although still hostile environments for plant life.
The vegetation on the northern spoil heap (south facing slope) was noted to be still a pioneer herb-grass community after 90 years, whereas the southern spoil heap (north facing slope) had developed a herb- rich community with woody perennials, after only 55 years.
The spent oil shale deposits at Philpston form two large spoil heaps and currently occupy about 10.5 ha of land bisected by the Union Canal.
Oil shale processing started here in 1884 and continued until 1935.
Spent shale deposits were dumped on the north bank of the canal - visible in the photograph above on the right hand side.
Note the variation in vegetation development over time on each slope.
Analyses of the "soil" substrate were undertaken to discover what underlying environmental factors
might contribute to the difference in vegetation cover on the two slopes in response to this hostile environment:
Particle-size analysis confirmed coarser substrate texture and higher soil-surface temperatures in the northern (s. facing) plot limiting germination and moisture retention.
Samples from plots on each slope showed pH to be uniformly high in the region of pH 8 - 10 although there was evidence of a thin surface acid horizon.
Exchangeable K, Mg, Ca & Na and available P & N concentrations were determined by atomic absorption sepectrometry and spectrophotometry respectively.
Factorial (NPK) glasshouse growth experiments were run to identify limiting nutrients.
Figure 1 (above) Variation in response of Lolium perenne to the addition of limiting
essential nutrients (NPK) grown on shale spoil taken from north slope of the study site.