Rapid beetle community convergence following experimental habitat restoration in a mined peat bog

The rate of recovery of invertebrate communities following habitat restoration has received little attention, despite the importance of invertebrates in ecosystem dynamics. In experimental trials in a mined peat bog in New Zealand, we compared the short-term rate of beetle community re-assembly at sites restored using management techniques varying in cost and effort to implement, and subsequently examined the long-term rate of beetle community convergence towards the ‘target’ community structure of an undisturbed peat bog. There was a direct relationship between the rate of beetle community re-assembly and the cost and effort applied to plant community restoration treatments (processed peat with no seed, processed peat with seed, and direct habitat translocation). To test the longer term rate of beetle community convergence following habitat restoration, we monitored beetle assemblages on a chronosequence of experimental habitat islands in which restoration was initiated 1, 13, 24, 25, 42 and 72 months previously. With increasing age, the plant community became more diverse and structurally complex, and beetle community composition converged rapidly on the target community structure of an undisturbed peat bog. Using a simple linear regression analysis on ordination axis scores, we obtained the quantitative prediction that the beetle community on restored islands would converge on the average community composition of an undisturbed peat bog within just 7-8.5 years. Our results clearly show that rapid invertebrate community re-assembly can occur in direct response to management techniques focused on establishing vegetation structure. Even the use of a low-cost restoration technique (processed peat with seed added) was effective in initiating remarkably rapid invertebrate community re-assembly in cutover peat bogs within 10 years.     

Earthquake rupture stalled by a subducting fracture zone

We showed that the rupture produced by the great Peru earthquake (moment magnitude 8.4) on 23 June 2001 propagated for approximately 70 kilometers before encountering a 6000-square-kilometer area of fault that acted as a barrier. The rupture continued around this barrier, which remained unbroken for approximately 30 seconds and then began to break when the main rupture front was approximately 200 kilometers from the epicenter. The barrier had relatively low rupture speed, slip, and aftershock density as compared to its surroundings, and the time of the main energy release in the earthquake coincided with the barrier's rupture. We associate this barrier with a fracture zone feature on the subducting oceanic plate.     

Land restoration management after topsoil mining and implications for restoration policy guidelines in New Zealand

A three-year field trial on an upland loessial soil (Belmont silt loam) in New Zealand investigated the effects of ripping, application of fertilizer N and grazing management on the recovery of some physical, chemical and biochemical properties of soil and pasture productivity following removal (mining) of topsoil. Removing the top 31 cm of soil by mining (all of the A horizon and part of the AB horizon) also removed most of the soil's labile organic matter fractions, and to a lesser extent its total organic matter. After three years, the microbial C and mineralizable N in the 0–10 cm depth of mined soil had reached 65 and 62 per cent of the corresponding levels in unmined soil. Ripping to a depth of 30 cm, application of fertilizer N and lenient grazing of the pasture failed to enhance the recovery of soil fertility. A soil sampling depth of 20 cm provided a reasonable basis to assess the microbial biomass and potential fertility. Pasture productivity was, on average, 30 per cent lower on mined land than on unmined land over the first three years after mining. Application of N proved uneconomic in terms of farm production, although a good pasture response to N fertilizer was obtained. The results from this and related trials are summarized as a series of recommendations for the monitoring and regulation of topsoil mining. An incentive regime is also recommended to encourage land owners and/or topsoil miners to use successful restoration techniques on topsoil-mined land. Copyright © 1999 John Wiley & Sons, Ltd.     

Structural stability of two Romanian soils as influenced by management practices

The effects of non-arable vs. arable land use as well as of wheeled traffic, crop rotation, manure applications and inorganic fertiliser application on soil stability parameters were investigated. The stability of a soil's structure was assessed by the dispersibility of clay in water, by measurement of the proportions of water-stable aggregates, and by the tensile strength of dry soil aggregates. An index of soil structural stability is defined and used. In general, there were trends towards increasing soil structural stability with non-arable agriculture, less wheeled traffic, crop rotations rather than monoculture, and fertiliser application.