THE WORLD CONFERENCE ON ECOLOGICAL RESTORATION

2005 The World Conference on Ecological Restoration 25
Ecological restoration under a changing environment: atmospheric nitrogen
deposition and biological invasions
Allen E.B.
Department of Botany and Plant Sciences, University of California, Riverside, USA
Southern California shrublands are subject to anthropogenic N deposition, primarily from automobile
emissions, with levels up to 30 kg N ha -1 yr -1 . In addition, coastal sage scrub has been invaded by an understory
of Mediterranean annual grasses that increases flammability, promoting an increased frequency
of fire. Observations along an urban-to-rural N deposition gradient showed a loss of diversity of native
forb species from 67 to 16 species per ha, and an increase in exotic grass cover from 1% to 70%. Longterm
N fertilizer studies in a site with low N deposition confirmed the relationship between elevated soil N
and decline of native vegetation; after 10 years of N fertilization the native species began to decline in
abundance even without fire, with a concomitant increase in exotic grass cover. Restored stands of native
shrublands typically have an understory of exotic grasses, but these are comparable to local undisturbed
stands that also have weedy understories. However, both restored and natural stands are intrinsically
unstable because of their susceptibility to fire when grass biomass is high in soils with high N. Restoration
of the diverse native forb component will be even more difficult to achieve, and will require a reduction
in soil N. Ultimately the solution will be to strengthen air pollution legislation to reduce N emissions.
The time required for soils with elevated N to decline to natural background levels is currently unknown,
but will be required before restoration can be carried out successfully.
Keywords: exotic annual grasses, Mediterranean ecosystems, nitrogen deposition, stability.
Flow requirements as a tool for restoring brown trout population dynamics in
regulated streams
Alonso-González 1,2 C., J. Gortázar 2 , D. Baeza Sanz 2 , D. García de Jalón 2
1 Sciences Faculty. Catholic University of Ávila. Ávila. Spain
2 Ecohidráulica. Laboratory of Hydrobiology. Polytechnic University of Madrid. Madrid. Spain
Changes on stream flow regimes due to the function of small hydroelectric dams (known as “minihydros”)
are usually observed in mountain streams. These changes concern not only the intensity of flow but also
the variability and frequency of high and low-flow episodes. Former studies have showed the influence of
flow variability on the dynamics of a resident brown trout population, especially that related to the stream
flow regime during spawning, incubation and emerging periods. As these stages are known to determine
the population dynamics in further ages, stream flow variability appears to be a mayor factor on the regulation
of a wild brown trout population. Thus, mean flow discharge should not be the only parameter
taken into account when establishing ecological flow regimes in order to re-establish proper flow conditions
for the enhancement of altered trout populations in mountain streams. Setting ecological stream
flow regime characteristics, in base to conclusions obtained in a former study (Alonso-González et al.,
2004), is propounded as a tool for the restoration of degraded trout populations inhabiting mountain
reaches downstream hydroelectric devices. Case studies were conducted in a high mountain basin in
Central Spain (River Tormes) during 5 years showing that relationship between duration and frequency of
high low-flow episodes during egg incubation could be linked to young of the year recruitment and quantified
in terms of flow management units. Duration and frequency of flow discharges can be set so as to
reach desirable population levels in brown trout populations affected by hydropower flow regulation.
Keywords: Stream, flow regime, population restoration, brown trout.
Remediation of hydrocarbon contaminated soils in Mexico using vermicompost
Álvarez-Bernal D., E.L. García-Díaz, S.M. Contreras-Ramos, L. Dendooven
Laboratory of Soil Ecology, Dept. Biotechnology and Bioengineering, CINVESTAV-IPN, Av. Instituto Politécnico Nacional 2508,
C. P. 07000 México D. F., México
Contamination of soil with hydrocarbon occurs frequently in Mexico through oil spills. Restoration of
these contaminated sites might take a long time through deficiency of nutrients (N, P) for the petroleum
degrading micro-organisms thereby increasing a possible impact on the ecosystem. Waste water treatment
is increasing throughout Mexico generating large amounts of biosolids that are often incinerated
because they contain pathogens thereby loosing a valuable source of nutrients (N, P, and K) and organic
material. Vermicomposting or composting with earthworms reduces amounts of pathogens while maintaining
nutrient levels. Addition of vermicompost to hydrocarbon-contaminated soil might accelerate
their degradation so soil was amended with vermicompost and spiked with three different polyaromatic