substrate stability in Puerto Rico
Reforestation of landslides in Puerto Rico requires slope stabilization best provided by native climbing fern ( Gleichenai bifida , Dicranopteris pectinata) thickets that then delay forest growth for several decades . Direct tree planting is rarely successful on erosive surfaces even with fertilizer or organic soil amendments
substrate fertility iceland and Alaska
adding fertiliser does not immediately establish critical nutrient cycles and too much fertiliser may result in dominance by densely growing grasses or herbs that inhibit tree establishment through competition for nitrogen phosphorus water or light appropriate levels of fertiliser , combined with species that are short-live or grow less densely ,can act as nurse plants for seedling of later successional plants and facilitate succession . Legume introduced to increase soil nitrogen may benefit tree growth if their densities are kept low .Attempts to accelerate reforestation in iceland with commercial fertilisers or by planting tree seedlings into stands of the nonnative nitrogen -fixing lupine (lupinus nootkatensis) have shown some promise for nonnative tree such as sitka spruce (picea sitchensis)However ,overfertilisation or overreliance on lupine may lead to dominance by nonnative herbs or conifers in some part of iceland . Fertilisation of nonnative grasses on the Alaska pipeline corridor delayed recolonisation of native tundra species by several de cades low-fertility site where competition is reduced and where all key species are introduced initially have the greatest chance of restoration success
Amelioration of toxic conditions in miner in south Africa
Reforestation often involves addressing toxic site conditions . Landfills can have toxic liquids and gases mine tailings can have extreme PH values or toxic levels of metals in addition to surface compaction or erosion problem reforestation of dunes mined for various ores in south africa involved topsoil replacement windbreaks and sowing of various grasses that provided a nurse crop for slower-germinating native Acacia karoo trees from the seed bank. The acacia trees, promoted soil development through nitrogen fixation and were gradually replaced by larger native trees. In this case normal succession processes replaced early intensive manipulation . However it is often difficult to restore some semblance of predisturbance vegetation due to alterations in drainage , fertility and even topography . forests may remain stunted if they do colonise toxic sites, and reclamation goals are often more modest than in less toxic situations.
outline of tools
stabilising soil substrate : substrate stability is example , the following actions treat successively more serious erosion conditions on Puerto Rican landslides: mulch fertiliser. transplants silt fences contouring, jute cloth covers rock-filled gabions redirecting water flow and lining alternative drainage channels
Adding organic matter : Soil processes are key to successful restoration Beginning with severely disturbed substrates. Beginning with severely disturbers substrates organic matter additions disturbed substrates , organic matter addition are the fastest way to incorporate critical soil microbes .Earth worm additions, inoculation of mycorrhizae ,and additions of limiting nutrients (with the noted above) all potentially accelerate soil development and facilitate woody plant invasions or planting, especially in severely disturbed habits. However , mycorrhizae can act as parasites when nutrient limitations are severe. Minimal additions of topsoil or other source of nutrients and soil biota can reduce the risk of overfertilisation and dominance by early succession species that preclude tree establishment , Addition of nitrogen fixing plants can often benefit (but see substrate Fertility ,above
Reducing soil nutrients: Restoration can also involve reducing soil nutrients(via carbornrice straw sawdust , or sugar or additions of lignin-rice plant litter that immobilise nutrients) if the goal is a naturally infertile site for example ,native ohia (metrosideros polymorpha) forest in hawaii are out-competed by the introduced nitrogen fixing tree Myricafaya. In fact ,the whole succession pathway
on volcanic surfaces is altered to favour plants adapted to higher nutrients , particularly nitrogen
Restoration of native Hawaiian communities and succession processes will most likely require nutrient reduction treatments
Reducing toxic conditions. Toxic conditions can be ameliorated by bioremediation or the use of plants, mycorrhizae and microbes. Once toxin are reduced. restoration of native communities can begin. Additions of topsoil from late successional communities sometime combined with sludge . composted yard wastes or other concentrated organic matter source ,often accelerate succession
Arrested succession can be avoided by dense plantings of native species particularly ones that attract vertebrate dispersers
Biodiversity is key goal to restoration and its reestablishment implies a fully functioning ecosystem. If a diverse biological community resembling the reference ecosystem is self-sustaining . then landscape and successional dynamics have likely been incorporated. In addition, adequate substrate stability , drainage depth, and fertility have been achieved . However , restoration generally requires ongoing monitoring and strategic alterations.
Future Needs
we need to better understand the role that individual species. we have tended to focus on nitrogen and phosphorus from infertile soils. We have also neglected the nature and specificity of plant mycorrhizal associations and their role in restoration. Species that have similar functional attributes (fix nitrogen, grow early and fast in succession. Host key pollinators or dispersers have deep roots that break through compacted soils. etc.) may offer insights into better approaches to restoration similarly . keystone species (ones with ecosystem and community impacts disproportional to their biomass) could be important to restoration efforts must not ignore these new influences .
Restoration is essentially the manipulation of succession .yet we understand little about how ecosystem processes very through succession Temporal replacement of vascular plant species reflects and influences . generally , a reduction in nutrient availability .How can restorationists maximize their manipulation of these trends to favour desirable outcome? finally ,much emphasis is placed on above-ground and visually obvious criteria on above-ground and visually obvious criteria
for measuring restoration success when below-ground processes are ignored or only treated in a crude way(through fertilisation or stabilisation, for example) ,restoration suffers. The interplay of soil organisms with soil stability ,fertility and/or toxicity and with animals and vascular plant is perhaps the ultimate key to successful restoration