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DESARROLLO DEL DOSEL DE LEGUMINOSAS BAJO DIVERSAS CONDICIONES DE RESTAURACIÓN ECOLÓGICA EN BOSQUE DE PINO – ENCINO DE MICHOACÁN, MÉXICO.
... The different sizes responded to the need of determining long term effects that are not reported in this study. All plots, regardless of size, were sown with the same density of seeds per square meter, 0.32 gr/m 2 (Gómez-Romero, 2006), by dropping individual seeds following an equally spaced grid. In September 2008 (during the rainy season) plant species richness in the four areas was assessed, and presence as well as percent cover of the three most abundant species in each plot were recorded. ...
El establecimiento de plántulas es esencial para garantizar la permanencia de la mayoría de las poblaciones de plantas. Cuando el establecimiento de especies sucesionales tempranas se encuentra limitada, la dinámica de la regeneración de las comunidades de plantas puede alterarse, volviéndose un obstáculo para la práctica de la restauración ecológica. Este es el caso de Lupinus elegans (Fabaceae), una leguminosa arbustiva que facilita el establecimiento de otras especies vegetales. En este experimento se sembraron semillas de L. elegans en la misma densidad en un paisaje formado por campos agrícolas abandonados, para determinar las características del sitio favorables para establecimiento de esta especie. Con base en el análisis de árboles de clasificación, se determinaron las variables que explican el establecimiento de L. elegans, antes y después de eventos masivos de herbivoría por Zygogeomus trichopus, la cual es una tuza endémica, conocida como tuza de Nahuatzen, que redujo el establecimiento de L. elegans en un 40%. Los resultados indicaron que las orientaciones S-SO y SO-O, una densidad del suelo > 0.8047 g/cm3, una cobertura vegetal < 110% y pendientes > 11.5° favorecen el establecimiento de L. elegans y minimizan la mortalidad causada por la herbivoría por la tuza.
... The different sizes responded to the need of determining long term effects that are not reported in this study. All plots, regardless of size, were sown with the same density of seeds per square meter, 0.32 gr/m 2 (Gómez-Romero, 2006), by dropping individual seeds following an equally spaced grid. In September 2008 (during the rainy season) plant species richness in the four areas was assessed, and presence as well as percent cover of the three most abundant species in each plot were recorded. ...
Seedling establishment is essential to ensure the persistence of most plant populations. When the establishment of early successional species is hampered, the regeneration dynamics of plant communities may be altered, thus becoming an obstacle for ecological restoration practice. This is the case of Lupinus elegans (Fabaceae), a pioneer leguminous shrub of temperate forests that facilitates the establishment of other plant species. In this experiment, L. elegans seeds were planted in the same density within a landscape of abandoned agricultural fields, to determine site characteristics that favor the establishment of this species. By analyzing classification trees, the variables that explain L. elegans establishment were determined, before and after herbivory by Zygogeomus trichopus, an endemic gopher known as tuza de Nahuatzen, that prevented establishment of this species by 40%. The results showed that S-SW and SW-W orientations, a soil density > 0.8047 g/cm3, a vegetation cover < 110%, and slopes > 11.5° favored L. elegans establishment and minimized mortality caused by the gopher.
A network of permanent plots has been established on the subalpine slopes of Mount St. Helens. Plants in sites receiving only tephra or thin mud deposits survived the 18 May 1980 eruption and re-established themselves by late summer. Richness and cover on these substrates increased dramatically by 1981. Sites receiving thick cold mudflows have little vegetation after two growing seasons, and the few scattered individuals encountered are residual survivors, not seedlings. Subalpine sites destroyed by the direct blast, debris flow or pyroclastic flows had no surviving vascular plants and have yet to be recolonized. Such sites will require import or organic debris, nitrification and seed invasion for recovery to commence. Subalpine herb composition is changing on all sites. The magnitude of change, except on totally devastated sites, is proportional to the magnitude of the initial impact.-from Author
Tropical forests are endangered from deforestation and overexploitation. The objective of this study was to examine the effects of production practices of the tropical hardwoods, mahogany and Spanish cedar, on survival and early growth in the state of Quintana Roo, Mexico. Mahogany seedlings were grown in polybags and Spanish cedar seedlings were grown in bareroot nursery beds. In addition, seedlings of both species were grown in R–L containers for the outplanting comparison. Fertilization had a minor affect on seedling morphology, but the amount of shade had a strong affect on seedling morphology in the nursery. Following outplanting, initial seedling diameter influenced seedling survival and growth. Survival and growth of Spanish cedar was strongly correlated with initial seedling diameter. Seedlings larger than 4mm had excellent survival and good growth. Large diameter (>5mm) mahogany seedlings had exceptional growth, achieving over 4m in height at 57 months There appeared to be no interaction between stocktype and performance. Polybag mahogany seedlings were larger than containerized seedlings, and grew better. Conversely, containerized cedar seedlings were larger than the bareroot seedlings and performed better. Nearly all the bareroot cedar seedlings had died by 57 months, whereas 50% of the larger containerized seedlings lived. Growth of cedar was less than one-half that of mahogany. Successful reforestation of both species can be accomplished with just small improvements in seedling quality using the conventional systems. Larger seedlings survive and grow better, and on this site, mahogany was superior in performance compared to Spanish cedar.
Growth performance of nine native tropical tree species planted on mine spoil under two levels of NPK treatment was studied by measuring height and diameter. Of the nine species, four were leguminous. All the tree species responded positively to NPK fertilization; however, the impact on leguminous species was little compared to non-leguminous species. In general, the height/diameter ratio decreased from control to full-dose NPK treatment, suggesting that nutrient enrichment influenced the resource allocation pattern such that the diameter growth was favored. The log-transformed height-diameter relationships were significant for the three treatments in all the tree species. The slopes (β) obtained were compared with three different models of tree growth (i.e., elastic similarity, geometric similarity, and constant stress). Acacia catechu, Dalbergia sissoo, Gmelina arborea, and Azadirachta indica fitted the elastic similarity model, whereas Pongamia pinnata and Phyllanthus emblica followed the constant stress model. Tectona grandis was the only species that followed the geometric similarity model. In Albizia lebbeck and Terminalia bellirica, the β values were considerably lower (i.e., below 0.5) and these two species did not fit any of the three models of tree growth. In several cases the β values were considerably influenced by nutrient enrichment.
Key words: chemical fertilization, coal mine spoil, growth response, tree structure, tree volume, tropical tree species, height/diameter ratio.
Tropical forests are being cleared at an alarming rate although our understanding of their ecology is limited. It is therefore essential to design restoration experiments that both further our basic knowledge of tropical ecology and inform management strategies to facilitate recovery of these ecosystems. Here we synthesize the results of research on tropical montane forest recovery in abandoned pasture in Costa Rica to address the following questions: (1) What factors limit tropical forest recovery in abandoned pasture? and (2) How can we use this information to design strategies to facilitate ecosystem recovery? Our results indicate that a number of factors impede tropical forest recovery in abandoned pasture land. The most important barriers are lack of dispersal of forest seeds and seedling competition with pasture grasses. High seed predation, low seed germination, lack of nutrients, high light intensity, and rabbit herbivory also affect recovery. Successful strategies to facilitate recovery in abandoned pastures must simultaneously overcome numerous obstacles. Our research shows that establishment of woody species, either native tree seedlings or early-successional shrubs, can be successful in facilitating recovery, by enhancing seed dispersal and shading out pasture grasses. On the contrary, bird perching structures alone are not an effective strategy, because they only serve to enhance seed dispersal but do not reduce grass cover. Remnant pasture trees can serve as foci of natural recovery and may enhance growth of planted seedlings. Our results highlight the importance of: (1) understanding the basic biology of an ecosystem to design effective restoration strategies; (2) comparing results across a range of sites to determine which restoration strategies are most generally useful; and (3) considering where best to allocate efforts in large-scale restoration projects.
The field performance of six different plant types of Corsican pine ( Pinus nigra var. maritima (Ait.) Melville) was compared over the first 4 years after outplanting at four sites in Thetford Forest, East Anglia. The stock types differed in size, age and method of production and included conventional 1-year-old container seedlings raised in Japanese Paper Pots and Rigipots, 1½- and 2-year old seedlings raised in Japanese Paper Pots, as well as 2-year-old bare-root seedlings which either had or had not been undercut. Survival was high (> 87 per cent) for all types except the non-undercut 2-year-old bare-root seedlings. Height and stem diameter growth were generally low during the first year after planting, but by the end of the second year there were significant differences between individual plant types and sites. Analysis of height increments in the second year suggested that the 1½-year-old container seedlings raised in paper pots had recovered from planting check, whereas other stock types had not. However, average increments were not great enough to allow these 1½-year-old seedlings to overtake 2-year-old seedlings which were taller at planting. All stock types had apparently recovered from check in the third and fourth years after planting and were tending to grow on the same growth curve at each site with shorter seedlings producing smaller height increments. Thus initial seedling size and site factors, rather than method of production, were the most important factors determining future growth with the height advantage of taller seedlings at planting being maintained or increased in subsequent years.
Se estudia el papel de las leguminosas en la recolonización vegetal en un pinar quemado de la provincia de Albacete, a través de la frecuencia y cobertura de las especies en parcelas permanentes durante los cinco primeros años post-incendio. Comparaciones con áreas no quemadas indican que el fuego induce una elevada aparición de leguminosas anuales durante los primeros dos años postincendio. Entre todas las plantas aparecidas, la familia de las leguminosas fue la predominante durante los cinco primeros años post-incendio tanto en cuanto al número de especies como a la cobertura. Scorpiurus muricatus y Psoralea bituminosa fueron las especies más abundantes en la primera primavera después del fuego, alcanzando su máximo tamaño de población durante ese período. Un segundo grupo de especies (Trifolium sp. pl., Ornithopus compressus) mostró su máximo tamaño poblacional dos años después del fuego. La abundancia y cobertura de ambos grupos de especies decreció fuertemente entre el tercer y quinto año post-incendio.
Thermal shock is well known to be an important stimulus for the germination of soil-stored seeds in fire-prone plant communities. Nevertheless, while the overall germination response of different species is known to vary, the interaction between seed size and germination to a range of thermal-shock temperatures is poorly understood. This interaction may be important in regulating post-fire plant community establishment, since larger seeds are able to emerge from deeper within the soil profile than smaller seeds, and are therefore likely to be insulated against high above-ground temperatures by a deeper soil covering. In this experiment we examined how germination of eight co-occurring Western Australian fire-followers was influenced by thermal shock, and whether germination was significantly correlated with seed size. We found that small-seeded species not only showed enhanced germination at higher temperatures, but that their ability to germinate at higher temperatures was also greater than that displayed by larger-seeded species. These findings suggest that while seed size may be a useful general predictor of post-fire recruitment success, under different fire regimes the interaction between seed size, maximum seedling emergence depth, and the ability to withstand different thermal-shock temperatures is complex and may confound recent predictive models.
Initial colonization on the devastated Pumice Plains on the northern flank of Mount St. Helens, Washington, was monitored in two large grids seven seasons after the eruptions of 1980. The Pumice Plains is composed primarily of deep pumice, but contains a few large mudflow channels and numerous small erosion gullies. Over 45% of 1,600 10 by 10 m quadrats (Willow Spring site) and over 35% of 875 quadrats (Lupine Patch site) were devoid of vascular plants. The most common species were the weedy natives, Anaphalis margaritacea and Epilobium angustifolium, as well as Lupinus lepidus var. lobbii, a native with poor dispersal usually found at subalpine elevations. The first two species invaded by long-distance dispersal; a few individuals of the latter somehow established by 1981 from surviving rootstocks or seeds, and dense populations have developed from these survivors. Other species are typically found at low densities in favorable microsites. Species richness averaged 1.03 per 100 m² at Willow Spring and 1.82 at Lupine Patch. There are 32 species at Willow Spring and 26 at Lupine Patch. Species richness was concentrated in sites with high soil moisture and where topographic irregularities permitted accumulation of seeds. Colonists are an unusual mix of natives, drawn from an array of open habitats, and introduced weeds originating in fields and clearcuts at lower elevations. Colonizing species are primarily herbaceous, perennial, and wind-dispersed, though seedlings of woody “climax” species occur. Three distributional patterns are recognized: hydrophiles, found near streams; facultative hydrophiles, concentrated in wet sites but successfully colonizing upland sites; and species distributed at random or in xeric sites. We predict that the course of succession will continue to be slow and herbs-dominated. Patches of Lupinus lepidus at present do not appear to facilitate colonization. Colonists will continue to be rare and be confined to favorable microsites for several years.
Seedling density on permanent plots at five sites was monitored for the first four summers following the deposition of 4.5 to 15 cm of tephra from the 1980 eruption of Mount St. Helens. Because the old-growth forests at the sites were not destroyed by the volcanic eruption, the plots were under a normal tree canopy. Almost no seedlings established in 1980. By 1983 tree seedling density exceeded 35 m⁻⁻² at all sites. Tsuga heterophylla seedlings were most common, with Abies amabilis seedlings next in abundance. A dense layer of small trees may develop on the tephra and long-term forest dynamics could be affected. There was no successful invasion by species not already present in the stands. Seedlings of some forest herbs, especially Tiarella trifoliata, were common, but many other common forest species produced none. It is still problematical if or when these species will return to areas of the forest from which they were extirpated.
Thermoinhibition describes the inability of seeds to germinate at high temperatures, although germination proceeds immediately when the temperature is reduced below a certain threshold level. This phenomenon is distinct from thermodormancy, where some form of dormancy-breaking treatment is required before germination can proceed at the favourable temperature. Like seed dormancy, thermoinhibition is manifested in a number of different ways, ranging from simple high-temperature induced changes to the structures enclosing the embryo which prevent radicle emergence, to the interaction of a number of different factors, and probable expression of certain genes inhibitory to germination which may be temperature regulated. Thermoinhibition occurs in a large number of important crop species, so that an understanding of this phenomenon is both of scientific interest and practical importance.
(1) As a result of changes in mining operations and recessions in the china clay industry there are a number of abandoned waste tips in Cornwall ranging in age since last tipping from 16-116 years. These tips have been naturally colonized by vegetation. (2) The vegetation on a series of waste tips is described and four species-assemblages--two pioneer groups, an intermediate group and a mature woodland group--are identified. It is clear that succession to a woodland ecosystem can occur on these waste tips. (3) The accumulation of organic matter and nutrients was measured and is discussed in relation to successional development. The central role of nitrogen in these new environments is suggested, and the potential inputs to the nitrogen budget examined.
Retama sphaerocarpa is a leafless leguminous shrub found in most regions of Spain, frequently with a growth of herbs in its understorey which contrasts with the surrounding areas by its higher biomass and diversity. We examined the relationships between the shrub and the herbs underneath along a gradient of shrub age. A total of fifty individuals were selected to fit five age classes and shrub characteristics, soil properties and flora under the canopy were examined along the estimated chronosequence. All shrub size variables increased with time, as did the amount of nutrients stored by the shrub, but differences were often significant only between the three oldest classes. Concentration of nitrogen and phosphorus in photosynthetic stems remained constant, but nutrient pools in stem biomass increased with time. The shrubs changed the soil environment under their canopies with age by ameliorating soil texture, nutrient content and capacitance of water. The improvement was most pronounced between the two oldest classes (IV and V), and was probably due to the high biomass of perennial species in the understorey which increased the production of litter, and the interception of wind-blown dust. Plant diversity in the understorey increased with shrub age, likely due to a greater heterogeneity under larger canopies. Drought-resistant species, typical of the open areas between shrubs, were displaced from the centre of the understorey by taller, more mesic species over the age gradient. Retama sphaerocarpa shrubs benefited from the increase of resources in the understorey and showed a higher reproductive output with shrub age, but decreased at the beginning of senescence. The indirect interactions between R. sphaerocarpa and its understorey herbs could be considered as a two-way facilitation in which both partners benefit from their association.
Nitrogen-fixing plants, by altering the availability of soil N, potentially facilitate plant invasion. Here we describe how herbivore-driven mortality of a native N-fixing shrub, bush lupine (Lupinus arboreus), increases soil N and light availability, which promotes invasion by introduced grasses to the detriment of a native plant community. Soils under live and dead lupine stands contained large amounts of total N, averaging 3.14 mg N/g dry mass of soil (398 g/m2) and 3.45 mg N/g dry mass of soil (438 g/m2), respectively, over four years. In contrast, similar lupine-free soil was low in N and averaged only 1.66 mg N/g dry mass of soil (211 g/m2) over three years. The addition of N fertilizer to lupine-free soil produced an 81% increase in aboveground plant biomass compared to plots unamended with N. Mean rates of net N mineralization were higher under live lupine and where mass die-off of lupine had occurred compared to soils free of bush lupine. At all sites, only 2.5-4.2% of the total soil N pool was mineralized annually. Soil enriched by lupine is not available to colonists while lupines are alive. The dense canopy of lupine shades soil under shrubs, reducing average photon-flux density in late spring from 1725 μmol · m-2 · s-1 (full sunlight) to 13 μmol · m-2 · s-1 (underneath shrubs). Stand die-off due to insect herbivory exposed this bare, enriched soil. In January, when annual plants are establishing, average photon-flux density under dead lupines killed by insect herbivores was 370 μmol · m-2 · s-1, compared to the photon-flux density under live lupines of the same age, which averaged 83 μmol · m-2 · s-1. The availability of bare, N-rich patches of soil enabled nonnative annuals (primarily Lolium multiflorum and Bromus diandrus) to colonize sites, grow rapidly, and dominate the plant assemblage until lupines reestablished after several years. The N content of these grasses was significantly greater than the N content of the mostly native plants that occupied adjacent coastal prairie devoid of bush lupine. Between 57 and 70% of the net amount of N mineralized annually was taken up by introduced grasses and subsequently returned to the soil upon the death of these annuals. Even in the absence of further N inputs, we estimate that it would take at least 25 yr to reduce the soil N pool by 50%, indicating that the reestablishment of the native prairie flora is likely to be long term.
Previous research indicates that a number of factors may limit forest seedling growth in abandoned tropical pastures; however, mammalian seedling herbivory has not been previously reported as a major factor inhibiting tropical pasture restoration. Seedlings of four native tree species were planted in abandoned pasture in southern Costa Rica to test their suitability for reforestation. Overall, the stems of 64% of the seedlings were cut by rabbits and only 26% of the seedlings survived 2 years after planting. Those seedlings that were able to survive and resprout after cutting by rabbits showed much lower growth rates than uncut seedlings. This study suggests that mammalian herbivory may be a more important factor in tropical reforestation than previously assumed. Experimental tests over larger spatial and temporal scales are needed to ascertain the degree to which it limits reforestation efforts.
Derelict and degraded land destroys amenity, causes pollution and is a waste of productive land surface. Despite the worldwide activity to restore it there is an enormous backlog, which in England has increased since 1974. In the past much of this restoration was empirically based and not always successful. But natural ecosystems develop unaided on raw starting materials by natural ecological processes. A proper understanding of these has led to more reliable and inexpensive restoration techniques. At the same time we have come to realize that, because, at the start, the slate has been wiped clean, many different end points are possible. Derelict land is a challenge and opportunity for creative manipulation of our landscape. Yet what is achieved in practice is often pedestrian, unscientific and uneconomic. Often the simple treatments that would minimize the impact of industrial activity, and would set the restoration off early and in the right direction, are not carried out. Yet there are plenty of good examples of what can be done. It appears that once more we may be victims of the British failure in technology and imagination transfer. For this the fault seems to lie broadly, not only with planners, industrialists and government, for not always making sure something is done, but also with scientists, for not applying their ecological knowledge sufficiently to problems of hard practice.
Previous attempts to reverse the degradation of a coastal wetland and restore nesting habitat for an endangered bird showed that adding nitrogen could temporarily increase the height of Spartina foliosa, but not produce self-sustaining tall canopies. We asked if increased effort (up to five years of N fertilization) would shift canopy attributes across the hypothesized threshold. Thirty plots were treated with 0-5 yr of urea addition, and all were followed for 5 yr. Canopies were robust while urea was being added, but Spartina reverted to short stature soon after fertilization ended, supporting R. J. Hobbs and D. A. Norton's concept of an irreversible transition. However, specific outcomes depended on thechoice of response variable (six comparisons), the choice of reference data (initial conditions, same-year data, and pooled data), and the choice of statistical design (repeated measures vs. complete design), indicating the need to assess experiments thoroughly before making strong recommendations for management.
The nature and pattern of vegetation modification and environmental change in the tropical rain forest of southwestern Nigeria were examined. The study considered some biotic and edaphic parameters in two different areas. The changes were determined by comparing these parameters, with those in a tract of mature forest. The results depict the extent to which the soil-vegetation system, in the area has been disrupted, by both regulations and the activities of peasant farmers. The activities of the farmers, have resulted in degradation of the structural complexity, of the vegetation and a deterioration of soil quality. The changes depicted in this study could only be said to be a temporary disruption, if the area is allowed sufficient time to recover. Alternative environmental management strategies are suggested.
During the mid-1900s, most of the island of Puerto Rico was deforested, but a shift in the economy from agriculture to small industry beginning in the 1950s resulted in the abandonment of agricultural lands and recovery of secondary forest. This unique history pro- vides an excellent opportunity to study secondary for- est succession and suggest strategies for tropical for- est restoration. To determine the pattern of secondary succession, we describe the woody vegetation in 71 abandoned pastures and forest sites in four regions of Puerto Rico. The density, basal area, aboveground biomass, and species richness of the secondary forest sites were similar to those of the old growth forest sites ( . 80 yr) after approximately 40 years. The domi- nant species that colonized recently abandoned pas- tures occurred over a broad elevational range and are widespread in the neotropics. The species richness of Puerto Rican secondary forests recovered rapidly, but the species composition was quite different in com- parison with old growth forest sites, suggesting that enrichment planting will be necessary to restore the original composition. Exotic species were some of the most abundant species in the secondary forest, but their long-term impact depended on life history char- acteristics of each species. These data demonstrate that one restoration strategy for tropical forest in abandoned pastures is simply to protect the areas from fire, and allow natural regeneration to produce secondary forest. This strategy will be most effective if remnant forest (i.e., seed sources) still exist in the landscape and soils have not been highly degraded. Patterns of forest recovery also suggest strategies for accelerating natural recovery by planting a suite of generalist species that are common in recently aban- doned pastures in Puerto Rico and throughout much of the neotropics.
On the western slopes of Reunion Island, the trends in cropping systems for perfume pelargonium are causing serious erosion problems. This paper reviews the causes of these trends, presents the consequences of this deterioration, and assesses the ago-ecological solutions by means of cover plants and hedging with agroforest species. Firstly, the short term effects of cover plants (Lotus uliginosus, Pennisetum clandestinum) associated with the pelargonium crop are considered. Using rainfall simulation, it is shown that such associations have immediate effects in controlling erosion, although runoff is not significantly reduced. The more long-term effects of this type of cover are then compared with pelargonium monocuiture on bare soils, and with pelargonium in rotation with stable crops. The effect of hedging along plot boundaries is also observed. Descriptions of soil profiles highlight the advantages of plant cover, in improving soil structure and biological activity. Near hedges, the same tendencies are even more marked. Soil hydraulic conductivity, measured .in the various situations, confirms the complementarity of cover plants and hedges in association. The plant cover reduces erosion, with only a slight increase in water infiltration. At the same time, soil under hedges gives rise to very high water conductivity which should enable a large proportion of runoff water to be absorbed.
One thousand hectares in the south-east sector of Banks Peninsula are being managed for the protection and restoration of native vegetation and wildlife under a policy of minimum interference. The probable pre-human vegetation cover (1000 yr B.P.), inferred from current evidence and some historical records, was continuous forest, c. 55% of it podo-carp/hardwood forest and 45% Nothofagus forest. About 4% of this old-growth forest survives. The remaining area is a diverse mosaic of successional vegetation. Approximately 30% of the total area is closed-canopy second-growth native forest. About 53% is under scrub of naturalised gorse (Ulex europaeus) and broom (Cytisus scoparius). The remaining 13% is under pasture, fernland, and native tussockland. The predicted cover 50 years hence, assuming that fire can be excluded, is 95% second-growth native forest, 4% old-growth forest, and 1% tussock, shrubland, and scrub which will persist on bluffs. Successional pathways are diverse, involving both native and naturalised species.Monitoring of vegetational change to test predicted pathways and patterns began in October 1987. To date, observations show that in the absence of grazing animals and fire, regeneration of native forest is rapid, especially through gorse and broom scrub, and by the vigorous establishment of native serai hardwoods, especially kanuka (Kunzea ericoides).
Degraded hillslope areas are widespread in the Tanakami area located in Shiga Prefecture of central Japan as a result of more than 1300 years of human impact. Consequently, accelerated erosion rates and high storm runoffs have been major environmental problems there. To attempt to stabilize hillslopes and to reduce sediment and water discharges, extensive reforestation projects have been conducted since the 1870s. The vegetation recovery in the Tanakami area over a 51-year period was assessed using a geographic information system-based approach. The results showed that, in the areas where only hillside planting work was conducted, the percentage of bare slope area increased mainly due to the destruction of the vegetation cover on the forested slopes with gradients exceeding 30 degrees, and/or on southwest and northwest slopes. Moreover, the destruction of vegetation cover on steep slopes was seen to be most prevalent where hillside planting work was conducted without slope terracing. In contrast, in the area where both hillside planting and tending works were implemented, the bare slope area tended to decrease through the study period. Consequently, in 1988, there were only 1 per cent of bare slopes in the area where both hillside planting and tending works were implemented; in contrast the bare slope areas where only hillside planting work was conducted still occupied 12–17 per cent. These results imply that the reforestation practices that include hillside planting and tending works, or at least slope terracing, are necessary to prevent the destruction of the vegetation cover on steep southwest and northwest slopes. Copyright © 2002 John Wiley & Sons, Ltd.
Woodlands dominated by Eucalyptus salmonophloia (salmon gum) occur throughout the fragmented landscape of the southwestern Australian wheatbelt. These remnants are often degraded by livestock grazing and weed invasion and in many cases there is little or no understorey remaining and little or no regeneration of the dominant tree E. salmonophloia. There is a growing interest in developing techniques for restoring remnant woodlands. This study describes techniques for establishing seedlings of the dominant tree and perennial understorey species in E. salmonophloia (salmon gum) woodlands degraded by livestock grazing. The study tests the hypothesis that, in addition to the exclusion of livestock, management of weeds and reintroduction of plant species, restoration of plant species diversity will require techniques which mimic large-scale disturbances, reduce soil compaction, and restore soil water infiltration to suitable rates. Five-month-old seedlings of the dominant tree E. salmonophloia and four commonly associated woody shrubs (Acacia hemiteles, Atriplex semibaccata, Maireana brevifolia, and Melaleuca pauperiflora) were planted into areas that differed with respect to grazing (–rabbit/ −livestock and +rabbit/–livestock), tree canopy disturbance (+/–competition with tree canopy) and amelioration of soil compaction (+/–deep ripping). Following three growing seasons and two summers, the exclusion of rabbits had no significant effect on the survival and growth of planted species. As a consequence grazing treatments are pooled for the purposes of presenting the impacts of removing competition with adult trees and soil deep ripping. The removal of competition with adult E. salmonophloia trees significantly improved the survival of E. salmonophloia seedlings but did not improve survival of understorey species. Deep ripping the soil significantly improved the survival of both E. salmonophloia and the shrub A. hemiteles but did not improve the survival of other understorey species. In contrast to seedling survival, the removal of adult E. salmonophloia trees and deep ripping soil significantly increased the growth of all species. The results indicate that increasing levels of intervention will increase the chances of successfully restoring tree and understorey species diversity in degraded E. salmonophloia woodlands.
Most of the world's forest has been cleared, cultivated, and then often abandoned. In many instances these areas have changed to successionally arrested grasslands, shrublands, or fernlands maintained by frequent fires and high herbivore populations. Many studies have shown that various herbaceous, nitrogen-fixing legumes can protect soil surfaces, retain soil moisture, improve soil fertility, and retard ground fires. Our objective was to ascertain if some of these species can potentially inhibit herbivory and satisfactorily establish in these arrested grassland areas to serve as sites for reforestation. We evaluated the potential for four species of nitrogen-fixing legumes (Calapogonium mucunoides, Centrosema pubescens, Desmodium ovalifolium, and Pueraria phaseoloides) to establish on exposed soil within successionally arrested grasslands of Panicum maximum and Cymbopogon nardus in the central hills of Sri Lanka. Four different sites within rectangular grassland areas were cleared of graminoids and sown with seed of each legume. Half of each clearing was protected from browsing rabbits and porcupines, and half was not protected. After 6 months, certain plots were destructively sampled to determine dry biomass gain for each species and treatment. Analyses of variance were performed to test for differences among sites, treatments, and species. All three factors revealed differences, indicating that species must be matched to site. On sites with high amounts of herbivory, D. ovalifolium had the greatest dry biomass gain after 6 months of growth, possibly because of its relatively low nitrogen and moisture content. Where herbivory was absent, P. phaseoloides and C. muconoides had the greatest dry biomass gain. Dry biomass gain of all four legume ground covers was low on sites with lowest pH and nutrient concentrations. Under conditions of low relative fertility and low pH, establishment of the tested legumes failed. Though soil moisture availability was not measured, we speculate that these low fertility sites were also prone to drought. Findings support the site-specific establishment of legume species for purposes of reforestation and watershed protection in central Sri Lanka. This work is applicable to other regions particularly dominated by successionally arrested grasslands with similar circumstances in other parts of south and southeast Asia.
The most important problem in the restoration of closed landfills is the production of toxic gases by decomposition of refuse. Such gases affect the root system of plants growing on these sites. The aim of the present study was to assess the effects induced by landfill biogas contamination on germination and initial root growth of Vicia villosa (hairy vetch), Lotus corniculatus (birdsfoot trefoil), Trifolium pratense (red clover), and Trifolium repens (white clover). In laboratory conditions, simulated landfill and control gas were supplied to the seedlings. The composition of the simulated landfill gas used was: 16% O2, 8% CO2, 3% CH4, and 73% N2; a control gas was also tested (21% O2, 0. 035% CO2, and 78% N2). Percentage of germinated seeds was determined after 6 and 12 days from the starting date; at the same time qualitative assays of metabolic root functionality were also performed by using an agar technique in order to visualize changes in rhizosphere pH. At the end of the experiment, the length of the primary and secondary root was measured. Germination after 6 days was affected by the gas treatment; the landfill biogas caused a delay in germination with respect to the control in seeds of V. villosa and L. corniculatus. Root fresh weight and dry weight were significantly decreased by biogas treatment in V. villosa and T. repens. In contrast, root dry weight was higher in gas treated L. corniculatus and T. pratense compared to control seedlings. Total root system was significantly higher in treated T. pratense. The qualitative assay suggests, with the exception of T. pratense, a metabolic adjustment of the treated seedlings.
Key words: restoration, landfill biogas, legumes.
Heightening human impacts on the Earth result in widespread losses of production and conservation values and make large-scale ecosystem restoration increasingly urgent. Tackling this problem requires the development of general guiding principles for restoration so that we can move away from the ad hoc, site- and situation-specific approach that now prevails. A continuum of restoration efforts can be recognized, ranging from restoration of localized highly degraded sites to restoration of entire landscapes for production and/or conservation reasons. We emphasize the importance of developing restoration methodologies that are applicable at the landscape scale. Key processes in restoration include identifying and dealing with the processes leading to degradation in the first place, determining realistic goals and measures of success, developing methods for implementing the goals and incorporating them into land-management and planning strategies, and monitoring the restoration and assessing its success. Few of these procedures are currently incorporated in many restoration projects. The concept that many ecosystems are likely to exist in alternative stable states, depending on their history, is relevant to the setting of restoration goals. A range of measures, such as those being developed to measure ecosystem health, could be used to develop “scorecards” for restoration efforts. Generalizable guidelines for restoration on individual sites could be based on the concepts of designed disturbance, controlled colonization, and controlled species performance. Fewer explicit guidelines are available at the landscape scale, beyond nonquantitative generalities about size and connectivity. Development of these guidelines is an important priority so that urgent large-scale restoration can be planned and implemented effectively.
Summary • The effect of temperature on the minimum (base) water potential for seed germination (Ψb) was investigated in Daucus carota and Allium cepa and then described in two hydrothermal threshold models. • Germination was recorded over a wide range of temperatures and water potentials. • At temperatures of 15°C and below the base water potential for germination of the 50th percentile (Ψb(50)) was constant, but in both species, above a temperature (Td) around 16–19 °C, Ψb(50) increased linearly with temperature. Hydrothermal time (HTT) and virtual osmotic potential (VOP) models were altered so that the effective base water potential (Ψb(G,T)) for any percentile of the seed population (G), above Td, was given by Ψb(G)d + m(T – Td), where Ψb(G)d is the uncorrected base water potential for that percentile. The coefficient m is the slope of the linear relationship between Ψb(50) and temperature above Td. • Germination response to all temperatures and water potentials can be adequately described in both the HTT and VOP models by incorporating changes in Ψb(G,T) with temperature.
A number of experimental freshwater wetlands (150 m long × 75 m wide) with different ages since they were abandoned as rice fields, were used to analyze the prospects of multipurpose wetland restoration for such degraded areas. Nitrogen and phosphorus removal rate of the wetlands were determined monthly during the flooding season to estimate their efficiency as filters to remove nutrients from agricultural sewage. The number of wetland birds was recorded regularly to identify their habitat preferences. Both the temporal dynamics and changes in the spatial pattern of land use cover during the last 20 years were determined from aerial photographs and field analysis. All the wetlands appeared to be very efficient in the removal of nitrogen and phosphorus exported from rice fields. Usually 50–98% of the nitrogen and less than 50% of the soluble phosphorus were removed by the wetlands at any stage of restoration. Wetland birds preferred wetlands with intermediate plant cover for resting and sleeping activities better than rice fields and either very open wetlands or very dense ones with tall vegetation. Apart from the improvement in water quality and the restoration of natural habitats, restoration of wetland belts around lagoons will increase spatial heterogeneity and diversity of the landscape.
Restoration of ponderosa pine ecosystems results in altered stand structure, potentially affecting microclimatic conditions and habitat quality for forest organisms. This research focuses on microclimatic changes resulting from forest and landscape structural alterations caused by restoration treatments in southwestern ponderosa pine forests. Three microclimate variables—light intensity, air temperature, and vapor pressure deficit (VPD)—were monitored over two field seasons. Differences in microclimate between the treated forest and the surrounding untreated forest were measured, and microclimatic gradients across the structural edge between these two forest types were quantified. Restoration treatments increased sunlight penetration to the forest floor but did not significantly impact ambient air temperature or VPD. Mean values for air temperature and VPD did not differ significantly between treatments, although temperature and vapor pressure deficit did exhibit a trend in the morning; both variables were higher at the structural edge and in the treated forest during morning hours. Significant edge gradients were detected for air temperature and VPD in the morning and evening, increasing from the structural edge into the untreated forest. Our results show that microclimatic effects of these restoration treatments are generally modest, but the changes are more prominent at specific locations and during certain times of day. Because even modest changes in microclimate have the potential to impact a range of key ecological processes, microclimatic effects should be considered when forest restoration treatments at the landscape scale are being planned and implemented.
The Amazon Basin has suffered extensive deforestation in the past 30 years. Deforestation typically leads to changes in climate, biodiversity, hydrological cycle, and soil degradation. Vegetation succession plays an important role in soil restoration through accumulation of vegetation biomass and improved soil/plant interaction. However, relationships between succession and soil properties are not well known. For example, how does vegetation succession affect nutrient accumulation? Which soil factors are important in influencing vegetation growth? What is the best way to evaluate soil fertility in the Amazon basin? This paper focuses on the interrelationships between secondary succession and soil properties. Field soil sample data and vegetation inventory data were collected in two regions of Brazilian Amazonia (Altamira and Bragantina). Soil nutrients and texture were analyzed at successional forest sites. Multiple regression models were used to identify the important soil properties affecting vegetation growth, and a soil evaluation factor (SEF) was developed for evaluating soil fertility in Alfisols, Ultisols, and Oxisols, which differ in the ways they affect vegetation growth. For example, the upper 40 cm of soil is most important for vegetation growth in Alfisols, but in Ultisols and Oxisols deeper horizons significantly influence vegetation growth rates. Accumulation of vegetation biomass increased soil fertility and improved soil physical structure in Alfisols but did not completely compensate for the nutrient losses in Ultisols and Oxisols; however, it significantly reduced the rate of nutrient loss. Copyright © 2002 John Wiley & Sons, Ltd.
Each year, about 75 billion tons of soil are eroded from the world's terrestrial ecosystems. Most agricultural land in the
world is losing soil at rates ranging from 13 tons/ha/year to 40 tons/ha/year. Because soil is formed very slowly, this means
that soil is being lost 13–40 times faster than the rate of renewal and sustainability. Rain and wind energy are the two prime
causes of erosion from tilled or bare land. Erosion occurs when the soil lacks protective vegetative cover. Soil erosion reduces
the productivity of the land by loss of water, soil organic matter, nutrients, biota, and depth of soil. The greatest threat
to providing food for a rapidly growing human population is soil erosion. Abandoned, eroded agricultural land is replaced
by clearing forested ecosystems.
Facilitation is an important process during succession. Legumes often play a significant role as facilitators, particularly in primary succession, enriching the soil with nitrogen (N). The leguminous shrub Lupinus arboreus (Sims) can fix significant N on acidic, nutrient-poor soils. An apparent association between L. arboreus and Urtica dioica (L), which requires high concentrations of soil N and phosphorus (P), suggested that L. arboreus might facilitate colonisation by Urtica of nutrient-poor soils by increasing both soil N and P. I measured significantly higher concentrations of extractable soil P and higher values of soil pH beneath L. arboreus canopy, compared with areas between bushes, occupied by herbaceous vegetation. Litter inputs beneath L. arboreus were more than two and a half times higher in terms of mass of material and P and three times higher in terms of N, than in areas between bushes. This high litter input accounted for the higher soil P concentration and higher pH. It did not lead to higher soil organic matter content however, probably because high nutrient concentration in L. arboreus litter leads to rapid decay. A glasshouse trial showed that Urtica grew poorly on soil collected from areas between bushes of L. arboreus without the addition of supplementary N and P fertiliser, indicting co-limitation, by both N and P. Growth of Urtica on soil from beneath L. arboreus was more than four times higher than on soil from between L. arboreus. Amendment of the latter soil with N significantly increased growth of Urtica, but amendment with P did not, indicating that Urtica growth on this soil was not P limited, even when amended with N. Facilitation of colonisation of this site by Urtica therefore can be attributed to increased soil N and P, derived from litter of L. arboreus. However, in the field Urtica was only found beneath dead and senescent L. arboreus, suggesting a period of inhibition caused by shading, before senescence of L. arboreus allows light penetration to the nutrient-rich soil below.
Plant establishment on sites affected by major volcanic disturbances is limited by several factors, such as lack of suitable
microsites for germination and establishment in sites affected by tephra from volcanic eruptions. Even after long periods
of time, tephra deposited over un-vegetated areas (agricultural fields and other barren areas) lack closed vegetation cover
and in many cases late successional species. To assess limiting factors for plant establishment, a field survey in a tephra
deposit from the Paricutin volcano eruption (19°30′42.4′′N, 102°12′03.0′′) and greenhouse experiments were carried out. The
field survey determined the relationship between tephra depth and vegetation distribution. Greenhouse experiments determined
the effect of tephra depth on establishment and growth of two dominant species in the tephra deposit surveyed, Eupatorium glabratum and Lupinus elegans. Our results suggest that size and spatial distribution of vegetation patches is related to tephra depth in the field (77%
of the vegetation patches were on tephra 38.8cm deep or less and only 2% on tephra of more than 46.8cm). Under greenhouse
conditions, Eupatorium glabratum and Lupinus elegans height sharply decreased as depth of the tephra layer increased. Lupinus elegans plants growing in tephra less than 30cm deep had a mean weight of 10.56g (±0.53g) compared with 3.11g (±0.46g) for plants
growing in tephra more than 30cm deep. Our results suggest that tephra depth is a limiting factor for canopy development
in barren areas affected by tephra deposition.
Declining fallow length in traditional upland rice-based cropping systems in West Africa results in a significant yield reduction due mainly to increased weed pressure and declining soil fertility. Promising cropping system alternatives include the use of weed-suppressing legumes as short duration fallows. N accumulation, N derived from the atmosphere (Ndfa), weed suppression, and the effects on rice yield were evaluated in 50 legumes, grown at four sites in Côte d'Ivoire with contrasting climate, soils, and rice production systems. The sites were located in the derived and the Guinea savanna and in the bimodal and the monomodal rainfall forest zones. Legume and weed biomass during the fallow were determined at bimonthly intervals. Percent Ndfa by biological N fixation was determined by 15N natural abundance. Fallow vegetation was cleared and rice seeded according to the practice of local farmers and the cropping calendar. Weed biomass and species composition were monitored at monthly intervals. Legume fallows appear to offer the potential to sustain rice yields under intensified cropping. Biomass was in most instances significantly greater in the legume fallow than in the "weedy" fallow control, and several legume species suppressed weed growth. N accumulation by legumes varied between 1–270 kg N ha–1 with 30–90% Ndfa. Across sites, Mucuna spp., Canavalia spp., and Stylosanthes
guianensis showed consistently high N accumulation. Grain yields of rice which had been preceded by a legume fallow were on average 0.2 Mg ha–1 or about 30% greater than that preceded by a natural weedy fallow control. At the savanna sites where fallow vegetation was incorporated, Mucuna spp. and Canavalia ensiformis significantly increased rice yield. In the bimodal forest zone, the highest rice yield and lowest weed biomass were obtained with Crotalaria anagyroides. In general, the effects of legume fallows on rice yield were most significant in environments with favourable soil and hydrological conditions.
The growth and survival of ten hardwood tree species, planted in abandoned fields in southern Québec, over a range of soil and geological conditions, were analyzed in order to identify optimal site conditions for species growth. From a total of 23 experimental blocks, in which a total of 5750 seedlings was planted, we described six different soil types based on a cluster analysis of 12 soil variables. Factorial analysis linked species growth, in height and diameter, to gradients of soil nutrient richness and soil moisture. A statistical indicator of the degree of specificity of species toward soil variables was obtained by Kaiser's measure of sampling adequacy (Kaiser, 1970. Little jiffy, mark IV. Educational and Psychological Measurement 34, 111–117). After four growing seasons, heights of red ash, red oak and bur oak are markedly different among soil types. Best red ash growth occurred on the most nutrient-rich and humid soils, as opposed to red oak whose best growth occurred at the nutrient-poor and dry endpoints of the edaphic gradients. Bur oak differs from red oak in having good growth over a wide range of soil moisture conditions. Sugar maple growth was best on well drained and relatively nutrient-rich soils, but had high within-site variability. Yellow birch, with a low overall survival, attained its best growth in the most nutrient-poor, as well as above-average soil moisture conditions. The optimal edaphic conditions are weakly defined in the case of bitternut hickory and black walnut, the largest size of which was attained in below-average and in better-than-average soil nutrient conditions respectively. Silver maple performed equally well on the majority of soil types, but achieved exceptional growth on the wettest soil type. White ash and butternut growth also suggest a wide ecological amplitude, the first having good growth and the second having slow growth on all soil types. A synthesis of the experimental results is presented as a decisional chart for silviculturalists. Soil texture, moisture and pH are ordered according to their potential for the optimal growth of species. Identified geological, geomorphologic and pedological site constraints on species growth must be considered in the species selection process, especially for species which attain their best growth in narrower segments of the edaphic gradients.
Three experimental sites in Québec were planted with four different sizes of containerized black spruce seedlings (Picea mariana (Mill.) BSP). We examined the water stress experienced by each stock size of black spruce seedlings in relation to different competing vegetation covers and also the effect of the water stress on spruce growth during the first three growing seasons. The sites consisted of one abandoned agricultural field and two forest locations. Containers of sizes 45–110, 45–340, 15–700, and 12–1000 were employed to produce the four different sizes of spruce seedlings. At each site, the experimental protocol used a split-plot in a randomized complete block design, in which the presence of a competing vegetation cover (weedy and bare plots) was assigned to the whole plot, while a specific seedling size was assigned to each subplot. At each experimental site both the predawn xylem water potential Ψxp and the midday value Ψxm were measured three times during each of the first three growing seasons. Data were analysed as a completely randomized split-split-plot design, where selection of seedlings in time was considered as the whole plot. The competing vegetation tended to protect the spruce seedlings from excessive water loss, without depressing the soil-water potential (SWP) to the point of reducing the moisture available to the seedlings. Both Ψxp and Ψxm were found to decrease significantly with increasing initial seedling size. The increased water stress experienced by the large stock of spruce seedlings had an effect on the absolute growth rate (AGR) in height on only one experimental site. The AGR was impaired by the presence of a competing vegetation cover, but more severely for the smaller stock-size than the larger. The short-term effect of a competition should be based on radial growth; height growth and mortality are not early indicators of such effect. These results emphasize the need to produce a large stock of spruce seedlings with well-developed root systems and root growth capacity, even though only moderate water stress was observed during the first three years of plantation growth.
The hypothesis that tree plantations may catalyze the regeneration of natural forest biodiversity was tested through studies of floristic diversity and structure in fast-growing tree plantations in the Congo. Study sites included experimental and industrial plantations on poor sandy coastal soils near Pointe-Noire, and experimental plantations on clay soils near Loudima. The effects of plantations species, plantation age (in 6- to 20-year-old eucalypt stands), disturbance due to herbicide use and fire, proximity to natural forest, and soils on understory plant diversity were studied. These plantations were compared to the native savanna ecosystem and to adjacent natural secondary forest stands. Vegetation diversity was assessed through analyses of floristic composition, species richness and frequency. Forest species were dominant in the understory of most plantations, especially in the older stands. However, the forest species established in plantation understories were quite different from those from adjacent natural forest stands. Premna lucens, Psorospermum tenuifolium and Psychotria cf. peduncularis were the most important forest species found in most eucalypt plantations and in Pinus caribaea and Acacia auriculiformis plantations. Alchornea cordifolia, Anthocleista nobilis, Barteria nigritiana and Bertiera cf. batesii were also important. The savanna species Eriosema erici-rosenii, Annona arenaria and Loudetia arundinacea were encountered in many plots. Herbaceous species were dominant in the younger and disturbed plantation stands.
Only recently has the importance of positive interactions among plant species in structuring natural communities been supported by experimental evidence. Most studies have focused on interactions between a pair of species at a single-life history stage. In this study positive interactions between a woody nitrogen-fixing shrub(Myrica pensylvanica)and two herbaceous sand dune species (Solidago sempervirens , Ammophila breviligulata) which frequently grow beneath shrub canopies are examined throughout the lifecycles of the herbaceous species. Comparisons of S.sempervirens and A.breviligulata growing beneath and outside M.pensylvanica shrubs show that plants growing in association with shrubs are larger, are more likely to flower, produce greater numbers of flowers and seeds, have high midday xylem water potentials, have higher tissue nitrogen concentrations, and have higher photosynthetic efficiencies. Measurements of environmental condiitons show that areas beneath the shrubs are more shaded, have lower soil temperatures, and have higher soil nitrogen levels. The results from experimental manipulations designed to test the effects of Myrica shrubs on understory species suggest that the observed differences in plant performance are stongly influenced by canopy shading and soil nutrient enrichment associated with the shrubs. The results demonstrate that M.pensylvanica facilitates growth, reproduction, and recruitment of S.sempervirensand A.breviligulata growing beneath it. This study, one of the few to examine positive interactions at different life-history stages, supports previous predictions that positive interactions may be particularly important in plant communities characterised by physiologically stressful conditions.
La sucesión forestal: fundamento ecológico de la silvicultura
- E Jardel
- L Sánchez-Velázquez
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silvicultura. Ciencia y Desarrollo 14(84): 35-43.
Restauración ecológica y Rehabilitación de áreas. La biodiversidad en Michoacán: Estudio de Estado
- R Lindig-Cisneros
- G Villaseñor
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Michoacán: Estudio de Estado. Villaseñor G., L. E. (editora). 2005. Comisión
Nacional para el Conocimiento y Uso de la Biodiversidad, Secretaría de Urbanismo y
Medio Ambiente.Universidad Michoacana de San Nicolás de Hidalgo. México.194
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Dinámica y uso de los recursos forestales de la región Purépecha. El papel de las pequeñas empresas artesanales. GIRA, México
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región Purépecha. El papel de las pequeñas empresas artesanales. GIRA, México. 195
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The role in lupine in sucession an Mt
- W F Morris
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facilitation or inhibition? Ecology 70:6997-703.
Comisión Nacional para el Conocimiento y Uso de la Biodiversidad
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