Natural Vegetation Recovery Research Articles

Effects of vehicle track formation on soil seed banks in grasslands with different vegetation in the Mongolian steppe

Dirt road formation caused by the passage of off-road vehicles can lead to intense disturbances in underdeveloped regions. The natural recovery of vegetation after the abandonment of dirt roads depends largely on the soil seed banks, although the amount of damage to the seed bank composition, which determines the natural revegetation potential caused by dirt road formation, is unclear. We investigated the vertical distributions of seed banks in two grasslands in the Mongolian steppe with different above-ground vegetation, i.e., annual- and perennial-dominated grasslands, and we evaluated the effects of dirt road formation. The soil seed banks mostly comprised annual species of Chenopodium, irrespective of the above-ground vegetation, and the soil seed banks were larger in the annual grassland than in the perennial grassland. However, vehicle track formation removed the upper soil layers, which contained an abundance of buried seeds; therefore, the seed banks were small below the tracks, and almost the same size in the two grasslands. Our results suggest that natural revegetation through seedling emergence depends largely on annuals in the Mongolian steppe. Vehicle track formation damages seed banks severely; thus, artificial manipulations such as seeding or transplanting are required to facilitate the rapid revegetation of abandoned roads, irrespective of the above-ground vegetation.

Recovery of Native Plant Communities following Control of Terracina Spurge (Euphorbia terracina): Three Case Studies from South-west Western Australia

Terracina spurge or Geraldton carnation weed ( Euphorbia terracina ) is an invasive weed that impacts native plant communities across southern mainland Australia and in the United States (USA), including southern California and Pennsylvania. There are, however, few published accounts of appropriate control techniques or recovery of native vegetation following removal of this species. We report here on the results of three adaptive management projects investigating effective control of Terracina Spurge and subsequent recovery of Banksia woodlands, coastal shrublands, and sedgeland communities in the Swan Coastal Plain bioregion, south-west Western Australia. In Banksia woodlands the herbicide metsulfuron-methyl (600g/kg) (Brush-Off® ) in combination with hand removal of adult plants was effective at controlling Terracina spurge. Although there was some initial off target damage to native flora, after five years of repeated application the Banksia woodland within the treated area is regenerating. In sedgelands of the Holocene dune swales and in coastal shrublands 750g/kg triasulfuron (Logran® ) was very effective, reducing Terracina spurge populations significantly in the first two years. The treatment resulted in little damage to native flora. At both sites a significant difference in species abundance between years was attributed mostly to a decrease in the cover of Terracina spurge but also an increase in cover of several species of native flora. The results indicate triasulfuron is an effective tool for the management of Terracina spurge in coastal plant communities potentially leading to the protection and restoration of significant areas of the conservation estate within the Swan Coastal Plain bioregion and beyond.

Response of soil CO2 efflux to water addition in temperate semiarid grassland in northern China: the importance of water availability and species composition

Knowledge of the effects of water addition and the composition of plant species on soil CO2 efflux (SCE) and its temperature sensitivity (Q10) in temperate semiarid grassland is essential for understanding carbon (C) cycles and for evaluating future C balance. Our objective was to examine the seasonal variability of SCE and its sensitivity to temperature in response to water addition in four grasslands on the northern Loess Plateau. SCE was measured during the growing seasons (April–October) in 2010 and 2011 in the four grasslands dominated by different species: purple alfalfa (ALF), bunge needlegrass (BNE), degraded alfalfa (DALF), and fallow land for the recovery of natural vegetation (NAF), in two treatments: water addition (50 mm year−1) and a control. Water addition consistently increased mean seasonal SCE by 8.4–33.8 % across the four communities, attributable to enhanced plant growth, root and microbial activities, and respiration. The magnitudes of the positive effects, however, varied with plant community and measuring period. Soil temperature was primarily responsible for the seasonal changes in SCE in both the control (37–63 %) and the watered (40–75 %) plots. The addition of water increased the Q10 of SCE by 11.0 %, 14.4 %, and 13.4 % for ALF, DALF, and NAF, respectively, but had no significant effect on the Q10 for BNE. We therefore conclude that water addition can significantly increase SCE and may stimulate the sensitivity to temperature in semiarid grassland. The composition of plant species may regulate the dependence of SCE on water and temperature.

To seed or not to seed in alpine restoration: introduced grass species outcompete rather than facilitate native species

Anthropogenic disturbance in alpine ecosystems is on the increase, and knowledge is needed about restoration methods and their long-term effects in these environments. Sowing seeds from introduced grass species has been a common approach to encourage the growth of new vegetation, but there is disagreement over the long-term effects. Little is known about native alternatives and their ability to promote establishment of native vegetation. We compared vegetation cover, species richness and soil conditions in a long-term field experiment in seeded sites and unseeded reference sites 21 years after seeding with a commercial seed mixture. We also tested germination and establishment of an introduced grass Festuca rubra and its native congener Festuca ovina and their effect on the establishment of the native shrub Betula nana in a greenhouse experiment in different soil types. In the long-term field experiment, the introduced Festuca species outcompeted rather than facilitated natural vegetation recovery in the seeded sites. Total vegetation cover was significantly higher in the seeded sites, but native vegetation cover and species richness were significantly higher in the unseeded sites. In the greenhouse experiment, the native F. ovina showed a tendency to facilitate the seedlings of B. nana in contrast to the introduced F. rubra, which clearly suppressed B. nana seedlings. However, seedlings of the native shrub B. nana performed best when seeded without any of the species that are presumed to be facilitators or nurse species. Suppression by seeded grass was stronger on commercial peat soil compared to fine mineral soil and coarse soil. When seeding is used in restoration efforts, it is important to choose species that do not compete strongly with the natural vegetation. Fertilization and other soil improvements may even favor strong seeded competitors at the expense of native species. Hence the combination of seeding introduced species and improving the soil may delay successful alpine natural vegetation recovery.

Increased inorganic nitrogen leaching from a mountain grassland ecosystem following grazing removal: a hangover of past intensive land-use?

Heathlands and grasslands occur in montane regions, naturally or due to anthropogenic land-use. These are typically nutrient-poor but exposure to elevated nitrogen deposition and intensive livestock grazing causes large-scale ecological change. We studied the long-term implications of grazing removal on soil and drainage water biogeochemistry and the implications for nitrogen cycling in 50-year replicated grazing exclosures on a montane grassland exposed to high rates of ambient nitrogen deposition. Evidence of ‘ecosystem recovery’ represented by successional change from graminoid to shrub-dominance after cessation of grazing was not reflected in the soil biogeochemistry. Cessation of grazing had a negative impact, with increased soil extractable and soil solution nitrate concentrations; an apparent shift towards a more nitrogen-rich, bacterially dominated microbial community; and the acidification of soils and leachate. The increase in nitrate leaching appears to have been counterbalanced by a decrease in dissolved organic nitrogen leaching, approximately maintaining the overall nitrogen balance of the system, whilst apparently altering ecosystem functioning. High rates of organic matter cycling and inorganic nitrogen uptake in grazed grassland may have sustained ecosystem N limitation under elevated nitrogen deposition. Grazing removal caused long-term over-supply of nitrogen from mineralisation of enriched organic matter, exacerbated by continued high nitrogen deposition, exceeding the uptake demand of heath vegetation and resulting in nitrification and nitrate leaching. This disequilibrium between vegetation and soil following grazing removal has implications for restoration after periods of intensive grazing. Grazing may not simply leave a legacy of nutrient enrichment but its cessation may trigger nitrogen saturation and soil and freshwater eutrophication and acidification which counteract the immediate benefits of natural vegetation recovery. Long term, nitrogen saturation of abandoned grasslands is likely to reduce ecosystem resilience to invasion by nitrophilous species, pathogen attack and vulnerability to environmental pressures such as climate change. We conclude that partial and/or phased reduction in grazing levels may permit the more synchronised recovery of soils and vegetation, thereby avoiding imbalances between nitrogen supply and nitrogen demand and detrimental ecological effects.

露天煤矿区生态风险受体分析—以内蒙古平庄西露天煤矿为例

煤矿露天开采行为导致矿区岩体剥离、植被破坏和土壤物理化学性质的巨大改变，对采矿区土壤生态系统造成剧烈扰动，使其成为水土流失、滑坡等矿区潜在生态风险的主要受体。以内蒙古平庄西露天煤矿区土壤生态系统为研究对象，通过分析矿区主要景观单元的土壤理化性质、植被演替规律与土壤线虫群落结构特征，研究其生态脆弱性分布与变化规律。结果表明矿区土壤系统的成熟度与稳定度与其形成年限具有相关性，但与农田生态系统和未受扰动的自然生态系统相比，煤矿开采区与排弃物堆放区的土壤结构较差、土壤肥力偏低、动、植物群落成熟度和稳定性较差。受土壤养分条件及土壤微生物数量等因素的限制，其植被自然恢复速度慢，生态系统脆弱，需通过土壤改良、合理选种适生植物、改善土壤养分条件，促进植被重建。;Open-pit coal mining causes rock mass peeling, vegetation damage and of phy-chemical properties change of soil. Severe disturbance makes soil system in mining area the main receptor of soil erosion,landslide and other potential ecological risks. In this study,soil ecosystem of Pingzhuang western open-pit coal mining area in Inner Mongolia was the research object. To find the distribution and changes of ecological fragility,the main phy-chemical properties of soil,the vegetation succession and the characteristics of soil nematode community structure in mining area were analyzed on landscape units. The results indicate the relevance between maturity and stability of soil systems and their lives. Compared with the agro-ecosystem and natural ecosystem undisturbed,however,mining areas and dumping sites have poor soil structure, low soil fertility and less maturity and stability of animal and plant communities. Due to the restriction factors such as soil nutrient condition and microbial quantity,natural recovery of vegetation in mining area is slow and the ecosystem is fragile. Soil reformation,plants selection and nutrient conditions improvement should be suitable to reconstruct vegetation.

Efficacy of bark strands and straw mulching after wildfire in NW Spain: Effects on erosion control and vegetation recovery

Slope stabilization treatments like mulching are frequently used to reduce runoff and erosion following high severity wildfires, but they may also affect native vegetation recovery or facilitate exotic species invasion. However, the effectiveness of many treatment options has not been well established, in particular, the use of wood-based mulches.In this study we assessed the efficacy of different methods of reducing soil erosion and the effects on vegetation recovery after a severe wildfire in Galicia (NW Spain). We compared the following treatments: straw mulch (2.0Mgha−1), bark strands mulch (3.5Mgha−1) and control (untreated). The straw mulch provided an initial ground cover of 70% and the bark strands mulch, 57%.During the first year after wildfire the mean sediment yield in the control plots was 5.4Mgha−1. In this period, the mean sediment yields in the treated plots were significantly lower than in the control plots (0.7Mgha−1 in the bark strands mulched plots and 0.5Mgha−1 in the straw-mulched plots). The bark strands mulch decayed very rapidly, so that six months after its application the mean cover had decreased to about 27%. Straw mulch persisted longer, and the mean cover was more than 40% at the end of the first year after fire.Soil erosion decreased sharply during the second year after wildfire with low and similar erosion yields in all cases.Straw mulching favoured vegetation cover recovery. Mulching did not have a significant effect on seedling emergence. Vegetation regrowth was very rapid and the total vegetation cover was about 70% at the end of the study.Mulching did not affect species composition, and there was also no evidence of the presence of any exotic species.The results indicate the feasibility of mulching with straw to reduce soil erosion after fire. The efficacy of bark strands mulch in controlling soil erosion losses during the first year after fire was probably due to the fact that most rainfall occurred when the cover provided by the mulch was maximal (i.e. before it decayed). This may indicate a limitation for soil protection the first year after fire when the erosion risk is highest.

Recovery rate of vegetation in the tsunami impacted littoral forest of Nicobar Islands, India

The interplay between disturbance and recovery has implications in understanding the dynamics of tropical forests. The high magnitude earthquake of 9.3Mw and the subsequent tsunami in Indian Ocean had severe impacts on the coastal biodiversity of Southeast Asia. Close vicinity of the Nicobar Islands to the earthquake epicenter has been attributed to the maximum damage levels in terms of coastal biodiversity as well as human lives. Littoral forests that are important for the survival of many endemic flora and fauna of Nicobar Islands were badly affected. We studied the recovery of littoral forest tree community from 25 sites on eight islands in Nicobar group during 2009–2011 where the tsunami had wiped out all the vegetation. Changes in woody plants⩾3.2cm Diameter at breast height (DBH) were monitored for 62 plots of 50×20m (0.1ha.) for two consecutive years, 2009–2010 and 2010–2011. Two kinds of regenerating vegetation were identified namely, Rubble-affected Vegetation (RV) where substrate was found deposited with sand and coral rubbles during tsunami and Loamy Vegetation (LV) where the substrate remained as sand-loamy without any deposition. A total of 5528 tree individuals of 120 species and a total of 5843 tree individuals of 127 species were recorded during the first and the second year, respectively. Species diversity was high in the second year for both the vegetation types, where LV with 120 species had higher species diversity than RV (43 species). The species composition differed among vegetation types. Macaranga peltata and Ficus hispida were dominant in LV, and Casuarina equisetifolia and Hibiscus tiliaceus were dominant in RV. Mean species richness, stem density and basal area plot−1 varied significantly between RV and LV (P<0.0001). LV showed higher values for variables than RV. The values for all the variables increased during the second year, except for stem density in LV and show significant differences between the years for RV and LV (P<0.01). Species richness plot−1 in LV may reach the mature forest value in two years if the species accumulation proceeds at the observed rate. We inferred that the natural recovery of vegetation was higher in the soil substratum unaffected LV than the debris deposited RV. Hence, the restoration of soil at RV sites is important for promoting the natural colonization of pioneer and old-growth forest species. Continuous monitoring of these plots may provide useful information on the long lasting impacts and recovery of littoral forest after tsunami.

Implications of accounting for land use in simulations of ecosystem carbon cycling in Africa

Abstract. Dynamic global vegetation models (DGVMs) are important tools for modelling impacts of global change on ecosystem services. However, most models do not take full account of human land management and land use and land cover changes (LULCCs). We integrated croplands and pasture and their management and natural vegetation recovery and succession following cropland abandonment into the LPJ-GUESS DGVM. The revised model was applied to Africa as a case study to investigate the implications of accounting for land use on net ecosystem carbon balance (NECB) and the skill of the model in describing agricultural production and reproducing trends and patterns in vegetation structure and function. The seasonality of modelled monthly fraction of absorbed photosynthetically active radiation (FPAR) was shown to agree well with satellite-inferred normalised difference vegetation index (NDVI). In regions with a large proportion of cropland, the managed land addition improved the FPAR vs. NDVI fit significantly. Modelled 1991–1995 average yields for the seven most important African crops, representing potential optimal yields limited only by climate forcings, were generally higher than reported FAO yields by a factor of 2–6, similar to previous yield gap estimates. Modelled inter-annual yield variations during 1971–2005 generally agreed well with FAO statistics, especially in regions with pronounced climate seasonality. Modelled land–atmosphere carbon fluxes for Africa associated with land use change (0.07 PgC yr−1 release to the atmosphere for the 1980s) agreed well with previous estimates. Cropland management options (residue removal, grass as cover crop) were shown to be important to the land–atmosphere carbon flux for the 20th century.

Natural recovery of dwarf shrubs following topsoil and vegetation clearing on gravel and sand plains in the southern Namib Desert

Natural recovery of vegetation in arid areas is expected to take long time spans. Relatively rapid turn-over times have, however, been reported in Succulent Karoo vegetation in southern Africa, suggesting a certain resilience. This study investigated natural recovery of coastal Succulent Karoo shrubland five, six and seven years after geological sampling in the southern Namib Desert. The geological sampling resulted in a grid-pattern of cleared and topsoil stripped 5 × 5 m areas in three study sites in slightly different environmental settings. Using plant species richness, vegetation cover, plant species composition and an adaptation of dominance–diversity curves as measures, the initiation of natural recovery was demonstrated at all three study sites. Calcrete and gravel plain vegetation showed the best recovery, followed by sand plain vegetation and gravel plain vegetation in a deflation valley (wind corridor). An adaptation of dominance–diversity curves proved useful in illustrating successional patterns in these sparsely vegetated, arid dwarf shrublands and provided a tool to extract information for species-level management intervention. An exceptional rainy season, a large edge effect due to the localised impact of the geological sampling, intact subsurface structure and natural sand deposition are hypothesised to have favoured the initiation of natural recovery in this arid area.

Colonization and expansion of grassland species after abandonment of dirt roads in the Mongolian steppe

Off-road vehicles cause long-lasting damage to soils and vegetation, especially under extreme conditions such as those in arid regions. Most research on natural vegetation recovery after dirt-road abandonment has only investigated vegetation in the tracks and not that adjacent to the tracks. We investigated plant expansion into adjacent grassland after its colonization of abandoned tracks in the Mongolian steppe. We surveyed the vegetation around two roads: one abandoned for >4 years and another still in use near the abandoned road. Aboveground biomass and ground cover of each species in and beside the tracks were measured. The dirt roads had sustained relatively low vehicle traffic, so the disturbance of grassland productivity was limited. Vegetation cover and aboveground biomass had almost recovered 4 years after road abandonment. However, a low-palatability clonal herb, Artemisia adamsii, increased in abundance by producing many shoots in and around the abandoned tracks, thereby decreasing the quality of pasture. Our results show that vegetation recovery in tracks of the abandoned road can affect surrounding vegetation through the colonization and expansion of clonal species. Thus, to evaluate natural vegetation recovery after dirt-road abandonment, changes in vegetation not only within but also around abandoned tracks should be investigated.

Microtopography and the Properties of Residual Peat Are Convenient Indicators for Restoration Planning of Abandoned Extracted Peatlands

AbstractThe natural recovery of vegetation on abandoned peat extraction areas lasts for decades and the result of restoration succession can be unpredictable. The aim of the study was to specify environmental factors that affect the formation of the pioneer stages of mire communities and, therefore, be helpful in the prediction of the resulting ecosystem properties. We used the national inventory data from 64 milled peatlands in Estonia, distributed over the region of 300 × 200 km. This is the first national‐scale statistical evaluation of abandoned extracted peatlands. During surveys, vascular plants, bryophytes, and residual peat properties were recorded on three microtopographic forms: flats, ditch margins, and ditches. The microtopography was the main factor distinguishing the composition of plant communities on flats and ditches, while ditch margins resembled flats. The extracted indicator species suggested two successional pathways, toward fen or raised bog community. A single indicator trait—the depth of residual peat, which combines the information about peat properties (e.g. pH, ash content, and trophicity status), predicted the plant community succession in microtopographic habitats. We suggest that peatland management plans about the cost‐efficient restoration of abandoned peat mining areas should consider properties of residual peat layer as the baseline indicator: milled peatfields with thin (&lt;2.3 m) and well‐decomposed residual peat should be restored toward fen vegetation types, whereas sites with thick (&gt;2.3 m) and less decomposed residual peat layer should be restored toward transitional mires or raised bogs. Specific methodological suggestions are provided.

Soil water repellency in riparian systems invaded by Eucalyptus camaldulensis: A restoration perspective from the Western Cape Province, South Africa

South African riparian systems are threatened by major alien plant invasions through the widespread replacement of native plant species by fast-growing alien species, including several Eucalyptus species. Since Eucalyptus species are known to cause soil water repellency, this study examined the occurrence of soil water repellency coupled with soil moisture and infiltration under laboratory conditions from soils collected along the Berg River which is heavily invaded by alien tree species, especially E. camaldulensis. The connection between alien clearing for restoration purposes and soil water repellency is important as it has the potential to affect the success of native vegetation recovery. The topsoil was sampled at 12 sites, under different restoration treatments, namely invaded by Eucalyptus, completely cleared, thinned and native (control) sites. The water drop penetration time (WDPT) and the critical surface tension (CST) methods were performed. Soil moisture was found to be higher in invaded and natural sites compared to completely cleared and thinned sites. Soil water repellency, measured with the WDPT test on dried samples taken at 5–10cm depth, differed with invasion status and/or restoration condition. In invaded sites water repellency varied from wettable to severely water repellent: in thinned sites from non-repellent to strongly water repellent; in natural sites from wettable to slightly water repellent; all samples from completely cleared sites were wettable. Soil water repellency had no impact on soil infiltration rates. We conclude that the removal of invasive Eucalyptus species has the potential to restore soils to a non-repellent state, thus improving soil related ecosystem functions, which will facilitate the restoration of indigenous species, vegetation composition and structure.

Study on the Vegetation Recovering Effect of Oily Soil after Bioremediation

The vegetation recovering effect of oily soil after bioremediation was studied and contrasted with the background of natural environment in this paper. The results indicated that the vegetation productivity of oily soil after microbial remediation can be restored to its original level, but is not enough to rely on natural recovery of vegetation. The unit productivity of oily soil only through microbial remediation was obviously lower than natural background, and the biocommunity and its vertical structure were relatively simple. But the unit productivity of oily soil after phytoremediation was nearly similar to the uncontaminated soil.

Hierarchical distance‐sampling models to estimate population size and habitat‐specific abundance of an island endemic

Population size and habitat-specific abundance estimates are essential for conservation management. A major impediment to obtaining such estimates is that few statistical models are able to simultaneously account for both spatial variation in abundance and heterogeneity in detection probability, and still be amenable to large-scale applications. The hierarchical distance-sampling model of J. A. Royle, D. K. Dawson, and S. Bates provides a practical solution. Here, we extend this model to estimate habitat-specific abundance and rangewide population size of a bird species of management concern, the Island Scrub-Jay (Aphelocoma insularis), which occurs solely on Santa Cruz Island, California, USA. We surveyed 307 randomly selected, 300 m diameter, point locations throughout the 250-km2 island during October 2008 and April 2009. Population size was estimated to be 2267 (95% CI 1613-3007) and 1705 (1212-2369) during the fall and spring respectively, considerably lower than a previously published but statistically problematic estimate of 12 500. This large discrepancy emphasizes the importance of proper survey design and analysis for obtaining reliable information for management decisions. Jays were most abundant in low-elevation chaparral habitat; the detection function depended primarily on the percent cover of chaparral and forest within count circles. Vegetation change on the island has been dramatic in recent decades, due to release from herbivory following the eradication of feral sheep (Ovis aries) from the majority of the island in the mid-1980s. We applied best-fit fall and spring models of habitat-specific jay abundance to a vegetation map from 1985, and estimated the population size of A. insularis was 1400-1500 at that time. The 20-30% increase in the jay population suggests that the species has benefited from the recovery of native vegetation since sheep removal. Nevertheless, this jay's tiny range and small population size make it vulnerable to natural disasters and to habitat alteration related to climate change. Our results demonstrate that hierarchical distance-sampling models hold promise for estimating population size and spatial density variation at large scales. Our statistical methods have been incorporated into the R package unmarked to facilitate their use by animal ecologists, and we provide annotated code in the Supplement.

Both complete clearing and thinning of invasive trees lead to short‐term recovery of native riparian vegetation in theWesternCape,SouthAfrica

AbstractQuestionsMost rivers in theWesternCapeProvince ofSouthAfrica are heavily invaded by alien trees, often resulting in profound changes in biodiversity and ecosystem functioning. Although large‐scale management operations are underway to clear invasive trees and restore ecosystem function, little is known regarding native species recovery after alien clearing. HasEucalyptusinvasion along theBergRiver altered the distribution and composition of native vegetation? How does the removal of invasive trees through complete clearing and thinning facilitate the recovery of native vegetation?LocationBergRiver,WesternCape,SouthAfrica.MethodsWe assessed the recovery of native vegetation after 4 yr of complete clearing of the invasive treeEucalyptus camaldulensis(100% alien cover removal) and thinning (40–50% alien cover removal) along theBergRiver in theWesternCape,SouthAfrica. Native and alien plant cover, species richness and diversity were recorded on completely cleared and thinned sites and compared to natural (non‐invaded control sites) andE. camaldulensisinvaded sites.ResultsSpecies richness and diversity were significantly higher in both completely cleared and thinned sites compared to natural and invaded sites. Increases in species richness and diversity in completely cleared and thinned sites were a result of re‐invasion by alien herbaceous and graminoid species, which have the potential to hinder native species recovery. Cover of native trees and shrubs was higher in both completely cleared and thinned sites compared to invaded sites. Species composition (relative cover) in completely cleared and thinned sites was similar to species composition in natural sites.ConclusionsBoth complete clearing and thinning methods promote indigenous vegetation recovery and a positive trajectory towards recovery of ecosystem structure and composition can be expected in future. To improve management operations, a four‐stage thinning process that has the potential to facilitate native species recovery is suggested.

Monitoring vegetation recovery after China's May 2008 Wenchuan earthquake using Landsat TM time‐series data: a case study in Mao County

AbstractThe Wenchuan earthquake (Richter scale 8) on 12 May 2008 in southwestern China caused widespread ecosystem damage in the Longmenshan area. It is important to evaluate natural vegetation recovery processes and provide basic information on ecological aspects of the recovering environment after the earthquake. To circumvent the weather limits of remote sensing in the Wenchuan earthquake‐hit areas, and to meet the need for regional observation analyses, three Landsat TM images pre‐ and post‐earthquake in Mao County were used for analysis. Post‐earthquake normalized difference vegetation index (NDVI) values were compared to pre‐earthquake values with an NDVI‐based index differencing method to determine the extent to which the vegetation was damaged in relation to the pre‐earthquake pattern, and the rate of recovery was evaluated. The spatial characteristics of vegetation loss and natural recovery patterns were analyzed in relation to elevation, slope and aspect. The results indicated that severely damaged sites occurred mainly in river valleys, within a range of 1,500–2,500 m elevation and on slopes of 25–55°. The distance from rivers, rather than the distance from active faults, controls the damage patterns. After 1 year of natural regeneration, 36 % of the destroyed areas showed a decrease in NDVI value, 28.8 % showed very little change, 19.1 % showed an increase, and 16.1 % also increased with a recovery rate greater than 100 %. Moreover, there is a good correlation between recovery rate and both slope and elevation, but recovery patterns in the damaged area are complicated. Our results indicate that natural recovery in this arid valley is a slow process.

GIS APPLIED TO THE STUDY OF TEMPORAL RECOVERY OF BURNED AREAS IN THE MUNICIPALITY OF PAI PEDRO LOCATED IN REGION NORTH OF THE STATE OF MINAS GERAIS

The northern region of Minas Gerais is considered a transition area between the biomes Caatinga and Savanna, with predominance of the Savanna and its variations. It is common to the occurrence of fires, which can be caused naturally or by anthropogenic actions, resulting in changes in the landscape. In this sense, the study aims to evaluate from time series of LANDSAT-5/TM and MODIS/TERRA images the process of natural recovery of vegetation after the identification of operational pixels corresponding to the burned areas. The results of the research are based on the response of the municipality test of Pai Pedro/MG. We can observe that was detected a hotspots pixel on the day 08/04/2008 through images MOD14A1, which validation was performed from the survey of burned areas conducted by INPE - National Institute of Space Research. From the identification of operational pixel of burned was evaluated the dynamics of recovery of the area through the vegetation index NDVI (Normalized Difference Vegetation Index), generated by images MODIS/TERRA, product MOD13Q. The scars of burned analyzed, approximately 52% were detected. Despite this limitation, much of the area impacted was identified. The errors of omission were considered satisfactory, with a view to the technical limitations of spatial resolution of the sensors used.

Impacto econômico da reserva legal sobre diferentes tipos de unidades de produção agropecuária

Este trabalho avalia o impacto econômico da reserva legal sobre a margem bruta de diferentes tipos de unidade de produção agropecuária (UPA) da Microbacia do Rio Oriçanga - São Paulo. A partir de uma tipologia das UPAs elaborada para a região, escolheram-se dois tipos para detalhamento do estudo: os pequenos produtores de baixa tecnologia e os citricultores. A modelagem de suas estruturas produtivas foi realizada por meio do método de programação recursiva, abarcando o período de 2002/03 a 2008/09. Os sistemas atuais dos dois tipos de UPAs foram confrontados com dois cenários de compensação do déficit de reserva legal, através da realocação de áreas produtivas no interior da própria unidade: I) procedendo-se à recuperação da vegetação natural nestas áreas por meio do plantio de espécies nativas, com vistas ao manejo sustentável para exploração de madeira; II) deixando que aí se desse o crescimento da vegetação espontânea, sem nenhum tipo de manejo ou exploração. Os resultados evidenciam a importância de políticas que permitam uma distribuição mais equitativa dos custos da conservação ambiental entre toda a sociedade, bem como a importância de ajustes locacionais das reservas legais, na busca de um melhor equilíbrio entre a conservação da biodiversidade e o custo de oportunidade das terras.

Assessing the potential effect of different land cover management practices on sediment yield from an abandoned farmland catchment in the Spanish Pyrenees

PurposeSediment delivery from headwater catchments to reservoirs is a serious threat to reservoir sustainability and is a critical issue in Mediterranean environments where water resources are scarce. In this study we assessed the consequences of two landscape management scenarios (natural vegetation recovery and scrub clearance) on soil erosion and sediment yield. The results were analyzed in relation to predicted and measured rates of soil erosion and sediment yield, with the aim of promoting better management practices.Materials and methodsThe study area was the Arnás River catchment (284 ha), which is located in the central Spanish Pyrenees; the area includes abandoned and poorly managed fields. The combination of the RUSLE and SEDD models of soil erosion and sediment delivery was evaluated in terms of its ability to predict annual rates of sediment yield, using field measurement data for seven water years at the gauging station. The consequences of natural plant succession in other areas of the Spanish Pyrenees and scrub clearance practices implemented by certain regional governments to increase grazing meadow areas and reduce the incidence of wildfires were spatially analyzed using GIS. The main sediment source areas were identified, and their specific and total sediment yields were calculated.Results and discussionThe predicted soil loss under existing conditions was 2.6 Mg ha−1 year−1, with 5% of the surface area affected by rates greater than 2 Mg. The measured sediment yield range was 69–534 Mg year−1. The maximum sediment yield detected was associated with an extraordinary debris flow. The predicted rates were strongly correlated to measured rates (Nash–Sutcliffe coefficient = 0.72). The main sources were alluvial deposits [specific sediment yield (SSY) = 51 Mg ha−1 year−1], bare soil (SSY = 12), unpaved trails (SSY = 11), lots (SSY = 4), and pastures (SSY = 1). Under a scenario of vegetation recovery, decreases of 3%, 17%, and 16% in soil loss and sediment delivery and yield (respectively) are predicted, whereas increases of 15%, 5%, and 2% are predicted following scrub clearance practices.ConclusionsCoupling the RUSLE and SEDD models enabled estimation of annual values of soil erosion and sediment delivery in monitored and unmonitored catchments of small and medium size, making this approach a useful tool for risk analysis. Management practices that combine fire-risk control, by the implementation of scrub clearance practices, with the effects of plant succession on sediment production are suggested as the best management strategy.