Vegetation Recovery Processes Research Articles

Monitoring Earthquake-Damaged Vegetation after the 2008 Wenchuan Earthquake in the Mountainous River Basins, Dujiangyan County

The 2008 Wenchuan earthquake destroyed large areas of vegetation in the Baisha River and Longxi River basins, in Dujiangyan County, China. There were several debris flow events in these mountainous river basins after 2008. Currently, these damaged vegetation areas are in various stages of recovery. This recovery vegetation improves the resistance of slopes to both surficial erosion and mass wasting. We introduce a probabilistic approach to determining the relationships between damaged vegetation and slope materials’ stability, and model the sediment and flow (hydrological) connectivity index to detect the hydrological changes in a given river basin, using the multi-temporal (1994–2014) remote-sensing images to monitor the vegetation recovery processes. Our results demonstrated that the earthquake-damaged vegetation areas have coupling relationships with topographic environment and slope material properties, and can be used to assess the slope material stability. Further, our analysis results showed that the areas with horizontal distance to river streams <500 m are areas that actively contribute sediment to the stream channel network, and are main material sources for debris flow processes in one given mountainous basin.

Dynamic changes in soil and vegetation during varying ecological-recovery conditions of abandoned mines in Beijing

Vegetation restoration in abandoned mines is very difficult and time consuming because of the harshness of the ecosystem, i.e., the extremely high and steep slopes. To accelerate the process of vegetation recovery in abandoned mines, understanding the rules of vegetation succession and the variation in soil characteristics during this process is very important. In the Zhoukoudian vegetation restoration experiment demonstration area (a 12ha area located in Fangshan District, Beijing, China), engineering measures, such as biological greening bags, eco-stick slope protection, container seedling planting and vegetative-carpet greening technologies, were applied to accelerate the process of vegetation recovery. In this study, 149 human-restored and spontaneously recovering slopes under three substrates were sampled to investigate the dynamic changes in soil and vegetation in different stages of succession by means of space-for-time substitution. WinTWINS was used to classify the samples, which experienced different recovery periods, into 6 plant community types. According to the results, the species richness index, Simpson’s predominance index, the Shannon–Wiener index and the soil fertility of the communities dominated by young trees (V, VI) were higher than those of the communities dominated by grasses (I, II) or shrubs (III, IV); thus, plant communities V and VI are considered optimal representations of severely damaged surface-mine ecosystems. Our results suggest that native species should be planted to accelerate the succession process by implementing the best engineering measures for different substrate types during the initial restoration.

Long-term vegetation development on a wildfire slope in Innerzwain (Styria, Austria)

Forest fires in mountainous areas can cause severe deforestation which can potentially trigger secondary natural hazards like debris falls and avalanches. We documented an extreme case study for the range of possible post-fire land cover (LC) dynamics. We investigated a 15-ha, steep (10°–65°) burnt slope in Styria (Austria) at elevation of 760°-113 m, which burned in 1946 and has not fully recovered to date. Seven 8-class legend LC maps were produced (1954, 1966, 1973, 1982, 1998, 2004, 2009) and integrated in a vector-based GIS, mainly by on-screen interpretation of aerial photos. Our aim was to clarify how post-wildfire LC dynamics take place on a severely damaged, steep slope and to give a basic projection of the future vegetation recovery process. The pre-fire Pinus sylvestris stands have been mainly replaced by Picea abies and Larix decidua. Regeneration proceeded mainly from the base of the slope upwards. All tree species together still cover no more than 40% of the slope after more than 60 years of recovery, while grassland communities and rock/debris areas have expanded. Multitemporal analysis showed a slow but steady increase in woodland cover. Degraded rock/debris areas, however, expanded as well because soil erosion and related debris flows remained active. Slope angle (with a threshold value of approx. 35-40°) seemed to control whether erosion or regeneration prevailed. According to a simple extrapolation, the slope will not reach its former condition before 2070. This extreme disturbance window of more than 120 years is owed to the steepness of the slope and to the shallow soils on dolomitic bedrock that were severely damaged by the fire. The neglect of any game fencing is a further factor slowing regeneration.

An efficient method for change detection of soil, vegetation and water in the Northern Gulf of Mexico wetland ecosystem

Mapping and monitoring wetland ecosystems over large geographic areas based on remote sensing is challenging because of the spatial and spectral complexities of the inherent ecosystem dynamics. The main objective of this research was to develop and evaluate a new method for detecting and quantifying wetland changes in the Northern Gulf of Mexico (NGOM) region using multitemporal, multispectral, and multisensor remotely sensed data. The abundance of three land- cover types (water, vegetation, and soil) was quantified for each Landsat 30 m pixel for 1987, 2004, 2005, and 2006 using a regression tree algorithm. The performance of the algorithm was evaluated using an independent reference data set derived from a high-resolution QuickBird image, and several statistics including average error (AE), relative error (RE), and the Pearson correlation coefficient (r). For per-pixel percentage estimation, the AE is under 10% for water prediction, 9.5–11.4% for vegetation, and 9–11.1% for soil. The correlation coefficients between predicted and reference data range from 0.90 to 0.96 for water, from 0.80 to 0.89 for vegetation, and from 0.79 to 0.86 for soil. The high accuracy achieved by this method is attributed to the high quality of training data and the rigorous calibrations applied to multisensor and multitemporal satellite imagery. Based on the multitemporal estimation of the three land-cover components, spatial and temporal changes of the land-cover types from 1987 to 2006 were quantified and analysed. The study demonstrates that the method provided useful information on the abundance and changes of the key land-cover types in the NGOM region where long-term disturbances and episodic events occurred. Such information is valuable for monitoring land and vegetation loss and recovery processes, and for understanding possible drivers of the coastal wetland evolution in the region.

Effects of enclosures on vegetation recovery and succession in Hulunbeier steppe, China

Hulunbeier steppe is one of the four largest grasslands in China and is renowned for its excellent natural grassland conditions. However, its natural ecosystem has been continuously disrupted due to heavy land use, excessive stock-farming, and deforestation as human activities have expanded. Exclusion of human disturbance is one of the common measures used for ecological environment restoration in Chinese desert areas. This study aims to investigate whether the duration of enclosure affects vegetation recovery and succession processes. Plant distribution, coverage and biomass were measured and described in non-enclosure, 1-year, 5-year, and 10-year enclosure plots. Vegetation succession proceeded via three stages. In the first stage, annual plant communities, such as Agriophyllum squarrosum and Corispermum stauntonii, were dominant, while in the second stage renascent arboreal herbs, mainly Cleistogenes squarrosa and Artemisia frigid, predominantly occupied the vegetation community. In the third stage, transition vegetation such as Agropyron cristatum and C. squarrosa werepredominant. Relevant government authorities in the Hulunbeier region should educate the herders regarding the apposite management of enclosure and provide incentives for compliance. Future study design should focus on effective enclosure management including grazing rate control and plantation development in enclosure.

The interplay among grazing history, plant-plant spatial interactions and species traits affects vegetation recovery processes in Patagonian steppe

Since the early 20th century Patagonian arid steppes have been subjected to overgrazing that led to the degradation of plant communities. We hypothesized that the interplay among grazing history, plant-plant spatial interactions and species traits affects recovery and assemblage of shrub community after short-term abandonment in north-eastern Patagonian arid steppe (Peninsula Valdes, Argentina). We compared six sites (two in grazed pastures, and four in short-term ungrazed pastures, two of which intensively grazed, while the other two low intensity grazed in the past) with regard to: shrub cover percentage (10 × 10 m plots); shrub patch dimension, species richness, and spatial interactions among shrub species depending on patch dimension (patches sampled along transects); species richness and composition, vertical relations among species, and traits related to avoidance strategies and disturbance (1 × 1 m plots sampled along transects). Our results indicated that recovery processes in abandoned pastures a...

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.

Patterns of species diversity and soil nutrients along a chronosequence of vegetation recovery in Hainan Island, South China

AbstractUnderstanding the pattern of species diversity and soil factors can enhance our knowledge of the mechanism of vegetation recovery, however, there is still a gap in the knowledge of succession rate and trend for species diversity in relation to soil nutrients during the vegetation recovery process. Patterns of species diversity and soil nutrients during the tropical vegetation recovery as well as the correlation between species diversity and soil nutrients were explored in Hainan Island, located in southern China. Plots assigned as grassland stage (GS), shrub stage (SS), secondary forest stage (SFS), and primary forest stage (PFS) were established using a chronosequence approach. Results showed that species richness and evenness increased from GS to PFS. Species dominance/diversity curves were fitted using the lognormal distribution model (r2= 0.891–0.972). Species richness for the herb layer was maximal at SFS, whereas species richness for both the shrub layer and tree layer reached their maximum at PFS. Species turnover and soil total phosphorus decreased, whereas organic matter and total nitrogen increased from GS to PFS. Organic matter and total nitrogen were both positively correlated with species richness and total coverage, and total phosphorus was positively correlated with species turnover. The results clearly demonstrate that diversity asymptotically increases and positively correlates with increasing soil fertility, and the total phosphorus value is predicted to be an important soil factor that affects successional rate during tropical vegetation recovery processes.

Changes of Species Richness in Heathland Communities over 15 Years following Disturbances

The aim of this study was to define the species richness patterns over a period of 15 years during the vegetation recovery process after disturbances (burning, cutting and ploughing) in heathlands. Three communities were selected: two dominated byErica australisand one dominated byCalluna vulgaris. The alpha and gamma diversity patterns were site specific and influenced by the ecological traits of dominant shrub species. The shrubland dominated byErica australis, typical resprouters with a fast regeneration, showed the highest values of alpha and gamma diversity during the first 7 years of regeneration. The heathland dominated byCalluna vulgaris, an obligate seeder, had a contrasting pattern of alpha and gamma diversity, as the highest values appeared from year 7 until year 14. Thus, the speed of regeneration of the dominant shrub species could be the main factor affecting structural parameters in these communities. Species richness patterns did not vary in relation to the different types of perturbation. Cutting and burning would be the most suitable forestry management strategies to conserveErica australisheathlands, but burning is more appropriate inCalluna vulgarisones because cutting modified this community.

Soil seed banks in a mature Hinoki (Chamaecyparis obtusa Endl.) plantation and initial process of secondary succession after clearcutting in southwestern Japan

To profile secondary succession after clearcutting a conifer plantation, we examined the composition of the soil seed bank and the process of vegetation recovery after clearcutting a mature Hinoki (Chamaecyparis obtusa) plantation in southwest Japan. We set up two study plots and collected 25 and 26 soil samples (each 20 cm × 30 cm × 5 cm depth), respectively, in April 1999, before clearcutting. Using the seedling emergence method, we detected 500–839 buried viable seeds m−2 in 42–44 species. Soil seed banks in both plots contained typical pioneer species but few late-successional species. After clearfelling the plantation in June 1999, we censused seedling establishment for 4 years and the composition of the vegetation for 6 years. More than half of the seedlings emerged in the second year, suggesting that the timing of clearcutting is possibly critical to seedling establishment. Nineteen plant species disappeared after clearcutting, 40 species were retained and 43 species newly emerged after clearcutting. Most of the newly emerged species were pioneer species which originated in the soil seed bank. Seven of the pioneer species, as typified by Rubus crataegifolius, showed clonal growth from the third year after clearcutting. Japanese serow browsed the seedlings of major pioneer species, possibly affecting the process of secondary succession. Late-successional species such as Abies firma declined in coverage or disappeared after clearcutting. Our results suggest that the soil seed bank makes a major contribution to vegetation recovery after clearcutting, but possibly not to restoration of the late-successional species.

衛星リモートセンシングによる三宅島２０００年噴火後の植生回復過程の評価

The vegetation of Miyake Island has been widely effected by the volcanic eruption in July 2000. This phenomenon is still going on and much of the vegetation cover has been changed. It is quite important to monitor the vegetation recovery process because of ecosystem study, prevention of disaster and rehabilitation of the Island. This study investigated an evaluation of the vegetation recovery process in Miyakejima Island after the 2000 volcanic eruption using satellite remote sensing and field vegetation survey. Multi temporal 12 satellite images of Terra/ASTER and JERS-1/OPS were selected and combined into three time series datasets such as the before eruption, the after eruption within two years and the after eruption more than three years. These three time series image datasets were analyzed into the seamless images of the maximum NDVI value. According to the unsupervised classification of these three images, Miyakejima Island was divided into six classes with vegetation change patterns. These results followed past works and field vegetation survey well. The classes were recognized with the vegetation change which shows the damage of trees and the recovery of vegetation after the volcanic eruption of the year 2000.

Recovery in Naturally Dynamic Environments: A Case Study from the Sperrgebiet, Southern African Arid Succulent Karoo

Little is known about the process of vegetation recovery and associated time frames in the Succulent Karoo Biome of southern Africa. This study investigated the recovery of vegetation on sites impacted by mining (different types of dumps and mined areas) in the arid succulent karoo. The main aim of this study was to determine the state of recovery, time frames, successional stages, and the influence of environmental factors on recovery of coastal dune and sand plain plant communities. For this purpose, vegetation was recorded on some 121 sites throughout a coastal strip of approximately 100 x 3 km in Namibia's restricted diamond area (Sperrgebiet). Using the species pool concept to derive vegetation reference sites and dominance-diversity curves, recovery of vegetation (measured in terms of species richness and cover) in these altered landscapes reached about 46% on the oldest, 51-year-old mine dumps. However, based on species richness, richness levels similar to the undisturbed reference sites were recorded after 30 years, following a logarithmic trend. Successional stages of natural recovery were indicated in this dynamic coastal environment and Cladoraphis cyperoides and Galenia fruticosa appear to be early successional species. Scaling up of studies to landscape level and developing a target community using the species pool concept are discussed as means to measure recovery in dynamic biological communities. On these altered, man-made landforms, the availability of seed may be the bottleneck to achieve vegetation cover comparable to undisturbed vegetation in the surrounding. Hence, restoration efforts should focus on this aspect.

Soil properties and physiographic factors controlling the natural vegetation re-growth in a disturbed catchment of the Central Spanish Pyrenees

Large changes in land use have occurred in the Central Spanish Pyrenees during the twentieth century. This mountain area supported an intense human use since the Middle Ages, that greatly transformed the natural landscape. The land uses changed dramatically during the first half of the twentieth century, due to major socioeconomic forces which lead to depopulation and land abandonment. Since then, a process of natural vegetation recovery has taken place. The anthropogenic impact during centuries deteriorated the soil quality, threatening the sustainability of agroecosystems and the natural vegetation re-growth. In this study, a soil survey was performed to identify the soil types and the physico-chemical properties of the soil that are relevant for maintaining the soil function for the recovery of vegetation after land abandonment. The study was conducted in the Arnas River catchment, which is representative of the region. The highest cation exchange capacity (CEC), nutrients, water retention, water availability and infiltration rates, as well as the lowest pH and carbonates, occurred in Lithic Hapludolls and Calcic Haploxerolls at the shady aspect, under a forest cover. Lithic Ustochrepts and Lithic Xerorthents on the sunny aspect, which were covered by shrubs, were of lesser quality than were the deeper and better-developed soils on the shady aspect. This is seen as an evidence of different patterns of soil degradation, which conditioned the re-growth of natural vegetation after land abandonment. The results provide insights into the main soil factors that have affected the re-establishment of natural vegetation in recent years. Recommendations are given for designing effective strategies for soil conservation after land abandonment in similar mountain environments.

Mapping erosion‐sensitive areas after wildfires using fieldwork, remote sensing, and geographic information systems techniques on a regional scale

Alterations in the hydrological cycle following wildfire due to the loss of ground cover vegetation and changes in soil properties have been documented in many studies. Nevertheless, the rapid process of vegetation recovery reduces such negative effects. Vegetation cover before fire, fire severity, and geophysical properties are important factors that control spatial discontinuities involved in the vegetation‐covering process. The objective of this study was to estimate the probability of high erosion in order to map erosion‐sensitive areas after fire. The analysis was carried out in different plant communities burnt by summer wildfires in the pre‐Pyrenean area (Spain). Three‐year Landsat Thematic Mapper (TM) images have been used for mapping wildfire areas and severity levels. Conversion to spectral reflectance has been applied for radiometric correction by normalizing topographic and atmospheric effects. Likewise, other physical variables have also been incorporated into the geographic information system (GIS): vegetation types, parent material, illumination, slope, aspect, and precipitation. The dependent variable has been characterized by means of fieldwork and a photointerpretation process based on high‐resolution digital aerial orthophotographs taken 11–12 years after the fire. Different logistic regression models have been used for mapping the probability of erosion. Results indicate that prefire normalized difference vegetation index values and aspect are the most important variables for estimating erosion‐sensitive areas after fire (Nagelkerke r2 = 0.66; Kappa values = 0.65). Finally, the use of nonparametric models with environmental digital information based on GIS can facilitate the management of burnt areas.

７６年間における崩壊地の長期変動と植生回復過程―西丹沢山地玄倉川仲の沢流域を対象として―

神奈川県北西部にあたる丹沢山地は神奈川県の重要な水源林である。しかし, 1923年に起きた関東大震災やその後の降雨などによって崩壊や土石流が多発した場所であり, 現在も多くの崩壊地が残存しているため, 森林地帯が本来持つ十分な水土保全機能が発揮されていないと考えられる。本研究では西丹沢山地玄倉川仲の沢流域約370haを対象とし, 崩壊地の植生回復過程を明らかにすることを目的とし, 航空写真による崩壊地の変遷調査と残存する崩壊地の植生回復状況を調べる現地調査を行った。崩壊が発生した後, 短期間で植生が回復する崩壊地と残存する崩壊地の違いは崩壊面積の大きさ, 傾斜角や斜面方位, 標高が要因として大きく関与していた。

Change of soil physical properties under long-term natural vegetation restoration in the Loess Plateau of China

A 150-year chronological study of semi-arid abandoned farmland in the central Loess Plateau of China indicated that soil physical properties were closely related to the date of being abandoned and the vegetation recovery stages. Bulk density of the surface layer (0–20 cm) significantly reduced with time while soil porosity, water-holding capacity, aggregate stability, and saturated hydraulic conductivity significantly increased. In the early period of abandonment, up to 14 years, these changes were relatively fast due to a significant increase of soil organic matter content. However, amelioration of soil physical properties of subsurface layers (20–40 cm) was relatively slow. Decline of soil bulk density of surface layers could be used as an indicator of soil structure amelioration since it was related to most other properties. Changes of soil textural properties and specific surface area were not significant, which suggested that these properties were mainly inherited from parent materials and difficult to change. Emergence of dominant woody plants during the natural vegetation recovery process could be a useful and reliable indicator of obvious improvement in soil physical properties.

Community succession along a chronosequence of vegetation restoration on sand dunes in Horqin Sandy Land

Species diversity influences plant community structure and function. This paper examines the patterns and dynamics of species diversity along a chronosequence of vegetation recovery on sand dunes in a semi-arid region to assess the probability of vegetation recovery via succession, and provides some implications for revegetation practices in this region. Species richness and diversity indices gradually increased with succession, except for a decline in the community of 18 years, which is attributed to the strong dominance of Artemisia halodendron. In each stage of the restoration process, there was a dominant species with particular life history traits which contribute to the dominance of this species. Species replacement and habitat changes were the main drivers of succession, while plant species and community succession drove the process of vegetation recovery. Results showed that restoration via succession holds promise for vegetation recovery and desertification control within protected, fenced enclosures.

Slow recovery in desert perennial vegetation following prolonged human disturbance

AbstractQuestions: How long may it take for desert perennial vegetation to recover from prolonged human disturbance and how do different plant community variables (i.e. diversity, density and cover) change during the recovery process?Location: Sonoran Desert, Arizona, USA.Methods: Since protection from grazing from 1907 onwards, plant diversity, density and cover of perennial species were monitored intermittently on ten 10 m × 10 m permanent plots on Tumamoc Hill, Tucson, Arizona, USA.Results: The study shows an exceptionally slow recovery of perennial vegetation from prolonged heavy grazing and other human impacts. Since protection, overall species richness and habitat heterogeneity at the study site continued to increase until the 1960s when diversity, density and cover had been stabilized. During the same period, overall plant density and cover also increased. Species turnover increased gradually with time but no significant relation between any of the three community variables and precipitation or Palmer Drought Severity Index (PDSI) was detected.Conclusions: It took more than 50 yr for the perennial vegetation to recover from prolonged human disturbance. The increases in plant species richness, density, and cover of the perennial vegetation were mostly due to the increase of herbaceous species, especially palatable species. The lack of a clear relationship between environment (e.g. precipitation) and community variables suggests that site history and plant life history must be taken into account in examining the nature of vegetation recovery processes after disturbance.

FOREST RESPONSE TO CATASTROPHIC WIND: RESULTS FROM AN EXPERIMENTAL HURRICANE

Infrequent, intense wind disturbance is an important factor in northeastern U.S. forests, yet little is known about the early stages of vegetation reorganization, or the processes that facilitate biotic regulation of ecosystem function after such storms. We designed an experiment, based on a simulated hurricane blowdown, to examine the relationship of tree damage patterns to mortality and regeneration, community dynamics, vegetation recovery, and ecosystem processes. In October 1990, selected canopy trees in a 50 × 160 m area within a 75-yr-old Quercus rubra–Acer rubrum forest in central Massachusetts were pulled over by a winch, using records from the 1938 hurricane to determine the number of trees and direction of fall. The resulting damage to 65% of trees closely approximated effects of the 1938 storm on New England forests. Damage and mortality varied by tree species and size, indicating the importance of pre-disturbance forest structure and composition in determining the range and severity of impact. Measurements of vegetation and environment in the experimental area and control indicated that, although the manipulated stand sustained dramatic damage and structural reorganization, resilience of trees and understory vegetation provided tight biotic control of ecosystem processes, including nutrient cycling. Continued leaf-out and induced sprouting by damaged trees, increased growth by saplings and understory plants, and seedling establishment on disturbed microsites stabilized the microenvironment. Our findings are in contrast to studies of disturbances in which mortality was higher when damaged trees were removed from the site. This suggests that salvage logging following wind disturbance may have serious long-term implications.

Seed rain and its role in the recolonization of degraded hill slopes in semi‐arid central Tanzania

SummaryA seed rain study in semi‐arid central Tanzania was conducted with the objective of providing guidelines on how to rehabilitate the degraded vegetation on the hillslopes of the Kondoa Irangi. The seed rain included predominantly wind‐dispersed diaspores which accounted for 78% of the species (45 out of 57) and 97% of the diaspores. The density ranged from 230 to 1667 seeds m‐2 over an 8‐month period. Both species richness and seed density were negatively correlated with vegetation cover. The increasing seed densities with decreasing vegetation cover signifies the importance of anemochory in areas undergoing regeneration succession. Cluster analysis of the seed rain data based on squared Euclidean distances produced a dendrogram with three distinct clusters, representing anemochorous seeds, epi‐zoochorous seeds and a mixture of both, but dominated by seeds with no obvious dispersal appendages. Management including controlled re‐introduction of livestock to the hills to increase nitrogen mineralization, species diversity and to reduce grass biomass, and hence the severity of fires, may be an appropriate solution to speed up the vegetation recovery process.