Landscape and Ecological Engineering

Effects of repeated fertilization and liming on soil microbial biomass in Betula maximowicziana Regel and Abies sachalinensis Fr. Schmidt stands in Japan Abstract Few long-term fertilization experiments have been performed in forests, even though the effects of nitrogen (N) addition on soil microbial biomass are a cause for concern. Our objective was to examine the effects of repeated fertilization for 36 years on soil microbial biomass in two forest stands. We measured soil chemical properties and microbial biomass carbon (C) and N in soils in fertilized and non-fertilized plots in a birch stand (Betula maximowicziana Regel) and a fir stand (Abies sachalinensis Fr. Schmidt). We also performed lime amendments and a 21-day laboratory incubation, and measured microbial biomass to clarify the effects of acidification due to fertilization. Soil pH was significantly lower in fertilized plots in both stands, and soil microbial biomass C and N were lower (significantly so in the fir stand) in the fertilized plots after 36 years of repeated fertilization. In the laboratory incubation, lime amendment did not significantly affect the microbial biomass C, N, or C:N ratio, despite an increase of about 1 unit in soil pH. Our results therefore indicate that factors other than soil pH also have important effects on soil microbial biomass in repeatedly fertilized forest stands.

Annual respiration of Japanese mud snail Batillaria attramentaria in an intertidal flat: its impact on ecosystem carbon flows Abstract The Japanese mud snail Batillaria attramentaria, a common gastropod in northeastern Asia, often predominates in isolated or degraded intertidal flat ecosystems in Japan and in other countries where it has invaded as an alien species. To evaluate the effects of B. attramentaria on carbon flow in intertidal flat ecosystems, we estimated the annual respiration of B. attramentaria from field surveys and laboratory experiments. The densities of the snails, as determined at an intertidal flat of the Seto Inland Sea, western Japan, were 235–485 individuals m−2. Temperature and snail size strongly affected their respiration rates, as determined by measuring their CO2emission rates using an open-flow infrared gas analyzer method. The respiration rates were higher in the submerged condition than in the air-exposed condition. Based on the size structure of the natural population, laboratory experiment results, and environmental factors in the field (temperature and duration of the ebb/flood tide), we estimated the respiration in spring, summer, and autumn, respectively, as 1.9, 2.4, and 4.0 g C m−2. The total amount of carbon mineralized annually by the respiration of B. attramentaria exceeds 10% of that mineralized through sediment respiration. Based on these data and respiration/ingestion ratios in previous reports, we conclude that B. attramentaria has a significant impact on the carbon flows in intertidal flat ecosystems.

Regional landscape-scale comparison of species composition and recruitment in remnant tree patches 3 years after the 2011 Great East Japan Earthquake and tsunami Abstract Understanding species composition and other characteristics of remnant trees that survive large-scale low-frequency disturbances such as tsunamis is an important step in monitoring and managing the process of recovery. This research was implemented in a study area along the shores of Sendai Bay, a region that was heavily damaged by the tsunami following the Great East Japan Earthquake of 2011. Field surveys of all the remnant patches of trees in the study area were conducted in 2014, three years after the disturbance. A total of 202 remnant patches were identified, and all the tree species, including both canopy trees and newly established seedlings, were recorded for each patch. The identified trees totaled 88 species, which were classified into three indicator-species types by a hierarchical cluster analysis. Comparisons based on species composition and similarity showed that species composition and other characteristics of the remnant patches were influenced by vegetation histories and other factors that only become visible at the regional landscape scale. The number of tree and seedling species per unit area was highest in patches that originated from pine plantations. Seven of the 25 seedling species identified were not present in any of the canopy layers in the study area, indicating that they dispersed from outside this area. These results show that, despite the immense scale of the tsunami, many diverse patches of trees managed to survive the disturbance. These patches function as hubs for species dispersion and accelerate recovery of species diversity in the disturbed area.

Soil infiltration rate of forestland and grassland over different vegetation restoration periods at Loess Plateau in northern hilly areas of China Abstract Vegetation restoration practices play an important role in environmental management and could mitigate soil and water losses in the Chinese Loess Plateau. The main objective of this study was to ascertain the influence of vegetation durations on soil infiltration rate and other related soil properties. Undisturbed soil columns in triplicate from the same plot, with different locations, were collected to estimate the accumulated soil infiltration over different vegetation periods (9, 15, and 25 years) of grassland and forestland at different time intervals. The highest cumulative infiltration and wet front movement speed was recorded after 25 years of grassland and increased with the vegetation restoration duration. Low root biomass density (g cm−3) and soil organic matter (g kg−1) were recorded in the 9-year plantation of forestland and grassland; however, maximum root biomass densities of 1.614 ± 0.95 mg cm−3 and 0.938 ± 0.03 mg cm−3 were recorded after 25 years of forestland and grassland. Furthermore, root images scanner analysis showed that the 25 years of grassland has higher root length density and root surface area density of 5.917 ± 0.86 cm cm−3 and 2.058 ± 0.95 cm2 cm−3 at surface and subsurface soil layers. We therefore suggest that for revegetation periods of less than 25 years, grassland would be better for soil infiltration and related soil properties particularly in areas of the Chinese Loess Plateau. Graphical abstract

Future land use/cover changes in Romania: regional simulations based on CLUE-S model and CORINE land cover database Abstract Since 1990, a series of fundamental political and socioeconomic transformations in Romania have led to important structural and functional changes in the land use/cover system. This paper aims to assess the past land use/cover dynamics during the period 1990–2006 and to simulate future changes (2007–2050) to identify the main land use/cover change processes and their potential environmental and land management implications. The simulation was carried out using the Conversion of Land Use and its Effects at Small regional extent (CLUE-S) model with the CORINE Land Cover (CLC) database and several biophysical and socioeconomic explanatory variables associated with the current land use/cover pattern. Using the receiver operating characteristic (ROC) method and cross-classification maps, statistical and spatial validation was assessed to evaluate the performance of the predicted data. The predicted map could represent a useful tool for monitoring and quantifying spatial and temporal land use/cover changes at national and particularly regional level, in order to adopt appropriate land use planning and environmental policy in line with sustainable development principles. In addition, the results could be used for further analyses to examine the consequences of land use/cover changes on landscape diversity and biodiversity, the interaction between land use/cover changes and natural hazards, or the implications for ecosystem services.

A pilot study of river design for slope stability and frog ecology Abstract A pilot study was carried out for the slope design of rivers which took into consideration both slope stability and frog ecology. Ecological engineering is defined as the design of sustainable ecosystems for the integration of human society with its natural environment for the benefit of both. In river engineering projects, the retaining banks and the river bottom are usually constructed of concrete. Although strong, there are no river-like crevices in these structures that can provide habitats, thus organisms are more vulnerable to predation by natural enemies. Ecological river engineering follows the laws of nature and takes into consideration river diversity and sustainable development. It also takes into consideration ecological and safety factors to create river ecosystems and habitats that are diverse, with a reduced impact on the natural environment. So far, there have been no related cross-subject studies on both the needs of amphibians and the slope stability of river banks. In this study, we attempt to increase our understanding and offer insights into current practices in ecological river slope engineering. The research purposes of this study were to examine (1) the climbing abilities of frogs on various degrees of slope and materials and (2) the failure mechanism of the selected slopes using the finite element method (FEM); and carry out (3) safety analysis using the FEM for the selected slopes, and (4) correlation analysis between the climbing abilities of frogs and the safety factors of slopes. The results show that the climbing abilities of frogs on cobblestone are much better than on other materials. Therefore, when considering the survival needs of frogs, the use of rocky revetment should be encouraged for use on ecological slopes. Our results should enhance knowledge relevant to ecologists and engineers for the creation of safe river slopes that also meet the ecological needs of amphibians.

How to renew soil bioengineering for slope stabilization: some proposals Abstract Mountain environments play a crucial role in maintaining biodiversity despite becoming more vulnerable to colluvial processes primarily induced by extreme meteorological events. Soil bioengineering stabilizes mountain slopes and limits impacts on ecosystems and is increasingly used worldwide, yet its effectiveness requires better assessment through post-intervention environmental monitoring. However such studies are only rarely performed even though they are essential to improve future intervention. This study reports soil and vegetation monitoring data of an area in the Italian Alps in which soil bioengineering work was carried out to restore an area hit by landslides. The monitoring involved an analysis of the floristic-vegetational and ecological features of the plant communities of the area of the soil bioengineering intervention (and in adjacent areas), as well as an analysis of the chemical–physical characteristics of the soils (texture, pH, organic matter, nitrogen content, roots depth) where these communities were established. The results of the monitoring, analyzed in the overall framework of the state of the art of the sector, have highlighted some lines of research and action that should be undertaken by technicians, researchers, and politicians to innovate and to make work aimed at the stabilization of landslides more effective. In particular, it would be extremely useful to study the biotechnical characteristics of herbaceous plants that are still “unknown” in soil bioengineering and to evaluate their possible effects on ecosystems in order to produce seed mixtures that, besides being useful for soil stabilization, can accelerate vegetation dynamics, therefore maximizing the success of such works.

Monitoring land cover change of a river-floodplain system using high-resolution satellite images Abstract In this study, a method was developed to monitor habitat structure in river-floodplain systems using high-resolution satellite images from 2010 to 2012 across a 30-km longitudinal section of the Tagliamento River, Northeast Italy. Three ortho-corrected RapidEye satellite images at 5-m spatial resolution and cloud cover of < 1%, with four spectral bands, namely, blue, green, red, and near-infrared, were used for land cover classification by converting pixel values into digital number (DN) distributions. The DN distributions for each band were clustered into separate classes based on correlations among all bands. The rate of unchanged habitat was further calculated as the intersection of all habitats divided by the area of the habitat of interest. The land cover categories were bare alluvium, river water, and vegetation. Bare alluvium was the dominant type, covering 55–75% of land. Vegetation and river water covered a relatively smaller area of the upper part and a larger area of the middle part of the Tagliamento River. The accuracy of this method was greater (> 89%) than that of the conventional unsupervised ISODATA method (> 83%) as river water and vegetation could be differentiated more accurately using this new method. The unchanged area was greater for river water than for vegetation and bare alluvium. These results indicated that habitat distribution changed spatially and temporally, especially for fluvial habitats, while the composition of habitat types was preserved in the middle reaches of the Tagliamento River. This method can be used to continuously and accurately monitor the large-scale spatiotemporal dynamics of habitat structures.

Extinction debt in a biodiversity hotspot: the case of the Chilean Winter Rainfall-Valdivian Forests Abstract Habitat fragmentation has become a major concern of conservation because of negative influences on plant species declines and extinctions. However, local extinction of species can occur with a temporal delay following habitat fragmentation, which is termed extinction debt. Many studies about extinction debt rely on community equilibrium from relationships between species richness and habitat variables. We assumed that the distribution of many vascular plant species in the coastal range of south-central Chile is not in equilibrium with the present habitat distribution. The aim of this research is to quantify patterns of habitat loss and to detect extinction debt from relationships between the current richness of different assemblages of vascular plants (considering longevity and habitat specialization) and both past and current habitat variables. The results showed that native forests have been fragmented and reduced by 53%, with an annual deforestation rate of 1.99%, in the study area between 1979 and 2011. Current richness of plant species was mostly explained by past habitat area and connectivity. Past habitat variables explained best richness of long-lived specialist plants, which are characterized by restricted habitat specialization and slower population turnover. We also showed that habitat fragmentation has resulted in a significant reduction in long-lived plant species’ “dwelling patch sizes (DPS)” between 1979 and 2011. Our analyses provide the first evidence of predicted future losses of plant species in a South American temperate biodiversity hotspot. Consequently, an unknown proportion of the plants in the study area will become extinct if no targeted restoration and conservation action is taken in the near future.

Landscape structure and network characteristics of the greenway system in Guangzhou City, South China Abstract Greenways help to conserve natural areas and improve the quality of life for residents, especially in cities experiencing rapid urbanization. In this study, we evaluated the landscape structure and network characteristics of Guangzhou’s greenway system and analyzed the potential effects of natural and socioeconomic factors on the construction of urban greenways. The total length and density of the greenway system in Guangzhou was 1319.3 km and 0.18 km/km2, respectively. The greenway density in the urban regions was > 1.5 km/km2, which met the optimal threshold requirement for an urban greenway system. Guangzhou’s greenway system had a total of 609 branches and 366 nodes, more than in Xiamen City (China) and Phoenix (AZ), which indicated a high level of network connectivity. The built-up area (area with residential, commercial, or industrial buildings) and the number of intersections of the transportation network were positively and linearly related (R2 = 0.46 and 0.78, respectively) to the length of Guangzhou’s greenways in each 1-km2 pixel grid. Population density (R2 = 0.47, p < 0.001) and gross domestic product per capita (R2 = 0.75, p < 0.001) were positively correlated with the density of Guangzhou’s greenways in each district. These results suggested that greenways were well distributed in the urban regions of Guangzhou. The slope was < 5° for 82.8% of Guangzhou’s greenway system, which made it suitable for walking and biking; 43.7% of the 265 scenic spots were within 400 m, and 64.9% within 800 m, of the nearest greenway, indicating their high accessibility from greenways. However, nearly 50% (273 km) of the waterfront greenways in Guangzhou were adjacent to poor-quality water bodies. The future priority for optimizing Guangzhou’s greenways should be the balancing of environmental protection with social and economic development.