An ecological integrity index for littoral wetlands in agricultural catchments of semiarid mediterranean regions

Macroinvertebrate assemblages along a gradient of physicochemical characteristics in four riverine wetlands, Upper Blue Nile basin, Northwestern Ethiopia

This study aims to examine the physicochemical variables that influence macroinvertebrate assemblages in wetlands of the Fetam River watershed. Macroinvertebrates and water quality samples were collected from 20 sampling stations across four wetlands between February and May 2022. Principal component analysis (PCA) was used to elucidate the physicochemical gradients among datasets and canonical correspondence analysis (CCA) was applied to explore the relationship between taxon assemblages and physicochemical variables. Aquatic insects such as Dytiscidae (Coleoptera), Chironomidae (Diptera), and Coenagrionidae (Odonata) were the most abundant families, and they comprised 20-80% of the macroinvertebrate communities. As demonstrated by cluster analysis, three site groups including slightly disturbed (SD), moderately disturbed (MD), and heavily disturbed (HD) sites were identified. PCA showed a clear separation of slightly disturbed sites from moderately and highly impacted sites. Differences in physicochemical variables, taxon richness and abundance, and Margalef diversity indices were observed along the SD to HD gradient. Phosphate concentration was an important predictor that influenced richness and diversity. The extracted two CCA axes of physicochemical variables accounted for 44% of the variability in macroinvertebrate assemblages. Nutrient concentration (nitrate, phosphate, and total phosphorus), conductivity, and turbidity were the main drivers of this variation. This suggested the need for sustainable wetland management intervention at the watershed level, ultimately benefiting invertebrate biodiversity.

Salinity Tolerance in Fraxinus angustifolia Vahl.: Seed Emergence in Field and Germination Trials

The effect of salinity on seed germination/emergence in narrow-leaved ash (Fraxinus angustifolia) was studied both under field and laboratory conditions, in order to detect critical values to NaCl exposure. Research Highlights: Novel statistical methods in germination ecology has been applied (i) to determine the effects of chilling length and salinity (up to 150 mM NaCl) on Fraxinus angustifolia subsp. oxycarpa seed emergence, and (ii) to estimate threshold limits treating germination response to salinity as a biomarker. Background and Objectives: Salinity cut values at germination stage had relevant interest for conservation and restoration aims of Mediterranean floodplain forests in coastal areas subjected to salt spray exposure and/or saline water introgression. Results: Salinity linearly decreased germination/emergence both in the field and laboratory tests. Absence of germination was observed at 60 mM NaCl in the field (70–84 mM NaCl depending on interpolation model) and at 150 mM NaCl for 4-week (but not for 24-week) chilling. At 50 mM NaCl, germination percentage was 50% (or 80%) of control for 4-week (or 24-week) chilling. Critical values for salinity were estimated between freshwater and 50 (75) mM NaCl for 4-week (24-week) chilling by Bayesian analysis. After 7-week freshwater recovery, critical cut-off values included all tested salinity levels up to 150 mM NaCl, indicating a marked resumption of seedling emergence. Conclusions: Fraxinus angustifolia is able to germinate at low salinity and to tolerate temporarily moderate salinity conditions for about two months. Prolonged chilling widened salinity tolerance.

Evaluating dynamic hydrological connectivity of a floodplain wetland in North Bihar, India using geostatistical methods

Spatio-temporal connectivity patterns of a wetland as a function of the land use/land cover (LULC) of its catchment have been analysed in a GIS environment. An innovative method has been implemented for mapping 'dynamic hydrological connectivity' for a water-stressed wetland of Kosi-Ganga interfluve area in the middle Ganga Plains, India for pre- and post-monsoon seasons over a time-span of 29 years (1989 to 2017). It was accomplished by using the time-series NDVI (Normalized Difference Vegetation Index) data and the connectivity response unit (CRU) approach by applying geostatistical methods namely the Getis-Ord Gi* and Mann-Kendall trend test statistics. The study area is principally a rain-fed wetland located in flat terrain (average slope of ~2°) under intensive agriculture and receives water as overland flows. The agriculture dominated LULC in this region is controlling the wetland-catchment connectivity scenarios and the overall connectivity potential of the catchment is higher in the pre-monsoon compared to the post-monsoon season. High and low connectivity potentials of different areas of the catchment with respect to the wetland have been classified into three types: persistent, intensifying, and diminishing. The areas with 'persistent' high or low connectivity potentials have been attributed to the topographic factors which are static in nature, such as the proximity to the wetland and the presence of other geomorphic features. The 'intensifying' and 'diminishing' clusters have been linked to changing LULC patterns. The proposed method holds significant implications for the restoration of wetland-catchment connectivity and can be applied in any flatland terrain where hydrological connectivity is strongly influenced by the surface impedance induced by LULC.

Evaluation of Landscape Ecological Integrity in the Yulin Region, China

We developed a framework and an index to evaluate landscape ecological integrity. The framework was applied to the Yulin region (Shaanxi Province, China) to evaluate its overall ecological integrity and the effect of the Grain for Green Project on landscape ecological integrity. Landscape ecological integrity (LEI) is the ability of an ecosystem to maintain its self-organization capacity, stability, and diversity in structure and function. A landscape having high ecological integrity has three major characteristics: complex structure, high self-organization capacity, and a high level of stability. The LEI can be evaluated using five indicators: landscape fragmentation, connectance, ecological sensitivity, diversity, and vegetation productivity. The results indicate that the LEI in the Yulin region was relatively low during the period from 2000 to 2015. From 2000 to 2005, areas of very low and low LEI decreased, and areas of moderate and high LEI increased. From 2005 to 2010, areas of low and high LEI decreased, and areas of moderate LEI increased. Furthermore, from 2010 to 2015, areas of very low and low LEI increased, and areas of moderate and high LEI decreased. Overall, the LEI of the region was low, but increased between 2000 and 2010, and decreased between 2010 and 2015. On the basis of these findings, we conclude that the Grain for Green Project in the Yulin region has been successful in improving regional LEI.

Non-linear feeding functional responses in the Greater Flamingo (Phoenicopterus roseus) predict immediate negative impact of wetland degradation on this flagship species

Accurate knowledge of the functional response of predators to prey density is essential for understanding food web dynamics, to parameterize mechanistic models of animal responses to environmental change, and for designing appropriate conservation measures. Greater flamingos (Phoenicopterus roseus), a flagship species of Mediterranean wetlands, primarily feed on Artemias (Artemia spp.) in commercial salt pans, an industry which may collapse for economic reasons. Flamingos also feed on alternative prey such as Chironomid larvae (e.g., Chironomid spp.) and rice seeds (Oryza sativa). However, the profitability of these food items for flamingos remains unknown. We determined the functional responses of flamingos feeding on Artemias, Chironomids, or rice. Experiments were conducted on 11 captive flamingos. For each food item, we offered different ranges of food densities, up to 13 times natural abundance. Video footage allowed estimating intake rates. Contrary to theoretical predictions for filter feeders, intake rates did not increase linearly with increasing food density (type I). Intake rates rather increased asymptotically with increasing food density (type II) or followed a sigmoid shape (type III). Hence, flamingos were not able to ingest food in direct proportion to their abundance, possibly because of unique bill structure resulting in limited filtering capabilities. Overall, flamingos foraged more efficiently on Artemias. When feeding on Chironomids, birds had lower instantaneous rates of food discovery and required more time to extract food from the sediment and ingest it, than when filtering Artemias from the water column. However, feeding on rice was energetically more profitable for flamingos than feeding on Artemias or Chironomids, explaining their attraction for rice fields. Crucially, we found that food densities required for flamingos to reach asymptotic intake rates are rarely met under natural conditions. This allows us to predict an immediate negative effect of any decrease in prey density upon flamingo foraging performance.

Selection of ecological indicators for the conservation, management and monitoring of Mediterranean coastal salinas

Salinas systems are artificial wetlands which are interesting from the viewpoint of nature conservation. They play an important role both as habitats for migratory waterbird species and as nodes of biotic connectivity networks. In the Mediterranean basin, where the coastal salinas are highly significant as alternative and complementary habitats for waterbirds, a process of abandonment occurs, and many seminatural systems of this kind are disappearing. This abandonment is having serious consequences for migratory bird populations and for the ecological role these play. In the present paper, this group of waterbird species has been used to evaluate these wetlands for conservation purposes. We have developed a methodological approach for the selection of ecological indicators for the conservation and management of these Mediterranean habitats and waterbird assemblages, the main consumers therein. The stepwise procedure developed constitutes a practical tool for this task. Application thereof enabled us to differentiate the habitats available for the waterbirds and to identify the biotic and abiotic indicators for the maintenance and management of the salina ecosystems. These variables can then be incorporated into monitoring programs.

Eco-environmental evolution, control, and adjustment for Aibi Lake catchment

Aibi Lake in north Xinjiang is a typical lake of the arid area, but with a peculiar wetland-arid area ecosystem. Due to the climate becoming drier and the disturbance of human activities, the eco-environment of Aibi Lake catchment has degraded. It was found in our study that there were spatial-temporal changes of vegetation cover, plant species, and soil physical and chemical properties in the catchment. In the upper section of alluvial-fluvial plains, the desertified steppe of Stipa and Artemisia spp. is developed with vegetation cover of some 50%. Haloxylon ammodendron desert occupies the lower section with vegetation cover of some 60%. In these regions with an intensive human disturbance, vegetation has degraded into herb vegetation of annual plant complexes. On the margins of the alluvial-fluvial fans, the lakeshore, and the surrounding regions where the river mouths join the lake, different azonal vegetation-Phragmites communis marsh, Phragmites communis meadow, and Tamarix shrubs-have developed with a vegetation cover of some 80%. On heavier, salinized land, succulent halophyte desert vegetation dominated by Halocnemum strobilaceum has formed with a fractional canopy cover of 10-15%. Haloxylon persicum, Aristida pennata, and other species with a vegetation cover of 30-50% grow in the sand desert zone on the periphery in the lake. In contrast with the 1950s, the vegetation cover around the lakebed and at the river deltas has slightly increased; however, the vegetation cover around the periphery of the lake has decreased and the plant species have still degraded. The surface soils on the windward area and the dried lakebed that have lost vegetation protection have become coarser, whereas the land on the leeward side of the lake has accumulated fine particles. In contrast with the 1980s, soil organic matter has declined markedly. The analyses of climatic data show that the number of days of drifting dust in Jinghe County and Bole City increased in the last 20 years. In the investigation, we found that intensively developed land, the bare lakebed, and abandoned cultivated land provided a great deal of material for drifting dust. In conclusion, we consider the eco-environmental degradation resulting from the inappropriate human activities and put forward recommendations for land-use adjustment and dust control.