Vulnerability assessment of wetland landscape ecosystem services using driver-pressure-state-impact-response (DPSIR) model

Wetlands exist in complex ecological conditions that are changeable in time and space in terms of function and structural diversity. In recent decades, wetlands have been exposed to a wide range of threats. Assessment of these threats is essential to develop an understanding of the state of a wetland ecosystem and to develop a suitable management strategy. This paper discusses wetland vulnerability in terms of analysis of human and environmental systems from application of the driver-pressure-state-impact-response (DPSIR) framework. This assessment presented a systematic methodology for assessment of wetland vulnerability in a social-ecological approach applying broad-scale ecosystem services and vulnerability functions. The method combined the hydro-geomorphic approach with estimations of vulnerability indicators and DPSIR analysis. The aim of this paper was to assess vulnerability of wetland ecosystem services and to characterize the threat indicators according to importance, severity, and probability of occurrence. Quantitative and qualitative methods were applied to characterize values for these three indicators. The Multi Criteria Decision Making (MCDM) method was used to prioritize threats and impacts of the wetland on the basis of experts’ opinions. The proposed methodology was applied to the Choghakhor international wetland landscape in south-western Iran. Vulnerability assessment revealed that water requirement of the lowland and the water transfer system were the most important factors threatening the wetland. Agricultural activities, settlements and urban areas, drought, tourism, population growth, and mining activities in the upland were the next most important priorities, in that order. Hydrological balance was determined as the most vulnerable function and was considered as the most important function in the Choghakhor wetland. The DPSIR model was used to determine a management strategy to reduce vulnerability of ecosystem services in response to drivers, pressures, states and impacts indicated by modelling.     

Economic values and dominant providers of key ecosystem services of wetlands in Beijing,China

This study estimates the economic values of and the dominant contributors to five key ecosystem services of wetlands in Beijing, by using the wetland inventory data in 2014 and economic valuation methods. Results indicate that the 51,434 ha of wetlands in Beijing annually provide 2.07 billion m³ of flood regulation, 944.01 million m³ of water provision, 42,154 tons of chemical oxygen demand (COD) purification, 3.03 PJ of heat absorption, and 9587 ha of habitat. Their economic values are estimated to be 15.89 billion RMB, 1.19 billion RMB, 169 million RMB, 421 million RMB, and 1.08 billion RMB in 2014 (RMB: Chinese currency, US$1 = RMB 6.14), respectively. The total values of five key wetland ecosystem services reach 18.76 billion RMB. In addition, the reservoir and river wetlands in Miyun, Yanqing, Fangshan, Huairou, and Mentougou Districts contribute 78% of key ecosystem services, whereas the urban wetlands in Xicheng, Dongcheng, Haidian, Chaoyang, and Tongzhou Districts more conveniently serve densely local people, hence they should be given particular attentions. In this paper, we develop the valuation methods of wetland ecosystem services, and recommend diversified strategies, regulations, and programs to protect the remaining wetlands in Beijing. This work can also provide a reference for the valuating of wetland ecosystem services for other urban-rural areas.     

Environmental factors affecting the distribution of aquatic invertebrates in temporary ponds in Mammoth Cave National Park,Kentucky, USA

Despite a recent surge of interest in temporary lentic systems, a strong theory linking the biota to its environment has not emerged. Using data from 10 temporary ponds at Mammoth Cave National Park, Kentucky, USA, we investigated how invertebrate communities were structured along environmental gradients, both between and within ponds. Samples were collected with a benthic corer in winter and spring, and a sweep net in spring. Six between-pond and two within-pond datasets were created. Between-pond analyses yielded significant CCA’s with only one of the six data sets. The ranges of environmental variables (EV’s) within ponds were often similar to the ranges of EV’s when averaged and compared between ponds. Some taxa were aggregated in a single pond, and richness increased with pond area. The theory that richness increases with hydroperiod did not apply to these systems. Within-pond analyses yielded more consistent relationships, with both CCA’s being significant. Sample depth was the best predictor of invertebrate richness and abundance, with most taxa preferring shallow habitats. Richness and abundance were higher in both shallow ponds and shallow areas of deep ponds than in deep areas of deep ponds. Standardizing sample depth may be an effective way to remove this gradient as a confounding variable in future research. The presence of within-pond gradients, possibly coupled with the limited dispersal and random colonization of tolerant taxa, makes between-pond comparisons difficult. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorised users. Handling editor: S. Declerck     

Fingerprinting environmental conditions and related stress using stable isotopic composition of rice (Oryza sativa L.) grain organic matter

Sea level rise (SLR) is a primary factor responsible for inundation of low-lying coastal regions across the world, which in turn governs the agricultural productivity. In this study, rice (Oryza sativa L.) cultivated seasonally in the Kuttanad Wetland, a SLR prone region on the southwest coast of India, were analysed for oxygen, hydrogen and carbon isotopic ratios (δ¹⁸O, δ²H and δ¹³C) to distinguish the seasonal environmental conditions prevalent during rice cultivation. The region receives high rainfall during the wet season which promotes large supply of fresh water to the local water bodies via the rivers. In contrast, during the dry season reduced river discharge favours sea water incursion which adversely affects the rice cultivation. The water for rice cultivation is derived from regional water bodies that are characterised by seasonal salinity variation which co-varies with the δ¹⁸O and δ²H values. Rice cultivated during the wet and the dry season bears the isotopic imprints of this water. We explored the utility of a mechanistic model to quantify the contribution of two prominent factors, namely relative humidity and source water composition in governing the seasonal variation in oxygen isotopic composition of rice grain OM. δ¹³C values of rice grain OM were used to deduce the stress level by estimating the intrinsic water use efficiency (WUE_i) of the crop during the two seasons. 1.3 times higher WUE_i was exhibited by the same genotype during the dry season. The approach can be extended to other low lying coastal agro-ecosystems to infer the growth conditions of cultivated crops and can further be utilised for retrieving paleo-environmental information from well preserved archaeological plant remains.     

Fossil insects and ecosystem dynamics in wetlands: implications for biodiversity and conservation

We review the uses of fossil insects, particularly Coleoptera (beetles) and Chironomidae (non-biting midges) from ancient deposits to inform the study of wetland ecosystems and their ecological and restoration processes. In particular, we focus on two contrasting ecosystems, drawing upon research undertaken by us on British raised mire peats and shallow lake systems, one an essentially terrestrial ecosystem, the other aquatic, but in which wetland insects play an important and integral part. The study of raised mire peats suggests that faunal stability is a characteristic of these wetland systems, over what appear to be extensive periods of time (up to several millennia), whilst studies of shallow lake ecosystems over recent timescales indicates that faunal instability appears to be more common, usually driven by increasing eutrophication. Drawing upon a series of fossil Coleoptera records spanning several thousand years from Hatfield Moors, south Yorkshire, we reconstruct in some detail the mire’s ontogeny and fluctuations in site hydrology and vegetation cover, illustrating the intimate association between substrate, topography and peat development. A comparison between fossil and modern beetle populations indicates that the faunal characteristics of this mire and its adjacent neighbour, Thorne Moors, become established during the early phases of peat development, including its rare endemics, and that the faunal biodiversity on the sites today is dictated by complex site histories. The over-riding characteristic of these faunas is of stability over several thousand years, which has important implications for the restoration of degraded sites, especially those where refugial areas are limited. In contrast, analyses of fossil Chironomidae from shallow lakes allow researchers to track changes in limnological status and while attempts have been made to reconstruct changes in nutrient levels quantitatively, the chironomids respond indirectly to such changes, typically mediated through complex ecosystem dynamics such as changes in fish and/or macrophyte communities. These changes are illustrated via historic chironomid stratigraphies and diversity indices from a range of shallow lakes located across Britain: Slapton Ley, Frensham Great Pond, Fleet Pond, Kyre Pool and Barnes Loch. These sites have shown varying degrees of eutrophication over recent timescales which tends to be associated with a decline in chironomid diversity. While complex functional processes exist within these ecosystems, our evidence suggests that one of the key drivers in the loss of shallow lake chironomid diversity appears to be the loss of aquatic macrophytes. Overall, while chironomids do show a clear response to altered nutrient regimes, multi-proxy reconstructions are recommended for a clear interpretation of past change. We conclude that if we are to have a better understanding of biota at the ecosystem level we need to know more of the complex interactions between different insect groups as well as with other animal and plant communities. A palaeoecological approach is thus crucial in order to assess the role of insect groups in ecosystem processes, both in the recent past and over long time scales, and is essential for wetland managers and conservation organisations involved in long term management and restoration of wetland systems     

Soil and plant tests for available sulfur in wetland rice soils

Summary Soil tests, plant performance, and plant tissue analyses were used to study the availability of sulfur to wetland rice in 30 Philippine soils. The critical concentrations of available sulfur by the calcium phosphate, lithium chloride, ammonium acetate, and hydrochloric acid extractions were 9, 25, 30, and 5 mg/kg, respectively. The critical total sulfur limits were 0.11% in the shoot at maximum tillering 0.055% in the straw at maturity, and 0.065% in the grain. The critical N:S ratio was 15 in the shoot at maximum tillering, 14 in the straw at maturity, and 26 in the grain. The critical sulfate-sulfur limit was 150 mg/kg in the shoot at maximum tillering and 100 mg/kg in the straw at maturity. The critical sulfate-sulfur/total sulfur percentage ratio was 15% in the shoot at maximum tillering and the straw at maturity. Plant performance, judged by appearance and yield of dry matter, straw, and grain, was generally poorer in the sulfur deficient soils than in the other soils. Although the calcium phosphate and ammonium acetate methods gave a better correlation between plant performance and available sulfur than the others, all four methods separated sulfur-deficient soils from non-deficient ones. The hydrochloric acid method merits further study because it is simple and versatile.     

A comparison of soil carbon pools and profiles in wetlands in Costa Rica and Ohio

Wetlands are large carbon pools and play important roles in global carbon cycles as natural carbon sinks. This study analyzes the variation of total soil carbon with depth in two temperate (Ohio) and three tropical (humid and dry) wetlands in Costa Rica and compares their total soil C pool to determine C accumulation in wetland soils. The temperate wetlands had significantly greater (P < 0.01) C pools (17.6 kg C m⁻²) than did the wetlands located in tropical climates (9.7 kg C m⁻²) in the top 24 cm of soil. Carbon profiles showed a rapid decrease of concentrations with soil depth in the tropical sites, whereas in the temperate wetlands they tended to increase with depth, up to a maximum at 18–24 cm, after which they started decreasing. The two wetlands in Ohio had about ten times the mean total C concentration of adjacent upland soils (e.g., 161 g C kg⁻¹ were measured in a central Ohio isolated forested wetland, and 17 g C kg⁻¹ in an adjacent upland site), and their soil C pools were significantly higher (P < 0.01). Among the five wetland study sites, three main wetland types were identified – isolated forested, riverine flow-through, and slow-flow slough. In the top 24 cm of soil, isolated forested wetlands had the greatest pool (10.8 kg C m⁻²), significantly higher (P < 0.05) than the other two types (7.9 kg C m⁻² in the riverine flow-though wetlands and 8.0 kg C m⁻² in a slowly flowing slough), indicating that the type of organic matter entering into the system and the type of wetland may be key factors in defining its soil C pool. A riverine flow-through wetland in Ohio showed a significantly higher C pool (P < 0.05) in the permanently flooded location (18.5 kg C m⁻²) than in the edge location with fluctuating hydrology, where the soil is intermittently flooded (14.6 kg C m⁻²).     

Growing islands and sinking solutes: processes maintaining the endorheic Okavango Delta as a freshwater system

In the Okavango Delta 98–99% of the water from inflow and rainfall is lost to the atmosphere through evapotranspiration. As a consequence 94% of inflowing solutes are retained within the Delta landscape. This process might be expected to result in an entirely saline environment, but that is not the case: the surface waters have very low salinity, supporting a typical freshwater biota. It has been deduced that the numerous islands in the Delta (about 150,000 within an area of 13,500 km²) have been formed through evapotransporative concentration in the groundwater, of infiltrating solutes, followed by precipitation and volume increase. Evidence of this is the large amount of calcrete in island soils. These islands of 3–10 m thickness with clayey soils are underlain by fine Kalahari sand to a depth of 200–300 m, which also indicates that they are formed through surface processes. The infiltration rate of surface water from floodplains and streams into islands is very high, and is predominantly a lateral process that is unidirectional. Evapotranspiration in the riparian woodland zone cause the ground-waters in the central area of islands—with halophyte grasslands—to have very high salinities. By use of chloride as a conservative element the concentration factor between central island groundwater and surface water is calculated to be 500–1,000. This groundwater is depleted of calcium and magnesium supporting the early deductions that these elements have precipitated as calcrete. There is also a large depletion of silicate and potassium that probably have precipitated as well forming the clayey soils typical of the islands. The central island groundwater is dominated by sodium, bicarbonate and dissolved organic matter. The gradual increase of salinity here causes a periodic let off of this water through a density-driven process to deeper layers. This process together with island growth through precipitation of solutes are the two major sink processes of inflowing solutes and explains why the Okavango Delta is at present a freshwater system. The whole island complex is calculated to be 100,000–400,000 years old while some intensely studied islands may be younger: 80,000–240,000 years. The discrepancy is explained by a biassed selection of islands currently in flooded areas with better growth conditions. The uniqueness of the Okavango Delta and ideas for future research are discussed.     

Wetland drying indirectly influences plant community and seed bank diversity through soil pH

High altitude wetlands on the Tibetan Plateau have been shrinking due to anthropogenic disturbances and global climate change. However, the few studies that have been conducted on wetlands are inconclusive about the effect of soil moisture on seed banks and potential of seed banks in wetlands with different levels of soil moisture for regeneration of dried wetlands. We investigated seed banks and plant communities along a soil moisture gradient. A structural equation model was used to analyze the direct and indirect effects of soil moisture on seed banks, as well as the relationship between plant communities and seed banks. Although soil moisture had no direct effects on seed bank richness and density and indirect effects on seed banks through plant community, it had indirect effects on the seed bank through soil pH. Soil moisture also did not have direct effects on plant community richness, but it had indirect effects through soil pH. Plant community composition changed with soil moisture, but aboveground plant abundance and seed banks composition did not change. Low similarity exists between plant community and seed banks for all wetlands, and similarity decreased along the moisture gradient. The key factor determining plant community diversity was soil pH, while seed bank diversity was mainly affected by soil pH and plant community diversity with wetland drying. Although potential for regenerating the plant community from the seed bank decreased with an increase in soil moisture, drained wetlands still have enough residual seeds for successful restoration of species-rich alpine meadows.