Ecology of Terrestrial Arthropods in Freshwater Wetlands

Ecological responses to hydrological connectivity in grassland riparian zones: Insights from vegetation and ground-dwelling arthropods

Riparian wetlands have suffered from degradation due to global climate change and human activities, which can alter flora and fauna community patterns and disrupt material cycles in the riparian zones. Hydrological connectivity identified by functional and structural connectivity is an important driving force of riparian ecosystems. However, the role of hydrological connectivity in linking riparian hydrology and ecology remains unclear, especially in dryland rivers. By taking the riparian zone of the Xilin River in Eurasian steppe as an example, the functional connectivity was represented by the groundwater depth in the riparian zones. The structural connectivity was quantified by integrating the soil, and vegetation properties of the riparian zone. The structural connectivity decreased from upstream to downstream. Laterally, the highest structural connectivity was found in the riparian zone 25 m away from the river channel. The abundance of three groups of ground-dwelling arthropods (except Araneae) showed a threshold behavior in response to the functional connectivity, with the highest abundance occurring in the medium level of functional connectivity. Both vegetation biomass and ground-dwelling arthropod abundance were significantly and positively correlated to the structural connectivity strength. The results of structural equation models (SEMs) also indicated that structural connectivity was a key factor affecting vegetation and ground-dwelling arthropod abundance. The results underscore the essential function of hydrological connectivity in maintaining the biodiversity in the riparian zones. The study provides a scientific reference of riparian-zone restoration based on hydrological connectivity.

Tradeoffs and synergies in wetland multifunctionality: A scaling issue

Wetland area in agricultural landscapes has been heavily reduced to gain land for crop production, but in recent years there is increased societal recognition of the negative consequences from wetland loss on nutrient retention, biodiversity and a range of other benefits to humans. The current trend is therefore to re-establish wetlands, often with an aim to achieve the simultaneous delivery of multiple ecosystem services, i.e., multifunctionality. Here we review the literature on key objectives used to motivate wetland re-establishment in temperate agricultural landscapes (provision of flow regulation, nutrient retention, climate mitigation, biodiversity conservation and cultural ecosystem services), and their relationships to environmental properties, in order to identify potential for tradeoffs and synergies concerning the development of multifunctional wetlands. Through this process, we find that there is a need for a change in scale from a focus on single wetlands to wetlandscapes (multiple neighboring wetlands including their catchments and surrounding landscape features) if multiple societal and environmental goals are to be achieved. Finally, we discuss the key factors to be considered when planning for re-establishment of wetlands that can support achievement of a wide range of objectives at the landscape scale.

Warming in Cold Seasons Increases the Abundance of Ground-Dwelling Collembola in Permafrost Wetlands

The consideration of environmental factors has long been crucial to developing theories about the spatial variability of species diversity. However, the effects of global warming on Collembola, in permafrost wetlands, are largely unknown. Understanding how Collembola are affected by climate warming is important as they directly affect the community assembly and decomposition processes of plant litter within soil ecosystems. A peatland area in a cold temperate monsoon climate zone in the Great Hing'an Mountains of Northeast China was selected as the study area. Collembola were captured using an aspirator after five years of simulated warming using open top chambers (OTCs). Sampling in different growth seasons showed different characteristics in the control (CK) and warming (OTCs) treatment. Further, the results showed that (1) warming treatment increased the species richness and abundance of Collembola in the different seasons, except in May, (2) warming increased Collembola abundance in permafrost wetlands, and the warming effect was more significant during the cold season (about eight times in April), (3) species composition differed significantly in the control and warming treatment in May and September, and (4) the Collembola species composition in permafrost wetlands was mainly determined by air humidity, indicating different responses of Collembola species to the indirect effect of warming on water availability. We found that warming was the primary factor positively affecting the abundance of Collembola. An increase of Collembola abundance and community alteration to warming could have profound cascading effects on the microbes and plants they feed on in permafrost wetlands.

Species composition of shoreline wolf spider communities vary with salinity, but their diets vary with wrack inflow

Wolf spiders are typically the most common group of arthropod predators on both lake and marine shorelines because of the high prey availability in these habitats. However, shores are also harsh environments due to flooding and, in proximity to marine waters, to toxic salinity levels. Here, we describe the spider community, prey availabilities, and spider diets between shoreline sites with different salinities, albeit with comparatively small differences (5‰ vs. 7‰). Despite the small environmental differences, spider communities between lower and higher saline sites showed an almost complete species turnover. At the same time, differences in prey availability or spider gut contents did not match changes in spider species composition but rather changed with habitat characteristics within a region, where spiders collected at sites with thick wrack beds had a different diet than sites with little wrack. These data suggest that shifts in spider communities are due to habitat characteristics other than prey availabilities, and the most likely candidate restricting species in high salinity would be saline sensitivity. At the same time, species absence from low-saline habitats remains unresolved.

Nonlinear effects of environmental drivers shape macroinvertebrate biodiversity in an agricultural pondscape

Agriculture is a leading cause of biodiversity loss and significantly impacts freshwater biodiversity through many stressors acting locally and on the landscape scale. The individual effects of these numerous stressors are often difficult to disentangle and quantify, as they might have nonlinear impacts on biodiversity. Within agroecosystems, ponds are biodiversity hotspots providing habitat for many freshwater species and resting or feeding places for terrestrial organisms. Ponds are strongly influenced by their terrestrial surroundings, and understanding the determinants of biodiversity in agricultural landscapes remains difficult but crucial for improving conservation policies and actions. We aimed to identify the main effects of environmental and spatial variables on α‐, β‐, and γ‐diversities of macroinvertebrate communities inhabiting ponds (n = 42) in an agricultural landscape in the Northeast Germany, and to quantify the respective roles of taxonomic turnover and nestedness in the pondscape. We disentangled the nonlinear effects of a wide range of environmental and spatial variables on macroinvertebrate α‐ and β‐biodiversity. Our results show that α‐diversity is impaired by eutrophication (phosphate and nitrogen) and that overshaded ponds support impoverished macroinvertebrate biota. The share of arable land in the ponds' surroundings decreases β‐diversity (i.e., dissimilarity in community), while β‐diversity is higher in shallower ponds. Moreover, we found that β‐diversity is mainly driven by taxonomic turnover and that ponds embedded in arable fields support local and regional diversity. Our findings highlight the importance of such ponds for supporting biodiversity, identify the main stressors related to human activities (eutrophication), and emphasize the need for a large number of ponds in the landscape to conserve biodiversity. Small freshwater systems in agricultural landscapes challenge us to compromise between human demands and nature conservation worldwide. Identifying and quantifying the effects of environmental variables on biodiversity inhabiting those ecosystems can help address threats impacting freshwater life with more effective management of pondscapes.

Optimal settings and advantages of drones as a tool for canopy arthropod collection

The growing field of aeroecology is limited by difficulties associated with sampling in the air column. Aerial insects are particularly hard to sample, despite being the main prey in the air column, with some recent studies attempting to use drones as a collection method. We conducted a study to determine the optimal drone settings for collecting insects above the canopy, where drones are seldom used. By attaching a net to the body of a small, commercial drone, we tested yield from different height, speed, and net settings in wetlands, as well as compared insect diversity across different habitat canopies. Height was the most important setting; grazing the canopy yielded significantly more insects than flying one meter above it. Speed, drone type, and net size did not influence the number of insects caught per trial. Wetland canopies had higher abundance, diversity, and species richness in its arthropod populations compared to forest canopies or lakes. Compared to the yield of Lindgren funnels-a traditional sampling method in entomology-drones captured higher diversity and abundance of insects in a fraction of the time. This study confirms that drones are an efficient and accurate way to collect canopy arthropods.

A report on the butterfly (Lepidoptera: Rhopalocera) diversity of the Upper Ganga River Ramsar site in Uttar Pradesh, India

This study provides a primary inventory of the butterfly diversity of the Upper Ganga River Ramsar site in Uttar Pradesh, India. The study was carried out in two phases, first in March 2019 and then in November 2019. A total of 44 species of butterflies belonging to 34 genera and five families were seen in the area. The species observed in the study site belonged to the families Hesperiidae (4 genera, 4 species), Lycaenidae (4 genera, 4 species), Nymphalidae (18 genera, 24 species), Papilionidae (2 genera, 4 species), and Pieridae (6 genera, 8 species). Three of these species are legally protected under various schedules of the Indian Wildlife Protection Act (1972).

Water table decline alters arthropod community structure by shifting plant communities and leaf nutrients in a Tibetan peatland

Water table decline is one of the most serious environmental problems in the peatland in the Qinghai-Tibetan Plateau. However, the effect of water table decline on the structure of aboveground arthropod communities is still not clear. We investigated changes in the abundance of different arthropod groups, and estimated the abundance, height, and biomass of the plant community in a soil water table reduction experiment to reveal the effect of water table decline on the arthropod community structure. The effect of water level decline on herbivorous arthropods varied according to the feeding habits. Specifically, water table decline treatment decreased the abundance of grass-preferring herbivores but increased the abundance of forb-preferring herbivores. However, the density of predators (e.g., spiders) did not change significantly. The variations in arthropod communities were correlated with the increase in forbs and leaf nitrogen content in the water table decline treatments. Our experiment demonstrated that the effect of water table decline on plant communities cascades upwardly to alter the arthropod community. Such trophic interactions should be considered in studies aimed at predicting shifts in the arthropods communities in a changing climate.

Landscape transformation of an urban wetland in Kashmir Himalaya, India using high-resolution remote sensing data, geospatial modeling, and ground observations over the last 5 decades (1965-2018)

Wetlands are among the most vulnerable and dynamic ecosystems of the world. Any change in the anthropogenic footprint or climate affects the health of these pristine ecologically and socioeconomically important ecosystems. In the present study, land use land cover changes (LULCC) and fragmentation of natural landscape changes in an urban wetland, Khushalsar, located in the heart of the Srinagar City, were assessed using high-resolution satellite data, geospatial modeling approach, and ground observations over the last ~ 5 decades (1965 and 2018). The spatiotemporal changes in LULC of the wetland were assessed for 3 time periods that include 1965-1980, 1980-2018, and 1965-2018. Additionally, landscape fragmentation tool (LFT) was used to quantify fragmentation of land cover. The analysis of LULCC indicated that built-up areas in the vicinity of the wetland increased by 510% between 1965 and 2018. The aquatic vegetation and marshy lands increased by 150% and 33% respectively. The area under agriculture, plantation, open water, and barren lands decreased mostly taken over by built-up areas. Within the wetland, the area under open water spread reduced by 75% while the aquatic vegetation increased by 150% from 1965 to 2018. The built-up areas including roads also showed a substantial increase. The LFT analysis revealed four categories of landscapes i.e., patch, edge, perforated, and core areas. Since the natural land cover types were taken over by land use predominantly built-up areas, the core natural areas and perforated landscapes in the Khushalsar shrunk by 34% and 94% respectively indicating fragmentation of natural environment. The lack of sewage treatment facility, reckless unplanned urbanization within and in the vicinity of the wetland, is responsible for the degradation of the Khushalsar wetland.

Classifying Streamflow Duration: The Scientific Basis and an Operational Framework for Method Development

Streamflow duration is used to differentiate reaches into discrete classes (e.g., perennial, intermittent, and ephemeral) for water resource management. Because the depiction of the extent and flow duration of streams via existing maps, remote sensing, and gauging is constrained, field-based tools are needed for use by practitioners and to validate hydrography and modeling advances. Streamflow Duration Assessment Methods (SDAMs) are rapid, reach-scale indices or models that use physical and biological indicators to predict flow duration class. We review the scientific basis for indicators and present conceptual and operational frameworks for SDAM development. Indicators can be responses to or controls of flow duration. Aquatic and terrestrial responses can be integrated into SDAMs, reflecting concurrent increases and decreases along the flow duration gradient. The conceptual framework for data-driven SDAM development shows interrelationships among the key components: study reaches, hydrologic data, and indicators. We present a generalized operational framework for SDAM development that integrates the data-driven components through five process steps: preparation, data collection, data analysis, evaluation, and implementation. We highlight priorities for the advancement of SDAMs, including expansion of gauging of nonperennial reaches, use of citizen science data, adjusting for stressor gradients, and statistical and monitoring advances to improve indicator effectiveness.