Invasive Water Hyacinth Limits Globally Threatened Waterbird Abundance and Diversity at Lake Cluster of Pokhara Valley, Nepal

Invasive species alter ecosystem structure and functioning, including impacts on native species, habitat alteration, and nutrient cycling. Among the 27 invasive plant species in Nepal, water hyacinth (Eichhornia crassipes) distribution is rapidly increasing in Lake Cluster of Pokhara Valley (LCPV) in the last several decades. We studied the effects of water hyacinth on threatened waterbird abundance, diversity, and physico-chemical parameters of water in the LCPV. We found areas with water hyacinth present (HP) had reduced threatened water bird abundance relative to areas where water hyacinth was absent (HA; p = 0.023). The occurrence of birds according to feeding guilds also varied between water hyacinth presence and absence habitats. Piscivorous birds were more abundant in HA areas than HP areas whereas insectivorous and omnivorous birds had greater abundance in HP areas than in HA areas. Threatened waterbird abundance and richness were greater in areas with greater water depth and overall bird abundance but declined in HP areas. Degraded water quality was also identified in HP areas. Our findings can be used as a baseline by lake managers and policy makers to develop strategies to remove or manage water hyacinth in LCPV to improve waterbird conservation.

Fire’s Effects on Grassland Restoration and Biodiversity Conservation

Ecosystem succession and biodiversity change associated with grassland fires are crucial for the patterns and dynamics of ecosystem functioning and services. The reactions to fire by different grassland types vary diversely, and are determined by certain species assemblages and environments. However, there are still uncertainties concerning the role of fire in affecting grassland ecosystems and how the effects are sustained. By conducting a bibliometric analysis of related articles indexed in the Web of Science between 1984 and 2020, we firstly described the general trend of these articles over the recent decades (1984–2020). The major research progress in the effects of fire on grassland ecosystems was then systematically summarized based on three levels (individual level, community level, and ecosystem level) with eight topics. We concluded that strong persistence or resistance of adapted individuals facilitated community conversion to a novel environment, which temporally and spatially interacted with ecological factors. The novel habitats could maintain more frequent fires and change an ecosystem structure and functioning. Nonetheless, the transformation of ecosystem states will present more uncertainties on prospective succession trajectories, global carbon storage, and subsequent biodiversity conservation. This review is important to flourish biodiversity, as well as aid conservation policies and strategy making.

Dynamic Role and Importance of Multi-Kingdom Communities in Mediterranean Wood-Pastures

Wood-pastures are among the most valuable types of farmland for ecosystem services, including biodiversity, landscape, soil protection, water management and cultural values. This paper reviews the scientific literature regarding the dynamic role and importance of plant, fungal and ruminant communities in Mediterranean wood-pastures and assesses the favorable and unfavorable aspects of their occurrence through grazing management. The grasslands of the Mediterranean region play an important role both in forage material production and the conservation of biodiversity in plant communities and at the landscape level. These two management purposes are not conflicting but complementary when the management is based upon the knowledge of the effect of grazing on the ecology of these ecosystems. Conclusively, vascular plant, fungal and ruminant communities have a strong influence on ecosystem structure and functioning and they play a key role in many ecological services. Hence, integrated studies which combine multi-level ecological research are essential in order to identify regional and/or national needs in terms of biodiversity, genetic resources, sustainable rural development and conservation policies.

Reconstructing Bioinvasion Dynamics Through Micropaleontologic Analysis Highlights the Role of Temperature Change as a Driver of Alien Foraminifera Invasion

Invasive alien species threaten biodiversity and ecosystem structure and functioning, but incomplete assessments of their origins and temporal trends impair our ability to understand the relative importance of different factors driving invasion success. Continuous time-series are needed to assess invasion dynamics, but such data are usually difficult to obtain, especially in the case of small-sized taxa that may remain undetected for several decades. In this study, we show how micropaleontologic analysis of sedimentary cores coupled with radiometric dating can be used to date the first arrival and to reconstruct temporal trends of foraminiferal species, focusing on the alien Amphistegina lobifera and its cryptogenic congener A. lessonii in the Maltese Islands. Our results show that the two species had reached the Central Mediterranean Sea several decades earlier than reported in the literature, with considerable implications for all previous hypotheses of their spreading patterns and rates. By relating the population dynamics of the two foraminifera with trends in sea surface temperature, we document a strong relationship between sea warming and population outbreaks of both species. We conclude that the micropaleontologic approach is a reliable procedure for reconstructing the bioinvasion dynamics of taxa having mineralized remains, and can be added to the toolkit for studying invasions.

Ecological mechanisms underlying aridity thresholds in global drylands

With ongoing climate change, the probability of crossing environmental thresholds promoting abrupt changes in ecosystem structure and functioning is higher than ever. In drylands (sites where it rains less than 60% of what is evaporated), recent research has shown how the crossing of three particular aridity thresholds (defining three consecutive phases, namely vegetation decline, soil disruption and systemic breakdown) leads to abrupt changes on ecosystem structural and functional attributes. Despite the importance of these findings and their implications to develop effective monitoring and adaptation actions to combat climate change, we lack a proper understanding of the mechanisms unleashing these abrupt shifts.Here we revise and discuss multiple mechanisms that may explain the existence of aridity thresholds observed across global drylands, and discuss the potential amplification mechanisms that may underpin hypothetical abrupt temporal shifts with climate change. We found that each aridity threshold is likely involving specific processes. In the vegetation decline phase we review mainly physiological mechanisms of plant adaptation to water shortages as main cause of this threshold. In the second threshold we identified three pathways involving mechanisms that propagates changes from plants to soil leading to a soil disruption: erosive mechanisms, mechanisms linked to an aridity-induced shrub encroachment and mechanisms linked to nutrient cycling and circulation. Finally, in the systemic breakdown phase we reviewed plant-plant amplification mechanisms triggered by survival limits of plants that may cause sudden diversity losses and plant-atmospheric feedbacks that may link vegetation collapse with further and critical aridification. By identifying, revising and linking relevant mechanisms to each aridity threshold, we catalogued a set of specific hypotheses and recommendations based on identified knowledge gaps concerning the study of mechanisms of threshold emergence in drylands. Moreover, we were able to establish plausible factors that are context dependent and may influence the occurrence of abrupt changes in time and we created a mechanistic-based conceptual model on how abrupt changes may emerge as aridity increases. This has importance for focusing future research efforts on aridity thresholds and for developing strategies to track, adapt to or even revert these abrupt ecosystem changes in the future.

A conceptual framework of drought legacies in grasslands

<p>As a consequence of climate change, extreme climatic events such as droughts will become more frequent and severe, affecting ecosystem structure and functioning, with implications for humans and society. While concurrent effects of drought events are comparatively well studied, the short- and longer-term changes in ecosystem structure and functioning triggered by drought (i.e. drought legacies) are far less understood. Furthermore, it has rarely been analysed how drought legacies alter the resistance to and recovery from subsequent drought events. To assess the overall impact of drought events on ecosystems and emerging cascading effects on societies, we need to advance the understanding of drought legacies and their long-lasting impacts on ecosystems. Based on a review of the literature on above- and belowground mechanisms underlying drought legacies in grasslands, we propose a conceptual framework, which identifies the factors determining the shape of potential legacy trajectories during recovery and post-recovery phases and synthesize the mechanisms leading to legacy responses to subsequent drought events.</p>

Comparison of approaches for incorporating depredation on fisheries catches into Ecopath

Ecosystem-based approaches are increasingly used in fisheries management to account for the direct trophic impacts of fish population harvesting. However, fisheries can also indirectly alter ecosystem structure and functioning, for instance via the provision of new feeding opportunities to marine predators. For instance, marine depredation, where predators feed on fishery catches on fishing gear, is a behaviour developed by many marine species globally. This behaviour can modify both the ecological role of predators and fisheries performance. Yet, these ecosystem-wide effects of depredation are rarely considered holistically. In this study, we explored different ways of incorporating depredation into an Ecopath trophic model. We assessed, through a subantarctic case study, how three alternative model structures can account for depredation effects on fishery catches, predator and non-commercial prey populations, as well as target fish stocks. While none adequately addresses all facets of depredation, the alternative models can to some extent capture how depredation can lead to increased fishing pressure on stocks. As structural specificities of Ecopath prevented us from representing other depredation effects such as provisioning effects for predator populations, we conclude this study with a set of guidance to effectively capture the complex effects of depredation in marine ecosystems and fisheries models.

The MARAS dataset, vegetation and soil characteristics of dryland rangelands across Patagonia

We present the MARAS (Environmental Monitoring of Arid and Semiarid Regions) dataset, which stores vegetation and soil data of 426 rangeland monitoring plots installed throughout Patagonia, a 624.500 km2 area of southern Argentina and Chile. Data for each monitoring plot includes basic climatic and landscape features, photographs, 500 point intercepts for vegetation cover, plant species list and biodiversity indexes, 50-m line-intercept transect for vegetation spatial pattern analysis, land function indexes drawn from 11 measures of soil surface characteristics and laboratory soil analysis (pH, conductivity, organic matter, N and texture). Monitoring plots were installed between 2007 and 2019, and are being reassessed at 5-year intervals (247 have been surveyed twice). The MARAS dataset provides a baseline from which to evaluate the impacts of climate change and changes in land use intensity in Patagonian ecosystems, which collectively constitute one of the world´s largest rangeland areas. This dataset will be of interest to scientists exploring key ecological questions such as biodiversity-ecosystem functioning relationships, plant-soil interactions and climatic controls on ecosystem structure and functioning.