Cause Of Decline Research Articles

The urge of conserving tradition from climate change: A case study of Darjeeling Himalayan large cardamom-based traditional agroforestry farming system

Large cardamom-based traditional agroforestry is an important farming system of the Darjeeling Himalayas. The present study assessed the status of large cardamom-based traditional agroforestry in the context of climate change along with the grower's perception of climate change, the impacts of climate change on this farming system, observed issues and their solutions. Primary data were collected through a semi-structured questionnaire from 100 cardamom growers selected using a multi-stage random sampling technique and analysed using a five-point Likert Scale. A total of 55% of surveyed growers perceived the impacts of climate change, manifested as changed livelihood (59%), visiting times of animals (65%), tree composition of the farming system (56%) and large cardamom phenology (42%). The majority (82%) of the growers were concerned about the decrease in the area and productivity of traditional large cardamom farming systems, and 94% expressed concerns about climate change mediated increased infestation of diseases and pests and decreased pollinator populations. Other concerns expressed by survey respondents included inadequate marketing (92%), inadequate management or cultural operations (82%) and limited extension services for capacity building (78%). The unavailability of quality planting material of large cardamom was expressed as a cause of decline by only 52% of the growers, although all respondents believed that the traditional large cardamom cultivars are inferior with low yield and susceptible to climate change mediated increased infestation by disease and pests. The majority of the growers were aware of the ecosystem services provided by large cardamom-based traditional agroforestry, such as temperature regulation (55%), improved air quality (57%), shelter to livestock and wildlife (60%), prevention of soil erosion and improvement of soil fertility (79%), and empowerment through higher income (58%). Although the majority of growers (68%) did not consider large cardamom farming systems as having significant economic worth as the farming system is unable to ensure high economic returns, all surveyed Darjeeling cardamom growers hailed their traditional large cardamom farming system as an heirloom while approximately 75% noted it as a source of cultural pride and the majority (70%) of the growers expressed a desire to continue the tradition of large cardamom. The Darjeeling growers surveyed suggested a range of solutions to revive their dying traditional farming, the most essential of which was deemed to be adequate training and extension for capacity building including institutional support (96%) followed by shade tree management and replanting of old plantations (74%), adequate market support and linkage (73%), suitable and timely post-harvest practices (77%), availability of high yielding pest and disease tolerant cultivars (62%) and appropriate and timely agronomic or cultural practices (47%). A revised policy platform to empower the growers through capacity building, institutional support and crop insurance schemes are recommended along with ensuring livelihood diversity and security to create proper human-environment interactions to revive the dying tradition of large cardamom-based agroforestry farming in the Darjeeling Himalayas. Additional future research is needed to clearly identify the factors that most influence harmonious human-environment interaction for improved insight into the dynamism of adaptation.

Integrating GIS, Remote Sensing, and Citizen Science to Map Oak Decline Risk across the Daniel Boone National Forest

Oak decline is a general term used for the progressive dieback and eventual mortality of oak trees due to many compounding stressors, typically a combination of predisposing, inciting, and contributing factors. While pinpointing individual causes of decline in oak trees is a challenge, past studies have identified site and stand characteristics associated with oak decline. In this study, we developed a risk map of oak decline for the Daniel Boone National Forest (DBNF), combining GIS, remote sensing (RS), and public reporting (citizen science, CS). Starting with ground reports of decline (CS), we developed a site-scale model (GIS and RS) for oak decline based on four previously identified predisposing factors: elevation, slope, solar radiation, and topographic wetness. We found that areas identified in the model as having a high oak decline risk also reflected areas of observed oak decline (CS). We then optimized and expanded this risk model to the entire range of the DBNF, based on both site characteristics (as piloted for the case study site) and stand inventory data. The stand inventory data (including species composition and age) further improved the model, resulting in a risk map at the landscape level. This case study can serve as a planning tool and highlights the potential usefulness of integrating GIS, remote sensing, and citizen science.

Multidisciplinary baselines quantify a drastic decline of mussel reefs and reveal an absence of natural recovery

AbstractThe onset of the Anthropocene has coincided with enormous global declines in natural ecosystems, leading to losses in the valuable goods and ecosystem services they provide. This global decline, in conjunction with growing recognition of the ecological importance of natural ecosystems, has generated a pressing need for restoration. Effective ecosystem restoration relies on accurate identification of the cause of decline and clear metrics of success, which are only possible with baseline data of both the pre‐degradation and pre‐restoration ecosystems. However, the establishment of these baselines can be difficult as different potential information sources each have benefits and drawbacks. Determining an efficient method to balance these diverse information sources and generate robust baselines is vital to achieving the United Nations' goal of massively scaled‐up ecosystem restoration. Here we expand on the concept of multidisciplinary baselines, or the combined use of sources and methods across a wide disciplinary spectrum to establish comprehensive and reliable ecosystem baselines, and use mussel reefs in the South Island of New Zealand as a test case. Using a combination of comprehensive historical review, extensive shoreline surveys, and local ecological knowledge, we demonstrate that local mussel abundances decreased by 97% since the mid‐1960s as a result of overharvesting, leaving the extant populations scattered, small, and without recovery. This study demonstrates that harnessing multidisciplinary baselines allows for the consolidation of qualitative and quantitative estimates of ecosystem change over hundreds of years, as well as confirmation of causes of ecosystem degradation, and clear documentation of current ecosystem state beyond what is possible from any individual source. This approach to establishing ecosystem baselines also provides valuable avenues for the advancement of restoration by quantifying the temporal and geographic scales of ecosystem decline, identifying areas for intervention, and establishing clear metrics of success.

Interactions among science, environmental policy and public perception in a Mississippi River Delta assimilation wetland

In November 2006, the City of Hammond, Louisiana, began discharging secondarily treated, disinfected municipal effluent through a distribution pipeline to a 14,000 ha emergent wetland complex referred to as the East Joyce Wetlands. The primary goals were to improve local water quality by taking effluent that would normally be discharged to local waterways and directing it to wetlands that were hydrologically isolated and degraded by saltwater intrusion. During the 2007 growing season there was robust growth of marsh vegetation with a near doubling of productivity compared to controls, however, during winter 2007 there was a massive decline in vegetation and transition to open water in the 121 ha of wetlands in the direct path of effluent discharge. Herbivory by nutria was found to be the cause of the decline, but not before several other causes were hypothesized and largely accepted by the public, specifically that the cause of the vegetation decline was due to excess nutrients that increased rates of soil decomposition and limited root growth of plants. Studies show these hypotheses were flawed due to scale and methodology issues. Intensive nutria removal began in the spring of 2008 and continued through the winter of 2008–2009, with approximately 2000 nutria killed, and vegetation recovery began during the spring of 2009, which was most pronounced and consistent nearest the discharge pipe. Vegetative cover increased dramatically from the near complete loss after nutria grazing to near 80% by 2015, and wetland recovery has continued to the present.

Declining clinical skills in medical education: A perspective on its causes and potential solutions

The medical education is undergoing decline in clinical training during the last 40 years. The Medical Interview of the patient and Physical Examination to arrive at a provisional diagnosis are replaced mostly by advanced diagnostic tests and procedures, after enquiry of the symptoms. This is leading to wrong diagnoses, delayed diagnoses, increase in cost, unfavorable outcome and many a time litigation and compensation against the doctor and hospital. The article outlines cause of decline in clinical skill and points to possible solution.

Modern Methods of Diagnostics and Treatment of Neurodegenerative Diseases and Depression.

This paper discusses the promising areas of research into machine learning applications for the prevention and correction of neurodegenerative and depressive disorders. These two groups of disorders are among the leading causes of decline in the quality of life in the world when estimated using disability-adjusted years. Despite decades of research, the development of new approaches for the assessment (especially pre-clinical) and correction of neurodegenerative diseases and depressive disorders remains among the priority areas of research in neurophysiology, psychology, genetics, and interdisciplinary medicine. Contemporary machine learning technologies and medical data infrastructure create new research opportunities. However, reaching a consensus on the application of new machine learning methods and their integration with the existing standards of care and assessment is still a challenge to overcome before the innovations could be widely introduced to clinics. The research on the development of clinical predictions and classification algorithms contributes towards creating a unified approach to the use of growing clinical data. This unified approach should integrate the requirements of medical professionals, researchers, and governmental regulators. In the current paper, the current state of research into neurodegenerative and depressive disorders is presented.

Population Dynamics of Shark Species in the Coast Of Ghana, West Africa

This study aimed at assessing the growth and mortality parameters of the Prionace gluaca and Sphyrna lewini shark species from the coast of Ghana. Data was taken for nine (9) months from April 2021 to December 2021. The length data taken from the shark species was analyzed for the estimation of population parameters using the FiSAT II tool. From the results, the estimated asymptotic length (L∞) and the growth rate (K) of P. glauca and S. lewini were 396.4 cm and 0.27 yr–1 and 349.1 cm and 0.24 yr–1 respectively, indicating that these species exhibited slow growing characteristics, evinced by a longevity of approximately 11 – 12 years. The length at first capture (Lc50) for P. gluaca was 128.6 cm and that for S. lewini was 169.0 cm. The length at first maturity (Lm50) for P. gluaca and S. lewini was 179.74 cm and 160.4 cm respectively. By comparing the Lc50 and Lm50, it implies that individuals of P. gluaca were vulnerable to fishing gears before having the chance to mature and even spawn once. The total mortality (Z), natural mortality (M), fishing mortality (F) and the exploitation rates for P. glauca and S. lewini were 0.82 yr–1 , 0.22 yr–1 , 0.60 yr–1 and 0.73 and 0.76 yr–1, 0.21 yr–1, 0.55 yr–1 and 0.72, respectively. This suggests that fishing activities are the main cause of decline in the abundance of these shark species. The exploitation rate (E > 0.5) revealed that these species are overexploited in Ghana’s marine waters. Based on these findings, it is recommended that fishing effort be reduced through appropriate measures by relevant authorities.
 Vol. 9, No. 3, December 2022: 353-365

Identifying imperilled fish species and potential causes of decline in the Himalaya biodiversity hotspot

Abstract Despite the global nature of the aquatic biodiversity crisis, drivers of extirpation vary among regions, making local‐level data collection crucial for adaptive management in understudied regions like the Himalaya Biodiversity Hotspot (HBH). As human population growth, economic development and environment change accelerate across the HBH it is important to identify imperilled species and determine any ecological traits that predispose them to extirpation. In the present study, Monte Carlo analysis was used to determine fish species with significant range reductions (‘significantly declining species’) from the 1980s to the 1990s, and from the 1990s to the 2010s, at 38 sites on Nepal’s Kaligandaki–Narayani River (KNR). Relative to a null model under which all species were equally likely to lose individuals between time periods, distributions of 16 of 83 species declined significantly across at least one of the two time periods, and two species, Hamilton’s baril (Opsarius bendelisis) and the trout barb (Raiamas bola), declined across both. Mid‐water fishes native to both lowlands and hills were most likely to experience range reduction. International Union for the Conservation of Nature Red List status was not representative of actual population trends, highlighting the critical role of local, long‐term data collection and management strategies for effective conservation. Opsarius bendelisis and R. bola urgently need protection in the KNR to stem current population declines. Conservation efforts here should focus on speciose lower‐elevation sites, where many of the 14 other significantly declining species also occur. Overfishing is likely to have contributed to species declines, suggesting that the network of terrestrial protected areas already in place across the HBH can aid aquatic biodiversity conservation efforts owing to their status as fish sanctuaries. Rivers such as the KNR represent a unique opportunity to conserve an intact, albeit threatened, fish species, before human pressures lead to widespread extirpations of the type documented in many areas of the world.

Threats assessment of vultures in Uttarakhand: A review note

Etymologically derived from Anglo-French vultur, Old French voutoir, voutre from Latin vultur, earlier voltur, and perhaps related to vellere- "to pluck, to tear"-the generic name ‘vulture’ does little justice to the immense ecological role that vultures play in maintaining the life support system of mother Earth. Given the wide range of topo-geographical features present in the State of Uttarakhand, all the 9 species of vultures of the Indian sub-continent are found here. However, the rapid and alarming decline in vulture population is a matter of great concern for all concerned. And therefore, there is an urgent need to identify the causes of decline and other threats that plague the vulture population in the country, especially in the State of Uttarakhand.

Tracking Device Attachment Methods for American Kestrels: Backpack Versus Leg-Loop Harnesses

ABSTRACT The American Kestrel (Falco sparverius) is a small falcon whose population is declining across North America, but drivers of this decline have yet to be identified. Conservationists have called for greater understanding of kestrels' migratory connectivity to identify potential causes of decline that may occur during various parts of their annual cycle. For many bird species, the most common and direct way to determine migratory connectivity is by attaching a tracking device that documents their locations over time. However, American Kestrels present a challenge when attaching tracking devices due to their small size and aggressive biting capabilities. We used two attachment methods (backpack and leg-loop harnesses) commonly used for raptors on a wintering population of American Kestrels in north Texas to test whether there were differences in observed return rates the following year. Of 20 American Kestrels fit with devices, significantly more of the kestrels fit with backpack harnesses were observed the following winter than the birds fit with leg-loop harnesses. Eight of the 10 kestrels we fit with backpacks were observed to return to their winter territories compared to only two of 10 kestrels fit with leg-loops. Overall return frequency data of kestrels with both harnessing methods (50%, n = 20) was similar to the frequency we observed on marked birds without devices (52%, n = 190), though this was heavily skewed due to the high return of birds with backpack harnesses (80%). Although our sample size was limited, the disparity between the return rates of birds with the two harness types suggests that backpack harnesses are the preferred method of attaching tracking devices to American Kestrels, and also potentially to similar small raptor species.

Dispersal of juvenile leatherback turtles from different Caribbean nesting beaches: A model study

The Northwest Atlantic (NWA) leatherback turtle (Dermochelys coriacea) subpopulation was recently classified as endangered. It nests in the Wider Caribbean Region and includes five genetic stocks, all declining, albeit at different rates. The causes of decline are multiple and difficult to identify based on annual nest counts which integrate the effects of multiple stressors over the entire life history. Demographic models, however, show that survival during the juvenile pelagic stage is the main factor modulating population trends, but this life stage remains largely unobserved. This paper presents a suite of numerical simulations where juveniles from the five NWA stocks disperse under the combined effects of ocean currents and habitat-driven swimming movements. Simulations reveal when and where NWA juveniles likely disperse and, thus, the environmental conditions and anthropogenic threats they may encounter. Simulated individuals initially disperse following either the “Caribbean route,” inside the Caribbean Sea and the Gulf of Mexico (GoM), or the “Atlantic route” east of the Antilles Islands Arc. The percentage of individuals following one or the other route varies markedly with the stock of origin. Late dispersal in the eastern Atlantic Ocean and the Mediterranean Sea is similar in all stocks. Juveniles following the Caribbean route are rapidly entrained northwards by the Gulf Stream and incur a high risk of cold-induced mortality. This mostly affects the Florida stock and the Western Caribbean (WCA) stock nesting in Costa Rica, Panama, and Colombia. The Atlantic route is less lethal as individuals progress more slowly toward higher latitudes. Simulations also show that the percentage of WCA juveniles visiting the GoM is larger than for any other stock. The learned migration goal (LMG) hypothesis, which posits that adult sea turtles tend to exploit foraging areas previously identified at the juvenile stage, may thus explain why WCA adults are overrepresented in the GoM. Finally, our results suggest that the recently observed increase in the percentage of WCA adults migrating into the GoM could be linked to bycatch reduction measures implemented in 2003–2004, combined with an increase in the frequency of Loop Current intrusion and eddy-shedding events that started around the year 2000.

Bisphenol A induced oxidative damage in the rat reproductive organs: A possible cause for decline in steroidogenesis

Bisphenol A induced oxidative damage in the rat reproductive organs: A possible cause for decline in steroidogenesis

It’s Time for a Turnaround on Turnaround Studies: Putting People and Process First

Unsatisfied with the low success rates of turnarounds, this paper investigates the literature on turnarounds from a process perspective. Using an input-throughput-output model we investigate the causes of decline, the different aspects of turnaround practices, their contextual factors, and the assessment of turnarounds. We conclude that all causes of decline are internal, stemming from dysfunctional leadership habits and human interactions, behaviors, and beliefs. Taking this seriously, turnaround studies should start integrating these organizational pathologies into their research objectives, to advance turnaround practices. We also find that similar turnaround measures under similar conditions show very different results, adding to the notion that content doesn’t matter when it comes to turnaround success, but process does. Still, the interplay between leadership style, the turnaround process, and staff engagement and their relationship to turnaround success is little investigated. We develop an agenda to fill this gap, integrating change management and systems psychodynamic concepts into turnaround studies to advance our understanding of decline and turnarounds and improve turnaround practices around the world.

Prevalence of gastrointestinal parasites in a lowland Black Grouse population in Central Europe

The Northern German Black Grouse metapopulation has been affected since decades by a sharply decline that has ultimately led to a reduced genetic variability. Gastrointestinal parasitoses are common among Black Grouse, but it is not clear if they have a further negative impact on the development of this already threatened metapopulation. Therefore, between 2011 and 2014, the occurrence and seasonal variation of gastrointestinal parasites were assessed by coproscopical investigations of Black Grouse feces collected in the nature conservation area of the “Lüneburg Heath”. Feces were obtained also from individuals during capture and re-capture activities. In total, 1,187 fecal samples were analyzed, of which 365 were caecal and 822 were rectal feces samples. 86% of the caecal and 95% of the rectal feces samples were parasite negative. Of the positive samples, oocysts of Coccidia spp. showed the highest prevalences of 12.1% in caecal and 1.1% in rectal samples, respectively. Helminths of the species/genera Trichostrongylus tenuis, Ascaridia spp., Heterakis spp., Capillaria spp., and Syngamus trachea were also observed, but at remarkably lower prevalences. High and moderate excretion intensities were observed only for coccidian oocysts. Coccidian infections revealed a seasonal pattern, occurring mostly during autumn and winter. Nematode eggs occurred more frequently in spring and summer. Four of the seven Black Grouse that were caught and equipped with GPS transmitters, presented high excretion intensities of coccidian oocysts. Despite high/moderate oocyst excretion, no negative health impact was observed, suggesting low pathogenicity of the infecting coccidia species or subsided infections. In contrast to previous studies, this Black Grouse population showed low prevalences of a rather narrow spectrum of parasites. We did not observe any negative impact of parasite infections on this population, which could be responsible for its decline. Thus, causes of decline are to be ascribed to other proximate and ultimate factors.

Re-evaluation Survey of Fish Composition, Abundance and Distribution in Agbokim Waterfalls, Nigeria

Alterations in the diversity of the ichthyofauna of a tropical waterfalls system can be affected by unsustainable utilisation of the fisheries resources, anthropogenic activities, runoff from faulty agricultural practices and environmental perturbation. To re-establish the status of the fish composition and diversity of Agbokim Waterfalls, monthly fish samples obtained from the fishery and physico-chemical properties were investigated in rainy and dry seasons, for six months along the length of the three reaches of the waterfalls. The results revealed a total of 833 fish specimens representing 18 species belonging to 15 genera from 9 families which is in deficit of four fish species, in the previous study which are Alestes nurse (Characidae), Aphyosemion gardneri (Cyprinodontidae), Pelmatochromis guntheri and Hemichromis fasciatus (Cichlidae). Cichlidae, Clariidae and Bagridae were the most abundant families accounting for 54.4% of the total catch with Cichlidae (23.17%) as the most dominant family and Mockokidae (1.68%) as the least with Tilapia zillii (15.4%), Clarias gariepinus (10.9% ) and Chrysichthys nigrodigitatus (9.5%) as the most dominant species accounting for 35.8% and Synodontis clarias (1.7%) with the least abundance. Fish species distribution in the downstream reach was dominant with 15 taxa and 607 (72.9%) individuals and in the midstream reach with 11 taxa but least (12.6%) number of individuals. Shannon Wiener diversity index for the six months was 2.7101 with Evenness value of 0.9376. The Richness index of Margalef’s was 2.5279 and Menhinick’s 0.6237. Seasonal variations in physico-chemical properties showed that, dissolved oxygen and conductivity were significantly (P< 0.05) higher in the raining season while pH showed no significant difference (P > 0.05). Temperature was significantly higher (p < 0.05) in the dry season than in the raining season. The hydrological properties showed a significantly higher mean values of rainfall (364.67± 0.00 mm) in the rainy and transparency (45.55± 1.58) in the dry season at (P < 0.05). In order to determine the cause of decline in fish species composition and abundance, further research on the heavy metals profile of the waterfalls is suggested.

Low Temperature Stress Tolerance: An Insight Into the Omics Approaches for Legume Crops.

The change in climatic conditions is the major cause for decline in crop production worldwide. Decreasing crop productivity will further lead to increase in global hunger rate. Climate change results in environmental stress which has negative impact on plant-like deficiencies in growth, crop yield, permanent damage, or death if the plant remains in the stress conditions for prolonged period. Cold stress is one of the main abiotic stresses which have already affected the global crop production. Cold stress adversely affects the plants leading to necrosis, chlorosis, and growth retardation. Various physiological, biochemical, and molecular responses under cold stress have revealed that the cold resistance is more complex than perceived which involves multiple pathways. Like other crops, legumes are also affected by cold stress and therefore, an effective technique to mitigate cold-mediated damage is critical for long-term legume production. Earlier, crop improvement for any stress was challenging for scientific community as conventional breeding approaches like inter-specific or inter-generic hybridization had limited success in crop improvement. The availability of genome sequence, transcriptome, and proteome data provides in-depth sight into different complex mechanisms under cold stress. Identification of QTLs, genes, and proteins responsible for cold stress tolerance will help in improving or developing stress-tolerant legume crop. Cold stress can alter gene expression which further leads to increases in stress protecting metabolites to cope up the plant against the temperature fluctuations. Moreover, genetic engineering can help in development of new cold stress-tolerant varieties of legume crop. This paper provides a general insight into the “omics” approaches for cold stress in legume crops.

Genetic polymorphism in the mitochondrial D-loop of Oriental White-backed Vultures (Gyps bengalensis)

Abstract Vultures are among nature’s most successful scavengers, providing tractable models for ecological, economic, and cultural studies. Asian vultures have undergone dramatic declines of 90–99% in the subcontinent due to consequences of poisoning drugs, thereby being at a high risk of extinction. In Pakistan, surveys conducted previously focused mostly the cause of decline and breeding strategies only. Genetic profiling of vultures was still unmapped that could play a particular role in conservation endeavors and let researchers to genetically label individuals of threatened or endangered species. In this study, we examined genetic diversity and molecular phylogeny of Oriental White-backed Vultures by analyzing mitochondrial DNA (mtDNA) sequences. Genetic polymorphism was detected among individuals, and, on that basis, phylogenetic analysis was conducted through Bayesian analysis of DNA sequences using MCMC. Using multiple sequence alignment, two mutations, transversion T>G and transition G>A, were observed at nucleotide positions 1 and 2, respectively. Similarly, T/C heterozygosity at two positions, 53 and 110, and one heterozygous T/G locus at 130 position were also observed. The reference sequence, along with other samples of V1, V6, V7 and V9, was placed into a clade, while V2, V5, V11, V3, V4 and V10 samples were grouped into a two clade.

Feral cats use fine scale prey cues and microhabitat patches of dense vegetation when hunting prey in arid Australia

Introduced predators are one of the leading causes of decline in island vertebrates. Understanding how they hunt and kill threatened prey can help improve management activities. Although broadscale features are known to influence predator movement patterns, factors influencing fine scale movement are often overlooked. In particular, the influence of prey cues and microhabitat features has received little attention despite predators spending considerable time hunting prey using a range of visual, olfactory and auditory cues. Using feral cats as a case study, we utilised video and GPS collars combined with ground-truthing to determine if predators use fine-scale prey cues or microhabitat features to hunt in an arid environment. Feral cat activity was comprised of continuous traverses interspersed with periods of stationary activity (GPS clusters) generally less than 40 min in duration. Video collars confirmed that these clusters included the majority of stalk and pounce hunting bouts. Stationary activity was significantly focussed on prominent prey cues such as burrows, foraging digs or warrens of mammalian prey including both exotic (rabbits) and threatened native species (rodents, bilbies and bettongs). Evidence of prey kills was higher at cluster sites. Cats spent significantly more time at microsites with high vegetation cover including single shrubs and trees, suggesting that they use prominent prey cues and patches of thick cover to increase their probability of encountering prey and/or to conceal themselves during hunting or feeding activity. Results suggest prey species with conspicuous cues are at higher risk of predation and this vulnerability could increase over time as resident cats learn to identify the location of prey cues within their home range. Conversely, removing resident knowledgeable predators may reduce predation rates if immigrating predators take time to learn to locate prey cues in their new environment. We urge researchers to investigate fine-scale drivers of movement patterns as this information is likely to be critical for long term management of predator species.

The Damage Mechanisms of Dark Hypoxic Stress on Photosystem II of Cymodocea rotundata.

Hypoxic stress is a major threat to the survival of seagrass but its damage mechanism is unclear. In order to explore the causes of seagrass meadow decline due to hypoxia, the effects of hypoxia in the dark on photosystem II (PSII) of Cymodocea rotundata, a widely distributed seagrass in Indo-Pacific area, were investigated in this study. The results show that dark hypoxic stress resulted in the inactivation of PSII reaction center, as well as the damage of PSII donor and acceptor sides in C. rotundata. These damages to PSII were not related to leaf senescence, but to the reactive oxygen species (ROS) accumulation. The lower the seawater oxygen content and the longer the hypoxic duration, the harder the recovery of PSII activity under dark normoxia because of dark hypoxia caused D1 protein injury. The interference of hypoxia on the AOX respiratory pathway is an important cause of the PSII damage under dark hypoxic stress. The PSII damage would result in a significant decrease in the photosynthetic activity, thereby affecting the growth and development of C. rotundata. Based on the above results, it is suggested that dark hypoxia may be an important cause of decline of C. rotundata meadow.

Holm oak decline is determined by shifts in fine root phenotypic plasticity in response to belowground stress.

Summary Climate change and pathogen outbreaks are the two major causes of decline in Mediterranean holm oak trees (Quercus ilex L. subsp. ballota (Desf.) Samp.). Crown‐level changes in response to these stressful conditions have been widely documented but the responses of the root systems remain unexplored. The effects of environmental stress over roots and its potential role during the declining process need to be evaluated.We aimed to study how key morphological and architectural root parameters and nonstructural carbohydrates of roots are affected along a holm oak health gradient (i.e. within healthy, susceptible and declining trees).Holm oaks with different health statuses had different soil resource‐uptake strategies. While healthy and susceptible trees showed a conservative resource‐uptake strategy independently of soil nutrient availability, declining trees optimized soil resource acquisition by increasing the phenotypic plasticity of their fine root system.This increase in fine root phenotypic plasticity in declining holm oaks represents an energy‐consuming strategy promoted to cope with the stress and at the expense of foliage maintenance. Our study describes a potential feedback loop resulting from strong unprecedented belowground stress that ultimately may lead to poor adaptation and tree death in the Spanish dehesa.