Root trait variation along water gradients in the Cape Floristic Region

Questions

Roots are responsible for essential plant functions including water uptake. However, the extent to which root traits (size and structure) determine plant presence in water-limited environments is still poorly understood. Here we investigated how root traits vary across water availability gradients within a dry South African biome.

Location

South Africa.

Methods

We measured six below-ground (root) and eight above-ground (leaf + stem) traits of 124 individuals of nine dominant woody shrub species from wetter and drier sites (600–700 vs 250–300 mm annual precipitation) in the Fynbos biome of the Cape Floristic Region. Within sites, we sampled from recently burnt and unburnt/more mature vegetation and at three locations along topographical gradients.

Results

Drier regions showed greater maximum rooting depth, length, root dry matter content and root to shoot ratio. These trait patterns were consistent at an intraspecific level, along locally drier topographical locations and in post-fire environments. Roots accounted for significant whole-plant trait variation. Additionally, in drier conditions, we found increased root allocation deviating from expected global allometric relationships. Our study also demonstrates that the combination of fire and drought in the driest locations results in poor above-ground vegetation recovery in terms of plant size, cover and individual counts with only resprouters persisting.

Conclusions

Our research suggests that root investment in Fynbos shrubs will likely be key for coping with a drier and warmer future and should be a focus of more research for dryland biomes.     

Intraspecific trait variation and reversals of trait strategies across key climate gradients in native Hawaiian plants and non-native invaders

Background and AimsDisplacement of native plant species by non-native invaders may result from differences in their carbon economy, yet little is known regarding how variation in leaf traits influences native–invader dynamics across climate gradients. In Hawaii, one of the most heavily invaded biodiversity hotspots in the world, strong spatial variation in climate results from the complex topography, which underlies variation in traits that probably drives shifts in species interactions.MethodsUsing one of the most comprehensive trait data sets for Hawaii to date (91 species and four islands), we determined the extent and sources of variation (climate, species and species origin) in leaf traits, and used mixed models to examine differences between natives and non-native invasives.Key ResultsWe detected significant differences in trait means, such that invasives were more resource acquisitive than natives over most of the climate gradients. However, we also detected trait convergence and a rank reversal (natives more resource acquisitive than invasives) in a sub-set of conditions. There was significant intraspecific trait variation (ITV) in leaf traits of natives and invasives, although invasives expressed significantly greater ITV than natives in water loss and photosynthesis. Species accounted for more trait variation than did climate for invasives, while the reverse was true for natives. Incorporating this climate-driven trait variation significantly improved the fit of models that compared natives and invasives. Lastly, in invasives, ITV was most strongly explained by spatial heterogeneity in moisture, whereas solar energy explains more ITV in natives.ConclusionsOur results indicate that trait expression and ITV vary significantly between natives and invasives, and that this is mediated by climate. These findings suggest that although natives and invasives are functionally similar at the regional scale, invader success at local scales is contingent on climate.     

Potential effects of future climate change on global reptile distributions and diversity

Aim

Until recently, complete information on global reptile distributions has not been widely available. Here, we provide the first comprehensive climate impact assessment for reptiles on a global scale.

Location

Global, excluding Antarctica.

Time period

1995, 2050 and 2080.

Major taxa studied

Reptiles.

Methods

We modelled the distribution of 6296 reptile species and assessed potential global and realm-specific changes in species richness, the change in global species richness across climate space, and species-specific changes in range extent, overlap and position under future climate change. To assess the future climatic impact on 3768 range-restricted species, which could not be modelled, we compared the future change in climatic conditions between both modelled and non-modelled species.

Results

Reptile richness was projected to decline significantly over time, globally but also for most zoogeographical realms, with the greatest decreases in Brazil, Australia and South Africa. Species richness was highest in warm and moist regions, with these regions being projected to shift further towards climate extremes in the future. Range extents were projected to decline considerably in the future, with a low overlap between current and future ranges. Shifts in range centroids differed among realms and taxa, with a dominant global poleward shift. Non-modelled species were significantly stronger affected by projected climatic changes than modelled species.

Main conclusions

With ongoing future climate change, reptile richness is likely to decrease significantly across most parts of the world. This effect, in addition to considerable impacts on species range extent, overlap and position, was visible across lizards, snakes and turtles alike. Together with other anthropogenic impacts, such as habitat loss and harvesting of species, this is a cause for concern. Given the historical lack of global reptile distributions, this calls for a re-assessment of global reptile conservation efforts, with a specific focus on anticipated future climate change.     

The effects of grazing history,soil properties and stand structure on the communities of saprotrophic fungi in wood-pastures

Wood-pastures are threatened anthropogenic biotopes that provide habitat for an extensive group of species. Here we studied the effect of management, grazing intensity, time since abandonment, historical land-use intensity, soil properties and stand conditions on communities of saprotrophic fungi in wood-pastures in Central Finland. We found that the proportion of broadleaved trees and soil pH are the major drivers in the communities of saprotrophic fungi in these boreal wood-pastures. In addition, tree species richness, soil moisture, historical land-use intensity and time since abandonment affected the communities of saprotrophic fungi. Current management or grazing intensity did not have a clear effect on saprotrophic fungal species richness, although dung-inhabiting fungal species richness was highest at intermediate to high grazing intensity. Obviously, there were many more dung-inhabiting fungal species on grazed than on abandoned sites. Our study highlights the conservation value of wood-pastures as hotspots of saprotrophic fungi.     

Mixed effects of climate variation on the scots pine forests: Age and species mixture matter

Understanding and unravelling the direct and indirect effects of ongoing and predicted climate change on the vitality and productivity of Scots pine forests is particularly important for Romania and other parts of eastern Europe, where the species represents an essential ecological and economic value. Here, we introduce the first nation-wide network of 34 Scots pine chronologies of basal area increment (BAI), and assess the species’ vulnerability to climate change. Temperatures of the previous autumn, as well as current year spring and summer warmth are found to be most critical for the productivity of Romania’s Scots pine forests. Negative growth anomalies after hot and dry August conditions are most severe in young (<50 years) Scots pine monocultures (>70% dominance) at lower elevations (<1000 m a.s.l.) across western Romania. Our findings emphasise the relevance and timeliness of carefully adapting sylvicultural management strategies to enhance the ecological and economic resilience of Romania’s widespread forest areas under a warmer and drier future climate.     

Insight into AMPK regulation mechanism in vivo and in vitro: Responses to low temperatures in the olive flounder Paralichthys olivaceus

The olive flounder, Paralichthys olivaceus, is a commercially important maricultured fish in China, Japan, and Korea. Low winter temperatures influence its survival and growth and affect the output of the aquaculture industry. Energy metabolism is essential for fish survival, and the central energy-regulating factor – 5ʹ-AMP-activated protein kinase (AMPK) – plays an important role in responses to cold stress. However, the mechanism of AMPK pathway regulation in fish coping with cold stress remains poorly understood. In the present study, the expression of AMPK and its upstream (LKB1 and CaMKKβ) and downstream genes (SITR1, FOXO1A, and TFAM) in the brain, muscle, and heart was analyzed while the flounder was under cold stress (0.2 ± 0.2 °C). The results showed that low temperatures activated LKB1, CaMKKβ, and AMPK genes in the brain, and the activated AMPK induced expression of SITR1, FOXO1A, and TFAM. In the muscle tissue, the expression patterns of these genes presented a trend of initially decreasing and then increasing, and there was a delay in the response to low temperatures. At the cellular level, comparative analysis of the effects of the activator 5-aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR) and inhibitor compound C of the AMPK pathway demonstrated that cold stress was similar to AICAR, which activated the AMPK pathway with hysteresis. Thus, the regulation mechanism of AMPK under cold stress was preliminarily analyzed. In general, AMPK was involved not only in responses to low temperatures but also in energy regulation under cold stress.     

Predicting species responses to climate change: demography and climate microrefugia in California valley oak (Quercus lobata)

Anticipating species movement under climate change is a major focus in conservation. Bioclimate models are one of the few predictive tools for adaptation planning, but are limited in accounting for (i) climatic tolerances in preadult life stages that are potentially more vulnerable to warming; and (ii) local‐scale movement and use of climatic refugia as an alternative or complement to large‐scale changes in distribution. To assess whether these shortfalls can be addressed with field demographic data, we used California valley oak (Quercus lobata Nee), a long‐lived species with juvenile life stages known to be sensitive to climate. We hypothesized that the valley oak bioclimate model, based on adults, would overpredict the species' ability to remain in the projected persisting area, due to higher climate vulnerability of young life stages; and underpredict the potential for the species to remain in the projected contracting area in local‐scale refugia. We assessed the bioclimate model projections against actual demographic patterns in natural populations. We found that saplings were more constricted around surface water than adults in the projected contracting area. We also found that the climate envelope for saplings is narrower than that for adults. Saplings disappeared at a summer maximum temperature 3 °C below that associated with adults. Our findings indicate that rather than a complete shift northward and upward, as predicted by the species bioclimate model, valley oaks are more likely to experience constriction around water bodies, and eventual disappearance from areas exceeding a threshold of maximum temperature. Ours is the first study we know of to examine the importance of discrete life stage climate sensitivities in determining bioclimate modeling inputs, and to identify current climate change‐related constriction of a species around microrefugia. Our findings illustrate that targeted biological fieldwork can be central to understanding climate change‐related movement for long‐lived, sessile species.     

Use and misuse of the IUCN Red List Criteria in projecting climate change impacts on biodiversity

Recent attempts at projecting climate change impacts on biodiversity have used the IUCN Red List Criteria to obtain estimates of extinction rates based on projected range shifts. In these studies, the Criteria are often misapplied, potentially introducing substantial bias and uncertainty. These misapplications include arbitrary changes to temporal and spatial scales; confusion of the spatial variables; and assume a linear relationship between abundance and range area. Using the IUCN Red List Criteria to identify which species are threatened by climate change presents special problems and uncertainties, especially for shorter‐lived species. Responses of most species to future climate change are not understood well enough to estimate extinction risks based solely on climate change scenarios and projections of shifts and/or reductions in range areas. One way to further such understanding would be to analyze the interactions among habitat shifts, landscape structure and demography for a number of species, using a combination of models. Evaluating the patterns in the results might allow the development of guidelines for assigning species to threat categories, based on a combination of life history parameters, characteristics of the landscapes in which they live, and projected range changes.     

Predicting the impacts of climate change on the distribution of species: are bioclimate envelope models useful?

Modelling strategies for predicting the potential impacts of climate change on the natural distribution of species have often focused on the characterization of a species’ bioclimate envelope. A number of recent critiques have questioned the validity of this approach by pointing to the many factors other than climate that play an important part in determining species distributions and the dynamics of distribution changes. Such factors include biotic interactions, evolutionary change and dispersal ability. This paper reviews and evaluates criticisms of bioclimate envelope models and discusses the implications of these criticisms for the different modelling strategies employed. It is proposed that, although the complexity of the natural system presents fundamental limits to predictive modelling, the bioclimate envelope approach can provide a useful first approximation as to the potentially dramatic impact of climate change on biodiversity. However, it is stressed that the spatial scale at which these models are applied is of fundamental importance, and that model results should not be interpreted without due consideration of the limitations involved. A hierarchical modelling framework is proposed through which some of these limitations can be addressed within a broader, scale‐dependent context.     

Mechanistic insights into the effects of climate change on larval cod

Understanding the biophysical mechanisms that shape variability in fisheries recruitment is critical for estimating the effects of climate change on fisheries. In this study, we used an Earth System Model (ESM) and a mechanistic individual‐based model (IBM) for larval fish to analyze how climate change may impact the growth and survival of larval cod in the North Atlantic. We focused our analysis on five regions that span the current geographical range of cod and are known to contain important spawning populations. Under the SRES A2 (high emissions) scenario, the ESM‐projected surface ocean temperatures are expected to increase by >1 °C for 3 of the 5 regions, and stratification is expected to increase at all sites between 1950–1999 and 2050–2099. This enhanced stratification is projected to decrease large (>5 μm ESD) phytoplankton productivity and mesozooplankton biomass at all 5 sites. Higher temperatures are projected to increase larval metabolic costs, which combined with decreased food resources will reduce larval weight, increase the probability of larvae dying from starvation and increase larval exposure to visual and invertebrate predators at most sites. If current concentrations of piscivore and invertebrate predators are maintained, larval survival is projected to decrease at all five sites by 2050–2099. In contrast to past observed responses to climate variability in which warm anomalies led to better recruitment in cold‐water stocks, our simulations indicated that reduced prey availability under climate change may cause a reduction in larval survival despite higher temperatures in these regions. In the lower prey environment projected under climate change, higher metabolic costs due to higher temperatures outweigh the advantages of higher growth potential, leading to negative effects on northern cod stocks. Our results provide an important first large‐scale assessment of the impacts of climate change on larval cod in the North Atlantic.     

Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability

The Southern Ocean is a major component within the global ocean and climate system and potentially the location where the most rapid climate change is most likely to happen, particularly in the high-latitude polar regions. In these regions, even small temperature changes can potentially lead to major environmental perturbations. Climate change is likely to be regional and may be expressed in various ways, including alterations to climate and weather patterns across a variety of time-scales that include changes to the long interdecadal background signals such as the development of the El Niño–Southern Oscillation (ENSO). Oscillating climate signals such as ENSO potentially provide a unique opportunity to explore how biological communities respond to change. This approach is based on the premise that biological responses to shorter-term sub-decadal climate variability signals are potentially the best predictor of biological responses over longer time-scales. Around the Southern Ocean, marine predator populations show periodicity in breeding performance and productivity, with relationships with the environment driven by physical forcing from the ENSO region in the Pacific. Wherever examined, these relationships are congruent with mid-trophic-level processes that are also correlated with environmental variability. The short-term changes to ecosystem structure and function observed during ENSO events herald potential long-term changes that may ensue following regional climate change. For example, in the South Atlantic, failure of Antarctic krill recruitment will inevitably foreshadow recruitment failures in a range of higher trophic-level marine predators. Where predator species are not able to accommodate by switching to other prey species, population-level changes will follow. The Southern Ocean, though oceanographically interconnected, is not a single ecosystem and different areas are dominated by different food webs. Where species occupy different positions in different regional food webs, there is the potential to make predictions about future change scenarios.     

气候变化和人为活动在宁夏草地变化中的相对作用

气候变化和人为活动是草地生态系统退化或恢复过程中的两大驱动因素。选取植被净初级生产力（NPP）为衡量指标,利用改进的Carnegie-Ames-Stanford Approach （CASA）模型、Thornthwaite Memorial模型以及残差趋势法分别计算了宁夏草地实际净初级生产力（ANPP）、潜在净初级生产力（PNPP）和人为活动影响的生产力（HNPP）及其变化趋势,定量评估了2001-2019年气候变化和人为活动在宁夏4种类型草地（温性草甸、温性草原、温性荒漠草原和温性草原化荒漠）动态变化中的相对作用。结果表明,2001-2019年宁夏草地实际净初级生产力增加的面积占宁夏草地总面积的97.84%;全区草地潜在净初级生产力均表现为增加趋势,表明气候变化有利于植被恢复。草地恢复过程中,气候变化引起的草地恢复面积占草地恢复总面积的61.68%,气候变化和人为活动共同作用引起的草地恢复面积占38.32%;人为活动是导致草地退化的绝对主导因素。4种类型草地动态变化的驱动因素存在差异,气候变化是促进温性草甸（68.94%）和温性草原化荒漠（70.51%）恢复的主导因素,气候变化和人为活动共同作用是促进温性草原恢复的主导因素（62.30%）,温性荒漠草原的恢复是气候变化和人为活动共同作用的结果（97.93%）。水热条件好转,尤其是降水增加是宁夏草地恢复的主导气候因子,生态保护政策的实施是促进草地恢复的主要人为因素,对草地的不合理利用是导致草地退化的主要人为因素。     

Modelling potential impacts of climate change on the bioclimatic envelope of species in Britain and Ireland

Aim Climate change has the potential to have significant impacts on the distribution of species and on the composition of habitats. This paper identifies the potential changes in the future distribution of species under the UKCIP98 climate change scenarios, in order that such changes can be taken into account in conservation management. Location The model was applied to Britain and Ireland. Methods A model based on an artificial neural network was used to predict the changing bioclimate envelopes of species in Britain and Ireland. Fifty‐four species representing 15 habitats were modelled. Results The modelled species could be placed into three categories: those losing suitable climate space, those gaining it, and those showing little or no change. When the species were associated with habitats it was found that Arctic–Alpine/montane heath communities were the most sensitive to climate change, followed by pine woodland and beech woodland in southern England. In lowland heath, wet heath, cereal field margins, coastal grazing marsh, drought‐prone acid grassland and calcareous grassland, the species either showed little change or an increase in suitable climate space. The other eight habitats showed a mixed response. Conclusions The species show a variety of responses to climate change and thus their current habitat associations may alter. The uncertain future of some species and habitats is highlighted. Conservation policy and practice will need to be revised in the face of climate change.     

Geographic variation in growth and phenology of two dominant central US grasses: consequences for climate change

Aims The rate of climate change may exceed many plant species' migration rates, particularly for long-lived perennial species that dominate most ecosystems. If bioclimatic envelopes shift more rapidly than dominant species can migrate, individuals located peripheral to biomes or in adjacent biomes may become a significant source of traits for future dominant populations (DPs). Thus, traits of individuals from peripheral populations (PPs) may affect future ecosystem functioning more than those of today's DPs.Methods We assessed key traits of individuals collected from populations that currently dominate two central US grasslands, the shortgrass steppe (Bouteloua gracilis) and the tallgrass prairie (Andropogon gerardii). We compared these to individuals from PPs in a reciprocal-transplant common garden experiment with gardens at the Shortgrass Steppe Long Term Ecological Research site in Colorado and the Konza Prairie Biological Station Long Term Ecological Research site in Kansas. DPs and PPs were subjected to high and reduced water availability in common gardens located in each biome. Traits measured included the following: individual plant biomass, reproductive allocation, specific leaf area (SLA) and plant–water relations. We focused on the climate-change relevant comparisons of traits from PPs versus DPs expressed under the climate of DPs.Important findings PPs of B. gracilis differed from DPs primarily in phenological traits. Under a semiarid shortgrass steppe climate, PPs initiated flowering later in the season, produced fewer reproductive tillers and were more sensitive to water stress. Biomass differences between populations were minimal. For A. gerardii, biomass in PPs was 50% lower than in DPs under the mesic tallgrass prairie climate and reproductive tillers were considerably smaller, despite higher SLA in PPs. Biomass of PPs was less sensitive to water stress, however. From these results, we conclude that key traits of PPs differed from DPs in both grassland types, but potential effects on reproductive phenology were greater for the bioclimatic shift in which a mesic biome becomes arid, whereas aboveground productivity may be affected more when a semiarid biome becomes more mesic.     

Projected marine climate change: effects on copepod oxidative status and reproduction

Zooplankton are an important link between primary producers and fish. Therefore, it is crucial to address their responses when predicting effects of climate change on pelagic ecosystems. For realistic community‐level predictions, several biotic and abiotic climate‐related variables should be examined in combination. We studied the combined effects of ocean acidification and global warming predicted for year 2100 with toxic cyanobacteria on the calanoid copepod, Acartia bifilosa. Acidification together with higher temperature reduced copepod antioxidant capacity. Higher temperature also decreased egg viability, nauplii development, and oxidative status. Exposure to cyanobacteria and its toxin had a negative effect on egg production but, a positive effect on oxidative status and egg viability, giving no net effects on viable egg production. Additionally, nauplii development was enhanced by the presence of cyanobacteria, which partially alleviated the otherwise negative effects of increased temperature and decreased pH on the copepod recruitment. The interactive effects of temperature, acidification, and cyanobacteria on copepods highlight the importance of testing combined effects of climate‐related factors when predicting biological responses.