Diversity in habit expands the environmental niche of Ziziphus (Rhamnaceae)

This is the final version. Available on open access from Wiley via the DOI in this recordData availability statement: The data that support the findings of this study are openly available in the Dryad Digital Repository: https://doi.org/10.5061/dryad.34tmpg4p0 (Rickenback et al., 2022).Ziziphus (Rhamnaceae) is a widely distributed genus across the Australasian and African tropics with unusual diversity in habit, and many species of significance to people. Here, we quantify the environmental limits of Ziziphus species and examine inter-specific relationships among functional traits, environment, biome, and range size. We developed a curated geolocation database for Ziziphus and used it to examine the environmental limits of the genus relative to temperature, rainfall, and seasonality. To assess the relationship between biome and habit, permutational analysis of variance was used, while hierarchical clustering was used to determine whether habit, leaves, and fruit traits were related to biome. For 40 species with adequate geolocation data, range size was calculated to assess its relationship with habit, biomes, and cultivation. Finally, niche identity tests were used to determine niche equivalency among cultivated and non-cultivated species. Liana species are restricted to closed forests and the geoxylic habit is found only in open grasslands. Further, habit is significantly associated with range size, with trees having on average larger range sizes than shrubs, lianas, and geoxyles, but biome was not correlated with range size. Cultivated species have ranges ~10 times that of non-cultivated tree species and with significantly different and broader environmental niches. The unusually wide distribution of Ziziphus can be explained by its diversity of habits associated with different biomes spanning continents. This, along with the usage of many Ziziphus species by people for their fruits, expands the range and environmental occupation of the genus

Encroachment diminishes herbaceous plant diversity in grassy ecosystems worldwide

Woody encroachment is ubiquitous in grassy ecosystems worldwide, but its global impacts on the diversity of herbaceous plants that characterise and define these ecosystems remain unquantified. The pervasiveness of encroachment is relatively easily observed via remote sensing, but its impacts on plant diversity and richness below the canopy can only be observed via field‐based studies. Via a meta‐analysis of 42 field studies across tropical to temperate grassy ecosystems, we quantified how encroachment altered herbaceous species richness, and the richness of forbs, C(3) graminoids and C(4) graminoids. Across studies, the natural logarithm of the response ratio (lnRR) of herbaceous species richness ranged from −3.33 to 0.34 with 87% of encroached ecosystems negatively impacted. Assessment of the extent of encroachment, duration of encroachment, mean annual rainfall, latitude, and continent demonstrated that only extent of encroachment had relevance in the data (univariate model including a random effect of study explained 45.4% of variance). The global weighted mean lnRR of species richness decreased from −0.245 at 66%. Continued encroachment results in substantial loss of herbaceous diversity at medium and high extents, with a loss of richness that is not replaced. Although all functional groups are significantly negatively impacted by encroachment, forb richness is relatively more sensitive than graminoid richness, and C(4) graminoid richness relatively more than C(3) graminoid richness. Although no geographic or climatic correlates had relevance in the data, encroachment as an emergent product of global change coalesces to decrease ground layer light availability, lead to loss of fire and grazers, and alter hydrology and soils. Encroachment is accelerating and grassy ecosystems require urgent attention to determine critical woody cover thresholds that facilitate diverse and resilient grassy ecosystems

Interaction and Experience in Enactive Intelligence and Humanoid Robotics

We overview how sensorimotor experience can be operationalized for interaction scenarios in which humanoid robots acquire skills and linguistic behaviours via enacting a “form-of-life”’ in interaction games (following Wittgenstein) with humans. The enactive paradigm is introduced which provides a powerful framework for the construction of complex adaptive systems, based on interaction, habit, and experience. Enactive cognitive architectures (following insights of Varela, Thompson and Rosch) that we have developed support social learning and robot ontogeny by harnessing information-theoretic methods and raw uninterpreted sensorimotor experience to scaffold the acquisition of behaviours. The success criterion here is validation by the robot engaging in ongoing human-robot interaction with naive participants who, over the course of iterated interactions, shape the robot’s behavioural and linguistic development. Engagement in such interaction exhibiting aspects of purposeful, habitual recurring structure evidences the developed capability of the humanoid to enact language and interaction games as a successful participant

Accurate quantification of selenoproteins in human plasma/serum by isotope dilution ICP-MS : focus on selenoprotein P

Acknowledgements The research leading to these results was funded by the EMRP Joint Research Project “Metrology for metalloproteins” (HLT-05 2012). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union.Peer reviewedPostprin

Woody plant encroachment intensifies under climate change across tundra and savanna biomes

CITATION: Garcia Criado, M. et al. 2020. Woody plant encroachment intensifies under climate change across tundra and savanna biomes. Global Ecology and Biogeography, 229(5): 925–943. doi:10.1111/geb.13072The original publication is available at https://onlinelibrary.wiley.com/journal/14668238Aim: Biomes worldwide are shifting with global change. Biomes whose extents are limited by temperature or precipitation, such as the tundra and savanna, may be particularly strongly affected by climate change. While woody plant encroachment is prevalent across both biomes, its relationship to temperature and precipitation change remains unknown. Here, we quantify the degree to which woody encroachment is related to climate change and identify its main associated drivers. Location: Tundra and savanna biomes. Time period: 1992 ± 20.27–2010 ± 5.62 (mean ± SD). 1876–2016 (range). Major taxa studied: Woody plants (shrubs and trees). Methods: We compiled a dataset comprising 1,089 records from 899 sites of woody plant cover over time and attributed drivers of woody cover change across these two biomes. We calculated cover change in each biome and assessed the degree to which cover change corresponds to concurrent temperature and precipitation changes using multiple climate metrics. Finally, we conducted a quantitative literature review of the relative importance of attributed drivers of woody cover change. Results: Woody encroachment was widespread geographically and across climate gradients. Rates of woody cover change (positive or negative) were 1.8 times lower in the tundra than in the savanna (1.8 vs. 3.2%), while rates of woody cover increase (i.e., encroachment) were c. 1.7 times lower in the tundra compared with the savanna (3.7 vs. 6.3% per decade). In the tundra, magnitudes of woody cover change did not correspond to climate, while in the savanna, greater cover change corresponded with increases in precipitation. We found higher rates of woody cover change in wetter versus drier sites with warming in the tundra biome, and higher rates of woody cover change in drier versus wetter sites with increasing precipitation in the savanna. However, faster rates of woody cover change were not associated with more rapid rates of climate change across sites, except for maximum precipitation in the savanna. Main conclusions: Woody encroachment was positively related to warming in the tundra and increased rainfall in the savanna. However, cover change rates were not predicted by rates of climate change, which can be partially explained by climate interactions in both biomes. Additional likely influences include site-level factors, time-lags, plant-specific responses, and land use and other non-climate drivers. Our findings highlight the complex nature of climate change impacts in biomes limited by seasonality, which should be accounted for to realistically estimate future responses across open biomes under global change scenarios.https://onlinelibrary.wiley.com/doi/10.1111/geb.13072Publishers versio

Focus on changing fire regimes: interactions with climate, ecosystems, and society

Fire is a complex Earth system phenomenon that fundamentally affects vegetation distributions, biogeochemical cycling, climate, and human society across most of Earth’s land surface. Fire regimes are currently changing due to multiple interacting global change drivers, most notably climate change, land use, and direct human influences via ignition and suppression. It is therefore critical to better understand the drivers, patterns, and impacts of these changing fire regimes now and continuing into the future. Our review contributes to this focus issue by synthesizing results from 27 studies covering a broad range of topics. Studies are categorized into (i) Understanding contemporary fire patterns, drivers, and effects; (ii) Human influences on fire regimes; (iii) Changes in historical fire regimes; (iv) Future projections; (v) Novel techniques; and (vi) Reviews. We conclude with a discussion on progress made, major remaining research challenges, and recommended directions

Fire and grazing determined grasslands of central Madagascar represent ancient assemblages

The ecology of Madagascar's grasslands is under-investigated and the dearth of ecological understanding of how disturbance by fire and grazing shapes these grasslands stems from a perception that disturbance shaped Malagasy grasslands only after human arrival. However, worldwide, fire and grazing shape tropical grasslands over ecological and evolutionary timescales, and it is curious Madagascar should be a global anomaly. We examined the functional and community ecology of Madagascar's grasslands across 71 communities in the Central Highlands. Combining multivariate abundance models of community composition and clustering of grass functional traits, we identified distinct grass assemblages each shaped by fire or grazing. The fire-maintained assemblage is primarily composed of tall caespitose species with narrow leaves and low bulk density. By contrast, the grazer-maintained assemblage is characterized by mat-forming, high bulk density grasses with wide leaves. Within each assemblage, levels of endemism, diversity and grass ages support these as ancient assemblages. Grazer-dependent grasses can only have co-evolved with a now-extinct megafauna. Ironically, the human introduction of cattle probably introduced a megafaunal substitute facilitating modern day persistence of a grazer-maintained grass assemblage in an otherwise defaunated landscape, where these landscapes now support the livelihoods of millions of people

Piezoelectric response to coherent longitudinal and transverse acoustic phonons in a semiconductor Schottky diode

We study the generation of microwave electronic signals by pumping a (311) GaAs Schottky diode with compressive and shear acoustic phonons, generated by femtosecond optical excitation of an Al _lm transducer and mode conversion at the Al-GaAs interface. They propagate through the substrate and arrive at the Schottky device on the opposite surface, where they induce a microwave electronic signal. The arrival time, amplitude and polarity of the signals depend on the phonon mode. A theoretical analysis is made of the polarity of the experimental signals. This includes the piezoelectric and deformation potential mechanisms of electron-phonon interaction in a Schottky contact and shows that the piezoelectric mechanism is dominant for both transverse and longitudinal modes with frequencies below 250 GHz and 70 GHz respectively