Increased climate variability is expected to intensify short-term drought events. Plants have evolved stress tolerance strategies involving trade-offs in resource conservation, mycorrhizal collaboration and plant size, yet how these strategies promote drought resistance across different herbaceous plant groups remains unknown. Leveraging 63 globally distributed grassland and shrubland sites from the International Drought Experiment, we identified plant traits linked to drought resistance in 661 populations of 421 species after 1 year of extreme drought. We assessed how traits, site precipitation and drought severity affected cover change across growth forms and lifespans, and how trait-environment interactions influenced drought resistance. Across all species, leaf N (an acquisitive trait) was associated with drought resistance, whereas in forbs, drought resistance was also associated with a conservative root trait and plant size. In addition, interactions among traits mediated drought resistance; root traits predicted performance only in concert with other traits. Environmental variables influenced trait effects on drought resistance, notably for annuals in wetter sites, suggesting that drought-escape strategies in annuals may be advantageous only under mild stress. Our study highlights variability in traits that predict drought resistance across herbaceous plant groups, emphasizing the importance of species context, environmental stress and the selection of traits in research and management.

As droughts become longer and more intense, impacts on terrestrial primary productivity are expected to increase progressively. Yet, some ecosystems appear to acclimate to multiyear drought, with constant or diminishing reductions in productivity as drought duration increases. We quantified the combined effects of drought duration and intensity on aboveground productivity in 74 grasslands and shrublands distributed globally. Ecosystem acclimation with multiyear drought was observed overall, except when droughts were extreme (i.e., ≤1-in-100-year likelihood of occurrence). Productivity losses after four consecutive years of extreme drought increased by ~2.5-fold compared with those of the first year. These results portend a foundational shift in ecosystem behavior if drought duration and intensity increase, from maintenance of reduced functioning over time to progressive and profound losses of productivity when droughts are extreme.

PREMISE:Environmental DNA (eDNA) can be used to determine the composition of the soil biome community, revealing beneficial and antagonistic microbes and invertebrates associated with plants. eDNA analyses can complement traditional soil community studies, offering more comprehensive information for conservation practitioners. Studies are also needed to examine differences between field and greenhouse soil biomes because greenhouse-grown plants are often transplanted in the field during restoration efforts. METHODS:We used eDNA multilocus metabarcoding to test how the soil biome of the federally and state-endangered species, Lupinus nipomensis, differed between wet-cool and dry-warm microhabitats. At Arroyo Grande, California, 20 experimental plots were sampled, representing a factorial combination of wet-cool vs. dry-warm soil and plots that did or did not contain L. nipomensis. In a simultaneous greenhouse study, L. nipomensis was grown in drought and well-watered conditions to compare soil communities between field and greenhouse. RESULTS:A diversity of carbon-cycling microorganisms but not nitrogen-fixers were overrepresented in the field, and nitrogen-fixing bacteria were overrepresented in some greenhouse treatments. The microbial communities in the field soils were more species-rich and evenly distributed than in greenhouse communities. In field plots, microhabitats significantly influenced community beta diversity, while field plots with or without L. nipomensis had no significant differences in alpha or beta diversity. CONCLUSIONS:Our study shows the utility of eDNA soil analysis in elucidating soil biome community differences for conservation and highlights the influence of plant microhabitats on soil microbe associations.

The western Joshua tree ( Yucca brevifolia Englm.) is a culturally and ecologically important species of the Mojave Desert that is threatened by climate change. The North American summer monsoon provides rainfall during an otherwise dry period, and some scenarios envision a 40% decrease in monsoon rainfall by 2100. We used summer water additions and the record-setting storm, Tropical Storm Hilary, to address the following questions: (1) Can Joshua trees use summer water pulses to improve water status, photosystem health, and carbon gain? and (2) Does pre-watering gas exchange physiology vary with antecedent water conditions? Measurement campaigns were undertaken in August of 2021 and 2023, which were dry (53 mm precipitation) and wet (383 mm precipitation) water years respectively. We measured leaf water potential, photosynthetic gas exchange, and chlorophyll a fluorescence of Joshua trees near Pioneertown, CA. Net leaf level CO 2 assimilation (A net ) for Y. brevifolia saw an average increase of 2.3 μmol CO 2 m −2 s −1 five days after the precipitation pulse in 2023, showing that Joshua trees can upregulate photosynthesis in response to summer precipitation. Stomatal conductance to water vapor increased in response to water in both years, by 80% in 2021 and by 500% in 2023. Our results suggest that the average monsoon precipitation pulse of 10 mm does not induce upregulation of photosynthesis, but precipitation pulses of sufficient magnitude can induce upregulation of multiple aspects of photosynthesis even at one of the hottest times of the year. Pre-watering differences between years were negligible, suggesting that antecedent effects dissipate within three and a half months without rain. Predicted decreases in monsoon rainfall may influence future summertime carbon gain by Joshua trees in the Mojave Desert.

Many terrestrial plant communities, especially forests, have been shown to lag in response to rapid climate change. Grassland communities may respond more quickly to novel climates, as they consist mostly of short-lived species, which are directly exposed to macroclimate change. Here we report the rapid response of grassland communities to climate change in the California Floristic Province. We estimated 349 vascular plant species' climatic niches from 829,337 occurrence records, compiled 15 long-term community composition datasets from 12 observational studies and 3 global change experiments, and analysed community compositional shifts in the climate niche space. We show that communities experienced significant shifts towards species associated with warmer and drier locations at rates of 0.0216 +/- 0.00592 degrees C yr(-1) (mean +/- s.e.) and -3.04 +/- 0.742 mm yr(-1), and these changes occurred at a pace similar to that of climate warming and drying. These directional shifts were consistent across observations and experiments. Our findings contrast with the lagged responses observed in communities dominated by long-lived plants and suggest greater biodiversity changes than expected in the near future.

Climate change is increasing the frequency and severity of short-term (~1 y) drought events-the most common duration of drought-globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function-aboveground net primary production (ANPP)-was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought.

Quantifying evapotranspiration is critical to accurately predict vegetation health, groundwater recharge, and streamflow generation. Hillslope aspect, the direction a hillslope faces, results in variable incoming solar radiation and subsequent vegetation water use that influence the timing and magnitude of evapotranspiration. Previous work in forested landscapes has shown that equator-facing slopes have higher evapotranspiration due to more direct solar radiation and higher evaporative demand. However, it remains unclear how differences in vegetation type (i.e., grasses and trees) influence evapotranspiration and water partitioning between hillslopes with opposing aspects. Here, we quantified evapotranspiration and subsurface water storage deficits between a pole- and equator-facing hillslope with contrasting vegetation types within central coastal California. Our results suggest that cooler pole-facing slopes with oak trees have higher evapotranspiration than warmer equator-facing slopes with grasses, which is counter to previous work in landscapes with singular vegetation types. Our water storage deficit calculations indicate that the pole-facing slope has a higher subsurface storage deficit and a larger seasonal dry down than the equator-facing slope. This aspect difference in subsurface water storage deficits may influence subsequent deep groundwater recharge and streamflow generation. In addition, larger root-zone storage deficits on pole-facing slopes may reduce their ability to serve as hydrologic refugia for oaks during periods of extended drought. This research provides a novel integration of field-based and remotely-sensed estimates of evapotranspiration required to properly quantify hillslope-scale water balances. These findings emphasize the importance of resolving hillslope-scale vegetation structure within Earth system models, especially in landscapes with diverse vegetation types.

Mountains present challenging habitats for biological conservation assessment and intervention. Atmospheric warming is pressuring populations, communities and ecosystems to move toward higher elevations, but increasingly variable precipitation patterns could enhance or reverse the upward trend. The effects of warming pressure from lower elevations combined with irregular annual precipitation pulses will be complicated by the squeeze cause by decreasing habitat area at higher elevations. Given the evidence to date this raises the question, can species' distributions on mountains ever be in climatic equilibrium?

Background and aims Both drought and vegetation restoration can have dramatic effects on plant community composition, but how they influence soil microbial community diversity, structure, and co-occurrence networks remain less well known. Methods To better understand the regulatory mechanisms of drought and vegetation restoration on soil microorganisms, we planted 12 native species in precipitation manipulation experimental plots in an invaded coastal grassland in California, USA. We measured soil bacterial and fungal community composition by amplicon sequencing, and quantified plant species richness and coverage in the third experimental year. Results Our results showed that drought significantly altered soil bacterial diversity and composition; however, neither drought nor vegetation restoration had significant effects on fungal diversity and composition. The control plots had the most cooperative interactions (greatest number of correlations) among bacterial and/or fungal species, while drought plots yielded the most complex co-occurrence network with the highest modularity and clustering coefficient. Structural equation modeling revealed that plant species richness, net gains, and soil moisture played dominant roles in shaping bacterial community structure. Drought and bacterial community structure directly affected fungal community structure. Plant dominant species cover, common species cover, and bacterial diversity were the key drivers in regulating the microbial co-occurrence network complex. Conclusion We conclude that soil bacterial and fungal communities differ in their responses to abiotic and biotic environmental changes, which may weaken the interspecies interactions among soil microorganisms.

Grassland and other herbaceous communities cover significant portions of Earth's terrestrial surface and provide many critical services, such as carbon sequestration, wildlife habitat, and food production. Forecasts of global change impacts on these services will require predictive tools, such as process-based dynamic vegetation models. Yet, model representation of herbaceous communities and ecosystems lags substantially behind that of tree communities and forests. The limited representation of herbaceous communities within models arises from two important knowledge gaps: first, our empirical understanding of the principles governing herbaceous vegetation dynamics is either incomplete or does not provide mechanistic information necessary to drive herbaceous community processes with models; second, current model structure and parameterization of grass and other herbaceous plant functional types limits the ability of models to predict outcomes of competition and growth for herbaceous vegetation. In this review, we provide direction for addressing these gaps by: (1) presenting a brief history of how vegetation dynamics have been developed and incorporated into earth system models, (2) reporting on a model simulation activity to evaluate current model capability to represent herbaceous vegetation dynamics and ecosystem function, and (3) detailing several ecological properties and phenomena that should be a focus for both empiricists and modelers to improve representation of herbaceous vegetation in models. Together, empiricists and modelers can improve representation of herbaceous ecosystem processes within models. In so doing, we will greatly enhance our ability to forecast future states of the earth system, which is of high importance given the rapid rate of environmental change on our planet.

As the world faces a changing climate, agriculture needs to develop more efficient and sustainable food production systems. Traditional farming methods consume considerable amounts of energy and are largely manually controlled, which leads to sub-optimal production. Green-houses, which enable year-round crop growth, can play an important role in efficient food production. Leveraging the need for artificial light in greenhouses when the natural sunlight available is not sufficient, we envision that recent progress in Internet of Things (IoT) technology, together with novel Light-Fidelity (LiFi)-based methods have the potential to significantly reduce energy and resources used in food production. In this article we describe our work towards sustainable and precision greenhouses by using LiFi-enabled IoT. Here we present a battery-free wireless network of IoT sensor nodes that exploit LiFi for both communication and power harvesting, while monitoring environmental conditions for optimal greenhouse operation and plant production. We highlight the research challenges and the way forward to integrate LiFi to monitor and control greenhouses, as well as a proof-of-concept LiFi-enabled IoT system for a real-world greenhouse.

Effective utilization of water is the cornerstone of maintaining plant biomass. Water use efficiency (WUE), defined as plant carbon assimilated as biomass per unit of water input, is significantly affected by global change, particularly by nitrogen (N) deposition. Generally, N availability promotes WUE by stimulating photosynthetic. However, the degree to which increased N availability may influence leaf WUE and photosynthesis properties (A, leaf net CO2 assimilation rate; gs, stomatal conductance, and E, transpiration rate), especially in salinized-alkalized grasslands, is not studied well. We conducted a randomized block manipulative experiment to evaluate the multilevel N addition (0, 5, 10, 20, 40 g N m− 2 year−1) on leaf photosynthesis properties and leaf WUE of the dominant species (Leymus chinensis (Trin.) Tzvelev) in the Songnen meadow steppe from 2016 to 2018. We have three key findings: (1) N availability increased photosynthetic and WUE properties, instantaneous WUE (Wi = A/E), intrinsic WUE (Wg =  A/gs) and long-term WUE (WL) inferred from 13C composition, were all showed a non-linear increasing pattern in response to N availability; (2) N application decreased leaf mass per area and increased leaf total N content via enhancing soil inorganic N content, thus increased photosynthetic characteristics (e.g., A, E and gs), ultimately, promoted Wi and Wg; (3) N application enhanced WL was attributed to the N-induced improvement in Wi and Wg. Results of the present work are critical to our prediction of how meadow steppe dominated by L. chinensis will respond to severe N deposition in the future.

Abstract Drought and competition affect how morphological and physiological traits are expressed in plants. California plants were previously found to respond less negatively to resource limitation compared to invasive counterparts. In a glasshouse in Santa Cruz, CA, USA, we exposed five native California C3 grassland species to episodic drought and competition (via five locally invasive species). We hypothesized that leaf morphology would be more affected by competition, and leaf photosynthetic gas exchange more so by drought, consistent with optimal partitioning and environmental filter theories. We expected that traits would exhibit trade‐offs along a spectrum for resource conservatism versus acquisition. Bromus carinatus had greater photosynthetic recovery, while Diplacus aurantiacus had lower percent loss of net assimilation (PLA) and intrinsic water‐use efficiency (iWUE) during drought and competition simultaneously compared to just drought. Stipa pulchra and Sidalcea malviflora gas exchange was unaffected by drought, and leaf morphology exhibited drought‐related adjustments. Lupinus nanus exhibited trait adjustments for competition but not drought. Functional traits sorted onto two principal components related to trade‐offs for resource conservatism versus acquisition, and for above‐ versus belowground allocation. In summary, morphological traits were affected by competition and drought, whereas physiological traits, like leaf gas exchange, were primarily affected by drought. The grassland plants we studied showed diverse responses to drought and competition with trait trade‐offs related to resource conservatism versus acquisition, and for above‐ versus belowground allocation consistent with optimal partitioning and environmental filter theories. Diplacus aurantiacus experienced competitive release based on greater iWUE and lower PLA when facing drought and competition.

Incorporating physiology into models of population dynamics will improve our understanding of how and why invasions succeed and cause ecological impacts, whereas others fail or remain innocuous. Targeting both organismal physiologists and invasion scientists, we detail how physiological processes affect every invasion stage, for both plants and animals, and how physiological data can be better used for studying the spatial dynamics and ecological effects of invasive species. We suggest six steps to quantify the physiological functions related to demography of nonnative species: justifying physiological traits of interest, determining ecologically appropriate time frames, identifying relevant abiotic variables, designing experimental treatments that capture covariation between abiotic variables, measuring physiological responses to these abiotic variables, and fitting statistical models to the data. We also provide brief guidance on approaches to modeling invasions. Finally, we emphasize the benefits of integrating research between communities of physiologists and invasion scientists.

1. Climate change will increase uncertainty in restoration outcomes due to greater water stress and other abiotic filters that limit plant survival. Drought-related plant functional traits can help species withstand filters in a semi-arid environment. Our objective was to provide guidance for selecting species to improve restoration success in a changing climate. 2. We planted 12 native species in ambient rainfall and under 60% rain-out shelters in an invaded coastal grassland in central California. We measured survival and size annually for 4 years and quantified plant community and trait composition in the third and fourth years. We measured growth rate, specific leaf area (SLA), leaf C:N, leaf lobedness and leaf delta C-13 of all planted species and dominant extant species, and evaluated the effect of treatments, traits and phylogenetics on mortality risk using Cox proportional hazards. 3. Native perennial species cover was greater, whereas thatch depth and per cent cover of shrubs and non-native annual grasses were lower, on drought plots. Drought plots had lower community-weighted leaf C:N and higher leaf lobedness. 4. Planted species with resource conservative traits, such as higher leaf lobedness and lower growth rate, had lower mortality risk. Increased plasticity of morphological traits (SLA and lobedness) was associated with decreased mortality risk, whereas increased plasticity of physiological traits (leaf C:N and delta C-13) and risk was positively correlated. Trait plasticity explained a greater degree of plant mortality risk compared to absolute trait values. 5. Plants that were more phylogenetically related to the surrounding plant community had lower mortality risk. Traits of planted species that were important for determining plant mortality in this coastal grassland may be conserved, which was supported by a phylogenetic signal (Blomberg's K = 0.380, Pagel's lambda = 0.830) in leaf C:N. 6. Synthesis and applications. Our results suggest that leaf traits and phylogenetics could serve as plant selection criteria for reducing plant mortality risk during drought, thereby improving restoration outcomes. Because some traits have a phylogenetic signal that explains drought survival, restoration practitioners could expand the use of trait-based selection for closely related species when restoring other arid- and semi-arid ecosystems.

In coastal California, the peak growing season of economically important crops is concurrent with fog events, which buffer drought stress during the dry season. Coastal fog patterns are changing, so we quantified its effects on the energy, water, and carbon fluxes of a strawberry farm located in the fog‐belt of the Salinas Valley, California. We used Geostationary Operational Environmental Satellite (GOES) total albedo to detect and quantify large scale patterns of coastal fog. We used eddy covariance (EC) to quantify actual evapotranspiration and gross primary productivity (GPP) at the field scale (approximately 0.5–3 hectares) from June to September 2016. We measured canopy‐scale (approximately 0.6 m2) strawberry physiology on foggy and non‐foggy days within the measurement footprint of the EC tower. Downwelling longwave radiation (L↓), observed by a surface‐mounted pyrgeometer, was consistently higher on foggy compared to clear‐sky days (regardless of fog‐drip), indicating that emission of longwave radiation was derived almost entirely from the cloud base. L↓ and total GOES albedo were positively and strongly correlated (R2 = 0.68, P < 0.01). For both field‐ and canopy‐scales, water‐use and light‐use efficiency increased by as much as 50% and 70%, respectively, during foggy compared to non‐foggy conditions. The initial slope of the curvilinear relationship fit between GPP and photosynthetically active radiation was twice as steep during foggy (α = 0.0395) than non‐foggy (α = 0.0210) conditions, suggesting that the scattering of light during fog events enhances photosynthetic output of whole‐plants. Our results suggest that irrigation for these fields could be rescheduled during foggy periods without sacrificing plant productivity.

Increased climatic variability can impact tree physiological processes beyond what is predicted from changes in mean conditions. We assessed the sensitivity of conifer saplings to spatial and temporal variability in meteorological conditions, taking advantage of the end of California’s historic drought and the exceedingly wet winter of 2017. We sought to understand how very dry and very wet conditions constrain photosynthesis and growth in four regionally dominant conifers and whether sensitivity in these processes changes across a 500 m gradient in elevation. All species demonstrated phenotypic plasticity in response to temporal differences in precipitation on both inter-annual and seasonal timescales. Net photosynthesis in Pinus contorta decreased from an early season 2016 average of 12.4 to 6.89 μmol CO2 m−2 s−1 later in the summer, but increased 14.1% between seasons in the wet year. By contrast, elevation had almost no effect on instantaneous photosynthetic gas exchange, CO2 response curve parameters, or stem water potential in any of the years for any of the species. Effects of the heavy snow year (2017) on needle growth differed between elevations. Pinus contorta showed a 38.9% increase in average needle length at the lower two elevations but a 31.6% decrease at the highest site compared to the height of the drought. Despite these differences, biological variation was dampened compared to the physical variation between years, suggesting these trees can effectively withstand substantial meteorological variability. Our results show that these species demonstrated considerable ability to tolerate and recover from an extreme drought event.

Soil microorganisms are essential participants in ecosystem processes, yet their composition, diversity, and function are affected by altered precipitation. The patterns and key processes driving the effects of changes in precipitation on soil bacterial and fungal communities remain unclear. To better understand how changes in precipitation may affect soil microorganisms, we conducted a three-year field precipitation manipulation experiment, with treatments ranging from 50% reduction to 50% increases in precipitation, in a meadow steppe located in northeast China. Our results demonstrated that the bacterial community was more sensitive to changes in precipitation than the fungal community. The fungal community was sensitive to inter-annual differences in precipitation, but not to the treatment-induced changes in precipitation. Increased annual precipitation shifted the dominance of the microbial community from bacteria to fungi. Over the precipitation range (200-280 mm) soil microbial biomass and diversity are maximal, below the long-term mean annual precipitation (430 mm) for this site. Soil water content, pH, and total phosphorus were the main factors related to the variance in soil microbial community diversity. Results show non-linear, time-dependent, and interacting responses of bacterial and fungal biomass and diversity to soil properties under gradients of altered precipitation magnitude in this semi-arid grassland.

California is predicted to experience warmer temperatures and more frequent droughts in future years, which will increase local and regional climatic water deficit. Understanding how commonly used restoration species will respond to drought may help with approaches to mediate the negative impacts of changing climates on restoration. Associated plant functional traits can increase understanding of how a group of species responds to variable environmental conditions, and aid with selecting broader mixes of drought-tolerant plants for restoration. For this study, we established ambient rainfall, first-year watered and drought treatments (60% rainfall reduction), in a coastal grassland in Santa Cruz, CA. Drought was created using rain-out shelters that simulate a 1-in-100-year drought. We planted 12 California native coastal prairie species to determine which species and life-forms had greater survivorship. We monitored the survival of these plantings annually from 2016 to 2019 and assessed the plant community composition in 2018 and 2019. We found that rhizomatous forbs were ideal candidates for planting coastal prairie restoration sites, especially in terms of drought. Bunchgrasses were also successful in the drought treatment, but to a lesser degree. Nfixers and non-rhizomatous forbs had minimal survivorship by the fourth year. Our findings demonstrate variable survival of planted seedlings in terms of time and drought. Additionally, from our study, the most favorable candidates for restoring California coastal prairie in a drier climate were common yarrow (Achillea millefolium), prairie mallow (Sidalcea malviflora), and purple needle grass (Stipa pulchra).