Fernando T. Maestre

Book review: “The Art of Making (Critical) Questions: Resilient Thinking and Scientific Craftsmanship” by Raúl Ochoa-Hueso, 2026. Becoming a scientist involves much more than learning how to design experiments, collect data, and analyze them. It requires developing a way of observing, thinking, reading, writing, and relating to others and, no less importantly, learning how to navigate an academic world that is increasingly competitive, demanding, and uncertain. This book addresses many of these dimensions from a highly personal perspective, combining reflections on the scientific craft with numerous practical recommendations aimed especially at those taking their first steps in research.

Drylands cover a large fraction of the terrestrial surface and are highly vulnerable to climate change; yet, long-term experimental platforms devoted to their study remain scarce. This case study synthesizes nearly two decades of research conducted at the Aranjuez Experimental Station (AES), a semiarid gypsum steppe in central Spain that has supported multiple observational studies, manipulative experiments and long-term monitoring aimed at understanding how plants, soils and biocrusts interact to regulate dryland structure and functioning and how organisms modulate ecosystem responses to climate change. Research at the AES has shown that plant–plant interactions vary with microclimate, ontogeny, water availability and herbivory; that biocrusts are key regulators of nitrogen, phosphorus and carbon cycling, soil respiration, infiltration and soil water dynamics; and that lichen-dominated biocrusts are highly sensitive to warming. At the same time, a long-term climate change experiment conducted at the AES has revealed that well-developed biocrusts can buffer warming effects on nutrient pools, greenhouse gas fluxes and soil moisture. The results obtained from the AES illustrate the value of long-term, integrative field research for understanding dryland resilience and vulnerability and highlight the key role of biocrusts as modulators of ecosystem responses to climate change.

Drylands store most of the global soil inorganic carbon (SIC), yet the extent to which this pool interacts with contemporary carbon (C) cycling remains poorly understood. To test whether SIC behaves primarily as an inert geological reservoir or instead bears a modern carbon imprint, we quantified SIC content and radiocarbon (∆ ¹⁴ C) at 42 dryland sites spanning broad aridity gradients across Eurasia. We also evaluated the climatic, edaphic, and biotic factors associated with variation in ∆ ¹⁴ C‐SIC. Across all sites, topsoil SIC (~0–10 cm) was strongly depleted in ¹⁴ C but consistently enriched relative to ¹⁴ C‐dead carbonates, indicating that it contains a measurable component derived from modern carbon inputs. In the Chinese drylands, ∆ ¹⁴ C‐SIC declined with increasing aridity, consistent with weaker modern carbon exchange under drier conditions and a greater contribution of inherited or ¹⁴ C‐depleted carbonate carbon. Soil pH and ∆ ¹⁴ C of soil organic carbon were the strongest predictors of ∆ ¹⁴ C‐SIC, suggesting that carbonate dissolution‐reprecipitation and the age of carbon entering soil CO ₂ play key roles in determining SIC origins. At a subset of nine Chinese sites, ∆ ¹⁴ C‐SIC declined sharply with depth and approached ¹⁴ C‐dead values in subsoils, indicating little influence of modern carbon in deeper carbonate pools. The presence of mixed ¹⁴ C‐depleted and modern ¹⁴ C signatures in SIC potentially complicates the use of SIC isotopic signatures as proxies of environmental conditions. Together, our results indicate that dryland topsoil SIC commonly carries a measurable modern carbon signature that is tightly linked to contemporary carbon cycling. This coupling weakens with increasing aridity and soil depth, suggesting that environmental change in drylands may reshape one of the planet's largest carbon pools not only through changes in SIC stocks, but also through shifts in carbonate radiocarbon signatures and sources.

Dissolved organic matter (DOM) is a central component of Earth’s carbon cycle and one of the planet’s most chemically diverse pools, yet the molecular structures of its constituents remain largely unresolved. This limitation has hindered our ability to link DOM composition to microbial processes and ecosystem function. Here we present ENVnet, a global molecular repository built from tandem mass spectrometry data collected across 13 terrestrial and aquatic environment types, including 419 newly generated samples that expand publicly available DOM metabolomics data and cover previously underrepresented environments. By computationally deconvolving chimeric mass spectra, a longstanding challenge in environmental metabolomics, we recover high-quality fragmentation data for >22,000 distinct molecular features (defined by a specific precursor mass and fragmentation pattern). Using ENVnet, we uncover conserved and environment-specific molecular patterns in DOM composition and underlying biogeochemical processes. We also use molecular features encoded in ENVnet to train predictive models of DOM persistence, allowing molecular-level assessment of microbial turnover in independent systems.

Biocrusts are soil‐surface assemblages of cryptogams, microbial communities, and soil particles, constituting the “living skin” of drylands. They are critical for global carbon and nitrogen cycles but are endangered by climate change. Safeguarding these critical components and their functions requires accurately measuring biocrust distribution and traits. Biocrust key functional indicators, such as pigments, provide information about their developmental stage, biomass, and functional state, but their remote quantification across spatial scales remains underdeveloped. We evaluated the potential of local‐scale (tripod‐acquired) multispectral imagery with machine learning to estimate pigments (scytonemin, chlorophyll a , carotenoids), soil organic carbon (SOC), and nitrogen (N) in two contrasting deserts: the Chihuahuan Desert (NM) and the Colorado Plateau (UT). High‐resolution imagery (< 1 mm) alongside pigments and nutrient concentrations was collected. At NM site, support vector regressions (SVR) using blue and red bands achieved high accuracy for scytonemin ( R ² = 0.93); red‐edge band enhanced predictions for SOC and N ( R ² = 0.95 and 0.80, respectively). In UT, predictive accuracy was lower ( R ² < 0.6), likely due to scytonemin saturation. Scytonemin‐based predictions of biocrust cover were less sensitive to moisture variability than chlorophyll a or carotenoids, suggesting scytonemin's superiority as a biocrust index compared to previously developed indices. The best‐performing local‐scale models at the NM site successfully scaled to landscape‐scale UAS imagery, allowing the remote prediction of pigments and nutrients and capturing relative differences associated with biocrust successional stages but did not capture the exact values of the modeled parameters compared to local measurements. The approach shows promise for future integration with satellite imagery to expand biocrust trait mapping at broader scales, offering a valuable tool for monitoring these key soil ecosystems and their functional attributes across diverse landscapes.

Aridity alters soil carbon (C), nitrogen (N) and phosphorus (P) stoichiometry, yet the implications of these processes for soil microbial functional traits and potentials at the genomic level remain poorly synthesized. Here we combine measurements of soil C, N and P pools and ratios with shotgun metagenomes from 200 natural ecosystems spanning major biomes worldwide. Across sites, increased aridity is associated with lower soil C:N and N:P (and C:P) ratios and with a coordinated shift in microbial functional potential. Genes linked to catabolic resource acquisition—including carbohydrate-active enzymes and pathways for degradation of plant litter and organophosphorus compounds—are declined as C becomes relatively scarce. In contrast, genes supporting anabolic investment in growth and drought resistance, such as RNA transcription, protein synthesis and intracellular transport, are increased. These patterns indicate that aridity-related change in soil elemental ratios is coupled to a broad shift from catabolic to anabolic strategies in soil microbiomes. By linking soil elemental ratios to microbial functional traits across biomes, our study provides a framework for anticipating how climate-driven drying may reorganize microbial metabolism with consequences for carbon and nutrient cycling.

Microbes, as the planet's most abundant and diverse organisms, drive soil functions globally and are vulnerable to environmental stressors triggered by global change. Yet, knowledge regarding the impacts of multiple environmental stressors on their functional profiles as well as the consequences for soil functionality largely remains unknown. Here, we analyze two global-scale datasets including information on soil metagenomics and multiple environmental stressors. We find that across terrestrial ecosystems worldwide, up to 60% of all functional genes significantly shift when soil microbes experience the high-level of concurrent stressors. In this regard, the relative abundances of genes involved in microbial growth are negatively linked to the increasing number of stressors. Conversely, those genes linked to stress resistance and energy production exhibit positive responses. Taken together, our findings highlight a significant restructuring of global soil functional microbiomes in response to multiple environmental stressors. Consequently, such restructuring drives community-level shifts in matter and energy reallocations, thereby impacting the maintenance of soil functionality under the projected global change.

Dryland ecosystems rely on infrequent rainfall pulses to activate soil microbial communities, yet the fraction and identity of microbes resuscitating after hydration remain unclear. We applied bioorthogonal non-canonical amino acid tagging coupled with fluorescence-activated cell sorting (BONCAT-FACS) and 16S rRNA gene sequencing to identify translationally active bacteria in early (L-BSC) and late (D-BSC) successional cyanobacteria-dominated biocrusts subjected to simulated rainfall under light and dark conditions. Our results reveal that only a small subset of the microbial community resumes activity within six hours, with higher active cell abundances in mature crusts. Microbial activity patterns were largely independent of light exposure and showed partial decoupling from total community composition, indicating that presence does not predict short-term function. These findings suggest that biocrust maturity shapes microbial activation dynamics and that functional responses to precipitation pulses are governed by a conserved pool of fast responders, informing predictions of dryland soil microbiome resilience under changing precipitation regimes.