Raúl Ochoa-Hueso

Overgrazing by sheep causes degradation of grasslands in the Inner Mongolian steppe, yet our understanding of its impact on grassland plant communities is limited by lack of observations at high spatial resolution. Employing a nested experimental design in a long-term grazing experiment provides insights into effects of increasing sheep grazing intensity on community composition, diversity, and spatial patterns in the grassland vegetation. Effects of observed changes in the plant community are discussed based on monthly weight gain of sheep during grazing. The design of the long-term experiment included four triplicated grazing intensities applied during an 8-year period. At the end of that period, we evaluated vegetation coverage, categorized plant species by functional groups, and analyzed the data using a mixed linear model. Moreover, spatial autocorrelation methods were employed to investigate spatial patterns, visualized via a kriging model. We found that the plant community composition differed among grazing treatments, with high grazing intensity showing higher plant species richness and stronger clustering of plants at our fine scale of observation. These fine-grained spatial scale observations are usually not recorded in larger spatial scale analyses of grassland responses to overgrazing. While the grazing intensities used in our study did not influence individual sheep weight gain, total sheep weight gain per hectare increased with an increase in grazing intensity. Our study shows that in a sheep grazing intensity experiment in Inner Mongolia grasslands total sheep weight gain may increase at the expense of fine-scale species composition and spatial dynamics of the grassland vegetation. These insights may be used for determining trade-offs of sheep meat production with original composition and structure of grassland plant communities. Effects on other ecosystem properties and functions, such as on belowground biodiversity, remain to be assessed.

Monitoring agriculture by remote sensing enables large-scale evaluation of biomass production across space and time. The normalized difference vegetation index (NDVI) is used as a proxy for green biomass. Here, we used satellite-derived NDVI of arable farms in the Netherlands to evaluate changes in biomass following conversion from conventional to organic farming. We compared NDVI and the stability of NDVI across 72 fields on sand and marine clay soils. Thirty-six of these fields had been converted into organic agriculture between 0 and 50 years ago (with 2017 as reference year), while the other 36 were paired control fields where conventional farming continued. We used high-resolution images from the Sentinel-2 satellite to obtain NDVI estimates across 5 years (January 2016–October 2020). Overall, NDVI did not differ between conventional and organic management during the time series, but NDVI stability was significantly higher under organic management. NDVI was lower under organic management in sandy, but not in clay, soils. Organic farms that had been converted less than ~19 years ago had lower NDVI than conventional farms. However, the difference diminished over time and eventually turned positive after ~19 years since the conversion. NDVI, averaged across the 5 years of study, was positively correlated to soil Olsen-P measured from soil samples collected in 2017. We conclude that NDVI in organic fields was more stable than in conventional fields, and that the lower biomass in the early years since the transition to organic agriculture can be overcome with time. Our study also indicates the role of soil P bioavailability for plant biomass production across the examined fields, and the benefit of combining remote sensing with on-site soil measurements to develop a more mechanistic understanding that may help us navigate the transition to a more sustainable type of agriculture.

There is an increasing interest in developing agricultural management practices that support a more nature-based, sustainable food production system. In organic systems, extracellular enzymes released by soil microorganisms are important regulators of the cycling and bioavailability of plant nutrients due to the lack of synthetical inputs. We used a chronosequence coupled with a paired field approach to evaluate how potential activity of hydrolytic soil extracellular enzymes changed over time (0–69 years) during the transition from conventional to organic agriculture in two types of soils, marine clay and sandy soils. Organic management generally enhanced the activity of enzymes related to the C cycle, particularly in sandy soils, and increased the proportion of C-related enzymes relative to N- and P-related enzymes. Differences in soil extracellular enzyme activity between organic and conventional farming increased with time since conversion to organic farming for α-β-glucosidase, xylosidase, phosphomonoesterase, 4-N-acetylglucosaminidase, arylsulphatase, and the ratio of C:N enzymes. In some cases, the divergence in enzyme activity was driven by enhanced activity with time in organic fields, but in others by reduced activity over time in conventional fields. Our findings suggest that organically managed soils with higher enzyme activity may have a greater potential for organic matter breakdown, residue decomposition, and higher rates of cycling of C and nutrients. However, these positive effects may take time to become apparent due to legacy effects of conventional management.

Global biogeochemical cycles have been widely altered due to human activities, potentially compromising the ability of plants to regulate their metabolism. We grew experimental herbaceous communities simulating the understory of eucalypt forests from southeastern Australia to evaluate the effects of elevated CO₂ (400 vs. 650 ppm) and changes in soil resource availability (high-low water and high-low P) on the concentration of fourteen essential plant macro- and micronutrients, and their degree of coupling. Coupling was based on correlations among all elements in absolute value and a null modeling approach. According to the ancient nature of Australian soils, P addition was the main driver of changes in plant tissue chemistry, increasing the concentrations of P, Mg, Ca, and Mn and reducing the concentrations of C, N, S, Na, and Cu. Most treatment combinations showed coupled patterns of plant elements, particularly under ambient CO₂. However, under elevated CO₂, elements in plant tissues became more decoupled, which was interpreted as the result of a lack of enough supply of a range of elements to satisfy greater demands. Across treatments, P, Mn, and N were the least coupled elements, while K, Ca, and Fe were the most coupled ones. We provide evidence that plant element coupling was positively related to the concentration and coupling of elements measured in soils worldwide, suggesting that plant element coupling is conserved. Our results provide compelling evidence that evaluating the coupling of a representative range of chemical elements in plant tissues may represent a highly novel and powerful indicator of nutritional mismatches between demand and supply under specific environmental circumstances, including in a resource-altered global change context.

Extensive livestock grazing is a global human activity. In the Iberian Peninsula, extensive grazing and seminatural grasslands and open woodlands such as dehesas have co-evolved with human use for millennia. However, social, demographic, and economic factors are now pushing this traditional activity towards both conventional intensification and land abandonment, with consequences for the biodiversity and functioning of these seminatural ecosystems. Soils can be particularly affected by grazing abandonment due to the cessation of inputs of pre-processed organic matter (dungs and urine) and of trampling, with still poorly understood consequences for the composition, network configuration, and activity of soil microbial communities and the capacity of soils to store C. In this work, we used 20 pairs of adjacent plots (40 plots in total) located in seminatural grasslands from central Spain. For each pair, one plot was extensively grazed by livestock and the other one was abandoned. We evaluated the effects of extensive grazing abandonment on soil fertility (C and N contents, and P and K bioavailability), forage quality (fibre and protein content), and soil microbial community composition (amplicon sequencing of 16 S [bacteria] and ITS [fungi]), network coupling, and activity (extracellular hydrolytic enzymes linked to the biogeochemical cycling of C, N, P, and S). Grazing resulted in higher soil fertility in terms of C, N, and P, and grassland forage quality (lower fibre). Grazing also affected soil microbial community composition, but not richness or diversity. These effects occurred primarily through changes in nutrients and soil water availability. Actinobacteria significantly increased in abandoned plots, while Acidobacteria, Verrucomicrobia, and Planctomycetes decreased. Bacterial and, particularly, fungal networks were generally less coupled in abandoned plots. Furthermore, grazing resulted in greater soil enzyme activity via direct effects. These results support the notion that extensive grazing with intermediate stocking rates provides a positive effect on grass quality, soil fertility, nutrient cycling, and microbial network configuration, and thus warn about the potential negative effects of land abandonment.

Background and aims: Increased N deposition can break the coupled associations among chemical elements in soil, many of which are essential plant nutrients. We evaluated the effects of four years of N deposition (0, 10, 20, 50 kg N ha⁻¹ yr⁻¹) on the temporal dynamics of the spatial co-variation (i.e., coupling) among ten chemical elements in soils from a semiarid shrubland in central Spain. Methods: Soil element coupling was calculated as the mean of Spearman rank correlation coefficients of all possible pairwise interactions among elemental cycles, in absolute value. We also investigated the role of atomic properties of elements as regulators of coupling. Results: While N deposition impacts on nutrient bioavailability were variable, soil elemental coupling consistently increased in response to N. Coupling responses also varied among elements and N treatments, and four out of ten elemental cycles also responded to N in a season-dependent manner. Atomic properties of elements such as mass, valence orbitals, and electronegativity contributed to explain the spatial coupling of soil elements, most likely due their role on the capacity of elements to interact with one another. Conclusions: The cumulative effects of N deposition can alter the spatial associations among chemical elements in soils, while not having evident consequences on the bioavailability of single elments. These results indicate that considering how multiple elements co-vary in topsoils may provide a useful framework to better understand the simultaneous response of multiple elemental cycles to global change.

Human activities cause substantial changes in biodiversity.^1,2 Despite ongoing concern about the implications of invertebrate decline,^3,4,5,6,7 few empirical studies have examined the ecosystem consequences of invertebrate biomass loss. Here, we test the responses of six ecosystem services informed by 30 above- and belowground ecosystem variables to three levels of aboveground (i.e., vegetation associated) invertebrate community biomass (100%, 36%, and 0% of ambient biomass) in experimental grassland mesocosms in a controlled Ecotron facility. In line with recent reports on invertebrate biomass loss over the last decade, our 36% biomass treatment also represented a decrease in invertebrate abundance (−70%) and richness (−44%). Moreover, we simulated the pronounced change in invertebrate biomass and turnover in community composition across the season. We found that the loss of invertebrate biomass decreases ecosystem multifunctionality, including two critical ecosystem services, aboveground pest control and belowground decomposition, while harvested plant biomass increases, likely because less energy was channeled up the food chain. Moreover, communities and ecosystem functions become decoupled with a lower biomass of invertebrates. Our study shows that invertebrate loss threatens the integrity of grasslands by decoupling ecosystem processes and decreasing ecosystem-service supply.

Understanding the chemical composition of our planet's crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro- and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome-dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling-atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world.

Soil life supports the functioning and biodiversity of terrestrial ecosystems. Springtails (Collembola) are among the most abundant soil arthropods regulating soil fertility and flow of energy through above- and belowground food webs. However, the global distribution of springtail diversity and density, and how these relate to energy fluxes remains unknown. Here, using a global dataset representing 2470 sites, we estimate the total soil springtail biomass at 27.5 megatons carbon, which is threefold higher than wild terrestrial vertebrates, and record peak densities up to 2 million individuals per square meter in the tundra. Despite a 20-fold biomass difference between the tundra and the tropics, springtail energy use (community metabolism) remains similar across the latitudinal gradient, owing to the changes in temperature with latitude. Neither springtail density nor community metabolism is predicted by local species richness, which is high in the tropics, but comparably high in some temperate forests and even tundra. Changes in springtail activity may emerge from latitudinal gradients in temperature, predation and resource limitation in soil communities. Contrasting relationships of biomass, diversity and activity of springtail communities with temperature suggest that climate warming will alter fundamental soil biodiversity metrics in different directions, potentially restructuring terrestrial food webs and affecting soil functioning.

Grasslands across arid and semi-arid regions are predicted to experience reductions in precipitation frequency. Besides, grassland degradation has become a serious problem in many of these areas. Despite increasing evidence suggesting compound effects of these synchronous alterations on biotic and abiotic ecosystem constituents, we still do not know how they will impact the coupling among ecosystem constituents and its consequences on ecosystem functioning. Here, we assessed the effects of decreased precipitation frequency and grassland degradation on ecosystem coupling, quantified based on the mean strength of pairwise correlations among multispecies communities and their physicochemical environment, individual functions and ecosystem multifunctionality, and reported their relationships within a mechanistic plant–nematode–micro-organism–soil interactions framework. Decreased precipitation frequency led to poorly coupled ecosystems, and reduced aboveground plant biomass, soil water content, soil nutrient levels, soil biota abundance and multifunctionality. By contrast, belowground plant biomass and soil potential enzyme activities increased under decreased precipitation frequency treatment. Severe degradation resulted in decoupled ecosystems and suppressed most of individual functions and multifunctionality. Using structural equation modelling, we showed that coupling had a strong direct positive effect on multifunctionality (standardized total effect: 0.74), while multifunctionality was weakened by greater soil water variation (−0.54) and higher soil pH (−0.53). The great sensitivity of ecosystem coupling to altered precipitation regimes and degradation highlights the importance of considering interactions among biotic and abiotic components when predicting early ecological impacts under changing environments. Moreover, the positive relationship between ecosystem coupling and functioning suggests that restoration of degraded grasslands may be achieved by intensifying ecological interactions.

Vineyards are a very important perennial woody crop globally, but they are also among the most intensively managed agroecosystems. This has resulted in biologically impoverished and highly eroded vineyards. Environmentally-friendly inter-row vegetation management, particularly the use of cover crops, could contribute to avoid erosion and regenerate soil biodiversity in vineyards. In this study, we updated a global meta-analysis on the effects of inter-row extensive vegetation cover management, particularly through the use of cover crops, on ecosystem services, including supporting, regulating and provisioning services, and biodiversity in vineyards. We also analyzed the role of environmental variables (climate, including precipitation- and temperature-related bioclimatic variables and soil properties, including pH and texture) and irrigation in modulating these effects. The presence of extensive vegetation cover consistently increased biodiversity, as well as supporting ecosystem services in irrigated vineyards and regulating services in rainfed vineyards. Provisioning services, which were evaluated as grape yield, were slightly negatively affected in rainfed vineyards, but not in irrigated ones. The effects of vegetation cover on ecosystem services varied depending on the climate and edaphic characteristics of vineyards. For example, supporting ecosystem services were favored in acidic soils and were also positively related to the precipitation of the wettest quarter, whereas regulating services were particularly enhanced in alkaline soils and in locations with lower temperatures of the wettest quarter. Biodiversity was especially favored in locations with lower precipitation seasonality. Taken together, our study indicates the importance of developing strategies for the adaptive management of extensive vegetation covers tailored to the climatic and edaphic conditions of each vineyard. This adaptive management, combined with irrigation and potentially other locally-tailored adaptive strategies, could also contribute to further mitigate potential negative effects of vegetation cover on grape production while maximizing other ecosystem services such as provisioning and supporting services and biodiversity.

Grasslands are now facing a continuously increasing supply of nitrogen (N) fertilizers, resulting in alterations in ecosystem functioning, including changes in carbon (C) and water cycling. Mowing, one of the most widely used grassland management techniques, has been shown to mitigate the negative impacts of increased N availability on species richness. However, knowledge of how N addition and mowing, alone and/or in combination, affect ecosystem-level C fluxes and water use efficiency (W_N) is still limited. We experimentally manipulated N fertilization (0 and 10 g N m⁻² yr⁻¹) and mowing (once per year at the end of the growing season) following a randomized block design in a meadow steppe characterized by salinization and alkalinization in northeastern China. We found that, compared to the control plots, N addition, mowing, and their interaction increased net ecosystem CO₂ exchange by 65.1%, 14.7%, and 133%, and W_N by 40.7%, 18.5%, and 96.1%, respectively. Nitrogen enrichment also decreased soil pH, which resulted in greater aboveground biomass (AGB). Moreover, N addition indirectly increased AGB by inducing changes in species richness. Our results indicate that mowing enhances the positive effects of N addition on ecosystem C fluxes and W_N. Therefore, appropriate grassland management practices are essential to improve ecosystem C sequestration, W_N, and mitigate future species diversity declines due to ecosystem eutrophication.

Evaluation of restoration activities is indispensable to assess the extent to which targets have been reached. Usually, the main goal of ecological restoration is to restore biodiversity and ecosystem functioning, but validation is often based on a single indicator, which may or may not cope with whole-ecosystem dynamics. Network analyses are, however, powerful tools, allowing to examine both the recovery of various biotic and abiotic properties and the integrated response at community and ecosystem level. We used restoration sites where topsoil was removed from former intensively managed grassland and seeds were added. These sites were between 3 and 32 years old. We assessed how plants, soil biota, soil properties and correlation-based interactions between biotic communities and their abiotic environment developed over time and compared the results with (i) intensively managed (not restored), and (ii) well-preserved targeted semi-natural grasslands. Plant, nematode, fungal and prokaryotic diversity and community structures of the restored grasslands revealed clear successional patterns and followed similar trajectories towards targeted semi-natural grasslands. All biotic communities reached targeted diversity levels no later than 18 years post-restoration. Ecological networks of intensively managed and short-term (~4 years) restored grasslands were less tightly connected compared to those found in mid- and long-term (~18–30 years) restored and target grasslands. Restoration specifically enhanced interactions among biotic communities, but reduced interactions between biotic communities and their abiotic environment as well as interactions among abiotic properties in the short- and mid-term. Synthesis and applications: Overall, our study demonstrated that topsoil removal and seed addition were successful in restoring diverse, tightly coupled and well-connected biotic communities above- and below-ground similar to those found in the semi-natural grasslands that were restoration targets. Network analyses proved to be powerful in examining the long-term re-establishment of functionally connected biotic communities in restored ecosystems. Thus, we provide an approach to holistically assess restoration activities by notably considering the complexity of ecosystems, much in contrast to most traditional approaches.

Current and continuing climate change in the Anthropocene epoch requires sustainable agricultural practices. Additionally, due to changing consumer preferences, organic approaches to cultivation are gaining popularity. The global market for organic grapes, grape products, and wine is growing. Biostimulant and biocontrol products are often applied in organic vineyards and can reduce the synthetic fertilizer, pesticide, and fungicide requirements of a vineyard. Plant growth promotion following application is also observed under a variety of challenging conditions associated with global warming. This paper reviews different groups of biostimulants and their effects on viticulture, including microorganisms, protein hydrolysates, humic acids, pyrogenic materials, and seaweed extracts. Of special interest are biostimulants with utility in protecting plants against the effects of climate change, including drought and heat stress. While many beneficial effects have been reported following the application of these materials, most studies lack a mechanistic explanation, and important parameters are often undefined (e.g., soil characteristics and nutrient availability). We recommend an increased study of the underlying mechanisms of these products to enable the selection of proper biostimulants, application methods, and dosage in viticulture. A detailed understanding of processes dictating beneficial effects in vineyards following application may allow for biostimulants with increased efficacy, uptake, and sustainability.

Increased human-derived nitrogen (N) loading in terrestrial ecosystems has caused widespread ecosystem-level phosphorus (P) limitation. In response, plants and soil micro-organisms adopt a series of P-acquisition strategies to offset N loading-induced P limitation. Many of these strategies impose costs on carbon (C) allocation by plants and soil micro-organisms; however, it remains unclear how P-acquisition strategies affect soil C cycling. Herein, we review the literature on the effects of N loading on P limitation and outline a conceptual overview of how plant and microbial P-acquisition strategies may affect soil organic carbon (SOC) stabilization and decomposition in terrestrial ecosystems. Excessive input of N significantly enhances plant biomass production, soil acidification, and produces plant litterfall with high N/P ratios, which can aggravate ecosystem-level P limitation. Long-term N loading can cause plants and soil micro-organisms to alter their functional traits to increase P acquisition. Plants can release carboxylate exudates and phosphatases, modify root morphological traits, facilitate the formation of symbiotic associations with mycorrhizal fungi and stimulate the abundance of P-mineralizing and P-solubilizing micro-organisms. Releasing carboxylate exudates and phosphatases could accelerate SOC decomposition, whereas changing symbiotic associations and root morphological traits (e.g. an increase in fine root length) may contribute to higher SOC stabilization. Increased relative abundances of P-mineralizing and P-solubilizing bacteria can accelerate P mining and SOC decay, which may decrease microbial C use efficiency and subsequently lower SOC sequestration. The trade-offs between different plant P-acquisition strategies under N loading should be among future research priorities due to their cascading impacts on soil C storage. Quantifying ecosystem thresholds for P adaption to increased N loading is important because P-acquisition strategies are effective when N loading is below the N threshold. Moreover, understanding the response of P-acquisition strategies at different levels of native soil N availability could provide insight to divergent P-acquisition strategies across sites and ecosystems. Altogether, P-acquisition strategies should be explicitly considered in Earth System Models to generate more realistic predictions of the effects of N loading on soil C cycling. Read the free Plain Language Summary for this article on the Journal blog.

The growing demand for timber and the boom in massive tree-planting programs could mean the spreading of mismanaged tree plantations worldwide. Here, we apply the concept of ecological intensification to forestry systems as a viable biodiversity-focused strategy that could be critical to develop productive, yet sustainable, tree plantations. Tree plantations can be highly productive if tree species are properly combined to complement their ecological functions. Simultaneously considering soil biodiversity and animal-mediated biocontrol will be critical to minimize the reliance on external inputs. Integrating genetic, functional, and demographic diversity across heterogeneous landscapes should improve resilience under climate change. Designing ecologically intensified plantations will mean breaking the timber productivity versus conservation dichotomy and assuring the maintenance of key ecosystem services at safe levels.

Global change frequently disrupts the connections among species, as well as among species and their environment, before the most obvious impacts can be detected. Therefore, we need to develop a unified conceptual framework that allows us to predict early ecological impacts under changing environments. The concept of coupling, defined as the multiple ways in which the biotic and abiotic components of ecosystems are orderly connected across space and/or time, may provide such a framework. Here, we operationally define the coupling of ecosystems based on a combination of correlational matrices and a null modeling approach. Compared with null models, ecosystems can be (1) coupled; (2) decoupled; and (3) anticoupled. Given that more tightly coupled ecosystems displaying higher levels of internal order may be characterized by a more efficient capture, transfer, and storage of energy and matter (i.e., of functioning), understanding the links between coupling and functioning may help us to accelerate the transition to planetary-scale sustainability. This may be achieved by promoting self-organized order.