Rewilding soil-disturbing vertebrates to rehabilitate degraded landscapes: benefits and risks

Soil-disturbing animals are common globally and play important roles in creating and maintaining healthy functional soils and landscapes. Yet many of these animals are threatened or locally extinct due to habitat loss, predation by non-native animals or poaching and poisoning. Some reintroduction and rewilding programmes have as their core aims to increase animal populations and reinstate processes that have been lost due to their extirpation. Here we use a meta-analytical approach to review the effects of soil-disturbing vertebrates on ecosystem processes, and advance the argument that they can be used to rehabilitate degraded ecosystems by altering mainly composition and function, but with fewer positive effects on structure. We describe four examples where the loss or reintroduction of soil-disturbing vertebrates leads to ecosystem state changes and highlight the role of spatial scale, covarying management changes, and species co-occurrence in modulating their effects. We discuss the advantages and disadvantages of using soil-disturbing vertebrates over mechanized engineering approaches such as pitting and furrowing, considering some advantages to include more self-sustainable and heterogeneous disturbances, creation of new habitats and added recreational values. Finally, we identify key knowledge gaps in our understanding of the use of soil-disturbing vertebrates for rehabilitating degraded ecosystems.This research was funded by the Hermon Slade Foundation (grant no. HSF21040)

Thinning and plantation of resprouting species redirect overstocked pine stands towards more functional communities in the Mediterranean basin

Post-fire regeneration in Pinus halepensis' forests, one of the most abundant vegetation types in the Mediterranean basin, often generates overstocked and vulnerable stands. They accumulate a high fuel load, increasing the risk of further fires, and present high levels of vulnerability due to their reduced seed production. In addition, these dense stands substantially reduce the availability of light and nutrients, which may hinder the recruitment of other species, often generating mono-specific and homogeneous stands, which potentially supply fewer ecosystem services than mixed forests with more heterogeneous structures. In these dense pine stands, management is of high priority to reduce fire hazards and promote their functionality. In overstocked pine stands (>75,000 trees·ha−1), we assessed the long-term effects (10 years) of two thinning levels (600 and 1200 trees·ha−1), in combination with the plantation of Quercus faginea (a resprouter species typical of advanced successional stages in our study area) on 28 above and belowground ecosystem attributes, including fire hazard. After ten years, thinning and plantation interacted to enhance ecosystem attributes associated with disturbance regulation and biodiversity conservation (up to 200%) and food production (up to 90%), while no effects were observed on those attributes related to carbon sequestration and supporting services. These effects were mainly driven by aboveground attributes, as they responded more strongly to our treatments than those belowground. Our results are relevant for the restoration of Mediterranean degraded ecosystems, and show that tree thinning in overstocked pine stands, combined with the plantation of resprouter species, may not only reduce fire risks and accelerate post-fire succession but also enhance the supply of multiple ecosystem services in the long run.This research was funded by the FUME project funded by the European Seventh Programme Framework (Grant number 24388), HYDROMED project funded by the Spanish Ministry of Science and Innovation (Subprojects BLUEWATER PID2019-111332RB-C21 and INERTIA PID2019-111332RB-C22), IMAGINA (PROMETEO/2019/110), and the FIRE-SCENARIO (GV-2020-160) projects funded by the Generalitat Valenciana. A.M. is supported by the scholarship of Generalitat Valenciana-European Social Fund (ACIF-2018-194). S.S. was supported by the Spanish Government under a Ramón y Cajal contract (RYC-2016-20604)

Secondary succession, biotic interactions and the functioning of roadside communities: plant-soil interactions matter more than plant-plant interactions

Los estudios a largo plazo de ecosistemas degradados en recuperación son raros, especialmente aquellos que miran más allá de la composición de especies vegetales. Aquí evaluamos cambios en las interacciones planta-planta y planta-suelo en una cronosecuencia de 20 años en taludes de carretera. Además, cuantificamos las asociaciones entre éstas interacciones y atributos fundamentales del ecosistema (fertilidad del suelo, reciclaje de nutrientes, resistencia a la erosión, composición de plantas y microorganismos). Las interacciones entre plantas no variaron de forma significativa entre taludes de 0-2, de 7-9 o de más de 20 años, pero sí lo hicieron las interacciones planta-suelo. Estas relaciones eran negativas en los taludes más jóvenes y positiva en los más maduros (> 7 años). Cuatro de las 15 variables analizadas (cobertura vegetal, contenido en P, coeficiente C/N y composición de los microorganismos del suelo) llegaron a niveles semejantes a los del ecosistema de referencia. Otras variables (composición y riqueza de plantas, biomasa radicular, reciclado de materia orgánica), incrementaron de forma notable, sobretodo en el periodo de 0-2 a 7-9 años, aunque sin llegar a los niveles de referencia. Las interacciones planta-suelo fueron tan importantes como la edad para determinar la similaridad en la composición microbiana (con respecto a la del ecosistema de referencia), la resistencia a la erosión y el reciclado de C, mientras que las interacciones planta-planta tuvieron una importancia menor para estos atributos. Nuestro trabajo ilustra la variación temporal de componentes fundamentales del ecosistema. También mostramos la importancia de las interacciones planta-suelo para determinar el funcionamiento de comunidades asociadas a taludes de carretera.Long-term assessments of the recovery of degraded ecosystems are scarce, and even more those focusing on attributes beyond plant species composition. Here, we evaluate changes in planta-plant and plant-soil interactions across a 20+ years-chronosequence in motorway slopes. Furthermore, we quantify the associations between these biotic interactions and changes in important ecosystem attributes (soil fertility, nutrient cycling, erodibility and plant and microbe composition). Plant-plant interactions did not change significantly between slopes 0-2, 7-9 or >20 years old, but plant-soil interactions did. Plant-soil interactions were negative in young slopes and shift to positive from 7 years onwards. Four of the 15 variables analysed (plant cover, P content, C/N ratio and the composition of soil microbes) reached levels comparable to those of the reference ecosystem. Other variables (plant composition and richness, root biomass, organic matter cycling) increased substantially between the 0-2 years and the 7-9 years period, although did not reach the same level as in the reference ecosystem. Plant-soil interactions were as important as slope age to determine the similarity (regarding the reference) in soil microbe composition, erosion resistance and C cycling, while planta-plant interactions were of little importance for those attributes. Our work illustrates how fundamental attributes of the ecosystem change through time. We also show the importance of plant-soil interactions to determine the functioning of plant communities linked to motorway slopes

El uso de parches artificiales mejora el rendimiento de una repoblación de Rhamnus lycioides en medio semiárido

En el presente estudio se evalúa el efecto de la formación de parches artificiales que contribuyan a regenerar la dinámica fuente-sumidero característica de ecosistemas semiáridos. Para ello se ha evaluado el efecto de pilas de ramas de pino sobre brinzales introducidos de Rhamnus lycioides L., analizando la importancia relativa de la sombra y la captura de escorrentía superficial de estos parches en la respuesta de la vegetación. Estos parches redujeron de forma significativa la radiación PAR incidente, aumentando la supervivencia de los brinzales en más de un 30%, aunque no tuvieron un efecto significativo sobre su crecimiento o la retención de sedimentos. Los resultados obtenidos sugieren que las pilas de ramas pueden ser una buena herramienta en la restauración de estos medios, pudiendo mejorar procesos vitales para el ecosistema.Esta investigación ha sido financiada por el proyecto Life-ECOQUARRY (LIFE04 ENV/ES/000195), con la colaboración de CEMEX S.A

Multifunctionality debt in global drylands linked to past biome and climate

Past vegetation and climatic conditions are known to influence current biodiversity patterns. However, whether their legacy effects affect the provision of multiple ecosystem functions, that is, multifunctionality, remains largely unknown. Here we analyzed soil nutrient stocks and their transformation rates in 236 drylands from six continents to evaluate the associations between current levels of multifunctionality and legacy effects of the Last Glacial Maximum (LGM) desert biome distribution and climate. We found that past desert distribution and temperature legacy, defined as increasing temperature from LGM, were negatively correlated with contemporary multifunctionality even after accounting for predictors such as current climate, soil texture, plant species richness, and site topography. Ecosystems that have been deserts since the LGM had up to 30% lower contemporary multifunctionality compared with those that were nondeserts during the LGM. In addition, ecosystems that experienced higher warming rates since the LGM had lower contemporary multifunctionality than those suffering lower warming rates, with a ~9% reduction per extra degree Celsius. Past desert distribution and temperature legacies had direct negative effects, while temperature legacy also had indirect (via soil sand content) negative effects on multifunctionality. Our results indicate that past biome and climatic conditions have left a strong “functionality debt” in global drylands. They also suggest that ongoing warming and expansion of desert areas may leave a strong fingerprint in the future functioning of dryland ecosystems worldwide that needs to be considered when establishing management actions aiming to combat land degradation and desertification.China Scholarship Council; National Natural Science Foundation of China, Grant/Award Number: 31570467; Horizon 2020 Framework Programme, Grant/Award Number: 702057, 242658 and 647038; Ramón y Cajal contract, Grant/Award Number: RYC-2016-20604; European Research Counci

Plant attributes interact with fungal pathogens and nitrogen addition to drive soil enzymatic activities and their temporal variation

1. Nitrogen enrichment can alter soil communities and their functioning directly, via changes in nutrient availability and stoichiometry, or indirectly, by changing plant communities or the abundance of consumers. However, most studies have only focused on one of these potential drivers and we know little about the relative importance of the different mechanisms (changes in nutrient availability, in plant diversity or functional composition or in consumer abundance) by which nitrogen enrichment affects soil functioning. In addition, soil functions could vary dramatically between seasons; however, they are typically measured only once during the peak growing season. We therefore know little about the drivers of intra-annual stability in soil functioning. 2. In this study, we measured activities of β-glucosidase and acid phosphatase, two extracellular enzymes that indicate soil functioning. We did so in a large grassland experiment which tested the effects, and relative importance, of nitrogen enrichment, plant functional composition and diversity, and foliar pathogen presence (controlled by fungicide) on soil functioning. We measured the activity of the two enzymes across seasons and years to assess the stability and temporal dynamics of soil functioning. 3. Overall β-glucosidase activity was slightly increased by nitrogen enrichment over time but did not respond to the other experimental treatments. Conversely, plant functional diversity and interactions between plant attributes and fungicide application were important drivers of mean acid phosphatase activity. The temporal stability of both soil enzymes was differently affected by two facets of plant diversity: species richness increased temporal stability and functional diversity decreased it; however, these effects were dampened when nitrogen and fungicide were added. 4. The fungicide effects on soil enzyme activities suggest that foliar pathogens can also affect below-ground processes and the interacting effect of fungicide and plant diversity suggests that these plant enemies can modulate the relationship between plant diversity and ecosystem functioning. The contrasting effects of our treatments on the mean versus stability of soil enzyme activities clearly show the need to consider temporal dynamics in below-ground processes, to better understand the responses of soil microbes to environmental changes such as nutrient enrichment.This work is part of the PaNDiv grassland experiment, which was funded by the Swiss National Science Foundation (Project Number: 310030_185260). We thank the Ramon y Cajal programme (RyC-2016-20604) founded by Spanish Ministry of Science, the Swedish Research Council for Sustainable Development for funding NIM (FORMAS 2018-00748), the Swiss National Science Foundation for funding AK (P3P3PA_160992) and the Federal Commission for Scholarships for foreign students (FCS) for funding TZN

Environmental correlates of species rank − abundance distributions in global drylands

Theoretical models predict lognormal species abundance distributions (SADs) in stable and productive environments, with log-series SADs in less stable, dispersal driven communities. We studied patterns of relative species abundances of perennial vascular plants in global dryland communities to: (i) assess the influence of climatic and soil characteristics on the observed SADs, (ii) infer how environmental variability influences relative abundances, and (iii) evaluate how colonisation dynamics and environmental filters shape abundance distributions. We fitted lognormal and log-series SADs to 91 sites containing at least 15 species of perennial vascular plants. The dependence of species relative abundances on soil and climate variables was assessed using general linear models. Irrespective of habitat type and latitude, the majority of the SADs (70.3%) were best described by a lognormal distribution. Lognormal SADs were associated with low annual precipitation, higher aridity, high soil carbon content, and higher variability of climate variables and soil nitrate. Our results do not corroborate models predicting the prevalence of log-series SADs in dryland communities. As lognormal SADs were particularly associated with sites with drier conditions and a higher environmental variability, we reject models linking lognormality to environmental stability and high productivity conditions. Instead our results point to the prevalence of lognormal SADs in heterogeneous environments, allowing for more evenly distributed plant communities, or in stressful ecosystems, which are generally shaped by strong habitat filters and limited colonisation. This suggests that drylands may be resilient to environmental changes because the many species with intermediate relative abundances could take over ecosystem functioning if the environment becomes suboptimal for dominant species

Matrix models for quantifying competitive intransitivity from species abundance data

In a network of competing species, a competitive intransitivity occurs when the ranking of competitive abilities does not follow a linear hierarchy (A \u3e B \u3e C but C \u3e A). A variety of mathematical models suggests that intransitive networks can prevent or slow down competitive exclusion and maintain biodiversity by enhancing species coexistence. However, it has been difficult to assess empirically the relative importance of intransitive competition because a large number of pairwise species competition experiments are needed to construct a competition matrix that is used to parameterize existing models. Here we introduce a statistical framework for evaluating the contribution of intransitivity to community structure using species abundance matrices that are commonly generated from replicated sampling of species assemblages. We provide metrics and analytical methods for using abundance matrices to estimate species competition and patch transition matrices by using reverse-engineering and a colonization–competition model. These matrices provide complementary metrics to estimate the degree of intransitivity in the competition network of the sampled communities. Benchmark tests reveal that the proposed methods could successfully detect intransitive competition networks, even in the absence of direct measures of pairwise competitive strength. To illustrate the approach, we analyzed patterns of abundance and biomass of five species of necrophagous Diptera and eight species of their hymenopteran parasitoids that co-occur in beech forests in Germany. We found evidence for a strong competitive hierarchy within communities of flies and parasitoids. However, for parasitoids, there was a tendency towards increasing intransitivity in higher weight classes, which represented larger resource patches. These tests provide novel methods for empirically estimating the degree of intransitivity in competitive networks from observational datasets. They can be applied to experimental measures of pairwise species interactions, as well as to spatio-temporal samples of assemblages in homogenous environments or environmental gradients

Factores que determinan la riqueza de especies de aves en hábitats mediterráneos: el papel de las características locales y del paisaje

Los P.N. de Font Roja y Serra de Mariola albergan una gran diversidad de aves. Nuestro objetivo es conocer cómo la riqueza de aves responde a factores locales (uso del suelo, diversidad de hábitats y recursos) y del paisaje (diversidad, tamaño del hábitat). Detectamos 39 especies de aves diferentes, cuya riqueza se relacionó de forma positiva con la de plantas. El resto de factores determinaron la presencia de especies individuales, pero no la riqueza general.Els P.N. de Font Roja i Serra de Mariola alberguen una gran diversitat d´aus. Volem conèixer com aquesta diversitat respon a factors locals (ús del sòl, varietat d’hàbitats i recursos) i de paisatge (diversitat, mida de l’hàbitat). Detectem 39 espècies d’aus, la riquesa de les quals és relaciona de manera positiva amb la riquesa de plantes. La resta de factors determina la presencia d’espècies individuals, però no la riquesa general.Font Roja and Serra de Mariola natural park are home for a great diversity of birds. We studied how such diversity responds to different local (land use, variety of habitats and resources) and landscape (diversity and size). We detected 39 species of birds, the richness of which was positively related to plants richness. The rest of factors affected the presence of individual species but had no effect on their overall richness.Esta investigación ha sido financiada por el Ministerio de Ciencia, Innovación y Universidades, del Gobierno de España, mediante el proyecto I+d+i «Retos investigación» del programa estatal de I+d+i orientada a los retos de la sociedad “Identificando las consecuencias funcionales de cambios en la biodiversidad a varias escalas espaciales” (FOBIASS; RTI2018-098895-a-i00) y la ayuda Ramón y Cajal (RyC-2016-20604)

Species interactions and random dispersal rather than habitat filtering drive community assembly during early plant succession

Theory on plant succession predicts a temporal increase in the complexity of spatial community structure and of competitive interactions: initially random occurrences of early colonising species shift towards spatially and competitively structured plant associations in later successional stages. Here we use long-term data on early plant succession in a German post mining area to disentangle the importance of random colonisation, habitat filtering, and competition on the temporal and spatial development of plant community structure. We used species co-occurrence analysis and a recently developed method for assessing competitive strength and hierarchies (transitive versus intransitive competitive orders) in multispecies communities. We found that species turnover decreased through time within interaction neighbourhoods, but increased through time outside interaction neighbourhoods. Successional change did not lead to modular community structure. After accounting for species richness effects, the strength of competitive interactions and the proportion of transitive competitive hierarchies increased through time. Although effects of habitat filtering were weak, random colonization and subsequent competitive interactions had strong effects on community structure. Because competitive strength and transitivity were poorly correlated with soil characteristics, there was little evidence for context dependent competitive strength associated with intransitive competitive hierarchies