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Animal burrowing activity affects soil texture, bulk density, soil water content, and redistribution of nutrients. All of these parameters in turn influence sediment redistribution, which shapes the earth's surface. Hence it is important to include bioturbation into hillslope sediment transport models. However, the inclusion of burrowing animals into hillslope-wide models has thus far been limited and has largely omitted vertebrate bioturbators, which can be major agents of bioturbation, especially in drier areas. Here, we included vertebrate bioturbator burrows into a semi-empirical Morgan-Morgan-Finney soil erosion model to allow a general approach to the assessment of the impacts of bioturbation on sediment redistribution within four sites along the Chilean climate gradient. For this, we predicted the distribution of burrows by applying machine learning techniques in combination with remotely sensed data in the hillslope catchment. Then, we adjusted the spatial model parameters at predicted burrow locations based on field and laboratory measurements. We validated the model using field sediment fences. We estimated the impact of bioturbator burrows on surface processes. Lastly, we analyzed how the impact of bioturbation on sediment redistribution depends on the burrow structure, climate, topography, and adjacent vegetation. Including bioturbation greatly increased model performance and demonstrates the overall importance of vertebrate bioturbators in enhancing both sediment erosion and accumulation along hillslopes, though this impact is clearly staggered according to climatic conditions. Burrowing vertebrates increased sediment accumulation by 137.8ĝ€¯%ĝ€¯±ĝ€¯16.4ĝ€¯% in the arid zone (3.53ĝ€¯kgĝ€¯ha-1ĝ€¯yr-1 vs. 48.79ĝ€¯kgĝ€¯ha-1ĝ€¯yr-1), sediment erosion by 6.5ĝ€¯%ĝ€¯±ĝ€¯0.7ĝ€¯% in the semi-arid zone (129.16ĝ€¯kgĝ€¯ha-1ĝ€¯yr-1 vs. 122.05ĝ€¯kgĝ€¯ha-1ĝ€¯yr-1), and sediment erosion by 15.6ĝ€¯%ĝ€¯±ĝ€¯0.3ĝ€¯% in the Mediterranean zone (4602.69ĝ€¯kgĝ€¯ha-1ĝ€¯yr-1 vs.

Altres ajuts: This work utilised the network of dendrometer observations established by the COST Action network STReESS (grant FP1106), Heatwaves exert disproportionately strong and sometimes irreversible impacts on forest ecosystems. These impacts remain poorly understood at the tree and species level and across large spatial scales. Here, we investigate the effects of the record-breaking 2018 European heatwave on tree growth and tree water status using a collection of high-temporal resolution dendrometer data from 21 species across 53 sites. Relative to the two preceding years, annual stem growth was not consistently reduced by the 2018 heatwave but stems experienced twice the temporary shrinkage due to depletion of water reserves. Conifer species were less capable of rehydrating overnight than broadleaves across gradients of soil and atmospheric drought, suggesting less resilience toward transient stress. In particular, Norway spruce and Scots pine experienced extensive stem dehydration. Our high-resolution dendrometer network was suitable to disentangle the effects of a severe heatwave on tree growth and desiccation at large-spatial scales in situ, and provided insights on which species may be more vulnerable to climate extremes.

Burrowing animals influence surface microtopography and hillslope sediment redistribution, but changes often remain undetected due to a lack of automated high-resolution field monitoring techniques. In this study, we present a new approach to quantify microtopographic variations and surface changes caused by burrowing animals and rainfall-driven erosional processes applied to remote field plots in arid and Mediterranean climate regions in Chile. We compared the mass balance of redistributed sediment between burrow and burrow-embedded area, quantified the cumulative sediment redistribution caused by animals and rainfall, and upscaled the results to a hillslope scale. The newly developed instrument, a time-of-flight camera, showed a very good detection accuracy. The animal-caused cumulative sediment excavation was 14.6 cm3 cm-2 yr-1 in the Mediterranean climate zone and 16.4 cm3 cm-2 yr-1 in the arid climate zone. The rainfall-related cumulative sediment erosion within burrows was higher (10.4 cm3 cm-2 yr-1) in the Mediterranean climate zone than the arid climate zone (1.4 cm3 cm-2 yr-1). Daily sediment redistribution during rainfall within burrow areas was up to 350 %(40 %) higher in the Mediterranean (arid) zone compared to burrow-embedded areas and much higher than previously reported in studies that were not based on continuous microtopographic monitoring. A total of 38 % of the sediment eroding from burrows accumulated within the burrow entrance, while 62 % was incorporated into hillslope sediment flux, which exceeds previous estimations 2-fold. On average, animals burrowed between 1.2-2.3 times a month, and the burrowing intensity increased after rainfall. This revealed a newly detected feedback mechanism between rainfall, erosion, and animal burrowing activity, likely leading to an underestimation of animal-triggered hillslope sediment flux in wetter climates. Our findings hence show that the rate of sediment redistribution due to animal burrowing is dependent

Heatwaves exert disproportionately strong and sometimes irreversible impacts on forest ecosystems. These impacts remain poorly understood at the tree and species level and across large spatial scales. Here, we investigate the effects of the record-breaking 2018 European heatwave on tree growth and tree water status using a collection of high-temporal resolution dendrometer data from 21 species across 53 sites. Relative to the two preceding years, annual stem growth was not consistently reduced by the 2018 heatwave but stems experienced twice the temporary shrinkage due to depletion of water reserves. Conifer species were less capable of rehydrating overnight than broadleaves across gradients of soil and atmospheric drought, suggesting less resilience toward transient stress. In particular, Norway spruce and Scots pine experienced extensive stem dehydration. Our high-resolution dendrometer network was suitable to disentangle the effects of a severe heatwave on tree growth and desiccation at large-spatial scales in situ, and provided insights on which species may be more vulnerable to climate extremes.

Bioturbators shape their environment with considerable consequences for ecosystem processes. However, both the composition and the impact of bioturbator communities may change along climatic gradients. For burrowing animals, their abundance and composition depend on climatic and other abiotic components, with ants and mammals dominating in arid and semiarid areas, and earthworms in humid areas. Moreover, the activity of burrowing animals is often positively associated with vegetation cover (biotic component). These observations highlight the need to understand the relative contributions of abiotic and biotic components in bioturbation in order to predict soil-shaping processes along broad climatic gradients. In this study, we estimated the activity of animal bioturbation by counting the density of holes and the quantity of bioturbation based on the volume of soil excavated by bioturbators along a gradient ranging from arid to humid in Chile. We distinguished between invertebrates and vertebrates. Overall, hole density (no/ 100 m2) decreased from arid (raw mean and standard deviation for invertebrates: 14 ± 7.8, vertebrates: 2.8 ± 2.9) to humid (invertebrates: 2.8 ± 3.1, vertebrates: 2.2 ± 2.1) environments. However, excavated soil volume did not follow the same clear geographic trend and was 300-fold larger for vertebrates than for invertebrates. The relationship between bioturbating invertebrates and vegetation cover was consistently negative whereas for vertebrates both, positive and negative relationships were determined along the gradient. Our study demonstrates complex relationships between climate, vegetation and the contribution of bioturbating invertebrates and vertebrates, which will be reflected in their impact on ecosystem functions.