Clumped or regular? the role of thinning pattern on pine growth and soil water content in dense Aleppo pine post-fire stands

The development of silvicultural practices that seek to promote structural heterogeneity is increasingly demanded. This work investigates the effect of thinning spatial pattern on the response to pre-commercial thinning of dense Aleppo pine post-fire stands. On three replicated experimental sites in SE Spain, we applied the following treatments: 600 trees/ha, regular thinning pattern (600R), with residual trees evenly spaced; 600 trees/ha, aggregated thinning pattern (600A), with residual pines arranged in clumps of ∽25 trees with a local within-clump density of 2500 trees/ha; and control treatment, with no thinning applied (> 20,000 trees/ha). We assessed treatment effects on pine growth, size-growth relationships, soil water content, and understory vegetation over the first three years after thinning application. Both regular and aggregated thinning pattern similarly increased pine radial growth. In general, dbh growth rates in response to thinning were faster for smaller trees than for larger trees. The growth rate of pine height was higher for 600R and control than for 600A, indicating a positive effect on height of both low and very high pine densities. We found a near-term positive effect of aggregated pattern on water availability at the stand level, mostly resulting from enhanced soil water content in the canopy gaps. For both thinning patterns, the recovery of understory vegetation was dominated by resprouter species. This study highlights the potential of aggregated thinning patterns to enhance the complexity and heterogeneity of the pine stands without compromising pine growth, which could be of great use to managing pine forests in Mediterranean areas.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This study was supported by the Spanish Ministry of Science and Innovation (http://www.ciencia.gob.es/) through the projects FEEDBACK (CGL2011-30515-C02-01) and DRYEX2 (CGL2017-89804-R)

Drone-based assessment of microsite-scale hydrological processes promoted by restoration actions in early post-mining ecological restoration stages

A successful choice of post-mining restoration activities in dry climates may depend on relevant features related to topographic characteristics, hydrological processes and vegetation development, which will determine functional recovery in these ecosystems. The combination of different restoration techniques to reestablish vegetation, such as sowing and plantation, implies the interspersion of bare-soil areas with vegetated areas in early plant development stages, which may result in an associated mosaic of hydrologic functioning. In this study, we conducted a drone-based assessment to disentangle the role played by microsite-scale hydrological processes (i.e., planting hole slope, sink volume capacity, individual catchment area, Flow Length Index) promoted by restoration actions in soil protection and vegetation development on the hillside scale. Based on two contrasting restoration scenarios (Steep hillside and Smooth hillside), the different applied restoration treatments conditioned the microtopographic processes on the planting hole scale and, therefore, resource redistribution. The main results showed higher planting hole functionality on the smooth hillsides than on steep hillside, which resulted in greater water availability and bigger vegetation patches. By addressing the role of hydrological processes on the microsite scale, our study contributes substantially to prior knowledge on the relevant factors for ecosystem development and post-mining restoration success. It also demonstrates that high-resolution drone images can be a very useful tool for monitoring restoration actions, especially in large, inaccessible and unstable restored areas.The study was funded by the LIFE TECMINE Project (LIFE16 ENV/ES/000159) from the European Programme for the Environment and Climate Action (2014–2020)*. L.M. was supported by the Spanish MICINN (PTA2019-018094). The CEAM foundation is funded by the Generalitat Valenciana

Innovative Techniques for Landscape Recovery after Clay Mining under Mediterranean Conditions

Open-pit mining results in profound modifications at different environmental scales that may persist for very long time periods, or even indefinitely. Considerable research efforts in mine reclamation strategies have been made, although reclamation failures are still common. In dry climates, such as in the Mediterranean Basin, successful actions may depend on features related to proper species selection and restoration techniques, which may substantially contribute to provide substrate stability and facilitate the regeneration of the main ecological processes. In this context, we developed the TECMINE case-study aimed to evaluate the feasibility and suitability of innovative restoration practices applied to clay-mine reclamation under Mediterranean conditions. The restoration strategy was designed at the landscape level with two main approaches: the recovery of natural geomorphology shapes and ecological restoration, including vegetation recovery and soil quality, based on proper reference ecosystems. After the geomorphological land remodeling, a combination of several innovative restoration techniques was implemented to reclaim plant communities and ecosystem functioning. These techniques involved: (i) accurate species selection according to microhabitat characteristics; (ii) high-quality plant production; (iii) surface remodeling to improve substrate stabilization; and (iv) implementing rainfall collection to enhance resources availability, soil fertility improvement and the amelioration of abiotic conditions for seedlings. Finally, we developed a monitoring program to assess the success of the implemented restoration techniques over time. The application of these innovative techniques has reported interesting results and represents a step forward in the improvement of mine restoration under Mediterranean climate.The study was funded by the LIFE TECMINE Project (LIFE16 ENV/ES/000159) from the European Programme for the Environment and Climate Action (2014–2020)*. L.M. was supported by the Spanish MICINN (PTA2019-018094). The CEAM foundation is funded by the Generalitat Valenciana

Seguimiento del estado de la vegetación en función de las precipitaciones mediante el uso de índices de vegetación y métricas de fenología de superficie (LSP) en el Parque Natural del Carrascal de la Font Roja

En un contexto de cambio climático el presente trabajo trata de abordar la respuesta de la vegetación a las precipitaciones mediante el análisis del el índice de vegetación de diferencia normalizada (NDVI) y las métricas de fenología de superficie (LPS, Land Surface Phenology) en el Parque Natural del Carrascal de la Font Roja (FR) para el periodo 2000-2017. Los resultados muestran una tendencia positiva en los valores medios anuales del NDVI en el periodo de estudio con un cambio negativo a partir del 2011 como respuesta al descenso de las precipitaciones en estos últimos años. La longitud media de la estación de crecimiento (LOS) en el Parque Natural es del orden de 174.7 ± 21.4 días mostrando una tendencia negativa significativa al 10% lo que indica un acortamiento de la LOS debido a un atraso en el inicio de la estación (SOS) pero principalmente a un adelantamiento del final de la estación (EOS) como respuesta a una disminución en las precipitaciones de primavera y en particular las de abril-mayo.En un context de canvi climàtic el present treball tracta d’abordar la resposta de la vegetació a les precipitacions mitjançant l’anàlisi de l’índex de vegetació de diferència normalitzada (NDVI) i les mètriques de fenologia de superficie (LPS, Land Surface Phenology) al Parc Natural del Carrascal de la Font Roja (FR) pel període 2000-2017. Els resultats mostren una tendència positiva en els valors mitjans anuals del NDVI al període d’estudi amb un canvi negatiu a partir del 2011 com a resposta al descens de les precipitacions en aquests últims anys. La longitud mitjana de l’estació de creixement (LOS) al Parc Natural és de l’orde de 174.7 ± 21.4 dies mostrant una tendència negativa significativa al 10%, la qual cosa indica un acurtament de la LOS degut a un retard de l’inici de l’estació (SOS) però principalment, per un avançament del final de l’estació (EOS) com a resposta d’una disminució en les precipitacions de primavera i en particular les de l’abril-maig.In the context of climate change this work aims to analyze the vegetation response to precipitations using the normalized difference vegetation index (NDVI) and land surface phenology (LSP) metrics in the Font Roja Natural Parc (FR) over the 2000-2017 period. The results show a positive trend on mean annual NDVI values over the study period; however, a negative change is observed since 2011 as response to precipitation decrease during the last years. The mean growing season length (LOS) in the Natural Parc is about 174.7 ± 21.4 days showing a significant negative trend at 10% which indicates a shortening of the LOS due to a delay in the season start (SOS) but particularly due to earlier end of season (EOS) as a consequence of the decrease of spring precipitation and particularly April-May rainfall.Este trabajo se ha realizado dentro del marco del proyecto ALTERACLIM (CGL2015-69773-C2-1) financiado por el Ministerio de Economía, Industria y Competitividad

Disentangling the independent effects of vegetation cover and pattern on runoff and sediment yield in dryland systems – Uncovering processes through mimicked plant patches

There is strong empirical evidence on the importance of the spatial pattern of vegetation in dryland hydrologic and geomorphologic dynamics. However, changes in vegetation cover and spatial pattern are often linked, making it difficult to disentangle and assess their independent hydro-geomorphologic roles. We used synthetic sponges placed on the soil surface to mimic the aboveground structure of vegetation patches, and manipulated patch cover and pattern as well as the sink capacity of the patches on a set of 24 (2 × 1 m) runoff plots. Combining natural-rainfall and simulated-rainfall experiments, we aimed to test that (1) both vegetation cover and pattern independently control runoff and sediment yield; (2) for any given cover, coarsening the vegetation pattern entails increasing runoff and sediment yield; and (3) pattern effect is mostly exerted by modulating the source-sink dynamics of the system. We found that increasing either patch cover or patch density decreased runoff and sediment yields from natural rainfalls, yet the effect of patch density largely disappeared when the effect of the co-varying patch cover was removed. Simulated-rainfall experiments on plots with equal medium-low patch cover showed however that coarser patterns (lower patch density; higher patch size) increased runoff coefficients and reduced time to runoff as compared with finer patterns. The effect of patch density was particularly clear when the sink function of vegetation patches was also mimicked. Rainfall interception and direct soil protection proved to be critical mechanisms underlying the effects of patch cover, yet they barely contributed to the effects of patch pattern. The control of overland flow by patch pattern was exerted through changes in the level of runoff disruption. However, physical obstructions to runoff hardly reduced runoff unless coupled to mimicked soil sinks. Overall this work demonstrates the independent effects of patch cover and pattern on the hydro-geomorphologic functioning of patchy landscapes, with patch cover being the primary hydrologic control factor and patch pattern exhibiting its full potential for low and medium low patch cover values. Our findings provide useful information for modelling and understanding dryland vegetation dynamics, and for designing management and restoration measures that take into account the critical role played by source-sink dynamics and hydrological connectivity in dryland landscapes.This work was supported by the Spanish Ministry of Science and Innovation (DRYEX2 project; grant number CGL 2017-89804-R), and the European Union's Seventh Framework Programme (CASCADE project; grant number GA283068)

Disentangling the independent effects of vegetation cover and pattern on runoff and sediment yield in dryland systems – Uncovering processes through mimicked plant patches

There is strong empirical evidence on the importance of the spatial pattern of vegetation in dryland hydrologic and geomorphologic dynamics. However, changes in vegetation cover and spatial pattern are often linked, making it difficult to disentangle and assess their independent hydro-geomorphologic roles. We used synthetic sponges placed on the soil surface to mimic the aboveground structure of vegetation patches, and manipulated patch cover and pattern as well as the sink capacity of the patches on a set of 24 (2 × 1 m) runoff plots. Combining natural-rainfall and simulated-rainfall experiments, we aimed to test that (1) both vegetation cover and pattern independently control runoff and sediment yield; (2) for any given cover, coarsening the vegetation pattern entails increasing runoff and sediment yield; and (3) pattern effect is mostly exerted by modulating the source-sink dynamics of the system. We found that increasing either patch cover or patch density decreased runoff and sediment yields from natural rainfalls, yet the effect of patch density largely disappeared when the effect of the co-varying patch cover was removed. Simulated-rainfall experiments on plots with equal medium-low patch cover showed however that coarser patterns (lower patch density; higher patch size) increased runoff coefficients and reduced time to runoff as compared with finer patterns. The effect of patch density was particularly clear when the sink function of vegetation patches was also mimicked. Rainfall interception and direct soil protection proved to be critical mechanisms underlying the effects of patch cover, yet they barely contributed to the effects of patch pattern. The control of overland flow by patch pattern was exerted through changes in the level of runoff disruption. However, physical obstructions to runoff hardly reduced runoff unless coupled to mimicked soil sinks. Overall this work demonstrates the independent effects of patch cover and pattern on the hydro-geomorphologic functioning of patchy landscapes, with patch cover being the primary hydrologic control factor and patch pattern exhibiting its full potential for low and medium low patch cover values. Our findings provide useful information for modelling and understanding dryland vegetation dynamics, and for designing management and restoration measures that take into account the critical role played by source-sink dynamics and hydrological connectivity in dryland landscapes

Moderate pine cover maximizes 10-year survival and growth in late-successional species of contrasting functional strategies

Monospecific pine forests are widespread due to extensive afforestation efforts and natural colonization of abandoned croplands in the Mediterranean Basin. It was originally thought that pines would facilitate the natural colonization of native late-successional resprouter species (e.g., hardwoods), but these species can be compromised if competition with pines outweighs their facilitative effect on these hardwood species. Managing the density or canopy cover of these widespread pine forests can potentially provide some “optimum” balance between facilitation and competition to maximize success in the introduction of late successional species while maintaining a tree stratum. We tested the response (survival and growth across 10 years) of six resprouter species covering a wide range of plant functional strategies, from drought-tolerant sclerophyllous shrubs and trees to malacophyllous drought-sensitive trees, across an experimental gradient of Aleppo pine canopy cover. Seedling performance varied according to the functional strategy, pine cover and time. High pine cover generally enhanced seedling survival, whereas moderate pine cover generally enhanced seedling growth, although this response was modulated by the functional strategy of the seedling species. Interactions between pines and seedlings were only detectable 2–3 years after plantation, increasing in intensity with time. The latter highlights the need of medium to long-term studies to evaluate plant-plant interactions in these water-limited environments with slow successional trajectories. Our results could be attributed to the shade tolerance of most of the introduced trees, combined with their low tolerance to the combination of high sunlight radiation and drought. We found an optimal pine cover of ca. 50% (equivalent to 300–400 trees/ha) in which both survival and growth of late successional species can be maximized, which help to select best locations for more efficient reforestation programs and set a threshold value to decide whether or not to perform tree thinning to enhance ecosystem diversity and, subsequently, resilience.The study was funded by the FUME (EU FP7-Environment, GA. 243888), SURVIVE-2 (CGL2015-69773-C2-2-P MINECO/FEDER) and INERTIA (PID2019-111332RB-C22) projects, from the Spanish Government and IMAGINA project (PROMETEU/2019/110) from Generalitat Valenciana. L.M. was supported by the Spanish MICINN (PTA2019-018094). S.S. was supported by the Ramón y Cajal fellowship (RYC-2016-20604) and the FOBIASS project (RTI2018-098895-A-100), both from the Ministry of Science and Innovation. CEAM foundation is funded by Generalitat Valenciana

Disentangling the independent effects of vegetation cover and pattern on runoff and sediment yield in dryland systems – Uncovering processes through mimicked plant patches

There is strong empirical evidence on the importance of the spatial pattern of vegetation in dryland hydrologic and geomorphologic dynamics. However, changes in vegetation cover and spatial pattern are often linked, making it difficult to disentangle and assess their independent hydro-geomorphologic roles. We used synthetic sponges placed on the soil surface to mimic the aboveground structure of vegetation patches, and manipulated patch cover and pattern as well as the sink capacity of the patches on a set of 24 (2 × 1 m) runoff plots. Combining natural-rainfall and simulated-rainfall experiments, we aimed to test that (1) both vegetation cover and pattern independently control runoff and sediment yield; (2) for any given cover, coarsening the vegetation pattern entails increasing runoff and sediment yield; and (3) pattern effect is mostly exerted by modulating the source-sink dynamics of the system. We found that increasing either patch cover or patch density decreased runoff and sediment yields from natural rainfalls, yet the effect of patch density largely disappeared when the effect of the co-varying patch cover was removed. Simulated-rainfall experiments on plots with equal medium-low patch cover showed however that coarser patterns (lower patch density; higher patch size) increased runoff coefficients and reduced time to runoff as compared with finer patterns. The effect of patch density was particularly clear when the sink function of vegetation patches was also mimicked. Rainfall interception and direct soil protection proved to be critical mechanisms underlying the effects of patch cover, yet they barely contributed to the effects of patch pattern. The control of overland flow by patch pattern was exerted through changes in the level of runoff disruption. However, physical obstructions to runoff hardly reduced runoff unless coupled to mimicked soil sinks. Overall this work demonstrates the independent effects of patch cover and pattern on the hydro-geomorphologic functioning of patchy landscapes, with patch cover being the primary hydrologic control factor and patch pattern exhibiting its full potential for low and medium low patch cover values. Our findings provide useful information for modelling and understanding dryland vegetation dynamics, and for designing management and restoration measures that take into account the critical role played by source-sink dynamics and hydrological connectivity in dryland landscapes