The Aranjuez Experimental Station: The Maestre Lab´s natural laboratory



An important part of our field research is carried out in the Aranjuez Experimental Station (AES), located in the vicinity of Aranjuez, 55 km south of Madrid.  With the support of an Early Career Project Grant from the British Ecological Society, and of some start-up funds I get from Rey Juan Carlos University (URJC) and the Spanish Ministry of Education and Science, we started working in the AES in the fall of 2006, and have been continuously working there since then. The site has hosted more than a dozen of experiments from our lab and other colleagues from the Biodiversity and Conservation Area of the Rey Juan Carlos University, and has supported seven PhD Theses so far, both from the Maestre lab (Santiago Soliveres, Andrea Castillo-Monroy, Manuel Delgado-Baquerizo, Cristina Escolar, and Miguel Berdugo) and from other groups that are collaborating with us (Guadalupe León from CEBAS-CSIC and Mónica Ladrón de Guevara, from EEZA-CSIC). Since 2010, all our research activities at the AES have been funded by the Starting Grant BIOCOM, awarded to Fernando T. Maestre by the European Research Council. The research carried out at the AES has been derived in 15 articles published in international peer-reviewed scientific journals (see references below), and is also very important for the teaching and outreaching activities carried out by the lab. The AES is visited every year by students from a Master in Restoration Ecology, who learn about the research we carry out there and use also the AES for their MsC. theses, by national and international visitors coming to the Maestre lab (click here for some pictures), and by members of local NGOs interested in nature conservation.

The AES is fundamental for us as a research group, as it is our main research site and a fantastic natural laboratory to study the ecology of drylands. As a small homage and recognition to the AES and to the people that has been working there over the last decade, in this blog post we describe the main characteristics of the AES, describe past/current experiments and synthesize some of the main results we have obtained from the research carried out there so far.

Description of the Aranjuez Experimental Station

The Aranjuez Experimental Station (AES) is located in the centre of the Iberian Peninsula (40º02’ N – 3º 32’W; 590 m a.s.l., Figure 1). It is part of the “Finca de Sotomayor”, a larger area historically devoted to host the Royal stable (“Caballerizas reales”) and in recent times to small game hunting and to the growth of grain crops typical from semi-arid Mediterranean areas. This land is owned by the Regional Government (Comunidad de Madrid), which has managed the site through a research institute devoted to agriculture, livestock and rural development (“Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario, IMIDRA)”. The AES is part of the European Union Natura 2000 network of protected areas, as it is included within the Special Protection Areas for Birds “Carrizales y Sotos de Aranjuez” (ES 0000119) and the Site of Community Importance  “Vegas, Cuestas y Páramos del Sureste” (ES3110006).



Figure 1. Location of the Aranjuez Experimental Station and view of the plant and biological soil crust communities that dominate it. Source: Delgado-Baquerizo (2013).

The climate of the AES is Mediterranean semi-arid, with a mean annual temperature and rainfall of 15ºC and 349 mm, respectively (Aranjuez Meteorological Station, 40º02’ N – 3º 32’W; 540 m a.s.l.; average data from the 1983-1988 and 1997-2011 periods). The soil is derived from gypsum, and is classified as Xeric Haplogypsid. Perennial plant cover is below 40%, and is dominated by the tussock grass Stipa tenacissima L. (18% of total cover) and the N-fixing shrub Retama sphaerocarpa (L.) Boiss (6% of total cover). Other shrubs common at the AES are Helianthemum squamatum (L.) Dum. Cours and Lepidium subulatum L. The open areas between perennial plants are colonized by well-developed biological soil crusts (BSCs) dominated by lichens such as Diploschistes diacapsis (Ach.) Lumbsch, Squamarina lentigera (Weber) Poelt, and Fulgensia subbracteata, mosses such as Pleurochaete squarrosa (Brid.) Lindb., and Didymodon acutus (Brid.) K. Saito. (Figure 2; see Table 1 for a species checklist). Bare soil (i.e. areas that do not contain perennial vegetation nor well-developed BSC communities) and BSC-dominated areas cover approximately 28% and 32% of the AES, respectively.



Figure 2. Close-up view of the lichens dominating biological soil crusts at the Aranjuez Experimental Station: Diploschistes diacapsis, Fulgensia subbracteata and Psora decipiens (white, yellow and pink thalli, respectively). Photograph by Fernando T. Maestre. For additional BSC pictures from Aranjuez click here.


Table 1. Checklist and frequency (in %) of biological soil crust-forming lichens and mosses in the dominant microsites present at the Aranjuez Experimental Station (Figure 3). ST = Stipa tenacissima, RS = Retama sphaerocarpa L., BS = Bare soil; LC = low cover of biological soil crust (BSC), MC = Medium cover of BSC, and HC = high cover of BSC. Source: Castillo-Monroy et al. (2010).

 Species
ST
RS
LC
MC
HC
BS
 Pleurochaete squarrosa
100.0
73.3
0.0
0.0
6.7
6.7
Syntrichia papillosissima
33.3
33.3
0.0
0.0
0.0
0.0
Didymodon acutus
0.0
0.0
26.7
20.0
20.0
26.7
Tortula revolvens
0.0
13.3
26.7
46.7
46.7
13.3
Weissia sp.
6.7
6.7
0.0
0.0
0.0
0.0
Acarospora reagens
6.7
0.0
33.3
40.0
40.0
33.3
Buellia epipolium
0.0
0.0
13.3
13.3
13.3
0.0
Buellia zoharyi
0.0
0.0
0.0
0.0
6.7
0.0
Cladonia convoluta
46.7
6.7
6.7
6.7
13.3
0.0
Collema crispum
6.7
13.3
20.0
0.0
20.0
6.7
Diploschistes diacapsis
6.7
6.7
53.3
40.0
73.3
66.7
Endocarpon pusillum
0.0
0.0
6.7
0.0
0.0
0.0
Fulgensia subbracteata
0.0
6.7
66.7
53.3
73.3
53.3
Placidium pilosellum
0.0
6.7
0.0
0.0
20.0
0.0
Placidium squamulosum
0.0
0.0
20.0
0.0
6.7
0.0
Psora decipiens
0.0
0.0
46.7
46.7
60.0
13.3
Psora savizcii
0.0
0.0
20.0
33.3
13.3
0.0
Squamarina cartilaginea
0.0
0.0
0.0
0.0
6.7
0.0
Squamarina lentigera
6.7
6.7
46.7
60.0
66.7
46.7
 Toninia sedifolia
0.0
6.7
6.7
26.7
33.3
6.7

Research carried out at the Aranjuez Experimental Station

The research program of the Maestre lab at the AES focuses on three main topics: i) biological soil crusts and their effects on ecosystem structure and functioning, ii) effects of climate change on BSCs and on the ecosystem processes depending on them, and iv) plant-plant interactions.

Biological soil crusts and their effects on ecosystem structure and functioning

Biological soil crusts –communities dominated by lichens, mosses, bacteria and fungi that inhabit the first mm of the soil surface– are a prevalent biotic component of dryland ecosystems worldwide that have multiple ecosystem roles in semiarid ecosystems such as the AES (see Maestre et al. 2011 and Castillo-Monroy & Maestre 2011 for recent reviews; click here for pictures of the BSC present at the AES). A core goal of our research at the AES is to understand how dryland ecosystems function; therefore, if we aim to achieve this goal we need to understand what BSCs, a key community in these ecosystems, are doing! The study of the ecology of BSCs, and of their effects on ecosystem structure and functioning, has been one of the core research activities carried out at the AES by the Maestre lab during the last seven years. Using natural and manipulative field experiments, as well as laboratory experiments with soils/BSCs from the AES, our research activities have focused on understanding how BSCs affect the water, carbon (C) and nitrogen (N) cycles, and how BSCs interact among them and with plant and microbial communities.

We started our N cycle studies by evaluating temporal changes in the availability of N in the six most frequent microsites found at the AES (Castillo-Monroy et al. 2010): S. tenacissima tussocks (ST), Retama sphaerocarpa shrubs (RS), and open areas with very low (BS), low (LC) medium (MC) and high (HC) cover of well developed and lichen-dominated BSCs (Figure 3). Over a two-year period (2007-2008), the temporal dynamics of available N followed changes in soil moisture. Available NH4+-N did not differ between microsites, while available NO3--N was substantially higher in the RS than in any other microsite (Figure 4). No significant differences in the amount of available NO3--N were found between ST and BS microsites, but these microsites had more NO3--N than those dominated by BSCs (LC, MC and HC). We also determined the proportion of nitrate, ammonium and dissolved organic nitrogen (DON) was determined in all microsites (Delgado-Baquerizo et al. 2010). DON was the dominant N form for BS microsites, while nitrate was dominant under the canopy of Retama; these microsites contained the lowest and highest N availability, respectively. Under BSCs, DON was the dominant N form. These results highlight the importance of this biotic community as a modulator of the availability of N in semi-arid ecosystems. We have been continuing the collection these data, and right now we have over six years of N availability data that are being analyzed (we plan to have these results ready later in 2013).




Figure 3. View of the most abundant microsites present at the Aranjuez Experimental Station, showing the plastic rings we are using to monitor soil CO2 fluxes.  A = high biological soil crust (BSC) cover; B = medium BSC cover, C = low BSC cover, D = bare ground soil, E = Retama sphaerocarpa shrubs, and F = Stipa tenacissima tussocks. Source: Castillo-Monroy et al. (2011).


Figure 4. Changes in NH4+-N (A) and NO3--N (B) availability between January 2007 and December 2008. Data represent means ± SE (n = 12). Different letters indicate significant differences between microsites after repeated measures ANOVA (P < 0.05). ST = Stipa tenacissima tussocks; RS = Retama sphaerocarpa shrubs; BS = Bare soil; LC = low biological soil crust (BSC) cover; MC = medium BSC cover; and HC = high BSC cover. The absence of NO3-N data in summer 2008 was promoted by the lack of significant rainfall events during this period, which prevented the diffusion of NO3- to the resins and thus its measurement. Source: Castillo-Monroy et al. (2010).

We have also evaluated how perennial plants and BSCs affected small-scale spatial patterns of soil inorganic N (ammonium and nitrate) availability at the AES by using geostatistical methods (Delgado-Baquerizo et al. 2013a). The range of semivariograms for ammonium and nitrate, and the coefficient of variation of nitrate, were lower in BSC-dominated microsites than in plant-dominated microsites. These results suggest that BSCs modulate the small-scale spatial pattern of inorganic N, producing more homogeneous conditions for spatial distribution of inorganic N forms than microsites provided by plants.

Measurements of soil CO2 efflux (soil respiration) at the dominant microsites of the AES (Figure 3) have been carried out on a monthly-quaterly basis since November 2006. As part of the PhD of Andrea Castillo-Monroy (you can download it from here) we set up an experiment to study the contribution of BSCs to the amount of CO2 respired by the soil at the AES. The analyses of the data gathered between November 2006 and June 2010 (Castillo-Monroy et al. 2011) revealed that soil respiration rates did not differ among BSC-dominated microsites, but were significantly higher and lower than those found in bare ground areas and Stipa (ST) microsites, respectively. A model using soil temperature and soil moisture accounted for over 85% of the temporal variation in soil respiration throughout the studied period. Using this model, we estimated a range of 240.4-322.6 g C·m-2·yr-1 released by soil respiration at our study area. Vegetated (ST and Retama) and BSC-dominated microsites accounted for 37% and 42% of this amount, respectively (Figure 5). Our results indicate that BSC-dominated areas are the main contributor to the total C released by soil respiration at the AES, and therefore BSCs must be considered when estimating C budgets in drylands. These measurements are being continued, and right now we have a ~7 year soil respiration database that will be analyzed in the upcoming months.


Figure 5. Relative contribution of Retama sphaerocarpa (RS), Stipa tenacissima (ST), bare soil (BS) and biological soil crust-dominated (BSC) microsites to the total amount of carbon released by soil respiration throughout the study period, both in dry (D) and wet (W) seasons. Results in 2006 represent only data from November and December; those from 2010 are calculated using data from January to May.

We have also studied how BSCs impact different parts of the hydrological cycle. Since 2006 we are continuously monitoring surface soil moisture (0-5 cm depth) at the main microsites of the AES (Figure 3), and using this dataset Miguel Berdugo is analyzing how BSCs control the temporal dynamics of soil moisture (this is work in progress, so we do not have any results to show yet!). During a research visit done by David Eldridge in 2009, and with the collaboration of our post-doc at the time Matthew A. Bowker, we used a systems approach to examine the interactive effects of three engineers -Stipa, BSCs, and the European rabbit (Oryctolagus cuniculus)- on infiltration processes at the AES. We measured the early (sorptivity) and later (steady–state infiltration) stages of infiltration using disk permeameters, which allowed us to determine the relative effects of engineers on water flow through large macropores (see Eldridge et al. 2010 for details). We detected few effects under tension when flow was restricted to matrix pores, but under ponding, sorptivity and steady–state infiltration adjacent to Stipa tussocks were 2–3 times higher than in intact or rabbit–disturbed crusts (Eldridge et al. 2010). Structural Equation Modeling (SEM) showed that both Stipa and crust cover exerted substantial and equal positive effects on infiltration under ponding, while indirectly, rabbit disturbance negatively affected infiltration by reducing crust cover (Figure 6). Additional SEM analyses demonstrated that 1) Stipa primarily influenced crusts by reducing their richness, 2) rabbits exerted a small negative effect on BSC richness and 3) lichens were negatively, and mosses positively, correlated with a derived “infiltration” axis. The results of this experiment highlight the importance of BSCs as a key player in the maintenance of infiltration–runoff dynamics in Stipa grasslands, and demonstrate the modulating role played by rabbits through their surface disturbances.



Figure 6. Effects of three interacting ecosystem engineers (Stipa tenacissima, rabbits and biological soil crusts, BSCs) upon infiltration at the Aranjuez Experimental Station. a. Final structural equation model illustrating ecosystem engineer effects upon steady–state infiltration under ponding. Boxes represent variables measured in the study, and arrows represent influences exerted by one variable upon another. Path coefficients (ranging from 0–1, and related to the partial correlation coefficient) appear adjacent to arrows. Arrow width is scaled proportionally to its corresponding coefficient. Statistics in lower left corner indicate satisfactory fit of the model. b. Effects of Stipa on steady–state infiltration under ponding. c. Effects of BSC cover on steady–state infiltration under ponding. d. Effects of rabbit disturbance upon total BSC cover. Source: Eldridge et al. (2010)

Dew is an important source of water in drylands, particularly for BSCs, albeit its effects on the cycling of nitrogen (N) and carbon (C) in BSC-dominated ecosystems are largely unknown. To evaluate the effects of BSCs and dew on N and C cycling, intact soil cores from either bare ground or BSC-dominated microsites were incubated under control and artificial dew addition treatments (Delgado-Baquerizo et al. 2013b). A positive increment in the amount of total available N and phenols was observed in response to dew events under BSCs (Figure 7). We also found an increase in the concentration of dissolved organic N, as well as in the pentoses:hexoses ratio, under BSCs, suggesting that dew promoted an increase in the decomposition of organic matter at this microsite. The increase in the amount of available N commonly observed under BSCs has been traditionally associated with the fixation of atmospheric N2 by BSC-forming cyanobacteria and cyanolichens. Our results provide a complementary explanation for such an increase: the stimulation of microbial activity of the microorganisms associated with BSCs by dew inputs. These effects of dew may have important implications for nutrient cycling in drylands worldwide, where dew events are common and BSCs cover large areas.




Figure 7. Increment in some nitrogen variables after 14 days of incubation under control and simulated dew conditions for biological soil crust (BSC) and bare ground (BG) soils. Data are means ± SE (n = 6). Significance levels between treatments (control and dew) are as follows: *p < 0.05; **p<0.01; ***p< 0.001. Source: Delgado-Baquerizo et al. (2013b).

Not all our BSC research has focused on the effects of these organisms soil variables and ecosystem processes/functioning! In collaboration with Adrián Escudero, Ana Sánchez and Arántzazu López de Luzuriaga, from the Biology & Department at the URJC, we have also evaluated how BSCs, water availability, perennial species (presence/absence of Stipa) and plant-plant interactions shape annual communities from the AES (Luzuriaga et al 2012). This study revealed that water stress acted as the primary filter determining the species pool available for the assembly of annual communities at the AES. Stipa and BSCs acted as secondary filters by modulating the effects of water availability. At extremely harsh environmental conditions, Stipa exerted a negative effect on the annual plant community, while at more benign conditions it increased annual community richness. Biological soil crusts exerted a contradictory effect depending on climate and on the presence of Stipa, favoring annuals in the most adverse conditions but showing repulsion at higher water availability conditions.

Effects of climate change on BSCs and on the ecosystem processes depending on them

Biological soil crusts are a great study system to explore multiple questions in community and ecosystem ecology (see Bowker et al. 2010 for a review), and their size and characteristics make them particularly suitable to explore climate change impacts on biotic communities and on the ecosystem processes depending on them.

As part of the PhD of Cristina Escolar, and with the funding of a Studentship awarded by the British Ecological Society, We started in 2008 a manipulative experiment to evaluate responses of the BSC community and its main constituents to a ~2.4 ºC increase in air temperature, and to a ~30% reduction of total annual rainfall, climatic conditions that mimic those forecasted for the last half of the 21st century at the AES. We established a factorial experimental design with three factors, each with two levels (Figure 8): BSC cover (poorly developed BSC communities with cover < 25% vs. well developed communities with cover > 75%), warming (control vs. a 2.4ºC annual temperature increase) and rainfall exclusion (control vs. a ~30% rainfall reduction in total annual rainfall). The working plots (1.2 m × 1.2 m) were randomly placed either on bare ground (8.6% ± 0.8 of BSC cover; mean ± SE, n = 40; hereafter Bare plots) or BSC-dominated (73.8% ± 1.7 of BSC cover; mean ± SE, n = 40; hereafter Crust plots) microsites. See Escolar et al. (2012) for additional details on the experiment.



Figure 8. View of an experimental plot with an open top chamber and a rainfall shelter in November 2008, after the full set up of the climate change experiment (left), and of part of the area where this experiment was deployed (right). Photographs by Cristina Escolar. Click here for additional pictures of this experiment.

Three years after the set up of the experiment, warming promoted a significant decrease in the richness and diversity of the whole BSC community (Figure 9, Escolar et al. 2012). This was accompanied by important compositional changes, as the cover of lichens suffered a substantial decrease with warming (up to 40% on average), while that of mosses increased slightly (from 0.3% to 7% on average). The physiological performance of the BSC community, evaluated using chlorophyll fluorescence, increased with warming during the first year of the experiment, but did not respond to rainfall reduction. These results indicate that ongoing climate change will strongly affect the diversity and composition of BSC communities, as well as their recovery after disturbances.


Figure 9. Differences in the cover and richness of biological soil crusts in areas without (Bare plots) and with well-developed biological soil crusts (Crust plots) between June 2008 and May 2011. Data represent means ± SE (n = 9-10). RS = rainfall exclusion, OTC = warming, and OTC x RS = warming and rainfall exclusion. * indicate P values from the Wilcoxon test: * P < 0.05, ** P < 0.01, *** P < 0.001. Source: Escolar et al. (2012).

The monitoring of this experiment continues, and in addition to the monitoring of the composition, cover and physiological performance of the BSC community, we have been measuring over the years multiple variables related to the C (soil organic C, soil respiration, net CO2 exchange, activity of the enzyme β-glucosidase, phenols, aromatic comounds, pentoses, and hexoses), P (phosphate and activity of the enzyme phosphatase) and N (in situ ammonium and nitrate availability, potential N mineralization) cycles, as well as the microbial community (abundance of fungi, bacteria and archaea). Nowadays we are analyzing all these data, and the article summarizing the C cycle responses to the first four years of climate change treatments is right now under review.

As part of his PhD, Manuel Delgado-Baquerizo conducted different experiments using soils and BSCs from the AES (Delgado-Baquerizo et al. 2013c, 2013d) to examine the role of BSCs in the resistance and resilience of N cycle (i.e. N availability, relative dominance of N forms and microbial biomass N) facing changes in temperature (from 5 to 30ºC) and water soil content (from 30 to 80% of water holding capacity), as well as in the ratios of C, N and P. Compared to bare ground areas, BSC-dominated microsites increased the resistance and resilience in N cycle variables to changes in temperature and in the C and N ratios, respectively. However, changes in soil water content did not affect the N cycle in neither biocrusts nor bare grounds areas, suggesting that processes such as mineralization in drylands have the same activity from 30 to 80% of water holding capacity.



Figure 10. View of an experimental plot used to simulate future climatic conditions in the Aranjuez Experimental Station during a winter sunrise. It isn´t a nice place to work? Photograph by Beatriz Gozalo.

Plant-plant interactions

During the PhD of Santiago Soliveres (you can download it from here) we have studied how Stipa tenacissima interacts with different shrub species (Retama sphaerocarpa and Lepidium subulatum) and annuals, and how the outcome of this effect is modulated by ontogeny and environmental stress (Figure 11).


Figure 11. Adult individual of Retama sphaerocarpa growing between several Stipa tenacissima tussocks at the Aranjuez Experimental Station. Photograph by Fernando T. Maestre.

Using the combination of spatial pattern analysis, fruit production surveys, carbohydrate assays, sowing experiments and dendrochronological techniques, we explored the interaction between Stipa tenacissima and Lepidium subulatum in South- and North-facing aspects of the AES (Soliveres et al. 2010). This battery of techniques allowed us to study the effects of the nurse plant during the whole life cycle of the protégée, and to assess the role of spatio-temporal variability in abiotic stress as a modulator of ontogenetic shifts in plant-plant interactions. Our results suggested a net facilitative effect of S. tenacissima on L. subulatum, which was particularly important during the germination of the later. This facilitative effect shifted to competition (growth reduction) early after establishment, which was also gradually reduced as the shrub aged (suggesting niche differentiation, Fig. 12). The magnitude of competition was reduced under low rainfall levels in south-facing slopes, whereas this response was observed due to other abiotic factors in north-facing slopes.


Figure 12. Relationships between the effect size of Stipa tenacissima on the growth of Lepidium subulatum, as measured by the RII index, and the age of Lepidium. Each RII value is obtained by averaging growth data from 12-16 Lepidium individuals. Source: Soliveres et al. (2010).

In a series of experiments running in parallel, we evaluated the interplay between biotic (herbivory by the rabbit Oryctolagus cunniculus) and abiotic (changes in water availability and frequency) factors as drivers of the outcome of the interaction between Stipa and Retama (Soliveres et al. 2011, 2013). Stipa protected Retama seedlings from rabbit herbivory during the wetter conditions of spring and winter, but this effect disappeared when rabbit pressure on Retama increased during summer drought. Stipa exerted a negative effect on the survival of Retama seedlings during the first three years of the experiment, which was mainly due to excessive shading. However, Stipa increased Retama recovery after initial rabbit impact, overriding in part this negative shade effect. The negative effects of Stipa on the photochemical efficiency of Retama juveniles decreased with higher water availabilities, but these effects did not extent to the survival and growth of Retama juveniles. Such effects also varied with the intra-annual water dynamics and its experimental manipulation, overall contradicting predictions from the stress – gradient hypothesis (i.e. increase in facilitative interactions with increasing abiotic stress)

Overall, facilitation research carried out at the AES highlights the crucial effect that positive interactions at early life-stages have to determine the long-term outcome of a given plant-plant interaction, and the existence of multiple shifts between facilitation and competition along different life-stages of the protégée. They also show how these ontogenetic shifts are modulated by abiotic factors, which differ among slope aspects. The complex interactions found between herbivory, microclimatic amelioration from Stipa, and water availability as drivers of Retama performance illustrate the importance of considering the temporal dynamics of both biotic and abiotic stressors to fully understand the outcome of plant – plant interactions.

The future of research at the Aranjuez Experimental Station

The different experiments and environmental monitoring sensors deployed over the last seven years make the AES a very interesting and unique research facility. As far as we can get funding to work there, we will continue the monitoring of the different experiments we have set up at the AES over the years. This is precisely a main goal of the work we are carrying out at the AES: to establish there the first Long-Term Ecological Research (LTER) station devoted to monitor soil CO2 and N fluxes in dryland areas of Europe, and to assess how biotic communities and the ecosystem processes depending on them will respond to ongoing climate change.

In addition to the long-term monitoring of the experiments described above, over the last years we have set up new and ongoing experiments in collaboration with colleagues from other institutions. With José I. Querejeta and Lupe León, from CEBAS-CSIC, we have set up new climate change plots to evaluate the effects of increased temperatures and reduced rainfall on the physiology and growth of Helianthemum and Lepidium. With Ana Rey and María Almagro, from MNCN-CSIC, we are studying how UV radiation affects the decomposition of Stipa litter (Fig. 13). Before next August we also hope to have ready a new field experiment on litter decomposition at the AES, which will be part of the PhD of Miguel Berdugo.



Figure 13. Partial view of the litter decomposition experiment set up by Ana Rey at the Aranjuez Experimental Station. Photograph by Fernando T. Maestre

The research carried out at the AES has been possible thanks to the support of the following organizations and funding agencies: British Ecological Society (Early Career Project Grant 231 ⁄ 607 and Studentship 231/1975), Fundación BBVA (Intercambio project), Comunidad de Madrid (S-0505/AMB/0335), Universidad Rey Juan Carlos (URJC-RNT-063-2), Spanish Ministry of Science and Innovation (CGL2008- 00986-E/BOS grant) and European Research Council (BIOCOM project). And to finish this post a big thanks to all the people that have been working at the AES over the years. In addition to the students and colleagues named above, we must mention the different technicians (María D. Puche, Victoria Ochoa, Rebecca Mou, Alicia Puche, Beatriz Gozalo, Patricia Alonso, Jorge Papadopoulos, and Marta Carpío), students (Pablo García-Palacios, Enrique Valencia), collaborators (Antonio Gallardo, Roberto Lázaro), post-docs (Matthew Bowker, José Luis Quero and Raúl Ochoa-Hueso) and visitors (David Eldridge, Juan Diego Mentruyt,  Juan Gaitán, Riin Tamme and different students from Pennsylvania State University) that have been working and helping with the different experiments set up at the AES. Without their hard work and enthusiasm we would not have been able to conduct all the different research activities highlighted above.




Figure 14. From up to down, and left to right: i) Andrea measuring soil respiration, ii) a few of us trying to get the van out of the mud, iii) Miguel and José Luis measuring net CO2 exchange at sunrise, iv) Bea, Victoria and José Luis getting ready for a fun day of measurements during winter, and v) Fernando explaining what we do in Aranjuez to some visitors. Photographs by Fernando T. Maestre, Miguel Berdugo, Santiago Soliveres and Miguel García.
 

Check out our twitter account and webpage for further news and research outputs from the Aranjuez Experimental Station!


References

You can obtain copies of the publications listed below in the Maestre lab webpage.

Bowker, M. A., F. T. Maestre & C. Escolar. 2010. Biological crusts as a model system for examining the biodiversity-ecosystem function relationship in soils. Soil Biology & Biochemistry 42: 405-417.
Castillo-Monroy, A. P. & F. T. Maestre. 2011. La costra biológica del suelo: Avances recientes en el conocimiento de su estructura y función ecológica. Revista Chilena de Historia Natural 84: 1-21.
Castillo-Monroy, A. P., F. T. Maestre, A. Rey, S. Soliveres & P. García-Palacios. 2011. Biological soil crusts are the main contributor to soil CO2 efflux and modulate its spatio-temporal variability in a semi-arid ecosystem. Ecosystems 14: 835–847.
Castillo-Monroy, A. P., F. T. Maestre, M. Delgado-Baquerizo & A. Gallardo. 2010. Biological soil crusts modulate nitrogen availability in semi-arid ecosystems: Insights from a Mediterranean grassland. Plant and Soil 333: 21-34.
Delgado-Baquerizo, M., A. P. Castillo-Monroy, F. T. Maestre, & A. Gallardo. 2010. Changes in the dominance of N forms within a semi-arid ecosystem. Soil Biology & Biochemistry 42: 376-378.
Delgado-Baquerizo, M., F. Covelo, F. T. Maestre & A. Gallardo. 2013a. Biological soil crusts affect small-scale spatial patterns of inorganic N in a semiarid Mediterranean steppe. Journal of Arid Environments 91: 147-150.
Delgado-Baquerizo, M., F. T. Maestre, J. G. P. Rodríguez & A. Gallardo. 2013b. Biological soil crusts promote N accumulation in response to dew events in dryland soils. Soil Biology & Biochemistry 62: 22–27.
Delgado-Baquerizo, F. T. Maestre & A. Gallardo. 2013c. Biological soil crusts increase the resistance of soil nitrogen dynamics to changes in temperatures in a semi-arid ecosystem. Plant and Soil 366: 35-47.

Delgado-Baquerizo, M., L. Morillas, F. T. Maestre & A. Gallardo. 2013d. Biocrusts control the nitrogen dynamics and microbial functional diversity of semi-arid soils in response to nutrient additions. Plant and Soil, doi: 10.1007/s11104-013-1779-9.
Eldridge, D., M. A. Bowker, F. T. Maestre, P. Alonso, R. L. Mau, J. Papadopoulos & A. Escudero. 2010. Interactive effects of three ecosystem engineers on infiltration in a semi–arid Mediterranean grassland. Ecosystems 13: 499-510.
Escolar, C., I. Martínez, M. A. Bowker & F. T. Maestre. 2012. Warming reduces the growth and diversity of biological soil crusts in a semi-arid environment: implications for ecosystem structure and functioning. Philosophical Transactions of the Royal Society B 367: 3087–3099.
Luzuriaga, A. L., A. M. Sánchez, F. T. Maestre & A. Escudero. 2012. Assemblage of a semi-arid annual plant community: Abiotic and biotic filters act hierarchically. PLoS ONE 7: e41270.
Maestre, F. T., M. A. Bowker, M. D. Puche, C. Escolar, S. Soliveres, S. Mouro, P. García-Palacios, A. P. Castillo-Monroy, I. Martínez & A. Escudero. 2010. Do biotic interactions modulate ecosystem functioning along abiotic stress gradients? Insights from semi-arid plant and biological soil crust communities. Philosophical Transactions of the Royal Society B 365: 2057-2070.
Maestre, F. T., M. A. Bowker, Y. Cantón, A. P. Castillo-Monroy, J. Cortina, C. Escolar, A. Escudero, R. Lázaro & I. Martínez. 2011. Ecology and functional roles of biological soil crusts in semi-arid ecosystems of Spain. Journal of Arid Environments 75: 1282-1291.
Soliveres, S., P. García-Palacios, A. P. Castillo-Monroy, F. T. Maestre, A. Escudero & F. Valladares. 2011. Temporal dynamics of herbivory and water availability interactively modulate the outcome of a grass-shrub interaction in a semi-arid ecosystem. Oikos 120: 710-719.
Soliveres, S., F. T. Maestre, A. Escudero, P. García-Palacios, F. Valladares & A. P. Castillo-Monroy. 2013. Changes in rainfall amount and frequency do not affect the outcome of the interaction between the shrub Retama sphaerocarpa and its neighbouring grasses in two contrasted semiarid communities. Journal of Arid Environments 91: 104-112.
Soliveres, S., L. DeSoto, F. T. Maestre & J. M. Olano. 2010. Spatio-temporal heterogeneity in abiotic factors can modulate multiple ontogenetic shifts between competition and facilitation. Perspectives in Plant Ecology, Evolution and Systematics 12: 227-234.

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