View from the southern Eddy tower of the MANIP experiment over the Dehesa of Spain towards the north. Distinct cork and holm oak groves where cows graze and Iberian pigs gorge themselves on acorns. In the front part of the picture a small mast with a swiveling radiation boom, which alternately measures over tree and grassland. In the background the mountains

MANIP - Majadas del Tietar (Spain) 

MANIP - MAnipulation NItrogen and Phosphorous

Manipulation experiment with nitrogen and phosphorus in the dehesa (holm oak groves) of Spain, with extensive measurements of the ecosystem.

Description & History

The site is located in a holm oak grove (dehesa) in Majadas del Tietar, Caceres, Spain (39°56′ N; 5°46′ W, 260 m a.s.l.).

The soil is classified as Cambisol (Dystric) [IUSS Working Group WRB, 2006] and originated from Pliocene-Miocene sedimentary deposits. The soil profile is about 90 cm deep with a clay horizon between 30 and 60 cm; in contrast, the texture in the upper horizons is sandy (9.3% clay, 10.7% silt, 80.0% sand). The pH is about 5.6 in the first 15 cm. The soil organic matter and associated extractable C fractions decrease very much in the first 15 cm of the soil.

The climate is continental Mediterranean with mild winters. Mean annual temperatures are 16.7°C and mean annual precipitation is 528 mm, with less than 6% of precipitation in summer. Occasional rain events occur on 5 to 10 days in the summer of a year. Where usually less than 20 mm falls per day.

The open tree layer (24.8 trees ha-1) consists of evergreen holm oak (Quercus ilex ssp ballota Lam.) with occasional interspersed cork oak (Q. suber L.) and Portuguese oak (Q. faginea Lam.) (<5%). Tree canopy cover averages 19.8%. The herbaceous layer consists mainly of anuelle (Vulpia bromoides (L.) SF Grey; V. geniculata (L.) Link; Trifolium subterraneum L., Ornithopus compressus L.), which wither by the end of May.

The site there is used for traditional woodland grazing (cows and Iberian pigs) (see Lopez-Sangil et al. [2011]).

In March 2014, two new identical measurement towers were erected for Eddy covariance measurements, and areas for chamber measurements were designated and prepared accordingly. A third small tower, a so-called "subcanopy eddy covariance tower" was built in June 2014.

Extensive placement of ground sensors took place in late fall 2014, as well as the construction of a smaller tower for meteorological purposes, at the site of which another eddy tower is eventually planned.

The 2014 growing season will serve as a status quo before the actual manipulation experiment begins in 2015.

Mid-October 2015: travel to Majadas and set up 6 additional towers (2 subcanopy eddy towers, 3 radiation towers, and a mobile tower in Albuera at a drier site where less precipitation falls) with their various sensors.


Dehesa - grazed holm oak grove (hute forest) of Extremadura; Las Majadas del Tietar (Spain)
Latitude: 39.94
Longitude: -5.77
Elevation: 260 m a.s.l.


  • Since 2014
  • Eddy covariance (CO2, H2O); (CEAM-Eddy since 2003)
  • MaNip - field manipulation experiment (moisture gradient/nutrient gradient).
  • Tree growth
  • Meteorology
  • Soil conditions
  • Differences light/ shade
  • Chamber measurements
  • Lysimeter


  • Fluxpec
  • Biospec


  • CEAM - Dr. Arnaud Carrara, scientific PI; Ramón Lopez, industrial engineer/technician

Variables & Instruments


  • Eddy covariance - CH4, CO2, water vapor, momentum, heat flux (USA-1, LI7500 and Los Gatos).
  • Subcanopy Eddy
  • Profile at 7 altitudes - CO2, water vapor


  • Wind speed and direction - Ultrasonic Anemometer USA-1, Metek
  • Air pressure - pressure transducer 61302V, Young
  • Air temperature and humidity - temperature-humidity sensor KPK1_5-ME, Mela
  • Precipitation - Tipping bucket precipitation gauge, Thies
  • Solar radiation - radiation balance sensor CNR4, Kipp & Zonen
  • Terrestrial radiation - Radiation Balance Sensor CNR4, Tilt & Zones
  • Photosynthetically active radiation - PAR sensor PQS1, tilt & zones

Soil Conditions

  • Soil temperature - Soil temperature sensors PT100, home-made
  • Soil Moisture (Preliminary) - Soil Moisture Probe ML-2x, Delta-T
  • Soil Moisture (grid)- Soil Moisture Probe EnviroSCAN , Sentek Easy AG
  • Soil Temperature Profile (5, 10, 20, 30, 50 & 100 cm) - Soil Temperature Profile Probe Th3, UMS

Data acquisition

  • Meteorological data - Data logger CR3000, Campbell Scientific
  • CO2 profile data - CR3000 data logger, Campbell Scientific
  • Soil sensor data - Data logger CR3000, Campbell Scientific
  • River data - industrial computer
  • Vegetation - digital camera


Casals, P., L. Lopez-Sangil, A. Carrara, C. Gimeno, and S. Nogués (2011). Autotrophic and heterotrophic contributions to short-term soil CO2 efflux following simulated summer precipitation pulses in a Mediterranean dehesa. Global Biogeochem. Cycles, 25, GB3012, doi:10.1029/2010GB003973.

Lopez-Sangil, L., J. Rousk, H. Wallander, and P. Casals (2011). Microbial growth rate measurements reveal that land-use abandonment promotes a fungal dominance of SOM decomposition in grazed Mediterranean ecosystems. Biol. Fertil. Soils, 47, 129-138, doi:10.1007/s00374-010-0510-8.

MANIP - MAnipulation NItrogen and Phosphorous.


A long-term experimental project aims to understand the responses of different eddy covariance (EC) sites to nutrient loading (mainly N and P) and water availability, ecosystem-level carbon and water fluxes, and their interannual variability. Three foci of the project are understanding ecosystem physiological response to changing N/P stoichiometry and water availability, structural and physiological phenology of tree-grass systems, and soil processes and properties.
The experimental sites were established in spring 2014. The project is divided into two questions. The first focuses on the effects of N/P availability on ecosystem functioning and structure and will be conducted mainly in the "WET" cluster in Majadas del Tietar, Spain (~650 mm annual precipitation). The second study addresses the effects of varying water availability on ecosystem functioning and phenology, examining ecosystem fluxes and phenology at the "WET" and "DRY" sites.

"WET" cluster

The WET cluster is associated with an existing long-term EC site that provides more information about the site history and available time series, which helps establish a "baseline" for the magnitude and interannual variability of C, water, and energy fluxes. Sites are selected to have similar nutrient conditions, soil chemical-physical properties, canopy structure, and stoichiometry of the various vegetation stands. The "WET" site is a Mediterranean savanna in Majadas del Tietar (Extramadura, Spain) (Figure 1). The mean annual temperature is 16˚C, and the mean annual precipitation is about 650 mm, most of which falls from November to May, with a very dry summer. The land consists of low-intensity grazing cows, individual oaks, and open grasslands. The herbaceous layer consists primarily of annual species with grasses, forbs, and legumes accounting for 84%, 15%, and ~1%, respectively, at the peak of the growing season. The different plant species show different phenology throughout the year. The soil texture of the upper soil horizons to a depth of 30 to 60 cm is sandy loam or loamy sand (SL or LS according to FAO soil description guidelines). In the deeper subsoil, the clay content increases, resulting in a clayey loam texture (CL). The average N/P ratio of vegetation measured in November 2013 is about 14 for trees and 9.1 for herbaceous plants.
In the N-ADD and NP-ADD, 2 eddy covariance flux towers were installed in March 2014. In the first phase of the experiment, which is currently underway, EC measurements are being made without any manipulation of the ecosystem to evaluate possible systematic differences between C and water fluxes at different sites. After evaluating this first phase, two basal sites will be manipulated by adding N and NP. Digital cameras to monitor phenology and grazing activity, spectrometers, and sap flow meters will be installed at each site. Three automatic weighed lysimiter stations and an EC system were also installed under the canopy at the main site.

Figure 1: Map of the MaNiP experimental site and location of the three EC stations in the "WET" cluster. The red lines represent the footprint climatology according to Göckede et al. (2008). The area of the Small Scale Manipulation Experiment (SMANIE) is also indicated.

DRY cluster

In the DRY cluster, the plan is to set up a mobile EC tower and, after the first year of measurements, to set up a permanent system and a mobile tower. Site screening conducted in the summer and fall of 2014 allowed potential sites to be identified. Currently, one site has been selected and a measurement station was installed in November 2014 to characterize the precipitation and wind conditions needed to plan the installation of the new eddy covariance site.

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