Pheidole fallax data
Description
Pheidole fallax is one the most abundant ants in sites where coal mines have undergone rehabilitation and in forests without mine intervention. The impact that this species may have as ecosystem engineer needs to be assessed. We aimed to test whether P. fallax nests have an effect on soil chemical properties, characterize the organic debris found in the refuse piles and describe nest architecture as proxy of bioturbation effect. The study was carried out in areas with 16 and 20 years of rehabilitation in a coal mine in Colombia. Samples were taken from inside the nests, from the external refuse pile and from a control area one meter away from the nest. Chemical analysis and near infrared spectra (NIRS) of the three sample types were obtained. Our results showed that P. fallax use food resources of different trophic levels, being arthropods and seeds the main items in their diet. The NIRS analysis enabled distinguishing the origin of the sample: refuse pile, interior of nest or control soil. The refuse piles of P. fallax had a lower pH and accumulated high contents of Ca + 2, Mg + 2, K + 1 and organic matter, when compared with the other two sites. Three dataframe are provided: (1) organic debris found in the refuse piles, (2) Chemical properties of soils collected in Pheidole fallax (n = 7) nests, coal mine, refuse piles and control soil from 20-y site in Cerrejón mine, located in La Guajira, Colombia and (3) NIRS results analysis of refuse piles (RP), soil of Pheidole fallax nests and control soil (CS), in the plane defined by the first two factors in the 20-y site.
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Fifteen nests (five per plot) were selected randomly from each area (16 and 20-y) for characterization of organic debris in refuse piles. All debris found in the refuse piles was collected. In the laboratory, the organic debris was sorted into three groups: a) Carcasses or parts of arthropods (AD: arthropod debris), b) seeds and c) parts of other animals (OAD: other animal debris). Each sample was cleaned, dried and weighed using an analytical balance. Given availability of nests, chemical properties and NIRS analyses were assessed only for those found in the 20 y-site (from two plots). Seven nests were selected and three types of samples were collected for chemical analyses: (1) 400 g of soil from the entrance of nests at a depth of 10 cm, (2) a sample from the refuse pile (sample size depending on the size of the refuse pile) and (3) a control sample obtained from soil located at least 1 m away from the nest’s entrance. The same protocol was followed in every nest, after having previously verified that there was no ant activity in the nest. Five chemical variables were measured: total Phosphorous (P) (L-ascorbic spectrophotometry UV-VIS), Ca+2, Mg+2, K+1 (1N ammonium acetate, atomic absorption), pH (in a 1v:2v water solution), organic matter content using the Walkley and Black volumetric method (Walkley and Black, 1934), and the effective cation exchange capacity (ECEC) as the sum of cations extracted with 1 N ammonium acetate. For NIRS analyses 10 nests of P. fallax were selected to evaluate the ability of NIRS (750-2500 nm) to discriminate nest soil from surrounding soil. Two 10-g samples were taken from each nest, control soil and refuse piles to sift them through a 500 µm sieve. One gram of each sifted soil sample was further scanned with a spectrometer (NIRFLEX N 500, Buchi®) in the 1010 - 2550 nm spectral range. Measurements were taken at four-nanometer intervals. Reflectance (R) was converted to absorbance (A) using the equation: A = log (1/R) and further transformed to second derivative following the general procedures recommended for the treatment of this particular type of signal. Finally, average values were calculated for 8 nm intervals in order to reduce the number of variables processed (Zangerlé et al., 2014). The software Unscrambler X 10.3 was used to obtain the second derivative transformation.