『Abstract
Termite activities are known to significantly influence small-scale
soil properties in tropical savannas. The lateral and vertical
extent of the alterations to the nest's surrounding, and particularly
resulting impacts on diagnostic soil horizons remain largely unresolved
until today. We examined the effects of mound-building termites
on soil genesis and constitutive chemical soil properties in and
below their nests. Two transects to a soil depth of 100 cm were
dug below three younger mounds of Cornitermes silvestrii
(the primary nest builder), three older mounds in which C.
silvestrii had died out and which were secondarily colonized
mainly by Nasutitermes kemneri, and three reference sites
in the Brazilian Cerrado. The samples were characterized by standard
procedures for soil classification; in addition, phosphorus extractions
were conducted on selected samples using NaHCO3
for labile P forms, and concentrated HCl for stable P forms. This
data set was then used to build calibration models for the prediction
of labile and stable inorganic (Pi) and organic
(Po) P forms, as well as for contents of
organic carbon (OC), for the remaining samples applying mid-infrared
spectroscopy in combination with partial least squares regression
(MIRS-PLSR). We can show that the termite influence on the soil
was sufficiently large to change diagnostic characteristics of
the soils under termite mounds. The MIRS-PLSR predictions were
suitable for quantifying organic carbon and most of the labile
and stable phosphorus fractions. They showed an enrichment of
OC, NaHCO3-Po and NaHCO3-Pi contents in nests inhabited
by primary and secondary termites by factors of 1.6-2.0 and 1.4-1.5,
respectively. The soils surrounding the nests had higher contents
of OC and NaHCO3-P under both nest types
vertically down to 30 cm below the lower nest border, and OC and
NaHCO3-Pi contents were
elevated at minimum to a lateral distance of 60 cm away from the
nest border. As the pattern of HClconc-Pi, which comprised 95% of total P, showed no variations,
we conclude that the higher NaHCO3-Pi amount was formed in termite nests by changing
the availability of the more stable HClconc-Pi. In contrast to the contents, the OC and NaHCO3-P stocks below the mounds inhabited by primary
termites were comparable to those inhabited by secondary ones,
because the bulk density of the secondarily inhabited nests was
elevated. This was due to a transport of clay-rich material from
the subsurface argic horizons into the nests. Here, the secondary
termites even reverted the lessivation observed in the reference
soils and under mounds inhabited by primary termites, thus causing
the soil types to change from Alisols and Acrisols to the properties
of Umbrisols.
Keywords: Cornitermes silvestrii; Nasutitermes kemneri;
Brazil; Cerrado; Savanna; Mid-infrared spectroscopy (MIRS)』
1. Introduction
2. Materials and methods
2.1. Study site
2.2. Sampling
2.3. Chemical analyses
2.4. MIRS-PLSR
2.5. Data analyses
3. Results
3.1. Soil under termite mounds - morphological changes and
classification
3.2. Soil properties under termite mounds
3.3. Carbon patterns in soils surrounding termite nests
3.4. Phosphorus patterns in soils surrounding termite nests
4. Discussion
4.1. Soil genesis and changes in the soil horizons under
termite mounds
4.2. Spatial extension of termite effects on adjacent soil
4.3. Differences between mounds inhabited by primary and secondary
termites
5. Conclusion
Acknowledgements
References