Relação entre a presença de cupinzeiros e a degradação de pastagens

Abstract

Resumo -O objetivo deste trabalho foi avaliar indicadores químicos, físicos e biológicos da degradação de pastagens em áreas contrastantes quanto à ocorrência de cupinzeiros. Foram avaliadas as áreas de pastagem com a cultivar Marandu de Urochloa brizantha (Syn. Brachiaria brizantha), quanto à ausência (pasto 1) ou à presença (pasto 2) de cupinzeiros, e área com vegetação nativa de Cerrado. Foram avaliados: granulometria e fertilidade do solo; atividade microbiana do solo; nitrogênio potencialmente mineralizável; produção da gramínea em oferta; liteira existente e depositada no período de 28 dias; e fração leve da matéria orgânica do solo. No pasto 2, os cupinzeiros foram contados e 20 ninhos foram sorteados para coleta e identificação de cupins. Cornitermes cumulans foi a única espécie coletada, com média de 128 ninhos por hectare, tendo ocupado 0,1% da área útil. Entre os indicadores avaliados, apenas a oferta e a liteira diferiram entre as áreas de pastagens. A maior densidade de cupinzeiros não pode ser relacionada à acidez do solo ou aos outros parâmetros avaliados. A presença de cupinzeiros não é indicador de degradação química e biológica da pastagem e não está associada à alteração na dinâmica de resíduos da parte aérea de capim-marandu.Termos para indexação: Brachiaria brizantha, Cornitermes cumulans, cupins, montículos, pastagem degradada. Relationship between the presence of termite mounds and pasture degradationAbstract -The objective of this work was to evaluate chemical, physical and biological indicators of degradation of pastures in areas with contrasting occurrence of termite mounds. Pasture areas with the Marandu cultivar of Urochloa brizantha (Syn. Brachiaria brizantha) were evaluated for the absence (pasture 1) or presence (pasture 2) of termite mounds, and an area of native Cerrado vegetation. The following parameters were evaluated: soil texture and fertility; soil microbial biomass; potentially mineralizable nitrogen; forage on offer; existing litter and litter deposited on the soil surface in 28 days; and free light fraction of soil organic matter. In pasture 2, termite mounds were counted and 20 nests were randomly selected for collection and identification of termites. All active mounds were inhabited by the species Cornitermes cumulans, with a mean of 128 mounds per hectare, occupying 0.1% of the net area. Among the indicators evaluated, only forage on offer and litter deposited in 28 days differed between pasture areas. The greater density of termite mounds was not related with the higher acidity of the soil or with the other evaluated parameters. The presence of termite mounds is not an indicator of the chemical and biological degradation of the pasture and is associated with the dynamics of aerial residues of Marandu palisadegrass.

Spatial Variability and Vitality of Epigeous Termite Mounds in Pastures of Mato Grosso Do Sul, Brazil

“…Oliveira et al (2011) found higher mound occurrence (408 mounds ha -1 ) on the Central Cerrado Plateau. Confirming findings of Lima et al (2011), the pasture areas studied were considered homogeneous, productive and undegraded, when assessing indicators of pasture degradation (soil fertility and microbial biomass, light fraction of organic matter, litter and existing regrowth) in the areas of this study, differing from many pastures areas in Brazil that are densely occupied by epigeous termite mounds. Ecological studies on the spatial distribution pattern and other termite mound parameters, such as vitality, are important in explaining the higher or lower formation intensity of epigeous mounds in pasture areas.…”

“…Moreover, Jiménez et al (2006) reported that unequal distribution of resources can determine the spatial distribution of soil organisms, which can alternate between high and low density in a same area. Lima et al (2011) recorded high productivity and consequent homogeneity of food distribution for termites in both pasture areas studied. Owing to these characteristics, the hypothesis of intraspecific competition cannot explain the random spatial distribution of termite mounds.…”

“…Despite the beneficial importance of termites to soil processes the useful pasture area can be reduced by very dense populations of epigeous mounds (Valério, 1995), which has led cattle farmers to find ways to destroy the mounds (Ávila and Goulart, 1995). Termite mounds have been commonly associated with pasture degradation, but this hypothesis has been recently refuted by Lima et al (2011) in an evaluation of soil and plant parameters in Cerrado areas.…”

Termite Mounds Effects on Soil Properties in the Atlantic Forest Biome

“…The presence of termites is commonly associated with soil degradation, declining fertility, and mainly increased soil acidity levels. However, in a study by Lima et al (2011), none of the analyzed degradation indicators confirmed any relation between the amount of termite mounds and the degree of pasture degradation. Despite this progress in the knowledge of the abundance of species that build epigean mounds such as C. cumulans, little is known about the impact of termite activities on the ecosystem.…”

Soil Physical and Chemical Properties in Epigeal Termite Mounds in Pastures

“…We identified individuals of the genera Embiratermes (three mounds), Velocitermes (two mounds), and Orthognathotermes (two mounds), one of which cohabited the mound with Embiratermes. These genera are commonly observed cohabiting in mounds within pastures of other builder species, such as Cornitermes snyderi and Cornitermes cumulans (Lima et al, 2011;Cunha & Morais 2010), but only Orthognathotermes does not build mounds (Constantino, 1999).…”