Effects of soil mechanical resistance on nematode community structure under conventional sugarcane and remaining of Atlantic Forest

Abstract

Nematodes present high potential as a biological indicator of soil quality. In this work, it was evaluated relations between soil physical properties and nematode community under sugarcane cropping and remaining of Atlantic Forest areas in Northeastern Pernambuco, Brazil. Soil samples were collected from September to November 2009 along two 200-m transects in both remaining of Atlantic Forest and sugarcane field at deeps of 0-10, 10-20, 20-30, 30-40, and 40-50 cm. For soil characterization, it was carried out analysis of soil size, water content, total porosity, bulk density, and particle density. The level of soil mechanical resistance was evaluated through a digital penetrometer. Nematodes were extracted per 300 cm(3) of soil through centrifugal flotation in sucrose being quantified, classified according trophic habit, and identified in level of genus or family. Data were analyzed using Pearson correlation at 5% of probability. Geostatistical analysis showed that the penetration resistance, water content, total porosity, and bulk density on both forest and cultivated area exhibited spatial dependence at the sampled scale, and their experimental semivariograms were fitted to spherical and exponential models. In forest area, the ectoparasites and free-living nematodes exhibited spherical model. In sugarcane field, the soil nematodes exhibited pure nugget effect. Pratylenchus sp. and Helicotylenchus sp. were prevalent in sugarcane field, but in forest, there was prevalence of Dorylaimidae and Rhabditidae. Total amount of nematode did not differ between environments; however, community trophic structure in forest presented prevalence of free-living nematodes: omnivores followed by bacterial-feeding soil nematodes, while plant-feeding nematodes were prevalent in sugarcane field. The nematode diversity was higher in the remaining of Atlantic Forest. However, the soil mechanical resistance was higher under sugarcane cropping, affecting more directly the free-living nematodes; especially Dorylaimidae which was the most sensible to changes in soil physical properties.

Nematodes and Microorganisms Interactively Stimulate Soil Organic Carbon Turnover in the Macroaggregates

“…The porosity of soil macroaggregates with porosity >100 μm was significantly improved under the M2 and M3 treatments (Figure 2 ), likely supporting the observed high densities of bacterivores. Nematodes are typically sensitive to the changes in the proportions of large pore sizes that are associated with intensive management (Cardoso et al, 2012 ). The intra-aggregate microarchitecture of soil macroaggregates with an adequate pore size range offers a suitable space for nematodes moving and migrating to their food sources.…”

Trees in the Agricultural Matrix: Reforestation Processes in a Tropical Dry Landscape in Chinandega, Nicaragua

“…Nicaragua increased it's sugarcane planted area in 2013 by 13% to 67,128 ha, a number expected to surge another 20% by 2016, while peanut plantations occupy 42,253 ha, 82% of which is concentrated in the west, directly affecting the study site (USDA 2013). These production increases demonstrate a dynamic that will negatively transform the landscape mosaic in these communities, as the highly mechanized cultivation of these crops compacts soil, and reduces soil fertility and productivity, adding urgency to increasing tree cover in the other elements of the landscape (Naranjo de la F. et al 2006, de Oliveira Cardoso et al 2012. While the forested riparian corridors that exist within this landscape provide a great resource for passive restoration, hosting a density and species diversity comparable to other disturbed dry forests and facilitating relatively diverse second growth forests, the diversity of species composition of pasture trees and live fences can be promoted to encourage further diversity restoration (Valencia 1998, Sagar and Singh 2006.…”