Understanding the role of environmental conditions and geographic space on species distributions is a major goal of ecological studies. Here, we investigate the effects of soil properties, a native bamboo (Actinocladum verticillatum (Nees) McClure ex Soderstr) ground cover and geographic distance on species richness and turnover in the Brazilian Cerrado. We established three transects along a forest-savanna gradient (14°41 0 S and 52°20 0 W), from the lowland next to a stream to the top of a hill, where we sampled the woody plant community (DBH ≥ 3 cm), soil properties and ground cover of A. verticillatum. We evaluated changes in species composition with a principal coordinates analysis, and the effects of the environmental predictors on species richness using generalised linear models and on species turnover using generalised dissimilarity modelling. We found that species richness increases with K concentration in the soil and decreases with Zn concentration in the soil and bamboo cover. The predictors explained 62% of species turnover, with environmental parameters (soil properties, bamboo cover and altitude) having the most significant contribution (80%), followed by the spatially structured environmental variation (20%). The most important environmental predictors of woody species turnover were soil concentration of Zn, P and K, altitude, and bamboo cover. Changes in species richness and composition in the studied gradient were strongly associated with plot height, bamboo cover and soil content of K, Zn and P. Our findings indicate that nutrient availability and competition with bamboo explain vegetation structure and composition in this region.
The effects of steam‐treated (hydrolytic process using high temperature 207°C and high pressure steam 1.6 MPaG for 30 min) grass clippings and their liquid residue on growth, drainage water quality and soil microbial properties were evaluated. Soils were placed in plastic containers (47 cm length × 40 cm width × 22.5 cm depth) so that the surface (0–10 cm depth) was a mixture of Andisol and sand (3:2 volume) and the subsurface soil (10–20 cm depth) was Andisol only. A basal dose of chemical fertilizer (25 g m−2 NPK 8–8–8) and poultry manure (20 g m−2) was applied. The treatments were: CF (without incorporation of plant residues and 25 g m−2 NPK 8–8–8 top dressing 1 month after transplanting), LL (1 kg m−2 commercial leaf litter), GT (1 kg m−2 steam‐treated grass clippings), GT + BL (1 kg m−2 steam‐treated grass clippings plus 6 L m−2 liquid residue in a single application as basal fertilizer), GT + FL (1 kg m−2 steam‐treated grass clippings plus 3.2 L m−2 liquid residue diluted 10‐fold and applied six times as fertigation), and GT10 (10 kg m−2 steam‐treated grass clippings). In all treatments, Manila grass (Zoysia matrella) was transplanted. The total dry matter yield of clippings was highest in GT10 (752 kg m−2), followed by GT (503 kg m−2), LL (491 kg m−2) and lowest in CF (378 kg m−2). Liquid residues did not show a positive effect on grass growth, probably because of low pH (4.5). Incorporation of high amounts of steam‐treated grass clippings (GT10) can result in more nitrate leaching. The trends in microbiological properties in response to the different treatments were the same as the grass growth (GT10 > GT > LL > CF). Steam‐treated grass clippings can enhance microbial activities and can partially replace chemical fertilizer. However, the incorporation of an adequate amount is necessary to minimize the environmental load by nitrate leaching. Liquid residue requires another form to be used.
Resistência mecânica do solo à penetração avaliada em área de segundo ano de implantação da cultura da mandioca (Manihot esculenta CRANTZ) Mechanical resistance of soil to penetration evaluated in the second year of implantation of cassava (Manihot esculenta CRANTZ)
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