Estimating lime requirements for tropical soils: Model comparison and development.

Acid tropical soils may become more productive when treated with agricultural lime, but optimal lime rates have yet to be determined in many tropical regions. In these regions, lime rates can be estimated with lime requirement models based on widely available soil data. We reviewed seven of these models and introduced a new model (LiTAS). We evaluated the models' ability to predict the amount of lime needed to reach a target change in soil chemical properties with data from four soil incubation studies covering 31 soil types. Two foundational models, one targeting acidity saturation and the other targeting base saturation, were more accurate than the five models that were derived from them, while the LiTAS model was the most accurate. The models were used to estimate lime requirements for 303 African soil samples. We found large differences in the estimated lime rates depending on the target soil chemical property of the model. Therefore, an important first step in formulating liming recommendations is to clearly identify the soil property of interest and the target value that needs to be reached. While the LiTAS model can be useful for strategic research, more information on acidity-related problems other than aluminum toxicity is needed to comprehensively assess the benefits of liming.

Woody species distribution across a savanna-dry forest soil gradient in the Brazilian Cerrado / Distribuição de espécies arbóreas em gradiente de solo savana-floresta seca no Cerrado brasileiro

Although richness and distribution of woody species in the Cerrado physiognomies have been extensively studied, the shifts of woody species from savanna physiognomies to dry forests have not yet been addressed. Here, we investigate the effect of soil physical-chemical traits on the woody species turnover between adjacent cerrado stricto sensu and dry forest physiognomies. Woody species were surveyed, and soil and topographic variables measured, in 30 10×40 m plots systematically distributed, with 15 plots in each physiognomy. We found a spatially structured distribution of woody species, and differences of soil traits between cerrado stricto sensu and dry forest areas, mainly related to the aluminum saturation, base saturation, and available phosphorus. Aluminum saturation increased toward the savanna area, while base saturation increased toward the dry forest. Most woody species predominated in one physiognomy, such as Callisthene major in the cerrado stricto sensu and Anadenanthera colubrina in the dry forest. Only 20% of the species were widely distributed across both physiognomies or, not often, restricted to the intermediary values of the soil gradient. General results indicate that contrasting soil traits between cerrado stricto sensu and dry forest produce a strongly spatially organized and sharp transition in terms of species distribution between these physiognomies.

Embora a distribuição e a riqueza em espécies arbóreas nas fitofisionomias do Cerrado venham sendo bastante estudadas, a transição entre savanas e florestas deciduais ainda não foi abordada. Investigamos o efeito de características físico-químicas do solo sobre a distribuição de espécies arbóreas em região de contato entre cerrado sentido restrito e floresta estacional decidual (FED). As espécies arbóreas foram amostradas sistematicamente, e variáveis de topografia e características do solo foram medidas em 30 parcelas de 10×40 m, sendo 15 parcelas em cada fisionomia. A distribuição das espécies arbóreas foi espacialmente estruturada, e as características do solo diferiram entre as áreas de cerrado sentido restrito e FED, principalmente relacionadas à saturação de alumínio, saturação de bases e teores de fósforo. A saturação de alumínio aumentou em direção ao cerrado sentido restrito, enquanto a saturação de bases aumentou em direção à FED. A maioria das espécies arbóreas predominou em uma das fisionomias, como Callisthene major em cerrado sentido restrito e Anadenanthera colubrina em FED. Apenas 20% das espécies foram amplamente distribuídas em ambas as fisionomias ou, em poucos casos, restritas aos valores intermediários do gradiente de solo. Os resultados indicam um forte contraste de características do solo entre o cerrado sentido restrito e a FED, assim como uma transição acentuada e espacialmente organizada quanto à distribuição de espécies arbóreas.

Woody species distribution across a savanna-dry forest soil gradient in the Brazilian Cerrado

Abstract Although richness and distribution of woody species in the Cerrado physiognomies have been extensively studied, the shifts of woody species from savanna physiognomies to dry forests have not yet been addressed. Here, we investigate the effect of soil physical-chemical traits on the woody species turnover between adjacent cerrado stricto sensu and dry forest physiognomies. Woody species were surveyed, and soil and topographic variables measured, in 30 10×40 m plots systematically distributed, with 15 plots in each physiognomy. We found a spatially structured distribution of woody species, and differences of soil traits between cerrado stricto sensu and dry forest areas, mainly related to the aluminum saturation, base saturation, and available phosphorus. Aluminum saturation increased toward the savanna area, while base saturation increased toward the dry forest. Most woody species predominated in one physiognomy, such as Callisthene major in the cerrado stricto sensu and Anadenanthera colubrina in the dry forest. Only 20% of the species were widely distributed across both physiognomies or, not often, restricted to the intermediary values of the soil gradient. General results indicate that contrasting soil traits between cerrado stricto sensu and dry forest produce a strongly spatially organized and sharp transition in terms of species distribution between these physiognomies.

Resumo Embora a distribuição e a riqueza em espécies arbóreas nas fitofisionomias do Cerrado venham sendo bastante estudadas, a transição entre savanas e florestas deciduais ainda não foi abordada. Investigamos o efeito de características físico-químicas do solo sobre a distribuição de espécies arbóreas em região de contato entre cerrado sentido restrito e floresta estacional decidual (FED). As espécies arbóreas foram amostradas sistematicamente, e variáveis de topografia e características do solo foram medidas em 30 parcelas de 10×40 m, sendo 15 parcelas em cada fisionomia. A distribuição das espécies arbóreas foi espacialmente estruturada, e as características do solo diferiram entre as áreas de cerrado sentido restrito e FED, principalmente relacionadas à saturação de alumínio, saturação de bases e teores de fósforo. A saturação de alumínio aumentou em direção ao cerrado sentido restrito, enquanto a saturação de bases aumentou em direção à FED. A maioria das espécies arbóreas predominou em uma das fisionomias, como Callisthene major em cerrado sentido restrito e Anadenanthera colubrina em FED. Apenas 20% das espécies foram amplamente distribuídas em ambas as fisionomias ou, em poucos casos, restritas aos valores intermediários do gradiente de solo. Os resultados indicam um forte contraste de características do solo entre o cerrado sentido restrito e a FED, assim como uma transição acentuada e espacialmente organizada quanto à distribuição de espécies arbóreas.

Woody species distribution across a savanna-dry forest soil gradient in the Brazilian Cerrado / Distribuição de espécies arbóreas em gradiente de solo savana-floresta seca no Cerrado brasileiro

Abstract Although richness and distribution of woody species in the Cerrado physiognomies have been extensively studied, the shifts of woody species from savanna physiognomies to dry forests have not yet been addressed. Here, we investigate the effect of soil physical-chemical traits on the woody species turnover between adjacent cerrado stricto sensu and dry forest physiognomies. Woody species were surveyed, and soil and topographic variables measured, in 30 10×40 m plots systematically distributed, with 15 plots in each physiognomy. We found a spatially structured distribution of woody species, and differences of soil traits between cerrado stricto sensu and dry forest areas, mainly related to the aluminum saturation, base saturation, and available phosphorus. Aluminum saturation increased toward the savanna area, while base saturation increased toward the dry forest. Most woody species predominated in one physiognomy, such as Callisthene major in the cerrado stricto sensu and Anadenanthera colubrina in the dry forest. Only 20% of the species were widely distributed across both physiognomies or, not often, restricted to the intermediary values of the soil gradient. General results indicate that contrasting soil traits between cerrado stricto sensu and dry forest produce a strongly spatially organized and sharp transition in terms of species distribution between these physiognomies.

Resumo Embora a distribuição e a riqueza em espécies arbóreas nas fitofisionomias do Cerrado venham sendo bastante estudadas, a transição entre savanas e florestas deciduais ainda não foi abordada. Investigamos o efeito de características físico-químicas do solo sobre a distribuição de espécies arbóreas em região de contato entre cerrado sentido restrito e floresta estacional decidual (FED). As espécies arbóreas foram amostradas sistematicamente, e variáveis de topografia e características do solo foram medidas em 30 parcelas de 10×40 m, sendo 15 parcelas em cada fisionomia. A distribuição das espécies arbóreas foi espacialmente estruturada, e as características do solo diferiram entre as áreas de cerrado sentido restrito e FED, principalmente relacionadas à saturação de alumínio, saturação de bases e teores de fósforo. A saturação de alumínio aumentou em direção ao cerrado sentido restrito, enquanto a saturação de bases aumentou em direção à FED. A maioria das espécies arbóreas predominou em uma das fisionomias, como Callisthene major em cerrado sentido restrito e Anadenanthera colubrina em FED. Apenas 20% das espécies foram amplamente distribuídas em ambas as fisionomias ou, em poucos casos, restritas aos valores intermediários do gradiente de solo. Os resultados indicam um forte contraste de características do solo entre o cerrado sentido restrito e a FED, assim como uma transição acentuada e espacialmente organizada quanto à distribuição de espécies arbóreas.

Arbuscular Mycorrhizal Fungal Communities in the Roots of Maize Lines Contrasting for Al Tolerance Grown in Limed and Non-Limed Brazilian Oxisoil.

Aluminum (Al) toxicity is one of the greatest limitations to agriculture in acid soils, particularly in tropical regions. Arbuscular mycorrhizal fungi (AMF) can supply plants with nutrients and give protection against Al toxicity. The aim of this work was to evaluate the effects of soil liming (i.e., reducing Al saturation) on the AMF community composition and structure in the roots of maize lines contrasting for Al tolerance. To this end, we constructed four 18S rDNA cloning libraries from L3 (Al tolerant) and L22 (Al sensitive) maize lines grown in limed and non-limed soils. A total of 790 clones were sequenced, 69% belonging to the Glomeromycota phylum. The remaining sequences were from Ascomycota, which were more prominent in the limed soil, mainly in the L3 line. The most abundant AM fungal clones were related to the family Glomeraceae represented by the genera uncultured Glomus followed by Rhizophagus and Funneliformis. However, the most abundant operational taxonomic units with 27% of the Glomeromycota clones was affiliated to genus Racocetra. This genus was present in all the four libraries, but it was predominant in the non-limed soils, suggesting that Racocetra is tolerant to Al toxicity. Similarly, Acaulospora and Rhizophagus were also present mostly in both lines in non-limed soils. The community richness of AMF in the non-limed soils was higher than the limed soil for both lines. The results suggest that the soil Al saturation was the parameter that mostly influences the AMF species composition in the soils in this study.