Soil physicochemical and biological properties in soybean areas under no-till Systems in the Brazilian Cerrado.

No-till (NT) as a conservation practice aims to minimize soil disturbance and enhance soil sustainability. However, how NT practice affects soil physicochemical and biological properties in soybean areas remains unclear. This study selected 65 high-yielding soybean farms under a long-term NT system in the Brazilian Cerrado and collected soil samples at 0.0-0.10 m (L1), 0.10-0.20 m (L2) and 0.20-0.40 m (L3) depths. The effect of NT on soil properties and interactions with soybean productivities were assessed. Results showed that the average soybean yield of the study areas in the last three years was 4.13 Mg ha-1, with 26 areas presenting yields over 4.20 Mg ha-1. Most studied soil properties showed a depth stratification and were strongly concentrated in L1, except for S, Al3+ and aluminum saturation, which displayed lower surface and higher subsurface concentrations. Moreover, a high proportion of SOM is composed of light SOM fraction in areas of high soybean yield, with the average SOM values of 39.9, 27.8 and 19.6 g kg-1 in L1, L2 and L3, respectively. Soils under long-term NT present moderate values of enzyme activity compared with the relatively low values under conventional tillage system, especially 94 % of the plots have moderate values of activity of arylsulfatase enzymes. The data presented support the conclusion that NT system can enhance soil fertility and biological quality in soybean cultivation. Our results suggest that it is necessary to adopt NT practice because it allows increasing soybean productivity in Brazil without the need to increase the sown area, in addition to increasing productivity associated with an improvement in the agroecosystem quality, thus moving toward a more sustainable agriculture.

The AtMYB2 inhibits the formation of axillary meristem in Arabidopsis by repressing RAX1 gene under environmental stresses.

KEY MESSAGE: AtMYB2 protein represses the formation of axillary meristems in response to environmental stresses so that plants can undergo a shorter vegetative development stage under environmental stresses. Shoot branching is an important event determined by endogenous factors during the development of plants. The formation of axillary meristem is also significantly repressed by environmental stresses and the underlying mechanism is largely unknown. The REGULATOR OF AXILLARY MERISTEMS (RAX) genes encode the R2R3 MYB transcription factors that have been shown to regulate the formation of axillary meristems in Arabidopsis. The AtMYB2 is also a member of R2R3 MYB gene family whose expression is usually induced by the environmental stresses. In this study, our results showed that AtMYB2 protein plays a pivotal negative regulatory role in the formation of axillary meristem. AtMYB2 is mainly expressed in the leaf axils as that of RAX1. The environmental stresses can increase the expression of AtMYB2 protein which further inhibits the expression of RAX1 gene by binding to its promoter. Therefore, AtMYB2 protein represses the formation of axillary meristems in response to environmental stresses so that plants can undergo a shorter vegetative development stage under environmental stresses.

Patterns and controls of vegetation productivity and precipitation-use efficiency across Eurasian grasslands.

Elucidating aboveground net primary production (ANPP) and precipitation-use efficiency (PUE) spatial variations and mechanisms are essential for predicting how ecosystem functioning will respond to future climate change. However, a comprehensive recognition of spatial patterns of ANPP and PUE across continental scale is still lacking. Here, we integrated long-term GIMMS NDVI remote sensing, field survey ANPP and meteorological datasets to reveal the spatial variations and controls of ANPP and PUE across Eurasian grasslands for the first time. The results showed that the mean value of ANPP and PUE of Eurasian grasslands were 40.20 ± 0.40 g C m-2 yr-1 and 0.15 ± 0.01 g C m-2 mm-1, respectively. At the continental scale, the ANPP and PUE showed unimodal patterns along mean annual precipitation (MAP) and hydrothermal index (HT) gradients, while a piecewise linear pattern along mean annual temperature (MAT) gradients. The MAP exerted positive effect on the ANPP in desert and temperate grasslands, while negative effect on the ANPP in alpine grasslands. Conversely, the MAT negatively affected the ANPP in desert and temperate grasslands, while positively affected the ANPP in alpine grasslands. The results indicated that the hydrothermal conditions coupled with the transition of vegetation types and its different responses combinedly shaped the spatial patterns of ANPP and PUE in Eurasian grasslands. This study advanced our knowledge of the spatial variations of ANPP and PUE at continental scale, providing theoretical information for predicting productivity and water use changes of arid and semi-arid grasslands under climate change in the future.

Toxic elements in the stream sediments of an urbanized basin, Eastern China: urbanization greatly elevates their adverse biological effects.

The concentration of toxic elements (Hg, Cd, Cr, Cu, Pb, Zn, Ni and As) was measured in the sediments of the Qinhuai River in Eastern China along a rural to urban gradient. Multiple approaches were undertaken to evaluate the degree of enrichment and adverse biological effects of these elements. The results showed that the concentration of Hg, Cd, Zn, Cu and Pb increased exponentially from the agricultural headwater to the urbanized downstream, which reflects a severe anthropogenic influence. In addition, area-specific references, such as the local soil background (LSB) and upper continental crust (UCC) derived from the Yangtze craton, were more applicable for evaluating the enrichment of toxic elements in the Qinhuai River than was global UCC. In addition, Cd and Hg had the highest enrichment factor values (EF, with averages of 9.18 and 7.14, respectively); Zn, Pb and Cu had moderate EFs (averages from 1.52 to 2.40), while the average EFs of Ni, Cr and As were approximately equal to 1. Based on consensus-based sediment quality guidelines (SQGs), the contamination characteristics of all of the samples studied were associated with low to moderate priority of adverse biological effects (ABEs) in the rural upstream area, while it was associated with a high to moderate priority of ABEs in the urban sections of the Qinhuai River. Our results suggest that the adverse biological effects of elevated levels of toxic elements were strongly related to the degree of anthropogenic pollution.