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The rhizosphere harbors complex bacterial communities, which are critical for plant growth and health. Significant differences exist between bacterial communities in the rhizosphere and bulk soils, however, limited research has explored co-occurrence patterns, environmental adaptations, and assembly mechanisms of rhizosphere bacterial communities. Using 16S rRNA high-throughput sequencing, we investigated the taxonomic and phylogenetic diversity of bacterial communities in both rhizosphere and bulk soils from a rice cropping experimental system in China. In addition to investigating differences in bacterial composition, we examined co-occurrence patterns, estimated environmental breadth and phylogenetic signals, and analyzed community assembly processes in these environments. Significant differences were observed between rhizosphere composition and bulk soil (p

In recent years, the alternating occurrence of high temperature and waterlogging disasters in South China has seriously reduced the yield of single cropping rice. Studying the changes in anatomical structure of the rice root system could provide theoretical basis for understanding the mechanisms of high temperature and waterlogging stress. To examine interactions between temperature and waterlogging stress, an experiment was set up in a growth chamber consisting of two temperatures (moderate, 30&ndash, 34 &deg, C and high, 35&ndash, 38 &deg, C) with three depths of flooding (0&ndash, 5, 10 and 15 cm). Treatments commenced at the booting stage and lasted five days, after which all treatments were returned to a 0&ndash, 5 cm flooding depth and the same temperature regime. Observations were made immediately after cessation of treatments, then after 5, 10 and 20 d to test the effect of treatments on subsequent root anatomical development. The low-stress control (0&ndash, 5 cm, medium temperature) showed no change with time in aerenchyma area, thickness of the outer root, stele diameter, and the number nor diameter of xylem vessels. Root diameter and stele diameter under the high-stress control (0&ndash, 5 cm, high temperature) were decreased by 29.09% and 15.28%, respectively, at the booting stage, whereas the high stress control (15 cm, high temperature) affected only the vessel diameter, reducing it by 14.11% compared with that in the low-stress control (0&ndash, 5 cm, medium temperature). Compared to the high-stress control (0&ndash, 5 cm, high temperature), the interaction of high temperature and waterlogging stress alleviated the inhibiting effect of the changes in the root system, especially after the end of the stress. We thought that waterlogging could reduce the damage of high temperature on rice root growth. Low water depth waterlogging has little effect on rice root system and aerenchyma area root diameter at 0, 5, 10 and 20 d after the stress ended, and the thickness of the outer root, stele diameter and the number and diameter of vessels at 0 d under M15 (15 cm, medium temperature) had no significant difference compared with M5 (0&ndash, 5 cm, medium temperature). However, the increase in rice root diameter, stele diameter, thickness of the outer root cortex depth and vessel diameter were inhibited under high temperature stress at the booting stage. Root diameter and stele diameter under H5 (0&ndash, 5 cm, high temperature) were decreased by 29.09% and 15.28%, respectively, at the booting stage, whereas H15 (15 cm, high temperature) affected only the vessel diameter, reducing it by 14.11% compared with that in the M5. Compared to H5, the interaction of high temperature and waterlogging stress alleviated the inhibiting effect of the changes in the root system, especially after the end of the stress. We thought that waterlogging could lighten the damage of high temperature on rice root growth.

Link topology lifetime is not only an important metric to evaluate the dynamic characteristic of Ad Hoc network, but also is a direct and effective method to determine the time to perform Ad Hoc network measurement. This paper introduces the concept of “snapshot” to take the picture of link topology of three classical mobile mobility (i.e., RPGM, Freeway and Manhattan) respectively. Simulation results show that link topology snapshots method is not only a new idea to obtain the link topology lifetime of Ad Hoc network, but also the ratio of link connection, variety ratio of link topology and link topology lifetime curve could also be derived.

The dynamic nature of topology makes it challengeable to estimate link loss rates in mobile ad hoc network (MANET). Firstly, simulation results based on existing mobility models have the unrealistic movement scenarios which may not correctly reflect true MANET performance. Secondly, it is difficult to identify MANET topology under these models due to phantasmagoric movements. This paper presents the circle movement mobility model (CMMM), which is superior to previous models, and its topology identification algorithm to characterize the dynamic MANET topology. Moreover, we present a loss inferring algorithmic based on modeling and computational methodology of factor graphs, which iteratively updates the estimates of link losses. The inference is a process based on unicast back-to-back packets probes sent from a sender to pairs of receivers. Without internal nodes' cooperations, the inference can be calculated using only information recorded at the end hosts. NS2 simulations show that the proposed algorithms exhibit good performance.

The internal link performance inference is an increasingly important role in evaluating network. In this paper, we explore the use of end-to-end unicast traffic measurements, which consist of back-to-back packets sent from a sender to pairs of receivers, to estimate the delay probability distribution of mobile ad hoc network (MANET) internal links. Since the majority of existing mobility models for MANET do not provide realistic movement scenarios, we propose a novel mobility model based on circle movement. It can be applied to military patrol or search and rescue activities. Using this model, we can infer the stable topology within the identifiable time slot. We then extend the exiting inference algorithm of delay probability distribution in wired network for MANET delay tomography. NS2 simulations with different network scenarios validate the proposed models and inference arithmetic.