With the combination of airborne Lidar and panchromatic images in 1981 and 2021, we investigated the canopy height structure of tropical forests in Menglun sub-reserve in the Xishuangbanna National Nature Reserve of Yunnan Province, and analyzed its relationship with environmental factors by using multiple regression tree (MRT) method. The results showed that forests in the Menglun sub-reserve could be clustered into seven types based on canopy height structures, with tropical rainforest, monsoon evergreen broad-leaved forest, secondary forest, and flood plain forest as the main types. The potential solar radiation, altitude, terrain profile curvature, slope and the brightness value of imageries in 1981 and 2021 were main factors that drove the classification. The tropical seasonal rainforest dominated by Pometia pinnata occupied the largest area in valley and low-land. The monsoon evergreen broad-leaved forest dominated by Castanopsis echinocarpa mainly distributed in the ridge and disturbed areas. The secondary forests had homogeneous canopy surface, which was significantly different from the primary forests. The activities of swidden agriculture about three decades ago had legacy impacts on the physiognomy of secondary forests.

ABSTRACTThe formation of three-dimensional ordered spatial patterns, which is essential for embryonic development, tissue regeneration, and cancer metastasis, is mainly guided by the chemical concentration gradient of morphogens. However, since no chemical concentration gradient has been observed in the early embryonic development (pre-implantation) of mammals, the pattern formation mechanism has been unsolved for a long time. During the second cell fate decision of mouse embryos, the inner cell mass (ICM) segregates into topographically regionalized epiblast (EPI) and primitive endoderm (PrE) layers. Here, we report that the segregation process of PrE/EPI precursors coincides with an emerged periodic expansion-contraction vibration of the blastocyst cavity, which induces phase transition in the ICM compartment to a higher fluidity state and generates directional tissue flows. By experiments and modeling, we demonstrate that the spatial segregation of PrE and EPI precursors is mediated by a “Brazil nut effect”-like viscous segregation mechanism in which PrE precursors with low affinity gradually migrate to the surface of ICM along with the tissue flow, while EPI precursors with high affinity remains inside ICM under cavity vibration. Artificially manipulation of the frequency and amplitude of cavity vibration could control the process of spatial separation as well as lineage specification of PrE/EPI. Furthermore, disruption of the cavity vibration in the initial stage after segregation could reverse the ICM cells back to a mixed state. Therefore, this study reveals a fundamental mechanism that guarantees the robustness of cell segregation and pattern formation without specific morphogens in early mammalian embryos. Our model also emphasizes a conserved function of cavity structure that widely exists in organisms as an energy reservoir and converter between different forms, such as chemical and mechanical energy.

2020年国家实行畜牧业全面减抗、禁抗,寻找到替抗物质对于畜牧业持续稳定发展至关重要.植物提取物因其具有的抗菌、抗氧化等作用成为研究重点,准确测定植物提取物含量至关重要.液相色谱-串联四极杆质谱(liquid chromatography tandem quadrupole-mass spectrometry,LC-MS)技术作为近年来前沿的分离分析检测技术被应用到很多行业.本文综述了近几年LC-MS对植物提取物含量的测定研究,以期为植物提取物作为替抗物质应用到畜牧业中,其用法用量的确定提供技术理论支撑,也为植物提取物含量测定标准建立提供参考.

As a new type of methane control agent, natural plant extract has been widely studied in recent years, but in vivo studies are few. This study was to investigate the effects of the dietary supplementation of 2 different polyphenols on the methane (CH4) emission and digestion metabolism in sheep. Ten healthy crossbred sheep (Dorper ♂ × small-tailed Han ♀; BW 60.0 ± 1.73 kg) were used in a change-over design. The sheep were fed the following 3 diets in the present study: the basal diet (CON) with no supplementation; the basal diet supplemented with 2 g mulberry leaf flavonoid (MLF) per day per sheep; the basal diet supplemented with 0.25 g resveratrol (RES) per day per sheep. Both MLF and RES reduced CH4 emission scaled to metabolic weight per kilogram of DMI and CO2 output scaled to metabolic weight, but the effect of RES was significant (P < 0.05). Both MLF and RES significantly improved apparent digestibility of DM, OM, NDF, ADF, and nitrogen, but the effect of RES was significant (P < 0.05). Both MLF and RES significantly improved ME (P < 0.05) and reduced energy losses in CH4 emission (P > 0.05). In conclusion, MLF and RES can improve the digestibility of nutrients, the utilization of nutrients and energy, and reduce CH4 emission, but they are not conducive to nitrogen retention.

The dispersal of many plants depends on transportation by birds as seed dispersers. The birds play an important role in long distance seed dispersal and may also affect seed germination. However, for plants who have many bird dispersers, the influence of dominant and non-dominant dispersers on retention time (dispersal distance) and germination remains poorly understood. In this study, we performed experiments with captive frugivorous birds and fruiting plant species to study the effects of dominant and non-dominant dispersers on seed retention time (SRT) and germination (seed germination percentage and germination speed). Our study showed a great interspecific variation in the effects of frugivorous birds on both SRT and germination. Some birds enhance the germination of a given plant species, but others do not. Generally, the dominant visitors improved the seed germination and performed longer seed retention time.

The cumulative environmental impact is one of the most important components in the environment research.The essence content of defining cumulative environmental impacts is put forward based on the review of the connotation including the cumulative environmental impacts sort and the concept's generation and development;the research in cumulative environmental impacts is conducted abroad for a long time and there are some problems,such as the concept inconsistency,the poor quantity of method and the lack of recognization.In China research in cumulative environmental impacts concentrates more on the analysis methods,but less on the definition and examples since 1990s.Then several analysis methods are classfied by the different application conditions.Especially,the research status of cumulative environmental impact assessment in water resource subject and the cumulative environmental impacts' characteristic in cascade hydropower exploitation are introduced in this paper.And four research trends are proposed.