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Two sediment cores recovered from Dahu Swamp, which is located in eastern Nanling Mountains in south China, were selected for investigation of palaeoclimatic changes. Multi-proxy records of the two cores including lithological variation, organic carbon isotope ratio, dry bulk density, organic matter content, magnetic susceptibility, humification degree, median grain size and geochemical proxies reveal that during the last deglaciation three drier phases correspond to the Oldest, Older and Younger Dryas cooling events, and the intercalated two wetter phases synchronise with the Bølling and Allerød warming events. The Holocene Optimum, which was resulted from a strengthening of the East Asian (EA) summer monsoon, occurred in the early and mid Holocene (ca. 10-6 cal. ka BP). In the mid and late Holocene (ca. 6-3 cal. ka BP), a prevailing dry climate suggested a weakening of the EA summer monsoon. The general trend of Holocene climatic changes in this study agrees with the 258 N summer solar insolation, suggesting that orbitally induced insolation may have played an important role in the Holocene climate in the study region.

Zhong, W., Ma, Q. H., Xue, J. B., Zheng, Y. M., Cai, Y. & Ou, Y. J. 2009: Humification degrees of a lacustrine sedimentary sequence as an indicator of past climatic changes in the last c. 49 000 years in South China. Boreas, 10.1111/j.1502‐3885.2009.00119.x. ISSN 0300‐9483. An 860 cm long sediment core recovered from Dahu Swamp was used to test the potential of the degree of humification (expressed as the corrected absorbance values, HDcab) of lacustrine sediments as an indicator of past climatic changes in South China. The chronological sequence of this core was established using 10 AMS 14C dates and 10 conventional 14C dates and gives the bottom age of c. 48 800 cal. yr BP. Based on comparisons with multiproxy records, such as lithological variation, organic carbon isotope ratio, organic matter content and dry bulk density, we infer that the HDcab record is sensitive to local hydrological variations that are closely related to the East Asian (EA) summer monsoon precipitation. Higher HDcab values would indicate relatively drier conditions, suggesting a weakening of the EA summer monsoon and vice versa. Based on the HDcab, as well as other multiproxies, the climatic history in the last c. 49 000 years in the swamp area shows agreement with the Chinese stalagmite record and with the 25°N summer solar insolation, implying that orbitally induced insolation may have played a role in the last glacial period (LGP) climate in South China. Several millennial‐scale dry phases during the LGP show similarities with the stadials revealed by the ice core record in Greenland and from the Chinese cave stalagmites. Our study demonstrates that the HDcab of lacustrine sediments is a useful proxy of past climatic changes in South China.

No abstract

Wheat head detection can estimate various wheat traits, such as density, health, and the presence of wheat head. However, traditional detection methods have a huge array of problems, including low efficiency, strong subjectivity, and poor accuracy. In this paper, a method of wheat-head detection based on a deep neural network is proposed to enhance the speed and accuracy of detection. The YOLOv4 is taken as the basic network. The backbone part in the basic network is enhanced by adding dual spatial pyramid pooling (SPP) networks to improve the ability of feature learning and increase the receptive field of the convolutional network. Multilevel features are obtained by a multipath neck part using a top-down to bottom-up strategy. Finally, YOLOv3′s head structures are used to predict the boxes of wheat heads. For training images, some data augmentation technologies are used. The experimental results demonstrate that the proposed method has a significant advantage in accuracy and speed. The mean average precision of our method is 94.5%, and the detection speed is 71 FPS that can achieve the effect of real-time detection.