International audiencePollen data from China for 6000 and 18,000 C-14 yr BP Were compiled and used to reconstruct palaeovegetation patterns, using complete taxon lists where possible and a biomization procedure that entailed the assignment of 645 pollen taxa to plant functional types. A set of 658 modern pollen samples spanning all biomes and regions provided a comprehensive test for this procedure and showed convincing agreement between reconstructed biomes and present natural vegetation types, both geographically and in terms of the elevation gradients in mountain regions of north-eastern and south-western China. The 6000 C-14 yr BP map confirms earlier studies in showing that the forest biomes in eastern China were systematically shifted northwards and extended westwards during the mid-Holocene. Tropical rain forest occurred on mainland China at sites characterized today by either tropical seasonal or broadleaved evergreen/warm mixed forest. Broadleaved evergreen/warm mixed forest occurred further north than today, and at higher elevation sites within the modern latitudinal range of this biome. The northern limit of temperate deciduous forest was shifted c. 800 km north relative to today. The 18,000 C-14 yr BP map shows that steppe and even desert vegetation extended to the modem coast of eastern China at the last glacial maximum, replacing today's temperate deciduous forest. Tropical forests were excluded from China and broadleaved evergreen/warm mixed forest had retreated to tropical latitudes, while taiga extended southwards to c. 43 degreesN

Drones of various shapes, sizes, and functionalities have emerged over the past few decades, and their civilian applications are becoming increasingly appealing. Flexible, low-cost, and high-resolution remote sensing systems that use drones as platforms are important for filling data gaps and supplementing the capabilities of crewed/manned aircraft and satellite remote sensing systems. Here, we refer to this growing remote sensing initiative as drone remote sensing and explain its unique advantages in forestry research and practices. Furthermore, we summarize the various approaches of drone remote sensing to surveying forests, mapping canopy gaps, measuring forest canopy height, tracking forest wildfires, and supporting intensive forest management. The benefits of drone remote sensing include low material and operational costs, flexible control of spatial and temporal resolution, high-intensity data collection, and the absence of risk to crews. The current forestry applications of drone remote sensing are still at an experimental stage, but they are expected to expand rapidly. To better guide the development of drone remote sensing for sustainable forestry, it is important to systematically and continuously conduct comparative studies to determine the appropriate drone remote sensing technologies for various forest conditions and/or forestry applications.

quantified vegetation attributes, its widespread use and popularity, especially in UAS applications, carry inherent risks of misuse with end users who received little to no remote sensing education. This article summarizes the progress of NDVI acquisition, highlights the areas of NDVI application, and addresses the critical problems and considerations in using NDVI. Detailed discussion mainly covers three aspects: atmospheric effect, saturation phenomenon, and sensor factors. The use of NDVI can be highly effective as long as its limitations and capabilities are understood. This consideration is particularly important to the UAS user community.

New data suggest that dramatic environmental change in the Western Loess Plateau of China corresponded with substantial changes in human demography ca. 4000 cal yr B.P. These data demonstrate that a rapid climatic transition from wet to dry led to an ecologically devastated period between 4090 and 3600 cal yr B.P. The sudden reduction in the number of archaeological sites during this period, namely a reduction in the total number of sites and a contraction of the areal distribution of sites, points to declining agricultural productivity associated with widespread aridification beginning at 4000 cal yr B.P.

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We present a record of monsoon variations for the early and middle Holocene that is inferred from the geochemistry of sediment cores from Ahung Co, a lake in central Tibet. The resolution of this record is better than 50 yr and the age model is derived from radiocarbon ages of terrestrial charcoal, which eliminates errors associated with the lake hard-water effect. We made down-core geochemical measurements of % carbonate, % organic carbon, C/N and d 13 C of bulk organic matter, d 13 C and d 18O of carbonate, and % dolomite. Proxy calibration and modern water-balance reconstruction show that these are proxies for lake depth and the amount of monsoon precipitation. We find that lake level and monsoon precipitation have been decreasing at Ahung Co since the early Holocene (¨7500 cal yr B.P.). Superimposed on this trend are rapid declines in monsoon rainfall at 7000 -7500 and 4700 cal yr B.P. and seven century-scale wet -dry oscillations. The cores do not contain sediment from the last¨4000 yr. Surface sediments from the lake accumulated during the 20th century, however. From this, we argue that lake levels have risen again recently following a late Holocene dry period.

The methane hydrate was formed in a pressure vessel 38 mm in id and 500 mm in length. Experimental works on gas production from the hydrate-bearing core by depressurization to 0.1, 0.93, and 1.93 MPa have been carried out. The hydrate reservoir simulator TOUGH-Fx/Hydrate was used to simulate the experimental gas production behavior, and the intrinsic hydration dissociation constant (K 0 ) fitted for the experimental data was on the order of 10 4 mol m -2 Pa -1 s -1 , which was one order lower than that of the bulk hydrate dissociation. The sensitivity analyses based on the simulator have been carried out, and the results suggested that the hydrate dissociation kinetics had a great effect on the gas production behavior for the laboratory-scale hydrate-bearing core. However for a field-scale hydrate reservoir, the flow ability dominated the gas production behavior and the effect of hydrate dissociation kinetics on the gas production behavior could be neglected.

This article investigates the gas production behavior from methane hydrate (MH) in porous sediment by injecting ethylene glycol (EG) solution with the different concentrations and the different injection rates in an one-dimensional experimental apparatus. The results suggest that the gas production process can be divided into the four stages: (1) the initial injection, (2) the EG diluteness, (3) the hydrate dissociation, and (4) the remained gas output. Nevertheless, the water production rate keeps nearly constant during the whole production process. The production efficiency is affected by both the EG concentration and the EG injection rate, and it reaches a maximum with the EG concentration of 60 wt %.