Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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WALRUS-paddy model for simulating the hydrological processes of lowland polders with paddy fields and pumping stations
No full textSimulating the rain-runoff process in lowland polder will lead to improvements to hydrological modeling of entire floodplain catchments. The lumped Wageningen Lowland Runoff Simulator (WALRUS) provides an efficient and reliable model for simulating the hydrological processes in lowland catchment with shallow groundwater. However, this model needs to be improved before being applied to Chinese polders, which have multiple land use types and pumping stations. This study proposes an improved version called WALRUS-paddy that accounts for the discharge from multi-sources, including drylands, paddy fields, residential areas, and water areas. A water management scheme is incorporated to control the irrigation and drainage operation in paddy rice fields and the groundwater flow between the paddy field and the adjacent dryland is considered. In addition, a new stage-discharge relation function is introduced to represent the discharge process of the polder with pumping stations and culverts. Then, the model is validated in the Jianwei polder of east China. The modeled results agree well with the observed discharge and show that the improved model can provide good estimates of the discharge in this polder district. Thus, the improved model is feasible and helpful for water resources management of Chinese polders. (C) 2016 Elsevier B.V. All rights reserved
Thermal stability of soil organic matter was affected by 23-yr maize and soybean continuous cultivation in northeast of China
No full textLong-term continuous cropping affects the biochemical quality of soil organic matter (SOM), but whether the effects are relevant with their thermal stability is less clear. In northeast China, long-term continuous cropping occurred frequently owing to higher yield and economic interest requirement. To verify the thermal stability properties of SOM affected by the long-term continuous cropping, the study focused on 23-yr continuous cultivated maize and soybean plots, where the effect of cropping is likely to be detected. Bulk soils sampled in 1991 and 2014 were studied by thermogravimetry and differential scanning calorimetry (DSC). The results showed typical bimodal peaks in DSC curve in bulk Mollisols. A labile fraction peak was observed at 354-366 A degrees C low-temperature zone and recalcitrant fraction one at high temperature of 430-438 A degrees C. Energy density (J mg(-1) OM) was greater in soybean plots compared to maize plots; in contrast, long-term continuous maize cultivation also increased energy density, in reverse in soybean plots after 23-yr cultivation. The DSC-T-50, temperature at which half of energy release occurred, typically showed larger responses to long-term cultivation than crop species. Results obtained support the hypothesis of a potential link between long-term continuous cropping and the thermal stability of SOM, and a correlation with crop species
The underlying basis for the trade-off between leaf size and leafing intensity
No full textRecent studies have reported a consistent trade-off between leaf size (mass) and leafing intensity (the number of leaves produced per unit of supporting stem tissue volume); however, a theoretical basis for this trade-off has not been described. We explore the mechanistic basis for this trade-off and assess the relationship in the light of other prominent theories for allometric biomass partitioning. We show algebraically how the allocation of mass to leaves versus stems and the density of stem tissue can potentially influence this trade-off. To assess these possible effects, we compared the relationship between leaf size and leafing intensity, expressed on both mass and volume basis, at the level of a single branch as well as the entire above-ground plant in 61 forbs over a 3-year period. Our results support the idea that the trade-off between leaf size and volume-based leafing intensity depends on both biomass investment (leaves vs. stems) and stem bulk density (mass vs. volume), whereas the trade-off between leaf size and mass-based leafing intensity only depends on the biomass investment. Similar exponents in the scaling of leaf mass vs. stem mass and stem mass vs. stem volume at branch and whole plant levels lead to similar trade-offs. An isometric trade-off between leaf size and volume-based leafing intensity is consistent with a constant biomass partitioning between leaves and stems as well as constant stem tissue density. Conversely, an allometric trade-off between leaf size and volume-based leafing intensity arises when biomass allocation is allometric and stem bulk density varies with plant size
Effects of Snow Cover on Ground Thermal Regime: A Case Study in Heilongjiang Province of China
No full textThe important effects of snow cover to ground thermal regime has received much attention of scholars during the past few decades. In the most of previous research, the effects were usually evaluated through the numerical models and many important results are found. However, less examples and insufficient data based on field measurements are available to show natural cases. In the present work, a typical case study in Mohe and Beijicun meteorological stations, which both are located in the most northern tip of China, is given to show the effects of snow cover on the ground thermal regime. The spatial (the ground profile) and time series analysis in the extremely snowy winter of 2012-2013 in Heilongjiang Province are also performed by contrast with those in the winter of 2011-2012 based on the measured data collected by 63 meteorological stations. Our results illustrate the positive (warmer) effect of snow cover on the ground temperature (GT) on the daily basis, the highest difference between GT and daily mean air temperature (DGAT) is as high as 32.35°C. Moreover, by the lag time analysis method it is found that the response time of GT from 0 cm to 20 cm ground depth to the alternate change of snow depth has 10 days lag, while at 40 cm depth the response of DGAT is not significant. This result is different from the previous research by modeling, in which the response depth of ground to the alteration of snow depth is far more than 40 cm
1990—2013年中国东北地区湿地生态系统格局演变遥感监测分析
No full text全球变化背景下,湿地生态系统极具敏感性和脆弱性。论文以Landsat TM/ETM+/OLI和国产环境卫星影像为数据源,重建1990、2000和2013年3期东北地区湿地生态系统分布格局;通过将东北地区划分为六大重要湿地分布区,探讨了区域天然湿地与人工湿地的分布和动态空间差异性及其驱动因素。结果表明:1990、2000、2013年东北地区湿地面积分别为11.75× 10~4、10.57×10~4、10.41×10~4km~2,湿地率分别为9.45%、8.50%、8.38%。湿地分布具有明显的地域特征,大兴安岭湿地区是最主要的天然湿地分布区,除水田外的人工湿地主要分布在辽河三角洲湿地区。1990—2013年东北地区湿地面积损失严重,损失面积为1.34×10~4 km~2,湿地相对损失率为11.4%,天然湿地相对损失率为14.3%,主要转化为耕地。三江平原湿地区的湿地率下降最明显,天然湿地损失面积为9 935.2 km~2;松嫩平原湿地区人工湿地面积增加最明显,增加1 141.9 km~2。气候变化影响叠加人类活动干扰背景下,沼泽湿地是对全球变化响应最显著的湿地类型,损失面积为16 091.4 km~2。气候要素和人文因子对湿地影响具有明显的空间差异性,人类活动的变化更加能够主导东北地区湿地面积的变化
施用有机肥对侵蚀黑土玉米苗期根内生细菌多样性的影响
No full text为了解根内生细菌群落结构在土壤侵蚀条件下的变化,明确有机肥施用对其多样性的影响,本研究采用LNA-PCR和454高通量测序技术相结合的方法对土壤表层剥离30 cm和施用有机肥处理的玉米苗期根内生细菌群落结构进行研究,以表层土没有剥离和单施化肥处理为对照.试验共获得37820条16S rDNA有效序列,主要分布在4个门35个纲214个属和782个OTU,其中,变形菌门、厚壁菌门、放线菌门和拟杆菌门为优势菌门,但不同样品各菌门分布比例存在差异.土壤侵蚀降低了玉米苗期根内生细菌群落多样性,但增施有机肥可以增加根内生细菌群落多样性,这种作用以表层土剥离30 cm处理表现得更为突出