Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources
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植物应答缺铁胁迫的分子生理机制及其调控
No full text铁是植物生长发育中所必需的微量营养元素。虽然土壤中铁的丰度很高，但其生物有效性非常低，特别 是在碱性石灰性土壤上，高pH和高重碳酸盐含量严重降低了土壤中铁的有效性。因此如何有效地提高植物对 铁的利用效率及增强植物对缺铁胁迫的响应已成为目前该领域的研究热点。本文重点阐述了植物两种不同的铁 吸收机制，以及对缺铁胁迫的应答反应；对目前所发现的植物中调控缺铁胁迫的相关基因进行了全面的综述， 包括新发现的吞噬机理中所涉及的NRAMP基因；同时也介绍了感应铁缺乏的众多相关信号，包括植物激素、 气体信号分子及microRNAs等；此外，还提出利用铁吸收相关基因的转导、控制铁吸收相关因子以及各种农艺 措施的实施来提高植物铁的生物有效性从而有效缓解缺铁胁迫。最后对未来有关植物吞噬机制、铁缺乏感应信 号及改善植物铁营养新途径等研究方向作了初步展望。</p
地表覆盖对旱作玉米农田土壤氮素矿化的影响
No full text采用树脂芯方法研究了黄土高原旱作农田秸秆覆盖和地膜覆盖对0 ～ 20 cm 土层土壤氮素净矿化的影
响。结果表明: 不覆盖( 对照) 、秸秆覆盖和地膜覆盖3 个处理在玉米生育前期( 播前～ 六叶期) 表现为土壤氮素净固
持，净固持量分别为53．7、52．7、56．7 mg·kg－1，六叶期之后表现为氮素净矿化，净矿化量分别为26．3、31．8、13．7
mg·kg－1 ; 综合两个生育阶段从全生育期看，3 个处理土壤氮素矿化均表现为净固持，矿质氮净固持量分别为27．4，
20．9 mg·kg－1和43．0 mg·kg－1。从不同覆盖处理看，秸秆覆盖会显著增加土壤氮素净矿化量和氮净矿化速率，地膜
覆盖虽然有利于增加土壤温度和水分含量，但并没有显著改变土壤氮净矿化量和氮净矿化速率，这一结果间接证明
地膜覆盖并不会显著影响土壤有机质矿化。研究还发现，在本试验条件下当田间土壤温度在22℃ ～ 25℃、土壤含水
量在20%左右时有利于土壤氮素矿化，该条件下净矿化速率较高，且干湿交替有利于矿化。</p
Effects of rhizosphere interactions of grass interspecies on the soil microbial properties during the natural succession in the Loess Plateau
No full textNatural vegetation succession is a process of interactions between plants and various environmental factors. The dynamics of soil microbes during successional stages have been intensively explored in the past two decades. The effect of rhizosphere interactions of interspecies on microbial properties, however, has received less attention. During the early stage of succession on a Loess Plateau soil from China, we investigated microbial properties in the rhizospheres of three dominant grass species: Artemisia capillaris, Artemisia sacrorum and Stipa bungeana. Experiments with monocultured and polycultured potted plants were designed to determine the effects of rhizosphere interactions on plant growth and soil microbial properties. The results showed that root biomass, shoot biomass, plant height, microbial biomass carbon (C), microbial biomass nitrogen (N), invertase and urease activities, Gram-negative and Gram-positive bacteria were significantly higher for A. capillaris than for A. sacrorinn and S. bungeana in both monocultures and polycultures. Lower root biomass, shoot biomass, plant height, microbial biomass C, microbial biomass N, invertase and alkaline phosphatase activities, and levels of microbial phospholipid-derived fatty acids in polycultures relative to the monocultures indicated that rhizosphere interactions led to lower plant growth and soil microbial activities. Our study suggests that rhizosphere interactions had a significant effect on the microbial properties of plant rhizospheres. The advantage of A. capillaris over A. sacrorum and S. bungeana in growth characteristics and rhizosphere microbial conditions is likely responsible for the dominance of A. capillaris in the early stage of succession in abandoned cropland on the Loess Plateau
Soil water and root distribution of apple tree (Malus pumila Mill) stands in relation to stand age and rainwater collection and infiltration system (RWCI) in a hilly region of the Loess Plateau, China
No full textSoil water status and fine root distribution is the basis of implementing water management in semiarid rain-fed orchards. Exploitation of rainwater is an effective avenue for alleviating water scarcity in semiarid regions since ground water is generally unavailable there. Through the method of space-for-time substitution, we investigated the soil moisture and root distribution along a range of stand ages (6, 9, 12, 18 and 21 years) in rain-fed apple (Malus pumila Mill) orchards and the effects of rainwater collection and infiltration systems (RWCI) on root-zone soil water and fine root distributions in matures apple orchards (21 years) in the semiarid Loess Plateau of China. The results showed that the mean soil moisture content (SMC) in the shallow layer ( 2 m) was higher than shallow soil layers ( 8 m in plantations > 12 years old. Dry root weight density (RWD) decreased sharply with depth, but densities at each depth were greater in older stands. The RWCI system significantly increased SMCs from the surface down to the maximum rainfall infiltration depth (MRID) (2 m depth) (P < 0.05), especially in the 0.2-1 m soil layer. Further, we found that apple tree water requirements could be sustainably met when RWCI system and a low-volume of irrigation water was applied. The distribution of root system was greatly affected by the RWCI system, which led to higher root densities close to the wetted area in the shallow soil layers (2 m soil depth) under RWCI system, down to a depth of 3 m in the soil. Overall, the application of RWCI system could be an effective water management strategy for providing sustainable water resources for semiarid orchards
Assessing response of sediment load variation to climate change and human activities with six different approaches
No full textUnderstanding the relative contributions of climate change and human activities to variations in sediment load is of great importance for regional soil, and river basin management. Considerable studies have investigated spatial temporal variation of sediment load within the Loess Plateau; however, contradictory findings exist among methods used. This study systematically reviewed six quantitative methods: simple linear regression, double mass curve, sediment identity factor analysis, dam-sedimentation based method, the Sediment Delivery Distributed (SEDD) model, and the Soil Water Assessment Tool (SWAT) model. The calculation procedures and merits for each method were systematically explained. A case study in the Huangfuchuan watershed on the northern Loess Plateau has been undertaken. The results showed that sediment load had been reduced by 70.5% during the changing period from 1990 to 2012 compared to that of the baseline period from 1955 to 1989. Human activities accounted for an average of 93.6 +/- 4.1% of the total decline in sediment load, whereas climate change contributed 6.4 +/- 4.1%. Five methods produced similar estimates, but the linear regression yielded relatively different results. The results of this study provide a good reference for assessing the effects of climate change and human activities on sediment load variation by using different methods. (C) 2018 Published by Elsevier B.V
Successful field cultivation of moss biocrusts on disturbed soil surfaces in the short term
No full textAims The artificial cultivation of biocrusts may represent a new low-cost and highly efficient solution to erosion control. However, establishment under varying field environmental conditions is understudied. We tested a variety of methods, arriving at a set of technical recommendations for rapid establishment of moss biocrusts on disturbed slopes, and the industrialization of this process. Methods In multiple field experiments, aimed at moss biocrust cultivation and establishment, we considered the following factors: nutrient solutions (control and weekly addition); water-retaining agent (control and addition); plant growth regulator (control and biweekly addition); shading (0, 50%, 70% and 90%); dispersal method (broadcast and spray application). In all cases, we initially inoculated soils with 700 g/m(2) of moss biocrust materials. We monitored dynamic changes of the coverage and density of moss biocrusts during the cultivation period, and their biomass at the end. Results We successfully cultured moss biocrusts in a field setting in as little as two months. Specifically, we found:(1) Regardless of the dispersal method, the nutrient solutions and some degree of shading both increased the coverage, plant density and biomass of moss biocrusts, whereas the water-retaining agent and plant growth regulator had little influence on these parameters. The shading treatments improved the survival rates of moss biocrusts, with the shade rating of 70% exhibiting the best performance. Further, the nutrient solutions had a more positive effect under shaded conditions. (2) The growth of mosses dispersed in the fall exceeded that of mosses dispersed in the summer. (3) Under both dispersal techniques, the maximal coverage of the moss biocrusts exceeded 90%, and the maximal plant density of moss biocrusts reached 120 stems/cm(2)under broadcast dispersal, and 150 stems/cm(2), under spray dispersal. Conclusions The rapid restoration of moss biocrusts can best be achieved by spray-dispersal or broadcast-dispersal, while also applying Hoagland solution to supply nutrients and maintaining soil moisture at 15-25%. Fall inoculation appears more likely to lead to better moss establishment, in fact, high moss mortality occurred in summer unless shading was used. We have some evidence, observational in fall, and experimental in summer, that moderate shading favors establishment. This technique could feasibly be up scaled and adopted to restore some ecological functions on various types of engineered disturbed surfaces. Over a longer period, the survivorship, succession and sustainability of artificial moss biocrusts should be explored specifically
Changes in fine root biomass of Picea abies forests: predicting the potential impacts of climate change
No full textAims The impact of global warming on belowground processes, especially on fine root production, is poorly understood in comparison with its aboveground counterpart. Methods Here, we compiled 227 measurements to assess the influence of temperature and precipitation on fine root biomass of Norway spruce (Picea abies [L.] Karst) forest ecosystems in the Eurasia boreal region. Important Findings We found that fine root biomass decreased significantly with latitudes. There was a biomass increase of 0.63 Mg ha(-1) and 0.32 Mg ha(-1) for fine roots <2 and <1 mm in diameter, respectively, with 1 degrees C increase of mean annual temperature. There was an increase of 0.5 and 0.1 Mg ha(-1) per 100 mm year(-1) precipitation for the two size classes of fine roots. If the adaption of root production can match the pace of global warming and water is not a limiting factor for plant growth, fine root biomass would be expected to increase by 40-140% in response to the predicted increase in temperature (3-10 degrees C) over the next century. Our analyses highlighted the strongly positive influences of temperature and precipitation on belowground function, suggesting that predicted future climate change could substantially enhance belowground biomass in the boreal region where the greatest warming is anticipated. This potential increase of belowground biomass, coupled with aboveground biomass, may provide a better understanding of climate-ecosystem feedbacks
Melatonin Mitigates Salt Stress in Wheat Seedlings by Modulating Polyamine Metabolism
No full textMelatonin, a small molecular weight indoleamine molecule, is involved in various biological processes and responses to environmental cues in plants. However, its function in abiotic stress response and the underlying mechanisms is less clear. In this study, we investigated the effect of melatonin on wheat seedlings growth under salt stress condition. Exogenous melatonin pretreatment partially mitigated the salt-induced inhibition of whole-plant growth as judged from shoot dry weight, IAA content, leaf photosynthesis rate, maximum photochemistry efficiency of photosystem II, and chlorophyll. The mitigation was also observed in reduced accumulation of H2O2 in melatonin-pretreated wheat seedlings exposed to salt stress. Exogenous melatonin increased endogenous melatonin content by evaluating the levels of TaSNAT transcript, which encodes a key regulatory enzyme in the melatonin biosynthetic pathway. Furthermore, melatonin increased polyamine contents by accelerating the metabolic flow from the precursor amino acids arginine and methionine to polyamines; melatonin also decreased the degradation of salt-induced polyamines. Taken together, these results provide the evidence that melatonin mitigates salt stress mainly through its regulation on polyamine metabolism of wheat seedlings
Soil water storage compensation potential of herbaceous energy crops in semi-arid region (vol 223, pg 41, 2018)
No full textThe Temporal-Spatial Characteristics of Drought in the Loess Plateau Using the Remote-Sensed TRMM Precipitation Data from 1998 to 2014
No full textRainfall gauges are always sparse in the arid and semi-arid areas of Northwest China, which makes it difficult to precisely study the characteristics of drought at a large scale in this region and similar areas. This study used the TRMM (The Tropical Rainfall Measuring Mission) multi-satellite precipitation data to study the spatial-temporal evolution of drought in the Loess Plateau based on the SPI (Standardized Precipitation Index) drought index for the period of 1998-2014. The results indicate that the monthly TRMM precipitation data are well matched with the observed precipitation, indicating that this remotely sensed data set can be reliably used to calculate the SPI drought index. Based on the study findings, the average precipitation in the Loess Plateau is showing a significant increasing trend at the rate of 4.46 mm/year. From the spatial perspective, the average annual precipitation in the Southeast is generally greater than that in the Northwest. However, the annual precipitation in the Southeast area is showing a decreasing trend, whereas, the annual precipitation in the northwest areas is showing an increasing trend. Through the SPI analysis, the 3-month SPI and 12-month SPI were both showing an increasing trend, which indicates that the drought severity in the Loess Plateau was a generally declining trend at a seasonal to annual time scale. From the spatial perspective, the SPI values in the Central and Northwest of the Loess Plateau were significantly increasing, whereas, the SPI values in the southern area of the Loess Plateau were slightly decreasing. From the seasonal characteristics, the high-risk area for drought in the spring was concentrated in the northeast and southwest part, and in the summer and autumn, the high-risk area was transferred to the south part. Through this study, it is concluded that the Loess Plateau was likely getting wetter during the time period since the Grain-for-Green Project (1999-2012) was implemented, which replaced much farmland with forestry. This is a positive signal for vegetation recovery and ecological restoration in the near future