土壤-植物系统中光照与氮素的相互关系研究

运用盆栽试验,以莴笋为材料,在人工气候箱内进行研究,其结果表明:光照强度的变化,不仅会引起莴笋生物量和养分吸收量的改变,而且也将导致土壤养分状况的差异。不同肥力的3种紫色土,其养分含量受光照强度变化影响的状况是,NH+4-N和NO-3-N的含量均以大眼泥土>沙土>石骨子土,而碱解氮含量的变化则以沙土>石骨子土>大眼泥土。光照强度的变化亦影响氮肥的施用效果,在试验光强(80～320μmol/m2·s)范围内,光照愈强时莴笋产量愈高、且其同时对氮肥的需要量也相应由0.213g/pot增加到0.38g/pot。本试验的结果,较为完整地阐述了光照强度的变化与土壤养分、作物营养以及施肥之间的相互关系。

Phenolic Acids in Plant-Soil-Microbe System: A Review

Phenolic acids are very common compounds in pedosphere. Theobjective of this review was to summarize the current knowledge ofthe behaviors of phenolic acids in plant-soil microbe system. Whenphenolic acids originated form leaching, decomposition and exudationof living and dead plant tissues enter soils, they can reactphysiochemically with soil particle surfaces and/or incorporate intohumic matter. Phenolic acids desorbed from soil particle surfaces andremained in solution phase can be utilized by microbe as carbonsources and absorbed by plants.

Interaction of Pb and Cd in Soil－Water－Plant System and its Mechanism： I．Pb－Cd Interaction in Red Soil－Plant System

A study on the effect of Pb-Cd interaction on plant growth and on the chemistry of elements in plants was conducted under greenhouse condition with red soil-wetland rice system in different growth stage. The results showed that Pb-Cd interactions on growth and metal uptake varied with different growth stageS and chemical compounds added. The plant height and the root weight were markedly affected by Pb-Cd interiction in the young stage but not in the ripening stage of rice at the treatments of PbCl_2 and CdCl_2 added. However, the weight of rice straw in the ripening stage was significantly effected by Pb-Cd interaction with the treatments of Pb(OAc)_2 and CdCl_2. The chemistry of elements in plants also depended on Pb-Cd interaction in varying degrees on account of different plant parts and growth stage. It seems that Pb-Cd interaction occurred not only in roots but also in other parts of wetland rice.

Modeling Hydrothermal Transfer Processes in Permafrost Regions of Qinghai-Tibet Plateau in China

Hydrothermal processes are key components in permafrost dynamics; these processes are integral to global wanning. In this study the coupled heat and mass transfer model for （CoupModel） the soil-plant-atmosphere-system is applied in high-altitude permafrost regions and to model hydrothermal transfer processes in freeze-thaw cycles. Measured meteorological forcing and soil and vegetation properties are used in the CoupModel for the period from January 1, 2009 to December 31, 2012 at the Tanggula observation site in the Qinghai-Tibet Plateau. A 24-h time step is used in the model simulation. The results show that the simulated soil temperature and water content, as well as the frozen depth compare well with the measured data. The coefficient of determination （R2） is 0.97 for the mean soil temperature and 0.73 for the mean soil water content, respectively. The simulated soil heat flux at a depth of 0-20 cm is also consistent with the monitored data. An analysis is performed on the simulated hydrothermal transfer processes from the deep soil layer to the upper one during the freezing and thawing period. At the beginning of the freezing period, the water in the deep soil layer moves upward to the freezing front and releases heat during the freezing process. When the soil layer is completely frozen, there are no vertical water ex- changes between the soil layers, and the heat exchange process is controlled by the vertical soil temperature gradient. During the thaw- ing period, the downward heat process becomes more active due to increased incoming shortwave radiation at the ground surface. The melt water is quickly dissolved in the soil, and the soil water movement only changes in the shallow soil layer. Subsequently, the model was used to provide an evaluation of the potential response of the active layer to different scenarios of initial water content and climate warming at the Tanggula site. The results reveal that the soil water content and the organic layer provide protection against active layer deepening in summer, so climate warming will cause the permafrost active layer to become deeoer and permafrost degradation.

Hydraulic Resistance and Capacitance in the Soil-Plant System

In this paper, the hydraulic resistances and capacitances were evaluated. based on the development of non-(?) model of water flow in the soil-plant system and the simulating experiment work.The results show that the mean hydraulic resistance in the soil-plant system is 6.79×109 MPa·S·m-3; the mean hydraulic capacitance in the system is 5.2×107m3·MPa-1. In the components of hydraulic capacitance in the system, the capacitance in soil (81.8×10-6m3·MPa ) is the biggest and its variability with suii water potential is extremely strong, the capacitance in plant (5.3×10-7m3·MPa-1) is much smaller than that in soil, and the capacitance in shoots (15.5×10-7m3·2MPa-1) is bigger than that in roots (8.4×10-7m3·2MPa-1). An interesting result is that the capacitance in plant is almost equivalent to that in the soil-plant system.

Uptake and Recovery of Soil Nitrogen by Bryophytes and Vascular Plants in an Alpine Meadow

Due to their particular physiology and life history traits, bryophytes are critical in regulating biogeochemical cycles and functions in alpine ecosystem. Hence, it is crucial to investigate their nutrient utilization strategies in comparison with vascular plants and understand their responses to the variation of growing season caused by climate change. Firstly, this study testified whether or not bryophytes can absorb nitrogen(N) directly from soil through spiking three chemical forms of 15N stable isotope tracer. Secondly, with stronger ability of carbohydrates assimilation and photosynthesis, it is supposed that N utilization efficiency of vascular plants is significantly higher than that of bryophytes. However, the recovery of soil N by bryophytes can still compete with vascular plants due to their greater phytomass. Thirdly, resource acquisition may be varied from the change of growing season, during which N pulse can be manipulated with 15N tracer addition at different time. Both of bryophytes and vascular plants contain more N in a longer growing season, and prefer inorganic over organic N. Bryophytes assimilate more NH4+ than NO3– and amino acid, which can be indicated from the greater shoot excess 15N of bryophytes. However, vascular plants prefer to absorb NO3– for their developed root systems and vascular tissue. Concerning the uptake of three forms N by bryophytes, there is significant difference between two manipulated lengths of growing season. Furthermore, the capacity of bryophytes to tolerate N-pollution may be lower than currently appreciated, which indicates the effect of climate change on asynchronous variation of soil N pools with plant requirements.

Interactions between Soil Characteristics, Environmental Factors, and Plant Species Abundance: A Case Study in the Karst Mountains of Longhushan Nature Reserve, Southwest China

The ability to manage and restore plant communities in the face of human-induced landscape change may rely on our ability to predict how species respond to environmental variables.Understanding this response requires examining factors or their interactions that have influence on plant and resource availability.Our objective was to analyze the relationships between changes in plant abundance and the interaction among environmental habitat factors including soil, geological(rock type), and other environmental variables in the Longhushan karst mountains ecosystem.Species density and dominance were examined using ANOVA, ANCOVA,and Generalized Linear Models to establish the single or combined effects of these groups of factors.The results showed that trends in abundance were mainly affected by rock type(related to the percentage content of dolomite and calcite), soil characteristics in association with topography.Both plant indices were higher in dolomite dominated areas and varied positively with moisture, and elevation, but negatively with organic matter, while density also increased with slope degree.The results demonstrate that significant variations in species abundance was produced with the combination of variables from soil, geological, andenvironmental factors, suggesting their interaction influence on plants.We postulate that spatial variations in plant abundance in karst ecosystem depends on the carbonate rock type in addition to water and nutrient availability which are mainly controlled by topography and other factors such as soil texture and temperature.The study suggests that in karst areas carbonate rock type, in addition to local environmental variables, should be taken into account when analyzing the factors that have impact on plant communities.

Assessment of Heavy Metals Control from Soil and Vegetable Plants in Different Growing Systems

Heavy metals contents of soils and vegetable edible parts were studied at three crop systems （conventional, in conversion and organic） from seven traditional sites for vegetable growing in North-eastern Romania, during 2010. The main goal of the research was to find a correlation between the heavy metals contents and the crop systems. Determination of heavy metals was performed by atomic absorption spectrometry （AAS）, using a Shimadzu spectrophotometer, 6300 version, equipped with graphite furnace and autosampler. Heavy metals contents in the soils varied with the metals and locations, according to the crop system. The following experimental average contents were determined： Mn-262.03 mg kg1, Zn-45.60 mg kgq, Cu-28.53 mg kgl, Pb-5.20 mg kg1 and Cd-1.84 mg kg1. In vegetable edible parts, heavy metal varied with metals, sites and plant species, without a significant correlation with crop system. The trend of heavy metals in conventional and organic crops was Zn 〉 Cu 〉 Mn = Pb 〉 Cd, but in conversion crops it was Zn 〉 Mn = Pb 〉 Cu 〉 Cd. The highest content was of Zn （4.85 mg kg＇t）, at a cabbage crop in conversion. Cd was not detected in vegetable products and Pb was detected only in some vegetable samples. Research emphasized that heavy metals contents from soil and vegetable edible parts did not exceed the admitted maximum limits, according to Romanian and European Regulations. Final conclusion of research is that no correlations exist between crop systems and heavy metals contents from soil and plant.

Phosphorus Speciation and Nutrient Stoichiometry in the Soil-Plant System During Primary Ecological Restoration of Copper Mine Tailings

The effects of plant vegetation on phosphorus （P） speciation, pH, total carbon concentration, total nitrogen concentration, and alkaline phosphatase activities were investigated to explore the P uptake strategy of plants in low-P soil and to determine the nutrient stoichiometric ratio changes in the rhizosphere of plants （Imperata cylindrica, Miscanthus floridulus, Zoysia sinica, Artemisia lavandulaefolia, Indigofera pseudotinctoria, and Conyza canadensis） which had grown for approximately 15 years in copper mine tailings, East China. The results showed that the average pH values in the rhizosphere decreased by 0.06 1.37 compared with those in the non-rhizosphere. The alkaline phosphatase activities of the rhizosphere were significantly higher than those in the non-rhizosphere. The mean concentrations of aluminum （A1）- and iron （Fe）-bound P and Ca2-P （CaHPO4） in the rhizosphere of all plants were 5.4% to 87.7%, 49.2% to 214.2%, and 86.6% to 147.6% higher than those in the non-rhizosphere, respectively. Except for Cas-P （CasH2（PO4）6） and Cal0-P （Cal0（PO4）6（OH）2） in the rhizosphere, all kinds of inorganic P forms were negatively correlated with pH. Significant correlation was also observed among the concentrations of dominant forms of inorganic P, C, and N and alkaline phosphatase activities in the rhizosphere. Among the studied species, I. pseudotinetoria showed the most significant effect on enhancing soil available P concentration. The stoichiometric ratios of C：P and N：P were apparently higher in the rhizosphere than the non-rhizosphere, whereas these ratios were far below the ratios commonly observed in Chinese soils. These results indicated that the plant growth effectively affected P fractions possibly by changing pH, C and N concentrations, and alkaline phosphatase activity, in the rhizosphere in copper mine railings.

Mineral weathering and element cycling in soil-microorganism-plant system

Soil is an essential part of the critical zone,and soil-microbe-plant system serves as a key link among lithosphere,biosphere,atmosphere and hydrosphere.As one of the habitats with the richest biodiversity,soil plays a critical role in element biogeochemistry on the earth surface(weathered crust).Here we review the soil biological processes that are relevant to mineral weathering,element cycling,and transformation,with an emphasis on rock weathering mediated by soil microbes,plant root and the rhizosphere.

Contrasting responses of native and alien plant species to soil properties shed new light on the invasion of dune systems

Aims Among terrestrial ecosystems,coastal sandy dunes are particularly prone to alien plant invasion.Many studies related the invasion of dune habitats to anthropic causes,but less is known about the role of soil properties and plant traits in plant invasion.In this study,we tested the relationships between soil features and alien plant invasion in dune systems,focusing on the interplay between soil nutrients,soil salinity and plant functional traits.Methods Study sites were sandy barrier islands of the Marano and Grado lagoon(northern Adriatic Sea).One hundred plots(4 m×4 m)were selected within 10 areas according to the main habitats occurring along the ecological gradient of dune system(foredune,backdune and saltmarsh).In each plot,we recorded all plant species occurrence and abundance and we collected a soil core.For each soil sample,soil texture,conductivity(as proxy of soil salinity),organic carbon and nitrogen content were analyzed and related to the species number and cover of native and alien plants.Variation of main reproductive and vegetative functional traits among habitats was also analyzed for both alien and native species.Important Findings Soil properties were strongly related to overall plant diversity,by differently affecting alien and native species pools.In backdune,the most invaded habitat,a high soil conductivity limited the number of alien species,whereas the content of soil organic carbon increased along with alien plant abundance,suggesting also the occurrence of potential feedback processes between plant invasion and soil.We found a significant convergence between native and alien plant functional trait spectra only in backdune habitat,where environmental conditions ameliorate and plant competition increases.Our findings suggest that in harsh conditions only native specialized plants can thrive while at intermediate conditions,soil properties gradient acts in synergy with plant traits to curb/facilitate alien plant richness.

Soil Contamination due to E-Waste Disposal and Recycling Activities: A Review with Special Focus on China

Considering that even contaminated soils are a potential resource for agricultural production, it is essential to develop a set of cropping systems to allow a safe and sustainable agriculture on contaminated lands while avoiding any transfer of toxic trace elements to the food chain. In this review, three main strategies, i.e., phytoexclusion, phytostabilization, and phytoextraction, are proposed to establish cropping systems for production of edible and non-edible plants, and for extraction of elements for industrial use. For safe production of food crops, the selection of low-accumulating plants/cultivars and the application of soil amendments are of vital importance. Phytostabilization using non-food energy and fiber plants can provide additional renewable energy sources and economic benefit with minimum cost of agricultural measures. Phytoextracting trace elements （e.g., As, Cd, Ni, and Zn） using hyperaccumulator species is more suitable for slightly and moderately polluted sites, and phytomining of Ni from serpentine soils has shown a great potential to extract Ni-containing bio-ores of economic interests. We conclude that appropriate combinations of soil types, plant species/cultivars, and agronomic practices can restrict trace metal transfer to the food chain and/or extract energy and metals of industrial use and allow safe agricultural activities.

Transportation characteristics of δ^(13)C in the plants-soil-bedrock-cave system in Chongqing karst area

Here we use an analytical method to determine δ^13C in local plants and organic matter in the soils above Furong cave, Chong- qing, China. We also monitored d13C in dissolved inorganic carbon （DIC） of drip water, δ^13C of active deposits under the drip waters, and the concentration of air CO2 （PCO2）. Based on these, we preliminarily studied the transportation characteristics of stable carbon isotope （^13C） in cave system of the subtropical karst area. The average δ^13C value of 27 local plant samples, which belong to 16 families, was -32% and the weighted δ^13C for surface dry biomass was -33%0. We found that for 54 soil samples collected from 5 soil profiles, δ^13C of soil organic matters was -22%o, which could be attributed to the different trans- portation rates of stable carbon isotopes during the decomposition of plants and organic matters in soils. The relatively lighter 12C tended to transfer into gaseous CO2, which made the relatively heavier ^13C concentrated in the soils. On the basis of moni- toring of DIC- δ^13C in drip waters from July 2009 to June 2010, we found that values in winter months were heavier and values in summer months were lighter in general, the reason of which was that in summer months, both the temperature and the hu- midity were comparatively higher, resulted in more CO2 with lighter δ^13C generated from organic matters decomposition and plants respiration. The average DIC- δ^13C value was -11%o, about 11%o heavier than the δ^13C of organic matters in soils, which proved that part of DIC in cave drip water was sourced from dissolution of inorganic carbonate （host rock, with heavier δ^13C. As for the δ^13C of active deposits at five drip water sites in Furong cave, they had almost the same variation with relatively light values. In other words, these active speleothems were deposited at equilibrium conditions for isotopic fractionation. These results suggest that the carbon isotopic information of speleothems could be used to track the evolution of local vegetation in certain situations.

The uptake diversity of soil nitrogen nutrients by main plant species in Kobresia humilis alpine meadow on the Qinghai-Tibet Plateau

We studied the uptake of ammonium, nitrate, and a variety of amino acids by alpine plant species in the Kobresia humil alpine meadow ecosystem in situ. We examined the extent of niche separation in uptake of N source by different plant species in alpine communities, and investigated the contribution of symbiotically fixed N to the total N in alpine meadow. The results are （1） δ15N natural abundance values of 13 plant species lie between -2.680‰ and 5.169‰, and the scope is 7.849‰. （2） Le- guminous plants, such as Trigonella ruthenica, Gueldenstaedtia diversiffolia, and Oxytyopis ochrocephala, and non-legumi- nous plant Gentiana straminea uptake low amounts of 15N labeled ammonium, nitrate, glycine or aspartate in soil. （3） As far as the plant uptake of organic N is concerned, Kobresia humilis, Poa pratensis, and Gentiuna spathutifolta can effectively uptake organic nitrogen, and about 37%-40% of the nitrogen of these species comes from soil organic nitrogen sources （such as glycine and aspartate）. Stipa aliena can effectively uptake nitrate, and 60% of its nitrogen comes from soil nitrate. Potentilla anserina, Poa pratensis, and Thalictrum alpinum can effectively absorb ammonium in comparason to other plant species in the meadow, and about 25%-27% of the nitrogen in these plants comes from soil ammonium. （4） The contribution of leguminous fixed N to total N is 7.48%-9.26% in Kobresia humilis alpine meadow. （5） These data show many plant species of alpine meadow may effectively utilize dissolved organic nitrogen such as amino acids, and these plants have diverse ways to uptake soil nitrogen in alpine meadows. Based on the results we can partly explain why there are abundant biodiversities and how plants at alpine habitat utilize the limited soil N sources.

Fractionation and Soil-Plant Transfer of ^(241)Am in Different Soil Types

Monitoring the behavior of radioactive contaminants associated with military applications,nuclear power facilities,and interim storage of radioactive waste materials is of significant concern in radiological analysis.Four sequential extraction schemes(SES) for fractionation of ^(241)Am were compared using five different types of soils,Vertisol,Cambisol,Chromic Luvisol,Eutric Fluvisol,and mixed urban soil,collected from different parts of Bulgaria.The results for the exchangeable ^(241) Am were in a wide range and depended on the SES used.Soil ^(241)Am varied from 0.5%to 6%in the exchangeable phase,from 0.5%to 35%in the carbonate phase,from0.4%to 36%in the reducible phase(easily reducible and moderately reducible),from 3%to 17%in the oxidizable phase,and from10%to 50%in the residual phase.After 100 d of contamination,around 50%of soil ^(241)Am was permanently fixed in the residual phase.There was strong evidence that the preferable soil phase for ^(241) Am was the carbonate phase.The transfer factor of ^(241) Am in the soil-plant system depended on ^(241)Am in the easily oxidizable phase(fulvic acid(FA)+humic acid(HA) phase).These confirmed the applicability of the National Institute of Standards and Technology(NIST) sequential extraction scheme for fractionation of soil^(241) Am since it includes extraction of FA+HA phase and then the carbonate phase.

Populus euphratica, a Tolerant Model but Endangered Arborescent Species

Populus euphratica is a most tolerant arborescent species to abiotic stress. It can adapt to extreme conditions, ranging from flood to atmosphere extremely dry, hot from + 54 ℃ to - 45 ℃, and from normal soil to the soil with very high salt concentration ( to 2 ～5%) although being a non-halophyte. However, the natural stands of P. euphratica have been shrinking tremendously for the past decades and some populations are facing the fate of extinction. The preservation of existing resources should be carried out as a burning issue. In parallel, P. euphratica could be taken as a model plant to explore the molecular mechanism of abiotic-stress tolerance and to exploit its tolerant genes due to its smaller genome and easy molecular manipulation. The measures for preservation, germ-plasma exploitation, tolerance mechanism exploration and resource utilization were also discussed in this paper.