Plant productivity and nitrogen gas fluxes in a tallgrass prairie landscape

We explored relationships between plant productivity and annual fluxes of nitrogen (N₂) and nitrous oxide (N₂O) in a tallgrass prairie landscape in central Kansas. Our objective was to develop predictive relationships between these variables that could be used in conjunction with remote sensing information on plant productivity to produce large-area estimates of N gas fluxes. Our hypothesis was that there are inherent relationships between plant productivity and N gas fluxes in tallgrass prairie because both are controlled by water and N availability. The research was carried out as part of a multi-investigator project, the First ISLSCP Field Experiment (FIFE, ISLSCP = International Satellite Land Surface Climatology Program), directed toward the use of remote sensing to characterize land-atmosphere interactions. Fluxes of N₂ (denitrification) and N₂O were measured using soil core techniques. Estimates of annual flux were produced by temporal extrapolation of measured rates. Annual aboveground net primary productivity (ANPP) was estimated from measurements of the maximum standing crop of plant biomass. There were strong relationships between ANPP and N gas fluxes, and between a satellite remote sensing-based index of plant productivity (normalized difference vegetation index, NDVI) and gas fluxes. We used these relationships to convert images of NDVI into images of N gas fluxes for one 83 ha watershed and for the entire 15 by 15 km FIFE site. These images were used to compute mean landscape gas fluxes (0.62 g N m^-2 y^-1 for N₂, 0.66 g N m^-2 y^-1 for N₂O) and total N gas production for the two areas. Our flux and production values are useful for comparison with values produced by simulation models and site-specific studies, and for assessing the significance of N gas production to ecosystem and landscape scale processes related to nutrient cycling, water quality and atmospheric chemistry.     

Recoupling cross-scale interactions in tall fescue-invaded tallgrass prairie

Landscape Ecology - Vegetation quantity and quality influence the degree to which large grazers shape grassland structural heterogeneity. Invasive plants threaten the function of cross-scale...     

Disturbances in tallgrass prairie: local and regional effects on community heterogeneity

Community heterogeneity in tallgrass prairie was analyzed at regional and local levels to assess the effects of disturbances on community structure at different spatial scales. The sites were part of NASA's First ISLSCP Field Experiment (FIFE) in Kansas, and were located on grassland treatments that were undisturbed, and burned-only on Konze Prairie Research Natural Area, and grazed-only and grazed + burned on adjacent ranch land. Sites in grazed-only or grazed + burned treatments were less similar to each other, on a regional scale (15 × 15 km), than were burned-only or undisturbed sites. Grazing reduced the cover of dominant species, making space available for the establishment of immigrants from the region. Each site was different because of establishment by different species from the large regional species pool. At the local scale (0.1 ha), the most homogeneous treatments were those that were most heterogeneous at the regional scale. Undisturbed treatments at the local scale were the most heterogeneous compared to sites under other treatments. Therefore, regional responses to disturbances were more variable than local responses, and were not predictable from within-site analyses.     

A GIS-based index for relating landscape characteristics to potential nitrogen leaching to wetlands

We developed a spatially-explicit, quantitative Nitrogen Leaching Index to assess the potential for non-point source subsurface nitrogen pollution to wetlands. The index was based on the leaching potential of the watershed soils, the amount of nitrogen available for leaching, and the spatial position of nitrogen sources in the watershed. A raster or cell-based geographic information system (GIS) was used to estimate the necessary data inputs for calculating the index, such as soil hydrologic group, land use/soil type combination, groundwater residence time, and location of septic systems. The Total and Average Watershed Nitrogen Leaching Index (TWNLI and AWNLI) were calculated by summing and averaging, respectively, individual cell contributions over a watershed.Analysis of nine wetland watersheds in central New York state, USA, with mixed forest and agricultural land uses illustrated the use of the index for identifying and ranking wetlands with potential nitrogen pollution. Results showed that the spatial characteristics of a watershed potentially can effect subsurface nitrogen delivery to groundwater-dominated wetlands. The use of an index based on watershed soils, topography, and land use may be useful for assessing potential nitrogen pollution to wetlands at a regional scale.     

Landscape patterns of nitrogen mineralization and nitrification in southern Ohio hardwood forests

This study quantified nitrogen mineralization and nitrification potentials in soils of hardwood forests of southern Ohio at three spatial scales: (1) the regional scale, represented by four study areas of 90–120 ha separated by 3–65 km, (2) the local scale, represented by three contiguous watersheds within each study area, and (3) the topographic scale, represented by xeric, intermediate, and mesic sites within each watershed, as defined by a GIS-generated Integrated Moisture Index (IMI). Organic C, NO₃ pool size, net N mineralization, proportional nitrification, and net nitrification potentials all varied among study sites (i.e. at the regional scale). Using path analysis, we were able to construct scale-independent causal models explaining 30–35% of the variance in organic C and potential net N mineralization and 70% of the variance in potential net NO₃ production. Site- and scale-specific differences in geology and/or land use history among study sites were likely responsible for the variation not explained by the path analysis. At the local scale, there were significant variations in organic C and inorganic N pool sizes among watersheds within a study site in two of the four study sites. In addition, most parameters we measured varied significantly along the topographic gradient (i.e. with long-term soil moisture availability/IMI). Based on our results, scaling up models of nitrification from plot scale to the regional scale should be straightforward, whereas scaling up organic C storage and N mineralization will require incorporation of independent scaling paradigms at three (or more) spatial scales.     

Spatial variability in soil nitrogen dynamics after prescribed burning in Ohio mixed-oak forests

This study describes the results of the application of a single dormant season prescribed fire to two southern Ohio forest sites for the purposes of restoring the ecosystem functional properties that existed in these sites prior to major human intervention (clearcutting, fire suppression, and atmospheric deposition). Each forest site was composed of three contiguous watershed units, two of which were burned in April of 1996. The forest sites differed in soil pH and available litter mass prior to the fires, and in both sites pH and available inorganic N varied among landscape positions such that inorganic C increased with increasing longterm soil moisture potential (measured as the GIS-derived Integrated Moisture Index [IMI] developed for this region). The fire temperatures at 10 cm above the litter surface were generally 150–300°C, and 29–80% of the litter was consumed, depending on site and landscape position. Soil solution total inorganic N (TIN) present one month after the fires did not differ significantly from that present prior to the fires in either burned or unburned watersheds, but was consistently greater in mesic landscape positions than in more xeric ones. N mineralization potential and organic C content varied both among fires and landscape positions. At the site which burned at higher intensity, soil N mineralization and TIN were both decreased by fire. At the less intensely burned site, fire resulted in increased TIN in the soils from the more xeric landscape position, and greater soil organic C in soils from the intermediate soil moisture areas. Path analysis produced models for fire-induced changes in C and N dynamics capable of explaining 26–69% of the observed variation using combinations of landscape and fire behavior. Losses of N to volatilization from these single fires were generally < 1 kg N/ha, and thus could not be expected to ameliorate the effects of atmospheric N deposition in these sites.     

Vegetative growth, flowering and leaf nutrient concentration of boronia as affected by nitrogen level and form

Boronia (Boronia megastigma Nees, family Rutaceae) is an Australian woody shrub, producing strongly scented flowers at nodes. Increasing N levels from 0 to 25 mM in the nutrient solution increased the production of nodes, lateral shoots from these nodes and further nodes on these lateral shoots. With the same level of N, the order of number of node and lateral shoot production by N form was: combined NH₄⁺plus NO₃⁻ > NH₄⁺alone > NO₃⁻ alone. This increase in the number of nodes subsequently translated into increased number of axils initiating flower buds and then into fully developed flowers. However, increasing N levels decreased the percentage of flower buds developing to anthesis and individual flower weight. These decreases were attributed to continued vegetative growth during flower development. Increasing N levels increased the leaf N concentration with the concentration in the order NH₄⁺ + NO₃⁻ > NH₄⁺ > NO₃⁻. Nitrogen form did not affect the leaf tissue concentration of P, K⁺, Ca²⁺ and Mg²⁺. At lower N levels, the concentrations of these nutrients in the leaf tissue were higher and may have reached toxic levels, causing toxicity symptoms on leaves. At higher N levels, the concentrations of these nutrients were diluted due to increased growth and no toxicity symptoms were produced.     

不同种植年限设施菜田土壤硝态氮的累积与空间分布特性

为了解新乡市牧野区冬春茬蔬菜拉秧后,即夏季敞棚休闲期,硝态氮在各土层中的残留、空间分布状况及淋失风险,试验以农田为对照,采集了不同种植年限(2年、3年、16年和21年)设施菜田土壤样品进行测定分析。结果表明,设施菜田各土层硝态氮含量和累积量均高于农田,且二者均随种植年限的增加而增大,与种植年限间有极显著的线性正相关。各种植年限设施菜田中,随土层加深,硝态氮含量及累积量呈先降后增的趋势。其中,表层较高,40～60 cm最低,至80～100 cm达最大。虽然种植年限对表层土壤硝态氮的富集作用大于下层土壤,但这种由肥料表施而造成的硝态氮富集现象,会因降雨或灌水,形成在下层土体的空间分布重构。综上,随种植年限增加,设施菜田硝态氮淋失风险加剧,应控制氮肥投入量和灌水量。     

碳源和氮源对桑黄菌丝(Phellinus liteus)生长的影响

研究了影响桑黄菌丝生长的碳源和氮源。结果表明，桑黄菌丝生长的最适碳源是蔗糖，最适氮源是蛋白胨。     

Effects of site,landscape features,and fire regime on vegetation patterns in presettlement southern Wisconsin

The presettlement tree cover (1831–33) of 3 townships in a southern Wisconsin landscape was analyzed using original survey records. Four forest types were identified: closed forest, open forest, savanna, and prairie. Comparisons of vegetation types and landscape pattern were made between the east and west sides of the Pecatonica River, which bisects the landscape and could have acted as a natural fire barrier. West of the river, presettlement tree species richness and diversity were lower and trees were smaller in diameter and less dense than to the east. The major vegetation types to the west were prairie (42% of landscape) and savanna (40%), both fire-susceptible types. Prairie was more common on gentle slopes than on other landforms. To the east, the landscape was 70% forested (closed plus open forest). Here, prairie was more frequent on steep dry sites. These vegetation differences, including the contrasting landscape placement of prairie, are attributed to distinct site characteristics and to disturbance (fire) regimes, with the west likely having more frequent fires. In terms of the four vegetation types, the east landscape was more homogeneous, being dominated by closed forest (50%). West of the Pecatonica River, the landscape was more heterogeneous because of the high proportion of both prairie and savanna; however, in terms of flammability of vegetation, the west was essentially homogeneous (82% prairie plus savanna).     

肥料袋控缓释对草莓N素利用率及其产量的影响

以鬼怒甘草莓为试材,应用同位素15N示踪技术,研究肥料袋控缓释对设施促成栽培草莓氮素利用率及其产量的影响。结果表明:盆栽条件下,肥料袋控缓释处理比同剂量散施处理氮素利用率提高1倍以上,肥料回收率增加1.7倍,产量约增加0.5倍;在田间条件下,袋控缓释处理比同剂量分2次(定植与开花前)施用,总产量提高12%左右,但前期产量约下降10%。     

雄安新区化肥使用及氮磷盈余空间分布特征研究

近年来,随着白洋淀内源污染与点源污染逐渐得到控制,农业面源污染逐渐成为制约白洋淀水质改善的重要因素。改善白洋淀生态环境状况,加强农业面源污染防控至关重要。然而,当前对雄安新区农业面源污染的认识尚待提高,尤其需要加强对种植业化肥使用及其氮磷盈余空间分布特征研究。因此,本研究以雄安新区主要种植模式小麦—玉米为研究对象,采用农田养分平衡方法,分析2016年雄安新区小麦—玉米氮、磷养分输入、输出与盈余情况,为雄安新区农业面源污染防控提供科学依据。结果表明：(1)雄安新区农田氮磷养分的输入以化肥为主,输出以籽粒为主,总体化肥氮、磷投入水平为446.82 kg/hm²、84.23 kg/hm²,籽粒输出氮、磷养分水平为312.71 kg/hm²、42.79 kg/hm²;(2)雄安新区小麦—玉米农田氮磷养分均表现为盈余状况,且氮磷养分盈余与氮肥、磷肥投入极显著正相关;(3)雄安新区氮素、磷素盈余强度分别为273.74 kg/hm²、44.99 kg/hm²,不同县市氮...     

不同缓控释氮肥对设施菠菜生长及土壤环境的影响研究

根据天津武清地区设施菜田施肥状况,进行不同缓控释氮肥在设施菠菜上的试验探究,分析不同氮肥在菠菜的长势、产量、收益等方面的差异及对土壤环境的影响。结果表明,施用促根剂包膜尿素的菠菜667 m2产量和667 m2净收益最高。对于不同氮肥,无包膜尿素的硝态氮含量在土层表现上明显下移;有包膜尿素中,除高分子聚合物包膜尿素,其余尿素包膜中均有活性物质,起到增效作用,施用前期效果好,但高分子聚合物包膜尿素的肥效期长,施用后期还会继续释放。因此,选用适当缓控肥料非常必要。本研究对提高氮肥利用率与不同作物增产增效具有重要意义。     

CO2 enrichment of greenhouse tomatoes using a closed-loop heat storage: Effects of cultivar and nitrogen

Spring crops of soil-grown greenhouse tomatoes (Lycopersion Lycopersicum (L.) Karst ex. Farw cultivars MO and TR-VE 23) were provided with three levels of nitrogen addition with and without added CO₂. Using a closed-loop solar collection/storage system, crops could be CO₂-enriched for 76–77% of the daylight hours. CO₂ enrichment increased No. 1 grade fruit weight by 14 and 27% and by 4 and 18% for both cultivars in 1981 and 1982, respectively. Although the method and amount of nitrogen application differed between 1981 and 1982, a trend was seen in both years for low nitrogen treatments to produce a greater response to CO₂ enrichment than high nitrogen treatments. A trend was also seen in both years for low nitrogen treatment to depress yield and quality in the non-enriched house, but to have no effect in the enriched house. This trend was particularly apparent in the cultivar with lower vegetative vigor, which also responded more overall to CO₂ enrichment than the cultivar with greater vegetative vigor.     

改性石灰氮防治香蕉枯萎病及其恢复香蕉生产的效果

针对我国香蕉主产区蕉园土壤退化引起的土地生产力疲劳、毁灭性土传病害(香蕉枯萎病)泛滥、养分不均衡等问题,通过田间试验研究了改性石灰氮综合措施防治香蕉枯萎病的效果。结果表明,对照区的枯萎病发病率为67.58%,应用综合措施可以使发病率降低到13.75%,切断病原菌传播途径的灌溉水消毒措施对防治枯萎病有十分明显的效果;综合措施的实施使收获面积由对照的32.42%增加到86.25%,单株产量由24.4kg增加到26.9kg,单株实收增产10%以上,并改善了香蕉果实外观、营养和食用品质,增加了蕉农的产值和经济效益。由此可以认为,以改性石灰氮综合调控为主要内容的蕉园土壤质量保育措施可以有效的用于香蕉枯萎病的防治。     

Isolation,cloning, and expression of five genes related to nitrogen metabolism in peach (Prunus persica L. Batsch)

An optimal dosage of nitrogen has long been known to play important roles in governing nitrogen-use efficiency and improving the yield of plants. However, there is limited information on the isolation and expression profiles of genes related to nitrogen metabolism in peach (Prunus persica L. Batsch). This study isolated five genes involved in nitrogen metabolism and evaluated the effects of a single foliar application of urea on levels of expression of these genes in the leaves of ‘Dazhenbaochiyue’ peach. Cloning resulted in the isolation of 1,767, 1,236, 1,074, 1,758, and 2,721 nt-long cDNAs with full-length open reading frames encoding 588, 411, 357, 585, and 906 amino acids representing the asparagine synthetase (AS), glutamate dehydrogenase (GDH), glutamine synthetase (GS), nitrite reductase (NiR), and nitrate reductase (NR) genes in peach, respectively. An alignment of multiple amino acid sequences revealed that the AS, GDH, GS, and NR proteins in peach shared high levels of sequence conservation or identity at the amino acid level with their homologues in Arabidopsis thaliana and grapevine (Vitis vinifera). Based on analyses of expression of the five genes in peach leaves, we demonstrated that genes related to nitrogen metabolism responded to a foliar application of urea within 2 d. This was consistent with previous reports which indicated that leaves rapidly absorbed urea-nitrogen after foliar application. Foliar application of 0.5% (w/v) urea inhibited expression of GS and NiR, but increased expression of GDH, AS, and NR compared to control leaves. The different patterns of expression of the five genes in this study suggested that their expression might reflect their various roles in nitrogen metabolism, plant N status, and responses to weather conditions such as high light intensity, temperature, or humidity, all of which affect photosynthesis. These findings provide a basis for future functional analyses of these five genes in peach.     

基于光谱分析的库尔勒香梨叶片全氮含量估测研究

【目的】为了实现无损、实时、快速地监测香梨养分状况,【方法】利用SVC HR—768便携式光谱仪测定大田20 a树龄库尔勒香梨叶片的光谱反射率,并结合室内叶片氮素含量分析,采用逐步回归法对香梨叶片的全氮含量与原始光谱、一阶导数光谱、高光谱参数之间的关系进行分析。【结果】全氮含量与原始光谱在761 nm处构建的线性模型,调整决定系数R2值达到0.986;在1 564 nm处一阶微分光谱与全氮含量构建的线性模型,调整决定系数R2值为0.997;对于所选的高光谱特征变量,叶片全氮含量与红边位置变量(Dr)和红边面积变量(SDr)的相关关系极显著,并由此建立的线性模型的调整决定系数R2值均达到0.9以上,说明这些变量预测香梨叶片全氮含量具有可行性。【结论】对所构建的方程进行检验,确定了基于1 564 nm的一阶导数光谱模型为香梨叶片全氮含量的最佳预测模型。     

Root storage of nitrogen applied in autumn and its remobilization to new growth in spring of persimmon trees (Diospyros kaki cv. Fuyu)

This study was conducted to understand the effect of N supply in autumn on its uptake and distribution in tree parts and the utilization of reserve N the following year in persimmon trees (Diospyros kaki cv. Fuyu). The treated trees received 22.5-g N each for two successive years as a 3.5% urea solution from September 18 at 5-day intervals. Trees absorbed about 30% on average of the N applied in autumn. Sixty four to 83% of the N absorbed in autumn was in perennial parts, and 65–72% of that was in roots. Total N in perennial parts of the tree fertilized with N increased by over 4.28 g while leaf N changed little during senescence, indicating that the reserve N was constituted mostly by the N absorbed in autumn. Total N in the new growth was about the same as the amount of N declined in spring from perennial parts, indicating that there was little contribution by soil N to sustain new growth. Total dry weights of new growth the following year in a with-N tree were greater by over 34 g than those in a without-N tree.     

Relationship between expression of COX-2 and clinicopathological features in esophageal carcinoma

AIM:To examine COX-2 expression in esophageal carcinoma, and to study relationships between COX-2 expression and clinicopathological features and prognosis of esophageal carcinoma patients. METHODS:89 paraffin - embedded tissue samples from patients with esophageal carcinoma were collected, its clinicopathological features such as tumour differentiation, depth of invasion, length and site of the tumor, regional lymph node metastases, distant metastasis were recorded. Survival time of 81 cases were also recorded. By SP immunohistochemistry method, the expression of COX-2 in tumor samples was examined. RESULTS:COX-2 expression in esophageal carcinoma was markedly higher than that in nomal esophagus, the expression was higher in less differentiated and deeper invaded cases (P<0.05), but it had no correlations with other clinicopathological features such as age,sex, length and site of the tumor, regional lymph node metastases, and distant metastasis (P>0.05). Cases of esophageal carcinoma with lower COX-2 expression had longer survival time than those with higher COX-2 expression (P<0.01). CONCLUSIONS:COX-2 expression is higher in esophageal carcinoma than normal esophagus. COX-2 expression of esophageal carcinoma is higher in less differentiated and deeper invaded cases, but it has no correlation with age, sex, length and site of the tumor, regional lymph node metastases, and distant metastasis. Patients with lower COX-2 expression have longer survival time than those with higher COX-2 expression.