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1.
Jansson  Åsa  Folke  Carl  Langaas  Sindre 《Landscape Ecology》1998,13(4):249-262
We estimate the nitrogen retention capacity of natural wetlands in the 1.7 million km2 Baltic Sea drainage basin, using a wetland GIS data base. There are approximately 138,000 km2 of wetlands (bogs and fens) in the Baltic Sea drainage basin, corresponding to 8% of the area. The input of nitrogen to natural wetlands from atmospheric deposition was estimated to 55,000–161,000 ton y1. A map of the deposition of both wet and dry nitrogen is presented. The input from the human population was estimated to 255,000 ton y1 in terms of excretory release in processed sewage water. There may also be leakage from forests and agricultural land into the wetlands. Due to lack of data on hydrology and topography, such potential nitrogen sources are not accounted for here. The capacity of the wetlands to retain the atmospheric deposition of nitrogen was estimated to 34,000–99,000 ton y1. The potential retention by wetlands was estimated to 57,000–145,000 ton y1 when the nitrogen input from the human population was added. If drained wetlands were to be restored and their area added to the present wetland area, the nitrogen retention capacity was estimated to increase to 196,000–261,000 ton y1. Our results indicate that existing natural wetlands in the Baltic Sea drainage basin annually can retain an amount of nitrogen which corresponds to about 5–13% of annual total (natural and anthropogenic) nitrogen emissions entering the Baltic Sea. The ecosystem retention service performed by wetlands accounts for a substantial nitrogen removal, thereby reducing the eutrophication of the Baltic Sea.  相似文献   

2.
黄土高原成龄富士苹果园土壤养分含量标准值研究   总被引：3，自引：0，他引：3  
2012-2013年,对黄土高原12个主产县区108个典型富士果园养分状况调查分析。结果表明：果园土壤有机质、全氮、全磷、全钾含量分别为11.9、0.63、1.12和13.7 g · kg-1,有效氮、有效磷、有效钾、有效钙、有效镁、有效锌和有效铁含量分别为77.7、26.9、259.7、4 681、121.3、1.24和7.89 mg · kg-1。制定了黄土高原成龄富士苹果园土壤养分含量标准值。土壤养分状况特征为：有机质偏低,全氮、全磷和全钾等全素养分相对适宜,但有效养分偏低;全素养分含量变异较小,有效养分含量变异较大;大量元素变异较小,微量元素变异较大;地域和深度分布不均衡问题较为突出。不同产区间,延安和洛川土壤养分水平较低,分别有9个和5个养分因子处于低值和缺乏水平;而河南陕县养分水平较佳,各养分因子均处于适宜值以上水平。今后果园土壤管理的重点是,因地制宜着力提高土壤有机质和有效养分的含量,并注意适度深施肥,提高20 ~ 60 cm土层的有效养分含量。  相似文献   

3.
Summary

Single and combined effects of three planting dates and three plant densities on nitrogen uptake and nitrogen harvest by Brussels sprouts (Brassica olerácea var. gemmifera) were studied in field experiments. The total amount of nitrogen taken up by the crop at harvest ranged between 220 and 325 kg ha–1. Although final crop dry matter decreased, total nitrogen uptake was not lower when planting was delayed. This resulted in increased nitrogen concentrations both in the total crop and in the harvested product. Forty to fifty per cent of the nitrogen taken up by the harvest was removed from the field with the product. Within the range of 2.7 to 4.4 plants per m2, plant density had no effect on final nitrogen uptake nor on the amount of nitrogen harvested with the product. The results indicate that nitrogen fertilizer recommendations should take planting date into account, because with delayed planting less dry matter will be accumulated with a corresponding lower nitrogen requirement. There was no interaction of effects of planting date and plant density on nitrogen uptake.  相似文献   

4.
Mander  Ülo  Kull  Ain  Kuusemets  Valdo 《Landscape Ecology》2000,15(3):187-199
Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO4 and organic matter (after BOD5) decreased from 25.9 to 5.1, 0.32 to 0.13, 78 to 48, and 7.4 to 3.5 kg ha–1 yr–1, respectively. The most significant decreases occurred in agricultural subcatchments while the changes were insignificant in the forested upper course catchment. A simple empirical model which incorporates land-use pattern, fertilization intensity, soil parameters and water discharge accurately described the variations of total-N and total-P runoff in both the whole catchment and its agricultural subcatchments (R 2 varies from 0.95–0.99 for N to 0.49–0.93 for P). In small agricultural subcatchments the rate of fertilization is found the most important factor for nitrogen runoff, whereas in larger mosaic watersheds land use pattern plays the main role. Seven alternative scenarios compiled on the base of the empirical model allow to forecast potential nitrogen and phosphorus losses from the catchment. This information can be used in further landscape and regional planning of the whole region.  相似文献   

5.
The objective of this PhD project was to investigate the nutrient translocation associated with the mulch from the grass alley to the tree strip. Therefore, a historical, approved 40-year fertiliser trial with apple cv. ‘Gloster’ on M9 rootstock at a spacing of 4 m?×?1.5?m was employed at Klein-Altendorf Research Centre, University of Bonn, Germany, which comprised mineral nutrition (1?t/ha??CaO? $ + $ ?NPK), an organic plot (10?t??FM/ha pig manure) and an unfertilised plot as control. Grass alleys were mowed 5?× in 1995 and 3?× in 1996 as commonly practised in fruit orchards; foil was spread on the tree strips to capture the biomass transferred with the mulching. Overall, ca.??60% of the grass mulch dry matter (mowed at 2?cm height) remained in the grass alleyway, while ca.??40% was translocated to the tree strips, which amounted to 550?kg??DM (Dry Matter) in the unfertilised plot and 800?kg??DM/ha/year in both fertilised plots with the five mulches in the wet year 1995. Grass mulch contained 2–3%??N and 2.2–2.9%??K in the unfertilised control plot or 2.1–3.9%??N and 2.7–4.1%??K on per leaf dry matter in both the inorganic NPK and organically fertilised plot; the nitrogen content of the grass mulch increased during the growing season in the wet year 1995, but remained low and constant at 2.5%??N in the dry year 1996. By contrast, calcium was decreased from 0.5–0.7%??Ca in the unfertilised plot to 0.3–0.6%??Ca in the organic plot. Overall, 25–50% of the grass mulch was translocated from the grass alleys (ca. 4,000 m2) into the tree strips, representing an organic fertilisation of 10–25?kg??N, 2–4?kg??P, 15–25?kg??K, 3–5?kg??Ca and 1–2?kg??Mg per hectare and year. This would theoretically be equivalent to ca 50% supply of??N,??P and??K and??10% of calcium as required nutrients by fruit trees depending on rate of nutrient availability. Its subsequent partial availability reported of 54%??N within??90 days after mulching and large nutrient content are discussed with respect to the low nutrient content in leaves dropped from the fruit trees in the autumn, where the nutrients had been previously translocated into the woody perennial parts of the tree. This nutrient cycling should be integrated in environmental-friendly sustainable fertilisation strategies for fruit orchards.  相似文献   

6.
Summary

This study addresses vegetative growth and the uptake of nutrients and their accumulation in the vegetative and reproductive tissues of pepino (Solanum muricatum Ait.). The study was conducted in soilless plastic house conditions, with a planting density equivalent to 25.000 plants ha–1 during two seasons (1997–98 and 1998–99). The plants were sampled, fractionated into leaves, stems, fruits and roots, then dried and weighed and the macronutrient content was analysed every 30.d for 300.d after transplanting. The yield obtained was 2.kg of fruit per plant, which is 30% of the total dry weight. The relative growth rate (RGR) ranged from 0.0028 to 0.0451.d–1. The highest N, K, Ca and Mg concentrations were recorded in the leaves, and the highest P concentration in the roots. The nutrient accumulation of this yield was 10.64, 1.12, 16.06, 10.0 and 1.58.g of N, P, K, Ca and Mg per plant respectively. The highest accumulation of all nutrients was found in the leaves. The nutrient with the highest specificuptake rate was K, which ranged from 0.0037 to 0.0838.g g–1 d–1.  相似文献   

7.
为了探讨不同浓度甘氨酸态氮对普通白菜幼苗生长和氮代谢的影响,在水培条件下比较了2个普通白菜品种(华王和五月慢)4个甘氨酸(Gly)浓度水平下(0、2.5、5.0、10.0、20.0mmol·L~()-1))全株干质量、总氮含量、总碳含量及氮代谢关键酶活性的差异。结果表明,2个普通白菜品种幼苗干质量、总氮含量、总碳含量及氮代谢关键酶活性均随着甘氨酸浓度的增加呈先上升后降低的趋势;2.5~10.0mmol·L~()-1)处理下2个普通白菜品种幼苗干质量、总氮含量、总碳含量、谷氨酰胺合成酶活性、谷氨酸合成酶活性及根系硝酸还原酶活性、根系谷草转氨酶活性、根系谷丙转氨酶活性大多显著高于对照;20.0mmol·L~()-1)处理下2个普通白菜品种幼苗干质量、总碳含量、总氮含量及大部分酶活性基本与对照差异不显著,其中五月慢幼苗干质量、地上部总氮含量、地上部和根系总氮含量显著低于对照。综上,适宜浓度的甘氨酸态氮处理下植株较高的GS、GOGA活性及根系NR、GOT、GPT活性有利于普通白菜对甘氨酸的同化利用,从而促进普通白菜的生长和碳氮积累。  相似文献   

8.
The nature of sediments in abandoned channels is an important component of their development as floodplain wetlands. The texture, organic matter, phosphorous, potassium, and nitrogen content of sediments were determined for abandoned channels along the Iowa and Cedar Rivers near their confluence in Iowa. Differences in the levels of these constituents were examined among categories of three landscape gradients: present connectivity to the river, time since abandonment, and proximity to agricultural land use. Local scale processes of ecological development are seen in the importance of time for increased organic matter and nitrogen. Basin scale processes of sediment transport and deposition are revealed by the importance of connectivity for decreases in these two elements, and by the counter-intuitive findings for nitrogen and especially phosphorous and potassium in relation to agricultural proximity. Location on a floodplain is important for differentiating development, but it cannot be reduced to univariate gradients.  相似文献   

9.
The objective of this study was to compare the physico-chemical properties and antioxidant activity of six apple cultivars grown in southern Brazil. Apple peel color, dry matter, total soluble solids, pH, total sugars, titratable acidity, total phenolics, total monomeric anthocyanin and total antioxidant activity were measured in the apple cultivars Imperatriz, Daiane, Fred Hough, Fuji Suprema, Galaxy and Baronesa. The results showed great quantitative differences in the composition of the apple cultivars. Of all the cultivars, the peel of Galaxy was slightly more red-colored and that of Fred Hough was the least red-colored. The dry matter varied from 15.24% (Galaxy) to 19.55% (Fuji Suprema), the soluble solids content was between 11.8 (Fred Hough) and 14.0 (Daiane) °Brix, pH values varied from 3.90 (Imperatriz) to 4.27 (Fred Hough), the total sugar content (g 100 g−1) ranged from 11.54 (Imperatriz) to 14.78 (Fuji Suprema) and the titratable acidity content (g 100 g−1) varied from 0.20 (Baronesa) to 0.36 (Imperatriz). The total phenolic content (GAE 100 g−1 fresh matter) observed in the apple cultivars was between 105.4 (Baronesa) and 269.7 mg (Imperatriz). The values of the total anthocyanin content (mg 100 g−1 FM) ranged from 4.79 (Fred Hough) to 41.96 (Galaxy). The highest total antioxidant activity was observed in Imperatriz (739 μmol TEAC 100 g−1 FM), while the lowest value was found in Fuji Suprema (335 μmol TEAC 100 g−1 FM). There was a strong correlation between total monomeric anthocyanin content and all peel color measurements and between antioxidant activity and total phenolic content. The results suggested that genotype is the main factor that determines the composition of bioactive compounds in apples and this provides important information on how to make the best use of the apple cultivars investigated.  相似文献   

10.
To determine the extent to which transpiration and Ca concentration in the nutrient solution affect the regulation of growth, two independent experiments with young tomato plants were carried out under fully controlled climate conditions and grown hydroponically. The first experiment consisted of the regulation of transpiration by three levels of relative air humidity (RH): 50%, 70% (control) and 95% (corresponding to 1.32, 0.79 and 0.13 kPa, respectively) during 7 days. The second experiment involved four periods of 1, 3, 7 or 14 days of low-calcium (0.5 meq L−1) compared with the nutrient standard solution (9 meq L−1). The results show that plant growth was affected more by RH than by the reduction of Ca in the nutrient solution. High humidity reduced the total plant dry matter and total leaf area, increasing the dry matter partitioning into the stems and reducing it into the leaves. However, the low-Ca supply did not affect those parameters. Plant Ca concentration was significantly reduced by low-Ca supply as well as by high RH, but to a much greater extent by the Ca supply than by high RH. Ca concentrations in leaves, stem, and roots were quickly reduced already after 1 day of low-Ca. After 14 days, Ca concentration in all plant organs (leaves, stems and roots) was reduced by approximately 70% compared to control plants. Our data show that calcium supply, and consequently Ca concentration in the tomato plant can be reduced drastically for short-term periods during the vegetative growth stage without any adverse effect on growth whilst higher humidity reduce both growth and Ca concentration in young vegetative tomato plants. Consequently, reduced Ca uptake at high air humidity is not the cause for the reduction in growth.  相似文献   

11.
以山东莲藕地方品种"齐头"为试材,采用田间池栽试验,在莲藕不同生育期动态取样,测定各器官的干物质量和氮、磷、钾养分含量,计算各生育时期养分积累量,明确莲藕干物质积累及氮、磷、钾的吸收规律,以期为黄河中下游地区莲藕合理施肥提供参考依据。结果表明:莲藕干物质积累呈"慢-快-慢"的变化趋势。膨大茎形成期是莲藕干物质积累最快的时期,积累速率为每株29.27 g·d^-1。根状茎膨大之前,干物质主要集中在叶片和叶柄中,膨大之后,叶片和叶柄中的营养物质逐渐向膨大茎中转移,膨大茎中干物质最终积累量占全株的66.68%。不同时期莲藕氮、磷、钾的吸收积累量不同。膨大茎形成期莲藕对氮、磷、钾的积累速率最大,分别为每株0.46、0.18、0.56 g·d^-1,积累量分别占全生育期的49.50%、31.49%、39.56%。整个生育期莲藕氮、磷、钾吸收积累量的比例为1∶0.62∶1.53。根状茎膨大之前,莲藕氮和磷主要集中在叶片中,钾主要集中在叶柄中,之后随着地下根状茎的膨大,叶片和叶柄中的养分逐渐向地下部分转移,成熟期地下膨大茎中氮、磷和钾积累量分别占全株积累总量的71.97%、69.54%和87.89%。综上所述,莲藕前期以营养生长为主,根状茎膨大之后,以贮藏生长为主,膨大茎形成期为莲藕生长的关键时期。  相似文献   

12.
Total fresh and dry weight of Capsicum chinense fruit accessions were inversely correlated with accumulation of dry matter, and fruits with a higher percentage of dry matter accumulated proportionally more total soluble solids. Based on regression analysis, a 1% increase in fruit dry weight was associated with a 0.28% improvement in total soluble content, up to a maximum total soluble solid content of 10.25%. Regardless of shape, larger fruits had thicker pericarps, and were therefore more suitable for open air fresh markets. Smaller fruits had thinner pericarps and higher concentrations of total soluble solids and were more appropriate for dehydration and paprika production. Dry fruits with color intensities greater than 200 ASTA units, as required for paprika production, were found in 18.4% of the analyzed accessions. A large number of accessions, close to 27%, had total capsaicinoid concentrations less than or equal to 1.9 mg g−1 dry weight, and can be considered as sweet or light pungent fruits. A small percentage of accessions (2.5%) were classified as extremely hot fruits.  相似文献   

13.
An important goal in ecology is to understand controls on community structure in spatially and temporally heterogeneous landscapes, a challenge for which riverine floodplains provide ideal laboratories. We evaluated how spatial position, local habitat features, and seasonal flooding interact to shape aquatic invertebrate community composition in an unregulated riverine floodplain in western Alabama (USA). We quantified sediment invertebrate assemblages and habitat variables at 23 sites over a 15-month period. Dissolved oxygen (DO) varied seasonally and among habitats, with sites less connected to the river channel experiencing frequent hypoxia (<2 mg O2 L?1) at the sediment–water interface. Differences in water temperature among sites were lowest (<1 °C) during winter floodplain inundation, but increased to >14 °C during spring and summer as sites became isolated. Overall, local habitat conditions were more important in explaining patterns in assemblage structure than was spatial position in the floodplain (e.g., distance to the main river channel). DO was an important predictor of taxonomic richness among sites, which was highest where hydrologic connections to the main river channel were strongest. Compositional heterogeneity across the floodplain was lowest immediately following inundation and increased as individual sites became hydrologically isolated. Our results illustrate how geomorphic structure and seasonal flooding interact to shape floodplain aquatic assemblages. The flood pulse of lowland rivers influences biodiversity through effects of connectivity on hydrologic flushing in different floodplain habitats, which may prevent the development of harsh environmental conditions that exclude certain taxa. Such interactions highlight the ongoing consequences of river regulation for taxonomically diverse floodplain ecosystems.  相似文献   

14.
对4个不同矮蔓型西葫芦品种的干物质生产与分配进行研究,结果表明,半矮蔓与矮蔓西葫芦品种各器官干物质含量没有显著差异,根、茎、叶、果干物质含量分别为:9%、6%、12%、5%;全生育期群体生长率(cropgrowth rate,CGR)半矮蔓品种平均为17.2g/(m2·d),而矮蔓品种为12.5g/(m2·d),半矮蔓品种是矮蔓品种的1.38倍;苗期、结果初期、结果中期、结果后期的当前干物质生产量半矮蔓品种分别是矮蔓品种的1.07、1.28、1.26、1.91倍,后期干物质生产衰减与矮蔓品种的早衰存在着相互依存关系;当前干物质的分配率营养器官与生殖器官的比半矮蔓品种为2.7∶1,矮蔓品种为2.1∶1;干物质累积值半矮蔓品种是矮蔓品种的1.4倍,果实干质量累积值半矮蔓品种是矮蔓品种的1.27倍,半矮蔓品种干物质向果实的分配率约为30.8%,矮蔓品种约为34.7%,单位面积干物质生产量的提高是半矮蔓品种果实干质量高于矮蔓品种的主要原因。  相似文献   

15.
Summary

Cauliflower (Brassica oleracea L. var. botrytis) was grown in refined sand at low (0.0011 mg l?1), normal (0.55 mg l?1) and excess (5.5 mg l?1) Mn, each at three levels of B, deficient (0.0033 mg l?1), normal (0.33 mg H) and excess (3.3 mg l?1). In Mn deficient cauliflowers a deficiency of B accentuated visible symptoms of Mn deficiency and aggravated the Mn deficiency effects i.e. a decrease in dry matter, leaf Mn, sugars, starch, chlorophyll, Hill reaction and specific activity of aldolase and an increase in the concentrations of proline and inorganic phosphorus. In cauliflowers exhibiting B toxicity symptoms under conditions of excess B, excess Mn increased leaf Mn, sugars, nucleic acids, protein P, nucleic acid P, acid-labile P and leaf B. Excess Mn decreased the concentrations of DNA, protein nitrogen, chlorophyll and activities of peroxidase, aldolase and leaf B, leaf Mn in boron deficient cauliflowers.  相似文献   

16.
Mid-anthesis foliar sprays of paclobutrazol (PB) at 2.5, 1.25 and 0.62 g a.i. I-1 reduced spring growth and altered dry-matter distribution in fruiting spring shoots of ‘Hass’ avocado.(Persea americana Mill.) trees. There was a decrease in dry matter allocation to vegetative components and an increase in allocation to fruit. The starch concentration in the wood of spring shoots on trees treated with 2.5 g a.i. I-1 foliar PB was increased by ca. 70% compared with spring shoots from trees of other treatments. The mid-anthesis foliar treatments also reduced summer growth by ca. 20%. Trunk injection of PB at 0.2 g a.i. m~2 of canopy silhouette area when the spring growth matured, in addition to a mid- anthesis foliar spray of 1.25 g a.i. I-1, reduced the length of summer shoots by 36% when compared with untreated trees. The spray treatments of 2.5 and 1.25 g a.i. T1 PB at mid- anthesis increased the mean fruit size at harvest by 16 and 11% respectively. Fruit yield was not significantly affected by PB applications on an annual basis. However, the PB spray treatments of 1.25 and 0.62 g a.i. I-1 significantly increased the two year cumulative yield by ca. 63%. There was no significant effect from the trunk injection treatment on fruit yield in either the season of treatment or the following season.  相似文献   

17.
N was applied at 50, 100 or 150 mg l?1 in factorial combination with P at 7.5, 15 or 22.5 mg l?1 to asparagus seedlings. There were 6 successional harvests. N and P increased shoot dry weight by increasing mean dry weight and number of shoots. Increasing P had no effect on shoot growth at 50 mg l?1 N. N increased root dry weight (crown and roots) by increasing root number, whereas P decreased root dry weight due to a decrease in mean root dry weight. N increased total plant dry weight, but P had no effect. N and P increased the partitioning of dry weight to the shoots, while partitioning to the roots increased with time. Plant analysis revealed that 2.6–2.7% N and 0.29–0.36% P, on a dry-weight basis, were present in the shoots at the later harvests with the higher concentrations of N and P. 100–150 mg 1?1 N in combination with 15 mg l?1 P produced a seedling suitable for transplanting into commercial fields at 6 weeks from emergence.  相似文献   

18.
在2013～2015年期间,每年3月31日到5月28日,调查新疆喀什地区裂盖马鞍菌(Helvella leucopus)的发生情况和环境因子,持续3年调查结果表明:在胡杨林和毛白杨中均有子实体发生,裂盖马鞍菌子实体发生在土壤pH 8.0左右、有机质含量20～36 g/kg、全氮含量0.8～1.3 g/kg和速效钾含量189～293mg/kg的地区;野生子实体形成期的土壤温度5.0～26.4℃,空气湿度20％～35％,光照3000～8000 lux.  相似文献   

19.
混合基质条件下茄子苗期施肥量研究   总被引：4，自引：0，他引：4  
在混合基质（草炭、蛭石、炉渣灰）育苗条件下，随着施肥量增加，茄子幼苗生长、干物质积累以及植株对Ｎ、Ｐ、Ｋ的吸收量也随之增大。当施肥量达到２８００ｇ／ｍ３时，茄子幼苗的株高、干物质积累以及Ｎ、Ｐ、Ｋ吸收量均达到或接近最大值，因此，２８００ｇ／ｍ３是茄子混合基质育苗时较为适宜的施肥量  相似文献   

20.
以马蹄"芳林1号"茎尖为外植体,研究不同浓度的稀土元素La、Ce和Sm对马蹄组培苗增殖系数、干物质量和叶绿素含量的影响。结果表明:以45mg/L的Sm处理效果最佳,此时增殖系数为9.2,每株干物质量为0.28g,叶绿素含量为1.73mg/g鲜重,相对增加48.0%,丛生芽生长快,叶色浓绿,容易形成壮苗。  相似文献   

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