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991.
Soil nitrogen (N) availability and pH are two determinants affecting plant growth, both of which are influenced by long‐term N deposition. However, the physiological mechanism of plants response to the changes in soil N availability and pH are not fully understood. To investigate the response of Picea asperata to both factors, seedlings of P. asperata were exposed to 50 or 1000 µM NH4NO3 with pH 5 or pH 7. In the current study, P. asperata, regardless of N availability and pH in growth medium, exhibited invariably a preference. Lower root biomass, root : shoot mass ratio, total root length and area, and root vitality were detected in high N condition compared to those in low N supply, corresponding well to lower net influxes of and at the root surface in both pH treatments. These results indicate that P. asperata may employ an active‐forge strategy to exploit nutrient resources for growth under low N availability, probably by increased below‐ground carbon allocation and net influxes of and . Although low pH, to some extent may generate more malondialdehyde, P. asperata would enhance pH tolerance by increased detoxification, i.e., antioxidant enzymes (peroxidase), free proline and soluble protein as well as improved carbohydrate status (i.e., soluble sugar and starch). 相似文献
992.
Maize(Zea mays L.), a staple crop in the North China Plain, contributing substantially to agricultural nitrous oxide(N_2O)emissions in this region. Many studies have focused on various agricultural management measures to reduce N_2O emissions. However, few have investigated soil N_2O emissions in intercropping systems. In the current study, we investigate whether maize-soybean intercropping treatments could reduce N_2O emission rates. Two differently configured maize-soybean intercropping treatments, 2:2 intercropping(two rows of maize and two rows of soybean, 2M2S) and 2:1 intercropping(two rows of maize and one row of soybean,2M1S), and monocultured maize(M) and soybean(S) treatments were performed using a static chamber method. The results showed no distinct yield advantage for the intercropping systems. The total N_2O production from the various treatments was 0.15 ± 0.04–113.85 ± 12.75 μg m~(-2) min~(-1). The cumulative N_2O emission from the M treatment was 16.9 ± 2.3 kg ha~(-1) over the entire growing season(three and a half months), which was significantly higher(P 0.05) than that of the 2M2S and 2M1S treatments by 36.6% and 32.2%, respectively. Two applications of nitrogen(N) fertilizer(as urea) at 240 kg N ha~(-1) each induced considerable soil N_2O fluxes. Short-term N_2O emissions(within one week after each of the two N applications) accounted for 74.4%–83.3% of the total emissions. Soil moisture, temperature, and inorganic N were significantly correlated with soil N_2O emissions(R~2= 0.246–0.365, n =192, P 0.001). Soil nitrate(NO_3~-) and moisture decreased in the intercropping treatments during the growing season. These results indicate that maize-soybean intercropping can reduce soil N_2O emissions relative to monocultured maize. 相似文献
993.
沙冬青光合速率日变化及其影响因子研究 总被引:2,自引:1,他引:2
采用Li-6200光合分析仪,在自然条件下对沙冬青(A.mongolicus(Maxim)Chengf.)光合作用日进程进行了观测,结果表明:在夏季晴天条件下,沙冬青Pn日变化为双峰曲线,峰值分别出现在11:00时和15:00时,具有典型的“光合午休”特征。相关分析和多元回归分析表明,光量子密度和气孔阻力是影响沙冬青叶片Pn日变化的主要生态因子。 相似文献
994.
Three nectarine (Prunus persica var. Nectarina Maxim.) cultivars grown under solar-heated greenhouse and open-field in northwest China, were tested to evaluate their photosynthetic and chlorophyll fluorescence response to both growth conditions, and whether nectarine plants acclimate to the solar-heated greenhouse growth condition. Comparisons of light-saturated photosynthetic capacity (Amax) and CO2-saturated photosynthetic capacity (RuBPmax) indicated that each cultivar (Z, Zao-Hongzhu; H, Hua-Guang; Y, Yan-Guang) maintained similar rates of light-saturated and CO2-saturated carbon assimilation when grown in both conditions. The curve of diurnal variation of net photosynthetic (PN) rate showed double peaks in open-field but single when grown in greenhouse. Compared with open-field-grown plants, a significant increase of daily average PN was found in Z but decreased in Y in greenhouse. The diurnal variation of Fv/Fm indicate that plants grown in greenhouse experience less photoinhibition than in open-field condition. A reduction in chlorophyll (chl) a/b ratio in leaves of greenhouse grown plants with significant increase in chlorophyll (chl) b content were obtained. The results suggest that some nectarine cultivars have the ability to acclimate to the solar-heated greenhouse growth condition. 相似文献
995.
N.Torkel Welander 《Scientia Horticulturae》1984,23(4):371-377
In vegetatively propagated Pelargonium × hortorum plants, formation of axillary shoots and initiation of inflorescences and leaves were promoted by an increase in quantum flux density, whereas application of GA3 had a negative effect. Application of CCC caused an increase in number of axillary shoots and consequently an increase in number of inflorescences and leaves per plant.Dry weight increase was promoted by an increase in quantum flux density, unaffected by GA3 treatment, but inhibited by CCC treatment. Moreover, continuous removal of the oldest leaves reduced the number of inflorescences, leaves, axillary shoots and dry weight. The changes in inflorescence and leaf initiation could not be definitely correlated to the changes in dry weight increase. 相似文献
996.
北京低山区两种人工林土壤中N2O排放通量的研究 总被引:12,自引:0,他引:12
N2 O是一种重要的温室气体 ,其主要的排放源是土壤。本研究采用静态封闭箱式技术在 1997~1998年对北京西山低山区元宝枫和油松人工林地土壤中N2 O的排放通量进行了原位测定。研究结果表明该地区森林土壤为大气N2 O气体的一个重要的源 ,年平均排放通量为 3 16 μg·m- 2 h- 1 ,变动范围为 - 1 2~ 7 92μg·m- 2 h- 1 。林地土壤N2 O的排放有较明显的季节变化趋势 ;夏季最高 ,春秋季次之 ,冬季最低甚至出现负值。排放通量的大小主要决定于土壤温度、土壤湿度及测定时前 5d内降水量等因子。研究还表明N2 O的排放通量有一定的日变化趋势 ;6 :0 0出现最低点 ,9:0 0和 18:0 0出现最高点 相似文献
997.
998.
采用静态箱-气相色谱法研究日光温室生菜地不施肥(CK)、施用腐熟鸡粪(H)、羊粪(S)、鸡粪+秸秆(HSt)、羊粪+秸秆(SSt)、羊粪+鸡粪+秸秆(SHSt)等6种处理的温室气体排放通量及增温潜势(GWP)。结果表明:(1)H、S、HSt处理的N_2O排放通量在施肥前、中、后期呈近"V"型变化,CK、SSt、SHSt呈倒"V"型变化;S、SSt、SHSt处理的CH_4排放通量呈倒"V"型变化;CO_2排放通量均呈近"V"型变化(SSt除外);(2)施肥前期,HSt、S、H、SHSt、SSt处理的N_2O排放通量分别较CK显著增加2.89、2.32、1.48、1.17、0.95倍;S、H的CH_4排放通量显著高于CK处理1.91、1.11倍;H的CO_2排放通量显著低于CK处理3.88倍。施肥中期,HSt的N_2O排放通量显著低于CK处理1.93倍;SHSt的CH_4排放通量显著高于CK处理1.34倍;各施肥处理的CO_2排放通量与CK差异不显著。施肥后期,H的N_2O排放通量显著高于CK处理1.10倍;SHSt、SSt、S的CH_4排放通量显著低于CK处理3.76、5.25、5.58倍;HSt的CO_2排放通量显著高于CK处理8.61倍;(3)全球增温潜势(GWP)按照SSHStHStSStCKH依次减小,建议施用腐熟鸡粪、鸡粪加秸秆及羊粪加秸秆。 相似文献
999.
[目的]研究倾斜土槽装置适宜的污水流量负荷。[方法]以5层倾斜土槽组合装置填充蜂窝煤渣和砂壤土,采用连续进水方式对人工配制的生活污水进行3种不同污水流量(100、200和300 L/d)对污染物指标去除效果的试验研究。[结果]3种污水流量处理对BOD5、COD、TP、TN等水质指标的平均去除率差异均不显著,但以100 L/d污水流量处理下污染物的去除率相对较大;倾斜土槽装置对BOD5、COD的去除率大都在87.8%~90.2%,对TP的去除率在98.4%~98.7%,TN的去除率也在72.0%~74.5%范围内。[结论]不同污水流量下倾斜土槽装置对生活污水的净化效果良好。 相似文献
1000.
Jennifer L. Stoffel Stith T. Gower Jodi A. Forrester David J. Mladenoff 《Forest Ecology and Management》2010
Soil surface CO2 flux (Sflux) is the second largest terrestrial ecosystem carbon flux, and may be affected by forest harvest. The effects of clearcutting on Sflux have been studied, but little is known about the effect of alternative harvesting methods such as selective tree harvest on Sflux. We measured Sflux before and after (i) the creation of forest canopy gaps (simulating group tree selection harvests) and (ii) mechanized winter harvest but no tree removal (simulating ground disturbance associated with logging). The experiment was carried out in a sugar maple dominated forest in the Flambeau River State Forest, Wisconsin. Pre-treatment measurements of soil moisture, temperature and Sflux were measured throughout the growing season of 2006. In January–February 2007, a harvester created the canopy gaps (200–380 m2). The mechanization treatment consisted of the harvester traveling through the plots for a similar amount of time as the gap plots, but no trees were cut. Soil moisture and temperature and Sflux were measured throughout the growing season for 1 year prior to harvest and for 2 years after harvest. Soil moisture and temperature were significantly greater in the gap than mechanized and control treatments. Instantaneous Sflux was positively correlated to soil moisture and soil temperature at 2 and 10 cm, but temperature at 10 cm was the single best predictor. Annual Sflux was not significantly different among treatments prior to winter 2007 harvest, and was not significantly different among treatments after harvest. Annual (+1 std. err.) Sflux averaged 967 + 72, 1011 + 72, and 1012 + 72 g C m−2 year−1 in the control, mechanized and gap treatments, respectively, for the 2-year post-treatment period. The results from this study suggest selective group tree harvest significantly increases soil moisture and temperature but does not significantly influence Sflux. 相似文献