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1.
《Scandinavian Journal of Forest Research》2012,27(1-4):1-14
Analysis of in vivo shoot nitrate reductase activity (NRA) of the grass Deschampsia flexuosa (L.) Trin. has been proposed as a method of indicating the availability of nitrate in northern temperate forest soils. We report the seasonal variation in NRA and the influence of temperature on the NRA assay. Studies were performed in the field or on natural populations on topsoil monoliths in a greenhouse. The induced in vivo NRA as measured at 28°C was higher in plants grown at lower than at higher temperatures within the range 4–20°C, although the induction was faster at higher temperatures. When the assay was performed at various temperatures, enzyme activity was much lower at lower temperatures. The accumulation of organic nitrogen in shoots showed that reduction actually increased with temperature. Transfer of monoliths from high to low temperature led to an increase of in vivo NRA within a day, whereas the decline caused by the reverse began after six days. Variations in temperature accounted for between 0 and 80% of the seasonal variation in NRA in the field, depending on the influence of the variability in nitrate supply. Maximally induced NRA after application of nitrate was mostly higher in a clearfelling than in a closed forest. In the forest, there was a close correlation between current and maximally induced NRA. One interpretation of this result is that low availability of nitrogen may have been a cause of the lower maximally induced NRA there. This is supported by results from other studies. We conclude that variations in temperature and availability of nitrogen, particularly nitrate, are largely responsible for seasonal variations in NRA. The influence of temperature can be adjusted for. 相似文献
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围隔海域水质评价及底栖曲浒苔对水质修复能力评估研究 总被引：2，自引：2，他引：0
于2015年1—12月对杭州湾北部沿岸碧海金沙围隔海域水环境质量进行每月一次的跟踪监测,进行围隔海域水质分析评价,通过调查底栖浒苔群落的种类组成及其生物量,评估其对围隔海域水质的修复能力。根据富营养化状态指数(E)表明,2015年该围隔海域1—9月份属于高富营养化状态,10—12月份属于富营养化状态,其中溶解无机氮(DIN)全年平均为(0.91±0.11)mg/L,属劣Ⅳ类海水水质标准;溶解无机磷(DIP)全年平均为(0.031±0.005)mg/L,属Ⅲ类海水水质标准;根据有机污染指数(A)显示,2015年该围隔海域2—7月份开始受到有机污染,8月、9月和12月属于轻度有机污染,10月和11月属于中度有机污染。底栖浒苔类的优势种为曲浒苔(Ulva flexuosa),占底栖藻场总生物量的97.3%。2015年3月至12月碧海金沙围隔海域底栖曲浒苔全年总生物量净增长量为1 497.3 t,实验测得曲浒苔组织内总氮(TN)和总磷(TP)平均含量分别为3.50%±0.02%和0.13%±0.01%(干重),全年吸收水体中氮和磷量分别为(4 354.90±46.78)kg和(161.75±1.74)kg。分析表明,碧海金沙围隔海域天然曲浒苔种群通过同化养殖水体中氮磷,具备一定的水质修复能力,但尚未平衡由水产养殖活动造成的营养负荷。因此,在近岸海水养殖海域,除需进行底栖海藻场的构建外,还需要调整养殖结构,如增加大型海藻栽培以建立多营养层次的综合养殖模式(IMTA),实现近岸海水养殖产业的可持续发展。 相似文献
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本研究以黄河源区发草作为研究对象,通过生境地植物群落物种结构组成、多样性分布、土壤理化特性等调查,采用相关分析和RDA排序法分析了黄河源区玛沁县5个发草适生地植物群落多样性特征和土壤影响因子及其关系,以期揭示影响发草种群在复杂多样高寒沼泽异质生境中适应性的关键环境因子。结果表明：1）不同发草适生地植物群落结构、组成和多样性指标明显不同,菊科、禾本科、莎草科、毛茛科、龙胆科和玄参科物种为发草适生地常见物种;2）不同发草适生地之间在土壤氮（N）、磷（P）、碳（C）、有机质（SOM）、土壤水分含量（W）和pH上也具有显著差异;3）发草适生地植物群落中发草的盖度、株高、生物量和重要值与群落物种丰富度、Simpson优势度指数、Shannon-Wiener指数、P和W呈显著负相关,与Alatalo均匀度指数、pH值呈显著正相关。研究结果表明发草更加适应低P、湿润偏中生的土壤环境,而随着群落中物种丰富度的增加发草在群落中的重要值显著下降则说明发草具有部分的先锋种特性,显示了利用发草修复和治理退化草地的可能潜力。 相似文献
4.
河南博爱竹林是中原地区宝贵的竹资源。近年来,博爱县优良乡土竹种——甜竹受到了竹竿锈病的严重危害。文章调查了竹竿锈病的分布状况,提出了以营林措施为主,药剂防治为辅,协调运用人工、物理等方法的综合防治措施。 相似文献
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Despite geotextile-mats having the potential for soil conservation, field studies on the effects of geotextiles on soil properties are limited. Hence, the utilization of palm-mat geotextiles as a potential soil conservation technique was investigated at Hilton, east Shropshire, U.K. (52°33′5.7″ N, 2°19′18.3″ W). Geotextile-mats constructed from Borassus aethiopum (Borassus palm of West Africa) and Mauritia flexuosa (Buriti palm of South America) leaves are termed Borassus mats and Buriti mats, respectively. Field experiments were conducted at Hilton during 2007–2009, to study the impacts of Borassus and Buriti mats on selected properties of the topsoil (0–5 cm). Ten fixed plots (10 × 1 m on a 15° slope) were established, with duplicate treatments. The treatments were: (i) bare soil; (ii) permanent grassed; (iii) bare soil with 1 m Borassus-mat buffer strips (area coverage ~ 10%) at the lower end of the plots; (iv) bare soil with 1 m Buriti mat buffer strips (area coverage ~ 10%) at the lower end of the plots; and (v) completely-covered with Borassus mats. Initial and final soil samples of the topsoil were collected and analysed for bulk density, aggregate stability, soil organic matter (SOM), total soil C (TSC), total soil N (TSN) and pH. Results indicate that, apart from Borassus completely-covered plots, soil bulk density increased and aggregate stability decreased in all plots after two years. Despite decreases in SOM contents in bare plots, SOM content did not change after two years in the grassed and geotextile treated plots. Treatments had no effects on changes in pH, TSC or TSN. Both Borassus and Buriti mat-covers within the buffer strip plots had little impact on SOM, TSC and TSN changes compared with bare soils within the same plots. Thus, Borassus buffer strip plots were very effective in maintaining some soil properties (i.e. SOM, TSC, and TSN) after two years of erosion by water. In summary, utilization of Borassus mats as buffer strips was very successful in conserving soil properties on a loamy sand soil. 相似文献
6.
Heathlands are endangered by both atmospheric nutrient deposition and natural succession. High-intensity management measures are considered necessary, as low-intensity measures (e.g. mowing, prescribed burning) are not able to compensate for atmospheric nutrient loads. Choppering (i.e. the near-complete removal of the O-layer) has several advantages over sod-cutting, including less waste material, faster vegetation recovery and lower costs. This raises the question addressed in this study as to the extent to which choppering and sod-cutting affect nutrient budgets in dry heathlands.We compared the quantities of N, Ca, K, Mg, and P removed by choppering and sod-cutting in the Lueneburg Heath (NW Germany). Nutrient balances were calculated by analysing atmospheric inputs, elevated leaching rates following management, and output due to the removal of above-ground biomass and humus horizons.Nutrient loss was particularly high after removal of O- and A-horizons. In contrast, increased leaching after management was of minor importance for nutrient budgets. Although considerably more nutrients were removed by sod-cutting than by choppering (e.g. N: 1712/1008 kg ha−1), nutrient output by choppering was still sufficient to compensate for 60.7 years of net N-input. Choppering was able to remove more N per volume unit than sod-cutting due to higher N-contents in the organic layer than in the A-horizon. For this reason, choppering is more economical than sod-cutting and, thus, should be considered the preferable method at sites not dominated by Molinia caerulea. A combination of high-intensity measures with prescribed burning would appear to be suitable as this would ensure more selective removal of N. 相似文献
7.
The pathogenicity of an isolate of a Pythium species from Signy Island in the South Orkney Islands was tested against the Antarctic hairgrass Deschampsia antarctica. The isolate was found to infect plants at 8ºC and to cause foliar and root symptoms similar to those seen in other Pythium infections in grasses. Analysis of ribosomal RNA sequences placed it, together with another isolate from Antarctica, in a clade that included the known snow moulds caused by Pythium spp. Sporangia and oogonia were produced in culture, but the isolate differed from other Pythium spp. in producing chlamydospores in older cultures and plant tissue. This is the first report of a pathogen of an eukaryotic vascular plant in the maritime Antarctic region. 相似文献
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M ZEBERIO Juan 《干旱区科学》2020,12(4):653-665
Degradation processes affect a vast area of arid and semi-arid lands around the world and damage the environment and people′s health. Degradation processes are driven by human productive activities that cause direct and indirect effects on natural resources, such as species extinction at regional scale, reduction and elimination of vegetation cover, soil erosion, etc. In this context, ecological rehabilitation is an important tool to recover key aspects of the degraded ecosystem. Rehabilitation trials rely on the use of native plant species with characteristics that allow them to obtain high survival and growth rates. The aim of this work was to assess the survival and growth of native woody species in degraded areas of northeastern Patagonia and relate them to plant functional traits and environmental variables. We observed high early and late survival rates, and growth rates in Prosopis flexuosa DC. var. depressa F.A. Roig and Schinus johnstonii F.A. Barkley, and low values in Condalia microphylla Cav. and Geoffroea decorticans (Gillies ex Hook. & Arn.) Burkart. Early survival rates were positively associated with specific leaf area (SLA) and precipitation, but negatively associated with wood density, the maximum mean temperature of the warmest month and the minimum mean temperature of the coldest month. Late survival rates were positively associated with SLA and soil organic matter, but negatively associated with plant height and precipitation. The temperature had a positive effect on late survival rates once the plants overcame the critical period of the first summer after they were transplanted to the field. Prosopis flexuosa and S. johnstonii were the most successful species in our study. This could be due to their functional traits that allow these species to acclimatize to the local environment. Further research should focus on C. microphylla and G. decorticans to determine how they relate to productive conditions, acclimation to environmental stress, auto-ecology and potential use in ecological rehabilitation trials. 相似文献
10.
《Communications in Soil Science and Plant Analysis》2012,43(19-20):2699-2718
Abstract The objective was to find an uncomplicated test giving the best correlation between calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), zinc (Zn), and lead (Pb) extracted from humic forest soil and the total concentration of the element in some understorey forest plants using well‐known extractants. The elements were selected because Ca, Mg, Mn, Cu, and Zn are essential nutrients to plants and Zn and Pb are potentially harmful heavy metals received over the years in the southern parts of Norway by long‐range atmospheric transport. Extraction of organic podzolic surface soil (Oe and Oa horizon) from 17 different pine forests in central and southern Norway was carried out with four different reagents to evaluate uptake of Ca, Mg, Mn, Cu, Zn, and Pb in the understorey plants Deschampsia flexuosa, Vaccinium myrtillus (leaves and stems), and Vaccinium vitis‐idaea (leaves and stems). The NH4OAc, NH4NO3, HCl, and EDTA solutions used to extract the soil in addition to concentrated HNO3, demonstrated variability in capacity to extract the different elements from the soil. The extractants yielded significant relations between concentrations of Ca, Mn, and Pb in the Oe or Oa horizon and some of the plants or plant compartments, even though distinct correlation was more dependent on species and plant part than the actual extractant used. In the case of Zn, Cu, and Mg only a few sporadic correlations were observed between the different plant/plant compartments and the element concentrations in the soil extracts. Altogether none of the extractants was shown to be superior to the others in providing the best correlation with the elements concentrations in selected plant/plant compartments. In the case of Ca, Mn, and Pb all the extractants including concentrated HNO3 provided significant correlations with at least some of the selected plant/plant compartments. 相似文献