Interactive effects of N and P on growth but not on resource allocation of Canna indica in wetland microcosms

The interactive effects of three levels of N (mM) (low 0.36, medium 2.1 and high 6.4) and two levels of P (mM) (low 0.10 and high 0.48) on growth and resource allocation of Canna indica Linn. were studied in wetland microcosms. After 91 days of plant growth, there was a significant interactive effect of N and P on plant growth, but not on resource allocation (except for allocation of N to leaves and allocation of P to the stems). The plant growth positively responded to the relatively higher nutrient availability (taller plants with more stems, leaves and flowers), but the growth performance was not significantly different between the medium N-low P and high N-low P treatments. At high P, the total biomass in the high N was about 51% higher than that in the medium N and about 348% higher than that in the low N. The growth performance was related to the physiological responses. The photochemical efficiency (F_v/F_m) increased from 0.843 to 0.855 with an increase in N additions. The photosynthetic rate increased from 13 to 16 μmol m⁻² s⁻¹ in the low P levels and from 14 to 20 μmol m⁻² s⁻¹ in the high P levels with an increase in N applications, but significant difference was only between the low and medium N levels, regardless of the P levels. The tissue concentrations of N increased with an increase in N applications and decreased with an increase in P additions, whereas reverse was true for tissue concentrations of P. The highest concentrations of N and P in leaves were 30.8 g N kg⁻¹ in the high N-low P treatment and 4.9 g P kg⁻¹ in the low N-high P treatment. The percent biomass allocation to aboveground tissues in the high N was nearly twice that in the low N treatments. The N allocation to aboveground tissues was slightly larger in high N than in low N treatments, whereas the P allocation to aboveground tissues increased with an increase in the N addition. Although some patterns of biomass allocation were similar to those of nutrient allocation, they did not totally reflect the nutrient allocation. These results imply that in order to enhance the treatment performance, appropriately high nutrient availability of N and P are required to stimulate the growth of C. indica in constructed wetlands.     

Growth response of Bolboschoenus maritimus ssp. maritimus and B. maritimus ssp. compactus to different trophic conditions

Bolboschoenus maritimus (L.) Palla (=Scirpus maritimus L.) forms extensive stands in the littoral zone of small fishponds and as a weed in rice and maize fields. Within the species, two subspecies are distinguished: Bolboschoenus maritimus subsp. maritimus, B. maritimus subsp. compactus. They differ in ecology, especially in their relationships with trophic conditions and salinity of habitats. To determine growth response of these two types to different nutrient levels, we compared their seasonal development under experimental cultivation at four controlled nutrient levels. Some differences between the subspecies were found to be stable, regardless of nutrient level, namely greater amount of smaller underground tubers and more extensive rhizome system in subsp. compactus compared to less numerous larger tubers and simpler rhizome system in subsp. maritimus. In response to trophic conditions,the plants of subsp. compactus were more resistant to the conditions of the highest trophic level than those of subsp. maritimus, which were stressed. This demonstrates better adaptability and spreading ability of B. maritimus subsp. compactus at high trophic levels.     

The biology of Butomus umbellatus in shallow waters with fluctuating water level

Butomus umbellatus L. is a plant species typical of littoral communities of river and stream shores. It can form continuous stands in shallow reservoirs with fluctuating water level. Their expansion is promoted by: (a) intensive vegetative reproduction of plants, (b) crowded sprouting from rhizome fragments on emerged pond bottom, (c) shallow water layer in the year following summer drainage. Expansion of B. umbellatus depends on ploidy level: two cytotypes were found in the Czech and Slovak Republics, differing in their reproductive ability. Seed production of triploids is strongly limited (they are self-incompatible within clones), while diploids can be fully fertile. Nevertheless, even in diploids, the efficiency of seed reproduction under natural conditions is low. Triploids spread by intensive vegetative reproduction, which is decisive for clonal growth of populations and their regeneration after scraping of bottom surface. During seasonal development, maximum of aboveground biomass is produced in early summer, while underground biomass increases till autumn. Growth of the plants is limited by cutting before maximum underground biomass is attained, or by duck grazing.     

自然湿地生态恢复研究综述

湿地由于具有丰富的资源、独特的牛态结构和功能而享有“自然之肾”之称。为了更好地保护和开发利用湿地,世界各国都在积极采取措施阴止湿地的退化或消失,湿地的生态恢复与重建问题已成为生态学和环境科学的研究热点,在全面综述国内外湿地生态恢复研究进展的基础上,对湿地乍态恢复研究的重点和热点进行了探讨和分析,指出我国为做好湿地生态恢复工作尚需进一步加强湿地生态恢复的方法学、基础理论、应用技术和示范推广等方面的研究。     

模拟增温对黄河三角洲滨海湿地非生长季土壤呼吸的影响

冬季土壤呼吸能释放生长季所固存的碳, 因而在陆地碳循环中占有重要地位。随着全球气候变暖, 平均地表温度将升高0.3-4.8 ℃, 且冬季增温更加明显, 而温度的升高会促进更多CO₂的释放。另外, 滨海湿地地下水位浅, 淡咸水交互作用明显, 增温能引起土壤表层盐分升高, 从而影响土壤呼吸。该研究以黄河三角洲滨海湿地为研究对象, 采用红外辐射加热器模拟增温, 研究了该地区非生长季土壤呼吸的日动态及季节动态, 同时探讨了土壤呼吸对环境因子的响应机制。结果显示: 日动态中, 增温与对照的土壤呼吸速率变化趋势一致, 为单峰曲线; 在平均日变化中, 整个非生长季不同处理的土壤呼吸速率无显著差异, 而土壤温度和土壤盐分均为增温大于对照, 并且土壤呼吸峰值时间均比土壤温度提前。季节动态中, 整个研究期分为非盐分限制阶段(2014年11月-2015年2月中旬)和盐分限制阶段(2015年2月中旬-2015年4月)。在整个非生长季, 土壤呼吸速率无显著差异; 在非盐分限制阶段, 当10 cm土壤温度升高4.0 ℃时, 土壤呼吸速率显著提高22.9%, 而土壤呼吸温度敏感性系数(Q₁₀)与对照相比有所降低; 在盐分限制阶段, 尽管土壤温度升高3.3 ℃, 土壤呼吸速率却降低了20.7%, 这可能是由于增温引起了土壤盐分的升高, 同时由增温引起的土壤含水量的升高在一定程度上也限制了土壤呼吸, 而此阶段增温对Q₁₀无显著影响。因此, 在滨海湿地中, 增温除了直接影响土壤温度, 还可通过影响土壤水盐状况来影响土壤呼吸, 进而影响滨海湿地土壤碳库。     

Long‐term responses of leaf litter decomposition to temperature,litter quality and litter mixing in plateau wetlands

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A decade of boreal rich fen greenhouse gas fluxes in response to natural and experimental water table variability

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Differences between species in seed bank and vegetation helps to hold functional diversity in a floodable Neotropical savanna

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