Increased Nitrogen Deposition Research Articles

Effects of simulated nitrogen deposition on soil microbial biomass carbon and nitrogen in natural evergreen broad-leaved forest in the Rainy Area of West China

To understand the effects of increasing nitrogen deposition on soil microbial biomass carbon (MBC) and nitrogen(MBN), an in situ experiment was conducted in a natural evergreen broad-leaved forest in Ya'an City, Sichuan Province. Four levels of nitrogen deposition were set: i.e., control (CK, 0 g N·m-2·a-1), low nitrogen (L, 5 g N·m-2·a-1), medium nitrogen (M, 15 g N·m-2·a-1), and high nitrogen (H, 30 g N·m-2·a-1). The results indicated that nitrogen deposition significantly decreased MBC and MBN in the 0-10 cm soil layer, and as N de-position increased, the inhibition effect was enhanced. L and M treatments had no significant effect on MBC and MBN in the 10-20 cm soil layer, while H treatment significantly reduced. The influence of N deposition on MBC and MBN was weakened with the increase of soil depth. MBC and MBN had obvious seasonal dynamic, which were highest in autumn and lowest in summer both in the 0-10 and 10-20 cm soil layers. The fluctuation ranges of soil microbial biomass C/N were respectively 10.58-11.19 and 9.62-12.20 in the 0-10 cm and 10-20 cm soil layers, which indicated that the fungi hold advantage in the soil microbial community in this natural evergreen broad-leaved forest.

华西雨屏区天然常绿阔叶林土壤可培养微生物数量对模拟氮沉降的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 华西雨屏区天然常绿阔叶林土壤可培养微生物数量对模拟氮沉降的响应 DOI: 10.5846/stxb201605040842 作者: 作者单位: 四川农业大学,四川农业大学,四川农业大学,四川农业大学,四川农业大学,四川农业大学,四川农业大学,四川农业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家“十二五”科技支撑资助项目（2010BACO1A11）；四川省“十二五”农作物育种攻关资助项目（2011NZ0098-10） Response of culturable soil microorganisms to simulated nitrogen deposition in a natural evergreen broadleaf forest in the Rainy Area of Western China Author: Affiliation: Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了解氮沉降对华西雨屏区天然常绿阔叶林土壤微生物数量的影响，从2013年11月至2014年12月，通过野外模拟N（NH4NO3）沉降，氮沉降水平分别为对照（CK 0 kg N hm-2 a-1）、低氮沉降（L 50 kg N hm-2 a-1）、中氮沉降（M 150 kg N hm-2 a-1）和高氮沉降（H 300 kg N hm-2 a-1），研究了氮沉降对天然常绿阔叶林0-10cm和10-20cm土层土壤可培养微生物数量的影响。结果表明：华西雨屏区天然常绿阔叶林0-10cm土层的细菌、真菌和放线菌数量均显著大于10-20cm土层，氮沉降未改变原有垂直分布格局。L处理对0-10cm和10-20 cm土层土壤微生物总量无显著影响，M和H处理则显著降低了土壤微生物总量。氮沉降降低了0-10cm和10-20cm土层的细菌数量，且抑制作用随氮沉降量的增加而增强。氮沉降降低了0-10cm土层的真菌数量，但下降幅度与氮沉降量之间无明显规律；在10-20cm土层，M和H处理在夏季显著增加了真菌数量，表明适量氮沉降能有效缓解夏季土壤真菌的氮限制状态。氮沉降对0-10cm土层放线菌数量的影响表现为先促进再抑制，L和M处理增加了放线菌数量，H处理降低了放线菌数量；氮沉降增加了10-20cm土层的放线菌数量，其中M处理的促进作用最大。氮沉降对土壤微生物数量的影响随土壤深度的增加而减弱。 Abstract:Forest soil microbial activity is an important aspect of soil properties, and the number of the three kinds of microorganisms (bacteria, fungi, and actinomycetes) is an important indicator of the level of soil microbial activity. To understand the effects of increasing nitrogen deposition on soil microorganisms, an in situ experiment was conducted in a natural evergreen broadleaf forest in Ya'an City, Sichuan Province. We conducted the field experiment between November 2013 and December 2014. Four levels of nitrogen deposition were set:control (CK 0 kg N hm-2 a-1), low nitrogen (L 50 kg N hm-2 a-1), medium nitrogen (M 150 kg N hm-2 a-1), and high nitrogen (H 300 kg N hm-2 a-1). The results indicated that the number of bacteria, fungi, and actinomycetes in the 0-10 cm soil layer was significantly greater than that in the 10-20 cm layer. Nitrogen deposition did not change the original vertical distribution pattern of bacteria, fungi, and actinomycetes in the natural evergreen broadleaf forest in the Rainy Area of Western China. The L treatment did not have a significant effect on total soil microbial number, whereas the M and H treatments significantly reduced the total soil microbial number in both the 0-10 cm and 10-20 cm soil layers. Nitrogen deposition inhibited the number of bacteria in the 0-10 cm and 10-20 cm soil layers, and as nitrogen deposition increased, the inhibition effect was enhanced. Compared with the control, the M and H treatments significantly increased the number of fungi in the 10-20 cm soil layer during summer, indicating that a suitable amount of nitrogen deposition could effectively alleviate the nitrogen limitation of soil fungi in that season. Nitrogen deposition decreased the amount of fungi in the 0-10 cm soil layer, but there was no obvious relationship between the decrease and nitrogen deposition rate, whereas nitrogen deposition increased the number of actinomycetes in the 10-20 cm soil layer, and the increase was greatest in the M treatment. Nitrogen deposition first increased and then inhibited the number of actinomycetes in the 0-10 cm soil layer. The L and M treatments increased the number of actinomycetes, whereas the H treatment reduced the number of actinomycetes. The effects of nitrogen deposition on the quantity of soil microbial organisms decreased with increasing soil depth. 参考文献 相似文献 引证文献

Effluxes of nitrous oxide, methane and carbon dioxide and their responses to increasing nitrogen deposition in the Gurbantünggüt Desert of Xinjiang, China

Effluxes of nitrous oxide, methane and carbon dioxide and their responses to increasing nitrogen deposition in the Gurbantünggüt Desert of Xinjiang, China

Modeling long-term changes in tundra carbon balance following wildfire, climate change, and potential nutrient addition.

To investigate the underlying mechanisms that control long-term recovery of tundra carbon (C) and nutrients after fire, we employed the Multiple Element Limitation (MEL) model to simulate 200-yr post-fire changes in the biogeochemistry of three sites along a burn severity gradient in response to increases in air temperature, CO2 concentration, nitrogen (N) deposition, and phosphorus (P) weathering rates. The simulations were conducted for severely burned, moderately burned, and unburned arctic tundra. Our simulations indicated that recovery of C balance after fire was mainly determined by the internal redistribution of nutrients among ecosystem components (controlled by air temperature), rather than the supply of nutrients from external sources (e.g., nitrogen deposition and fixation, phosphorus weathering). Increases in air temperature and atmospheric CO2 concentration resulted in (1) a net transfer of nutrient from soil organic matter to vegetation and (2) higher C : nutrient ratios in vegetation and soil organic matter. These changes led to gains in vegetation biomass C but net losses in soil organic C stocks. Under a warming climate, nutrients lost in wildfire were difficult to recover because the warming-induced acceleration in nutrient cycles caused further net nutrient loss from the system through leaching. In both burned and unburned tundra, the warming-caused acceleration in nutrient cycles and increases in ecosystem C stocks were eventually constrained by increases in soil C : nutrient ratios, which increased microbial retention of plant-available nutrients in the soil. Accelerated nutrient turnover, loss of C, and increasing soil temperatures will likely result in vegetation changes, which further regulate the long-term biogeochemical succession. Our analysis should help in the assessment of tundra C budgets and of the recovery of biogeochemical function following fire, which is in turn necessary for the maintenance of wildlife habitat and tundra vegetation.

Endophyte species influence the biomass production of the native grass Achnatherum sibiricum (L.) Keng under high nitrogen availability.

Research on the interaction of endophytes and native grasses normally takes infection status into account, but less often considers the species of endophyte involved in the interaction. Here, we examined the effect of endophyte infection, endophyte species, nitrogen availability, and plant maternal genotype on the performance of a wild grass, Achnatherum sibiricum. Six different Epichloë‐infected maternal lines of A. sibiricum were used in the study; three lines harbored Epichloë gansuensis (Eg), while three lines harbored Epichloë sibirica (Es). These endophytes are vertically transmitted, while Eg also occasionally produces stromata on host tillers. We experimentally removed the endophyte from some ramets of the six lines, with the infected (E+) and uninfected (E−) plants grown under varying levels of nitrogen availability. Eg hosts produced more aboveground biomass than Es hosts only under high nitrogen supply. Endophyte species did not show any influence on the maximum net photosynthetic rate (P max), photosynthetic nitrogen use efficiency, or total phenolics of A. sibiricum under all nitrogen conditions. However, the plant maternal genotype did influence the P max and shoot biomass of A. sibiricum. Our results show that endophyte species influenced the shoot biomass of A. sibiricum, and this effect was dependent on nitrogen supply. As with most coevolutionary interactions, A. sibiricum that harbored Eg and Es may show pronounced geographic variation in natural habitats with increased nitrogen deposition. In addition, stroma‐bearing endophyte (Eg) provides positive effects (e.g., higher biomass production) to A. sibiricum plants during the vegetative growth stage.

A strategy for introducing an endangered plant Mosla hangchowensis to urban area based on nitrogen preference

To introduce endangered plants to urban green space for ex situ conservation successfully, it is important to better understand the optimal NO3 −/NH4 + ratios for profitable plant. Increasing nitrogen deposition altered the nitrate to ammonium ratio (NO3 −/NH4 +) in soil. This change may strongly affect the fate of endangered plants, which often have little ability to adapt to environmental changes. In this study, we carried out a microcosm hydroponic experiment by growing Mosla hangchowensis (an endangered species) to test its preference to NO3 −/NH4 + ratios and used congeneric M. dianthera (a widespread species) for comparison. Results showed that M. hangchowensis preferred an equal NO3 −/NH4 + ratio to NO3 − as an N source, with a higher biomass observed under NO3 −/NH4 + ratios of 50/50 and 75/25 than other treatments. However, M. dianthera preferred NO3 − as N source, with a higher biomass under NO3 −/NH4 + ratios of 100/0 and 75/25 than other treatments. NH4 + is the dominant form of N in atmospheric deposition in China and continued increasing in nitrogen deposition may be detrimental to M. hangchowensis, while only have minimal effects on M. dianthera. Urban regions are expanding, and the high environmental heterogeneity in urban areas can provide potential habitats for M. hangchowensis. Based on this study, we advise that the ex suit conservation of M. hangchowensis in urban green spaces needs to adjust the fertilization strategy according to the situation of nitrogen deposition to achieve the optimal NO3 −/NH4 + ratio.

Effects of arbuscular mycorrhizal fungi on the growth, photosynthesis and photosynthetic pigments of Leymus chinensis seedlings under salt-alkali stress and nitrogen deposition

Leymus chinensis is the most promising grass species for salt-alkaline grassland restoration in northern China. However, little information exists concerning the role of arbuscular mycorrhizal (AM) symbiosis in the adaptation of seedlings to salt-alkali stress, particularly under increased nitrogen deposition, which has become a major environmental problem throughout the world. In this study, Leymus chinensis seedlings were cultivated in soil with 0, 100 and 200mM NaCl/NaHCO3 under two forms of nitrogen (10mM NH4NO3 or NH4Cl: NH4NO3=3:1), and the root colonization, growth and photosynthetic characteristics of the seedlings were measured. The results showed that the colonization rate and intensity decreased with increasing salt-alkali stress and were much lower under alkali stress. The nitrogen treatments also decreased the colonization, particularly under the NH4+-N treatment. Compared with the non-mycorrhizal controls, mycorrhizal seedlings generally presented higher plant biomass, photosynthetic parameters and contents of photosynthetic pigments under stresses, and the inhibitive effects of alkali stress were substantially stronger. In addition, both nitrogen forms decreased the physiological indexes compared with those of the AM seedlings. Our results suggest that salt stress and alkali stress are significantly different and that the salt-alkali tolerance of Leymus chinensis seedlings could be enhanced by associations with arbuscular mycorrhizal fungi, in which would yield better plant growth and photosynthesis. Excessive nitrogen in the soil affects mycorrhizal colonization and thereby inhibits the growth and photosynthetic ability of the seedlings.

The effect of increased nitrogen load on phytoplankton in a phosphorus‐limited lake

Summary Widespread use of artificial fertilisers and the burning of fossil fuels and/or biomass release a large amount of reactive nitrogen into the atmosphere. So far, the effects of increasing nitrogen deposition from the atmosphere have mainly been studied in nitrogen‐limited limnic and marine systems. Interestingly, in phosphorus‐limited lakes, additional nitrogen input might not affect phytoplankton biomass, but rather increase mainly the degree of phosphorus limitation. The resulting effects on plankton communities are difficult to predict and quantify. To estimate the effects of increasing nitrogen load on a spring phytoplankton community in a primarily phosphorus‐limited system, a mesocosm experiment was performed in an oligotrophic lake, in which a gradient of six increasing nitrogen enrichment levels was applied. During the initial phytoplankton growth phase (spring bloom), molar, seston nitrogen:phosphorus ratios increased from 43 to 72 and carbon:phosphorus ratios from 328 to 542 with increasing nitrogen enrichment, indicating increased phosphorus limitation. Three commonly used phytoplankton biomass proxies (phytoplankton biovolume, chlorophyll a and particulate organic carbon) showed only minor responses to nitrogen enrichment. Different groups and species of phytoplankton varied in their responses to the nitrogen enrichment in both the growth phase (spring bloom) and the descending phase (clear water phase). Overall, we detected an effect of nitrogen enrichment on phytoplankton stoichiometry and community composition. The observed changes in the phytoplankton community combined with changes in abundances of heterotrophic nanoflagellates and ciliates indicate bottom‐up driven alterations of the basal food web due to increased nitrogen loads.

The anthropogenic perturbation of the marine nitrogen cycle by atmospheric deposition: Nitrogen cycle feedbacks and the 15N Haber‐Bosch effect

AbstractOver the last 100 years, anthropogenic emissions have led to a strong increase of atmospheric nitrogen deposition over the ocean, yet the resulting impacts and feedbacks are neither well understood nor quantified. To this end, we run a suite of simulations with the ocean component of the Community Earth System Model v1.2 forced with five scenarios of nitrogen deposition over the period from 1850 through 2100, while keeping all other forcings unchanged. Even though global oceanic net primary production increases little in response to this fertilization, the higher export and the resulting expansion of the oxygen minimum zones cause an increase in pelagic and benthic denitrification and burial by about 5%. In addition, the enhanced availability of fixed nitrogen in the surface ocean reduces global ocean N2 fixation by more than 10%. Despite the compensating effects through these negative feedbacks that eliminate by the year 2000 about 60% of the deposited nitrogen, the anthropogenic nitrogen input forced the upper ocean N budget into an imbalance of between 9 and 22 Tg N yr−1 depending on the deposition scenario. The excess nitrogen accumulates to highly detectable levels and causes in most areas a distinct negative trend in the δ15N of the oceanic fixed nitrogen pools—a trend we refer to as the 15N Haber‐Bosch effect. Changes in surface nitrate utilization and the nitrogen feedbacks induce further changes in the δ15N of , making it a good but complex recorder of the overall impact of the changes in atmospheric deposition.

Effects of Elevated Ozone and Nitrogen Deposition on Photosynthetic Characteristics and biomass of Populus cathayana

The open top chambers were used to explore the influences of nitrogen deposition on the response of photosynthetic characteristics of Populus cathayana to ozone. The results showed that the net photosynthetic rate (Pn), apparent electron transport rate (ETR), excitation energy capture efficiency of PSⅡ reaction center (F'v/F'm), coefficient of photochemical quenching (qP), the maximum of carboxylation efficiency (Vcmax) and the maximum rate of electron transport (Jmax) were significantly decreased with the increasing O3 concentration. However, intercellular CO2 concentration (ci) was significantly increased and stomatal conductance (Gs) remained unchanged. There was significant difference in biomass at the end of growing season. However, in a certain extent, nitrogen deposition improved photosynthetic capacity and biomass of P. cathayana. The interaction of O3 and nitrogen deposition was not significant in terms of plant photosynthetic characteristics. The current results provided scientific basis for the protection of P. cathayana in response to the global O3 concentration and nitrogen deposition increase.

Biomass and physiological responses of Quercus robur (L.) young trees during 2 years of treatments with different levels of ozone and nitrogen wet deposition

The root biomass of oak young trees significantly decreased after 2 years of exposure to high levels of ozone, but increased nitrogen wet deposition tended to partly contrast this effect. A 2-year Open-Top Chamber (OTC) experiment with young Quercus robur trees that were exposed to different levels of ozone (O3) and nitrogen deposition was performed in Curno (Northern Italy) for the FP7 Project ECLAIRE. The plants were exposed to four levels of ozone (−40 % of ambient ozone in charcoal-filtered OTCs, −5 % in non-filtered OTCs, and +30 and +75 % in O3-enriched OTCs) and two levels of nitrogen wet deposition (tap water and tap water +70 kg N ha−1 year−1). The stomatal conductance and A/Ci response curves were measured during the two experimental seasons, and in October, the plant dry biomass partition between the roots and stem was assessed. Oak plants were moderately sensitive to O3. After the second year of treatments, the dose–response relationships based on the O3 stomatal flux indicated a 4.6 % of root biomass loss and a 12.1 % of reduction of the number of leaves per 10 mmol O3 m−2 absorbed by plants grown with no nitrogen addition. Ozone also decreased both the stomatal conductance and the maximum carboxylation rate allowed by Rubisco (V cmax) during the first year of treatments. However, the effect on V cmax was lost during the second year, and the plants showed an uncoupling between leaf-level physiological responses and plant-level biomass responses. Increased nitrogen deposition enhanced the growth of plants and partially mitigated the O3 impact on biomass and physiology, but no significant effect of the interaction between the two factors was found. The data that were collected could contribute to the definition of the O3 dose–response relationships based on biomass losses for deciduous trees in Southern Europe climatic conditions and could improve the O3 risk assessment models by providing new information about the effect of increased nitrogen deposition on the ozone impact.

Can litter addition mediate plant productivity responses to increased precipitation and nitrogen deposition in a typical steppe?

AbstractPlant litter is a key component of grassland and plays a major role in terrestrial ecosystem processes. Global climate change has been shown to considerably alter litter inputs to soils, which may feed back to the grassland ecosystem responses to climate change. In order to explore whether litter addition could mediate above and belowground productivity responses to short‐term increases in growing‐season precipitation and nitrogen deposition, we conducted a two‐year study on water, nitrogen and litter addition in Inner Mongolia grassland. After two years of treatments, our results showed that water, nitrogen, and litter addition increased aboveground biomass (AB) and belowground net primary productivity (BNPP). Besides, litter addition increased BNPP responses to water addition. These litter addition effects could be attributed to the influence of litter on soil moisture and soil nitrogen availability, ultimately increasing belowground water use efficiency (WUEBNPP) and plant nitrogen uptake (NUPBNPP). However, litter addition suppressed the aboveground biomass (AB) responses to nitrogen addition under ambient precipitation conditions by affecting soil moisture. In conclusion, our results suggest that ecosystem responses to short‐term increases in growing‐season precipitation and nitrogen deposition could be mediated by the increased litter input caused by climate change.

The fate of plant wax lipids in a model forest ecosystem under elevated CO2 concentration and increased nitrogen deposition

Atmospheric CO2 concentration and nitrogen (N) deposition have been altered by anthropogenic activity and they affect global biogeochemical cycles. It is still not clear how these environmental changes influence the storage and cycling of organic matter (OM) in soils, although this plays a key role in the biogeochemistry of terrestrial ecosystems. Here, we used n-alkanes as biomarkers for plant-derived OM in specific soil fractions. We investigated the effect of elevated CO2 concentration and increased N deposition on the molecular and isotopic (δ13C) composition of n-alkanes in above-ground and below-ground tree biomass (beech and spruce) and soil density fractions.The n-alkane distribution patterns of spruce needles and root biomass were well reflected in those of particulate soil OM. Long chain (C27–34) n-alkanes were preserved in soil by association with soil minerals, while mid-chain (C20–27) n-alkanes from plant biomass and particulate soil OM were ultimately degraded due to lack of physical protection. Renewal of n-alkanes was lower in roots and spruce needles than in beech leaves. Similar low renewal of n-alkanes in soil reflected the low input of n-alkanes from plant biomass to the soil n-alkane pool. n-Alkane biosynthesis in beech leaves was modified under high N deposition and similar effects were observed for n-alkanes in mineral soil fractions and bulk soil. Here, different biosynthesis of n-alkanes in beech leaves under high N deposition consequently led to a modified input of n-alkanes from plant biomass to soil, with a relatively low proportion of new (experimentally-derived) n-alkanes bound to soil minerals.

Mediterranean, invasive, woody species grow larger than their less-invasive counterparts under potential global environmental change.

Revealing biological differences between invasive and noninvasive species is essential for predicting species' distribution changes with global environmental change. While most research has focused on differences between invasive and noninvasive species under favorable conditions using herbaceous species, invasive woody angiosperms are also of great ecological concern. Our study focused on how growth and allocation may change for invasive and noninvasive, mediterranean, woody angiosperms under future conditions caused by global change, specifically increased nitrogen deposition and drought. We tested how seedling functional traits differed between invasive and noninvasive woody angiosperms under different experimental conditions in a greenhouse setting. We compared growth rates and allocation patterns using two levels of soil nitrogen and three levels of watering. We also examined trait log response ratios to increases in nitrogen and increases in water. Our study sampled angiosperm trees and shrubs, incorporating congeneric/confamilial relationships through 13 phylogenetically controlled contrasts. Three functional traits were highly and positively associated with plant invasiveness for most conditions studied: seedling plant mass, leaf area, and height. Invasive species also had significantly higher root mass ratios at low water regardless of nitrogen input. Invasive and noninvasive species had similar log response ratios to increases in nitrogen and watering for studied traits. Mediterranean, woody, invasive species' larger mass, leaf area, and early height advantage under elevated nitrogen input and increased root production in drought conditions may lead to increased invasion of these species with expected global climate change.

Why is the relative abundance of Asterionella formosa increasing in a Boreal Shield lake as nutrient levels decline?

The freshwater diatom Asterionella formosa Hassall is a widely distributed species whose populations have been increasing in the recent sediments of numerous lakes worldwide. This taxon’s proliferation has commonly been associated with nutrient enrichment and, more recently, with twentieth century increases in atmospheric nitrogen deposition. However, a growing number of studies have reported increases in A. formosa in the absence of increased nutrients and have thus raised questions about whether alternative causative factors (such as recent climate warming) may be important. Here we assess the relative importance of nutrients and climate warming on A. formosa by comparing regional air temperature trends and 20 years of annually measured lake water nutrients (total inorganic nitrogen, total nitrogen, and total phosphorus) with past changes in relative abundance of this taxon from a sediment core obtained from a soft-water, Boreal Shield lake (George Lake, Killarney, Ontario). Measured lake water total phosphorus has always been very low and remains so to the present (<10 µg L−1). Total inorganic nitrogen (TIN) and total nitrogen (TN) concentrations, however, show distinct declining trends (p < 0.05) at George Lake since the 1990s, when substantial increases in mean annual and mean winter air temperatures (p < 0.01) were also recorded. These declines in lake water nitrogen concentrations match declines in atmospherically deposited nitrogen in this region. Since the late-1980s and early-1990s, there has been a marked increase in the relative abundance of A. formosa, which had been virtually absent from the lake’s sediment record in earlier intervals. A. formosa trends closely track increasing regional air temperatures, but also clearly coincide with declines in lake water nutrients and decreases in regional nitrogen deposition (p < 0.01). These trends have also occurred in other lakes in the region. Our results show that increases in nitrogen deposition and/or nutrient enrichment are not pre-conditions for increases in the relative abundance of A. formosa. Instead, warming-related changes including longer open water periods, changes in lake mixing regimes, and lake thermal properties might have contributed to the recent increase in the relative abundance of A. formosa in this lake and likely elsewhere.

Rainfall variability and nitrogen addition synergistically reduce plant diversity in a restored tallgrass prairie

Summary Climate change is expected to bring fewer, larger rainfall events and prolonged droughts (i.e. increased rainfall variability). Concurrently, the burning of fossil fuels and reliance on nitrogen (N) fertilizers are expected to continue to increase N availability in many ecosystems. These changes in water and N availability have the potential to alter plant community composition and structure. We manipulated rainfall variability and N inputs in a restored tallgrass prairie over the course of two growing seasons. Greater rainfall variability led to wetter soils throughout the majority of both growing seasons and provided punctuated relief from a severe drought that occurred during the first three months of the experiment. Both rainfall variability‐ and fertilization‐induced increases in resource availability favoured fast‐growing, deeply rooted C3 forbs, particularly the dominant Solidago canadensis, at the expense of species adapted to low resource conditions, particularly C4 grasses and N‐fixing forbs. This change in community composition decreased plant community diversity and evenness in plots receiving both supplemental N and more variable rainfall. Synthesis and applications. These results suggest that future increases in rainfall variability and nitrogen (N) deposition could synergistically alter the structure of prairie restorations and jeopardize restoration targets related to increasing floral diversity. Mitigating N availability in restoration sites may help to maintain prairie diversity as rainfall patterns become more variable.

Effects of nitrogen deposition on nitrogen acquisition bySarracenia purpureain the Adirondack Mountains, New York, USA1

Abstract Human generated emissions to the atmosphere have historically increased inorganic nitrogen (N) deposition throughout the Adirondack Mountains of New York. Nitrogen is generally a limiting nutrient for the purple pitcher plant (Sarracenia purpurea L.). Our objective was to determine the dependence of S. purpurea on atmospherically deposited and insect-derived N sources across an increasing nitrogen deposition gradient. Sampling was conducted at 10 sites, with 104 S. purpurea plants sampled. The effects of increasing nitrogen deposition on morphological characteristics and organic N content of S. purpurea and a noncarnivorous reference plant, Chamaedaphne calyculata L. Moench, Leatherleaf, were examined. Sarracenia purpurea flower and C. calyculata leaf tissues were analyzed for stable nitrogen isotope (δ15N), and foliar N content. Increased nitrogen deposition up to 4.1 kgN*ha−1*yr−1 was correlated with increased plant size and δ15N values of S. purpurea. However, deposition exceeding these levels...

A novel soil manganese mechanism drives plant species loss with increased nitrogen deposition in a temperate steppe.

Loss of plant diversity with increased anthropogenic nitrogen (N) deposition in grasslands has occurred globally. In most cases, competitive exclusion driven by preemption of light or space is invoked as a key mechanism. Here, we provide evidence from a 9-yr N-addition experiment for an alternative mechanism: differential sensitivity of forbs and grasses to increased soil manganese (Mn) levels. In Inner Mongolia steppes, increasing the N supply shifted plant community composition from grass-forb codominance (primarily Stipa krylovii and Artemisia frigida, respectively) to exclusive dominance by grass, with associated declines in overall species richness. Reduced abundance of forbs was linked to soil acidification that increased mobilization of soil Mn, with a 10-fold greater accumulation of Mn in forbs than in grasses. The enhanced accumulation of Mn in forbs was correlated with reduced photosynthetic rates and growth, and is consistent with the loss of forb species. Differential accumulation of Mn between forbs and grasses can be linked to fundamental differences between dicots and monocots in the biochemical pathways regulating metal transport. These findings provide a mechanistic explanation for N-induced species loss in temperate grasslands by linking metal mobilization in soil to differential metal acquisition and impacts on key functional groups in these ecosystems.

模拟氮沉降对华西雨屏区天然常绿阔叶林凋落叶分解过程中基质质量的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 模拟氮沉降对华西雨屏区天然常绿阔叶林凋落叶分解过程中基质质量的影响 DOI: 10.5846/stxb201601080054 作者: 作者单位: 四川农业大学,四川农业大学,四川农业大学,四川农业大学,四川农业大学,四川农业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家“十二五”科技支撑资助项目（2010BACO1A11）；四川省“十二五”农作物育种攻关资助项目（2011NZ0098-10） Effects of simulated nitrogen deposition on the substrate quality of foliar litter in a natural evergreen broad-leaved forest in the Rainy Area of Western China Author: Affiliation: Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University,Sichuan Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为理解氮沉降对华西雨屏区天然常绿阔叶林凋落物分解过程的影响，采用立地控制实验和凋落物分解袋法，研究了低氮沉降（L，50 kg N hm-2 a-1）、中氮沉降（M，150 kg N hm-2 a-1）和高氮沉降（H，300 kg N hm-2 a-1）对华西雨屏区天然常绿阔叶林凋落叶分解过程中基质质量的影响。结果表明：N沉降抑制了凋落叶的分解，并随着N沉降量的增加，抑制作用增强。N沉降遏制了凋落叶的C、N释放和纤维素降解，促进了P释放。N沉降提高了凋落叶的C/P比，中氮和高氮处理提高了凋落叶C/N比。N沉降显著增加了凋落叶N、木质素和纤维素的含量，分解1年后，各N沉降处理的木质素/N和纤维素/N均显著高于对照。N沉降提高了质量残留率与C/N、木质素/N和纤维素/N的相关性，降低了与C/P的相关性。可见，模拟N沉降显著影响了华西雨屏区天然常绿阔叶林凋落叶分解过程中的基质质量，进而影响了凋落叶的分解过程。 Abstract:Litter, an essential component of the forest ecosystem, plays an important role in maintaining site fertility, sequestering carbon, and nursing soil biodiversity. However, the substrate quality of decomposing litter is affected by increasing nitrogen deposition mainly because of fossil fuel combustion and chemical fertilizer production and use. Theoretically, decomposition of atmospheric nitrogen may have a strong impact on litter decomposition in three ways. The first approach is that nitrogen deposition may alter the chemical components of litter by direct nitrogen addition. The second approach is that nitrogen addition can change the growth of plants and carbon and nutrient allocations in plant tissues and indirectly lead to changes in litter substrate quality. The third approach is that nitrogen deposition may result in soil acidification, and, in turn, have strong effects on litter substrate quality indirectly. To date, there is limited information on the changes in litter substrate quality due to atmospheric nitrogen deposition in the Rainy Area of Western China. To understand the effects of increasing nitrogen deposition on the litter decomposition process in natural evergreen broadleaved forests in the Rainy Area of Western China, a field litter decomposition experiment was conducted in a natural evergreen broad-leaved forest in Ya'an City. Between November 2013 and November 2014, we conducted the field experiment by using the litterbag method. Four levels of nitrogen deposition were set:control (0 kg N hm-2 a-1), low nitrogen (50 kg N hm-2 a-1), medium nitrogen (150 kg N hm-2 a-1), and high nitrogen (300 kg N hm-2 a-1). The results indicated that nitrogen deposition significantly influenced litter substrate quality, and concentrations of carbon, nitrogen, and cellulose in the leaf litter were found to increase significantly with nitrogen addition. Nitrogen deposition also affected C/P and C/N of the leaf litter; all nitrogen deposition treatments significantly increased C/P, whereas medium nitrogen and high nitrogen treatments significantly increased C/N. Since nitrogen deposition significantly increased the nitrogen concentration of the litter, exacerbating the accumulation of litter lignin and cellulose, after decomposing for 1 a, lignin/N and cellulose/N after each nitrogen deposition treatment were significantly higher than those in the control. The correlation coefficient of mass remaining of foliar litter with C/N, lignin/N, and cellulose/N was increased by nitrogen deposition, while C/P was reduced. Thus, simulated nitrogen deposition influenced the substrate quality of foliar litter in natural evergreen broad-leaved forest in the Rainy Area of Western China, and influenced the decomposition process of the litter. 参考文献 相似文献 引证文献

The ‘teflon basin’ myth: hydrology and hydrochemistry of a seasonally snow-covered catchment

Background: Snow and ice melt provide sensitive indicators of climate change and serve as the primary source of stream flow in alpine basins.Aims: We synthesise the results of hydrological and hydrochemical studies during the period 1995–2014, building on a long history of earlier work focused on snow and water on Niwot Ridge and the adjacent Green Lakes Valley (GLV), which is part of the Niwot Ridge Long Term Ecological Research site (NWT LTER).Methods: These studies are discussed in the context of how snow, snowmelt and runoff reflect changing local climate. We review recent results of snow, snowmelt, hydrology and hydrochemistry from the plot to the basin scale, utilising new tools such as continuous global positioning system (GPS) measurements of snow depth, along with remotely-sensed measurements of snow-covered area and melt, combined with long-term measurements of snow properties, discharge and solute and isotopic content of water.Results and Conclusions: Surface–groundwater interactions are important components of water quantity and quality in alpine basins. Some or most snowmelt infiltrates underlying soils and bedrock, transporting soil and bedrock products to surface waters. Infiltrating snowmelt, along with increased melt of stored ice, increases the hydrologic connectivity between the terrestrial and aquatic systems. Alpine basins are being impacted by increases in atmospheric nitrogen deposition, which has caused changes in soil microbial processes such as nitrification. Nitrate, dissolved organic carbon and dissolved organic nitrogen are thus flushed from soils and talus to streams. Our long-term results show that alpine catchments, such as Green Lake 4 at NWT LTER+, have the greatest sensitivity and least resilience to climate warming, with any warming leading to increased water yields.