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51.
通过对福建万木林自然保护区常绿阔叶林群落101种乔木、灌木叶的N、P化学计量学特征分析,结果显示:同一群落内种间的叶N、P含量和N/P存在极大变异,叶N含量变化范围为10.76～34.14 mg.g-1,几何平均值为17.33 mg.g-1;叶P含量变化范围为0.28～2.93mg.g-1,几何平均值为0.94 mg.g-1;N/P变化范围为6.47～34.90,几何平均值为18.49.群落叶N/P平均水平均高于全球、全国和中国东部南北样带的平均水平,说明本区的常绿阔叶林更易受P限制.在不同生长型中,只有落叶木本与常绿木本、落叶乔木和常绿乔木的叶片N、P含量存在显著差异(P<0.001;P<0.05),而不同生长型叶片N/P无显著差异.不同科之间,只有大戟科叶的N含量与其他科之间存在差异(P<0.05),其余科之间的N、P含量和N/P均不存在显著性差异. 相似文献
52.
We used a one dimensional, multi-element model to simulate the primary production (PP), recycling and export of organic matter at Stn. ALOHA, near Hawaii. We compared versions of the model with and without the cycling of dissolved organic matter (DOM) via the Microbial Food Web (MFW). We incorporated recently published measurements of high C:N ratios for uptake by diazotrophs. For other phytoplankton we included a formulation for overflow production of dissolved organic carbon (DOC), which occurs under nutrient-limited, light-replete conditions. We were able to match the observed mean DOC profile near the surface with both models, by tuning only the fraction of overflow DOC that is labile. The simulated bulk C:N remineralization ratio from the MFW model agreed well with a data-based estimate for the North Pacific subtropical gyre, but that from the Base model was too low. This is because the MFW model includes bacteria, with their low-C:N biomass. Simulated mean PP was lower than observed by 10% (Base) and 27% (MFW). This is consistent with the expectation that the 14C-method measures something greater than net production. DOC accounted for approximately half of simulated PP, most of this being overflow DOC. We find that overflow production and the MFW are key processes for reconciling the various data and PP measurements at this oligotrophic site. The impact of bacteria on the C:N remineralization ratio is an important link between ecosystem structure and the cycling of carbon. 相似文献
53.
Field geometry, petrography and geochemistry of a dolomitization front (Late Jurassic, central Lebanon) 总被引：1，自引：1，他引：1
This contribution describes the field geometry, petrography and geochemistry of a well-exposed dolomitization front in Upper Jurassic carbonates, and attempts to highlight the sedimentological, structural and relative sea-level controls on multiphase dolomitization and related diagenetic events. The data presented reflect the superposition of various diagenetic phases which have resulted in a single dolostone body, whose dimensions are well defined in the field. Local microbial intraclastic dolomites of Late Tithonian age accumulated in a hypersaline lagoon during relative sea-level fall. These pre-date beige hydrothermal dolostones (51 to 55 mol% CaCO3 ; δ 18 O: −9·3 to −4·0‰ V-PDB; δ 13 C: −1·5 to +2·1‰ V-PDB; 87 Sr/86 Sr: 0·70742; matrix porosity: ≈6%; Klinkenberg permeability: ≈0·5 mD), whose dolomitizing fluid circulated along faults and invaded the nearby facies. First, the burrows were dolomitized, then the bulk rocks, resulting in the investigated 'tongue'-shaped dolomite body. Upon Late Jurassic–Early Cretaceous uplift, near-surface water percolated through – and altered – the underlying beige dolostones. This event was followed by a ferroan dolomite cement phase, which occurred during further burial. This contribution, featuring a well-defined geometric pattern of a dolomitization front with a large petrographic and geochemical data set, may also serve as a case study illustrating the complexity of superimposed diagenetic processes which have to be taken into account in modelling exercises of multiphase hydrothermal dolomitization. 相似文献
54.
Calcitized Jurassic dolostones from central Mount Lebanon (Kesrouane Formation) are discussed utilizing petrographic, mineralogical and geochemical data. In particular, two sequential extraction methods for both major/trace elements and stable isotope analyses provide results that support and refine conventional bulk analyses data. The new data demonstrate that the major dedolomitization phase of the investigated Jurassic carbonates occurred as a result of the migration of karst‐related meteoric waters (characterized by soil‐derived carbon, and estimated δ18OV‐SMOW composition between ?7·2‰ and ?3·4‰) into previously dolomitized horizons within the limestone rock, during the final uplift and emergence of Mount Lebanon, after Palaeogene time. The study demonstrates that, in this case, the mechanisms of dedolomitization and their resulting fabrics are controlled primarily by the texture of the original dolomite rock. Pervasively dolomitized rocks, where the micritic matrix is entirely dolomitized, show calcitization mainly through dissolution/precipitation. By contrast, the rock textures that still include a considerable amount of limey micritic matrix – spared from dolomitization – are more prone to mole per mole and mimic replacement of the dolomite crystals by calcite. 相似文献
55.
两种白刺叶片及沙堆土壤化学计量学特征的比较 总被引：3，自引：0，他引：3
在植物叶片氮、磷化学计量学研究中,氮磷比常作为判断土壤养分限制性的指标,其适用范围从海洋、湖泊等水生生态系统扩展到陆地生态系统。以生长在民勤绿洲的毛瓣白刺(Nitraria praevisa)和唐古特白刺(N. tangutorun)为研究对象,分别测定叶片N、P含量以及沙堆各层土壤有机质、N、P含量,以探讨两种白刺叶片及其沙堆土壤化学计量学特征的关系。研究结果表明:①白刺叶片的N、P含量之间存在显著的正相关关系;②两种白刺沙堆各项土壤养分指标差异极显著(P<0.01);③毛瓣白刺沙堆土壤的N含量在0～20 cm土层存在富集现象,唐古特白刺沙堆土壤的有机质、N、P含量在20～40 cm土层存在富集现象;④在水分为最主要的限制性因子的荒漠生态系统中,能否以叶片N∶P作为判定营养元素限制性的标准,值得进一步探讨。 相似文献
56.
生态系统氮磷比化学计量特征研究进展 总被引：11，自引：4，他引：7
通过对国内外关于氮磷比化学计量特征研究文献的大量阅读,总结了在陆地生态系统和水域生态系统中氮磷比化学计量特征的意义。在陆地生态系统中,土壤中的氮磷比与固氮共生体及非共生体的生物固氮量呈反比例关系;土壤中的氮磷比化学计量特征发生变化会影响植被动态;土壤中氮磷比化学计量特征的变化对物种多样性及生产力产生影响,尤其是磷限制濒危物种的生产力及丰富度;植物体中的氮磷比化学计量特征可以体现氮和磷两种营养元素的供应状况及相对有效性,对植被恢复和濒危物种管理工作起到重要作用。在水域生态系统中,水体中的氮磷比与水生生物的固氮量呈反比例关系,并且会影响水生植物的生长及水生生物群落的组成。 相似文献
57.
古尔班通古特沙漠典型灌木群落土壤化学计量特征及其影响因素 总被引：6，自引：2，他引：4
对古尔班通古特沙漠3种典型灌木群落77个样地的0～10 cm层土壤及环境因子进行调查取样,分析了土壤有机碳（C）、全氮（N）、全磷（P）及全钾（K）的化学计量特征及其影响因素。结果表明：土壤C、N、P、K含量均值分别为1.057、0.133、0.319、14.11 g·kg-1,C∶N、C∶P、C∶K、N∶P、N∶K、P∶K值分别为8.124、3.486、0.099、0.434、0.013、0.034。本研究土壤C、N、P养分元素含量及其化学计量比均远低于全球及全国平均水平。C∶N和P含量具有较高的稳定性（CV=19.26%和22.46%）,而K、C∶K、N∶K和P∶K变异性较强（CV=52.17%～80.30%）。土壤化学计量特征在不同群落类型间、不同结皮类型间均有一定差异。C-N、C-K、P-K之间以及土壤养分与其化学计量比之间具有显著的非线性耦合关系,可用二次函数、幂函数或指数函数等非线性函数表征。相关性分析和CCA排序分析表明,除C∶N不受所调查环境因子影响外,土壤化学计量特征主要受经度、纬度、年降水量、生物结皮发育等级、电导率及海拔的影响。 相似文献
58.
NaCl胁迫对骆驼蓬幼苗液泡膜H+-ATPase和H+-PPase活性的影响 总被引：5，自引：3，他引：2
研究了不同浓度NaCl胁迫对骆驼蓬幼苗Na+、K+含量及液胞膜H+-ATP酶(H+-ATPase)和H+-焦磷酸酶(H+-PPase)活性的影响。结果表明,NaCl胁迫浓度的增加使骆驼蓬幼苗根、叶中的K+含量下降,Na+含量和Na+/K+比及K+对Na+的吸收和运输选择性增高;根、叶液胞膜H+-ATPase和H+-PPase活性升高,H+-ATP酶耦联比率无显著变化;根液胞膜依赖ATP和PPi的质子泵活性及Na+/H+逆向转运活性先升后降,叶依赖ATP的质子泵活性及Na+/H+逆向转运活性升高,依赖PPi的质子泵活性先升后降。说明液泡膜H+-ATPase和H+-PPase驱动的质子泵和Na+/H+逆向转运活性对Na+在液泡内的积累及其骆驼蓬的耐盐性起重要作用。 相似文献
59.
We describe the impact of an open-ocean convection event on nutrient budgets, carbon budget, elemental stoichiometry, phytoplankton biomass and activity in the Northwestern Mediterranean Sea (NWM). In the convective episode examined here we estimated an input of nutrients to the surface layer of 7.0, 8.0 and 0.4×108 mol of silicate, nitrate and phosphate, respectively. These quantities correspond to the annual nutrient input by river discharges and atmospheric depositions in the Gulf of Lion. Such nutrient input is sufficient to sustain new primary production from 46 to 63 g C m−2 y−1, which is the same order of magnitude found in the NWM open waters. Our results together with satellite data analysis, propose new scenarios that explain the origin of the spring phytoplankton bloom occurring in NWM. 相似文献
60.
UM Scharler MJ Ayers AM de Lecea M Pretorius ST Fennessy JA Huggett 《African Journal of Marine Science》2016,38(1):S193-S203
Riverine influences on nearshore oceanic habitats often have detrimental consequences leading to algal blooms and hypoxia. In oligo- to mesotrophic systems, however, nutrient delivery via rivers may stimulate production and even be a vital source of nutrients, as may nutrient supplements from upwelling. We investigated the nutrient content (C, N, P) and stoichiometry of sediment, and several pelagic, benthopelagic and benthic species in the KwaZulu-Natal (KZN) Bight, a narrow shelf area on the south-east coast of South Africa, bordering the Agulhas Current. Three suggested nutrient sources to the bight are the Thukela River in the central region of the bight, upwelling in the northern part and a semi-permanent eddy (Durban Eddy) in the southern part. Elemental content of the various groups studied showed significantly higher values for most groups at the site near the Thukela River. C:P and N:P were highest in the southern part of the bight, and lowest near the Thukela Mouth or at Richards Bay in the north, indicating the latter were the P-richer sites. Sediment organic matter showed lowest elemental content, as expected, and zooplankton stoichiometry was highest compared to all other biotic groups. Environmental heterogeneity played a greater role in organismal C, N and P content and stoichiometry compared to phylogeny, with the exception of the differences in C:P and N:P of zooplankton. From this bight-wide study, the higher elemental content and lower ratios at the Thukela Mouth site supported previous findings of the importance of coastal nutrient sources to the bight ecosystem. Reductions in river flow for water use in the catchment areas may therefore have negative consequences for the productivity of the entire ecosystem. 相似文献