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Dissolved Organic nitrogen in Mediterranean Ecosystems

Pedosphere 2011年第3期21卷 309-318页

作者： M.DELGADO-BAQUERIZO F.COVELO A.GALLARDO Department of Physical Chemical and Natural Systems University Pablo de Olavide Ctra. de Utrera km.1Seville 41013 (Spain)

Dissolved organic nitrogen （DOn） in soils has recently gained increasing interest because it may be both a direct n source for plants and the dominant available n form in nutrient-poor soils, however, its prevalence in Mediterranean ecosystems remains unclear. The aims of this study were to i） estimate soil DOn in a wide set of Mediterranean ecosystems and compare this levels with those for other ecosystems; ii） describe temporal changes in DOn and dissolved inorganic nitrogen （DIn） forms （nH＋ and nO3）, and characterize spatial heterogeneity within plant communities; and iii） study the relative proportion of soil DOn and DIn forms as a test of Schimel and Bennett＇s hypothesis that the prevalence of different n forms follows a gradient of nutrient availability. The study was carried out in eleven plant communities chosen to represent a wide spectrum of Mediterranean vegetation types, ranging from early to late successional status. DOn concentrations in the studied Mediterranean plant communities （0-18.2 mg n kg-1） were consistently lower than those found in the literature for other ecosystems. We found high temporal and spatial variability in soil DOn for all plant communities. As predicted by the Schimel and Bennett model for nutrient-poor ecosystems, DOn dominance over ammonium and nitrate was observed for most plant communities in winter and spring soil samples. However, mineral-n dominated over DOn in summer and autumn. Thus, soil water content may have an important effect on DOn versus mineral n dominance in Mediterranean ecosystems

关键词： dissolved inorganic nitrogen nitrogen cycle soil ammonium soil n availability soil nitrate

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The relative and combined effects of herbivore assemblage and soil nitrogen on plant diversity

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Science China(Life Sciences) 2022年第4期65卷 830-837页

作者： Minna Zhang Bai Liu Guangyin Li Yingying Kuang Xiuquan Yue Shicheng Jiang Jushan Liu Ling Wang Institute of Grassland Science Key Laboratory of Vegetation Ecology of the Ministry of EducationJilin Songnen Grassland Ecosystem National Observation and Research StationNortheast Normal UniversityChangchun130024China

Plant diversity can be affected by both herbivore grazing and soil resources. However, it is unclear if the joint effects of herbivores and soil resources might vary with components of plant diversity. Here, we evaluated the relative and combined effects of herbivore assemblage and soil nitrogen(n) quantity and heterogeneity on the α and β components of plant diversity in a grassland that was subjected to four years of grazing under differing herbivore assemblages(no grazing, cattle grazing, sheep grazing, and mixed grazing). We found that herbivore assemblage combined with soil n quantity explained 41% of the variation in plant α-diversity, while herbivore assemblage combined with soil n heterogeneity explained 15% of the variation in plant β-diversity. The independent effects of herbivore assemblage explained more than those of soil n for both α-and β-diversity(α-diversity: 12% vs. 4%;β-diversity: 18% vs. 16%). We concluded that the effects of herbivores are stronger than those of soil n,and that grazing-induced changes in soil resources are important drivers of plant diversity change, especially α-***, we suggest that managing herbivore species by accounting for the effects that their grazing can have on soil resources may be significant for plant diversity maintenance.

关键词： plant diversity large herbivore resource heterogeneity soil n availability α-diversity β-diversity

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