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Nâ‚‚-fixing tropical legume evolution: a contributor to enhanced weathering through the Cenozoic?
Fossil and phylogenetic evidence indicates legume-rich modern tropical forests replaced Late Cretaceous palm-dominated tropical forests across four continents during the early Cenozoic (58–42 Ma). Tropical legume trees can transform ecosystems via their ability to fix dinitrogen (N₂) and higher leaf N compared with non-legumes (35–65%), but it is unclear how their evolutionary rise contributed to silicate weathering, the long-term sink for atmospheric carbon dioxide (CO₂). Here we hypothesize that the increasing abundance of N₂-fixing legumes in tropical forests amplified silicate weathering rates by increased input of fixed nitrogen (N) to terrestrial ecosystems via interrelated mechanisms including increasing microbial respiration and soil acidification, and stimulating forest net primary productivity. We suggest the high CO₂ early Cenozoic atmosphere further amplified legume weathering. Evolution of legumes with high weathering rates was probably driven by their high demand for phosphorus and micronutrients required for N₂-fixation and nodule formation
Scented grasses in Norway - Identity and uses
Published version. Source at http://doi.org/10.1186/s13002-015-0070-y.Background: Some grass species are richer in coumarin and thus more sweetly scented than others. These have
been eagerly sought after in parts of Norway, but the tradition has been weakly documented, both in terms of the
species collected, their vernacular names, and uses.
Methods: Based on literature data and a substantial body of information collected during my own ethnobotanical
field work, artefacts and voucher specimens, the grass species are identified, and their uses clarified.
Results: In Norwegian literature, the tradition of collecting and using scented grasses has received little attention,
and past authors largely refer it to Anthoxanthum spp. The tradition’s concentration to the Sámi strongholds of
northernmost Norway, and most authors’ lacking knowledge of the Sámi language, have contributed to the weak
and misleading coverage in previous publications. Coumarin-rich grass species are well known in folk tradition in
northernmost Norway, as luktegress (Norwegian, “scent grass”), háissasuoidni (North Sámi, “scent grass”), hajuheinä
(Finnish, “scent grass”), or similar terms. They have been (and still are) frequently collected, and used as perfume, for
storing with clothes, and a number of other purposes. Despite literature records identifying the species used as
Anthoxanthum odoratum coll. (including A. nipponicum), the main source utilized in North Norway is Hierochloë
odorata, both ssp. arctica and ssp. odorata. Anthoxanthum nipponicum and Milium effusum are alternative, but
infrequently used sources of material, depending on local tradition and availability.
Conclusion: By far the most important grass species hiding behind the “scented grass” tradition in Norway is
Hierochloë odorata. Anthoxanthum nipponicum is also used, but much less frequently, and only a single record
confirms the use of Milium effusum. Only the foliage of Hierochloë provides suitable material for making traditional
braids. The three major ethnic groups in Norway have all utilized scented grasses as perfume and for storing with
clothes, but the tradition’s geographical concentration to the far north of Norway (Finnmark and NE Troms),
suggests that it has originally mainly been a Sámi tradition, adopted by their neighbours