Abstract
(1) In fifteen lowland grasslands, as the quotient of root density in the lower (5-10 cm) layer of soil to that in the upper (0-5 cm) layer increases so there is a decrease in number of species per unit area and in an index of dominance. (2) This quotient, a measure of the heterogeneity of root development, was not related to the difference in pH or concentration of extractable phosphate or potassium in the two soil layers. (3) In a pot experiment an infertile acid sand and a fertile calcareous loam, either mixed or in distinct upper and lower soil layers, were used to grow a standard mixture of five grassland plants. Dominance of one or two species was less marked where there was a distinct lower layer of soil, and this was true irrespective of the total above-ground biomass of all plants. (4) The amount of calcium in the shoots indicates that the species differed in rooting depth, although the spatial distribution of the root system was not analysed. (5) Soil heterogeneity can therefore be shown experimentally to influence the coexistence of species. The distribution of roots in the field may be of great importance in this respect.
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Claims 5
Claim · model-written summary
Greater lower to upper root density ratio corresponded to fewer grassland species per unit area.
Verbatim
e0“In fifteen lowland grasslands, as the quotient of root density in the lower (5-10 cm) layer of soil to that in the upper (0-5 cm) layer increases so there is a decrease in number of species per unit area”
Claim · model-written summary
Greater lower to upper root density ratio corresponded to lower dominance index.
Verbatim
e0“In fifteen lowland grasslands, as the quotient of root density in the lower (5-10 cm) layer of soil to that in the upper (0-5 cm) layer increases so there is a decrease in number of species per unit area and in an index of dominance”
Claim · model-written summary
Root development heterogeneity was unrelated to soil layer differences in pH, extractable phosphate or potassium.
Not reportedTaxonDirection
Verbatim
e0“This quotient, a measure of the heterogeneity of root development, was not related to the difference in pH or concentration of extractable phosphate or potassium in the two soil layers”
Claim · model-written summary
A distinct lower soil layer reduced dominance by one or two grassland species irrespective of biomass.
- Taxon
- plantsViridiplantaee0
- Treatment
- distinct lower layer of soile0
- Outcome
- Dominance of one or two speciese0
- Direction
- less markede0
- Qualifier
- irrespective of the total above-ground biomass of all plantse0
Not reportedComparator
Verbatim
e0“Dominance of one or two species was less marked where there was a distinct lower layer of soil, and this was true irrespective of the total above-ground biomass of all plants”
Claim · model-written summary
Shoot calcium indicated species differences in rooting depth.
Not reportedDirection
Verbatim
e0“The amount of calcium in the shoots indicates that the species differed in rooting depth”