Local distribution of C3 and C4 grasses in sites of overlap on Mount Kenya

Abstract

Summary.A zone of C3-C 4 grass overlap has been identified on the northern slopes of Mount Kenya at elevations of 2,800-3,200 m. At higher elevations, C 3 grasses predominate; below, C4 grasses predominate. At each of three elevational sites of overlap, a series of transects was surveyed for C 4 and C 3 grass composition. All transects were located in structurally similar vegetation (high elevation grassland) within 150 m of each other. Transects were run in a variety of topographic situations. Within each transect, several environmental parameters were measured. Both unweighted (species presence/absence) and weighted (by frequency) measures of %C 4 composition were significantly correlated with dry season soil moisture. Drier transects contain significantly more C 4 species, in greater frequency, than wetter transects. Other correlations of C4 composition (e.g. factors which tend to parallel soil moisture) were also found. This local trend parallels the larger scale tendency of C a grasses to replace C 4 grasses with increasing elevation. Finer scale habitat partitioning may account for C3-C 4 overlap within transects.

Phytolith indices as proxies of grass subfamilies on East African tropical mountains

“…However, in open areas such as grasslands, shrublands and open forests, Panicoideae grasses are often C 4 and the Ic index can be reasonably interpreted as a proxy of C 3 versus C 4 grass abundance. An increase in the abundance of Pooideae grasses at the expense of Panicoideae grasses with elevation, have been observed along altitudinal gradients, all over the inter-tropical world (Costa Rica, Hawaï, East-Africa, Argentina) (Chazdon, 1978;Tieszen et al, 1979;Livingstone and Clayton, 1980;Young and Young, 1983;Cabido et al, 1997). These studies investigated open formations where Panicoideae grasses were all C 4 .…”

“…At low pCO 2, and high temperature, C 4 grasses abundance and more generally C 4 plants are also inversely correlated with soil moisture (e.g. Young and Young, 1983;Liu et al, 2005). Finally, the sensitivity of C 3 and C 4 grass and plants toward environmental factors is not well constrained and is likely to differ from one ecosystem to another and the climate pattern at key periods of time (e.g.…”

“…(mid-point: mean values of the selected variable; the box: ±standard errors (S-E); and whiskers:+/− standard deviation (S-D)). c) Ic values calculated for all the samples (Masoko lake, Mount Rungwe and Mount Kenya) are compared to available botanical data (% of C 3 grass species) published for East Africa(Tieszen et al, 1979;Livingstone and Clayton, 1980;Young and Young, 1983;Wooller et al, 2001). Data are reported using 10 box plots with equal interval from 0 to 5200 m a.s.l (mid-point: mean values of the selected variable; the box:+/− standard errors (S-E); and whiskers:+/−standard deviation (S-D)).…”

Late Quaternary vegetation changes around Lake Rutundu, Mount Kenya, East Africa: evidence from grass cuticles, pollen and stable carbon isotopes

“…1). A gap in the forest on the northern flank of Mount Kenya (Young and Young, 1983) corresponds to relatively low annual rainfall receipts and is possibly the result of drier conditions and/or human disturbance (Bussmann, 1994). Lake Rutundu is located at 3078 m a.s.l.…”

Microsite characteristics of Muhlenbergia richardsonis (Trin.) Rydb., an alpine C4 grass from the White Mountains, California

“…Most information on C 4 plant distribution in cold climates comes from floristic accounts that are largely descriptive (Teeri and Stowe 1976;Tieszen et al 1979;Sage et al 1999). C 4 plants at high altitude or latitude have been observed to occur primarily on drought-prone (Young and Young 1983 for C 4 grasses on Mt Kenya) or south-facing slopes (Schwarz and Redman 1988 for the Canadian Boreal zone); however, these studies lack microclimate information. To fully understand the relationship between temperature and success of C 4 plants in low-temperature environments, it is necessary to examine both the microsite distribution and the related microclimate characteristics of the C 4 species native to cold climates.…”