Geographical and environmental distribution of C3 and C4 grasses in the Sinai, Negev, and Judean deserts

Abstract

The relation between photosynthetic pathway and habitat of the grass species recorded in the desert regions of Sinai, Negev, and Judea was investigated. The climatic conditions and micro-environments in the study area vary considerably, and the distribution of the various species is found to conform to specific patterns which reveal the adaptive advantages of the different photosynthetic pathways. There is also a distinct correlation between the phytogeographic origin of the grass species and the photosynthetic pathways that they utilize.The survey shows that the majority of the grass species in the region are of the C type and all except one of these species belong to the Holarctic domain. This is in accordance with the fact that the region forms part of the Mediterranean winter rainfall regime and that C species have an adaptive advantage where minimum temperatures are low during the winter growing season.The occurence of C species increases with decreasing rainfall and they dominate in those districts where temperatures are high throughout the year. These C grasses are of both Holarctic and Palaeotropic origin according to the classification adopted here, but they are essentially all elements of the Saharo-Arabian, Irano-Turanian, Sudanian, or Tropical phytogeographic regions and are not typical of the Mediterranean or Euro-Siberian floras. The plants with multi-regional distributions that occur in Mediterranean communities may well be intrusive.Analysis of the three subtypes of the C species suggests that the malate-forming NADP-me grasses grow where water stress is not a dominating factor, while the aspartateforming NAD-me grasses are more successful under xeric conditions. The PEP-ck species are not abundant and form an intermediate group between the NADP-me and NAD-me subtypes.

Phylogenetic analyses reveal the shady history of C 4 grasses

“…Furthermore, both experimental measurements of photosynthetic light use efficiency (termed "quantum yield"), and predictions of leaf models of C 3 and C 4 photosynthesis provide strong evidence that C 4 grasses outperform C 3 grasses at higher temperatures (5,(14)(15)(16). Most studies concerning C 4 grasses and precipitation have focused on C 3 /C 4 mixed temperate grassland systems, where the timing of C 4 growth often is restricted to periods with significant rainfall (12,13,17,18).…”

Dating of Groundwater Recharge in Two Small Adjacent Aquifers in Israel and Their Initial 14C Activities

“…These results are similar to those of the Judea Group aquifer of the Samaria hills (Kroitoru 1987). The  13 C value of -12.2‰ to -12.8‰ seen in the En Alon and En Kedem springs ( Figure 1, Table 2) is expected in groundwater from marine carbonate-rich ( 13 C = ~0) terrain covered by C 3 plants ( 13 C = ~ -25‰) in the recharge region (Vogel et al 1986), and dissolution of CO 2 in equal proportions from the marine carbonate and the soil gas.…”

Desert Habitation History by14C Dating of Soil Layers in Rural Building Structures (Negev, Israel): Preliminary Results from Horvat Haluqim

“…These have a different photosynthesis than C 3 plants and hence less negative ô 1 3 C values. Most C 4 plants are short-lived and various annual grasses belong to this group, as shown by a botanical study in the Negev, Sinai, and Judean deserts (Vogel et al 1986). The occasional charred organic 398 H J Bruins et al spots in the archaeological soil seem to result from habitation.…”