caa a22 4500 477110193 CHVBK 20180405111606.0 cr unu---uuuuu 170330e19960401xx s 000 0 eng 10.1007/BF00012051 doi (NATIONALLICENCE)springer-10.1007/BF00012051 Dynamics of energy and nutrient concentration and construction cost in a native and two alien C4 grasses from two neotropical savannas [Elektronische Daten] [Zdravko Baruch, José Gómez] In Venezuela, the alien grasses Melinis minutiflora Beauv. and Hyparrhenia rufa (Nees.) Stapf tend to displace the native savanna plant community dominated by Trachypogon plumosus (Humb. and Bonpl.) Nees. This occurs in either relatively wetter and fertile highland savannas or in drier and less fertile lowland savannas. Although the native and aliens are perennial C4 grasses, higher net assimilation leaf biomass per plant and germination rate of the latter are some causes for their higher growth rates and for their competitive success. The objective of this study is to compare seasonal tissue energy, N, P and K concentrations and the calculated construction costs (CC) between the native grass and either one of the alien grasses from lowland and highland savannas. We predict that, in order to out-compete native plants, alien grasses should be more efficient in resource use as evidenced by lower tissue energy and nutrient concentrations and CC. Tissue energy and nutrient concentration were measured throughout the year and compared between M. minutiflora and the co-occurring local population of T. plumosus in a highland savanna and between H. rufa and its neighbor local population of T. plumosus in a lowland savanna. CC was calculated from energy, N and ash concentrations considering ammonium as the sole N source. Differences between co-occurring species, T. plumosus populations, seasons, and organs were analyzed with ANOVA. Highland and lowland grasses differed in concentration and allocation of energy and nutrients whereas the differences between alien and native grasses were specific for each pair considered. Highland grasses had higher energy, N, P and CC than lowland grasses. These variables were always lowest in the culms. In the more stressed lowland site, tissue energy and nutrient concentrations decreased significantly during the dry season except in the roots of both grasses which had the highest energy and nutrients concentrations during the drought. This seasonal response was more marked in the local lowland population of T. plumosus in which maximum CC alternated seasonally between leaves and roots. Energy and nutrient concentrations and CC were the lowest in H. rufa. In the lowland savannas, the higher efficiency of resource use in the invader grass contributes to its higher competitive success through increased growth rate. In the highlands, overall tissue energy concentration and CC, but not N nor P concentration, were lower in the fast growing M. minutiflora but seasonal differences were lacking. The higher leaf CC in T. plumosus can be attributed to the higher proportion of sclerenchyma tissue which is more expensive to construct. Considering CC, both fast growing alien grasses are more efficient in resource use than the co-occurring native grass. However, the role of CC explaining the competitive success of the former, through higher growth rates, is more evident in the more stressful environment of the lowland savanna. Kluwer Academic Publishers, 1996 construction costs nationallicence energy concentration nationallicence mineral nutrient concentration nationallicence savannas nationallicence tropical C4 grasses nationallicence Venezuela nationallicence Baruch Zdravko Departamento Estudios Ambientales, Universidad Simón Bolívar, Apartado 89000, 1080, Caracas, Venezuela aut Gómez José Departamento Estudios Ambientales, Universidad Simón Bolívar, Apartado 89000, 1080, Caracas, Venezuela aut Plant and Soil Kluwer Academic Publishers; http://www.wkap.nl 181/2(1996-04-01), 175-184 0032-079X 181:2<175 1996 181 11104 https://doi.org/10.1007/BF00012051 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00012051 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Baruch Zdravko Departamento Estudios Ambientales, Universidad Simón Bolívar, Apartado 89000, 1080, Caracas, Venezuela aut NATIONALLICENCE 700 1- Gómez José Departamento Estudios Ambientales, Universidad Simón Bolívar, Apartado 89000, 1080, Caracas, Venezuela aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; http://www.wkap.nl 181/2(1996-04-01), 175-184 0032-079X 181:2<175 1996 181 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer