Influence of trees on above‐ground production dynamics of grasses in a humid savanna

Abstract

Abstract. Above‐ground grass biomass, necromass and tree litter were measured monthly over a vegetation cycle under tree clumps and in the open, in a humid savanna in Côte d'Ivoire. Grass production was calculated using several methods to better discriminate the contribution of the different grass compartments. Above‐ground grass biomass is higher in the open than under canopies during the second part of the growing season, but there is no difference in grass necromass dynamics. Physical protection of grass necromass by tree litter against decaying under tree canopies was assumed to explain this discrepancy. Grass production, calculated as the sum of positive increments of biomass and necromass, equals 1073 g m‐2 yr‐1 in the open, against 74 % underneath trees. However, basal ground cover is only 50 % of that in the open. Comparison with other savanna studies as a whole does not show any significant effect of rainfall on the relationship between under‐canopy and outside‐canopy grass production. However, in arid conditions, grass production tends to increase under light‐canopied trees (mostly Acacia legumes) which hardly affect grass photosynthesis, but add high quality litter to the soil surface.

Influencia de microhábitats en el desempeño de especies herbáceas en áreas de bosque maduro y secundario en la región semiárida de Brasil

“…This result agrees with other studies in semiarid environments which record that there is a higher density of the herbaceous component in open segments, where sunlight directly reaches the herbaceous stratum, facilitating recruitment (Crozier, & Boerner, 1984;Kessler, 1992;Belsky, 1994;Aguilera, & Lauenroth, 1995;Mordelet, & Menaut, 1995;Silva et al, 2008;Flores-Torres, & Montaña, 2012).…”

“…The first model includes the herbaceous species that develop in more shaded locations, below the crown of woody plants; these are capable of inducing morphological changes in herbaceous species, so that they can increase the biomass produced (Kessler, 1992;Mordelet, & Menaut, 1995;Zhang, Wang, Liu, & Li, 2006;Legras et al, 2010). The second model encompasses the herbaceous species that thrive best in open areas (Crozier, & Boerner, 1984;Kessler, 1992;Belsky, 1994;Mordelet, & Menaut, 1995;Aguilera, & Lauenroth 1995;Silva et al, 2008). In this study, differences in the mean heights of plants between microhabitats confirmed the influence of establishment conditions on plant growth, showing that direct light is an important prerequisite for the development of the studied species.…”

Differential responses of shrubs and herbs present at the Upper Minjiang River basin (Tibetan Plateau) to several soil variables

“…light) when sheltered by shrubs in a shrub-dominant community. It is well known that shade has a significant influence on herbaceous growth, and woody plants may influence the environments under their canopies, changing SM and nutrients, light availability, and temperature (Belsky, 1994;Mordelet and Menaut, 1995;Scholes and Archer, 1997). Some studies have shown that understory sites have higher SM than open grassland sites (Joffre and Rambal, 1993;Scholes and Archer, 1997).…”

Root foraging strategies and soil patchiness in a humid savanna

“…The selected tree clumps were made of three species, Bridelia ferruginea Benth., Crossopteryx febrifuga (Afzel. ex G. Don) Benth., Cussonia barteri Seeman and without any B. aethiopum (Mordelet and Menaut, 1995).…”