02725nas a2200217 4500008004100000245011300041210006900154300001300223490000700236520204500243653001002288653001502298653001602313653002202329653001202351100001902363700001402382700001702396700001702413856007702430 2013 eng d00aVariation in root system traits among African semi-arid savanna grasses: implications for drought tolerance0 aVariation in root system traits among African semiarid savanna g a383 -3920 v383 a
In arid to semi-arid grasslands and savannas, plant growth, population dynamics, and productivity are consistently and strongly limited by soil water and nutrient availability. Adaptive traits of the root systems of grasses in these ecosystems are crucial to their ability to cope with strong water and/or nutrient limitation and the increasing drought stress associated with ecosystem degradation or projected climate change. We studied 18 grass species in semi-arid savanna of the Kalahari region of Botswana to quantify interspecific variation in three important root system traits including root system architecture, rhizosheath thickness and mycorrhizal colonization. Drought-tolerant species and shorter-lived species showed greater rhizosheath thickness and fine root development but lower mycorrhizal colonization compared to later successional climax grasses and those characteristic of wetter sites. In addition, there was a significant positive correlation between root fibrousness index and rhizosheath thickness among species and a weak negative correlation between root fibrousness index and mycorrhizal colonization. These patterns suggest that an extensive fine root system and rhizosheath development may be important complementary traits of grasses coping with drought conditions, the former aiding in the acquisition of water by the grass plant and the latter aiding in water uptake and retention, and reducing water loss in the rhizosphere. Within species, both rhizosheath development and mycorrhizal colonization were significantly greater in a wet year than in a year with below-average precipitation. The observed patterns suggest that the primary benefit of rhizosheath development in African savanna grasses is improved drought tolerance and that it is a plastic trait that can be adjusted annually to changing environmental conditions. The functioning of mycorrhizal symbiosis is likely to be relatively more important in infertile savannas where nutrient limitation is higher relative to water limitation.
10agrass10amycorrhiza10arhizosheath10aroot architecture10asavanna1 aHartnett, D.C.1 aOtt, J.P.1 aWilson, G.T.1 aSetshogo, M. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1442-9993.2012.02422.x02491nas a2200229 4500008004100000245010200041210006900143300001300212490000700225520176600232653001301998653001302011653001202024653002802036653002802064100002002092700001402112700001702126700001602143700001902159856008302178 2012 eng d00aInterspecific variation in bud banks and flowering effort among semi-arid African savanna grasses0 aInterspecific variation in bud banks and flowering effort among a127 -1330 v833 aPopulation viability and productivity of grasses in southern African savannas are dependent upon both successful seed production and tiller recruitment from the belowground bud bank. Relative recruitment rates from buds versus seeds influence population dynamics, genetic diversity, and patterns of vegetation productivity. We assessed patterns in bud bank size and flowering effort in fourteen semi-arid savanna grass species in the Kalahari region of Botswana. There was high inter-specific variability and between-year variability in flowering effort (percentage of tillers flowering). Bud production (number of buds per tiller) exhibited high inter-specific variability, but was more consistent between-years than flowering effort. Relative allocation to flowering versus bud production varied with life history, with longer-lived perennial grasses showing higher bud production and lower flowering effort relative to shorter-lived grasses. Several species showed higher bud production and lower flowering effort in a wet year compared to a dry year, and grass species that are regularly grazed maintained significantly larger bud banks than non-grazed species. These differential demographic responses among co-occurring species suggest that environmental change in semi-arid savannas may alter the composition, relative abundances and diversity of grasses, and that the maintenance of a belowground bud bank is an important factor influencing their resiliency, their capacity to recover from grazing and/or drought, and their persistence and sustainability under changing environmental conditions. Meristem-limitation in species that maintain few viable buds may constrain their population viability under changing conditions in semi-arid savannas.
10aBud bank10aMeristem10aPoaceae10aReproductive allocation10aVegetative reproduction1 aDalgleish, H.J.1 aOtt, J.P.1 aSetshogo, M.1 aMuzilla, M.1 aHartnett, D.C. uhttps://www.sciencedirect.com/science/article/pii/S0254629912001275?via%3Dihub