@article {KNZ001548, title = {Variation in root system traits among African semi-arid savanna grasses: implications for drought tolerance}, journal = {Austral Ecology}, volume = {38}, year = {2013}, pages = {383 -392}, abstract = {

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.

}, keywords = {LTER-KNZ, grass, mycorrhiza, rhizosheath, root architecture, savanna}, doi = {10.1111/j.1442-9993.2012.02422.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1442-9993.2012.02422.x}, author = {D.C. Hartnett and Ott, J.P. and G.T. Wilson and Setshogo, M.} } @article {KNZ001550, title = {Interspecific variation in bud banks and flowering effort among semi-arid African savanna grasses}, journal = {South African Journal of Botany}, volume = {83}, year = {2012}, pages = {127 -133}, abstract = {

Population 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.

}, keywords = {LTER-KNZ, Bud bank, Meristem, Poaceae, Reproductive allocation, Vegetative reproduction}, doi = {10.1016/j.sajb.2012.08.010}, url = {https://www.sciencedirect.com/science/article/pii/S0254629912001275?via\%3Dihub}, author = {Dalgleish, H.J. and Ott, J.P. and Setshogo, M. and Muzilla, M. and D.C. Hartnett} }