Patterns in leaf traits of leguminous and non-leguminous dominant trees along a rainfall gradient in Ghana

Aims Both dominance distribution of species and the composition of the dominant species determine the distribution of traits within community.Leaf carbon(C)and nitrogen(N)isotopic composition are important leaf traits,and such traits of dominant species are associated with ecosystem C,water and N cycling.Very little is known how dominant species with distinct traits(e.g.N-fixing leguminous and non-leguminous trees)mediate resource utilization of the ecosystems in stressful environment.Methods Leaves of 81 dominant leguminous and non-leguminous trees were collected in forest(moist semi-deciduous and dry semi-deciduous ecosystems)and savanna(costal savanna,Guinean savanna and west Sudanian savanna ecosystems)areas and the transitional zone(between the forest and the savanna)along the transect from the south to the north of Ghana.We measured leaf traits,i.e.leafδ13C,leafδ15N,leaf water content,leaf mass per area(LMA)and C and N concentration.Correlation analyses were used to examine trait–trait relationships,and relationships of leaf traits with temperature and precipitation.We used analysis of covariance to test the differences in slopes of the linear regressions between legumes and non-legumes.Important Findings Leafδ13C,δ15N,leaf water content and LMA did not differ between leguminous and non-leguminous trees.Leaf N concentration and C:N ratio differed between the two groups.Moreover,leaf traits varied significantly among the six ecosystems.δ13C values were negatively correlated with annual precipitation and positively correlated with mean annual temperature.In contrast,leafδ15N of non-leguminous trees were positively correlated with annual precipitation and negatively correlated with mean annual temperature.For leguminous trees,such correlations were not significant.We also found significant coordination between leaf traits.However,the slopes of the linear relationships were significantly different between leguminous and non-leguminous trees.Our results indicate that shifts in dominant trees with distinct water-use efficiency were corresponded to the rainfall gradient.Moreover,leguminous trees,those characterized with relative high water-use efficiency in the low rainfall ecosystems,were also corresponded to the relative high N use efficiency.The high proportion of leguminous trees in the savannas is crucial to mitigate nutrient stress.

The contribution of microorganisms and metazoans to mineral nutrition in bromeliads

Aims One critical challenge for plants is to maintain an adequate nutrient supply under fluctuating environmental conditions.This is particularly true for epiphytic species that have limited or no access to the pedosphere and often live in harsh climates.Bromeliads have evolved key innovations such as epiphytism,water-absorbing leaf trichomes,tank habit and Crassulacean acid metabolism(CAM)photosynthesis that enable them to survive under various environmental conditions.Bromeliads encompass diverse ecological types that live on different substrates(they can be terrestrial,epilithic or epiphytic)and vary in their ability to retain water(they can be tank-forming or tankless)and photosynthetic pathway(i.e.C3 or CAM).In this review,we outline the nutritional modes and specializations that enable bromeliads to thrive in a wide range of nutrient-poor(mostly nitrogen-depleted)environments.Important FindingsBromeliads have evolved a great diversity of morphologies and functional adaptations leading to the existence of numerous nutritional modes.Focusing on species that have absorptive foliar trichomes,we review evidence that bromeliads have evolved multi-faceted nutritional strategies to respond to fluctuations in the supply of natural nitrogen(N).These plants have developed mutualistic associations with many different and functionally diverse terrestrial and aquatic microorganisms and metazoans that contribute substantially to their mineral nutrition and,thus,their fitness and survival.Bacterial and fungal microbiota-assisted N provisioning,protocarnivory,digestive mutualisms and myrmecotrophic pathways are the main strategies used by bromeliads to acquire nitrogen.The combination of different nutritional pathways in bromeliads represents an important adaptation enabling them to exploit nutrient-poor habitats.Nonetheless,as has been shown for several other vascular plants,multiple partners are involved in nutrient acquisition indicating that there have been convergent adaptations to nutrient scarcity.Finally,we point out some gaps in the current knowledge of bromeliad nutrition that offer fascinating research opportunities.