Response of three floodplain tree species to spatial heterogeneity in soil oxygen and nutrients

Abstract

Summary1. Plant responses to nutrient heterogeneity may be influenced by spatial heterogeneity in other soil-based resources. We investigated how heterogeneity in two resources, nutrients and oxygen, affected root system morphology and biomass of three floodplain tree species, which differ in waterlogging tolerance from highly tolerant ( Nyssa aquatica L.) to intermediate ( Fraxinus pennsylvanica Marsh.) to less tolerant ( Liquidambar styraciflua L.). 2. We predicted that heterogeneity in soil oxygen would affect the well-known root proliferation response to nutrient-rich patches, and biomass, of the least tolerant species, L. styraciflua , but would not influence biomass or proliferation of the more tolerant species, F. pennsylvanica and N . aquatica . To test this prediction, we grew seedlings in pots where we manipulated the spatial distribution of oxygen (via waterlogging) and nutrients. 3. All species were precise foragers (i.e. they displayed preferential proliferation of roots in nutrient-rich patches) in uniformly drained and waterlogged conditions. When waterlogging and nutrients were both heterogeneous, roots of L. styraciflua avoided waterlogged patches and did not precisely forage for nutrients. In contrast, waterlogging had no negative effects on nutrient foraging of either F. pennsylvanica or N. aquatica ; however, these species did not precisely forage for nutrients when nutrient-rich and waterlogged patches were spatially separate. 4. Waterlogging reduced biomass of L. styraciflua , did not significantly affect biomass of F. pennsylvanica , and enhanced biomass of N. aquatica . In pots where waterlogging and nutrients were simultaneously heterogeneous, the spatial position of waterlogging relative to that of nutrients influenced the biomass response of F. pennsylvanica and N. aquatica to nutrient heterogeneity, but did not influence L. styraciflua . For F. pennsylvanica and N. aquatica , nutrients may have been easier to acquire in waterlogged patches due to faster diffusion rates. 5. Synthesis . Our results suggest that root system and biomass responses to nutrient heterogeneity can be affected by heterogeneity in another soil-based resource (i.e. soil oxygen availability). We believe ecologists should consider the effects of spatial heterogeneity in other soil-based resources when attempting to link nutrient heterogeneity to plant population or community attributes.

Alterations in flood frequency increase exotic and native species richness of understorey vegetation in a temperate floodplain eucalypt forest

“…Floodplain forests are subject to localised heterogeneity in both soil oxygen and nutrients, due to periodic saturation and development of anoxic conditions during the growing season (Neatrour et al 2007). Whilst both soil oxygen and nutrient content of the soil are linked to the flood cycle, the increase in exotic species could impact upon these resources due to alterations in leaf litter decomposition processes between exotic versus native species (Schulze and Walker 1997;Shah and Dahm 2008).…”

Reciprocal and coincident patchiness of multiple resources differentially affect benefits of clonal integration in two perennial plants

“…Although this result appears not to have been previously reported for ramets within clones (Zhang & He 2009), it parallels at least one report for branches within non‐clonal plants. Neartour, Jones & Golladay (2007) grew individuals of each of three non‐clonal species in bisected pots and subjected their root systems to reciprocal and coincident patchiness of nutrients and oxygen, the latter manipulated with waterlogging. The species least tolerant of flooding was the only one less able to concentrate roots in the high‐nutrient soil when patchiness was reciprocal, showing both a differential response to reciprocal and coincident patchiness and a link between this response and ecological range in the species.…”

“…Blair & Perfecto 2004). This is probably due at least in part to the ability of many plants to locate modules such as root branches where resource availability is relatively high and to higher efficiency or rate of uptake by modules where availability is higher, and it depends upon the ability to redistribute resources between modules within the plant (Hodge 2004; Jansen, Van De Steeg & De Kroon 2005; Neartour, Jones & Golladay 2007).…”

Root growth and plant biomass in Lolium perenne exploring a nutrient-rich patch in soil

“…Deeper root elongation may also benefit plants by reaching deeper moisture and the nutrients within it. This possibility suggests the need to examine the interactions between patchy distribution of soil nutrients and other factors such as water availability (e.g., Neatrour et al 2007). …”