The Effect of Nitrogen and Glyphosate on Survival and Colonisation of Perennial Grass Species in an Agro-Ecosystem: Does the Relative Importance of Survival Decrease with Competitive Ability?

Abstract

The ecological success of a plant species is typically described by the observed change in plant abundance or cover, but in order to more fully understand the fundamental plant ecological processes, it is necessary to inspect the underlying processes of survival and colonization and how they are affected by environmental conditions. A general ecological hypothesis on the effect of environmental gradients on demographic parameters is proposed and tested. The hypothesis is that decreasing fitness or competitive ability along an environmental gradient is associated with an increasing importance of survival for regulating the abundance of the species. The tested hypothesis is related to both the stress gradient hypothesis and whether the importance of competition increases along productivity gradients. The combined effect of nitrogen and glyphosate on the survival and colonization probability of two perennial grass species, Festuca ovina and Agrostis capillaris, which are known to differ in their responses to both glyphosate and nitrogen treatments, is calculated using pin-point cover data in permanent frames. We found that the relative importance of survival increased with the level of glyphosate for the glyphosate sensitive A. capillaris and decreased for the glyphosate tolerant F. ovina. Likewise, increasing levels of nitrogen increased the importance of survival for the relative nitrophobic F. ovina. Consequently, the proposed hypothesis was corroborated in this specific study. The proposed method will enable predictions of the effects of agricultural practices on community dynamics in a relatively simple setup eliminating the need to quantify all the interaction among the species in the plant community. The method will be immediately useful for the regulation of non-cultivated buffer strips between agricultural fields and semi-natural and natural biotopes such as hedgerows and waterways.

Effect of Nutrient and Spacing on Growth and Biomass Production in Poplar under Nursery Condition

“…. Similarly, Damagaard et al [12] also reported that increasing levels of fertilizer enhanced the sprouting of cutting in Fesuca ovina.…”

Empirical modelling of trait selection by partitioning selection into direct selection and selection that is mediated by interspecific interactions

“…Furthermore, if plant abundance of perennial plants is measured several times during 210 a growth season, e.g. in spring and autumn (Damgaard, 2011;Damgaard et al, 2013;Damgaard et al, in 211 press), then the trait selection processes during summer growth may be estimated independently from the 212 trait selection processes during over-wintering and, consequently, allows the generation and testing of 213 temporal coexistence mechanisms (storage effects, Chesson, 2000). 214…”