Plant communities in field margins of agricultural landscapes: species distributions, functional traits, and contributions to landscape function

Most of the agricultural landscapes are a mosaic of cultivated fields, semi-natural habitats, human infrastructures and occasional natural habitats. Within such landscapes, linear semi-natural habitats often define the edges of agricultural fields, called “field margins”. Field margins are an important component of the agricultural landscapes as they are contributing positively to ecosystem functions by supporting biodiversity, preventing soil erosion, contributing in nutrient cycling and improving soil stability. This thesis is aiming to further our understanding of the processes governing plant community structure and resulting functioning in agricultural field margins by focusing on describing naturally occurring plant communities of the field margins in the agricultural landscape of Haean-myun catchment in South Korea and how it can affect the ecosystem functioning (e.g. soil stability, soil erosion control), which consequently will help us to understand the functional role of the field margins as an important component of the agro-ecosystem. Our first study investigates how the local-scale management and the landscape-scale land-use influence the composition of plant communities of agricultural field margins, to understand how to improve the diversity of the field margins in agricultural landscapes. In the second study, we aimed to integrate vegetation characteristics and plant functional traits (PFTs) into a statistical model of abiotic soil characteristic effects on soil stability, towards an improved understanding of ecosystem functioning in agricultural landscapes. Finally, in the third study, we investigated how field margins in the agriculture landscapes can limit the soil erosion during the monsoon season, which will help us to better understand the function of an important ecosystem component like field margins within the agriculture landscapes, via testing the effect of its different management schemes at different slope degrees on sediment trapping. To test how the local management “managed and unmanaged” and the landscape-scale land-use “percentage of non-farmed habitat” influence plant communities of agricultural field margins, we studied multi-facet plant community structure which includes alpha, beta and gamma diversities and species level characteristics such as rareness, growth forms, and dispersal types in hundred field margins in Haean-myun catchment, South Korea. We found that abandonment of local management in field margins positively influenced alpha diversity and especially the abundance of species that are rare and/or are characterized by abiotic dispersal and perennial growth forms. In contrast, local management of field margins resulted in lower alpha diversity and contributed to high beta diversity. The availability of landscape-scale non-farmed habitats influenced especially the diversity of managed field margins by increasing alpha diversity especially when focusing on more frequent species. The positive effect was highest for annual species independent of their dispersal mode. For our second study, we used path model analysis to quantify the effect of plant functional traits (PFTs), abiotic soil characteristics (soil texture) and vegetation characteristics (vegetation cover and species richness) on three soil stability measures (soil aggregate stability, soil penetration resistance and soil shear vane strength) in 30 field margins in Haean-myun catchment, South Korea, in these models we studied also the importance of intraspecific trait variability (ITV) by comparing models that account or ignore for ITV. We found that, variance in soil stability was explained to varying degrees (from 81% for soil aggregate stability to 35% for soil shear vane strength). The three soil stability measures were mainly affected directly by root density, while PFTs and soil texture exerted indirect effects through root density and vegetation parameters, respectively. Including ITV improved model explained variance and goodness-of-fit in all cases. In the third study on the effect of field margin’s management and slope degree on sediment trapping, prior to the beginning of monsoon season, a total of 12 sites within Haean-myun catchment, South Korea, were equipped with Astroturf mats (n = 15 / site) which were placed before, within and after four different types of field margins: “managed flat”, “managed steep”, “natural flat” and “natural steep. Sediment was collected from the 12 sites after each rain event continuously until the end of the monsoon season. Using the linear mixed effect model allowed us to test the effect of management and slope degree on sediment trapping for the sediment collected within the field margin and the sediment difference between these collected after and before the four field margins’ types. We found that in all cases, there is a positive relation between rainfall and sediment collected. Natural field margins showed high efficiency in reducing soil erosion in comparison to the managed ones. For the field margin slope, it showed effectiveness in combination with vegetation cover, as natural margins that have steep slopes had more sediment trapped in comparison to the managed margins. These findings allowed us to develop a functional framework of placement and designing of field margins within agriculture landscape to reduce soil erosion. In this thesis, we developed several recommendations for improving the ecosystem functions in agricultural landscapes using the field margins as a functional component of the agroecosystem. We showed how important the local-management of the field margins and the surrounding landscape-scale land-use in maintaining the diversity in the agricultural landscapes. For areas like South Korea, new laws and strategies should be developed to control the field margin’s local management, which will help in conserving the biodiversity by providing the suitable habitats for flora and fauna and consequently, will affect the soil quality and stability which will help in controlling the soil erosion happens during the monsoon time in South Korea. Furthermore, we demonstrated how essential is the field margin’s plant functional community composition on soil stability as an important ecosystem function in the agricultural landscapes. Finally, we modified a pre-existing future decision support system (DSS) framework for the effective design and placement of the vegetated field margins within the agricultural field system to help in protecting soil erosion via field margins in agricultural landscapes that face monsoonal climate.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bayreuth

Year

2015

Author dc:creator

• Elsayed Ali, Hamada

Contributors dc:contributor

• Reineking, Björn

Repository record source_url

https://epub.uni-bayreuth.de/id/eprint/2460/

OAI identifier oai:identifier

oai:epub.uni-bayreuth.de:2460