Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alteration

In this paper, a general method for an a posteriori plant functional type (PFT) analysis of global change effects on community composition is developed. We apply the method to a case study, specifically the Giessen-FACE experiment. This experiment involves a Central European meadow that has been ex...

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Main Authors: U. Grüters, S. Janze, C. Kammann, H.-J. Jäger
Format: Article
Language:English
Published: Julius Kühn-Institut 2012-12-01
Series:Journal of Applied Botany and Food Quality
Online Access:https://ojs.openagrar.de/index.php/JABFQ/article/view/2170
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spelling doaj-05d7d9dfc2f64224a2023a31e79bda1f2021-03-02T03:54:09ZengJulius Kühn-InstitutJournal of Applied Botany and Food Quality1613-92161439-040X2012-12-01802Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alterationU. GrütersS. JanzeC. KammannH.-J. Jäger In this paper, a general method for an a posteriori plant functional type (PFT) analysis of global change effects on community composition is developed. We apply the method to a case study, specifically the Giessen-FACE experiment. This experiment involves a Central European meadow that has been exposed to moderate CO2-enrichment since May 1998. The method for an a posteriori PFT-analysis: The method consists of four working steps and uses a combination of standard gradient analysis and Random Forests (RF). (1) The trait composition of the species is studied using Principal Components Analysis. Species trait information is gathered from databases. Natural PFT, i.e. groups of species with similar trait-sets, are identified specifically for the community under study. (2) A ranking of the species according to standardized/absolute CO2 abundance response is obtained from Redundancy Analysis. Initially, species with a response above or below the median are grouped into three response groups (RG) each having similar behaviour, i.e. positive/negative or no-response. (3) The outlyingness measure of RF is used to shift RG boundaries until satisfactory RG homogeneity is achieved. RF is utilized to find the best traits for the RG classification. The behaviour of species representative of the RG is derived from RF class centers. (4) From knowledge gained in steps 1-3, hypotheses about the causes underlying the community alteration are built. Strengths/weaknesses of the method are discussed. Application of the method to the case study: The community consists of three natural PFT. Five species are summer-green forbs of varying competitiveness. Four species are evergreen ruderal forbs characterized as (semi-) basal rosette plants. The third natural PFT contains evergreen, more or less competitive species, mostly grasses, but also a few forbs. Negative standardized CO2-response was practically restricted to two natural PFT, i.e. the summer-greens, irrespective of their competitiveness, and the evergreen ruderals. Standard positive response covered part of the evergreen competitive natural PFT. Among them was Glechoma hederacea, one of the forbs with the greatest similarity to grasses. Two hypotheses were formulated to explain the response pattern: (1) Summer-greens lost in competition with evergreens, because the annual time-integral they can use for enhanced growth was more limited with year-round CO2-enrichment. (2) As rosette plants, ruderal evergreens lagged behind evergreen competitors because periods with full sunlight, which enabled them to gain additional carbon, were shorter for them. Absolute responses were additionally dependent on dominance patterns. The most striking difference to standard responses was the restriction of positive response to (sub-)dominant grasses. https://ojs.openagrar.de/index.php/JABFQ/article/view/2170
collection DOAJ
language English
format Article
sources DOAJ
author U. Grüters
S. Janze
C. Kammann
H.-J. Jäger
spellingShingle U. Grüters
S. Janze
C. Kammann
H.-J. Jäger
Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alteration
Journal of Applied Botany and Food Quality
author_facet U. Grüters
S. Janze
C. Kammann
H.-J. Jäger
author_sort U. Grüters
title Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alteration
title_short Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alteration
title_full Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alteration
title_fullStr Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alteration
title_full_unstemmed Plant functional types and elevated CO<sub>2</sub>: A method of scanning for causes of community alteration
title_sort plant functional types and elevated co<sub>2</sub>: a method of scanning for causes of community alteration
publisher Julius Kühn-Institut
series Journal of Applied Botany and Food Quality
issn 1613-9216
1439-040X
publishDate 2012-12-01
description In this paper, a general method for an a posteriori plant functional type (PFT) analysis of global change effects on community composition is developed. We apply the method to a case study, specifically the Giessen-FACE experiment. This experiment involves a Central European meadow that has been exposed to moderate CO2-enrichment since May 1998. The method for an a posteriori PFT-analysis: The method consists of four working steps and uses a combination of standard gradient analysis and Random Forests (RF). (1) The trait composition of the species is studied using Principal Components Analysis. Species trait information is gathered from databases. Natural PFT, i.e. groups of species with similar trait-sets, are identified specifically for the community under study. (2) A ranking of the species according to standardized/absolute CO2 abundance response is obtained from Redundancy Analysis. Initially, species with a response above or below the median are grouped into three response groups (RG) each having similar behaviour, i.e. positive/negative or no-response. (3) The outlyingness measure of RF is used to shift RG boundaries until satisfactory RG homogeneity is achieved. RF is utilized to find the best traits for the RG classification. The behaviour of species representative of the RG is derived from RF class centers. (4) From knowledge gained in steps 1-3, hypotheses about the causes underlying the community alteration are built. Strengths/weaknesses of the method are discussed. Application of the method to the case study: The community consists of three natural PFT. Five species are summer-green forbs of varying competitiveness. Four species are evergreen ruderal forbs characterized as (semi-) basal rosette plants. The third natural PFT contains evergreen, more or less competitive species, mostly grasses, but also a few forbs. Negative standardized CO2-response was practically restricted to two natural PFT, i.e. the summer-greens, irrespective of their competitiveness, and the evergreen ruderals. Standard positive response covered part of the evergreen competitive natural PFT. Among them was Glechoma hederacea, one of the forbs with the greatest similarity to grasses. Two hypotheses were formulated to explain the response pattern: (1) Summer-greens lost in competition with evergreens, because the annual time-integral they can use for enhanced growth was more limited with year-round CO2-enrichment. (2) As rosette plants, ruderal evergreens lagged behind evergreen competitors because periods with full sunlight, which enabled them to gain additional carbon, were shorter for them. Absolute responses were additionally dependent on dominance patterns. The most striking difference to standard responses was the restriction of positive response to (sub-)dominant grasses.
url https://ojs.openagrar.de/index.php/JABFQ/article/view/2170
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