TY  - JOUR
A1  - Hoffmann, Mathias
A1  - Wirth, Stephan J.
A1  - Bessler, Holger
A1  - Engels, Christof
A1  - Jochheim, Hubert
A1  - Sommer, Michael
A1  - Augustin, Jürgen
T1  - Combining a root exclusion technique with continuous chamber and porous tube measurements for a pin-point separation of ecosystem respiration in croplands
JF  - Journal of plant nutrition and soil science = Zeitschrift für Pflanzenernährung und Bodenkunde
N2  - To better assess ecosystem C budgets of croplands and understand their potential response to climate and management changes, detailed information on the mechanisms and environmental controls driving the individual C flux components are needed. This accounts in particular for the ecosystem respiration (R-eco) and its components, the autotrophic (R-a) and heterotrophic respiration (R-h) which vary tremendously in time and space. This study presents a method to separate R-eco into R-a [as the sum of R-a (shoot) and R-a (root)] and R-h in order to detect temporal and small-scale spatial dynamics within their relative contribution to overall R-eco. Thus, predominant environmental drivers and underlying mechanisms can be revealed. R-eco was derived during nighttime by automatic chamber CO2 flux measurements on plant covered plots. R-h was derived from CO2 efflux measurements, which were performed in parallel to R-eco measurements on a fallow plot using CO2 sampling tubes in 10 cm soil depth. R-a (root) was calculated as the difference between sampling tube CO2 efflux measurements on a plant covered plot and R-h. R-a (shoot) was calculated as R-eco - R-a (root) - R-h. Measurements were carried out for winter wheat (Triticum aestivum L.) during the crop season 2015 at an experimental plot located in the hummocky ground moraine landscape of NE Germany. R-eco varied seasonally from < 1 to 9.5 g C m(-2) d(-1), and was higher in adult (a) and reproductive (r) than juvenile (j) stands (gC m(-2) d(-1): j = 1.2, a = 4.6, r = 5.3). Observed R-a and R-h were in general smaller compared to the independently measured R-eco, contributing in average 58% and 42% to R-eco. However, both varied strongly regarding their environmental drivers and particular contribution throughout the study period, following the seasonal development of soil temperature and moisture (R-h) as well as crop development (R-a). Thus, our results consistently revealed temporal dynamics regarding the relative contribution of R-a (root) and R-a (shoot) to R-a, as well as of R-a and R-h to R-eco. Based on the observed results, implications for partitioning of R-eco in croplands are given.
KW  - automatic chambers
KW  - autotrophic respiration
KW  - heterotrophic respiration
KW  - soil CO2 sampling tubes
Y1  - 2017
U6  - https://doi.org/10.1002/jpln.201600489
SN  - 1436-8730
SN  - 1522-2624
VL  - 181
IS  - 1
SP  - 41
EP  - 50
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Schmidt, Martin
A1  - Jochheim, Hubert
A1  - Kersebaum, Kurt-Christian
A1  - Lischeid, Gunnar
A1  - Nendel, Claas
T1  - Gradients of microclimate, carbon and nitrogen in transition zones of fragmented landscapes - a review
JF  - Agricultural and forest meteorology
N2  - Fragmentation of landscapes creates a transition zone in between natural habitats or different kinds of land use. In forested and agricultural landscapes with transition zones, microclimate and matter cycling are markedly altered. This probably accelerates and is intensified by global warming. However, there is no consensus on defining transition zones and quantifying relevant variables for microclimate and matter cycling across disciplines. This article is an attempt to a) revise definitions and offer a framework for quantitative ecologists, b) review the literature on microclimate and matter cycling in transition zones and c) summarise this information using meta-analysis to better understand bio-geochemical and bio-geophysical processes and their spatial extent in transition zones. We expect altered conditions in soils of transition zones to be 10-20 m with a maximum of 50 m, and 25-50 m for above-ground space with a maximum of 125 m.
KW  - Edge effects
KW  - Ecological boundaries
KW  - Matter cycling
KW  - Matter dynamics
KW  - Framework quantitative ecology
KW  - Ecotone hierarchy
Y1  - 2016
U6  - https://doi.org/10.1016/j.agrformet.2016.10.022
SN  - 0168-1923
SN  - 1873-2240
VL  - 232
SP  - 659
EP  - 671
PB  - Elsevier
CY  - Amsterdam
ER  -