The research presented in this thesis is part of an interdisciplinary project funded by the Ger-man Research Foundation ‘Adaptation of Forest Trees to Climatic Change - Diversity of Drought Responses in Douglas-Fir Provenances (Pseudotsuga menziesii (Mirb.) Franco)’.
The aim of the joint research program is to study the drought response diversity of various Douglas-fir provenances from the molecular to the organism level, and to link phenotypic and physiological variation (as expressed in e.g. growth responses and isotope composition) with allelic variation in candidate genes. Furthermore, metabolite profiles as physiological markers were performed with external funds and linked to the results of the joint project. The focus of this thesis lies on linking the information derived from leaf gas exchange (assessed by leaf isotopic analyses and gas exchange measurements) to metabolic changes that interact with leaf gas exchange (for instance osmotic adjustment) as well as to concomitant changes in growth patterns under heat and drought stress.
The thesis consists of field experiments (chapters 2 and 3) and experiments under controlled conditions (chapter 4). In joint field campaigns, the interdisciplinary project offered the unique opportunity to study 50 year old Douglas-fir trees (ca. 25 - 35 m tall) in a provenance trial (Table 1) monitored by the Forest Research Institute Baden-Württemberg (Freiburg, Germany) since they were established (Kenk & Thren, 1984).
Table 1 Location and climatic conditions at the field sites of the provenance trial (Kenk & Ehring 2004) Field Site Region Altitude (m asl) MAT (°C) MAP (mm) See field experiment in chapter
Dgl 122 Wiesloch Rhine valley 105 9.9 660 2
Dgl 115 Mooswald Rhine valley 228 10.0 830 3
Dgl 114 Illenberg Black Forest 500 8.0 903 3
Dgl 116 Schauinsland Black Forest 940 6.0 1791 3
Dgl 123 Schluchsee Black Forest 1050 6.1 1345 2
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Table 2 Geographic location and climatic conditions in the regions of origin of the provenances studied in the field experiments (chapter 2 & 3) and experiments under controlled conditions (chapter 4)
Longitude and latitude are given in decimal format. Mean annual temperature (MAT), mean annual precipitation (MAP), mean summer temperature (May-Sep, MST), mean summer (May to Sept.) precipitation (MSP), annual heat:moisture index (AHM=(MAT+10)/(MAP/1000)), summer heat:moisture index (SHM=mean warmest month temperature/(MSP/1000)), Hargreaves climatic moisture deficit (CMD) were modelled based on ClimateWNA v4.72 (© University of British Columbia, Wang et al., 2012). Elevation according to Kenk & Ehring (2004) or ac-cording to information given by the seedling supplier (Monte Creek and Pend Oreille). Physiographic regions in USA according to Franklin & Dyrness (1973)
Provenance name
We studied provenances from British Columbia, Washington and Oregon including the coastal and interior variety of Douglas-Fir, originating from environments differing strongly in temperature (Table 2), precipitation amount (Figure 3) and, consequently, climatic moisture deficit (CMD, Table 3).
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Figure 3 Monthly precipitation in the regions of origin of the provenances studied in the field experiments and in the experiments under controlled conditions
Precipitation was modelled with ClimateWNA v4.72 (© University of British Columbia, Wang et al., 2012)
Table 3 Monthly Hargreaves climatic moisture deficit (CMD) in the regions of origin of the provenances studied in the field experiments and experiments under controlled conditions
CMD was modelled with ClimateWNA (© University of British Columbia) v4.72 (Wang et al., 2012)
Provenance name CMD
Jan CMD Feb CMD
Mar CMD Apr CMD
May CMD Jun CMD
Jul CMD Aug CMD
Sep CMD Oct CMD
Nov CMD Dec
Salmon Arm (31/102) 0 0 11 42 66 81 106 82 33 5 0 0
Monte Creek 0 0 17 43 68 84 101 81 31 8 0 0
Cameron Lake 0 0 0 0 8 43 75 41 0 0 0 0
Duncan Paldi 0 0 0 0 40 66 92 72 22 0 0 0
Conrad Creek(Darrington 3) 0 0 0 0 5 33 93 53 0 0 0 0
Pend Oreille 0 0 1 21 45 72 120 95 41 3 0 0
Timber 0 0 0 0 34 66 112 91 12 0 0 0
Santiam River 0 0 0 0 7 68 130 108 33 0 0 0
Pamelia Creek 0 0 0 0 0 25 99 61 0 0 0 0
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The main part of this thesis includes three studies on growth, physiological and metabolic responses towards environmental conditions (chapter 2, 3, and 4). The appendix includes two studies from the joint project that are closely interlinked with the aforementioned studies (Du et al., 2014; Junker et al., 2017).
For studies on the response of Douglas fir to environmental drivers during two growing sea-sons, we selected two sites from the provenance trial representing the end members of an alti-tudinal transect and thus showing contrasting temperature and precipitation regimes (Dgl 122 Wiesloch, 105 m asl in the Rhine valley and Dgl 123 Schluchsee, 1050 m asl in the Black-Forest, see Table 1), and 4 provenances originating from climatically contrasting environ-ments (see Table 2). Joint field campaigns conducted in the growing seasons 2010 and 2011 led to two studies presented in chapter 2 and in the appendix, (Junker et al., 2017).
For retrospective analyses of the response of Douglas fir to environmental drivers, including the hot and dry year 2003, we studied 6 provenances (Table 2) along an altitudinal transect at three sites close to Freiburg (230, 500 and 940 m asl, Table 1). The results are shown in chap-ter 3 (Jansen et al., 2013).
In an experiment under controlled conditions, we exposed 3- and 4-year old Douglas-fir seed-lings of two provenances (Table 2) to elevated temperature and atmospheric drought and as-sessed the physiological and metabolic responses to understand the mechanisms of drought resistance and susceptibility. This experiment lead to two studies, presented in chapter 4 (Jansen et al., 2014) and in the appendix (Du et al., 2014).
In order to identify productive as well as heat and drought-tolerant Douglas-fir provenances, the studies included in this thesis aim at detecting physiological and metabolic markers for drought and heat sensitivity or resistance of provenances and linking the physiological varia-tion to phenotypic (i.e. growth) variavaria-tion. Stable isotope techniques and leaf gas exchange were applied to characterise intrinsic water-use efficiency and stomatal reactions. Changes in the metabolite profiles were analysed to detect marker metabolites for heat stress responses and to identify changes in metabolic pathways in reaction to heat. Leaf levels of organic os-molytes and inorganic ions were studied to reveal information on osmotic adjustment in re-sponse to heat and drought. These results are complemented by the study on photoprotective mechanisms (see appendix).
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On different time-integrating scales and under field and controlled conditions, these studies overall intend to answer the following research questions:
Do Douglas-fir provenances differ in physiological, metabolic and growth parameters under humid as well as hot and dry conditions?
Can we derive information on heat and drought sensitivity and resistance regarding short-term and long-term responses?
Can we elucidate stress response mechanisms linking physiological and morphological pa-rameters such as stomatal control (chapter 2 & 3), growth responses (chapter 3), osmotic ad-justment (chapter 2 & 4), changes in metabolic pathways (chapter 4 & appendix) or photopro-tective mechanisms (appendix)?
Do the environmental conditions at the site of origin play a role in this response and if so, what are specific results for provenances originating from warm and dry areas versus humid areas?
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