- Titel
- Understanding Soil Hydraulic Properties in Temperate Climate Forests – A Case Study in Northeast Germany
- Zitierfähige Url:
- https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-970322
- Erstveröffentlichung
- 2025
- Datum der Einreichung
- 07.09.2024
- Datum der Verteidigung
- 31.01.2025
- Abstract (EN)
- Due to climate change, European forests face several challenges, including rising temperatures, decreased soil moisture, and increasingly frequent and intense extreme weather events. These factors threaten the health, functions, and the provision of essential ecosystem services of forests. As a response to these threats, forest management strategies are being adapted to enhance forest resilience and adaptability. However, the implications of these management practices on water resources and soil hydrology remain largely uncertain. Soil hydraulic properties (SHP), such as water retention capacity, soil hydraulic conductivity, and pore-size distribution play a relevant role in determining water availability for plant growth and ecosystem functioning. Based on two Journal papers, this dissertation investigated the variability of SHP in temperate climate forests to address these challenges. The aim was to identify key factors determining these variations, including tree species, soil texture, and tree age. The research encompassed three objectives: (1) to understand the general state of knowledge on SHP concerning forest type and site characteristics, (2) to provide empirical evidence on the variation of SHP, focusing on two relevant aspects: site conditions and forest stands, and (3) to raise awareness about the need to develop a robust scientific basis on the variation of the SHP in forest stands in temperate climates following standardised approaches. Three hypotheses and a research question guided this study: (H1) hydraulic conductivity will exhibit a gradient, with broad-leaved forests stands demonstrating the highest values, followed by mixed forests and then needle-leaved forests stands; (H2) water holding capacity in the soil will vary among broad-leaved, needle-leaved, and mixed forests; (H3) soil texture and tree age significantly influence SHP, with higher hydraulic conductivity associated with increased sand content and older tree stands; and (RQ) is the influence of forest stand type, considering two of the most used tree species in European forestry (Fagus sylvatica and Picea abies) larger than the influence of site-specific conditions? To address these, a comprehensive systematic literature review together with field measurements were conducted to assess the influence of forest stands and site-specific conditions on SHP. The literature review focused on synthesising the state of knowledge about SHP variability across various forest types within temperate climates. The analysis revealed a substantial knowledge gap regarding the influence of forest stands, soil texture, and stand age on SHP. In addition, studies were difficult to compare as analyses often included differing parameters. Given the observed ambiguity surrounding the characterisation of SHP, conducting experimental investigations are important to gain a clearer understanding of the behaviour of SHP. Therefore, the conducted measurements in this thesis provided insights into the variation of SHP following approaches often overlooked in existing literature. It focused on paired-sites of forest stands of Picea abies and Fagus sylvatica of a comparable stand age (90-120 years old) in the Tharandt Forest, Saxony, NE Germany. Moreover, to include the effect of site-specific conditions on SHP, paired-sites were selected in several locations with differing soil textures. This study employed a combination of field and laboratory experiments to characterise SHP, including hydraulic conductivity, water retention capacity of the soil, and pore-size distribution. Results showed compelling evidence that both tree type and site conditions play an important role in the characterisation of SHP. Beech stands exhibited distinct SHP characteristics compared to spruce forests of comparable characteristics, highlighting the influence of stand type. Additionally, soil texture emerged as a crucial factor influencing SHP variations, with sand content demonstrating a particular relationship with the soil hydraulic conductivity. To address the existing knowledge gap, a standardised methodology for SHP research is proposed. Also advocated the importance of reporting essential parameters such as stand type, soil texture, tree age, and measurement devices. By adhering to this standardised approach and consistently including these parameters, researchers can enhance data comparability across studies. The implementation of such standardised methodologies will contribute to the creation of a robust and unified SHP database for temperate forests. This study contributes to a deeper understanding of soil water dynamics in forests of temperate climates by identifying key factors influencing SHP variability. While providing insights into the characterisation of SHP, it highlights the need for standardised methodologies to ensure data comparability and reliability. Moreover, validating these methodologies across diverse soil and environmental conditions is crucial to strengthen the applicability of these findings. Furthermore, increasing investigations incorporating a wider range of parameters are necessary (e.g., forest stand types and soil texture). Ultimately, this research represents a step forward in bridging the gap between scientific knowledge and practical applications, to improve soil hydrology quantification in temperate zone forests, supporting accurate forest management. This information will serve as a valuable resource for researchers, forest managers, and policymakers, enabling the development of effective strategies for forest management and conservation under a changing climate.
- Freie Schlagwörter (EN)
- Fagus sylvatica, hydraulic conductivity, Picea abies, pore-size distribution, water retention capacity
- Klassifikation (DDC)
- 634
- Klassifikation (RVK)
- ZC 72400
- GutachterIn
- Prof. Dr. Karl-Heinz Feger
- Prof. Dr. Martin Freudiger
- Prof. Dr. Winfried Riek
- BetreuerIn Hochschule / Universität
- Prof. Dr. Karl-Heinz Feger
- BetreuerIn - externe Einrichtung
- Prof. Dr. Stefan Jülich
- Den akademischen Grad verleihende / prüfende Institution
- Technische Universität Dresden, Tharandt, Deutschland
- Version / Begutachtungsstatus
- publizierte Version / Verlagsversion
- URN Qucosa
- urn:nbn:de:bsz:14-qucosa2-970322
- Veröffentlichungsdatum Qucosa
- 21.05.2025
- Dokumenttyp
- Dissertation
- Sprache des Dokumentes
- Englisch
- Lizenz / Rechtehinweis
CC BY-NC-SA 4.0- Inhaltsverzeichnis
Declaration of conformity i Note on the commencement of the doctoral procedure ii Abstract iii Zusammenfassung v Table of Contents viii List of Figures x List of Tables xii Acronyms and Abbreviations xiii Symbols xiv Chapter 1 Introduction 1 1.1 Background and Problem Statement 1 1.1.1 Climate change, forests ecosystems, and their vulnerability 1 1.1.2 European forests, composition, and changes in the structure 2 1.1.3 Soil hydraulic properties and their relevance in forest soils 4 1.2 Methodologies and SHP Calculation 7 1.2.1 Saturated and near-saturated hydraulic conductivity field measurements 7 1.2.2 Pore-size Distribution of the soil (PSD) from the water retention functions 9 1.3 Problem Statement and Objectives 10 1.4 Hypotheses, Research Question, and Approach of the Thesis 11 1.5 Research Papers of the Thesis 14 Chapter 2 Review of Literature (Paper 1) 15 2.1 Introduction 16 2.2 Materials and Methods 17 2.2.1 Nature and classification of studies 17 2.2.2 Statistical analyses 19 2.3 Results 19 2.3.1 Soil water retention 20 2.3.2 Soil bulk density 20 2.3.3 Soil saturated hydraulic conductivity 23 2.4 Discussions 26 2.5 Conclusions 28 2.6 Chapter references 29 Chapter 3 Case Study (Paper 2) 34 3.1 Introduction 35 3.2 Materials and Methods 36 3.2.1 Study site 36 3.2.2 Infiltration experiments 37 3.2.3 Sampling 37 3.2.4 Analysis of water retention and conductivity characteristics 37 3.2.5 Soil texture, pH, C, and N 38 3.2.6 Statistical analyses 38 3.3 Results 40 3.3.1 Effect of forest types on soil hydraulic properties 40 3.3.2 Variation of SHP in dependence on site conditions 42 3.4 Discussions 47 3.4.1 Effect of tree species on SHP 47 3.4.2 Effect of site conditions on SHP 48 3.5 Synthesis of Results and Conclusions 49 3.6 Chapter References 50 Chapter 4 Synthesis 55 4.1 Understanding the Influence of Tree Species on SHP 56 4.2 Understanding the Influence of Site-Specific Conditions on SHP 59 4.3 Identifying Knowledge Gap in Literature and Advocate Standardisation for Measuring SHP in Forest Soils 61 Chapter 5 Conclusions and Outlook 65 Chapter 6 References 72 Acknowledgements 81 Annexes 83 Annex A –Soil hydraulic conductivity and bulk density values found in literature review 84 References Annex A 90 Annex B –HCC and WRC plots of all samples 93 Annex C – Statistical parameters to determine WRC and HCC from the Hyprop-Fit fitting 104 Annex D – Average values of WRC under beech and spruce forests concerning sand content 107