The role of the hydrological cycle in forest ecosystems : flow path, nutrient cycling and water-carbon interaction

• Main Author: Yan, Yanzi
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Lund University Press 2019
• Subjects: Earth and Related Environmental Sciences; flow path; DOC concentration; groundwater; photosynthesis; Amazon rainforest; catchment geomorphology; Arctic; Climate change
• Online Access: https://lup.lub.lu.se/record/24cd2746-1940-4ba7-9d62-a5e7e98f83aa; https://portal.research.lu.se/files/70412989/Kappa.pdf

Forest ecosystems, covering over a third of land on the Earth, play a significant role in the global hydrological cycle, and influence soil erosion and climate change. However, the distribution, movements, quality of water, and hydrological processes in forested ecosystems are not well understood yet. This thesis aims to improve our understanding of the interaction between forest ecosystems and water cycle from the perspective of flow path, nutrient cycling, and carbon – water interactions. Flow path is particularly important for the study of water storage and distribution, and solute transport and attenuation. However, in dense forest areas, flow path is usually hard to detect from terrain models due to large noise in elevation data, e.g. large sinks. Spurious sinks hinder water flowing downslope and thus likely result in unrealistic flow path estimation. An algorithm that can tackle spurious sinks without altering elevation was proposed and shown to be able to estimate flow path more accurately than traditional methods for different terrain forms. Besides the problem of flow path estimation, the evaluation of flow path estimation has usually been done for the whole catchment, ignoring the variability of the disagreement between estimated flow path and observations among different land cover, soil type, and slopes within a catchment. A number of culverts investigated in fields have thus been used and taken as observations of stream locations for the assessment of flow path evaluation. The results showed that the uncertainty of flow path estimation is strongly related to soil hydraulic productivity, vegetation cover, and slope. Furthermore, nutrient cycling can significantly affect the quality of water. Water is observed getting browner in (sub)arctic regions due to elevated concentration of dissolved organic carbon (DOC). However, it is still not well known how catchment morphometric, e.g. hydrologic connectivity, could affect the distribution and transportation of DOC from terrestrial systems to streams. A ...