Root water uptake patterns are controlled by tree species interactions and soil water variability
Abstract. Throughfall is the largest source of water entering the soil in forests, and its spatial distribution depends on several biotic and abiotic factors. It is well documented that the distribution of throughfall results in reoccurring higher and lower water inputs at certain locations. However, the role of horizontal root water uptake patterns in understanding the effects of throughfall patterns on subsurface water dynamics remains unresolved. Therefore, here we investigate root water uptake patterns by considering spatial patterns of throughfall and soil water patterns in addition to soil and neighboring tree characteristics. We conducted weekly intensive throughfall sampling at locations paired with soil moisture sensors during the 2019 growing season. We employed a linear mixed effects model to understand controlling factors for root water uptake patterns. Our results show that soil water patterns and interactions among neighbouring trees are the most significant factors regulating root water uptake patterns. Temporally stable throughfall patterns did not influence root water uptake patterns. Similarly, soil properties were unimportant for spatial patterns of root water uptake. We found that wetter locations (rarely associated with throughfall hotspots) promoted greater root water uptake. Root water uptake in monitored soil layers also increased with neighbourhood species richness. Ultimately our findings suggest that complementarity mechanisms within the forest stand, in addition to soil water variability and availability, govern root water uptake patterns.
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