Hydrometeorology organizes intra‐annual patterns of tree growth across time, space and species in a montane watershed

Abstract

Tree radial growth is often systematically limited by water availability, as is evident in tree ring records. However, the physiological nature of observed tree growth limitation is often uncertain outside of the laboratory. To further explore the physiology of water limitation, we observed intra-annual growth rates of four conifer species using point dendrometers and microcores, and coupled these data to observations of water potential, soil moisture, and vapor pressure deficit over 2 yr in the Northern Rocky Mountains, USA. The onset of growth limitation in four species was well explained by a critical balance between soil moisture supply and atmospheric demand representing relatively mesic conditions, despite the timing of this threshold response varying by up to 2 months across topographic and elevation gradients, growing locations, and study years. Our findings suggest that critical water deficits impeding tissue growth occurred at relatively high water potential values, often occurring when hydrometeorological conditions were relatively wet during the growing season (e.g. in early spring in some cases). This suggests that species-specific differences in water use strategies may not necessarily affect tree growth, and that tissue growth may be more directly linked to environmental moisture conditions than might otherwise be expected.

Moisture‐driven xylogenesis in Pinus ponderosa from a Mojave Desert mountain reveals high phenological plasticity

“…Comparative studies conducted on several conifer species from the northern hemisphere have demonstrated that the ending of xylogenesis phases is generally more dispersed compared to their onset, as complex interactions between temperature constraints and water limitations may occur (Rossi et al, ). Tree dimension had very little effect on the timing of wood formation and xylem differentiation, suggesting a predominant climatic control over stem growth in forest ecosystems subject to water limitation (Martin, Looker, Hoylman, Jencso, & Hu, ).…”

Hillslope Topography Mediates Spatial Patterns of Ecosystem Sensitivity to Climate

“…Hwang et al () proposed that the degree of organization of vegetation along hydrologic flow paths effectively represents the dependency of local ecosystems to lateral redistribution of soil moisture. While we acknowledge that lateral redistribution of moisture likely plays a substantial role in organizing vegetation along topographic gradients, topographically organized transfers of water vapor and energy (i.e., vapor pressure gradients) also significantly impact spatial patterns of atmospheric demands for moisture and therefore, ecosystem productivity (Martin et al, ; Oberhuber et al, ). Furthermore, soil processes (such as weathering and transport) and properties (such as texture, depth, and composition) often align along topographic gradients (McAuliffe, ; Pachepsky et al, ; Rasmussen et al, ) and contribute to the organization of soil moisture and plant available nutrients.…”

The Topographic Signature of Ecosystem Climate Sensitivity in the Western United States

“…In the future, it will be important for ecological studies to explicitly identify and incorporate the spatial distribution of active hillslope hydrology processes, and their potential to change with climate shifts, if we are to fully predict ecosystem trajectories in water‐limited landscapes (Fan et al, ; Simeone et al, ; Tai et al, ). One potential way forward is to perform site‐specific analysis across the ecosystem sensitivity gradient (Figures d and a) using field‐based hydrology approaches (e.g., Martin et al, ; Hawthorne & Miniat, ; Hoylman et al, ) or distributed ecohydrology modeling frameworks that couple the water and carbon cycles (e.g., Maneta & Silverman, ; Simeone et al, ; Tague & Band, )…”