# Elevation pattern of resource allocation in Picea crassifolia Kom. and its coupling mechanism with soil factors in Helan Mountains, China

## TL;DR

This study explores how Qinghai spruce allocates nutrients in response to elevation and soil conditions in China's Helan Mountains.

## Contribution

The study reveals elevation-driven nutrient allocation strategies in Qinghai spruce and their coupling with soil factors in subalpine forests.

## Key findings

- Nutrient allocation in Qinghai spruce varies with elevation, with mid-elevations favoring root allocation.
- Soil nutrient changes influence more plant organs as elevation increases.
- Above-ground nutrient allocation increases at higher elevations to cope with harsher conditions.

## Abstract

Environmental heterogeneity in soil fertility induced by elevation gradients affects trade-offs in tree survival strategies. In arid and semi-arid ecosystems, especially in subalpine coniferous forests in the northwest of China, tree nutrient partitioning strategies and their interactions with the soil environment need to be further explored in depth. We set up three sample plots at different elevations in Helan Mountains, and collected and measured the C, N, and P contents of all organs and soil samples of to explore the nutrient partitioning of Qinghai spruce (Picea crassifolia Kom.) and its coupling with soil. N and P contents in plants and soils showed a synchronized pattern of decreasing and then increasing with elevation, while C only changed synchronously at low to middle elevations. The allocation strategies of different elements among organs varied across the elevation gradient. Plants at middle elevation allocated more N and P to thick roots and less to branches and leaves compared to those at low and high elevations. Plant stoichiometric characteristics have a close response and influence relationship with soil stoichiometric characteristics, as elevation increased, the number of plant organ types that significantly responded to soil nutrient changes increased, and at the same time, and the effect of soil C content on the stoichiometric characteristics of plant showed an enhanced trend. This study elucidates the elevation patterns and driving mechanisms of plant–soil stoichiometric characteristics in montane forest ecosystems, which will contribute to better targeting of forest and tree management and conservation from the perspective of plant nutrient partitioning.

In arid and semi-arid regions, subalpine coniferous forests are highly sensitive to soil conditions. Elevation changes affect both soil nutrients and tree growth strategies. This study tested if Qinghai spruce (Picea crassifolia) employs different nutrient allocation strategies at different elevations in the Helan Mountains. Results showed greater sensitivity to soil environment at higher elevations. At mid-elevations, spruce allocated more N and P to thick roots, optimizing growth. Conversely, at the timberline, it preferentially allocated these nutrients above-ground to cope with harsher conditions.