Balancing the nutrient needs: Optimizing growth in Malus sieversii seedlings through tailored nitrogen and phosphorus effects

The impact of nitrogen (N) and phosphorus (P) on the physiological and biochemical processes crucial for tree seedling growth is substantial. Although the study of plant hydraulic traits in response to N and P is growing, comprehensive research on their combined effects remains limited. Malus sieversii, a key ancestral species of modern apples and a dominant species in Xinjiang's Tianshan wild fruit forest, is witnessing a decline due to climate change, pests and diseases, compounded by challenges in seedling regeneration. Addressing this, a four-year study was conducted to determine the optimal fertilization method for it. The experiment explored varying levels of N (N10, N20, N40) and P (P2, P4, P8), and their combined effects (N20Px: N20P2, N20P4, N20P8; NxP4: N10P4, N20P4, N40P4), assessing their impact on gas exchange, hydraulic traits, and the interplay among functional traits in Tianshan Mountains' M. sieversii seedlings. Our study revealed that all nitrogen treatments enhanced g..., Select sun-oriented, fully expanded leaves. Gas exchange parameters, including net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and intercellular CO2 concentration (Ci), were measured using a Li-Cor 6400 portable photosynthesis system under a photosynthetic photon flux density of 1500 μmol m-2 s-1 between 9:00-13:00 BST. The leaf chamber used was a 2×3 cm unit with a red and blue light source. CO2 concentration was set to 400 ppm with a high flow rate of 500 μmol s-1 to minimize stabilization time for Pn and Gs measurements. 
Predawn water potential (ΨPd) and the midday water potential (ΨM) were measured at predawn (5:00–7:00) and midday (13:00–14:00) using a pressure chamber (Model 3500, PMS Instrument Company, Albany, USA). The evening before measurements, select and mark healthy, north-south oriented branches with colored tape. The next day, measure the water potential of the marked branches. Place the cut branches in the pressure chamber, open the co..., , # Balancing the nutrient needs: Optimizing growth in Malus sieversii seedlings through tailored nitrogen and phosphorus effects

[https://doi.org/10.5061/dryad.brv15dvj0](https://doi.org/10.5061/dryad.brv15dvj0)

All data in this dataset were obtained from field measurements in the field through in situ experiments.

The hydraulic trait and gas exchange data for the NxP4 addition were not included in this study. The notation \"n/a or null\" is used in the dataset to indicate the portions where data is missing.

## Description of the data and file structure

The nutrient addition patterns that emerged from the data are specifically described as follows：

| Treatments | N (g m-2 yr-1) | P (g m-2 yr-1) | Nutrient Description |
| :--------- | :------------- | :------------- | :------------------- |
| CK | 0 | 0 | Control group |
| N10 | 10 | 0 | Low N addition |
| N20 | 20 | 0 | Medi...