Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan Grasslands

Uncertainties regarding the responses of soil-available nitrogen and phosphorus (i.e., ammonium nitrogen, NH<sub>4</sub><sup>+</sup>–N; nitrate nitrogen, NO<sub>3</sub><sup>−</sup>–N; available phosphorus, AP) to global changes pose significant challen...

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Main Authors: Guangyu Zhang, Rang Ding, Wei Sun, Gang Fu
Format: Article
Language:English
Published: MDPI AG 2025-05-01
Series:Agronomy
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Online Access:https://www.mdpi.com/2073-4395/15/5/1255
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author Guangyu Zhang
Rang Ding
Wei Sun
Gang Fu
author_facet Guangyu Zhang
Rang Ding
Wei Sun
Gang Fu
author_sort Guangyu Zhang
collection DOAJ
description Uncertainties regarding the responses of soil-available nitrogen and phosphorus (i.e., ammonium nitrogen, NH<sub>4</sub><sup>+</sup>–N; nitrate nitrogen, NO<sub>3</sub><sup>−</sup>–N; available phosphorus, AP) to global changes pose significant challenges to predicting future shifts in plant productivity and livestock development in alpine ecosystems, where these nutrients are critical limiting factors. This study aimed to (1) compare the relative contributions of climate warming, precipitation change, and radiation change on soil-available nitrogen and phosphorus; (2) reveal the decoupling relationships between nutrient contents and their temporal stability; and (3) compare the sensitivity of nutrient contents and their temporal stability. We conducted a regional-scale analysis on soil profiles of 0–10 and 10–20 cm through random forest models across alpine grasslands on the Tibetan Plateau (2000–2020), integrating climate datasets (temperature, precipitation, and radiation) and a normalized difference vegetation index. Temporal stability indicated the reciprocal of the coefficient of variation. Trend analyses were used to quantify the change rate of the nutrient contents and their temporal stability. Three key findings emerged. First, radiation change can exert stronger effects on soil-available nitrogen and phosphorus for some cases. Second, both the contents and temporal stability of NH<sub>4</sub><sup>+</sup>–N, NO<sub>3</sub><sup>−</sup>–N, and AP increased in 13.62–25.80% of grasslands but decreased in 18.74–41.80%. Additionally, 18.71–52.03% of areas showed nutrient increases coupled with decreased temporal stability (while being vice versa in 10.28–26.29%). Third, the relative change in temporal stability exhibited greater ranges (−3081.02% to 3852.73%) than those of the nutrient contents (−355.95% to 947.56%). Therefore, radiation change should be valued in regulating the variations in soil NH<sub>4</sub><sup>+</sup>–N, NO<sub>3</sub><sup>−</sup>–N, and AP. The changes in the contents of NH<sub>4</sub><sup>+</sup>–N, NO<sub>3</sub><sup>−</sup>–N, and AP were not always in sync with the changes in their temporal stability. Stability metrics may better reflect ecosystem vulnerability to global change. All these findings underscore the importance of radiation changes and concurrently considering soil-available nitrogen and phosphorus contents and their temporal stability.
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spelling doaj-art-a983e460d706459595c3bb4b7f4c455e2025-08-20T03:47:48ZengMDPI AGAgronomy2073-43952025-05-01155125510.3390/agronomy15051255Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan GrasslandsGuangyu Zhang0Rang Ding1Wei Sun2Gang Fu3Lhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, ChinaLhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, ChinaLhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, ChinaLhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, ChinaUncertainties regarding the responses of soil-available nitrogen and phosphorus (i.e., ammonium nitrogen, NH<sub>4</sub><sup>+</sup>–N; nitrate nitrogen, NO<sub>3</sub><sup>−</sup>–N; available phosphorus, AP) to global changes pose significant challenges to predicting future shifts in plant productivity and livestock development in alpine ecosystems, where these nutrients are critical limiting factors. This study aimed to (1) compare the relative contributions of climate warming, precipitation change, and radiation change on soil-available nitrogen and phosphorus; (2) reveal the decoupling relationships between nutrient contents and their temporal stability; and (3) compare the sensitivity of nutrient contents and their temporal stability. We conducted a regional-scale analysis on soil profiles of 0–10 and 10–20 cm through random forest models across alpine grasslands on the Tibetan Plateau (2000–2020), integrating climate datasets (temperature, precipitation, and radiation) and a normalized difference vegetation index. Temporal stability indicated the reciprocal of the coefficient of variation. Trend analyses were used to quantify the change rate of the nutrient contents and their temporal stability. Three key findings emerged. First, radiation change can exert stronger effects on soil-available nitrogen and phosphorus for some cases. Second, both the contents and temporal stability of NH<sub>4</sub><sup>+</sup>–N, NO<sub>3</sub><sup>−</sup>–N, and AP increased in 13.62–25.80% of grasslands but decreased in 18.74–41.80%. Additionally, 18.71–52.03% of areas showed nutrient increases coupled with decreased temporal stability (while being vice versa in 10.28–26.29%). Third, the relative change in temporal stability exhibited greater ranges (−3081.02% to 3852.73%) than those of the nutrient contents (−355.95% to 947.56%). Therefore, radiation change should be valued in regulating the variations in soil NH<sub>4</sub><sup>+</sup>–N, NO<sub>3</sub><sup>−</sup>–N, and AP. The changes in the contents of NH<sub>4</sub><sup>+</sup>–N, NO<sub>3</sub><sup>−</sup>–N, and AP were not always in sync with the changes in their temporal stability. Stability metrics may better reflect ecosystem vulnerability to global change. All these findings underscore the importance of radiation changes and concurrently considering soil-available nitrogen and phosphorus contents and their temporal stability.https://www.mdpi.com/2073-4395/15/5/1255temporal stabilityvariable change–temporal stability relationshipclimate changehuman activitiesTibetan Plateau
spellingShingle Guangyu Zhang
Rang Ding
Wei Sun
Gang Fu
Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan Grasslands
Agronomy
temporal stability
variable change–temporal stability relationship
climate change
human activities
Tibetan Plateau
title Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan Grasslands
title_full Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan Grasslands
title_fullStr Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan Grasslands
title_full_unstemmed Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan Grasslands
title_short Soil-Available Nitrogen and Phosphorus and Their Temporal Stability in the Tibetan Grasslands
title_sort soil available nitrogen and phosphorus and their temporal stability in the tibetan grasslands
topic temporal stability
variable change–temporal stability relationship
climate change
human activities
Tibetan Plateau
url https://www.mdpi.com/2073-4395/15/5/1255
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AT rangding soilavailablenitrogenandphosphorusandtheirtemporalstabilityinthetibetangrasslands
AT weisun soilavailablenitrogenandphosphorusandtheirtemporalstabilityinthetibetangrasslands
AT gangfu soilavailablenitrogenandphosphorusandtheirtemporalstabilityinthetibetangrasslands