Divergent responses of nitrogen availability to aridity in drylands
Divergent responses of nitrogen availability to aridity in drylands
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DOI：
10.1007/s11104-022-05673-1
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发表时间：
2022-09
期刊：
影响因子：
4.9
通讯作者：
Jing Wang;X. Wen
中科院分区：
文献类型：
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作者：
Jing Wang;X. Wen
旱地通常是干旱胁迫的地区，土壤肥力较低。虽然干旱对植被生产力的负面影响是无可争议的，但尚不清楚是水单独限制生产力还是与低氮(N)有效性（相对于植物N需求的N供应）联合限制生产力。在物种水平上测定了土壤和叶片的δ15N浓度和δ15N，并利用反硝化-分解模型模拟了生态系统的N过程。结果模型模拟的总氮供给及其组分（氮沉降、生物固氮和总氮矿化）和模拟的总初级生产力（植物氮需求）随干旱程度的增加而降低。非固氮树种的δ 15nn群落加权δ 15nleaf随干旱程度的增加而增加，而土壤与叶片之间的δ15N差异（δ15NSoil-leaf）随MP和TP的干旱程度的增加而增加。土壤-叶片δ 15nlp随干旱变化不显著。这些结果表明，土壤氮素速效随干旱程度的增加而增加，而土壤氮素速效因土壤氮素需要量大而保持在较低水平。结果表明，δ 15nsoil -leaf比δ15Nsoiland δ15Nleaf更能反映土壤氮素有效性。植被生产力与水分有效度呈负相关，而与氮有效度呈负相关，表明植被生产力受水分而非氮有效度的制约。结论旱地植被生产力是否受到氮素有效性的限制取决于植物生长所需的水分。
PurposeDrylands are generally drought-stressed and have low soil fertility. While negative effects of drought on vegetation productivity are undisputed, it is unclear whether water limits productivity alone or in combination with low nitrogen (N) availability (N supply relative to plant N demand).MethodsOne aridity transect was established in each – the Loess Plateau (LP), Inner Mongolia Plateau (MP), and Tibetan Plateau (TP). Concentrations and δ15N of soil and leaf at the species level were measured, and ecosystem N processes were simulated using DeNitrification-DeComposition model.ResultsModel simulations of total N supply and its components (N deposition, biological N2fixation, and gross N mineralization) and modelled gross primary productivity (plant N demand) decreased with increasing aridity. δ15Nsoiland community-weighted δ15Nleafof non-N2-fixing species increased with aridity, however, difference in δ15N between soil and leaf (δ15NSoil-leaf) exhibited an increasing trend with aridity in MP and TP. δ15NSoil-leafat LP was variable but did not change significantly with aridity. These results implied that N availability increased with aridity in MP and TP but remained low due to high plant N demand in LP. We found that δ15NSoil-leafis a better indicator of N availability than δ15Nsoiland δ15Nleaf. Vegetation productivity was negatively correlated with water availability, but not with N availability along aridity gradients, indicating that vegetation productivity in these ecosystems was constrained by water rather than N availability.ConclusionWhether vegetation productivity is limited by N availability in drylands depends on how much water is available for plant growth.