CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
Department of Soil Science of Temperate Ecosystems, Department of Agricultural Soil Science, University of Göttingen, Göttingen, Germany.
Glob Chang Biol. 2022 Jul;28(13):4194-4210. doi: 10.1111/gcb.16205. Epub 2022 May 2.
Increasing phosphorus (P) inputs induced by anthropogenic activities have increased P availability in soils considerably, with dramatic effects on carbon (C) cycling and storage. However, the underlying mechanisms via which P drives plant and microbial regulation of soil organic C (SOC) formation and stabilization remain unclear, hampering the accurate projection of soil C sequestration under future global change scenarios. Taking the advantage of an 8-year field experiment with increasing P addition levels in a subalpine forest on the eastern Tibetan Plateau, we explored plant C inputs, soil microbial communities, plant and microbial biomarkers, as well as SOC physical and chemical fractions. We found that continuous P addition reduced fine root biomass, but did not affect total SOC content. P addition decreased plant lignin contribution to SOC, primarily from declined vanillyl-type phenols, which was coincided with a reduction in methoxyl/N-alkyl C by 2.1%-5.5%. Despite a decline in lignin decomposition due to suppressed oxidase activity by P addition, the content of lignin-derived compounds decreased because of low C input from fine roots. In contrast, P addition increased microbial (mainly fungal) necromass and its contribution to SOC due to the slower necromass decomposition under reduced N-acquisition enzyme activity. The larger microbial necromass contribution to SOC corresponded with a 9.1%-12.4% increase in carbonyl C abundance. Moreover, P addition had no influence on the slow-cycing mineral-associated organic C pool, and SOC chemical stability indicated by aliphaticity and recalcitrance indices. Overall, P addition in the subalpine forest over 8 years influenced SOC composition through divergent alterations of plant- and microbial-derived C contributions, but did not shape SOC physical and chemical stability. Such findings may aid in accurately forecasting SOC dynamics and their potential feedbacks to climate change with future scenarios of increasing soil P availability in Earth system models.
人为活动导致的磷（P）输入增加，极大地增加了土壤中 P 的有效性，对碳（C）循环和储存产生了巨大影响。然而，P 驱动植物和微生物调节土壤有机碳（SOC）形成和稳定的潜在机制尚不清楚，这阻碍了在未来全球变化情景下准确预测土壤 C 固存。利用青藏高原东部亚高山森林中 P 添加水平增加的 8 年野外实验，我们研究了植物 C 输入、土壤微生物群落、植物和微生物生物标志物以及 SOC 物理和化学分数。我们发现，持续的 P 添加减少了细根生物量，但不影响总 SOC 含量。P 添加减少了植物木质素对 SOC 的贡献，主要是由于香草型酚类物质的减少，同时甲氧基/N-烷基 C 减少了 2.1%-5.5%。尽管由于 P 添加抑制了氧化酶活性，木质素分解减少，但由于细根的 C 输入减少，木质素衍生化合物的含量也减少了。相比之下，由于降低 N 获得酶活性导致的腐殖质分解速度较慢，P 添加增加了微生物（主要是真菌）腐殖质及其对 SOC 的贡献。较大的微生物腐殖质对 SOC 的贡献与羰基 C 丰度增加 9.1%-12.4%相对应。此外，P 添加对慢速循环的矿物结合有机 C 库没有影响，并且 SOC 化学稳定性由脂肪族和抗降解指数表示。总的来说，在亚高山森林中，8 年来的 P 添加通过改变植物和微生物来源 C 的贡献来影响 SOC 组成，但不会影响 SOC 的物理和化学稳定性。这些发现可能有助于在地球系统模型中，通过未来土壤 P 有效性增加的情景，准确预测 SOC 动态及其对气候变化的潜在反馈。
