模拟增温对中亚热带杉木人工林土壤磷有效性的影响

气候变暖改变与土壤磷循环相关的生物地球化学过程,对陆地生态系统磷循环产生直接或间接影响。为研究亚热带地区杉木人工林土壤磷有效性对增温的响应,开展了模拟增温实验。实验设置对照组及增温组(5℃),经过1.5a的短期增温,对杉木人工林的土壤全磷、有机磷、微生物量磷、有效磷、酸性磷酸酶活性及相关土壤理化性质进行测定,结果表明:增温处理下,土壤酸性磷酸酶活性提高约1.5倍,土壤全磷、微生物量磷以及有机磷含量分别减少了6%、34%和12%,土壤有效磷含量增加25%。可见,短期增温通过提高土壤磷酸酶活性进而促进土壤有机磷矿化和降低土壤微生物固磷量,从而增加土壤磷有效性,但是增温导致潜在可利用的土壤微生物量磷大幅度的降低,将有可能加剧亚热带杉木人工林土壤磷限制。

Effects of simulated warming on soil phosphorus availability in subtropical Chinese fir plantation

Phosphorus (P), one of the most important nutrients in soil, is essential for plant growth, and plays a significant role in maintaining the balance of forest ecosystems. Furthermore, soil P availability is controlled mainly by geochemical and biological processes and can be vulnerable to global climate change. Warming, which has become one of the most important topics of current study, directly and indirectly alters soil P cycling in terrestrial ecosystems; however, to date, most studies have focused on nitrogen deficiency in temperate ecosystems, and have produced inconsistent results regarding the responses of soil P dynamics. Few relevant studies have been conducted in P-deficient tropical and subtropical forest ecosystems. In order to study the potential impacts of warming on soil P fractions related to P availability, we simulated warming in a subtropical Chinese fir plantation, and undertook sampling after one and a half years of short-term warming. The result showed that soil acid phosphatase in the warming treatment was 1.5 times higher compared to that in the control treatment, and that soil available P had increased by 25%, whereas soil total P, microbial P, and organic P had declined by 6%, 34%, and 12%, respectively. The increased soil P availability after short-term soil warming is mainly attributed to an increase in acid phosphatase activity that can promote mineralization of soil organic P, and to the reduced P immobilization of microbe. Despite the increase in soil available P after short-term warming, the significant decrease in microbial P, which is potentially available for plants, is likely to exacerbate P limitation in subtropical Chinese fir plantations. The findings of this study indicate that more attention should be paid to the responses of soil P to climate warming in the subtropical zone and highlight the need for further research.