三峡库区不同林龄人工橘林土壤异养呼吸及其温度敏感性

土壤异养呼吸是土壤碳库净输出的主要途径, 其对气候变暖的响应已引起国内外学者的广泛关注。对森林生态系统来说, 林龄是影响生态系统碳平衡的一个重要因素。柑橘作为三峡库区第一大支柱产业, 种植面积极广, 对维持该区域的生态平衡起着巨大的调节作用。该文以三峡库区宜昌市郊区种植年限不同的3个橘林土壤为研究对象, 采用室内培养法, 研究在不同温度条件下, 不同林龄土壤的异养呼吸及其温度敏感系数的差异, 探讨该区域生态系统对未来气候变化的潜在响应。结果显示, 随着种植年限的增加, 橘林土壤pH值减小, 有机质和全氮含量显著增加, 土壤微生物生物量碳呈下降趋势。无论在低温、常温还是高温条件下, 林龄较小的橘树土壤异养呼吸及其累积释放量较低。与其他研究相比, 该区域人工橘林土壤异养呼吸的温度敏感系数Q₁₀值相对较低(1.45-1.69), 且随着培养时间的变化而变化。随着种植年限的增加, 人工橘林土壤异养呼吸的温度敏感性逐渐降低, 表明在未来全球气候变暖条件下, 幼龄人工橘林要比成熟林对温度的反应敏感。

Soil heterotrophic respiration and its temperature sensitivity in different-aged orange plantations in Three Gorges Reservoir area of China

Aims Orange (Citrus reticulate) plantations, as the primary industry of the Three Gorges Reservoir area of China, play a significant regulatory role in the maintenance of ecological balance in the region. Our objectives were to examine the main factors controlling soil heterotrophic respiration and its temperature sensitivity in three different-aged orange plantations and discuss their potential responses to future climate change in this region. Methods A laboratory simulation was conducted with soil samples collected at 0–10 cm depth from three different-aged orange plantations in Yichang. Samples were incubated in the laboratory at 5, 15, 25, and 35 °C, respectively, and the alkali absorption method was applied to measure soil respiration. Soil physical and chemical properties were also measured. Important findings With increasing age of the plantation, soil organic content and total nitrogen content increased, while soil pH and microbial biomass carbon decreased. The younger orange plantations released less CO₂ from soil heterotrophic respiration under all temperature conditions. Compared with other studies, temperature sensitivity coefficients of soil heterotrophic respiration (Q₁₀) in the orange plantations in this region were relatively low (1.45–1.69). All Q₁₀ value changed with culture time. The temperature sensitivity coefficient of soil heterotrophic respiration of the plantations decreased with planting years, indicating that younger orange plantations will be more sensitive to future global warming than the older ones.