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摘要:通过对中亚热带丘陵山区 4 种典型的土地利用方式( 天然林以及由此转变而来的杉木人工林、板栗园和坡耕地) 1 m 深土 壤剖面碳储量、啄 13 C 值和细根生物量的研究,结果表明:土地利用变化 7a 后,土壤剖面( 1 m) 有机碳储量与天然林相比降低了 26%-36%,且 40 cm 以下深层矿质土壤碳储量下降了 19%-45%。 1 m 深土壤 啄 13 C 平均则升高 1译-3译,说明植物群落的光 合类型发生了变化,C 4 植物种对土壤有机碳的贡献增加。 天然林转变后,严重的水土流失、人为扰动和植物物种组成的变化,诱 发深层土壤碳输入减少以及碳流失和矿化损失增加,是导致深层土壤碳储量大幅下降的主因。 土地利用变化后,60 cm 深细根 生物量锐减 50%-99%,且细根主要集中于表土层。 这主要与土壤理化性状劣化、资源有效性大幅降低及天然林转变后植被幼 龄化有关,反映土地利用变化后土地生产力大幅退化。 上述研究结果揭示在中亚热带山地开发、利用和土地转变过程中,加强 天然林保育和中幼林抚育,创新减轻坡土扰动的农艺措施和加强陡坡地退耕,严控水土流失,科学施肥补充损失的土壤有机质 和养分,对于维系山地土壤生产力和山区可持续经营具有长远意义。 关键词:土地利用方式转变;土壤碳贮量;啄 13 C 值;细根生物量;稳定性碳同位素 Response of deep soil organic carbon storage to land鄄use changes in subtropical hilly region of ChinaAbstract: Soil is a major terrestrial carbon pool and most of the soil carbon is stored in the deep soil layers, which contributes to more than half of the total soil carbon storage. Compared with the topsoil carbon storage, carbon reserved in deep soil depth may respond differently to environmental change and land management practices. Thus, it needs to consider the deep soil organic carbon storage in the global carbon cycles. In the subtropical hilly region of China, some soils are deeply weathered and have highly developed profile. These deeply weathered soils may very sensitive to land use changes.Until recently, the dynamics of carbon storage in deep soil, especially its response to land use conversion was largely ignored in the subtropical hilly region of China. In the present study, soil carbon storage at 1 m depth, soil 啄 13 C value and fine root biomass were evaluated within a representative land鄄use sequence in mid鄄subtropical China. The purpose was to evaluate the effect of land use change on the storage and resource of deep soil carbon storage. The land鄄use tpes included

The research on the impact of rainfall on soil respiration is significant to predict accurately the carbon balance of terrestrial ecosystems under future climate change. It is consensus that a certain degree of drought would suppress soil respiration, as well as the processes of water, carbon and nitrogen would be excited after re鄄watering by precipitation or irrigation. However, some research showed the suppression of soil respiration by precipitation. As a disturbance factor, the effect of precipitation on soil respiration is complex because of different vegetation and soil type in different regions. It is necessary to reveal the impact of rainfall amount, intensity and duration on soil respiration under different soil water content, as well to make clear the turning point of suppression or excitation of soil respiration in different regions. In a maize cropland located at eastern Loess Plateau, soil respiration and its components was measured continuously around 3 rainfall incidents based on in situ observation technique, and the impact of rainfall on soil respiration and its components was analyzed. The study was conducted in Shouyang county, Shanxi Province. It is a semi鄄humid area. The seasonal variation of precipitation is large, about 70% of annual amount occurs from June to September. In the field of maize cropland, soil respiration and its components were measured continuously by LI鄄8150 Soil CO 2 Flux System. Soil respiration was divided into microbial respiration and root respiration respectively based on root exclude method. Each treatment was repeated

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