Ferrari A, Hagedorn F, Niklaus P A
Institute of Evolutionary Biology and Environmental Studies, University of Zurich, 8057, Zurich, Switzerland.
Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), 8903, Birmensdorf, Switzerland.
Oecologia. 2016 May;181(1):25-37. doi: 10.1007/s00442-015-3427-y. Epub 2015 Aug 28.
Despite concerns about climate change effects on ecosystems functioning, little is known on how plant assimilate partitioning changes with temperature. Particularly, large temperature effects might occur in cold ecosystems where critical processes are at their temperature limit. In this study, we tested temperature effects on carbon (C) assimilate partitioning in a field experiment at the alpine treeline. We warmed and cooled soils of microcosms planted with Pinus mugo or Leucanthemopsis alpina, achieving daily mean soil temperatures (3-10 cm depth) around 5.8, 12.7 and 19.2 °C in cooled, control and warmed soils. We pulse-labelled these systems with (14)CO2 for one photoperiod and traced (14)C over the successive 4 days. Plant net (14)C uptake increased steadily with soil temperature. However, (14)C amounts in fungal hyphae, soil microbial biomass, soil organic matter, and soil respiration showed a non-linear response to temperature. This non-linear pattern was particularly pronounced in P. mugo, with five times higher (14)C activities in cooled compared to control soils, but no difference between warmed and control soil. Autoradiographic analysis of the spatial distribution of (14)C in soils indicated that temperature effects on the vertical label distribution within soils depended on plant species. Our results show that plant growth, in particular root metabolism, is limited by low soil temperature. As a consequence, positive temperature effects on net C uptake may not be paralleled by similar changes in rhizodeposition. This has important implications for predictions of soil C storage, because rhizodeposits and plant biomass vary strongly in their residence times.
尽管人们担心气候变化对生态系统功能的影响，但对于植物同化物分配如何随温度变化却知之甚少。特别是在寒冷生态系统中，关键过程处于温度极限时，可能会出现较大的温度效应。在本研究中，我们在高山林线的田间试验中测试了温度对碳（C）同化物分配的影响。我们对种植了偃松或高山滨菊的微观世界的土壤进行升温或降温处理，使冷却、对照和升温土壤中（3 - 10厘米深度）的日平均土壤温度分别达到约5.8、12.7和19.2°C。我们用（14）CO2对这些系统进行一个光周期的脉冲标记，并在接下来的4天追踪（14）C。植物净（14）C吸收量随土壤温度稳步增加。然而，真菌菌丝、土壤微生物生物量、土壤有机质和土壤呼吸中的（14）C含量对温度呈现非线性响应。这种非线性模式在偃松中尤为明显，冷却土壤中的（14）C活性比对照土壤高五倍，但升温土壤和对照土壤之间没有差异。对土壤中（14）C空间分布的放射自显影分析表明，温度对土壤内垂直标记分布的影响取决于植物种类。我们的结果表明，植物生长，特别是根系代谢，受到低土壤温度的限制。因此，温度对净碳吸收的正向影响可能不会伴随着根际沉积的类似变化。这对土壤碳储存的预测具有重要意义，因为根际沉积物和植物生物量在其停留时间上有很大差异。
