Impacts of C4 grass introductions on soil carbon and nitrogen cycling in C3-dominated successional systems
Impacts of C4 grass introductions on soil carbon and nitrogen cycling in C3-dominated successional systems
复制标题
C4 草的引入对 C3 主导的演替系统中土壤碳和氮循环的影响
作者：
W. Mahaney;K. Smemo;K. Gross
虽然最近的研究主要集中在外来植物物种对生态系统属性的影响上，但关于恢复个别本地植物物种(生物量和组织化学不同)可能会如何影响生态系统的了解较少。我们研究了三种本地C4草原草在重新引入以非本地C3草为主的演替老田群落11年后对土壤C和N循环的影响。这项研究中考察的物种在预计会影响土壤C和N循环(生物量和组织化学)的特征上有所不同。因此，我们假设，与C3物种相比，C4物种下的土壤循环速率会降低，从而增加土壤中的池塘大小。正如预测的那样，与优势的C3物种相比，C4物种具有更大的生物量和更多的顽固组织[更高的C：N，酸性洗涤纤维(ADF)：N]。这三种C4植物在组织C：N、ADF：N和根生物量方面没有差异，但雄雄龙的地上部分生物量是裂褶草和高粱的两倍多。C4树种下的土壤无机氮水平没有差异，但低于C3树种下的土壤，而且雄配子土壤的原位净N矿化速率略低于C3树种下的土壤。11年后，我们几乎没有发现C4物种下的表层土壤C库比C3物种下的更大的证据，并且物种之间的地下土壤C或N没有差异。11年后，C4物种对两种土壤深度的碳贡献都很大。我们的结果表明，C4物种重新引入老田可以在相对较短的时间尺度上改变C和N的循环，并且不同的C4物种在这些影响的程度上存在差异。提高我们对物种如何影响生态系统属性的理解，对于预测由于土地利用变化、全球变化和物种引进而导致的植物群落变化的生态系统层面的后果至关重要。
While recent research has focused on the effects of exotic plant species on ecosystem properties, less is known about how restoring individual native plant species, differing in biomass and tissue chemistry, may impact ecosystems. We examined how three native C4 prairie grasses affected soil C and N cycling 11 years after reintroduction into successional old-field communities dominated by non-native C3 grasses. The species examined in this study differ in traits that are expected to influence soil C and N cycling (biomass and tissue chemistry). Thus, we hypothesized that cycling rates would decrease, thereby increasing pool sizes in soils under C4 species compared under C3 species. As predicted, the C4 species had greater biomass and more recalcitrant tissue [higher C:N, acid detergent fiber (ADF):N] compared to the dominant C3 species. The three C4 species did not differ in tissue C:N, ADF:N, or root biomass, but Andropogon had more than twice the shoot biomass of Schizachyrium and Sorghastrum. Soils under the C4 species did not differ in inorganic N levels, but levels were lower than in soils under the C3 species, and soils under Andropogon had slightly lower in situ net N mineralization rates compared to those under C3 species. We found little evidence of larger surface soil C pools under C4 species versus C3 species after 11 years and no differences in subsurface soil C or N among species. The C4 species contributed a significant amount of C to both soil depths after 11 years. Our results demonstrate that C4 species reintroduction into old-fields can alter C and N cycling on relatively short timescales, and that individual C4 species differ in the magnitude of these effects. Improving our understanding of how species influence ecosystem properties is essential to predicting the ecosystem-level consequences of plant community alterations due to land use changes, global change, and species introductions.