Australian Rivers Institute and School of Environment and Science, Griffith University, Nathan, QLD 4111, Australia.
Science Information Services, Department of Environment and Science, Queensland Government, 41 Boggo Road Dutton Park, QLD, Australia.
Sci Total Environ. 2019 Dec 20;697:134127. doi: 10.1016/j.scitotenv.2019.134127. Epub 2019 Aug 29.
Riparian wetland provides important ecosystem function, such as water filtration and nutrient retention. When land use change in upland from native forest to sugarcane cultivation have important impacts on carbon (C) and nutrient availability in downstream wetland systems. Here, we examined concentrations and stoichiometry of C and nutrients in total, labile, biomass pools in upland soil, riparian wetland and sediment along two distinct transects (sugarcane versus forest). Sugarcane cultivation significantly reduced total C, nitrogen (N), labile C and N in riparian soils by 69%, 62%, 33% and 45%, respectively, but significantly increased NO-N and δN by 99% and 56% in riparian areas. The presence of native forest resulted in significantly higher NH-N concentrations in downstream wetlands. Concentrations of microbial biomass C and N were generally lower, but the abundance of genes associated with nitrifiers (ammonia oxidizing bacteria and archaea) was higher in the sugarcane transect than in the forest transect. These significantly differences between two transects could be attributed to different organic inputs and biogeochemical processes associated with the different vegetation types and management practices in the upland systems. Difference in δC signature from the two transects further confirmed the significant influence of vegetation type on downstream wetlands. Sugarcane cultivation led to a consistent stoichiometric shift in both resource and microbial biomass towards lower C:P and N:P ratios across upland soils, wetlands and sediment, compared with the forest transect. The average total and microbial biomass C:N:P ratios in soil under sugarcane were 136:9:1 and 180:33:1, respectively. The average total and microbial biomass C:N:P ratios in soil under forest were 410:22:1 and 594:76:1, respectively. It is concluded that since microbial demand of C and nutrients is driven by the stoichiometry of the biomass, which is regulated by the resource stoichiometry, a change of resource induced by upland land use change leads to a shift in the stoichiometry of microbial biomass C, N and P.
河岸湿地提供了重要的生态系统功能，如水质过滤和养分保持。当旱地从原生林转变为甘蔗种植时，会对下游湿地系统的碳（C）和养分供应产生重要影响。在这里，我们研究了两条截然不同的样带（甘蔗与森林）中旱地土壤、河岸湿地和沉积物中总碳、养分以及可利用性和生物量库的浓度和化学计量。甘蔗种植使河岸土壤中的总碳、氮（N）、可利用碳和氮分别减少了 69%、62%、33%和 45%，但使河岸地区的硝态氮和 δN 分别增加了 99%和 56%。原生林的存在导致下游湿地中的 NH-N 浓度显著增加。微生物生物量 C 和 N 的浓度通常较低，但在甘蔗样带中与氨氧化细菌和古菌相关的基因丰度高于森林样带。这两个样带之间的显著差异可归因于不同植被类型和旱地系统管理实践带来的不同有机输入和生物地球化学过程。两个样带之间的 δC 特征的差异进一步证实了植被类型对下游湿地的显著影响。与森林样带相比，甘蔗种植导致了旱地土壤、湿地和沉积物中资源和微生物生物量的化学计量比朝着更低的 C:P 和 N:P 比值的一致变化。与森林样带相比，甘蔗地土壤中总生物量和微生物生物量 C:N:P 比值分别为 136:9:1 和 180:33:1。森林土壤中总生物量和微生物生物量 C:N:P 比值分别为 410:22:1 和 594:76:1。因此，可以得出结论，由于微生物对 C 和养分的需求受到生物量化学计量的驱动，而生物量的化学计量又受到资源化学计量的调节，旱地土地利用变化引起的资源变化导致微生物生物量 C、N 和 P 的化学计量发生变化。
