Information about nutrient dynamics is of upmost importance in order to contribute to the restoration of degraded forest environments in the Andes of southern Ecuador. This study aims to investigate the differences of nutrient dynamics between a native alder (Alnus acuminata) and an exotic pine (Pinus patula) tree species in this region. Based on litterfall, forest floor and mineral topsoil (0–20 cm) of two pine and two alder plantations, we studied the litterfall production and its seasonality; temporal variations of nutrient concentrations, stoichiometric ratios and potential nutrient return (PNR) of leaf-litterfall; mean residence times (MRT) of nutrients in the forest floor; and assessed soil biogeochemical properties. Our results showed that total litterfall production in pine was twice as high as in alder. Litterfall biomass seasonality was similar for both species and highly associated to periods with less precipitation. Pine exhibited the highest seasonality of nutrient concentrations and stoichiometric ratios. PNR of N, K, Ca, and Mn exhibited the major differences between the species. The annual PNR of N and Ca were higher in alder, while those of K and Mn were higher in pine. Pine exhibited higher MRT values for C, N, P, S, Cu, and Zn, while alder showed the higher for Mg, K, Mn, and Ca. In soils, alder exhibited higher concentrations and stocks of nutrients, but not for C. Although, the soil microbial biomass was similar under both species, microbial activity was different. C and net N mineralization were higher in alder, and nitrification dominated over ammonification processes. In general, our findings show a faster cycling of nutrients in alder than in pine.

中文翻译：

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安第斯森林地区的营养动态：以厄瓜多尔南部的外来和本地物种种植园为例

关于营养动态的信息至关重要，这有助于恢复厄瓜多尔南部安第斯山脉退化的森林环境。这项研究旨在调查本地al木（Alnus acuminata）和外来松（Pinus patula）之间的营养动态差异。）该地区的树种。基于两个松树和两个al木人工林的凋落物，林地和矿物表层土壤（0-20厘米），我们研究了凋落物的产生及其季节性。叶片凋落物的养分浓度，化学计量比和潜在养分返回（PNR）的时间变化；营养物质在森林地面的平均停留时间（MRT）；并评估了土壤生物地球化学特性。我们的结果表明，松树的凋落物总产量是al木的两倍。两种物种的凋落物生物量季节性相似，并且与降水较少的时期高度相关。松树表现出最高的季节性养分浓度和化学计量比。N，K，Ca和Mn的PNR表现出物种之间的主要差异。der和钙的年PNR值较高，而松树中钾和锰的含量较高。松树的C，N，P，S，Cu和Zn的MRT值较高，而der木的Mg，K，Mn和Ca的MRT值较高。在土壤中，al木表现出较高的浓度和养分含量，而对C则没有。尽管两种物种下土壤微生物的生物量相似，但微生物活性却不同。der木中的碳和净氮矿化度更高，硝化作用在氨化过程中占主导地位。一般而言，我们的研究结果表明，al木中的养分循环比松树中的养分循环更快。微生物活性不同。der木中的碳和净氮矿化度更高，硝化作用在氨化过程中占主导地位。一般而言，我们的研究结果表明，al木中的养分循环比松树中的养分循环更快。微生物活性不同。der木中的碳和净氮矿化度更高，硝化作用在氨化过程中占主导地位。一般而言，我们的研究结果表明，al木中的养分循环比松树中的养分循环更快。