Nutrient supply as driver of biomass production and associated ecosystem water fluxes along a land-use and climate gradient

RESPECT研究单位将水文、动态植被和气候学模型结合到新的“生物多样化”陆地表面模型HUMBOL-TD中。HUMBOL-TD可以解决厄瓜多尔潮湿热带山地森林土地利用和气候变化情景下树木性状多样性对生物量生产和相关蒸散量的影响。子项目A3帮助实现了N和P循环模块，大大改善了动态植被模块的预测。在RESPECT的第二期，研究区域将从潮湿的热带山地森林扩展到干燥的热带山地森林。子项目A3将继续关注矿化和风化的养分供应，为模型强迫（N和P沉积、土壤质地、土壤深度、土壤持水量、C、N和P有效性）和模型评估（C和N浓度、N矿化率、养分淋失）提供必要的数据。子项目A3将研究土地利用（原生山地干旱林和农林业）和气候（海拔600和1200米）对干旱林中RESPECT 12个核心地块N矿化、风化释放养分、微生物P保留和养分淋滤的影响。我们将利用离子交换树脂芯测定干旱森林中的养分沉积和淋失，并提供包括C、N和P有效性在内的基本土壤性质。我们将通过在雨季开始和雨季期间的短期孵育以及测量土壤中δ - 13c值和C浓度的垂直分布来确定N矿化率。我们将通过使用开放系统质量平衡来量化风化速率，采用pHstat方法（即在实验室中恒定pH下加速风化），并通过测量土壤中稳定Ca同位素比率的垂直分布来量化风化速率。我们将利用示踪试验评估树木在雨季初和雨季的养分吸收深度。此外，我们将使用一种新颖的180 -标记方法来确定在潮湿和干燥研究地区的所有30个RESPECT核心地块上微生物P的掺入程度。所有数据将在核心地块和工厂功能类型层面提供，甚至个别目标工厂的部分数据也将提供，从而有助于联合响应-效果框架分析。总体而言，子项目A3将加深我们对气候和土地利用变化对高度生物多样性的偏远热带山地森林及其人为替代系统的潮湿和季节性形式的主要养分供应和损失过程的影响的理解。

The Research Unit RESPECT has combined a hydrological, a dynamic vegetation, and a climatological model into the novel “biodiversified” Land Surface Model HUMBOL-TD. HUMBOL-TD allows for addressing the effect of trait diversity of trees on biomass production and associated evapotranspiration in land-use and climate change scenarios for the humid tropical montane forest in Ecuador. Subproject A3 has helped implementing N and P cycle modules, which improved projections of the dynamic vegetation module considerably. In Phase II of RESPECT, the study area will be expanded from the humid to the dry tropical montane forest. Subproject A3 will keep its focus on nutrient supply by mineralization and weathering to provide necessary data from the dry forest for model forcing (N and P deposition, soil texture, soil depth, soil water-holding capacity, C, N, and P availability) and for model evaluation (C and N concentrations, N mineralization rates, nutrient leaching). Subproject A3 will investigate the influence of land use (native montane dry forest and agroforestry) and climate (approximated by the elevations 600 and 1200 m above sea level) on N mineralization, nutrient release by weathering, microbial P retention and nutrient leaching on the 12 core plots of RESPECT in the dry forest. We will determine nutrient deposition and leaching in the dry forest with the help of ion-exchange resin cores and provide basic soil properties including C, N and P availability. We will determine N mineralization rates with a short-term incubation at the beginning and during the high rainy season and by measuring the vertical distribution of delta13C values and C concentrations in soil. We will quantify weathering rates by using open-system mass balances, with a pHstat approach (i.e., accelerated weathering at constant pH in the laboratory), and by measuring the vertical distribution of stable Ca isotope ratios in soil. We will assess the depth of nutrient uptake by the trees at the beginning and during the high rainy season with tracer experiments. Moreover, we will use a novel 18O-labeling approach to determine the degree of microbial P incorporation on all 30 core plots of RESPECT in the humid and dry study regions. All data will be provided at the core plot and plant functional type levels and part of the data even for individual target plants thereby contributing to the joint Response-Effect Framework analysis. Overall, Subproject A3 will deepen our understanding of the effects of climate and land-use change on major nutrient supply and loss processes in the humid and seasonal forms of a highly biodiverse, remote tropical montane forest and its anthropogenic replacement systems.