SPP 1685: Ecosystem Nutrition: Forest Strategies for Limited Phosphorus Resources

磷是一种有限的资源，有越来越多的辩论有关的原则，严格的磷循环。森林生态系统普遍表现出较高的磷利用效率，这一现象背后的过程仍然没有得到解决。优先方案SPP 1685的成员应用并完善了生态系统营养的概念，该概念的基础是整合从不同空间和时间尺度以及不同学科获得的结果，以揭示这些过程。在第一阶段进行的研究，是针对确定的过程，相互作用和反馈与温带森林生态系统的磷营养。我们测试的假设，植物和微生物群落建立在富P网站遵循P收购策略引入P从原生矿物进入地球化学P循环。随着母质供磷量的减少，林分的供磷策略转变为磷的紧循环，以维持林分对磷的需求。对硅酸盐岩石上的五个山毛榉森林生态系统的分析进行了调整，以检验这一假设，这些生态系统代表了具有不同母质的磷地质序列，因此具有不同的磷总储量（160 <$900 g P m-2;下至1 m土壤深度）。这些分析与个别项目使用的其他实验方法相联系。各个项目涵盖了从微米到集水区的空间尺度和从数秒到数百万年的时间尺度。此外，许多方法已被开发或调整，以适应与森林生态系统中磷的挑战性分析有关的具体要求，其中磷浓度部分极低。这些方法上的发展也为优先方案第二阶段计划进行的分析提供了有希望的工具。在优先计划的第一阶段，收集了有关土壤磷状况及其空间异质性、植物、植物根系和微生物的反应以及生态系统内磷通量的宝贵信息。事实上，许多研究提供的证据表明，在磷丰富的网站和P-贫网站的P紧密循环山毛榉林强烈的磷获取。土壤生物多样性、活性和空间分布的变化以及植物根系对磷的吸收效率和植物体内磷的转移似乎是这些不同策略背后的过程。通过使用这些策略，生物体改变土壤性质，例如森林地面的周转率，土壤有机质的质量和土壤中P的空间分布和形态以及P通量。从第一阶段获得的经验和发展提供了独特的机会，以解决仍然悬而未决的问题，控制和驱动程序的P战略，在不同的时间和空间尺度上的P动态或P和OC动态之间的关系，以及人类对P营养的影响。

Phosphorus is a limited resource and there is increasing debate regarding the principles of tight P recycling. Forest ecosystems show commonly high P use efficiencies and the processes behind this phenomenon are still unresolved. The members of the priority programme SPP 1685 have applied and refined the concept of ecosystem nutrition, which is based on the integration of results obtained from different spatial and temporal scales and from different disciplines, to unravel these processes. The studies conducted in the first phase, were directed to the identification of processes, interactions and feedbacks associated with the P nutrition of temperate forest ecosystems. We tested the hypothesis that plant and microbial communities established at P rich sites follow a P acquiring strategy introducing P from primary minerals into the biogeochemical P cycle. With decreasing P supply by the parent material, the strategy changes into tight P cycling to sustain the P demand of the forests. The analyses of five beech forest ecosystems on silicate rock representing a P geosequence with different parent materials and thus different total P stocks (160 ¿ 900 g P m-2; down to 1m soil depth) were adjusted to test this hypothesis. These analyses were linked to additional experimental approaches used by individual projects. Spatial scales from micrometers up to the catchment scale and temporal scales from seconds to millions of years have been covered by individual projects. In addition, many methods have been developed or adjusted to the specific requirements related to the challenging analysis of P in forest ecosystems, where P concentrations are in part extremely low. These methodological developments provide promising tools also for ongoing analyses planned for the second phase of the priority programme. Valuable information regarding the P-status of soils and its spatial heterogeneity, the response of plants, plant roots and microbes, and regarding the P fluxes within the ecosystems has been gathered in the first phase of the priority programme. In fact, many of the studies provide evidence for intense P acquiring of beech forests at P- rich sites and tight recycling of P at P- poor sites. Changes in the diversity, activity and spatial distribution soil organisms and in the P-uptake efficiency of plant roots and the transfer of P within plants seem to be the processes behind these different strategies. By using these strategies the organisms change the soil properties, for example the turnover rate of the forest floor, the quality of soil organic matter and the spatial distribution and speciation of P in soils as well as P fluxes. The experience and developments gained from the first phase provide unique opportunities to address still open questions regarding controls and drivers of P strategies, relations between the P dynamics on different temporal and spatial scales or between P and OC dynamics, and human impact on P nutrition.