###### Abstract
By comparing the coefficients of determination for the modeled and observed NPPs of the three models with each other, it was shown that the coefficient of the Miami model lies between the coefficients of the two other models [16]. Nevertheless, these models estimate the NPP and not the ABM (above-ground biomass production of a single species in terms of dry matter). The NPP, which reflects the gross primary production (GPP) minus the atmospheric loss or respiration (R), can be split into above-ground NPP (ANPP) and below-ground NPP (BNPP). The NPP/GPP ratio is between 0.44 and 0.47, and the ratio ANPP/GPP about 0.29 [18,19], so that a combination of the two results in an ANPP/NPP ratio of 0.62 to 0.66. Furthermore, since a BNPP/NPP ratio of about 0.35 is known [18], it can be suggested that the ANPP/NPP ratio is one minus the BNPP/NPP ratio, which leads to an ANPP/NPP ratio of 0.65. These relations show that it should be possible to use a model developed to estimate the NPP as a basis for estimating the ABM. When one of the NPP models introduced above is used to estimate the ABM, the limiting factors are climatic factors, particularly the mean annual temperature and the mean annual precipitation. This implies that soil conditions can reduce the growth rate and that fertilization supports an increase towards the maximum growth. This was demonstrated in Norway spruce (_Picea abies_ Karst). The production of Norway spruce in northern Sweden increased by 300% and in southern Sweden by 100% when nutrition and water supply were no longer limiting factors [20]. This result impressively showed the impact of the soil, as well as the strong influence that nutrients have on plant production. For that reason and because of the relatively small differences and exceptions regarding soil conditions in Sweden [21,22], the soil was not considered in this study, and the focus was set on climatic factors. With regard to the climate, it is important to know which factors are considered and how the borders are defined. Temperature, for example, is a limiting factor not only during the growth season but also during the period of dormancy. _Miscanthus_ spp. is a perennial C\({}_{4}\) grass, which has a photosynthetic mechanism obviously better adapted to low temperatures than that of various other C\({}_{4}\) plants [23]. Tests in Northern Europe showed, however, that especially in the first two years of cultivation, high losses are possible because of too low winter temperatures [24]. In this context, it can be assumed that climate is the limiting factor for distribution, while soil conditions have a strong impact on the growth rate. Compared to models estimating the potential distribution of a species, the NPP models mentioned above for the production of all species on a site are defined only by the climate variables. A greater specification of a model for a single species has the advantage of providing a more detailed estimate of the productivity or distribution; but the disadvantage is that the model is valid for only one species. As these models are, in general, complex, the adaptation required for further species is quite extensive. In contrast, no method yet exists to transform a NPP model estimating the productivity over all species into a species-specific model estimating the ABM.