Aboveground biomass quantification is essential for determining carbon stocks in forests. Multiple tree biomass models are available, but estimations can be biased outside the fitting range. This is due to the lack of data for larger trees, mainly because of the cost and time required. This study proposed a methodology based on tree crown biomass ratio (crown biomass: total aboveground biomass) modelling. The original data used in the existing biomass models in Spain have been notably extended by the inclusion of stem data from First Spanish National Forest Inventory and other databases, covering better tree size variability. The analysis of the crown biomass ratio against tree size (d²h), allowed us to distinguish three different patterns: an increasing pattern, a constant one, and a decreasing pattern. A new system of biomass models was fitted simultaneously by species, including a model for crown biomass ratio according to the identified pattern, a stem biomass model, and a total aboveground biomass model. Using this methodology, models were fitted for the 29 most important species in Spain. The fitted models result in more accurate and unbiased predictions for stem biomass, and realistic estimations for the crown biomass. This methodology means more robust and flexible biomass estimations with the possibility of using different data sources. The absence of crown information is not an obstacle because this component is a percentage of total aboveground biomass. Moreover, determining the crown biomass ratio pattern allows improving the accuracy of tree biomass estimation beyond the range of tree sizes (2–70 cm) for which these models were fitted.

地上生物量量化对于确定森林中的碳储量至关重要。可以使用多种树木生物量模型，但估计值可能会超出拟合范围。这是由于缺少大树的数据，主要是因为所需的成本和时间。这项研究提出了一种基于树冠生物量比率（冠生物量：总地上生物量）建模的方法。西班牙现有生物量模型中使用的原始数据已得到显着扩展，其中包括来自第一西班牙国家森林清单和其他数据库的茎数据，涵盖了更好的树木大小可变性。冠生物量比对树木大小（d ² h）的分析，允许我们区分三种不同的模式：递增模式，恒定模式和递减模式。一个新的生物量模型系统是按物种同时拟合的，包括根据确定的模式的冠生物量比模型，茎生物量模型和总地上生物量模型。使用这种方法，对西班牙的29个最重要物种进行了模型拟合。拟合模型可得出茎生物量的更准确和无偏的预测，以及冠生物量的现实估计。这种方法意味着可以使用不同数据源进行更可靠，更灵活的生物量估算。缺少树冠信息并不是障碍，因为该部分占地上总生物量的百分比。此外，