Rapidly and accurately predicting leaf area (LA) and leaf dry mass (LDM) are essential for exploring the response of plant traits to climate change. Empirical models suitable for predicting LA and LDM of a single leaf for various broadleaved tree species at the regional scale have not been proposed. We selected six broadleaved tree species in four mixed broadleaved-Korean pine (Pinus koraiensis) forests in northeastern China, including Betula platyphylla, Tilia amurensis, Populus davidiana, Betula costata, Fraxinus mandshurica and Ulmus laciniata, and measured leaf length, leaf width, leaf thickness, LA and LDM at different canopy layers (top, middle, and low). Using the median of leaf length and width ratio as the classification criterion, the six species were sorted into two groups. We tested whether different canopy layers for each group of broadleaved tree species had significant impacts on the empirical model for predicting LA and LDM. We constructed empirical models suitable for predicting LA and LDM of a single leaf at different canopy layers at the regional scale, and verified their forecast accuracy, and further evaluated their applicability for predicting LA and LDM of same broadleaved tree species in other regions. These results showed that the LA of a single leaf increased significantly with the decreases of canopy height for the six tree species, while the LDM of some broadleaved tree species showed a downward trend. The canopy height had significant impacts on constructing the empirical model for LA and LDM. The average forecast accuracy of empirical model was 95% and 83% for LA and LDM of a single leaf across canopy layers for two groups of broadleaved tree species, respectively. The average forecast accuracy was 94% and 80% for predicting LA and LDM of corresponding broadleaved tree species in other regions, respectively, indicating that the empirical models constructed in this study had a universal applicability in Northeast China.
快捷、准确地测定植物叶片尺度上的叶面积(LA)和叶干质量(LDM)对于探讨植物性状对气候变化的响应机制至关重要,但适于测定区域尺度上不同阔叶植物单个叶片LA和LDM的经验模型尚未提出.本研究以中国东北4个分布区阔叶红松林内的白桦、紫椴、山杨、枫桦、水曲柳和裂叶榆6种阔叶树种为研究对象,分别测定其不同冠层高度(上层、中层和下层)叶片的叶长、叶宽、叶厚、LA及LDM.以叶长与叶宽之比(叶长宽比)的中位数为标准将6种阔叶树分为两组,检验每组树种不同冠层高度对构建预测LA和LDM的经验模型是否存在显著影响;构建适于预测区域尺度上不同冠层单个叶片LA和LDM的经验模型,验证其预测精度;并进一步评估构建的经验模型预测其他区域相同阔叶树种LA和LDM的适用性.结果表明: 整体上6种阔叶树单个叶片的LA随冠层高度的降低呈显著增大趋势,而部分树种的LDM呈下降趋势;冠层高度对构建预测LA和LDM的经验模型具有显著影响;构建的经验模型预测两组阔叶树种不同冠层单个叶片LA和LDM的平均精度分别为95%和83%,且基于这些模型预测其他区域相应树种LA和LDM的平均精度分别为94%和80%,表明本研究构建的经验模型在我国东北区域具有普遍适用性.
Keywords: broadleaf plant; canopy; empirical model; leaf area; leaf dry mass; leaf length and width ratio.