College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, 510642, China.
College of Agriculture, Guangdong Ocean University, Zhanjiang, 524088, China.
Environ Monit Assess. 2019 May 8;191(6):355. doi: 10.1007/s10661-019-7500-6.
We estimated canopy structure and transmitted radiation using hemispherical photography in four monitoring years (2008-2010, 2016) following the 2008 huge ice storm in a subtropical forest in south China, so as to assess changes in canopy biophysical parameters during forest recovery from natural disturbance. Significant decrease in canopy openness (CO), transmitted direct radiation (TransDir), and transmitted diffuse radiation (TransDif), as well as significant increase in leaf area index (LAI), were found in the disturbed forest stand in the subsequent years following the ice storm, indicating rapid canopy recovery. In contrast, these biophysical parameters of the undisturbed forest stand were quite stable during the monitoring years. The strength of relationships between CO and other canopy biophysical parameters decreased in the disturbed stand along the monitoring years. The disturbed stand had common slopes for the CO-TransDir and CO-TransDif models in the first two monitoring years, but different slopes for the CO-LAI model between the first and the subsequent monitoring years, while the undisturbed stand had common slopes for all the regression models in the first three monitoring years following the huge ice storm. These results showed that stronger correlations of LAI or TransDir with CO were characteristic of less complex canopies, such as those damaged by disturbance; the sensitivity of transmitted radiation in response to CO decreased with canopy recovery. Our findings demonstrated that forests with different canopy structure varied in biophysical parameters, which can be quantified by hemispherical photography.
我们在四个监测年份（2008-2010 年、2016 年）中使用半球摄影法估算了树冠结构和透射辐射，这些监测年份是在中国南方亚热带森林中发生的 2008 年特大冰暴之后进行的，以便评估森林从自然干扰中恢复期间树冠生物物理参数的变化。在冰暴之后的随后几年里，受干扰的林分中树冠开阔度（CO）、透射直接辐射（TransDir）和透射漫射辐射（TransDif）显著降低，叶面积指数（LAI）显著增加，表明树冠快速恢复。相比之下，在监测期间，未受干扰林分的这些生物物理参数相当稳定。随着监测年份的推移，CO 与其他树冠生物物理参数之间的关系强度在受干扰的林分中减弱。在最初的两年监测中，受干扰的林分中 CO-TransDir 和 CO-TransDif 模型具有共同的斜率，但在第一个和随后的监测年之间，CO-LAI 模型的斜率不同；而在特大冰暴发生后的前三年监测中，未受干扰的林分所有回归模型都具有共同的斜率。这些结果表明，LAI 或 TransDir 与 CO 的相关性越强，树冠越复杂，例如受干扰破坏的树冠；随着树冠恢复，透射辐射对 CO 的敏感性降低。我们的研究结果表明，具有不同树冠结构的森林在生物物理参数方面存在差异，这些差异可以通过半球摄影法来量化。
