It is important to understand temporal and spatial variations in the structure and photosynthetic capacity of tropical rainforests in a world of changing climate, increased disturbances and human appropriation. The equatorial rainforests of Central Africa are the second largest and least disturbed of the biodiversly-rich and highly productive rainforests on Earth. Currently, there is a dearth of knowledge about the phenological behavior and long-term changes that these forests are experiencing. Thus, this study reports on leaf area seasonality and its time trend over the past two decades as assessed from multiple remotely sensed datasets. Seasonal variations of leaf area in Congolese forests derived from MODIS data co-vary with the bimodal precipitation pattern in this region, with higher values during the wet season. Independent observational evidence derived from MISR and EPIC sensors in the form of angular reflectance signatures further corroborate this seasonal behavior of leaf area. The bimodal patterns vary latitudinally within this large region. Two sub-seasonal cycles, each consisting of a dry and wet season, could be discerned clearly. These exhibit different sensitivities to changes in precipitation. Contrary to a previous published report, no widespread decline in leaf area was detected across the entire extent of the Congolese rainforests over the past two decades with the latest MODIS Collection 6 dataset. Long-term precipitation decline did occur in some localized areas, but these had minimal impacts on leaf area, as inferred from MODIS and MISR multi-angle observations.

在气候变化、干扰增加和人类占有的世界中，了解热带雨林结构和光合能力的时空变化非常重要。中非的赤道雨林是地球上生物多样性丰富、生产力高的热带雨林中第二大、受干扰最少的雨林。目前，人们对这些森林正在经历的物候行为和长期变化知之甚少。因此，本研究报告了从多个遥感数据集评估的过去二十年叶面积季节性及其时间趋势。来自 MODIS 数据的刚果森林叶面积的季节性变化与该地区的双峰降水模式共同变化，在雨季具有更高的值。来自 MISR 和 EPIC 传感器的独立观测证据以角度反射特征的形式进一步证实了叶面积的这种季节性行为。双峰模式在这个大区域内随纬度变化。可以清楚地辨别出两个次季节周期，每个周期由旱季和雨季组成。这些对降水变化表现出不同的敏感性。与之前发表的报告相反，在过去的二十年里，最新的 MODIS Collection 6 数据集没有检测到刚果雨林整个范围内的叶面积普遍下降。从 MODIS 和 MISR 多角度观测推断，一些局部地区确实发生了长期降水减少，但这些对叶面积的影响很小。