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Bamboo phenology and life cycle drive seasonal and long‐term functioning of Amazonian bamboo‐dominated forests
Journal of Ecology ( IF 5.3 ) Pub Date : 2020-10-09 , DOI: 10.1111/1365-2745.13512 Belen Fadrique 1 , Daniel Gann 2 , Bruce W. Nelson 3 , Sassan Saatchi 4 , Kenneth J. Feeley 1, 5
中文翻译：
竹的物候和生命周期驱动亚马逊河以竹为主的森林的季节性和长期功能
更新日期：2020-10-09
Journal of Ecology ( IF 5.3 ) Pub Date : 2020-10-09 , DOI: 10.1111/1365-2745.13512 Belen Fadrique 1 , Daniel Gann 2 , Bruce W. Nelson 3 , Sassan Saatchi 4 , Kenneth J. Feeley 1, 5
Affiliation
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- Bamboo‐dominated forests (BDF) extend over large areas in the drought‐prone Southwestern Amazon, yet little is known about the dynamics of these ecosystems. Here, we investigate the hypothesis that bamboo modulates large‐scale ecosystem dynamics through competition with coexisting trees for water.
- We examined spatio‐temporal patterns of remotely sensed metrics (Enhanced Vegetation Index [EVI], Normalized Difference Moisture Index [NDMI]) in >300 Landsat images as proxies for canopy leaf phenology and water content at two time scales: (1) a complete bamboo life cycle (~28 years), and (2) the seasonal cycle; and at two spatial scales: (a) comparing adjacent areas of BDF vs. Terra‐firme forests (TFF) to investigate regional dynamics, and (b) comparing the vegetation classes of bamboo, trees in BDF, and trees in TFF to investigate the effects of bamboo on coexisting trees.
- At the regional scale, BDF showed higher EVI (leaf area density) and lower NDMI (water content) than nearby TFF but these differences disappeared as bamboo died, suggesting a strong influence of bamboo life stage in the functioning of these forests. BDF seasonal cycle showed a bimodal EVI pattern as trees and bamboos had asynchronized leaf production peaks.
- At the scale of vegetation classes, trees in BDF showed lower NDMI (i.e. water content) than trees in TFF except after bamboo mortality, indicating a release from competition with bamboo for water. Canopy water content of trees in BDF was also reduced during bamboo dry‐season greening (increased EVI ~ leaf production) due to increased water demands. Nevertheless, long‐term and seasonal phenology of trees in BDF did not differ from that of trees in TFF suggesting a potential selection for drought‐tolerant trees in BDF.
- Synthesis. Bamboo‐dominated forests have received less attention than other Amazonian forests and their functional dynamics are commonly ignored or misinterpreted. Using remote sensing to characterize forest phenology and water content, we show the distinctive seasonal and long‐term dynamics of BDF and coexisting trees and the importance of bamboo competition for water in shaping this ecosystem. Our results suggest a potential selection for drought‐tolerant trees in BDF since they maintain the same EVI as trees in bamboo‐free forests but with lower water content. A better characterization of BDF and their cyclical dynamics is crucial for accurately interpreting Amazonian forests' responses to extreme climatic events such as high temperatures and droughts.
中文翻译：
竹的物候和生命周期驱动亚马逊河以竹为主的森林的季节性和长期功能
- 在干旱多发的西南亚马逊地区，以竹为主的森林（BDF）遍布大片地区，但对这些生态系统的动态知之甚少。在这里，我们研究了竹子通过与树木共存争夺水来调节大规模生态系统动态的假说。
- 我们在两个时间尺度上检查了超过300幅Landsat图像中遥感指标（增强的植被指数[EVI]，归一化差异水分指数[NDMI]）的时空模式，作为冠层叶片物候和含水量的代理：（1）完整竹子的生命周期（约28年），以及（2）季节周期；在两个空间尺度上：（a）比较BDF与Terrafirme森林（TFF）的相邻区域以研究区域动态，以及（b）比较竹类，BDF中的树木和TFF中的树木的植被类型以调查对树木共存的影响。
- 在区域范围内，BDF的EVI（叶面积密度）和NDMI（水分含量）均比附近的TFF高，但是随着竹子的死亡，这些差异消失了，这表明竹子的生长期对这些森林的功能有很大的影响。BDF季节周期显示出双峰EVI模式，因为树木和竹子的叶片产量高峰不同步。
- 在植被类别的规模上，BDF中的树木显示出的NDMI（即水分含量）比TFF中的树木要低，除了在竹子死亡之后，这表明从与竹子争夺水源中释放出来。由于需水量增加，在竹干季绿化期间（EVI增加到叶片产量），BDF中树木的冠层含水量也减少了。但是，BDF中树木的长期和季节性物候与TFF中树木的长期物候没有区别，这表明BDF中耐旱树木的潜在选择。
- 综合。与其他亚马逊森林相比，以竹为主的森林受到的关注较少，其功能动力学通常被忽略或误解。利用遥感来表征森林物候和水分含量，我们展示了BDF和共存树木的独特季节和长期动态，以及竹子争夺水在塑造该生态系统中的重要性。我们的结果表明，BDF中耐旱树木的潜在选择，因为它们保持与无竹林中的树木相同的EVI，但水分含量较低。BDF及其周期性动态的更好表征对于准确解释亚马孙森林对极端气候事件（例如高温和干旱）的反应至关重要。
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