Imaging spectroscopy reveals the effects of topography and logging on the leaf chemistry of tropical forest canopy trees.
Imaging spectroscopy reveals the effects of topography and logging on the leaf chemistry of tropical forest canopy trees.
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成像光谱揭示了地形和伐木对热带森林冠层树木叶子化学的影响。
DOI：
10.1111/gcb.14903
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发表时间：
2020
影响因子：
11.6
通讯作者：
Swinfield T
中科院分区：
文献类型：
--
作者：
Swinfield T
伐木在热带低地普遍存在，影响了数百万公顷的森林，但它对养分循环的影响仍然知之甚少。一种假设是，伐木会影响磷(P)的循环，因为这种稀缺的养分在被开采的木材和侵蚀的土壤中被移除，导致生态系统功能和群落组成的变化。然而，测试这一点是具有挑战性的，因为P随着地质、地形和气候的变化而在景观中变化。叠加在这些趋势之上的是伐木森林的组成变化，具有更多获取特征的物种更具优势，其特征是叶片磷浓度更高。仅使用传统的实地方法很难解决这些模式。在这里，我们使用机载光探测和测距制导的高光谱图像来绘制叶片养分(即P，N[N])浓度的地图，该浓度使用田间测量的特征进行校准，在婆罗洲东北部超过400千米，包括横跨老树到重复砍伐的森林的景观级干扰梯度。地图显示，冠层叶P和N浓度随海拔升高而降低。这些关系不能用传统的叶片和土壤养分的田间测量来确定。在控制了地形后，伐木森林的树冠叶养分浓度低于老生长区，反映了养分有效性的降低。然而，在伐木区相对较短的斑块中，叶片养分浓度和比叶面积最大，反映出组成向具有获得性特征的先锋物种的转变。采伐林地N：P比增加，说明干扰降低了土壤P的有效性。通过第一次景观尺度的功能叶特征如何变化对伐木的评估，我们发现，随着原木林身高的增加，与老林的差异变得更加明显，这表明随着森林的恢复，磷的限制加剧。
Logging, pervasive across the lowland tropics, affects millions of hectares of forest, yet its influence on nutrient cycling remains poorly understood. One hypothesis is that logging influences phosphorus (P) cycling, because this scarce nutrient is removed in extracted timber and eroded soil, leading to shifts in ecosystem functioning and community composition. However, testing this is challenging because P varies within landscapes as a function of geology, topography and climate. Superimposed upon these trends are compositional changes in logged forests, with species with more acquisitive traits, characterized by higher foliar P concentrations, more dominant. It is difficult to resolve these patterns using traditional field approaches alone. Here, we use airborne light detection and ranging‐guided hyperspectral imagery to map foliar nutrient (i.e. P, nitrogen [N]) concentrations, calibrated using field measured traits, over 400 km2of northeastern Borneo, including a landscape‐level disturbance gradient spanning old‐growth to repeatedly logged forests. The maps reveal that canopy foliar P and N concentrations decrease with elevation. These relationships were not identified using traditional field measurements of leaf and soil nutrients. After controlling for topography, canopy foliar nutrient concentrations were lower in logged forest than in old‐growth areas, reflecting decreased nutrient availability. However, foliar nutrient concentrations and specific leaf area were greatest in relatively short patches in logged areas, reflecting a shift in composition to pioneer species with acquisitive traits. N:P ratio increased in logged forest, suggesting reduced soil P availability through disturbance. Through the first landscape scale assessment of how functional leaf traits change in response to logging, we find that differences from old‐growth forest become more pronounced as logged forests increase in stature over time, suggesting exacerbated phosphorus limitation as forests recover.