Logging, grazing, wood extraction, and anthropogenic fires are pervasive throughout the subtropical dry vegetation of South America leading to changes in woodlands structure and ultimately its degradation. The Chac ohaco biome encompasses the second-largest forest in South America and has a long history of intensive use. We sought to characterize the structure and heterogeneity of its woodlands across biogeographic subunits and climatic gradients, and evaluate structure controls. We quantified canopy height, cover, vertical complexity, vegetation amount above 3 m and total vegetation amount over 58 woodlands within the Argentinean Chaco by means of terrestrial laser scanner. We assessed the relationship between three groups near the maximum, average and minimum values of each structural variable and precipitation, temperature and temperature of the coldest month using quantile regressions. We found large variability in structural attributes within each biogeographical subunit, showing woodland areas with similar structure across broad gradients of climate. This suggests a considerable impact of current and past land use in shaping woodland structures across the Chaco. Overall, structural variables were positively associated with precipitation and temperature, albeit more strongly to the former, except for canopy height, which showed a strong association with mean temperature of the coldest month. We hypothesize that land-use impact on woodland structure decreases with increasing precipitation, as the lack of water may limit the recovery of vegetation structure. Our results contribute to a better understanding of variation in key structural variables of Chaco woodlands in relation to climate and land use.

中文翻译：

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深入了解南美查科林地结构的模式和控制

伐木、放牧、木材开采和人为火灾在南美洲的亚热带干旱植被中普遍存在，导致林地结构发生变化并最终导致其退化。Chac ohaco生物群落包括南美洲第二大森林，并且有着悠久的集约利用历史。我们试图通过生物地理亚单位和气候梯度来描述其林地的结构和异质性，并评估结构控制。我们量化了阿根廷查科内 58 个林地的冠层高度、覆盖度、垂直复杂性、3 m 以上的植被数量和总植被数量通过地面激光扫描仪。我们使用分位数回归评估了每个结构变量的最大值、平均值和最小值附近的三组与最冷月份的降水、温度和温度之间的关系。我们发现每个生物地理亚单位内的结构属性存在很大差异，表明在广泛的气候梯度中具有相似结构的林地区域。这表明当前和过去的土地利用对塑造整个查科的林地结构产生了相当大的影响. 总体而言，结构变量与降水和温度呈正相关，尽管对前者的影响更大，但冠层高度与最冷月份的平均温度密切相关。我们假设土地利用对林地结构的影响随着降水的增加而减少，因为缺水可能会限制植被结构的恢复。我们的结果有助于更好地了解查科林地与气候和土地利用相关的关键结构变量的变化。