Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts. That biodiversity, reflected in differences in species compositions among sites (beta diversity), can be derived from species replacement (turnover) and is driven by multiple factors. Here, we sought to tackle this issue through two questions related to threatened Brazilian seasonally dry forests: (i) what is the contribution of species turnover to beta diversity? and (ii) which factors drive variations in species compositions among forest patches?
We sampled tree species and environmental variables (soils and climate) in 17 dry forest patches spaced almost 300 km apart. We used the beta diversity partitioning framework to determine the contribution of turnover. We used redundancy analysis, with properly controlled spatial structure, to assess the contributions of the environmental and spatial factors to the variations of the species composition.
Beta diversity among the patches was mainly represented by the turnover component (98.2%), with Simpson dissimilarity superior to other regions of the country (means of 0.89 and 0.71 in multiple site and pairwise measures, respectively). The environmental factors measured explained more than space, representing 30.3% of the variation of the species composition, of which 28.1% was nonspatially structured. We suggest that 300 km represents a threshold at which edaphic and climatic predictors have similar effects in determining community turnover (14.9% and 12.6%, respectively, without spatial structure). Thus, conservation strategies should be considered across landscapes to effectively protect tropical forest diversity, as even considering the different climatic aspects covered by the scale, landscaped edaphic varieties are important drivers of species turnover.
摘要:
了解在不同空间尺度上控制生物多样性分布的因素是保护工作面临的一个关键挑战。生物多样性,反映在不同地点物种组成的差异(β多样性),可以通过物种更替(周转率)获得,并受到多种因素的驱动。在本研究中,我们试图通过研究两个与受威胁的巴西季节性干旱森林相关的问题探讨:I)物种周转对β多样性的贡献是什么? II)哪些因素驱动了林块间物种组成的变化?我们在17个相隔近300公里的干燥森林斑块中对树种进行采样,以及采集环境变量(土壤和气候)。我们使用β多样性划分框架来确定周转率的贡献,采用冗余分析和适合的空间结构来评估环境和空间因素对物种组成变化的贡献。斑块间的β多样性主要以周转组分(98.2%)为代表,Simpson相异度优于国内其他地区 (多位点和两两比较的平均值分别为0.89和0.71)。环境因子对物种组成变化的解释多于空间因素,占物种组成变化的30.3%,其中28.1%是非空间结构的。我们建议,300公里代表一个阈值,在这个阈值上,土壤和气候预测因子在决定群落周转方面具有相似的效应(在不考虑空间结构的情况下,分别为14.9%和12.6%)。因此,应该跨景观考虑保护策略,以有效地保护热带森林多样性,因为即使考虑到不同规模的气候差异, 景观化的土壤种类也是物种周转的重要驱动因素。
关键词:
β多样性,
环境过滤,
生境破碎化,
景观结构,
植物地理学