Lee Myung-Bok, Carroll John P
Daniel B. Warnell School of Forest and Natural Resources University of Georgia Athens Georgia.
School of Natural Resources University of Nebraska-Lincoln Lincoln Nebraska.
Ecol Evol. 2018 Jun 11;8(14):6909-6920. doi: 10.1002/ece3.4208. eCollection 2018 Jul.
Relationships between avian diversity and habitat area are assumed to be positive; however, often little attention has given to how these relationships can be influenced by the habitat structure or quality. In addition, other components of biodiversity, such as functional diversity, are often overlooked in assessing habitat patch value. In the Sandhills Ecoregion of Georgia, USA, we investigated the relationship between avian species richness and functional diversity, forest basal area, and patch size in pine forests using basal area as a surrogate for overstory structure which in turn impacts vegetation structure and determines habitat quality within a patch. We conducted bird surveys in planted mature pine stands, during breeding season of 2011. We used three classes of stand basal area (BA): OS, overstocked (BA ≥ 23 m/ha); FS, fully/densely stocked (13.8 m/ha ≤ BA < 23 m/ha); and MS, moderately stocked (2.3 m/ha ≤ BA < 13.8 m/ha). MS patches showed more structural diversity due to higher herbaceous vegetation cover than other two pine stocking classes of patches. Total species richness and functional richness increased with the size of MS patches, whereas functional divergence decreased with the size of OS patches (< 0.05). Functional richness tended to be lower than expected as the size of OS patches increased. Greater richness of pine-grassland species was also found at MS patches. Percent cover of MS patches within a landscape influenced positively the richness of pine-grassland species (< 0.05). Our results suggest that (a) avian species-habitat area relationship can be affected by habitat quality (structural diversity) and varies depending on diversity indices considered, and (b) it is important to maintain moderate or low levels of pine basal area and to preserve large-sized patches of the level of basal area to enhance both taxonomic and functional diversity in managed pine forests.
一般认为鸟类多样性与栖息地面积之间呈正相关；然而，人们往往很少关注这些关系会如何受到栖息地结构或质量的影响。此外，在评估栖息地斑块价值时，生物多样性的其他组成部分，如功能多样性，常常被忽视。在美国佐治亚州的桑德希尔斯生态区，我们以森林断面积作为上层林冠结构的替代指标（上层林冠结构进而影响植被结构并决定斑块内的栖息地质量），研究了松林中鸟类物种丰富度与功能多样性、森林断面积和斑块大小之间 的关系。2011年繁殖季节，我们在人工种植的成熟松林中进行了鸟类调查。我们将林分断面积（BA）分为三类：OS，过密（BA≥23平方米/公顷）；FS，全/密郁闭（13.8平方米/公顷≤BA＜23平方米/公顷）；MS，中度郁闭（2.3平方米/公顷≤BA＜13.8平方米/公顷）。与其他两类郁闭度的松林斑块相比，MS斑块因草本植被覆盖度较高而表现出更多的结构多样性。总物种丰富度和功能丰富度随MS斑块大小的增加而增加，而功能离散度随OS斑块大小的增加而降低（P＜0.05）。随着OS斑块大小的增加，功能丰富度往往低于预期。在MS斑块中还发现了更多的松柏草原物种。景观中MS斑块的覆盖百分比对松柏草原物种的丰富度有正向影响（P＜0.05）。我们的结果表明：（a）鸟类物种与栖息地面积的关系会受到栖息地质量（结构多样性）的影响，并因所考虑的多样性指数而异；（b）保持中等或低水平的松林断面积，并保留大面积的该断面积水平斑块，对于提高人工松林的分类多样性和功能多样性很重要。
