Hanle Juliana, Duguid Marlyse C, Ashton Mark S
School of Forestry and Environmental Studies Yale University New Haven CT USA.
Ecol Evol. 2020 Jan 28;10(3):1193-1208. doi: 10.1002/ece3.5967. eCollection 2020 Feb.
Many studies have demonstrated the importance of early-successional forest habitat for breeding bird abundance, composition, and diversity. However, very few studies directly link measures of bird diversity, composition and abundance to measures of forest composition, and structure and their dynamic change over early succession. This study examines the relationships between breeding bird community composition and forest structure in regenerating broadleaf forests of southern New England, USA, separating the influences of ecological succession from retained stand structure. We conducted bird point counts and vegetation surveys across a chronosequence of forest stands that originated between 2 and 24 years previously in shelterwood timber harvests, a silvicultural method of regenerating oak-mixed broadleaf forests. We distinguish between vegetation variables that relate to condition of forest regeneration and those that reflect legacy stand structure. Using principal components analyses, we confirmed the distinction between regeneration and legacy vegetation variables. We ran regression analysis to test for relationships between bird community variables, including nesting and foraging functional guild abundances, and vegetation variables. We confirmed these relationships with hierarchical partitioning. Our results demonstrate that regenerating and legacy vegetation correlate with bird community variables across stand phases and that the strength with which they drive bird community composition changes with forest succession. While measures of regeneration condition explain bird abundance and diversity variables during late initiation, legacy stand structure explains them during stem exclusion. Canopy cover, ground-story diversity, and canopy structure diversity are the most powerful and consistent explanatory variables. Our results suggest that leaving varied legacy stand structure to promote habitat heterogeneity in shelterwood harvests contributes to greater bird community diversity. Interestingly, this is particularly important during the structurally depauperate phase of stem exclusion of young regenerating forests.
许多研究已经证明了早期演替森林栖息地对于繁殖鸟类的数量、组成和多样性的重要性。然而，很少有研究直接将鸟类多样性、组成和数量的指标与森林组成、结构及其在早期演替过程中的动态变化指标联系起来。本研究考察了美国新英格兰南部再生阔叶林繁殖鸟类群落组成与森林结构之间的关系，将生态演替的影响与保留的林分结构区分开来。我们在一个森林林分的时间序列上进行了鸟类定点计数和植被调查，这些林分起源于2至24年前的庇护木采伐，这是一种再生橡木混交阔叶林的造林方法。我们区分了与森林更新状况相关的植被变量和反映遗留林分结构的植被变量。通过主成分分析，我们证实了更新植被变量和遗留植被变量之间的区别。我们进行回归分析，以检验鸟类群落变量（包括筑巢和觅食功能类群的数量）与植被变量之间的关系。我们用层次划分法证实了这些关系。我们的结果表明，在不同林分阶段，更新植被和遗留植被都与鸟类群落变量相关，并且它们驱动鸟类群落组成的强度随森林演替而变化。虽然更新状况指标在演替后期解释鸟类数量和多样性变量，但遗留林分结构在林木疏伐阶段解释这些变量。树冠覆盖度、林下多样性和树冠结构多样性是最有力且一致的解释变量。我们的结果表明，在庇护木采伐中保留不同的遗留林分结构以促进栖息地异质性，有助于提高鸟类群落的多样性。有趣的是，这在年轻再生林林木疏伐的结构贫瘠阶段尤为重要。
