White-tailed deer (Odocoileus virginianus) have increased during the past century in the USA. Greater deer densities may reduce tree regeneration, leading to forests that are understocked, where growing space is not filled completely by trees. Despite deer pressure, a major transition in eastern forests has resulted in increased tree densities. To reconcile conflicting trends, we applied generalized linear mixed models to compare deer densities during 1982 and then 1996 to tree stocking after about 30 years and 15 years of potential reductions of small trees by deer, for the entire eastern US and 11 ecological provinces. We also compiled deer browse preferences and compared preferred browse with trends in tree species composition from historical (1620–1900) and current tree surveys. The forested area of the eastern US, including a prairie ecological province, was equally well-stocked (52%) and understocked (48%) during 2011–2017 tree surveys. For 1982 deer densities, 38% of area had deer densities > 5.8 deer/km2 and for 1996, 66% of area had deer densities > 5.8 deer/km2. Deer densities and tree stocking were not related significantly for the entire eastern US. Deer may reduce tree stocking in the Laurentian Mixed Forest; however, this province had both lower deer densities and greater tree stocking than other provinces. Furthermore, major tree species trends did not match tree browse preferences. Rather than too few trees, too many trees is an ecological problem where historical open oak and pine forests had herbaceous understories, and currently, trees have captured growing space. We attribute other drivers than deer to explain this transition.

中文翻译：

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白尾鹿的密度会影响美国东部森林中的树木种群吗？

在过去的一个世纪里，美国白尾鹿（Odocoileus virginianus）数量有所增加。更高的鹿密度可能会减少树木的再生，导致森林资源不足，树木无法完全填满生长空间。尽管有鹿的压力，但东部森林的一次重大过渡导致树木密度增加。为了调和矛盾的趋势，我们对整个美国东部和11个生态省使用了线性混合模型，以比较1982年和1996年的鹿密度与大约30年和15年后鹿可能减少小树的树木放养量。我们还汇编了鹿浏览偏好，并将首选浏览与历史（1620–1900）和当前树木调查中树木种类组成的趋势进行了比较。美国东部的森林地区，在2011-2017年的树木调查中，包括草原生态省在内的所有树木均存量充足（52％）和存货不足（48％）。对于1982年的鹿群密度，38％的地区鹿群密度> 5.8鹿/平方公里，而对于1996年，66％的地区鹿群密度> 5.8鹿/平方公里。在整个美国东部，鹿的密度和树木的放养没有显着相关。鹿可能会减少劳伦森混合森林中的树木种群；但是，与其他省份相比，该省的鹿群密度较低，树木资源更大。此外，主要树种趋势与树浏览偏好不匹配。生态学问题不是树木太少，而是树木过多，这是一个历史问题，因为历史悠久的开放式橡树和松树林具有草本植物的林下层，目前，树木已占据了越来越大的空间。我们归因于鹿以外的其他驱动因素来解释这种过渡。