Private land management is more important than public land in sustaining oaks in temperate forests in the eastern U.S.

Preserving the abundance and stocking of oaks (Quercus spp.) has become increasingly challenging in temperate hardwood forests of the eastern US in recent decades due to a remarkable shift in dominance to mesophytic species (e.g., red maple Acer rubrum). Studies have shown that efforts to sustain oaks while restraining maples yield limited success. Given that a significant portion of forestlands in the eastern U.S. are privately owned, it is critical to assess whether current forest management on cross-ownership forests can achieve those objectives. However, such assessments are rare. In this study, we employed a landscape modeling approach to investigate the long-term outcomes (i.e., 150-year forest composition and structure) of business-as-usual management and alternative management in a large, temperate hardwood forest landscape in Ohio, US. The business-as-usual management continues the current existing management practices, whereas the alternative management increases the pace and scale of forest management on both private and public lands to favor oaks. We compared the basal area and relative dominance for oaks (including Q. alba, Q. coccinea, Q. prinus, Q. rubra, and Q. velutina) and maples (including A. rubrum, A. saccharinum, and A. saccharum). Our results demonstrate that the implementation of business-as-usual management practices on both private and public lands may not effectively ensure the long-term sustainability of oak populations, but instead promote the proliferation of maple species over time. By contrast, alternative management on both private and public lands can effectively sustain oaks across a range of diameter classes while mitigating the growth of large, dominant maples. Our study emphasizes the influential role of private lands in driving oak-maple dynamics at the regional scale, as they can generate significant regional effects even when public lands continue with their business-as-usual management practices. Starting conditions based on landownership are crucial considerations for understanding these dynamics over time.

Multi-nutrient stoichiometry of Chinese hickory (Carya cathayensis) saplings: plant organs vary in their response to nitrogen fertilization.

Nitrogen (N) enrichment from excessive fertilization in managed forests affects biogeochemical cycles on multiple scales, but our knowledge of how N availability shifts multi-nutrient stoichiometries (including macronutrients: N, phosphorus, potassium, calcium, magnesium and micronutrients: manganese, iron and zinc) within and among organs (root, stem and leaf) remains limited. To understand the difference among organs in terms of multi-nutrient stoichiometric homeostasis responding to N fertilization, a six-level N supply experiment was conducted through a hydroponic system to examine stem growth, multi-nutrient concentrations and stoichiometric ratios in roots, stems and leaves of 2-year-old Chinese hickory (Carya cathayensis Sarg.) saplings. Results showed that N supply significantly enhanced leaf length, width, basal diameter and sapling height. Increasing the rates of N also significantly altered multi-nutrient concentrations in roots, stems and leaves. Macronutrients generally respond more positively than micronutrients within organs. Among organs, leaves and stems generally responded more actively to N supply than roots. The stoichiometric ratios of nutrients within different organs changed significantly with N supply, but their direction and degree of change varied by organ. Specifically, increased N supply reduced the ratios of both macronutrients and micronutrients to N in plant organs, while increased N supply elevated the ratios of P to other nutrients. With N fertilization, ratios of micronutrients decreased in leaves and stems and increased in roots. In particular, leaf N and stem Mn stoichiometries responded strongly to N availability, indicating stimulated N uptake but a decreased risk of Mn2+ accumulation to excessive N. Overall, Chinese hickory saplings responded positively to increasing N availability in terms of stem growth, but the multi-nutrient stoichiometric homeostasis was distinctively organ-dependent. These results are expected to enhance our understanding of N-induced changes in homeostasis of multiple nutrients at the organ level and may offer new insights into how plants adapt to increasing N fertilization.