Generating renewable bioenergy crops requires varietals that are suited to grow under varying environmental conditions necessitating the development and testing of a wide range of poplar (Populus) genotypes. Meanwhile, there is an increasing demand for refining the selection process of high-performing poplars. However, a cost-effective method is still needed to predict the productivity of various poplar genotypes. Photosynthetic capacity and leaf nitrogen are important growth-related physicochemical traits, but measuring them in the field and laboratory is expensive and time-consuming. Alternatively, remote sensing of hyperspectral leaf spectra may serve as a proxy to rapidly estimate these traits, which are associated with absorption, reflection, and transmission of solar radiation. To quantify photosynthetic traits, CO2 response curves were used to estimate Rubisco-limited carboxylation rate (Vcmax), maximum electron transport rate (Jmax), and triose phosphate utilization (TPU). From the same leaves measured for photosynthesis, leaf reflectance was measured with a handheld spectroradiometer. We measured a total of 105 leaf samples, including 6 taxa with 61 different poplar genotypes. For data analyses, Least Absolute Shrinkage and Selection Operator and Principal Component Analysis were used to determine the wavelengths that were the most useful for capturing the variability in the physicochemical data. Results showed that leaf reflectance at 758 nm and 936 nm were crucial wavelengths for predicting Vcmax (RMSPE = 31%) and Jmax (RMSPE = 32%), while 687 nm and 757 nm were important predictors for TPU (RMSPE = 31%), and 709 nm and 927 nm were important predictors for leaf nitrogen (RMSPE = 22%). The wavelengths near 687 nm and 760 nm are the oxygen absorption bands, and also overlap with the chlorophyll fluorescence emission of plants. Therefore, it is possible to apply hyperspectral reflectance models for rapid clonal screening and high-throughput field phenotyping of photosynthetic capacity parameters and leaf nitrogen of various poplar genotypes.

Coal strip mining has left degraded soils throughout the southeastern United States. These soils tend to have low pH, high bulk density, impacted hydraulic processes, and an accumulation of heavy metals that limit revegetation and reforestation efforts. Shortleaf pine (Pinus echinata) has the adaptability to grow on post-mined sites due to being able to tolerate soils with a low pH. It also has the largest native range of pines in the southeastern United States, making it an ideal species for such restoration efforts. Furthermore, soil restoration using a combination of biochar and mycorrhizal amendments can provide many benefits for degraded soils ranging from increasing carbon sequestration, reducing erosion, promoting plant growth, and immobilizing heavy metals. However, limited empirical field trials have been conducted on the success of these soil amendments on both soil health and tree productivity. To provide restoration recommendations to land managers and landowners, we established a field trial in Winston County, Alabama at a reclaimed mining site. In Spring 2021 we planted Shortleaf pine in a complete randomized block design with 30.5x30.5 m spacing with two treatments: biochar and microbial inoculation in four replicates. We measured soil bulk density, pH, heavy metal content, electrical conductivity, carbon content, and nitrogen content both before and after planting every three months. We will also monitor shortleaf pine survival and growth. Our preliminary results for pH, bulk density, and electrical conductivity are within the expected range for shortleaf pine to do well on this post-mined site. Prior to soil treatments and planting, soil pH was 5.55 ± 0.54 pH, dry bulk density was 1.46 ± 0.14 g/cm3, wet bulk density was 1.74 ± 0.12 g/cm3, and electrical conductivity was 273.19 ± 141.33 µS. Soil nitrogen content was 0.15 ± 0.04% and soil carbon content was 2.31 ± 0.76%. The average C:N ratio was 15.8:1. Survival of planted seedlings after three months was 98%. Changes in soil physical and chemical conditions relative to restoration treatments are pending. This study will help support our understanding of biochar’s interaction with mycorrhizal fungi inoculation, role in restoration, and use in southeastern United States soils.