@article{coleman_chang_robison_2003, title={DRIS analysis identifies a common potassium imbalance in sweetgum plantations}, volume={34}, ISSN={["0010-3624"]}, DOI={10.1081/CSS-120023227}, abstractNote={DRIS (Diagnosis and Recommendation Integrated System) analysis was applied to fast-growing sweetgum (Liquidambar styraciflua L.) plantations in the southeast United States as a tool for nutrient diagnosis and fertilizer recommendations. First, standard foliar nutrient ratios for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were established using high-yield stands from a region-wide sweetgum fertilization study. DRIS indices were then calculated for the low-yield stands in the same study and stands from four other studies to evaluate foliar nutritional characteristics. Low-yield stands showed strong negative K imbalance, indicating insufficient K, but also showed strong positive Mg imbalance. Potassium imbalance was also observed in the other four data sets tested. DRIS analysis successfully identified the tendency for K insufficiency to increase from early to late in the growing season, probably due to K foliar leaching and low soil K supply. While insufficient N was common in all the stands tested, the DRIS analysis failed to identify any P imbalance. We recommend that K be applied in N:K ratios less than one to correct K imbalance problems in the studied sweetgum plantations. Supra-optimal Ca and Mg levels are expected to decline once insufficient N and K are corrected. DRIS analysis provides the means for diagnosing nutrient imbalance and a potential basis for prescribing corrective amendments in sweetgum plantations. #The submitted manuscript has been authored by a contractor of the U.S. Government. Accordingly, the U.S. Government retains a non-exclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.}, number={13-14}, journal={COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS}, author={Coleman, MD and Chang, SX and Robison, DJ}, year={2003}, pages={1919–1941} }
 @inproceedings{chang_robison_2002, title={Genotype x fertility interactions in seedling sweetgum}, booktitle={Proceedings of the Eleventh Biennial Southern Silvicultural Research Conference : Knoxville, Tennessee, March 20-22, 2002}, publisher={Asheville, N.C. : USDA Forest Service, Southern Research Station}, author={Chang, S. X. and Robison, D. J.}, editor={K. W. Outcalt, P. A. Outcalt and Tucker, R. B.Editors}, year={2002} }
 @inproceedings{chang_robison_2001, title={Genotypic effects of fertilization on seedling sweetgum biomass allocation, N uptake, and N use efficiency}, volume={2}, ISBN={9026519273}, DOI={10.1100/tsw.2001.275}, abstractNote={Screening and selecting tree genotypes that are responsive to N additions and that have high nutrient use efficiencies can provide better genetic material for short-rotation plantation establishment. A pot experiment was conducted to test the hypotheses that (1) sweetgum (Liquidambar styraciflua L.) families have different patterns in biomass production and allocation, N uptake, and N use efficiency (NUE), because of their differences in growth strategies, and (2) sweetgum families that are more responsive to N additions will also have greater nutrient use efficiencies. Seedlings from two half-sib families (F10022 and F10023) that were known to have contrasting responses to fertility and other stress treatments were used for an experiment with two levels of N (0 vs. 100 kg N/ha equivalent) and two levels of P (0 vs. 50 kg P/ha equivalent) in a split-plot design. Sweetgum seedlings responded to N and P treatments rapidly, with increases in both size and biomass production, and those responses were greater with F10023 than with F10022. Growth response to N application was particularly strong. N and P application increased the proportional allocation of biomass to leaves. Under increased N supply, P application increased foliar N concentration and content, as well as total N uptake by the seedlings. However, NUE was decreased by N addition and was higher in F10023 than in F10022 when P was not limiting. A better understanding of genotype by fertility interactions is important in selecting genotypes for specific site conditions and for optimizing nutrient use in forestry production.}, number={electronic}, booktitle={Optimizing nitrogen management in food and energy production and environmental protection: Proceedings of the 2nd International Nitrogen Conference on Science and Policy. TheScientificWorld:1}, author={Chang, S. X. and Robison, D. J.}, year={2001} }
 @article{chang_handley_2000, title={Site history affects soil and plant N-15 natural abundances (delta N-15) in forests of northern Vancouver Island, British Columbia}, volume={14}, ISSN={["1365-2435"]}, DOI={10.1046/j.1365-2435.2000.00424.x}, abstractNote={Abstract}, number={3}, journal={FUNCTIONAL ECOLOGY}, author={Chang, SX and Handley, LL}, year={2000}, month={Jun}, pages={273–280} }
 @article{chang_preston_2000, title={Understorey competition affects tree growth and fate of fertilizer-applied N-15 in a Coastal British Columbia plantation forest: 6-year results}, volume={30}, ISSN={["1208-6037"]}, DOI={10.1139/cjfr-30-9-1379}, abstractNote={Growth of planted seedlings in cutovers dominated by salal (Gaultheria shallon Pursh) is poor largely because of low N availability and understorey competition. In this paper, the response of tree growth and fertilizer recovery to understorey competition was studied. The trees were four years old when (15NH4)2SO4 (200 kg N/ha, 3.38004% enrichment) was applied in 1991 to single-tree plots, with either understorey removed from (treated) or left (control) in the plots. Half of the plots were either sampled after two (1992) or six (1996) growing seasons. Understorey competition continued to significantly reduce height and diameter growth between 1992 and 1996, except diameter growth for western redcedar (Thuja plicata Donn.). Nitrogen and 15N concentration in both tree and understorey components decreased from 1992 to 1996 and N concentration in 1-year-old foliage in 1996 (but not in 1992) was significantly lower in the control than in the treated plots, indicating that the site was low in N supply and the ef...}, number={9}, journal={CANADIAN JOURNAL OF FOREST RESEARCH}, author={Chang, SX and Preston, CM}, year={2000}, month={Sep}, pages={1379–1388} }
 @article{chang_preston_weetman_1999, title={Availability of residual N-15 in a coniferous forest soil: a greenhouse bioassay and comparison with chemical extractions}, volume={117}, ISSN={["0378-1127"]}, DOI={10.1016/S0378-1127(98)00464-2}, abstractNote={Abstract The assessment of soil N availability by chemical extraction methods often needs to be checked by methods which directly measure plant N uptake such as a greenhouse bioassay. In this paper, the recovery of residual 15 N, from humus material samples with 15 N labelled for 24-h, seven-month, and 31-month, in western redcedar ( Thuja plicata Donn ex D. Don) and western hemlock ( Tsuga heterophylla (Raf.) Sarg.) seedlings was investigated in a 342-day greenhouse incubation study and was compared to chemical extraction studies on the same samples. Apparently higher N availability in the 24-h treatment resulted in greater shoot mass in that treatment than in the other two treatments. However, root and whole plant mass were not significantly different among treatments and there were no differences between the species in any of the above measurements. Plants in the 24-h treatment also proportionally took up more residual 15 N from the humus material than those in the other two treatments and thus significantly greater availability ratios were obtained in the former than in the latter two treatments. At the end of the 342-day incubation, a significant amount of 15 N had been immobilised by the soil in the 24-h treatment compared to net 15 N mineralisation in the other two treatments. The high soil mineral N and 15 N contents in the 24-h treatment at the end of the 342-day incubation compared to the low soil mineral N and 15 N contents in the seven-month treatment at the beginning of greenhouse incubation means immobilisation of fertiliser N in the greenhouse incubation was dramatically reduced compared to field situations. Nitrification was negligible before day 182 but was detected at the end of the incubation. Correlation analysis showed that 15 N released during a two-week anaerobic incubation or in a 42-day aerobic incubation, 15 N extracted by 0.01 M KMnO 4 or 2 M KCl, 15 N released by autoclaving or fumigation (-extraction), and even 15 N abundance in the fulvic acid fraction of the organic matter all seemed good indicators of soil residual N availability.}, number={1-3}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Chang, SX and Preston, CM and Weetman, GE}, year={1999}, month={May}, pages={199–209} }
 @article{gautam_mead_frampton_chang_1999, title={Coarse root system characteristics and toppling of clona}, volume={44}, number={1}, journal={New Zealand Journal of Forestry}, author={Gautam, M. and Mead, D. J. and Frampton, C. and Chang, S. X.}, year={1999}, pages={15–18} }