Lake Macwahoc, International Paper PCT Site

1. Effects of various silviculture treatments on foliar physiology of balsam fir and red spruce trees and its relationship to forest productivity. RAKESH MINOCHA1, STEPHANIE LONG1 AND ROBERT G. WAGNER21. USDA Forest Service, NERS, Durham, NH. Email: rminocha@hopper.unh.edu, 2. University of Maine, Orono, ME Sample Collection Golden Road Site non-PCT Lake Macwahoc Site-PCT Lake Macwahoc Balsam Fir Golden Road Balsam Fir Golden Road Red Spruce Polyamines Polyamines Polyamines Amino Acids Amino Acids Amino Acids Figure 1. Polyamines and their link between nitrogen and carbon metabolism in plants. Inorganic Ions Inorganic Ions Inorganic Ions Chlorophyll Chlorophyll Chlorophyll Basal Area Basal Area Basal Area • RESULTS • Foliar Physiology • Foliar putrescine showed a significant increase with all types and at both intensities of thinning treatments in red spruce for current and one-year-old needles. However, balsam fir did not show any significant changes in putrescine at either site. • There was also a significant increase in the level of spermidine, glutamic acid, and g-aminobutyric acid (GABA) for current and one-year-old needles for both species and at both sites. However, soluble protein levels were not affected by thinning in balsam fir at Lake Macwahoc (data not shown). Thinning at the 33% level did cause a decrease in soluble proteins in current year needles of both species and an increase in soluble proteins in one-year-old needles only in red spruce at Golden Road (data not shown). • Red spruce showed a decrease in foliar exchangeable Ca levels with crown and dominant treatments and this effect was more pronounced at the 50% thinning level. No significant changes in foliar Ca were observed in balsam fir at either site. • Both species showed a decrease in foliar exchangeable Mg levels with crown and dominant treatments and this effect was more pronounced at the 50% thinning level. • There was a significant increase in total chlorophyll in current and one-year-old needles at Golden Road for crown thinning in red spruce, and for crown and dominant thinning in balsam fir. At Lake Macwahoc, 33% thinning also caused an increase in total chlorophyll.  • Growth Data • Mean relative change in basal area [(RBA) = ((BA at T2)-(BA at T1))/ BA at T1] increased with an increase in % thinning in the case of balsam fir at Lake Macwahoc. Within plot tree variation of RBA for this site was significantly less as compared to Golden Road balsam fir and red spruce leading to no clear growth effects that could be observed at Golden Road. The preliminary data indicate that 50% dominant thinning resulted in the least amount of growth in red spruce. SUMMARY Forest management practices such as stand thinning can substantially alter the physiology of trees. Forest health and wood production may later be linked with either an increase or decrease in many of these physiological parameters and should therefore be assessed within a short time after thinning. Having this information will enable us to not only better understand the response of forest trees to thinning but also to make early predictions regarding positive or negative effects of a particular silvicultural treatment on growth.We quantified the effects of various commercial thinning treatments on foliar metabolism of red spruce (Picea rubens) and balsam fir (Abies balsamea) trees in northern Maine. A relationship between the physiological parameters and incremental changes in growth associated with the thinning treatments is presented here. Polyamines (PAs) are low molecular weight organic cations found in all living organisms that play a critical role in growth, development, and stress responses. The common polyamines in plants are spermidine, spermine and their diamine precursor, putrescine. Due to their richness in amine groups and their presence in millimolar quantities in plant cells, polyamines act as storage products of N. Polyamines also reduce NH4/NH3 toxicity. The diamine, putrescine, due to its divalent charge, accumulates in cells in response to deficiency of soil or foliar Ca2+. Whereas Ca availability is dependent on soil nutritional status, cellular putrescine can be synthesized on demand with just C, H, and N (Minocha et al., 2000). Accumulation of putrescine along with the amino acids proline, arginine, and g-aminobutyric acid (GABA) is a common protective mechanism for plants subjected to environmental change. All these metabolites are part of the arginine/ornithine/PA pathway derived from the amino acid glutamic acid (Figure 1). Chlorophyll is also derived from glutamic acid, one of twenty common amino acid that are responsible for biosynthesis of protein. GABA can be produced either directly from glutamate or from the breakdown of putrescine; GABA in turn breaks down into succinate and enters the tricarboxylic acid (TCA) cycle thus recycling the carbon skeleton of polyamines through respiration (Figure 1). Our group has identified that an accumulation of putrescine in conifers and hardwoods is a useful indicator of tree stress (Minocha et al., 1997, 2000; Wargo et al., 2002) under conditions of acidic deposition and/or Al toxicity. We have also demonstrated arginine accumulation in the foliage of conifers and hardwoods that were exposed to high levels of nitrogen. Arginine could thus be used as specific indicator of excess nitrogen availability (Bauer et al., 2004; R. Minocha et al., unpublished data). These biochemical changes were a precursor to reductions in growth, crown deterioration, and tree death at N amendment sites at Harvard Forest, MA. Other changes in one or more of the other amino acids and/or chlorophyll in combination with two common polyamines, spermidine and putrescine, may be indicative of a change in growth. OBJECTIVES AND GOALS To determine the effects of various commercial thinning treatments on physiological parameters (including biochemical stress indicators) of pre-commercially thinned (PCT) and non-PCT spruce-fir stands. The goal is to correlate these early indicators of tree and/or stand health with long-term forest and soil productivity. • CONCLUSIONS • It is too early to establish the physiological parameters that may have the potential to predict the effects of specific silvicultural treatments on forest health and wood production primarily due to the range of variability being observed for growth data within 2-3 years after the treatments. • The main finding so far is: an increase in putrescine when accompanied by a decrease in Ca is a predictor of adverse growth conditions as seen in this study with dominant thinning. This was also observed in several other studies conducted previously by our group on physiological effects of acid deposition or N fertilization; once again supporting the hypothesis that putrescine may compensate for some of the cellular functions performed by Ca. • A similar increase in putrescine, when it occurs in combination with an increase in: spermidine, chlorophyll or Ca, Mg, as well as RBA, may be an indicator of growth. • Foliar Physiology • After thinning, a larger opening in the canopy can cause soil warming and/or decreased competition within a plot. Both changes would result in higher N availability, causing an increase in N containing metabolites such as glutamic acid and spermidine with all thinning treatments. • Soil inorganic ion analyses may help determine if a decrease in some foliar nutrients was the result of soil leaching caused by the thinning treatments. • Independent of soil chemistry changes, one reason for this observed decrease in some of the inorganic ions in foliage may be the result of an increase in light intensity causing increased growth, thereby lessening the amount of nutrients distributed on a fresh weight basis. • Growth Data • Only at the Lake Macwahoc-PCT site was a significant change in RBA seen with thinning treatments. At this site, the trees on all plots at time zero (soon after thinning) were very similar in age and dbh and therefore the growth data is easier to interpret. However, the plots at Golden Road were very different in their initial average dbh at time zero making growth data harder to interpret at this point. Correlations using plot means of foliar parameters: putrescine, spermidine, Ca, Mg, P, and chlorophyll with mean relative change in basal area (RBA) were stronger for Lake Macwahoc balsam fir (caution: n size of only 3) as compared to Golden Road spruce (n size of 7) (data not presented). However, no strong correlations emerged when raw data on a per tree basis were regressed against each other. Foliar data are on fresh mass basis and may need to be converted to total production per foliar biomass in order to regress against RBA. • Species and Site Specific • There were notable differences in foliar physiology between balsam fir and red spruce in response to thinning treatments used at Golden Road. For balsam fir, the response to thinning was similar at both sites; only the intensity was stronger at Golden Road as compared to Lake Macwahoc. Growth effects of thinning were clearly positive for a younger PCT fir stand but not yet as evident on the fir in an old growth-non-PCT stand. Golden Road, Huber Resources Non-PCT Site Thinning Treatments: The Golden Road site has never received PCT and is 58 years old. A 3x2 factorial combination of three types of thinning methods and two levels of relative density reduction (33% and 50% thinning) plus an untreated control were used. Thinning methods were: low thin - where only smaller dbh (diameter at breast height) trees were removed; dominant thin - where trees with largest dbh were removed; and crown thin - where dominant crop trees with largest dbh were selected and surrounding dominant and co-dominant trees removed. First thinning treatments were given in November of 2000. In August of 2003, we collected 113 each of current and past year foliage samples for red spruce and 70 each of current and past year foliage samples for balsam fir (a total of 366 samples at this site). MATERIALS AND METHODS  The methods used for biochemical analyses are all routinely used in our laboratory and most of them are described in Minocha et al., 2000. Lake Macwahoc, International Paper PCT Site Thinning Treatments: The Lake Macwahoc site has been previously commercially thinned and is 42 years old. A 3x2 factorial combination of three levels of timing of entry for thinning (0, 5, and 10 year) and two levels of relative density reduction (33% and 50%) plus an untreated control were used. Each treatment plot is 0.2 acres and is divided into 4 x 0.05 acre subplots. The plots were established in August 2001 and the first thinning was done in September 2001.Balsam fir foliagesamples were collected from plots 2, 4, and 7 in August of 2003. Altogether 70 current year and 70 past year needle samples were collected for balsam fir (a total of 140) at this site. • REFERENCES • Minocha R, Shortle WC, Lawrence GB, David MB, Minocha SC. 1997. A relationship among foliar chemistry, foliar polyamines, and soil chemistry in red spruce trees growing across the northeastern United States. Plant and Soil. 191:109-122. • Minocha R, Aber JD, Long S, Magill AH, McDowell W. 2000. Foliar polyamine and inorganic ion content in relation to soil and soil solution chemistry in two fertilized forest stands at the Harvard forest, Massachusetts. Plant and Soil. 222:119-137. • Wargo PM, Minocha R, Wong B, Long RP, Horsley SB, Hall TJ. 2002. Measuring Stress and Recovery in Lime Fertilized Sugar Maple in the Allegheny Plateau Area of Northwestern Pennsylvania. Can. J. For. Res. 32: 629-641. • Bauer GA, Bazzaz FA, Minocha R, Long S, Magill A, Aber JD, Berntson GM. 2004. Effects of chronic N additions on tissue chemistry, photosynthetic capacity, and carbon sequestration potential of a red pine (Pinus resinosa Ait.) stand in the NE United States For. Ecol. Manage. In Press. ACKNOWLEDGEMENTS: The authors would like to thank our entire field crew with special thanks to Mr. Benjamin Mayer for his assistance with analytical work and to Mr. Robert Keefe for processing of growth data. Figure 2.The effect of various thinning treatments on foliar physiology and basal area of red spruce and balsam fir at Golden Road and balsam fir at Lake Macwahoc. N size per plot are: Golden Road red spruce = 10-20, Golden Road balsam fir = 5-18 (due to availability of live trees) and Lake Macwahoc balsam fir = 15-27.