To the uninitiated eye an aerial photo of Fairbanks’ surrounding area includes patches of what might appear to be the channels left by the workings of a bark beetle grub. These series of parallel mounds with sequences of smaller undulations on their surfaces are actually composed of coarse gravel and are the product of some forty years of gold dredging. Started in 1928, dredging was concentrated in several of the tributary valleys of the Tanana River and Goldstream Creek. Some of these tailings piles support lush growth while others are relatively bare. At present, no ecologically oriented studies, either qualitative or quantitative, have been published concerning the gold dredge tailings. It was therefore the intent of this study to obtain a broad picture of the present stage of revegetation, in order that further ecological work and, hopefully, assisted rehabilitation may be facilitated.Introduction -- Methods -- Preliminary results -- Stands with little vegetation -- Intermediate stands -- Well developed stands -- Concluding remarks

McKendrick, J.D., Neiland, B.J., and Holmes, K.

English

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Open F i l e  Report No. 80-2 NATURAL REVEGETATION OF PLACER MINED LANDS OF INTERIOR ALASKA I1 by J . D .  McKendrick, B.J. Neiland, and K .  Holmes Final Report  NATURAL REVEGETATION OF. PLACER MINED LANDS OF INTERIOR ALASKA XI Submitted to Mining and Mineral Resources Research I n s t i t u t e  Office of Surface Mining U.S. Department of Interior Washington, D.C. 70740 Grant No. G5184001 March 1980 Jay D. McKendrick Bonita J. Neiland Kay Holmes, Graduate  Student A g r i c u l t u r e  & Land Resources Management Mineral Industry Research Laboratory School of Mineral Industry . University of Alaska Fairbanks, Alaska 9 9 7 0 1  TABLE OF CONTENTS Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 8 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . 28  P r e l i m i n a r y R e s u l t s  . . . . . . . . . . . . . . . . . . . . 30 S tands  With L i t t l e  V e g e t a t i o n  . . . . . . . . . . . . . . . 3 1  I n t e r m e d i a t e  S t a n d s  . . . . . . . . . .  . , .  . . . . . . . . 3 1  Well Developed S t a n d s  . . . . . . . . . . . . . . . . . . . 3 2  Concluding Remarks . . . . . . . . . . . . . . . . . . . . . 3 3  Introduction: To the uninitiated eye an aerial photo of Fairbankst surround- ing area includes patches of what might appear to be the channels left by the workings of a bark beetle grub. These series of parallel mounds with sequences of smaller undulations on their surfaces are actually composed of coarse gravel and are the product of some forty years of gold dredging. Started in 1928, dredging was concen- trated in several of the tributary valleys of the Tanana River and Goldstream Creek. Some of these t a i l i n g s  piles support lush growth while others are relatively bare. At present, no ecologically oriented studies, either qualitative or quantitative, have been published concerning the gold dredge tailings. It was therefore the intent of this study to obtain a broad picture of the p~esent stage of revegetation, in order that further ecological work and, hopefully, assisted rehabilitation may be facilitated. Methods : In an attempt to obtain preliminary baseline information on the present vegetational condition of the gold mine tailings, field work was carried out in a selected area of tailings near Fox, Alaska, approxinately eight miles north-northeast of Fairbanks (64057'N, 147O35'W). Field work involved an initial reconnaissance of a large area surrounding Fox, a subsequent semi-quantitative description of a number of stands, and a limited amount of quanti- tative ~arnpling of a small number of selected stands. A search for pertinent literature was begun in the spring of 1979 and is continuing. Consultations with Mr. Dan Eagan, vice p p e s i d e n t  of the ~ l a s k a  Gold Company and Dr. Earl ~eistline, Dean, Schosl of Mineral Industry, are greatly appreciated and were in- valuable in the choosing of a study area and subsequent work. With the assistance of Mr. Eagan and ihe use of the dredging maps in the possession of Alaska Gold Co., approximate dates of mining were obtained for most tailings observed. Selection of quantitative and semi-quantitative sites necessi- tated considerations of both physical and biological factors operating on individual tailings heaps that might possibly influence subsequent revegetation. Physical factors varying from site to site included micro- and mesotopography, gross shape and orientation of the mounds, microclimate, differing wind patterns, and state of weathering and geologic composition of substrate gravels and decayed bedrock. The main biological factor thought to be important to recolonization was nearness to seed source. Recause a l l  of these conditions could not be held constant between masses of different ages, and not even between masses of tailings of the same age, it w a s  decided that most of the intensive work should be done in one general area in an effort to minimize variabi-lity. The great complexity of physical and vegetational patterns of t a iL i -ngs  of the same age made it impossible to include in-depth studies of tailings of differing ages within the limited time and resources available, and these were given only cursory consideration. Intensive work, including all the quantitative work and a majority of the semi-quantitative work, was done in the lower Goldstream Creek area to the west of the Steese Highway and the Trans-Alaska Pipeline. General reconnaissance of the area and collection of vascular and nonvascular plants began in May of 1979. Species identifica- tion is continuing with the use of the University of Alaska Herbarium. Semi-quantitative work followed in June and representative homogeneous stands were singled out for further study. Homogeneity was determined largely by the general overall appearance of indi- vidual areas. Dominant life forms,.density 'of vegetation and height of vegetation were three structural components used in making this decision. Once the stand was selected, major floristic components were identified and given relative cover values. Occular estimates of species cover were based on an increasing familiarity with the vegetation in the area and are not of a highly precise nature. The  following estimates were made for these sites: ground cover compo- sition and percentages, percentage of fines mixed with gravels, average size of gravel, and height cf and distance between consecu- tive undulations. In addition, average depth of the litter layer was estimated and the presence of decayed bedrock clumps was noted. The following items were also obtained or observed on all semi-quantitative and quantitative stands: general .orientation of t h e  mounds, steepness of slope (if the stand was on a side slope) and whether or not the dredge was moving up-or downstream when depositing gravel. At the more intensive level, four quantitative stands were chosen, three of them on adjacent mounds which represented three different degrees of revegetation. The fourth was an extremely densely vegetated area. The stands ranged fron approximately 2,400 to 4,500 square feet in size. These were paced off and a grid was set up. All tree species were mapped, their heights were estimated and either their basal diameters or diameters at breast height (dbh) were measured. The largest trees in each stand were cored for aging purposes. Mapping provides a permanent record of t h e  vegetative status of these differing stands and will allow changes to be followed over a period of time. Mapping also furnishes the only practical method of securing reasonably precise quantitative data from a limZted number of homogeneous stands that were too small to be sampled. Hulten's Flora was used as a guide.in field identification of vascular plants; Dahl and ~ r o ~ ' s  Macrolichens of Denmark, F.inland, Norway and Sweden and Crum's Mosses of the Great Lakes rarest were used for field identi- fication of nonvascular plants. Those species that could not be positively identified in the field were collected. Tall shrubs were also mapped and much the same information that was gathered for tree species was collected for tall shrubs. Individual shrubs with more than one basal stem were  assigned a clump diameter and an average stem diameter. L o w  shrubs and herbs were mapped in the cases where they could not be adequately sampled. Photographs supplemented information obtained on quantitative stands. Ground cover, including herbaceous, lod shrub, moss and lichen cover was obtained by systematic quadrat sampling. An equal number of quadrats from the tops and bottoms of undulations were sampled. Protruding clumps of what was thought to be decaying bedrock were sampled separately as they appeared to support lichens and mosses in amounts differing from the the surrounding gravel substrate. In addition, much of the information collected for the semi-quantita- tive stands was also obtained for the quantitative stands. Soil and plant samples were gathered from each stand f ~ r  subsequent nutrient analysis. Nutrient analysis will allow tentative conclusions to be drawn as to whether or not soil nutrient status is a factor in limiting plant growth. Complete nutrient analysis is being performed by the soils testing laboratory at the Palmer Research Center. All field data were collected in the summer of 1979 and are currently being analyzed and reduced. This report represents the present status of- the project and the final results will be written up and included in a graduate thesis which will be submitted to the funding agency. Preliminary Results: Few conclusive results are available at the present stage of analysis but the following observations can be tentatively presented. Although the dates of mining of most of the tailings heaps looked at in the lower Goldstream area did not vary more than 10 years, the amounts of vegetation present on those tailings varied widely. A direct correlation between age (date mined) and degree of growth seemed doubtful, at least on those equal-age mounds observed. The only physical factor that was conspicuously correlated with degree of revegetation was the amount of fines mixed in with surficial gravels. Presence of fines ranged from about 5% of the total. rooting :depth substrate to over 50%. Further data analysis may allow other correlative factors involved to be detected. Many things were discovered over the course of the field season, that, had they been known prior to investigation, would have changed some approaches to the study. It was anticipated that more obvious correlations between both age and amount of fines and vegetative state would be found. Many aspects could not be dealt with and will have to be left to further study. Stands With Little Vegetation: The initial reconnaissance and subsequent semi-quantitative work revealed a wide array of vegetative types. At one end of the spectrum, there were the relatively bare sites. A small p2rcentage of fines was intermixed with the gravel on these sites. Except for an occasional birch sapling there were no tr'ee species present. Willows, or any of the other tall shrub species found on t h e  more developed sites, were also found in small amounts. Bare gravel predominated in the ground cover and any accumu- lated litter was negligible. Members of the moss genus, Grimmia, were the most common of the moss species, though again they were not found in abundance. The only plant types that occurred in substantial amounts were species of lichens, especially Stereocaulon species, Umbilicaria species and different crustose forms. Even in the case of Stereocaulon, however, it was observed that the lichen was found in denser mats when associated with patches of mineral soil. Intermediate Stands Between the bare sites and those with nearly 100% tree cover were a wide variety of vegetation types. Most of these stands in- cluded a few trees (dbh 2 "  and taller than 10') and an equal or greater number of saplings (dbh 2"  and less than 10' tall). Paper birch, Betula papyrifera, was the predominant tree species occurring to some extent in all sites observed. Quaking aspen, Populus tremuloides, and balsam poplar, Populus balsamifera, were less widespread and in general found I n  lesser abundance than birch. Where balsam poplar grew, it was often either dying out or had dead tops or dead limbs. This may be a consequence of a lack of water during particularly dry summers. It was not found in great abun- dance when in association with birch. Varying proportions of three willow species were found in these intermediate stands: Salix bebbiana (the most prevalent of the three), S. alaxensis and S. arbusculoides. Other shrubs including ~ l n u s  crispa, Rosa ~cicularis and Viburnum edule were found only occasionally; Shepherdia canadensis and Ribes triste were rare in these stands. Many of the willows had dead branc,hes. Low shrubs included Ledum palustre ssp. decumbens and s s p .  groenlandi.curn, Arctostaphylos uva-ursi, Vaccinium uliginosum and Empetrum nigrym, and, to a lesser extent, Linnaea borealis and Vaccinium v~tls-idaea. In the sites observed, none of the low shrubs were in great abundance or had high cover values. Major herbaceous plants were Epilobium angustifolium, grasses, Equisetum spp. and Pyrola spp. Herbaceous cover rarely exceeded 10%. Other herbs were present in lesser amounts. A much larger range of mosses and lichens were found i n  these intermediate sites than in the sites previously mentioned. The most important mos Rhacomitrium; many cover. Lichens of spp. and Cladonia  of litter ( u p  to 3 s genera were ~ol~trichum,   re pa no clad us and * others also contributed to total Bryophyte ' major importance were Stereocaulon spp., Peltigera spp.  Ground cover include'd varying percentages - - - 0%) and bare rock (up to 80%). - Well Developed Stands The sites with the heaviest growth had a much smaller percen- tage of exposed bare rock and attendant higher litter cover per- centages. The gravels in these sites were mixed with a higher percentage of soil-sized particles. Tree s p e c i e s  present on these sites paralleled those growing on the more intermediate stands. However, densities, average height and dbh measurements were substantially greater. White spruce, Picea glauca, also appeared to occur more regularly in these more developed sites. The composi t ion of tall shrubs was also similar to those of the more intermediate sites with some increases in ~ e r c e n t a e e s  of Viburnum e d u l e  and perhaps Rosa acicularis. The tA1es-t wiylows occurred on these sites with some exceeding 30' i n  height. Low shrub species composition was much the same as in the intermediate stands with apparent increases in the abundance of Ledurn palustre ssp. groenlHndicum and Vaccinium uliginosum. Grass species, especially Calamagrostis canadensis, and Epilobium angustifolium continued in these denser stands to be the major herbaceous groups present. Moss and lichen species composition showed perhaps the greatest change from that found in the intermediate stands. Stereocaulon, which was a dominant ground cover on less shaded sites, was rare on these sites and Peltigera and Cladonia species predominated. Hylocomium splendens, which was rare on more open sites, assumed a position of dominance among the moss species. This position of dominance was shared by the genus Drepanocladus. The abundance of Polytrichum did not appear to have changed much through the transition. Corlcluding Remarks At the present stage of analysis, the only definitive conclu- sion that can be m ~ d e  with respect to "causes" of vegetational pattern is that there is a positive correlation of percent fines with vegetative cover on a large scale. The patterns of vegetation on the mine tailings are extremely complex and undoubtedly are related to many interacting factors. Further analysis and data reduction may provide evidence of possible vegetation patterns (both large- and small-scale) which at this point are not obvious. There is no question but that establishment of most of the woody plant species common on disturbed sites, in interior Alaska have been successful on many sites on these 30-40 year old tailings. Judging by the age of some specimens, successful establishment occurred in some sites very soon after the tailings were deposited. Preliminary analysis, however, does not explain why apparently similar sites were not vegetated. The causes of such unconformi- ties remains to be determined. 

Natural revegetation of placer mined lands of interior Alaska II

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Natural revegetation of placer mined lands of interior Alaska II

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