Soil Characteristics in Relation to the Occurrence and Growth of Black Spruce

Black spruce (Picea mariana) Is one of the valuable pulpwbod species of northern Michigan as well as many sections of the northeastern United States. Nevertheless very little specific Information on the occurrence and growth of this species exists. It is listed as a component of seven forest types in the forest type classification recently published by the Society of American Foresters. With few exceptions the sites occupied by these seven forest types are described as poorly drained, swampy, moist to wet muck, and peat with little or no drainage, or low-lying flats, Indicating that the habitat of black spruce is a wet site. This might lead to the belief that this species is well adapted to such sites although ecologists recognize that plants are often forced to occupy adverse sites merely because they are not able to compete on the more favorable sites with more aggressive species. This appears to be true in the case of black spruce. In a comprehensive study of various phases of the management of black spruce carried on in the upper peninsula of Michigan, some data were secured on the occurrence and growth of black spruce in relation to certain soil characteristics. These data are not completely analyzed, therefore, the material presented here suggests only tentative conclusions. Several representative soils are included here, these being used to illustrate the influence of certain soil characteristics on the occurrence and growth of black spruce. In addition to the information on black spruce, there are shown in the accompanying figure, the percentage representation of the species most abundant in the stand composition (except in those cases where black spruce is the predominant species in which case the species being second in abundance is shown), the percentage representation of northern white cedar (Thuja occidentalis) (this being shown to determine whether its occurrence had any relation to soil acidity), and the total number of species represented on each soil or group of soils. Two broad groups of soils are shown, mineral soils and organic soils. The percentage representation of the various species Is based on the number of trees one Inch and over in diameter at breast height. The data on growth of black spruce showing growth both in height and diameter are based on trees In the dominant crown class. Such trees have had optimum conditions for growth throughout life. In comparing the mineral with the organic soils, lt should be noted that the former, in general, support a greater variety of species, the number varying from 10 to 19 on the mineral soils, the average being 14, while the organic soils support from 6 to 11 species, the average being 8. The quantity of black spruce on the mineral soils varies from 3.2 to 55.3 P cent of the total number of trees. Black spruce is most abundant on the wetter soils, namely Bruce fine sandy loam, Munuscong fine sandy loam and Saugatuck sand, where it makes up approximately 50 per cent of the number of stems in the stand. The drier mineral soils represented by Emmet stony loamy sand and several well drained sandy loams support very little black spruce, the representation of this species varying from 3.3 to 4.1 per cent. Even the Ontonagon silty clay and clay loama which are highly retentive of soil moisture support only a limited quantity of black spruce, actually 15.3 per cent of the stand. However, when considered in light of the fact that 19 species are represented on these soils, the black spruce is well represented. On all of the mineral soils, balsam fir (Abies balaamea) is a prominent species,~eTEh"eT~b"eTngthe most abundant or second in abundance. It is most abundant on the better drained soils where it makes up 34.0 to 42.8 per cent of the number of stems. On the other hand, lt is represented in limited quantity on the poorly drained Bruce fine sandy loam, Munuscong fine sandy loam and Saugatuck sand. The general occurrence of balsam fir on a variety of mineral soils is not unexpected since this species was found in limited quantity on all of the 25 soils studied upon which the northern hardwood forest occurred. With the exception of Emmet stony loamy sand the soils upon which black spruce is least abundantly represented produce the most rapid growth both In height and diameter. The poor growth on Emmet stony loamy sand is probably due to excessive stoniness of the soil, this relationship having been, reported upon previously. Both height and diameter