Heikki Veijalainen

Kasvuhäiriöistä ja niiden syistä metsäojitusalueilla

Veijalainen H. Kasvuhäiriöistä ja niiden syistä metsäojitusalueilla.

Tiivistelmä

During the last five years a number of foresters and research workers in Finland have noticed the increasing occurrence of a growth distur-bance in 10—15 year old peatland stands. This phenomenon is referred to as "eskimosis" in this paper. The symptoms do not resemble those of any of the known nutrient deficiencies and as far as we know it does not appear to be caused by insects or fungi. The symptoms of eskimosis in Pinus silvestris are as follows; — young samplings have long branches — apical dominance is lost — lammas growth is common — terminal shoots may become branched — needle lenghts vary within wide limits — elongation growth is suppressed — dark green colouring and sturdy external appearance of saplings Apparently 1—2 years after these almost invisible symptoms first appear, eskimosis kills the apical parts of the "infected"" trees, usually from one to three whorls, during late winter (die back). Some trees develop 2—3 leaders without any additional symptoms, but usually eskimosis is repeated year after year causing cessation of height growth, giving the tree a flat-topped appearance with plenty of dead needles distributed throughout all parts of the trees. At this stage of eskimosis, resination of the buds, necrotic spots on the needles and browning inside the shoots proceeding from the apical parts, are typical secondary symptoms. After some years the cambial growth may also be suppressed as a result of the decreased amount of green needles. Eskimosis results in thick-stemmed and stunted trees which very often die. An investigation programme has been started by the Department of Peatland Forestry, the Finnish Forest Research Institute, and some preliminary results are published in this paper. Eskimosis may infect pines, spruces and birches on drained peatlands as well as on mineral soils. Phosphorus fertilization often increases the likelihood of eskimosis developing. The first attempt to cure eskimosis, was carried out in a drained spruce stand, by fertilizing with micro-and macro-nutrients. The greatest increase in radial growth was achieved with NP fertilization, although the spruces survived even without any fertilization. Boron had a slightly positive effect on visible symptoms. Eskimosis was apparently caused by P-rich litter from the previously felled pine stand which had been fertilized with phosphorus some years prior to felling. The young spruce stand lost its shelter stand and subsequently received much easily soluble phosphorus from the P-rich litter. The largest known eskimosis area lies at Kivi-suo Experimental Fields, Leivonmäki, in pine plantations established in 1959. Kivisuo, Exp. 1^ lay-out, 4x4x4 NPKwith two replications, planting spacing 2 m, ditch spacing 22 m, earlier used as a drying field for hydro peat, originally an open Sphagnum bog with rimpis, fertilization in 1959, refertilization 1968. During refertilization, the plots were divided into three parts; a = broadcast fertilization, PK(0-17-15) 500 kg/ha b =spot fertilization. PK(0-17-15) 50 g/ sq.m c = control A couple of years after refertilization was carried out, eskimosis appeared. It seems that eskimosis is largely a result of the original micro-relief of the bog and is further increased by the highest P and K levels (eg. Huikari and Paarlahti, 1973). Another investigation was carried out in 1975 with the following results: the elongation growth of the trees was decreased most on plots which received broadcast refertilization and least on the control plots (Fig. 1.). The situation was about the same in Experiment V which was spot fertilized in 1959 (spot size 0,25 sq.m) and refertilized in 1966 in a similar way as exp. 1. Eskimosis also appeared soon after refertilization. A decrease in tree heights induced by eskimosis was observed (Fig- 2). Experiments under greenhouse conditions using substrate taken from sites where eskimosis is prevalent have shown that this Scheuchzeria-rich peat is deficient in N, K and B even after previous site treatments with NPK and PK at high levels. This may be the solution to the problem at Kivisuo. It will require perhaps another 2—3 years to confirm this before our micronutrient experiments will provide us with the final details. "

Vastaanotettu 31.10.2017 Julkaistu 1.1.1975

Katselukerrat 1114

Saatavilla http://suo.fi/article/9447 | Lataa PDF