Stem Biomass Production Research Articles

Inherited narrow crown form, harvest index and stem biomass production in Norway spruce, Picea abies.

The effect of crown form on stem biomass production was investigated in an 18-19-year-old Norway spruce stand (Picea abies (L.) Karst.). The harvest index was 0.271 in pendula trees, which have a heritable narrow crown form, and 0.235 in normal-crowned trees and the dry weights of stem biomass were 2.57 kg and 3.37 kg, respectively. However, the production of stem biomass per crown projected area was more than twice as much in pendula trees as in normal-crowned trees. Results indicate that the crown form of pendula spruce is less plastic than that of normal-crowned spruce suggesting that such trees might maintain a high stemwood yield per unit ground area with increasing stand density. Because pendula spruce has a higher harvest index and a less flexible crown than normal-crowned spruce, it might be useful for crop tree ideotype breeding.

Season of Cutting Affects Biomass Production by Coppicing Browse Species of the Brazilian Caatinga

This paper reports the effect of season of cutting on coppice biomass production by S tree species common in the semiarid caatinga woodlands of northeast Brazil. Trees were cut early and late in the wet and dry seasons and coppice biomass production was monitored for 2 growing seasons after cutting. No mortality occurred as a result of cutting in any season. The effect of season of cutting on subsequent coppice production was most pronounced in the first year but differences persisted into the second year. Production by trees cut late in the wet season lagged behind that of trees cut at any other time. This was true for all species except marmeliero (Croton hemiargyreus Muell. Arg.) during both years. Pau branco (Auxemma oncocalyx Taub.) production was maximized by cutting late in the dry season. Jurema preta (Mimosa acutistipula Benth.) and catingueira (Caesalpinia pyramidalis Tul.) production was maximized by cutting early in the dry season. The season of cutting does not affect marmeliero stem production. Except for the late wet season, no treatment significantly affected sabia Mimosa caesalpinifolia production. Stem biomass production is affected more by season of cut than is leaf biomass production. The different patterns of response among these species could be the basis of a selective cutting scheme to achieve objectives such as browse and wood production.

Organic Matter Production and Distribution in Slash Pine (Pinus Elliottii) Plantations

The production and accumulation of total system organic matter (to 100 cm soil depth) in plantations of slash pine were analyzed using three replications of stands 2, 5, 8, 14, 18, 26, and 34 yr old. Maximum leaf area occurred at 5 yr. After this point aboveground net primary production (NPP) continued to increase to a maximum at 26 yr and then declined. After 5 yr stem biomass production composed a constant 50% of NPP. The forest floor increased at a constant rate through 34 yr, although total detritus (forest floor plus soil organic matter) was relatively constant at m160 Mg/ha. Live vegetation mass was less than detritus mass until =m25 yr, the current harvest rotation length. Total system organic matter showed no indication of a decline after site preparation, and was still increasing at 34 yr (340 Mg/ha). During site preparation -30 Mg/ha organic matter were lost through burning and decomposition. This loss was small enough to be completely offset by increases in live vegetation and forest floor over -3 yr following site preparation, which may be important in limiting losses of nutrients from these sites after a disturbance. rently 5.2 x 106 ha of commercial slash pine (Pinus elliottii var. elliottii), with -40% of the total in north- ern Florida. Fifty-two percent of the total is in plan- tations, representing 14% of the forested land area in Florida, and the rest is in naturally regenerated second growth (Scheffield et al. 1981); the proportion in plan- tations is rapidly increasing. Although the conversion of the natural stands to plantations amounts to landscape modification at a tre- mendous scale, we have little idea of the ecological consequences. Delcourt and Harris (1980) proposed