Mountain Spruce Forest Research Articles

Spacial distribution of photosynthetic capacity and performance in a mountain spruce forest of northern Germany : II. Climatic Control of Carbon Dioxide Uptake.

Net photosynthesis of Picea abies was measured in a spruce forest in northern Germany with temperature- and humidity-controlled cuvettes in 4 different crown layers on shoots of different ages. These measurments were performed such that temperature and humidity either followed ambient conditions or were kept constant. Annual courses of light-, temperature-, and humidity-related net photosynthesis were determined. Spruce had a remarkably constant rate of CO2 uptake from April to September for 1-year and older needles. Light saturation was achieved at 25 klx. Current year needles had the highest rates of CO2 uptake in early summer, but these rates decreased by autumn. Photosynthetic capacity decreased with needle age and, on a dry weight basis, it was higher in the shade than in the sun crown. The temperature optimum was between 13 and 23° C. Photosynthesis in spruce decreased when air humidity was low.The effect of the natural weather conditions on photosynthetic capacity was determined. The habitat is characterized by a high frequency of low light intensities (75% of total daytime below 20 klx) and cool temperatures (80% of daytime between 9 and 21° C). Low air humidity was only present when light intensities were high. The major limiting factor for production was low light intensities, which reduced photosynthetic capacity in the sun crown to 42% below maximum possible rates. Adverse temperatures reduced CO2 uptake by 28% and large water vapor pressure deficits reduced rates by only 2% compared with maximum possible rates. The limited adaptation to light is discussed.

Spacial distribution of photosynthetic capacity and performance in a mountain spruce forest of Northern Germany

Biomass distribution and diurnal CO2 uptake under natural conditions were investigated on Picea abies in a mountainous climate (Solling, Northwest Germany). Spruce has a remarkable variability in leaf characteristics. Even on a single branch in the lower sun crown, needle dry weight and surface area change considerably from the branch base to the tip and accoring to exposure. Only about 18% of the total biomass of the tree was current year's growth, about 40% of the needles were 4 years and older reaching a maximal age of 12 years. The main growing zone was at the border of upper shade and lower sun crown and the main accumulation of dry weight was at a greater tree height than was observed for maximal growth of needle numbers or surface area. The annual, new growth shifted toward the upper sun crown. Maximal daily CO2 uptake was highest in the lower sun crown on days with variable cloud cover when temperatures were moderate and water vapor pressure deficits were low. Also the annual CO2 uptake was highest in the lower sun crown, where 4-year-old and older needles contributed about 35% to the annual CO2 uptake of the tree. Current year growth contributed about 15% of the total CO2 gain. The upper and lower sun crowns produce about 70% of the total carbon gain. The carbon balance of spruce and the distribution of the production process in relation to needle age and crown level are discussed.

Untersuchungen über Stickstoff-Blattspiegelwerte einiger Bodenpflanzen naturnaher Berg-Fichtenwälder: Standorts- und Vegetationsbeziehungen

Summary The plants in the field layer of natural mountain spruce forests studied are all characterized by high nitrogen leaf levels. Apart from species-typical distinctions site conditions and vegetation structure produce the differentiation in the nitrogen and mineral matter content of leaves. Available mineral nitrogen in the upper organic soil horizons and the ecological conditions of biosynthetic utilization determine essentially the values of nitrogen and protein content in leaves and the biomass as final product. The conditions of competition may modify vigorously the nitrogen content of the dominating plants Calamagrostis villosa and Vaccinium myrtillus . These findings coincide to a large extent with experimental results on protein and biomass depression caused by competition stress. The investigations are concluded by a discussion of the relations between nitrogen leaf level and site factors as well as syngeographical differentiation of Hercynian-Sudetian mountain spruce forests.

Untersuchungen über Stickstoff-Blattspiegelwerte einiger Bodenpflanzen naturnaher Berg-Fichtenwälder: Saisonale Veränderungen und artspezifische Relationen

The content of nitrogen, protein and mineral matter in leaves and stems of important plants in the field layer of natural mountain spruce forests (Harz, Erzgebirge) is overthrown by a vigorous dynamic during vegetation period, the regularity of which is remaining throughout the single years. Additionally to this generell equidirectional tendency of all plants studied species- and site-typical particularities can be observed, showing close relations to their growth forms and to their ecological amplitude and valency. The nitrogen-protein-equivalents are remarkably constant. Plants of oligotrophic sites (Vaccinium vitis-idaea, Vaccinium myrtillus) may produce much protein with relativ lower nitrogen leaf levels, whereas plants of mesotrophic sites (Calamagrostis villosa, Trientalis europaea) require a higher nitrogen leaf level for the same protein content. The relation between nitrogen and protein content in leaves may be described by a linear regression model. The parameters however are more or less attributed to the plant species. The same species resp. populations moreover show temporal (annual) variations of parameters, correlating with weather factors. The plant specific relations are treated and the different gradations resulting from them are correlated with the phytosociological behaviour of the species on the same ecological conditions. Finally the ecological relevance of high nitrogen and protein content in leaves of the plants studied is discussed.