Browsing by Subject "Ecuador"

Now showing 1 - 2 of 2

Untersuchungen zur räumlichen Heterogenität von Kronenstruktur und Bestandesniederschlag in einem tropischen Bergregenwald
(2008) Oesker, Mathias; Küppers, Manfred
The objective of this study was to investigate the distribution and heterogeneity of canopy structure and precipitation throughfall and related with this the factors light, water, and nutrient input. Further to appraise the consequences of this heterogeneity as a factor, which forms ecological niches. The study took place in a tropical mountain rain forest in southern Ecuador, specifically in the Reserva San Francisco located north of the Podocarpus National Park. The area of research covered the altitudinal range from 1950 m a.s.l. to 2275 m a.s.l. Nine plots of 400 m2 (20 m by 20 m) were set up in three forest types, which differed in tree species composition (HOMEIER 2004). Two forest types were located on a ridge and one was in a gorge at the same elevation as the lower ridge forest type. In each forest type three representative plots were chosen and a total of 31 study points were defined. At each point throughfall was collected during a one-year period. In all throughfall samples the following parameters were determined: Volume, pH, electrical conductivity, concentration of K, Mg and Ca, nitrate, ammonium, organic nitrogen, phosphate, P, Mn, Cu, Rb, Sr and Pb. The canopy structure was determined at all points with both structural measurements and hemispherical photography over a period of three years. Lab experiments with a representative selection of tree species were performed in order to determine leaf surface water storage capacity and nutrient leaching out of leaves. For determination of canopy structure hemispherical photography turned out to be a particularly efficient method. The software HemiView (DeltaT) was used to calculate important information such as canopy openness, light environment and LAI. A high spatial heterogeneity with a coefficient of variation (CV) of 59 % was found for all parameters. It was higher than the temporal variability over three years (CV 12 %). The throughfall was most heterogeneous within the investigated parameter with a CV of 64 %. In total close to 82 % (between 0.5 % and 492 % and a CV 29 %) of the volume of the incident precipitation could be collected as throughfall in the forest. With this throughfall 49.1 kg ha-1 a-1 K, 3.7 kg ha-1 a-1 Mg and 8.7 kg ha-1 a-1 Ca (mean values) were transported. During low intensity rain events the proportion of throughfall, expressed as percentage of incident throughfall was significantly lower than the annual mean of the incident precipitation. For high rain intensities no differences were found. With a geostatistical approach to investigate the spatial distribution of the throughfall no clear results could be calculated because the three replicates diverged strongly from each other. Canopy structure and its species composition was influenced by the distribution of throughfall. Related to the amount of throughfall it could be shown that with an open canopy up to 100 % of the incident precipitation could be collected. Underneath a closed canopy, in average less throughfall was collected. However, the volume of throughfall showed high spatial distribution and heterogeneity with even more than 100 % of incident precipitation. Nevertheless, throughfall volume can be predicted using the parameters radiation and canopy openness at a zenith angle of 36°. Average water storage capacity of leaf surfaces from eleven most common tree species resulted in 74.74 ml m-2 leaf area. In a dry canopy with a theoretical equal distribution of precipitation and a given LAI this value equals 0.38 mm of rain. The nutrient leaching out of leaves is species dependent and differs statistically. Those lab results can be extrapolated to the entire forest: Including the water storage capacity and the number of rain events, a maximum leaching capacity of 220 kg ha-1 a-1 K, 14 kg ha-1 a-1 Mg and 67 kg ha-1 a-1 Ca can be calculated. The main focus of this study was to investigate heterogeneity of abiotic factors and its ecological consequences. In the forest type with the most heterogeneous canopy structure and the most heterogeneous distribution of throughfall amounts were found. Lowest heterogeneity of spatial distribution of throughfall element contents was found in forest type with the lowest tree species diversity. The higher the tree species diversity the more heterogeneously scattered is the element content in the throughfall.
Vergleichende Betrachtung von Mikroklima, Struktur und aus dem Xylemsaftfluss von Bäumen hochskalierter Transpiration eines tropisch-montanen Regenwaldes und eines Wolkenwaldes in Südost-Ecuador
(2010) Ohlemacher, Christian; Küppers, Manfred
In a tropical montane rain forest 1990 m a.s.l. and a cloud forest 2240 m a.s.l. in the Andes of Southeast Ecuador, tree stand structure (tree height, tree basal area, tree sapwood area, tree crown ground projection area and leaf area index (LAI)) was registered and the sap flow rate of trees, the microclimate (photosynthetically active radiation, temperature, air moisture) inside and above the canopy, and short term stem radius changes were measured. The period of measurement was one year, and synchronous measurements exist from 7 months. To investigate, whether the stand conductance for water differs between the two sites, their stand structure, xylem sap flow and microclimate were compared. Annual stand transpiration was calculated by means of upscaling the xylem sap flow, under inclusion of the site specific microclimate, with the basal area as scaling parameter. Mean radial stem growth was derived from stem radius changes. Radial stem growth is higher in the montane rain forest than in the cloud forest by a factor 3-5. No clear hints were found for different conductivity of trees between the investigated stands. The lower annual stand transpiration of the higher sited cloud forest (238 mm/a^-1) than that of the lower sited montane rain forest (438 mm/a^-1) is caused by a lower stand and foliage density (LAI = 1,6 in the cloud forest vs. LAI = 3,7 in the montane rain forest) and the higher air moisture at the higher sited stand. The crown area-related sap flow rate of single trees is approximately equal at both stands.