Ivan Tůma

Effect of Manipulated Rainfall on Root Production and Plant Belowground Dry Mass of Different Grassland Ecosystems

A field experiment was established to quantify the effects of different amounts of rainfall on root growth and dry mass of belowground plant parts in three types of grassland ecosystems. Mountain (Nardus grassland), highland (wet Cirsium grassland), and lowland grassland (dry Festuca grassland) ecosystems were studied in 2006 and 2007. Roofs constructed above the canopy of grass stands and gravity irrigation systems simulated three climate scenarios: (1) rainfall reduced by 50%, (2) rainfall enhanced by 50%, and (3) the full natural rainfall of the current growing season. Experimentally reduced amounts of precipitation significantly affected both yearly root increments and total root dry mass in the highland grassland. Dry conditions in 2007 resulted in considerable reduction of total belowground dry mass in highland and mountain grasslands. Although not all differences in root biomass of studied grasslands were statistically significantly, some also showed a decrease in root increment and in the amount of belowground dry mass in dry conditions.

Interannual Variation in Root Production in Grasslands Affected by Artificially Modified Amount of Rainfall

The effect of different amounts of rainfall on the below-ground plant biomass was studied in three grassland ecosystems. Responses of the lowland (dry Festuca grassland), highland (wet Cirsium grassland), and mountain (Nardus grassland) grasslands were studied during five years (2006–2010). A field experiment based on rainout shelters and gravity irrigation simulated three climate scenarios: rainfall reduced by 50% (dry), rainfall increased by 50% (wet), and the natural rainfall of the current growing season (ambient). The interannual variation in root increment and total below-ground biomass reflected the experimentally manipulated amount of precipitation and also the amount of current rainfall of individual years. The effect of year on these below-ground parameters was found significant in all studied grasslands. In comparison with dry Festuca grassland, better adapted to drought, submontane wet Cirsium grassland was more sensitive to the different water inputs forming rather lower amount of below-ground plant matter at reduced precipitation.

The effect of enhanced nitrogen on aboveground biomass allocation and nutrient resorption in the fern Athyrium distentifolium

We measured aboveground biomass allocation and resorption of nitrogen (N) and phosphorus (P) in the fronds of a winter-deciduous fern Athyrium distentifolium in ambient and N-enhanced treatments. Studies were done in the Moravian-Silesian Beskydy Mts. (Czech Republic) during 2007 and 2008. Athyrium distentifolium formed taller fronds and petioles and allocated more biomass to supporting tissue relative to photosynthetically active leaf tissue in response to N addition. Resorption of P from green fronds was more efficient than N resorption (on average 50% P, 21% N from supporting and 44% P, 24% N from photosynthetic tissues were withdrawn during senescence). The N/P-ratios were higher in photosynthetic tissue (10.8 in 2007 and 13.0 in 2008) in comparison with supporting tissue (5.5 and 7.7, respectively). In N-enhanced treatment, a positive relationship was found between the amount of supporting tissue relative to photosynthetic tissue and resorption of nutrients from photosynthetic tissue. However, higher N availability resulted in a significant decrease of N resorption efficiency in photosynthetic tissue of A. distentifolium.

Proportion of Root Production in Several Temperate Grasslands of Central Europe

Abstract Variability in frnpp, defined as the fraction of root net primary productivity (RNPP) to total net primary productivity (TNPP) [above-ground net primary productivity (ANPP) + RNPP] were examined through synthesis of 40 samples from available field biomass data assessed by in-growth core and obtained at 13 grassland sites situated in different altitudes in the Czech and Slovak Republics. Results indicate that frnpp varied from 0.05 to 0.59 across the compared sites. Submontane wet meadows had larger frnpp and dry lowland grasslands had smaller frnpp However, extreme conditions of mountain sites were reflected in a decrease of frnpp. Thus the relationship between values of frnpp at different sites and altitudes was indicated by quadratic regression with the highest frnpp coefficients in middle altitudes, where there were sufficient amounts of precipitation together with not so extremely cold temperatures. Results also indicate a high variability in frnpp at a regional scale and along increasing altitude. These data show how important and different roles grasslands can play in accumulation and turnover of root biomass.