scholarly journals Change in hydraulic traits of Mediterranean Quercus ilex subjected to long-term throughfall exclusion

2010 ◽  
Vol 30 (8) ◽  
pp. 1026-1036 ◽  
Author(s):  
J.-M. Limousin ◽  
D. Longepierre ◽  
R. Huc ◽  
S. Rambal
Keyword(s):  
Quercus Ilex ◽  
Throughfall Exclusion

Mitigation of drought stress in forest stands - insights from a throughfall-exclusion and a thinning experiment

2020 ◽  
Author(s):  
Timo Gebhardt ◽  
Benjamin D. Hesse ◽  
Thorsten E.E. Grams ◽  
Christian Ammer ◽  
Karl-Heinz Häberle
Keyword(s):  
Drought Stress ◽  
Forest Management ◽  
Soil Water ◽  
Norway Spruce ◽  
Intraspecific Competition ◽  
Basal Area ◽  
Understorey Vegetation ◽  
Management Measures ◽  
Throughfall Exclusion

<p>Due to climate change suitable forest management measures are required to mitigate the proposed exacerbating drought events as already observed in central Europe in summer 2003, 2015, 2018, and 2019. This contribution summarizes the findings of two long-term field experiments studying different forest management measures aiming at mitigating drought in forest stands.</p><p>The first study investigated the potential of mixing tree composition for mitigating drought stress in Norway spruce (Picea abies [L.] Karst.). To this end, a five-year study with repeated summer droughts, experimentally induced via throughfall-exclusion (TE), was performed. The study objects were mature (60-80 years) old stands of Norway spruce in monoculture and mixture with European beech (Fagus sylvatica (L.). The impacts of repeated summer droughts were assessed on about 100 trees distributed on 12 plots and accessible via canopy crane (Kranzberg forest ROOF experiment in southern Germany). Predawn leaf water potentials of Norway spruce reached minima of -1.8 MPa, but were not affected by species mixture. Nevertheless, daily xylem sapflow density was increased up to 40% in mixture compared to pure strands. Likewise, stem growth, i.e. relative basal area increment, showed significantly higher drought resistance in mixture compared to monocultures.</p><p>While altering forest stand composition seems to be promising on the long-term, the conversion from monocultures is often economically not suitable for young stands in the short- to medium-term. Therefore, reducing intraspecific competition via thinning is a frequently discussed option investigated in the second, eight-year-long study. In a 26-year old Norway spruce monoculture, three thinning intensities, i.e. unchanged (control), moderate thinning (MT with reduced basal area by 43%) and heavy thinning (HT, reduced basal area by 67%) were applied, potentially mitigating drought by reducing intraspecific competition and increasing soil water availability. Indeed, in both thinning intensities the duration of drought stress for the trees (soil water content below critical value) was reduced compared to controls for up to 5-7 years following the event. However, increased radiation and higher growth rates of the individual trees accompanied by the fast establishment of a vital ground vegetation diminished the difference in stand transpiration between MT and HT within two years. Moreover, belowground competition with the understorey vegetation suppressed fine root recovery under HT compared to MT in contradiction to increased leaf area on HT on tree-level and therefore increased transpirational demand.</p><p>The presented studies suggest admixing of broadleaved beech into monocultures of Norway spruce to be a promising management measure in the long-term. In juvenile monocultures of Norway spruce frequent and intense thinning interventions while preventing the establishment of a vital understorey vegetation appears to be a promising forest measure, mitigating drought without losing sight of economic needs.</p>

Modelling rainfall interception in a mediterranean Quercus ilex ecosystem: Lesson from a throughfall exclusion experiment

2008 ◽  
Vol 357 (1-2) ◽  
pp. 57-66 ◽  
Author(s):  
Jean-Marc Limousin ◽  
Serge Rambal ◽  
Jean-Marc Ourcival ◽  
Richard Joffre
Keyword(s):  
Quercus Ilex ◽  
Rainfall Interception ◽  
Exclusion Experiment ◽  
Throughfall Exclusion

scholarly journals Change in hydraulic properties and leaf traits in a tall rainforest tree species subjected to long-term throughfall exclusion in the perhumid tropics

2011 ◽  
Vol 8 (8) ◽  
pp. 2179-2194 ◽  
Author(s):  
B. Schuldt ◽  
C. Leuschner ◽  
V. Horna ◽  
G. Moser ◽  
M. Köhler ◽  
...  
Keyword(s):  
Tree Species ◽  
Large Scale ◽  
Stem Diameter ◽  
Soil Drought ◽  
Diameter Growth ◽  
The Sun ◽  
Exclusion Experiment ◽  
Throughfall Exclusion ◽  
Stem Diameter Growth

Abstract. A large-scale replicated throughfall exclusion experiment was conducted in a pre-montane perhumid rainforest in Sulawesi (Indonesia) exposing the trees for two years to pronounced soil desiccation. The lack of regularly occurring dry periods and shallow rooting patterns distinguish this experiment from similar experiments conducted in the Amazonian rainforest. We tested the hypotheses that a tree's sun canopy is more affected by soil drought than its shade crown, making tall trees particularly vulnerable even under a perhumid climate, and that extended drought periods stimulate an acclimation in the hydraulic system of the sun canopy. In the abundant and tall tree species Castanopsis acuminatissima (Fagaceae), we compared 31 morphological, anatomical, hydraulic and chemical variables of leaves, branches and the stem together with stem diameter growth between drought and control plots. There was no evidence of canopy dieback. However, the drought treatment led to a 30 % reduction in sapwood-specific hydraulic conductivity of sun canopy branches, possibly caused by the formation of smaller vessels and/or vessel filling by tyloses. Drought caused an increase in leaf size, but a decrease in leaf number, and a reduction in foliar calcium content. The δ13C and δ18O signatures of sun canopy leaves gave no indication of a permanent down-regulation of stomatal conductance during the drought, indicating that pre-senescent leaf shedding may have improved the water status of the remaining leaves. Annual stem diameter growth decreased during the drought, while the density of wood in the recently produced xylem increased in both the stem and sun canopy branches (marginally significant). The sun canopy showed a more pronounced drought response than the shade crown indicating that tall trees with a large sun canopy are more vulnerable to drought stress. We conclude that the extended drought prompted a number of medium- to long-term responses in the leaves, branches and the trunk, which may have reduced drought susceptibility. However, unlike a natural drought, our drought simulation experiment was carried out under conditions of high humidity, which may have dampened drought induced damages.

Response of foliar metabolism in mature trees of Quercus pubescens and Quercus ilex to long-term elevated CO2

1998 ◽  
Vol 39 (3) ◽  
pp. 233-245 ◽  
Author(s):  
Roberto Tognetti ◽  
Jon D Johnson ◽  
Marco Michelozzi ◽  
Antonio Raschi
Keyword(s):  
Elevated Co2 ◽  
Quercus Ilex ◽  
Mature Trees ◽  
Quercus Pubescens
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