Long-term decomposition process of leaf litter from Quercus pyrenaica forests across a rainfall gradient (Spanish central system) A Martin, Jf Gallardo, I Santa Regina To cite this version: A Martin, Jf Gallardo, I Santa Regina. Long-term decomposition process of leaf litter from Quercus pyrenaica forests across a rainfall gradient (Spanish central system). Annales des sciences forestières, INRA/EDP Sciences, 1997, 54 (2), pp.191-202. hal-00883141 HAL Id: hal-00883141 https://hal.archives-ouvertes.fr/hal-00883141 Submitted on 1 Jan 1997 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Original article Long-term decomposition process of leaf litter from Quercus pyrenaica forests across a rainfall gradient (Spanish central system) A Martin JF Gallardo2 I Santa Regina 1 Area de Edafología, Facultad de Farmacia, Universidad de Salamanca, 37080 Salamanca; 2 CSIC, Aptado 257, 37071 Salamanca, Spain (Received 30 November 1995; accepted 1 April 1996) Summary - A long-term (3 years) study has been made of the leaf-litter decomposition process in four forest ecosystems across a rainfall gradient. The soil organic contents comply with the factor of rainfall, but this does not appear to affect the complete decomposition process decisively, since the limiting factor is soil humidity. The rainfall distribution is similar for all the plots studied and the main differences are seen essentially in the amount of water received during the wet season (in each case with sufficient humidity for leaf decomposition to progress). Thus, leaf-litter decay is linked to the maintenance of soil humidity, mineralization slowing down when the soil dries out, and the effects of climate therefore predominating over the chemical characteristics of the material in the regulation of the decomposition process (at least at short term). In this sense, the summer drought is the most unfavourable environmental factor in this type of climate. In advanced stages of decay the rate of weight loss becomes relatively independent of climate. The decomposition rates obtained by the litterbag pro- cedure are lower than those calculated by litter production and permanent litter; the reason for these differences is probably the limitation of the mesofaune activity in the litterbags. Leaf decomposition constants ranged from 0.33 on the plot with the highest rainfall to 0.47 (on the driest plot), corre- sponding to mean residence times of 2.0 to 1.1 years, respectively. However, each bioelement has a different residence time. leaf-litter decomposition / forest ecosystems / Quercus pyrellaica forests / Mediterranean climate / litter quality / litterbag methods Résumé - Processus de décomposition à long terme des litières de chênaies à Quercus pyre- naica suivant un transect pluviométrique. On a étudié le processus de décomposition à longue terme (3 années) des feuilles de quatre chênaies à Quercus pyrenaica qui suivent un transect plu- viométrique. Les contenus de matière organique des sols forestiers sont liés au facteur pluviométrique, mais la pluviométrie n’affecte pas de manière significative le processus de décomposition des feuilles * Correspondence and reprints du chêne, car ce processus est plutôt affecté par l’humidité du sol. Cette distribution des pluies est simi- laire dans tous les sols forestiers, mais la différence de la quantité de pluie se manifeste en hiver, c’est- à-dire quand les sols sont humides. La décomposition est liée à l’humidité du sol, et elle est arrêtée quand le sol est sec. Ainsi l’effet du climat est plus important que la composition chimique à court terme; à long terme, l’importance du climat diminue. La constante de décomposition des feuilles obte- nue par la méthode de « litter-bag » est plus basse que celle calculée à partir des donnés de produc- tion des litières et de la teneur en litière permanente, ce qui est dû à la limitation de l’activité de la méso- faune dans les « litter-bags ». Les constantes de décomposition varient de 0,33, dans la station la plus pluvieuse, à 0,47, dans la station la plus sèche. Les temps de résidence varient de 2,0 à 1,1 années, res- pectivement. Il faut tenir compte du fait que chaque bioélément a son propre temps de résidence. décomposition des litières / écosystèmes forestiers / Quercus pyrenaica / climat méditerranéen / qualité de la litière / méthode « litter-bag » INTRODUCTION The release of bioelements depends on the decomposition of organic matter and is to loss. In any forest ecosystem, both deciduous and generally proportional weight Many factors are involved in the release of evergreen, the litter fall is reflected each bioele- ments. It should be stressed that from year in the massive appearance of dead apart the intrinsic factors of the such as the organic matter that accumulates on the litter, ground (Mangenot and Toutain, 1980). base content (Eijsackers and Zehnder, 1990), Together with the contribution from the nitrogen (Berg and Staaf, 1980), polyphe- nols et decay of roots (McClaugherty et al, 1982), (Domínguez al, 1988), lignin (Melillo or tannins the litter on the surface of the soil represents et al, 1989), (Davies et al, 1960), there are external factors that also affect the the main source of energy, carbon, nitrogen and phosphorus for the soil microflora and decomposition rate; among these, of note are climate aera- mesofauna (Ranger et al, 1995) and also (temperature, humidity, tion, actual provides an amount of nutrients that can evapotranspiration (AET); Berg become readily available and be reused by et al, 1990; Dyer et al, 1990), soil charac- the plant covering (Rapp and Leonardi, teristics (pH, base content; Kononova, 1966; 1988). Toutain, 1981) and soil organisms (Aranda et al, 1990; Kögel-Knabner et al, 1990; Joer- It is customary to define two or three gensen, 1991). phases in the transfer of nutrients to the soil: In an ecosystem in the total in the first, soluble compounds are released equilibrium, mass of the contributions is compensated by leaching; this is a rapid phase that by the loss of an mass of litter; if this depends on the initial nutrient content (Berg equal were not so, elements would be accumu- and Staaf, 1977). In the second phase, ener- lated and retained the rise to getic compounds like cellulose and hemi- by litter, giving a progressive decrease in productivity (Jenny cellulose are decomposed after immediately et and that phase, thus making evident the degra- al, 1949; Mangenot Toutain, 1980). an essential in forest dation of the biological material. The third Accordingly, problem is to information about the which is much slower, affects ecology gain phase, laws the transformation of molecules with bonds more resistant to governing organic matter so that an excessive down degradation; this phase is carried out by soil slowing can be avoided. organisms, essentially saprophytes (bacteria of biogeochemical cycles and fungi), and depends on the lignin content Losses of organic matter due to the loss (Berg and Staaf, 1987). of carbon dioxide and leachates derived from decomposition are also important to Genista falcata) and spiny rosaceae (Rubus consider, especially in managed woodlands ulmifolius, Crataegus monogyna). In the (Howard and Howard, 1974). herbaceous stratum there is a predominance of (Festuca sp, Dactilys The aim of the present work was thus to gramineae glom- erata), at determine, in a long-term (3 years) study, leguminosae only appearing the factors governing the decay of leaf litter Fuenteguinaldo (Trifolium sp, Ornithopus As rainfall increases, the of in the different phases of the process and to sp). presence ferns (Pteridium and. in forest compare different methods and calculations aquilinum) of heathers (Erica Calluna to estimate decomposition rates. clearings, sp, vulgaris) increases. In all cases, the soils are Cambisols (gen- DESCRIPTION OF STUDY AREA erally humic) developed over slates and greywackes at Navasfrías and Villasrubias and over Ca-alkaline at El and Four experimental plots in Quercus pyre- granite Payo (Gallardo et al, naica forests across a rainfall gradient were Fuenteguinaldo 1980). chosen. The plots are situated in the munic- ipalities of Navasfrías, El Payo, Villasru- bias and Fuenteguinaldo in the region known METHODS as El Rebollar on the northern face of the To follow the of leaf-litter Sierra de Gata Mountains (southwest of the dynamics decompo- sition on the soil, 54 nylon litterbags with a sur- of Salamanca). province face area of2 4 dmwere placed on each plot. The a mesh of 1 mm were dis- The climate of the zone features rainy bags had pore and tributed in three of 18 distributed winters and warm summers and may be groups bags according to the topography (Martin, 1992). Each classified as Mediterranean temperate (Elías litterbag contained 10 g of recently fallen leaves. and The summer deficit in rain- Ruiz, 1977). previously dried at room temperature, from the fall (189 mm yr-1) is lower at Navasfrías, same stand. The bags were placed on the soil due to higher rainfall (1580 mm yr-1) and surface so that the conditions would be as close lower temperatures (annual mean, 10.4 °C). as possible to natural ones (Bocock, 1964). At Fuenteguinaldo the summer rainfall The experiment started in February 1990 (the deficit (259 mm yr-1) is significantly more leaves were taken on November 1989). One bag was from marked owing to higher temperatures withdrawn each group at approximately two monthly intervals until a sampling period of (12.9 °C) and lower rainfall (720 mm yr-1).