Phosphorus cycling in primary and secondary seasonally dry tropical forests in Mexico

Abstract

Abstract• Primary forests in the seasonally dry tropical regions of Mexico are disappearing under land-use pressure, creating a mosaic of secondary forests of different ages.• In this study we measured the aboveground litterfall phosphorus (P) fluxes, litter-layer and soil P pools to compare the P cycles in primary and secondary seasonally dry tropical forests. Our hypothesis was that the previous agricultural land use of secondary forests would bring about a lower P flux in the litterfall, lower soil P pool, and higher nutrient resorption proficiency than in primary forests, as well as an increase of relative amounts of available P provided by the soil with forest aging.• The expected litterfall P flux increase in the secondary forest following a previous agricultural land use did not occur. Phosphorus return to the soil by aboveground litterfall was unaffected by the succession stage of the forest. In addition, the total soil P pool did not change with forest age. However, available soil P (bicarbonate P-inorganic and P-organic pools) and hydroxide inorganic P pools were higher in primary than in secondary forest soils. Phosphorus concentration in litterfall increased significantly with forest age, suggesting that P is cycled more efficiently (by a higher nutrient resorption proficiency) when soil available P is less abundant. Despite these differences among forests, the results of our study gave evidence that P requirements by plants in primary and secondary forests are sufficiently met by the accumulation of dissolved (water extractable) P in the forest floor during the dry season and by soil bicarbonate-P pools.• Our study on the effects of land cover change on P cycling, following the discontinuation of agricultural practices, leads to the conclusion that this ecosystem P dynamics will vary depending on the successional stage of the forests, and is strongly influenced by the seasonal rainfall pattern which determines plant-available P. Mots-clés :litière / succession secondaire / disponibilité du phosphore / sols tropicaux Résumé -Cycle du phosphore dans les forêts primaires et secondaires tropicales à saison sèche du Mexique.• Les forêts primaires dans les régions tropicales à saison sèche du Mexique sont en train de disparaître sous la pression de l'utilisation agricole des terres, créant une mosaïque de forêts secondaires d'âges différents.• Dans cette étude, nous avons mesuré les flux de phosphore (P) de la litière au-dessus du sol, de l'horizon de litière et les pools de phosphore P du sol, pour comparer les cycles de P dans les forêts primaires et secondaires tropicales à saison sèche. Notre hypothèse est que l'exploitation agricole précédente des forêts secondaires devrait aboutir à un flux plus faible de P dans la litière, à un plus faible pool de P du sol, et à une résorption plus élevée des éléments nutritifs que dans les forêts primaires, ainsi qu'une augmentation des quantités relatives de P disponibles fournies par le sol avec le vieillissement de la forêt.• L'accroissement attendu du flux de ...

Trees increase their P:N ratio with size

“…Moreover, in certain situations the time‐scale of the ecosystem P cycle and of the successional process can be similar. An increase in nutrient cycling rates and losses occurs after disturbance and secondary succession, with early‐successional species substituting for late‐successional ones (Valdespino et al ., ). Forest disturbances such as fires frequently imply increases in the availability of P that are accompanied by the recruitment of early successional species, as observed in mediterranean (Escudey et al ., ; Yildiz et al ., ; Lane et al ., ; Turkmen & Duzenli, ), tropical (Hughes et al ., ; Kennard & Gholz, ; Ilstedt et al ., ; Blair, ), wet temperate (Saa et al ., , ; Michalzik & Martin, ) and cold forests (Lagerström et al ., ; Mitchell & Ruess, ).…”

Nutrient limitation reduces land carbon uptake in simulations with a model of combined carbon, nitrogen and phosphorus cycling

“…Low latitude systems are expected to show the highest direct CO 2 response of NPP (Hickler et al, 2008), and in climate change projections they are responsible for a substantial positive feedback between climate and the C cycle (Friedlingstein et al, 2006;Raddatz et al, 2007). At the same time, low latitude ecosystems are expected to be more P-limited (Townsend et al, 2011). Therefore, an inclusion of the terrestrial P cycle into global C cycle models seems essential to appropriately determine land C uptake.…”

“…As it is not yet clear where and how strong N and P constrain today's plant productivity and soil C turnover (Elser et al, 2007;Zaehle and Dalmonech, 2011;Townsend et al, 2011), we developed a new modelling concept of nutrient limitation to avoid prescribing nutrient limitation in the inital model state. We assume that during thousands of years of stable Holocene climate and relatively low atmospheric CO 2 concentration, plants have adapted to their environment such that their growth is limited by multiple resources (Field et al, 1992;Townsend et al, 2011). We thus hypothesize that for present day, ecosystems are co-limited by the availability of N and P, which is in broad terms consistent with a meta-analysis of N and P manipulation experiments across global biomes (Elser et al, 2007).…”

Soil phosphorus responses to chronic nutrient fertilisation and seasonal drought in a humid lowland forest, Panama

“…Our findings for the NaOH P i fraction agree with the pattern for other regions with seasonal drought, in which values peak during the wet season (cf. Chacón et al 2008;Valdespino et al 2009). The interpretation is that the binding ability of Fe and Al oxides for NaOH P i is greater in wet than in dry soil.…”