Abstract
Black alder, an N-fixing tree is considered to accelerate the availability of phosphorus in soils due to the increased production of phosphatase enzymes, which are responsible for the P release from the litter. Acid phosphatase activity plays a pivotal role in organic P mineralization in forest soils and in making P available to plants. In order to check whether <em>Alnus glutinosa </em>stimulates acid phosphomonoesterase (PH<sub>ACID</sub>) activity, we compared enzyme activities, total P concentration (P<sub>TOT</sub>), plant-available P (P<sub>AVAIL</sub>), organic P (P<sub>ORG</sub>) and inorganic P (P<sub>INORG</sub>), and organic matter content in 27 ancient and 27 post-agricultural alder woods (the latter ones representing different age classes: 11-20, 21-40 and 41-60 years) of soil samples taken from the litter and the mineral layers. Phosphomonoesterase activity, organic matter, P<sub>TOT</sub>, P<sub>INORG</sub> and P<sub>ORG</sub> concentrations were significantly higher in ancient alder woods than in the soils of post-agricultural forests. Significant differences in the acid phosphatase activity, organic matter and P<sub>AVAIL</sub> concentration were noted between the litter and mineral layers within the same forest type. In recent stands the amount of organic matter and phosphatase activity increased significantly with the age of alder stands, although only in the mineral layer of their soils. Phosphomonoesterase activity, organic matter and P<sub>AVAIL</sub> content were higher in a litter layer and decreased significantly at a mineral depth of the soil. The acid phosphatase activity was significantly correlated with organic matter content in both ancient and recent stands. There was no significant relationship between PH<sub>ACID</sub> activity and any P forms.
Highlights
Several phosphatases are involved in the hydrolysis of organic P compounds but the major role in the organic phosphorus mineralization process is attributed to the phosphomonoesterases
Organic matter, total, inorganic and organic P concentrations were significantly higher in soils from ancient alder woods than in soils from the recent ones
Significant differences in the available P concentration were observed between the litter and mineral layers in the same forest type
Summary
Several phosphatases are involved in the hydrolysis of organic P compounds but the major role in the organic phosphorus mineralization process is attributed to the phosphomonoesterases. Acid phosphomonoesterase enzymes are the dominant group of enzymes involved in organic P mineralization in acidic soils [1]. These enzymes are produced mainly by plants and fungi and to a lesser degree by bacteria. Plant available P (PAVAIL) concentration increases in soils underlying plantations of N-fixing trees [1], probably due to a higher P requirement by N-fixing plants [3]. The relationship between the available P concentration and phosphatase activity is usually very complex, since a positive, a negative or no relationship
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