PMC

Changes in organic and inorganic phosphorus content of different forms in rhizosphere soils. Al-P: aluminium-bound phosphorus; Fe-P: iron-bound phosphorus; Ca-P: calcium-bound phosphorus; O-P: insoluble phosphorus (iron oxide gel-coated phosphate); LOP: easily mineralised and absorbed by plants; MLOP: relatively easy to mineralise and absorbed by plants; MROP: more difficult to mineralise and difficult to absorb by plants; HROP: more stable, insoluble and difficult to mineralized and basically not absorbed by plants; Organic P: numerically equal to the sum of the contents of the four organic phosphorus forms, Inorganic P: numerically equal to the sum of the four inorganic phosphorus forms; Unextracted P: numerically equal to the total phosphorus content minus total organic phosphorus and total inorganic phosphorus.

Percentage of plant organic carbon, plant total nitrogen, and total phosphorus of dominant species in the study sites. (a) The organic carbon, total nitrogen, total phosphorus of Agropyron mongolicum under the interaction of the precipitation changing and temperature increasing (TR); (b) The organic carbon, total nitrogen, total phosphorus of Lespedeza bicolor under the interaction of the precipitation changing and temperature increasing(TR); (c) The organic carbon, total nitrogen, total phosphorus of Polygala tenuifolia under the interaction of the precipitation changing and temperature increasing(TR); (d) The organic carbon, total nitrogen, total phosphorus of Agropyron mongolicum under the precipitation changing (R); (e) The organic carbon, total nitrogen, total phosphorus of Lespedeza bicolor under the precipitation changing (R); (f) The organic carbon, total nitrogen, total phosphorus of Polygala tenuifolia under the precipitation changing (R); (g) The organic carbon, total nitrogen, total phosphorus of Agropyron mongolicum under the temperature increasing (T); (h) The organic carbon, total nitrogen, total phosphorus of Lespedeza bicolor under the temperature increasing (T); (i) The organic carbon, total nitrogen, total phosphorus of Polygala tenuifolia under the temperature increasing (T). Five levels of rainfall (R) were used: 33% (R33), 66% (R66), 100% (CK), 133% (R133), and 166% (R166) of the annual average. The first two rainfall conditions were obtained by using two rainout shelters with two manipulated rainfall doses: 97 mm (R33) and 194 mm (R66). For the three other rainfall conditions, we artificially increased rainfall in unsheltered plots using a watering pot: 295 mm (CK), 392 mm (R133), and 490 mm (R166). The temperature consisted of two levels: the actual temperature (CK) and the interaction between rainfall and the temperature, which was increased by about 2 °C (T) with the OTC (Open-Top Chamber) in each plot. TR33 was the first site of interaction between 33% precipitation (R33) and the temperature increase of about 2 °C (T), and the marks of TR66, TCK, TR133, TR166 are the same. R33 was the first site of 33% precipitation, and the marks of R66, CK, R133, R166 are the same. Values indicate the mean ± SE, and different letters represent a significant difference according to LSD test (p < 0.05).

(A) Ratios of organic carbon vs. organic nitrogen and organic carbon vs. organic phosphorus along the continuum beginning from the Baltic Proper and western Gulf of Finland towards the eastern Gulf of Finland (sampling sites 1−9), (B) in the Ahvenkoskenlahti Bay estuary (sampling sites 10−12) and along the sediment depth. Refer to locations of the sediment sampling sites in .

Conceptual diagram of the dominant carbon, nitrogen, and phosphorus cycling processes in oxic (top) and anoxic (bottom) conditions in the water column of a thermally stratified reservoir. Carbon processes include cycling of carbon dioxide (CO₂), dissolved organic carbon (DOC), methane (CH₄), and particulate organic carbon (POC). Nitrogen processes include cycling of dissolved organic nitrogen (DON), nitrogen gas (N₂), ammonium (NH₄ ⁺), nitrate (NO₃ ⁻), and particulate organic nitrogen (PON). Phosphorus processes include cycling of dissolved organic phosphorus (DOP), dissolved reactive phosphorus (DRP), and particulate organic phosphorus (POP). Processes are denoted by arrows