Nodulation and nitrogen accretion response of Cercocarpus betuloides seedlings to phosphorus supplementation and water availability

Abstract

Greenhouse experiments were conducted to assess the effect of phosphorus (P) supplementation and water availability on incidence of nodulation and nitrogen (N) fixation by Cercocarpus betuloides seedlings. Phosphorus supplementation resulted in a two-fold increase in shoot and total dry matter of seedlings grown in a P-deficient soil. Seedlings grown in P-supplemented soil supported a larger number (4.8 vs. 0.3) and fresh mass (0.179 vs. 0.009g) of nodules than did controls. Nitrogenase activity (acetylene reduction), N concentration and N accretion were greater for seedlings grown in P-amended soil than for controls.Seedlings were grown at four soil water potentials-0.1, -0.2, -0.4, and -0.7 MPa for 214 days. Biomass production, nodulation, acetylene reduction activity and N accretion were greatest at -0.2 MPa and declined at higher and lower soil water potentials. Independently-measured dependent variables were highly correlated, suggesting that water availability was influencing a primary plant process, most likely photosynthesis, on which other plant processes are dependent.

Effects of nitrogen: phosphorus supply ratios on nitrogen fixation in agricultural and pastoral ecosystems

“…Additional evidence for phosphorus effects on N-fixation by other symbiotic systems derives from recent studies of an actinorhizal shrub (Weinhold & Klemmedson 1991) and of the black locust (Guofan & Tingxiu 1991). Phosphorus availability has been implicated as a limiting factor for both nodulation and N-fixation in actinorhizal plants, and Weinhold & Klemmedson (1991) have demonstrated strong stimulatory effects of P fertilization on nitrogenase activity in Cercocarpus betuloides seedlings. Similarly, Guofan & Tingxiu (1991) explored the edaphic controls of nitrogen fixation by black locust (Robiniu pseudoacacia L.) seedlings grown in pot cultures on 42 types of forest soils, and developed regression models relating N-fixation to soil chemistry.…”

Aspect and species influences on nitrogen and phosphorus accumulation in Arizona chaparral soil‐plant systems

“…We attribute this to N fixation in Cercocarpus. We have collected nodules from roots of Cercocarpus shrubs growing at Battle Flat and laboratory studies (Wienhold and Klemmedson 1991) suggest that under favorable moisture, temperature, and nutrient conditions this actinorhizal shrub is capable of fixing significant amounts of N. In a chaparral chronosequence of southern California, Marion and Black (1988) attributed increased soil N accretion to the presence of Ceanothus greggii, which is also an actinorhizal shrub. Other reports (Delwiche et al 1965, Vlamis et al 1971, Dunn and Poth 1979 document the contribution of N fixed by symbiotic organisms associated with herbs and shrubs of the chaparral type.…”