The indiscriminate use of chemical fertilizers has led to adverse environmental impacts and poor crop quality and accelerates the depletion of mineral reserves used for fertilizer production. Microbes are vital in soil nutrient cycling, and some effectively enhance soil nutrient supply and reduce chemical fertilizer usage. Biocontrol bacterium Lysobacter enzymogenes LE16 can produce various hydrolases against plant pathogens to mineralize soil organics via enzyme production. Therefore, the enzyme production, soil organic P and N mineralization, and crop agronomic performances induced by L. enzymogenes LE16 were investigated by pure culture, soil incubation, and greenhouse pot experiments. L. enzymogenes LE16 can hydrolyze lecithin and protein and convert them to inorganic P and NH₄⁺-N. Similarly, available P and N increased as this bacterium was inoculated and grown in the tested soil. In the greenhouse pot experiment, phosphomonoesterase and protease produced by L. enzymogenes LE16 inoculant effectively mineralized soil organic P and N and enhanced soil available nutrients, thereby improving the nutrient uptake, fertilizer utilization rate, and agronomic efficiency of lettuce and pepper seedlings. Bacterial inoculation increased the lettuce yield by 6.43–11.30% and pepper fruit yield by 43.82–70.32%, even with less chemical fertilizer application. Therefore, L. enzymogenes LE16 can hydrolyze lecithin and protein in pure cultures, and mineralize organic P and N in soils, thus improving crop yield and quality and reducing chemical fertilizer application via the production of phosphomonoesterase and protease. L. enzymogenes LE16 shows potential for sustainable agriculture beyond plant protection.

Gap formation and its effects on regeneration have been reported as being important in forest development, but seldom studies concentrated on the gap closure process by lateral extension growth of canopy trees surrounding gaps. We monitored the closure process of 12 artificial gaps for 7 years with three size classes: small (from 68 mto 125 m), middle (from 174 m to 321 m), and large (from 514 m to 621 m); and investigated the regeneration twice in a temperate secondary forest, Northeast China. The closure process can be described through quadratic functions, which showed the closure rates slowed down with gap ages. Large gaps had a higher closure rate (39 m a) than middle gaps (25 m a) and small gaps (11 m a). According to the quadratic equations, the lateral growth could last 11, 13 and 16 years for small, middle and large gaps with a remaining size of 12, 69 and 223 m, respectively. As expected, regeneration exhibited the highest seedling density and volume in large gaps. There was no significant difference in regeneration density between middle gaps, small gaps and forest understory in the final investigation; but the volume of regenerated woody species increased significantly from small gaps to large gaps compared with forest understory. These results may provide references on the choice of appropriate gap sizes to promote the regeneration in temperate secondary forests.2 2 2 2 2 2 2 –1 2 –1 2 –1 2