Cattle grazing facilitates tree regeneration in a conifer forest with palatable bamboo understory

In a temperate mixed conifer forest in the Bhutan Himalayas, we investigated the effects of cattle grazing on conifer (Tsuga dumosa, Pinus wallichiana, Picea spinulosa, Abies densa) seedling density, growth and microsite of recruitment under dense cover of the bamboo Yushania microphylla, using exclosures over a period of 9 years after group selection harvest. Increasing bamboo competition over time following canopy opening successfully prevented seedling recruitment in ungrazed plots, while recruitment in grazed plots was continuous. Reduction of bamboo height through grazing facilitated recruitment of all tree species, particularly T. dumosa, mainly through increased light interception on the forest floor. Tree species composition of seedlings and the overstory did not differ in ungrazed plots, while in grazed plots we observed a shift towards dominance of T. dumosa. Growth rates of T. dumosa and P. spinulosa were higher in grazed plots as compared to ungrazed plots. In grazed plots, recruitment of T. dumosa was concentrated on moss, which might have prevented desiccation of the small-seeded species after germination. We propose that controlled grazing might facilitate natural regeneration after logging in mixed conifer forests of central Bhutan with dense Y. microphylla bamboo understory.