Summary
Although the effect of experimental warming on soil microorganisms has been well documented at surface horizons, less is known about its influence in subsurface horizons. An experiment was therefore carried out in an alpine meadow on the Qinghai‐Tibet Plateau to examine the responses of microbial communities to experimental warming at five soil depths (0–10, 10–20, 20–30, 30–40 and 40–50 cm). Plots were passively warmed for 3 years in open‐top chambers and compared with adjacent control plots at ambient temperature. Soil microbial communities were assessed by using phospholipid fatty acid (PLFA) analysis. Our results showed clearly that 3 years of experimental warming increased microbial biomass consistently and significantly throughout the upper 50‐cm soil profiles, as indicated by the changes in both microbial biomass carbon (C) and total PLFA contents. The composition of microbial communities was also affected significantly by warming, but its effect depended on soil depth. While warming induced a community shift towards bacteria at the 0–10‐cm depth, it tended to shift microbial communities towards fungi at the other, deeper, layers. These results indicate that warming had strong effects on soil microbial communities, including even those residing in subsurface horizons, which may help us to understand the microbial mediation of the feedback between terrestrial C cycling and climate warming.
Chinese leymus [Leymus chinensis (Trin.) Tzvel.] is an important forage distributed in East Asia. The seed-set rates and the pollen-stigma compatibility in six populations were investigated in 2001. Proportionately seed-set ranged from 0AE065 to 0AE567 under open pollination and 0AE0056 to 0AE0426 under self-pollination. The former is significantly higher than the latter in each population. Microscopic observations showed that proportionately only 0AE0551 to 0AE1167 of self-pollinated pollen grains were compatible but most cross-pollinated pollen grains were compatible. The tubes of most incompatible pollen grains aborted upon entering into the stigmas. Among the six populations, there was a significant correlation between seed-set under open pollination and the compatible pollen rates under cross-pollination. These results suggest that Chinese leymus is a self-incompatible species, and the compatibility of pollen and stigma might be one of the factors influencing seed-set in natural conditions. This information will be useful for future breeding efforts.
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