查看更多>>摘要：Microbial metabolism changes in soil systems along a vegetation restoration gradient have attracted considerable attention; however, the differences in microbial metabolic limitations between the rhizosphere and bulk soil and their drivers during natural secondary forest restoration after disturbance have rarely been investigated. Here, we used multiple methods based on extracellular enzymatic stoichiometry to examine the microbial metabolic limitations in the rhizosphere and bulk soils along with a clear-cut oak (Quercus aliena var. acuteserrata) forest restoration over 58 years in the Qinling Mountains, China. Overall, the microbial metabolisms in both rhizo-sphere and bulk soils were co-limited by the availability of soil carbon (C) and phosphorus (P), and the limi-tations tended to decrease during restoration. Rhizosphere soil microorganisms were subject to relatively strong C limitation and weak P limitation compared with those in bulk soil. Microbial C and P limitations in the bulk soil were regulated by the nutrient ratios, and those in the rhizosphere soil were mainly dependent on the available nutrients mediated by soil moisture. Our results indicate that variations in the soil nutrients caused by oak forest restoration and water differences caused by the rhizosphere effect regulated microbial C and P metabolism in the rhizosphere and bulk soils. This study highlights the microbial metabolism difference between rhizosphere and bulk soil and its drivers during oak forest restoration and provides insights into the microbial resource limitation, nutrient cycling, and rhizosphere processes in the natural secondary forests after clear-cutting.
查看更多>>摘要：Browsing damage in forests relies on a complex interaction between herbivore density and forest understory composition and relative availability. Although variation in the amount of browsed twigs is sometimes used to assess abundance of large herbivores, the potential confounding effect of resource availability on this relation-ship has not been investigated yet. To fill the gap, we measured how browsing intensity of the woody plants varied in response to changes in both roe deer (Capreolus capreolus) abundance and vegetation availability from an intensive long-term monitoring. We estimated plant availability and consumption by roe deer from a modified Aldous method throughout a 14 year-long period during which we experimentally manipulated population density. The functional response was strongly non-linear and density-dependent. When plant availability was low (<12.5%), browsing intensity strongly increased with plant availability with an increasing rate of roe deer density, whereas beyond this threshold, browsing intensity slightly increased with both plant availability and population density in an additive way. Thus, forest susceptibility to browsing increases with increasing competition for food, especially when plant availability is low. Moreover, the interplay between browsing in-tensity and population density at low plant availability prevents the use of browsing intensity to monitor roe deer abundance when plant availability is low. Our findings provide clear evidence that relying on key ecological concepts such as functional responses improves the accuracy of management tools when monitoring changes of the herbivore-plant system over time.
NSTL
Elsevier