Restoring function: Positive responses of carbon and nitrogen to 20 years of hydrologic restoration in montane meadows.

Montane meadows are highly productive ecosystems that contain high densities of soil carbon (C) and nitrogen (N). However, anthropogenic disturbances that have led to channel incision and disconnected floodplain hydrology have altered the C balance of many meadows, converting them from net C sinks to net sources of C to the atmosphere. Restoration efforts designed to reconnect floodplain hydrology may slow rates of soil C loss from degraded meadows and restore the conditions for C sequestration and N immobilization, yet questions remain about the long-term impact of such efforts. Here, we used a 22-year meadow restoration chronosequence to measure the decadal impact of hydrologic restoration on aboveground and belowground C and N stocks and concentrations. Increases in herbaceous vegetation biomass preceded changes in soil C stocks, with the largest gains occurring belowground. Root biomass (0-15 cm) increased at a rate of 270.3 g m-2 year-1 and soil C stocks (0-15 cm) increased by 232.9 g C m-2 year-1 across the chronosequence. Increases in soil C concentration (2.99 g C kg-1 year-1 ) were tightly coupled with increases in soil N concentration (0.21 g N kg-1 year-1 ) and soil C:N did not vary with time since restoration. Fourier transform infrared spectroscopy results showed that the fraction of labile aliphatic C-H and carboxylate C-O (COO) compounds in the soil increased with the age of restoration and were positively correlated with soil C and N concentrations. Our results demonstrate that restoration of floodplain hydrology in montane meadows has significant impacts on belowground C and N stocks, soil C and N concentration, and soil C chemistry within the first two decades following restoration.

Changes in belowground biodiversity during ecosystem development.

Belowground organisms play critical roles in maintaining multiple ecosystem processes, including plant productivity, decomposition, and nutrient cycling. Despite their importance, however, we have a limited understanding of how and why belowground biodiversity (bacteria, fungi, protists, and invertebrates) may change as soils develop over centuries to millennia (pedogenesis). Moreover, it is unclear whether belowground biodiversity changes during pedogenesis are similar to the patterns observed for aboveground plant diversity. Here we evaluated the roles of resource availability, nutrient stoichiometry, and soil abiotic factors in driving belowground biodiversity across 16 soil chronosequences (from centuries to millennia) spanning a wide range of globally distributed ecosystem types. Changes in belowground biodiversity during pedogenesis followed two main patterns. In lower-productivity ecosystems (i.e., drier and colder), increases in belowground biodiversity tracked increases in plant cover. In more productive ecosystems (i.e., wetter and warmer), increased acidification during pedogenesis was associated with declines in belowground biodiversity. Changes in the diversity of bacteria, fungi, protists, and invertebrates with pedogenesis were strongly and positively correlated worldwide, highlighting that belowground biodiversity shares similar ecological drivers as soils and ecosystems develop. In general, temporal changes in aboveground plant diversity and belowground biodiversity were not correlated, challenging the common perception that belowground biodiversity should follow similar patterns to those of plant diversity during ecosystem development. Taken together, our findings provide evidence that ecological patterns in belowground biodiversity are predictable across major globally distributed ecosystem types and suggest that shifts in plant cover and soil acidification during ecosystem development are associated with changes in belowground biodiversity over centuries to millennia.

Multiple elements of soil biodiversity drive ecosystem functions across biomes.

The role of soil biodiversity in regulating multiple ecosystem functions is poorly understood, limiting our ability to predict how soil biodiversity loss might affect human wellbeing and ecosystem sustainability. Here, combining a global observational study with an experimental microcosm study, we provide evidence that soil biodiversity (bacteria, fungi, protists and invertebrates) is significantly and positively associated with multiple ecosystem functions. These functions include nutrient cycling, decomposition, plant production, and reduced potential for pathogenicity and belowground biological warfare. Our findings also reveal the context dependency of such relationships and the importance of the connectedness, biodiversity and nature of the globally distributed dominant phylotypes within the soil network in maintaining multiple functions. Moreover, our results suggest that the positive association between plant diversity and multifunctionality across biomes is indirectly driven by soil biodiversity. Together, our results provide insights into the importance of soil biodiversity for maintaining soil functionality locally and across biomes, as well as providing strong support for the inclusion of soil biodiversity in conservation and management programmes.