Treesearch

Dams fragment the longitudinal flux of sediment and obstruct fish passage. To help remediate these impacts, dam removal has become an important tool in the river restoration toolkit. Scientifically, these removals also provide an important experimental design, fixed in time and space, to quantify geomorphic and ecological responses to removal of a disturbance. Using the removal of a 6 m high dam in Massachusetts (USA), we quantify the immediate and subsequent channel and ecological recovery to test whether the immediate ecological/geomorphic responses were sustained or transient. Initial...

Climate change adaptation requires that we anticipate future conditions that may deviate from our historical experiences. Our ability to do so is associated with the perceived proximity of decision-outcomes. Through analysis of semi-structured interviews with farmers in the northeastern United States, we conclude that temporal distance (now versus later) and social distance (self versus other) of climate impacts interact to play important roles in climate risk perception. Using Psychological Distance and Construal Level Theory, we identified two distinct temporal perspectives, historically...

The Coweeta Hydrologic Laboratory (CHL) is a USDA Forest Service (FS) Experimental Forest, located in western North Carolina, in the southern Appalachian Mountains. Established in 1934, CHL has long-term data records that include climate, streamflow, stream and atmospheric chemistry, and vegetation in several small, experimentally-manipulated and reference watersheds. In addition to these long-term data, additional data associated with specific projects have been collected and are available through publications and electronic archives. Notably, CHL was a member of the National Science...

The water-quality effects of low-density rural land-use activities are understudied but important because of large rural land coverage. We review and synthesize spatially extensive studies of oligotrophic mountain streams in the rural Southern Appalachian Mountains, concluding that rural land-use activities significantly degrade water quality through altered and mostly enhanced landscape–stream connections, despite high forest retention. Some connections (insolation, organic inputs, root–channel interactions, stream–field connectivity, individual landowner discharges) are controlled by...

In the past century, the evergreen woody shrub, Rhododendron maximum, has experienced habitat expansion following foundational tree species die-off in eastern US deciduous forests. Rhododendron can potentially alter stream chemistry, temperature, trophic dynamics, and in-stream decomposition rates, given its dominance in riparian areas. Here we conducted two operational-scale (3 ha) riparian treatments that removed rhododendron through cutting alone (CR, canopy removal), or removing both the rhododendron canopy and forest floor using cutting and prescribed fire (CFFR, canopy and forest...

Soil organic matter composition controls many microbial processes in the soil matrix. How these processes interact to drive carbon cycling through greenhouse gas fluxes or carbon stabilization through biochemical transformations continues to evolve. From laboratory incubations, it is clear that low molecular weight compounds (LMWCs; e.g. dextrose, mannitol, and trehalose) can have a profound effect on microbially mediated fluxes. However, relationships between LMWCs and soil efflux have been largely unproven in field studies due to methodological constraints. In the current study we...

Cloud-water interception (CWI) is the process by which fog or cloud water droplets are captured and accumulate on the leaves and branches of plants, some of which drips to the ground. Prior studies in Hawai'i indicate that CWI is highly variable and can contribute substantially to total precipitation. In this study, we monitored CWI and other processes at five mountain field sites on the Islands of Oʻahu, Maui, and Hawaiʻi to explore how CWI (1) varies with different climate and vegetation characteristics, (2) affects plant water use and growth, and (3) contributes to water resources....

Trees can have large effects on soil nutrients in ways that alter succession, particularly in the case of nitrogen-(N)-fixing trees. In Hawai’i, forest restoration relies heavily on use of a native N-fixing tree, Acacia koa (koa), but this species increases soil-available N and likely facilitates competitive dominance of exotic pasture grasses. In contrast, Metrosideros polymorpha (‘ohi’a), the dominant native tree in Hawai’i, is less often planted because it is slow growing; yet it is typically associated with lower soil N and grass biomass, and greater native understory recruitment. We...

Outbreaks of defoliating insects in low-diversity tropical forests occur infrequently but provide valuable insights about outbreak ecology in temperate environments and in general. We investigated an extensive outbreak of the endemic koa moth (Scotorythra paludicola), which defoliated endemic koa trees (Acacia koa) over a third of their range on Hawai‘i Island during 2013 and 2014. At Hakalau Forest National Wildlife Refuge, we observed the dynamics of the outbreak and its effects on host trees, nutrient cycling, and insectivorous consumers in reforestation stands of densely planted koa...

To better understand hydraulic adaptations of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii(Mirb.) Franco) to local climate, we examined genetic (G) and environmental (E) responses of branch hydraulic architecture of 7-year-old saplings from dry and wet climates of origin grown at a relatively dry and a relatively wet common garden site in western Oregon. We sampled 2 years of branch growth from three dry-source and three wet-source families grown at both sites (72 branches, total). Overall, only 4 of the 11 traits had significant genetic (G) effects, whereas 9 traits had...