Abstract. Restoration ecology can benefit greatly from developments in trait-based ecology that enable improved predictions of how the composition of plant communities will respond to changes in environmental conditions. Plant functional traits can be used to guide the restoration of degraded habitats by closely tailoring treatments to the local species pool. We tested this approach in two heavily invaded coastal California grasslands. We asked whether native plant abundance and plant community trait composition respond to (1) experimental soil fertility reduction in the form of twice-yearly carbon (C) amendments and (2) disturbance in the form of mowing. We measured height, specific leaf area, leaf thickness and leaf density from individuals of 39 species in the control and C addition plots, and supplemented these trait values with database information on growth form, lifespan, nitrogen-fixing ability and seed mass.Consistent with theoretical predictions, C addition favored short, large-seeded and nitrogen-fixing species, while mowing benefitted short species with high specific leaf area. However, native and exotic species did not differ in any of the measured traits, and neither group benefitted generally from the treatments. Carbon addition led to large intraspecific trait shifts, with individuals in C addition plots having smaller, denser leaves and shorter stature. Species' trait plasticity, however, was not related to the community composition response to C addition.Our study indicates that trait-based ecology is sufficiently mature to provide useful predictions in the realm of restoration ecology. Trait screening at a site can help predict the success of a particular restoration measure in that community.
Rice field outflow can contain high concentrations of dissolved organic carbon (DOC), which plays a crucial role in drinking water quality and aquatic ecosystem processes. This study examined the relationship between potential determining factors (i.e. rice area, outflow, drainwater reuse, soil properties, and time, measured as the day in the growing season) and the concentration and composition of DOC exported from 11 rice-dominated subwatersheds. Samples were collected from subwatershed inflow and outflow every 1-2 weeks from May through September 2008 and analyzed for DOC concentration, trihalomethane formation potential (THMFP), and also specific ultraviolet absorbance (SUVA 254 ) and the spectral slope parameter (S), which are indicators of DOC composition. Concentrations of DOC across all subwatersheds and sampling dates ranged from 1.56 to 14.43 mg L -1 (mean = 4.32 mg L -1 ). Linear mixed effects (LME) analysis indicated that DOC concentration decreased over time, and that THMFP, and DOC and THM flux, decreased over time, but increased with outflow. LME analysis of the SUVA 254 and S parameters indicated that the fraction of aromatic DOC moieties increased with time, outflow, and reuse. Additionally, apparent peaks in DOC concentrations, THMFP, and SUVA 254 coincided with the onsets of flooding and draining. Lastly, subwatersheds with outflow less than approximately 4,700 m 3 ha -1 behaved as sinks of DOC. Our findings suggest that water management factors such as outflow, reuse, and discrete irrigation events, all of which vary over the course of the growing season, were the dominant determinants of DOC concentration and composition.
The removal of conifers through commercial timber harvesting has been successful in restoring aspen, however many aspen stands are located near streams, and there are concerns about potential aquatic ecosystem impairment. We examined the effects of management-scale conifer removal from aspen stands located adjacent to streams on water quality, solar radiation, canopy cover, temperature, aquatic macroinvertebrates, and soil moisture. This 8-year study (2003–2010) involved two projects located in Lassen National Forest. The Pine-Bogard Project consisted of three treatments adjacent to Pine and Bogard Creeks: (i) Phase 1 in January 2004, (ii) Phase 2 in August 2005, and (iii) Phase 3 in January 2008. The Bailey Project consisted of one treatment adjacent to Bailey Creek in September 2006. Treatments involved whole tree removal using track-laying harvesters and rubber tire skidders. More than 80% of all samples analyzed for NO3-N, NH4-N, and PO4-P at Pine, Bogard, and Bailey Creeks were below the detection limit, with the exception of naturally elevated PO4-P in Bogard Creek. All nutrient concentrations (NO3-N, NH4-N, PO4-P, K, and SO4-S) showed little variation within streams and across years. Turbidity and TSS exhibited annual variation, but there was no significant increase in the difference between upstream and downstream turbidity and TSS levels. There was a significant decrease in stream canopy cover and increase in the potential fraction of solar radiation reaching the streams in response to the Pine-Bogard Phase 3 and Bailey treatments; however, there was no corresponding increase in stream temperatures. Macroinvertebrate metrics indicated healthy aquatic ecosystem conditions throughout the course of the study. Lastly, the removal of vegetation significantly increased soil moisture in treated stands relative to untreated stands. These results indicate that, with careful planning and implementation of site-specific best management practices, conifer removal to restore aspen stands can be conducted without degrading aquatic ecosystems.
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