Guidelines for Riparian Vegetative Shade Restoration Based Upon a Theoretical Shaded‐Stream Model1

Abstract: Guidelines for riparian vegetative shade restoration were developed using a theoretical model of total daily radiation received by a shaded stream. The model assumed stream shading by nontransmitting, vertical or overhanging, solid vegetation planes in infinitely long reaches. Radiation components considered in the model were direct beam shortwave on the stream centerline, diffuse atmospheric shortwave, shortwave reflected by vegetation, atmospheric longwave, and longwave emitted by vegetation. Potential or extraterrestrial shortwave irradiation theory was used to compute beam shortwave radiation received at the stream centerline, and view factor theory was used to compute diffuse radiation exchange among stream, vegetation, and atmospheric planes. Model shade effects under clear skies were dominated by reductions in receipt of direct beam shortwave radiation. Model shade effects with cloudy skies were dominated by the “view factor effect” or the decreases in diffuse shortwave and longwave radiation from the atmosphere balanced against increases in longwave radiation from vegetation. Model shade effects on shortwave radiation reflected by vegetation were found to be negligible. The model was used to determine the vegetation height (H) to stream width (W) ratios needed to achieve 50, 75, and 90 % shade restoration for mid‐latitude conditions on clear and cloudy days. Ratios of vegetation height to stream width, for dense nontransmitting vegetation, generally ranged from 1.4 to 2.3 for 75% shade restoration at a mid‐latitude site (40°N). The model was used to show H/W needed for E‐W vs. N‐S stream azimuths, varying stream latitudes between 30° and 50°N, channels with overhanging vegetation, channels undergoing width changes, as well as the limits to shade restoration on very wide channels.     

安徽沿江地带投资环境综合研究

改善投资环境吸引外资是经济发展的重要内容。安徽沿江地带是长江经济带重要的组成部分，对安徽沿江地带投资环境进行了分析与评价，并就进一步完善沿江地带宏观投资环境，推动经济联合发展提出了建议与措施。     

Life-history traits and the fate of translocated populations

Attempts to identify predictors and mechanisms of invasion success have been weakened by poor data quality, mostly because monitoring does not begin immediately after introduction events. To overcome this issue, we used data from conservation translocations of threatened bird species. We analyzed information on >1200 translocation events of >150 bird species to investigate how life-history traits affect population establishment measured based on rates of survival and reproduction. Species position along the slow–fast life-history continuum was a key predictor of translocation success. Species with fast-paced life histories were less likely to survive (over both short- and mid-term) and more likely to breed successfully than species with slow life histories. The temporal partitioning of reproductive effort (number of clutches per year) also affected the probability of successful reproduction. Our results illustrate how conservation-motivated reintroduction programs can provide proxies for the initial stages of the invasion process, enabling empirical tests of predictions from life-history theory and informing management.     

梯级开发河流污染物的积累性和缓冲性——兼论惰性物的积累模型

本文论述了梯级开发河流的“水库－河流”两重性，当该河流呈水库性质时，会发生对污染物的积累和缓冲；同时，论述了惰性物质氯离子（Ｃｌ＾－）的积累模型，提出了破坏此积累性和缓冲性的临界流量，以及如何用它来改善梯级开发河流的水质。     

The Buffer Capacity of Calcareous Soils in Gansu Province of China

In this study, we added increments of acid and base to three calcareous soils from the eastern, middle and western parts of Gansu Province (China) and to three treated soils to remove calcium carbonate, organic matter and both carbonate and organic matter, respectively. the titration curves were measured and the magnitudes of buffer capacities as a function of pH were computed. It was found that the buffer capacity of calcareous soil is mainly attributed to calcium carbonate, as expected from the chemical composition of calcareous soil, while cation exchange system, silicate buffer system and organic matter play a minor role. the results clearly show that these soils of Gansu Province will not become a problem in the near future from the entrance of H⁺ into these soils.     

Effects of Buffer-Strip Retention and Clearcutting on Land Snails in Boreal Riparian Forests

Abstract:  We investigated the short-term effects of forest clearcutting on land snails (terrestrial gastropods) in 15 forest stands along small streams in Sweden. Two different silvicultural treatments were applied at each site: clearcutting across the stream channel and buffer strips 10 m wide on each side of the stream. Additionally, we studied 10 reference sites in unlogged riparian forests along similar-sized streams. All sites were studied before logging and then 2.5 years after logging. After clearcutting the number of individuals in a 0.5-m² sample from each site decreased on average from 107 to 87, and the mean number of species per sample decreased from 9.9 to 7.7. Most species were negatively affected, but there were also clear differences in sensitivity. There were correlations between species survival and ground moisture. At the wettest clearcut sites with an almost intact bryophyte cover, the land snails were unaffected by clearcutting. This result suggests that wet or moist forest floors can serve as refugia even at very small spatial scales (e.g., shallow hollows, crevices). If this is an important mechanism, the spatial distribution of small habitats could be important for the long-term survival of the snail fauna or other small, dispersal-limited organisms at clearcut sites. In the buffer strips, the number of individuals decreased but not the number of species, indicating that buffer-strip retention is a good practice for protecting land snails in riparian forests. The varying effectiveness of the buffer strip could partly be explained by the proportion of the remaining basal area, emphasizing that buffer strips could be even more effective if efforts are made to avoid heavy damage by windthrows.     

Instream Large Wood: Denitrification Hotspots with Low N2O Production

We examined the effect of instream large wood on denitrification capacity in two contrasting, lower order streams — one that drains an agricultural watershed with no riparian forest and minimal stores of instream large wood and another that drains a forested watershed with an extensive riparian forest and abundant instream large wood. We incubated two types of wood substrates (fresh wood blocks and extant streambed wood) and an artificial stone substrate for nine weeks in each stream. After in situ incubation, we collected the substrates and their attached biofilms and established laboratory‐based mesocosm assays with stream water amended with ¹⁵N‐labeled nitrate‐N. Wood substrates at the forested site had significantly higher denitrification than wood substrates from the agricultural site and artificial stone substrates from either site. Nitrate‐N removal rates were markedly higher on woody substrates compared to artificial stones at both sites. Nitrate‐N removal rates were significantly correlated with biofilm biomass. Denitrification capacity accounted for only a portion of nitrate‐N removal observed within the mesocosms in both the wood controls and instream substrates. N₂ accounted for 99.7% of total denitrification. Restoration practices that generate large wood in streams should be encouraged for N removal and do not appear to generate high risks of instream N₂O generation.     

Ranking Agricultural Sub-basins for Environmental Protection

Abstract

Reconstructing long-term vegetation buffers along streams in agricultural landscapes has become a common environmental restoration strategy for improving water quality and wildlife habitat connectivity. This article developed a linear weighted model to rank the priority of agricultural sub-basins for the establishment of vegetative buffers. The method was applied to an agricultural watershed of 146 km² in Ontario, Canada. The watershed was divided into 11 sub-basins as basic decision units. In each subbasin, four stream buffer schemes with widths of 5, 10, 15 and 20m were generated. For each buffer, three benefit-cost attributes of reconstructing vegetation cover were estimated, which include acreage per dollar, sediment abatement per dollar and habitat benefit per dollar. These attributes were first normalized using a linear normalization approach to eliminate the effects across different units. The normalized attributes were then integrated using a simple additive weighting method to rank the 11 sub-basins for prioritizing spatial restoration action. A sensitivity analysis was also conducted to observe the impact of a change in attribute weights on the management decisions. The results suggest that vegetation buffers reconstructed for achieving the water quality goal are not effective in improving habitat connectivity and vice versa.     

Impacts of Climatic Change On Peatland Hydrochemistry; A Laboratory-Based Experiment

A laboratory simulation of a reduction in water table height that could be anticipated from current climate change models, resulted in a change in the efficiency with which a valley-bottom wetland acted as a sink/source of nutrients. Effects were confined to the upper 10 cm of the profile, but since this depth has the greatest hydraulic conductivity, it was noted that the effects of hydrochemical changes therein would be readily transferred to receiving waterbodies. Marked changes in leachate chemistry were observed, including increases in nitrate and sulphate concentrations, while concentrations of phenolics, dissolved organic carbon, potassium, iron and ammonium decreased. These changes have implications for the quality and productivity of waters draining wetlands.     

Riparian Ecosystem Management Model: Sensitivity to Soil,Vegetation, and Weather Input Parameters1

Abstract: The Riparian Ecosystem Management Model (REMM) was developed by the U.S. Department of Agriculture‐Agriculture Research Service (USDA‐ARS) and its cooperators to design and evaluate the efficiency of riparian buffer ecosystems for nonpoint source pollution reduction. REMM requires numerous inputs to simulate water movement, sediment transport, and nutrient cycling in the buffer system. In order to identify critical model inputs and their uncertainties, a univariate sensitivity analysis was conducted for nine REMM output variables. The magnitude of each input parameter was changed from ?50% to +50% from the baseline data in 12 intervals or, in some cases, the complete range of an input was tested. Baseline model inputs for the sensitivity analysis were taken from Gibbs Farm, Georgia, where REMM was tested using a 5‐year field dataset. Results of the sensitivity analysis indicate that REMM responses were most sensitive to weather inputs, with minimum daily temperature having the greatest impact on the nitrogen‐related outputs. For example, the 100% change (?50% to +50%) in minimum daily temperature input values yielded a 164.4% change in total nitrogen (N), a 109.3% change in total nitrate (NO₃), and a 127.1% change in denitrification. REMM was most sensitive to precipitation with regard to total flow leaving the riparian vegetative buffer zone (199.8%) and sediment yield (138.2%). Deep seepage (12.2%), volumetric water content (24.8%), and pore size index (6.5%) in the buffer soil profile were the most influential inputs for the output water movement. Sediment yield was most sensitive to Manning’s coefficient (46.6%), bare soil percent (40.7%), and soil permeability (6.1%). For vegetation, specific leaf area, growing degree day coefficients, and maximum root depth influenced the nitrogen related outputs. Overall results suggest that because of the high sensitivity to weather parameters, on‐site weather data is needed for model calibration and validation. The model’s relatively low sensitivity to vegetation parameters also appears to support the use of regional vegetation datasets that would simplify model implementation without compromising results.