排序方式: 共有11条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Small and impoverished regional species pools constrain colonisation of restored river reaches by fishes 总被引:1,自引:0,他引:1
STEFAN STOLL ANDREA SUNDERMANN ARMIN W. LORENZ JOCHEM KAIL PETER HAASE 《Freshwater Biology》2013,58(4):664-674
1. Using an extensive data set from 18 river restoration projects in the lower mountain ranges of Germany and 5462 river reaches in their surroundings, we estimated the spatial extent of the regional fish species pool from which restored river reaches are colonised. 2. Restoration resulted in a marginally significant increase in fish species richness; however, restored reaches still deviated markedly from natural reference conditions. Nearly all (96.6%) species occurring in restored reaches were present in reaches within a distance of 5 km up‐ or downstream of the restored reach. 3. Species richness in restored reaches was correlated with species richness within a 5‐km species pool. This relationship was more pronounced for common than for rare fishes and applied to both the total number of fish species at the restored reach and the number of additional fish species that were not present at unrestored conditions. 4. The richness of the regional species pools was greatly impoverished. On average, only 50% of all species considered to represent natural reference assemblages were present. The limited success in establishing natural fish assemblages in restored reaches was attributed to spatial limitation (e.g. due to fragmentation) and an impoverished regional species pools from which restored reaches recruit. 5. We recommend that integrated river restoration management should consider not only the abiotic prerequisites of successful restorations, but also the structure and quality of the regional species pool. 相似文献
6.
XINYOU YIN PAUL C. STRUIK PASCUAL ROMERO JEREMY HARBINSON JOCHEM B. EVERS PETER E. L. VAN DER PUTTEN & JAN VOS 《Plant, cell & environment》2009,32(5):448-464
We appraised the literature and described an approach to estimate the parameters of the Farquhar, von Caemmerer and Berry model using measured CO2 assimilation rate (A) and photosystem II (PSII) electron transport efficiency (Φ2). The approach uses curve fitting to data of A and Φ2 at various levels of incident irradiance (Iinc), intercellular CO2 (Ci) and O2. Estimated parameters include day respiration (Rd), conversion efficiency of Iinc into linear electron transport of PSII under limiting light [κ2(LL)], electron transport capacity (Jmax), curvature factor (θ) for the non‐rectangular hyperbolic response of electron flux to Iinc, ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco) CO2/O2 specificity (Sc/o), Rubisco carboxylation capacity (Vcmax), rate of triose phosphate utilization (Tp) and mesophyll conductance (gm). The method is used to analyse combined gas exchange and chlorophyll fluorescence measurements on leaves of various ages and positions in wheat plants grown at two nitrogen levels. Estimated Sc/o (25 °C) was 3.13 mbar µbar?1; Rd was lower than respiration in the dark; Jmax was lower and θ was higher at 2% than at 21% O2; κ2(LL), Vcmax, Jmax and Tp correlated to leaf nitrogen content; and gm decreased with increasing Ci and with decreasing Iinc. Based on the parameter estimates, we surmised that there was some alternative electron transport. 相似文献
7.
8.
9.
10.