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River restoration projects often involve vegetation planting to retain sediment and stabilize riverbanks. Laboratory experiments have explored the impact of rigid emergent vegetation canopies on bed morphology. Inside canopies, bed erosion is attributed to vegetation‐induced turbulent kinetic energy (TKE). Based on the in‐canopy local TKE and the criteria for sediment movement, a method is established and validated for predicting the length of the bed erosion region. In the bare channel, bed erosion is related to the ratio of canopy length to flow adjustment distance, L/LI, and exhibits two trends. At L/LI < 1, the maximum depth, ds(bare), and length, Ls(bare), of the bed erosion region increase with increasing canopy length. At L/LI ≥ 1, ds(bare) and Ls(bare) are not influenced by the canopy length and remain constant. In vegetated regions with the same length and plant density, discontinuous canopies (streamwise interval s ≥ canopy width D) yield weaker bed erosion than continuous canopies. The mutual influence between two canopies must be considered if the canopy interval satisfies s < 3D. These results provide insights for designing vegetation canopies for river restoration projects. Key Points The impact of canopy length on bed morphology inside and outside the canopy is clarified A method for predicting the length of the bed erosion region inside canopies is established Discontinuous canopies produce weaker bed erosion than continuous canopies for the same vegetated region length and plant density

The escape probability of Solar-induced chlorophyll fluorescence (SIF) can be remotely estimated using reflectance measurements based on spectral invariants theory. This can then be used to correct the effects of canopy structure on canopy-leaving SIF. However, the feasibility of these estimation methods is untested in heterogeneous vegetation such as the discontinuous forest canopy layer under evaluation here. In this study, the Discrete Anisotropic Radiative Transfer (DART) model is used to simulate canopy-leaving SIF, canopy total emitted SIF, canopy interceptance, and the fraction of absorbed photosynthetically active radiation (fAPAR) in order to evaluate the estimation methods of SIF escape probability in discontinuous forest canopies. Our simulation results show that the normalized difference vegetation index (NDVI) can be used to partly eliminate the effects of background reflectance on the estimation of SIF escape probability in most cases, but fails to produce accurate estimations if the background is partly or totally covered by vegetation. We also found that SIF escape probabilities estimated at a high solar zenith angle have better estimation accuracy than those estimated at a lower solar zenith angle. Our results show that additional errors will be introduced to the estimation of SIF escape probability with the use of satellite products, especially when the product of leaf area index (LAI) and clumping index (CI) was underestimated. In other results, fAPAR has comparable estimation accuracy of SIF escape probability when compared to canopy interceptance. Additionally, fAPAR for the entire canopy has better estimation accuracy of SIF escape probability than fPAR for leaf only in sparse forest canopies. These results help us to better understand the current estimation results of SIF escape probability based on spectral invariants theory, and to improve its estimation accuracy in discontinuous forest canopies.

Plant canopies can be considered as assemblages of leaves, stems and fruits growing in zones of differing irradiance demarcated by contours of mean irradiance as measured on a horizontal surface. The following general equations have been derived to calculate the leaf area (LI) and the canopy volume (CVI) in zones external to any chosen contour of mean irradiance: (1) LI = ((1nl)/(−K)(I−Tf) or leaf area index (LAI) if this is less (2) CVI = LI/(leaf area density m2 m−2), where I is the specified value of irradiance (horizontal surface) expressed as a decimal fraction of that above the canopy, K is the appropriate extinction coefficient and Tf is the proportion of the total of available radiation which, if the canopy is discontinuous, would reach the ground by passing through gaps between the discrete canopy units. Where the canopy is continuous Tf is zero so expression (1) simplifies to L1 = 1n I/−K (or LAI if this is less). For a range of model hedgerow orchards of varying dimensions, spacings and LAIs, it has been shown that the use of these equations gives very similar results to those obtained by detailed calculation of light penetration. They therefore seem to be of potential use in calculating both potential dry-matter production by discontinuous canopies of any type and, in the case of orchard fruit crops, the potential effect of changes in tree size, leaf area density, spacing etc. on the canopy volume in which irradiation is adequate for fruit bud initiation and fruit colour development.