Herbaceous Riparian Vegetation Research Articles

Changes in vegetation and soil properties following 6 years of enclosure in riparian corridors

Abstract Aims Riparian corridors play vital roles in the maintenance of biodiversity. Nonetheless, plant species diversity and vegetation coverage in riparian corridors are seriously threatened by increasing pressure owing to livestock consumption and anthropogenic disturbance; even the stability of river courses has been threatened. The establishment of enclosures is a widely used strategy to restore degraded grassland ecosystems, but its impact on degraded herbaceous riparian vegetation and soil properties remains unclear. The aim of this study was to evaluate whether species composition, richness, diversity, and soil properties can be recovered by the enclosure. Methods Twenty long-term monitoring sample plots were set in the Liaohe main stream river, Liaohe main stream river was enclosed for grazing and farmland exclusion in 2012. The height, coverage and individual numbers of plant were recorded for species richness and diversity evaluation from 2012 to 2017; soil nutrients were measured for comparative analysis in 2012 and 2017. We examined the effects of the establishment of enclosures on plant species diversity and soil properties from 2012 to 2017 in the riparian corridors of the Liaohe River system in China. Important Findings Plant species richness and diversity significantly increased from 2012 to 2017. The dominance of Asteraceae plants increased, while the abundance of Gramineae plants decreased over time. The difference in abundance increased each year since enclosure was implemented in 2012. The concentrations of phosphorus and potassium in the soil significantly decreased as a result of the combined effects of vegetation restoration and prohibition of farming practices following the establishment of enclosures. There was also a lag time related to the response of soil organic matter to the establishment of enclosures. In conclusion, our study provides new evidence regarding the response of species diversity, species composition and soil properties following riparian vegetation restoration efforts through enclosure development.

Ecology and fluvial dynamics of an Early Holocene medium‐sized European lowland river valley (Upper Scheldt, northern Belgium)

The fluvial environment of Early Holocene small‐ to middle‐sized lowland rivers in northwest Europe is mostly unstudied due to a lack of preserved and accessible deposits. A rescue excavation in the Scheldt valley in northern Belgium offered the opportunity to study a Boreal alluvial succession in detail. The results of palaeoecological and sedimentological analyses (diatoms, pollen, botanical macro‐remains, molluscs, grain size) characterize the biotic and physical environment in the middle reach of this medium‐sized river system. Although the Early Holocene in the Scheldt Basin has often been portrayed as a period of fluvial stability with marshy conditions and diffuse discharge, this study showed evidence of point bar formation by a small, low‐energy meandering river between ~9.5 and ~8.8 cal. ka BP. The point bar was at least temporarily vegetated and shows a shift from herbaceous riparian vegetation to an open willow‐dominated alluvial forest. This evidence points to a more open vegetation and a more energetic environment than traditionally described for rivers of this size and age. A link to the 9.3 ka BP cooling event is suggested and possible reasons for the scarcity of records of this type of deposits are discussed.

Environmental determinants of woody and herbaceous riparian vegetation patterns in a semi-arid mediterranean basin

What environmental variables determine riparian vegetation patterns? Are there differences between woody and herbaceous species? To answer these questions, we first explored the composition and richness patterns of both riparian woody and herbaceous species in a semi-arid mediterranean basin. Then, we assessed the environmental factors (climate, geology, topography, hydrogeomorphology and land use) that best explain these patterns. We used the following methodological approaches: clustering analyses, distance-based linear models, generalised linear models and hierarchical partitioning procedures. Valley shape, drought duration, river habitat heterogeneity, water conductivity and agricultural land use were the most important variables explaining variation in species composition for both groups. Woody riparian richness was mainly influenced by flow conditions and valley shape, whereas herbaceous one was more dependent on substrate features. Thus, although some differences in the importance of individual variables were observed, we found a notable congruence in the composition and species richness of both groups and also in the main types of variables explaining these patterns (hydrogeomorphology and land use, especially agriculture). Our results show that both communities could be treated in a holistic way, since they respond similarly to the strong natural and anthropogenic environmental gradients present in mediterranean basins.

Riparian evapotranspiration modelling: model description and implementation for predicting vegetation spatial distribution in semi‐arid environments

ABSTRACTBiotic and abiotic interactions between the riparian zone and the river determine relevant hydrological processes and exert control over riparian and bordering upland vegetation types. Vegetation growth and development are mainly controlled by water availability on semi‐arid regions, where a moisture gradient determines the transition between the densely vegetated riparian zone and the semi‐arid upland. To reproduce this spatial distribution, a mathematical model named RibAV is presented. Its conceptualization is based on the main ecohydrological modelling approaches and field expertise. The implementation of RibAV that is proposed in this paper allows the simulation of the distribution of three plant functional types [herbaceous riparian vegetation (HRV), woody riparian vegetation (WRV) and terrestrial vegetation (TV)] within the riparian zone. An evapotranspiration index (Eidx) obtained through RibAV is used as a criterion for plant absence/presence prediction. Two permanent river reaches of semi‐arid Mediterranean basins, the Terde reach (Mijares River, Spain) and the Lorcha reach (Serpis River, Spain), have been selected as case studies for the calibration and validation of the model, respectively. Several criteria based on the confusion matrix were used to analyse the efficiency of RibAV on the prediction of plant distribution. The satisfactory performance of the model establishing the distribution of the riparian vegetation types and the limit between this zone and the bordering upland are demonstrated in this paper; the strength of the Eidx to classify plant functional types in riparian semi‐arid environments is additionally proven. Copyright © 2013 John Wiley & Sons, Ltd.

Changes in the decomposition process associated with the invasion of Gleditsia triacanthos (honey locust) in pampean streams (Buenos Aires, Argentina)

Pampean streams are characterized by herbaceous riparian vegetation and a great abundance of primary producers. In the past decades, the banks of many water courses in the Pampa Ondulada (Buenos Aires, Argentina) have been invaded by Gleditsia triacanthos. Therefore, the original herbaceous vegetation has been replaced by trees, leading to possible consequences in the functioning of the system. We compared the rate of litter breakdown and the structure of the communities of zoosporic true fungi and heterotrophic straminipiles associated with the litter in sites invaded and not invaded by G. triacanthos. Litter bags with two different mesh sizes were placed at three invaded and three non-invaded sites in three streams. In the invaded sites, leaves in the bags with larger mesh size decomposed at a faster rate than those in non-invaded sites, but the community structure and species composition of zoosporic true fungi and heterotrophic straminipiles did not differ. In addition, some variables related to the particulate material were significantly different between invaded and non-invaded sites. In non-invaded sites, where fine sediments were abundant, leaf burial may have played an important role by diminishing the fragmentation of the leaves or changing the environmental conditions for detritivorous invertebrates, thus determining the slow breakdown rates observed in the non-invaded sites.

Decline of the Meadow Jumping Mouse (Zapus hudsonius luteus) in two Mountain Ranges in New Mexico

The New Mexico meadow jumping mouse (Zapus hudsonius luteus) is endemic to riparian habitats in the American Southwest. We evaluated current status and habitat of this species in the Jemez and Sacramento mountains, New Mexico. We compiled historical capture localities and conducted field surveys at historical and potential new localities during 2005 and 2006. We did not find the species or its habitat at 73% of historical localities surveyed in the Jemez Mountains and 94% of historical localities surveyed in the Sacramento Mountains. It persisted in two drainages (five localities) in the Jemez Mountains and two small, isolated localities in the Sacramento Mountains. Zapus h. luteus was associated with tall, dense, herbaceous riparian vegetation, especially areas dominated by sedges. The lower bound to the 95% confidence interval for vertical cover at localities where Z. h. luteus was captured was 63 cm. Decline in distribution was due to loss of this habitat, primarily as a result of livestock grazing. However, drought, development, recreation, forest fire, and loss of the American beaver (Castor canadensis) also contributed. We recommend that conservation of Z. h. luteus will require establishment of refugial areas of suitable habitat through protection from livestock grazing.

Regrowth and Production of Herbaceous Riparian Vegetation following Defoliation

Regrowth and Production of Herbaceous Riparian Vegetation following Defoliation

Regrowth and production of herbaceous riparian vegetation following defoliation

Stubble height regulations are frequently used to manage livestock grazing of herbaceous riparian vegetation. The objective of this study was to determine the impact of stubble height, time of clipping and soil water status on production and regrowth of herbaceous riparian vegetation. We used a randomized block design with 4 study sites on each of 3 small (< 2m width) streams in northern Harney County, Ore. In June and July of 2000–2003, 40 × 50 cm experimental plots were clipped to stubble heights of 5.1 (2 inch), 10.2 (4 inch), or 15.2 cm (6 inch), and paired control plots were left unclipped. Complete treatment sets were located adjacent to the stream and 4 m from the stream at each site. All plots were clipped to 1 cm in October and regrowth was calculated by comparing clipped and control plots. Water table depth was measured weekly using PVC wells. Results indicate that height regrowth was associated positively with stubble height (P < 0.01) and was less with July compared to June clipping (P = 0.02). Weight regrowth was also positively related to stubble height (P < 0.01) and decreased with July compared to June clipping (P = 0.04) whereas annual aboveground production increased with July clipping (P = 0.02). Annual production values for clipped plots were higher than for unclipped plots, indicating compensatory production in response to defoliation. Plots distant from the stream had less water availability, but regrowth and production were not strongly influenced by distance from active stream channel. Timing and intensity of defoliation were reliable predictors of regrowth and production performance. Most clipping height × time combinations produced end of season heights sufficient to meet current federal stubble height requirements (i.e., 10–15 cm). Our results provide insight on the timing and intensity of defoliation that will allow for adequate regrowth to meet different management objectives. However, other factors such as stream channel morphology, animal selectivity, and annual weather variation will need to be considered.

Regrowth and production of herbaceous riparian vegetation following defoliation

Abstract Stubble height regulations are frequently used to manage livestock grazing of herbaceous riparian vegetation. The objective of this study was to determine the impact of stubble height, time of clipping and soil water status on production and regrowth of herbaceous riparian vegetation. We used a randomized block design with 4 study sites on each of 3 small (< 2m width) streams in northern Harney County, Ore. In June and July of 2000–2003, 40 × 50 cm experimental plots were clipped to stubble heights of 5.1 (2 inch), 10.2 (4 inch), or 15.2 cm (6 inch), and paired control plots were left unclipped. Complete treatment sets were located adjacent to the stream and 4 m from the stream at each site. All plots were clipped to 1 cm in October and regrowth was calculated by comparing clipped and control plots. Water table depth was measured weekly using PVC wells. Results indicate that height regrowth was associated positively with stubble height (P < 0.01) and was less with July compared to June clipping (...

Regrowth and production of herbaceous riparian vegetation following defoliation

Stubble height regulations are frequently used to manage livestock grazing of herbaceous riparian vegetation. The objective of this study was to determine the impact of stubble height, time of clipping and soil water status on production and regrowth of herbaceous riparian vegetation. We used a randomized block design with 4 study sites on each of 3 small ( 2m width) streams in northern Harney County, Ore. In June and July of 2000-2003, 40 × 50 cm experimental plots were clipped to stubble heights of 5.1 (2 inch), 10.2 (4 inch), or 15.2 cm (6 inch), and paired control plots were left unclipped. Complete treatment sets were located adjacent to the stream and 4 m from the stream at each site. All plots were clipped to 1 cm in October and regrowth was calculated by comparing clipped and control plots. Water table depth was measured weekly using PVC wells. Results indicate that height regrowth was associated positively with stubble height (P &lt; 0.01) and was less with July compared to June clipping (P = 0.02). Weight regrowth was also positively related to stubble height (P &lt; 0.01) and decreased with July compared to June clipping (P = 0.04) whereas annual aboveground production increased with July clipping (P = 0.02). Annual production values for clipped plots were higher than for unclipped plots, indicating compensatory production in response to defoliation. Plots distant from the stream had less water availability, but regrowth and production were not strongly influenced by distance from active stream channel. Timing and intensity of defoliation were reliable predictors of regrowth and production performance. Most clipping height × time combinations produced end of season heights sufficient to meet current federal stubble height requirements (i.e., 10-15 cm). Our results provide insight on the timing and intensity of defoliation that will allow for adequate regrowth to meet different management objectives. However, other factors such as stream channel morphology, animal selectivity, and annual weather variation will need to be considered.

Do rare species have any place in multivariate analysis for bioassessment?

Cao et al. (2001) have recently published an assessment of the place of rare species in multivariate analyses associated with bioassessment. This assessment follows their earlier comments on this subject (Cao et al. 1998, Cao and Williams 1999) and criticism of their viewpoint (Marchant 1999). In their earlier comments Cao et al. (1998) claimed that elimination of rare species from data sets unduly biases the similarity measures used in multivariate analyses of community composition and results in an ‘‘unacceptable loss of ecological information’’. Marchant (1999) refuted this claim by noting that when rare taxa are eliminated from data sets the trends displayed by multivariate analyses are unaltered and that benthic data sets, both from freshwater and marine habitats, commonly contain much redundant information. If, as Cao et al. (1998) claimed, rare species are vital for multivariate analysis, then logically the less rare species and the common species must also be vital. In other words, all species are vital and, as Marchant (1999) noted, this amounts to saying that no redundancy exists. Such a claim is contrary to common experience. Cao et al. (2001) admitted that rare species may not be important when environmental gradients are strong. However, they suggested that rare species respond to different gradients, perhaps less important and subtle ones or those related to human impacts. They provided little evidence from the literature that such situations exist but they quoted a paper by Faith and Norris (1989) as supporting this view. Faith and Norris (1989) reanalyzed a study conducted in the La Trobe catchment of eastern Victoria, Australia (Metzeling et al. 1984, Marchant et al. 1985). Using all 269 taxa (mostly at genus or species level) Faith and Norris (1989) compared ordinations with and without rare taxa, as well as ordinations based solely on rare taxa (those with total abundances ,0.5% of the total abundance of all taxa). They showed that inclusion of rare taxa resulted in a greater number of sig-

GRASS VERSUS TREES: MANAGING RIPARIAN AREAS TO BENEFIT STREAMS OF CENTRAL NORTH AMERICA1

ABSTRACT: Forestation of riparian areas has long been promoted to restore stream ecosystems degraded by agriculture in central North America. Although trees and shrubs in the riparian zone can provide many benefits to streams, grassy or herbaceous riparian vegetation can also provide benefits and may be more appropriate in some situations. Here we review some of the positive and negative implications of grassy versus wooded riparian zones and discuss potential management outcomes. Compared to wooded areas, grassy riparian areas result in stream reaches with different patterns of bank stability, erosion, channel morphology, cover for fish, terrestrial runoff, hydrology, water temperature, organic matter inputs, primary production, aquatic macroinvertebrates, and fish. Of particular relevance in agricultural regions, grassy riparian areas may be more effective in reducing bank erosion and trapping suspended sediments than wooded areas. Maintenance of grassy riparian vegetation usually requires active management (e.g., mowing, burning, herbicide treatments, and grazing), as successional processes will tend ultimately to favor woody vegetation. Riparian agricultural practices that promote a dense, healthy, grassy turf, such as certain types of intensively managed livestock grazing, have potential to restore degraded stream ecosystems.