Black Willow Cuttings Research Articles

Root Porosity Changes in Salix nigra Cuttings in Response to Copper and Ultraviolet-B Radiation Exposure

Cuttings of black willow (Salix nigra), a naturally occurring wetland species, are used for restoration and streambank stabilization. As an adaptation to their wetland habitat, this species develops aerenchyma tissue to avoid root anoxia. To determine the effects of combined copper and ultraviolet-B radiation exposure on aerenchyma tissue (measured as root porosity), black willow cuttings were grown hydroponically and exposed to three ultraviolet-B (UV-B) intensities and three Cu concentrations in a completely randomized 3 × 3 factorial design. While both UV-B (F2,42 = 11.45; p = 0.0001) and Cu (F2,42 = 6.14; p = 0.0046) exposure increased root porosity, total biomass decreased in response to both UV-B (F2,43 = 3.36; p = 0.0441) and to Cu (F2,43 = 4.03; p = 0.0249). Root biomass decreased only in response to Cu (F2,41 = 3.41; p = 0.0427) resulting in a decrease in the root/shoot ratio (F2,42 = 3.5; p = 0.0393). Copper exposure also resulted in a decrease in the number of leaves/shoot (F2,42 = 7.03; P = 0.0023). No UV-B and Cu interaction was found. While the present research indicates the negative effects of Cu contamination and elevated UV-B intensities on S. nigra, it also points out potential mechanisms that S. nigra uses to alleviate these stresses.

Photosynthetic gene expression in black willow under various soil moisture regimes

This study was the first attempt to extract RNA from black willow (Salix nigra Marshall) that contains numerous secondary products and to examine the photosynthetic gene expression of black willow under a wide range of soil moisture regimes. Black willow cuttings were grown under control, continuous flooding, periodic flooding and periodic drought for 42 d. A modified lithium chloride precipitation method was used for RNA extraction. Results of real-time polymerase chain reaction showed reduced gene expression of oxygen evolving complex, large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenasse and ferredoxin on day 7 as well as the latter two on day 14 in response to flooding. Therefore, decreased expression of these three genes may have contributed to the observed reduced photosynthetic capacity in response to flooding.

BLACK WILLOW CUTTING SURVIVAL IN STREAMBANK PLANTINGS, SOUTHEASTERN UNITED STATES1

ABSTRACT:Field studies were conducted on black willow (Salix nigra) cuttings planted for riparian zone restoration along Harland Creek, Twentymile Creek, and Little Topashaw Creek in Mississippi, USA. Planted cuttings were 2.5 to 3 m long and had base diameters of 2.5 to 7.5 cm. Streams were unstable, deeply incised sand bed channels with eroding banks 1 to 6 m high. Soil texture, redox potential (Eh), depth to water table, and willow survival were monitored for two to three years after planting. While many factors influence willow cuttings at restoration sites, soil texture and moisture are key to plant success. In these studies, plant survival and growth were best for cuttings planted in soils with less than 40 percent silt‐clay content and a water table 0.5 m to 1.0 m below the soil surface during the growing season. These conditions produced soil Eh greater than approximately 200 mV and were most often observed 1 to 2 m higher than the bank toe. These findings suggest criteria useful for preplanting site evaluations. Additional evidence suggests that preplanting soaking enhances performance of black willow cuttings. Additional factors (channel erosion, herbivory by beaver, and competition from exotics) may control performance over periods longer than two to three years.

Partial flooding enhances aeration in adventitious roots of black willow (S alix nigra) cuttings

Black willow (Salix nigra) cuttings are used for streambank stabilization where they are subjected to a range of soil moisture conditions including flooding. Flooding has been shown to adversely impact cutting performance, and improved understanding of natural adaptations to flooding might suggest handling and planting techniques to enhance success. However, data assessing the root aeration in adventitious roots that are developed on cuttings of woody species are scant. In addition, it appears that no data are available regarding aeration of the root system under partially flooded conditions. This experiment was designed to examine the effects of continuous flooding (CF) and partial flooding (PF) on aerenchyma formation and radial oxygen loss (ROL) in black willow cuttings. Photosynthetic and growth responses to these conditions were also investigated. Under laboratory condition, replicated potted cuttings were subjected to three treatments: no flooding (control, C), CF, and PF. Water was maintained above the soil surface in CF and at 10 cm depth in PF. Results indicated that after the 28-d treatments, root porosity ranged between 28.6% and 33.0% for the CF and C plants but was greater for the PF plants (39.2% for the drained and 37.2% for the flooded portions). A similar response pattern was found for ROL. In addition, CF treatment led to decreases in final root biomass and root/shoot ratio. Neither CF nor PF had any detectable adverse effects on plant gas exchange or photosystem II functioning. Our results indicated that S. nigra cuttings exhibited avoidance mechanisms in response to flooding, especially the partially flooded condition which is the most common occurrence in riparian systems.

A dormancy extension technique for biotechnical streambank stabilization in warm regions

Researchers identified four challenges to applying biotechnical streambank stabilization in warm regions. These challenges are strongly correlated to plant dormancy and planting period. Prompted by these challenges, researchers investigated the applicability of using the cold storage method to extend the dormant condition of live black willow (Salix nigra) cuttings for later planting. Black willow cuttings were harvested in February 2001 and stored in a refrigerator at 4.4 °C (40 °F). These cold-stored cuttings had survival rates of 81.3, 43.6, and 43.8% when they were planted in the field in March, April, and May 2001, respectively. These rates are considered satisfactory in biotechnical engineering. A cost analysis suggests that using cold storage in field conditions is feasible.

A dormancy extension technique for biotechnical streambank stabilization in warm regions

Researchers identified four challenges to applying biotechnical streambank stabilization in warm regions. These challenges are strongly correlated to plant dormancy and planting period. Prompted by these challenges, researchers investigated the applicability of using the cold storage method to extend the dormant condition of live black willow ( Salix nigra) cuttings for later planting. Black willow cuttings were harvested in February 2001 and stored in a refrigerator at 4.4 °C (40 °F). These cold-stored cuttings had survival rates of 81.3, 43.6, and 43.8% when they were planted in the field in March, April, and May 2001, respectively. These rates are considered satisfactory in biotechnical engineering. A cost analysis suggests that using cold storage in field conditions is feasible.

High Oxygen Level in a Soaking Treatment Improves Early Root and Shoot Development of Black Willow Cuttings

Black willow (Salix nigra) stem cuttings are commonly used to stabilize eroded streambanks with survival dependent on rapid development of adventitious roots to maintain plant water balance, absorb nutrients, and provide anchorage and support especially during flood and drought events. Soaking cuttings in water prior to planting increases survival and growth rates, but it is not known whether oxygen content in the soaking water affects the rate of early root and shoot initiation and growth. A laboratory experiment tested the hypothesis that cuttings treated with high oxygen (>95% saturation, 8.62 mg O2 l—-1) soaking exhibit more rapid initiation and growth of roots and shoots than cuttings treated with low oxygen (<15% saturation, 1.24 mg O2 l-1) soaking and control (unsoaked). Root initiation was enhanced in both high and low O2 soaking treatments compared to control (100, 93, and 41%, respectively, n = 27). High O2 soaking led to greater root length than low O2 soaking during the fourth week after planting (26.5 and 12.3 cm on day 22; 27.7 and 19.1 cm on day 27, respectively). Shoot growth was greater in high O2 compared to low O2 soaking on days 36 and 56 after planting (9.3 and 6.3 cm on day 36, 10.7 and 7.2 cm on day 56, respectively). Shoot and root biomass production was stimulated in both soaking treatments, with 200% more biomass production by day 59 compared to control. Results of this study demonstrated that a high oxygen soaking treatment has potential for improving early root and shoot growth, and survival in willow cuttings planted at riparian restoration sites.

Effects of soil conditions on survival and growth of black willow cuttings.

Current streambank restoration efforts focus on providing bank stability, enhancing water quality, and improving woody habitat using native vegetation rather than traditional engineering techniques. However, in most cases harsh site conditions limit restoration success. A two-year field study was conducted at Twentymile Creek, in northern Mississippi, investigating edaphic factors governing the survival of black willow (Salix nigra) cuttings used for streambank restoration. Low height growth, above-ground biomass production, and average leaf area were observed in willow cuttings grown in plots subjected to moisture deficits. However, sediment texture emerged as the dominant factor determining willow post growth, health, and survival. Shoot biomass, leaf biomass, and total above-ground biomass were 15-, 10-, and 14-fold greater for large willow cuttings (posts) grown in plots with sandy sediments relative to those grown in plots with similar moisture and soil redox potential but with silt and clay sediments. Average leaf size, average leaf mass and specific leaf area were all lower in fine textured plots. Under moisture conditions present at our sites, coarse-grained sediment (sand) was more conducive to willow growth, biomass production, and survival than were fine-grained sediments (silt/clay). Our results strongly suggest that soil texture and moisture conditions can determine restoration success. Therefore, it is critical that site conditions are factored into the selection of project locations prior to the initiation of willow planting restoration projects.

Effects of Pre‐Planting Soaking on Growth and Survival of Black Willow Cuttings

AbstractBlack willow (Salix nigra) uses periodic flood events for dispersal of vegetative propagules, subjecting them to periods of soaking before their deposition along the streambank. It was hypothesized that this life history trait results in optimal conditions for willow growth and survival. To test this hypothesis, a greenhouse experiment was conducted using 1.2‐m‐long black willow cuttings (posts) with a basal diameter of 5 cm. Cuttings were subjected to three soaking treatments (0, 3, and 10 days) and then grown under four soil moisture regimes (control, drought, permanently flooded, and intermittently flooded). Growth, biomass, and survival were recorded. Results showed that soaking posts for 10 days was most beneficial in the control soil moisture regime, enhancing root, shoot, leaf, and total biomass production. Shoot abundance and growth were also enhanced by 10 days of soaking in the control and permanently flooded moisture regimes. Finally, survival increased significantly in control and drought moisture regimes in response to the 10‐day soaking treatment. Results clearly demonstrated that soaking had significant effects on willow post success when evaluated across all soil moisture regimes. Posts subjected to the 10‐day soaking treatment consistently had greatest growth and biomass and displayed a doubling of the survival rate. Therefore, soaking willow cuttings before planting is a simple, inexpensive technique that may be used to bolster streambank restoration success.