Natural History of Ecological Restoration

Tag: Mycorrhizae

  • Land Abandonment, Succession, and Restoration: The Wolf Run Grassland Restoration Project at the Missouri Botanical Garden’s Shaw Nature Reserve

    Land Abandonment, Succession, and Restoration: The Wolf Run Grassland Restoration Project at the Missouri Botanical Garden’s Shaw Nature Reserve

    By: Mike Saxton and Calvin Maginel

    Mike Saxton (mike.saxton@mobot.org) is the Manager of Restoration and Land Stewardship, and Calvin Maginel (cmaginel@mobot.org) is the Ecological Resource Scientist at Shaw Nature Reserve. 

    Since 1950, over 1-billon acres of agricultural land have been abandoned worldwide. In certain landscape contexts, unassisted spontaneous recovery of high levels of native biodiversity in abandoned fields is possible while in others, like the Midwest USA, fallow fields rarely develop into biologically rich habitats. To achieve the ambitious goals of the UN Decade of Ecosystem Restoration, land managers and ecologists need to better understand how to assist the regeneration and ecological restoration of these highly altered landscapes. 

    In 1925, the Missouri Botanical Garden purchased 1,300 acres of battered farm ground in Gray Summit, MO – approximately 35 miles (56 km) west of St. Louis – to escape the deleterious impact urban air pollution was having on horticultural collections in St. Louis City. The intended uses of this acreage were to: (1) propagate and grow plants, trees, and shrubs for the main Garden’s displays and (2) establish an arboretum focusing on woody plant collections. The site was officially named the Shaw Arboretum in 1933. After decades of development, many non-essential operations at the Arboretum were eliminated in 1958 and many fields were abandoned to allow spontaneous successional change. In 2000, the Shaw Arboretum was renamed Shaw Nature Reserve to reflect its contemporary mission to demonstrate, test, and inspire responsible stewardship practices through education, restoration, and protection of natural habitats and public enjoyment of the natural world. Today the Nature Reserve consists of 2,400 acres of varied habitat in various stages of restoration and revised management, including the use of prescribed fire.  

    Prior to European settlement, the natural plant communities and ecosystems of the area were fire adapted, open oak-hickory woodlands and xeric glades with gallery forests along riparian corridors. Post-settlement, woodlands were clear-cut with some woodlots left to passively regenerate while others were converted to row crop agriculture. 

    Wolf Run Grassland Restoration 

    In 2016, Nature Reserve staff set an ambitious goal to bring all 2,400 acres of the site into active management to promote native biodiversity by the year 2030. This effort will include restoring open pastures and former row crop fields, a relatively simple process. A much more challenging effort will be reclaiming 120 acres of old fields with 60+ year successional development, which is our current Wolf Run Grassland Restoration project. The 120 acre project area was initially “wasted farm ground” that had erosion gullies “where a freight train could pass without you seeing it”, according to August Beilmann, former Arboretum Director from 1941 to 1956. The entire project area was re-sculpted and smoothed by a bulldozer in 1953 and then converted to bluegrass (Poa pratensis). “Every piece of this land that looks so likely to be just right was laboriously rebuilt,” said Beilmann in a 1974 interview.

    Wolf Run Grassland Restoration project area in ca. 1945 showing open fields (light green) maintained through cattle grazing and mowing with trees occupying wet-weather streams and ditches (dark green). Photo: MBG Archives.

    Since 1958 when areas including the Wolf Run Grassland Restoration were removed from mowing and grazing, the site was encroached upon and became dominated by eastern red cedar (Juniperus virginiana), the non-native invasive shrubs Amur honeysuckle (Lonicera maackii), and border privet (Ligustrum obtusifolium), as well as slippery elm (Ulmus rubra), shingle oak (Quercus imbricaria) and ash (Fraxinus) species, the latter of which which are in severe decline due to the emerald ash borer. 

    These degraded woodlands had little native ground flora and were highly infested with non-native shrubs. Tree abundance and species composition had no historic analog. When setting ecological restoration goals for the area, staff determined that much of the site could not be managed as an open oak-hickory woodland, which would have existed at the site pre-settlement.  A new vision was needed. 

    Goals for the Wolf Run Grassland Restoration project

    • Establish a mosaic of 80 acres (~32 ha) of prairie, 15 acres (~6 ha) of savanna and 25 acres (~10 ha) of oak-hickory woodlands
    • Maximize native flora diversity and aggressively control invasive shrub species 
    • Manage with periodic, dormant-season prescribed fire 

    In 2021, Nature Reserve staff marked hundreds of native trees to retain including white, red, bur and black oaks (Quercus alba, Q. rubra, Q. macrocarpa, Q. velutina) and shagbark hickory (Carya ovata) and bitternut hickory (C. cordiformis). Drainages and wet weather streams were left with a 50 ft. (~15 m)  untreated buffer zone while a perennial creek flowing through the unit retained a 150 ft. (~46 m) untouched buffer. A logger removed unmarked trees from the area, with the commercial value of the timber offsetting the cost of the removal. Following US Fish and Wildlife Service recovery management guidelines for the Indiana bat (Myotis sodalis) — a federally endangered species — trees were only removed from November 1st to April 1st.

    Wolf Run Grassland Restoration project area pre-thinning (2021), approximately 60 years after land abandonment. Note the dark green areas are dominated by eastern red cedar (Juniperus virginiana), a native tree that rapidly colonizes abandoned or disturbed lands in the Midwest. Historically, this fire-sensitive tree species primarily occurred on rocky outcrops and bluffs that served as refugia from periodic fires that were common in the pre-European settlement landscape. Photo: ESRI
    Wolf Run Grassland Restoration project area post-thinning (2023). Photo: ESRI
    Forestry contractor equipment was used to remove most woody biomass greater than 4.5 in. (~11 cm) in diameter and left behind mostly small-diameter slash. A bulldozer was used to collect the debris into 600 piles that were subsequently burned. Photo: Mike Saxton

    The Restoration team has spent the last 9 months focusing on the removal of stumps for the project area. Stumps can be a substantial hazard for vehicles, equipment and staff safety. To seed native species and effectively manage the area for invasive species in perpetuity, the stumps must be ground down or cut flush to the ground.

    Skid loader mounted stump grinder removing stumps. Photo: M. Saxton

    Concurrent to this effort has been the site preparation step of chemically treating all of the invasive species and the disturbance driven annual vegetation that emerged post-land clearing [primarily fireweed (Erechtites hieraciifolius), mare’s tail (Erigeron canadensis), ragweed (Ambrosia artemisiifolia) and fox tail (Setaria pumila)]. This step is necessary because diverse, healthy native plant communities have not existed in these areas in more than 100 years. Consequently, there is no native seedbank to support the unassisted spontaneous recovery of native perennial herbaceous species in these highly degraded acres. 

    In areas where stumps have not been cleared, traditional equipment (tractor boom sprayers and UTV mounted spray rigs) for applying herbicide are ineffective. The Nature Reserve hired a contractor that specializes in drone-assisted aerial herbicide applications. The drone flies 12 ft. (~37 m) above vegetation and can self-navigate around trees and other hazards. The unit carries a total of 8 gallons (~30 L) and sprays approximately 3 gallons of herbicide per acre. The effective width of each pass is 25 ft. (~8 m). A single battery powers the drone, with a flight time of 7.5 minutes and a re-charge time of 6 minutes. When the herbicide tank runs out, the drone re-deploys to the fill up location, is refilled by the contractor, and then returns to where it left off. 

    Aerial drone sprayer used to eliminate undesirable vegetation. Photo: M. Saxton

    The last step after the undesirable trees have been removed, biomass/debris has been burned, the stumps have been ground and invasive species have been controlled, is the final ground preparation. Currently, in 2023, we are again smoothing out erosion gullies and clearing away the last remnants of woody debris with a bulldozer. This effort will ensure effective seed-to-soil contact when we sow native seed in January 2024 and will enhance our ability to successfully search for invasive species in the coming years by eliminating deep ruts and rills.  

    Above: Bulldozer in 1953 eliminating erosion rills in Wolf Run Grassland Restoration project area. Below: Bulldozer completing site preparation for native seed addition (2023).  Top Photo: St. Louis Globe Democrat, Bottom Photo: M. Saxton

    Native Seeding and Experimentation to promote Biodiversity Recovery 

    During the growing season of 2023, the Restoration team at the Nature Reserve has been feverishly collecting seed for this 2024 seeding effort. More than 1,100 lbs. (~500 kg) of bulk, milled seed from ~200 locally collected native tallgrass prairie and open oak-hickory woodland species will be used in the restoration planting. Additionally, these acres are enrolled in the Environmental Quality Incentives Program, EQIP – part of the Natural Resources Conservation Service, and we must purchase viability-tested seed to meet the minimum required specifications of the contract. The hand-collected seed together with the pure live seed (PLS) – percentage of viable seed in a seed lot – purchased from commercial vendors will provide us with ample species and volume of seed to effectively cover the 40 acres (~16 ha) to be planted this winter. 

    Concurrent with the preparation effort, we initiated a research study, which will help inform our work and the broader research community on plant recruitment amongst scraped soils that have been inoculated with mycorrhizal fungi and those that have not. This study includes paired species from the same genus that have different CC-values, short for coefficients of conservatism, which represents a species’ tolerance of environmental degradation, or its fidelity to intact remnant or long-restored habitats, as determined by local botanical experts. Ecologists generally expect species that are dependent on stable intact communities (higher CC-values) to be more reliant on mycorrhizae connections to establish and flourish. Species with high CC-values tend to establish poorly in restoration sites, which is one of the reasons to pursue this study. Some examples from the ten herbaceous pairs of native species include sedges (Carex bushii [CC = 4] and Carex bicknellii [CC = 10]), grasses (Sporobolus compositus [CC = 3] and Bouteloua curtipendula [CC = 7]), and forbs (Oligoneuron rigidum [CC = 5] and Oligoneuron album [CC = 9]).

    We added all 20 species at the same rate of pure live seed to provide each species an equal opportunity to establish. Initial analyses after one growing season indicate that low CC-value species germinated more successfully, producing more seedlings and greater percent cover than the high CC-value species, regardless of inoculation. We expect the addition of mycorrhizal fungi to have the greatest effects on species during the first couple of years after germination. If the mycorrhizae associate with the roots of the high-CC species more than the low-CC species, this may help them grow faster or be more resistant to future stress. Future monitoring will show us if there are long-term effects of inoculation.

    To check for updates on restoration activities and results from experimental studies, please visit our webpage.

    Barrels of hand-collected seed connected to a seed dryer, which pumps air through tubes into the barrels to eliminate mold & moisture. Photo: M. Saxton
  • Homemade mycorrhizal inoculum improves seedling growth for some native Malagasy trees

    Homemade mycorrhizal inoculum improves seedling growth for some native Malagasy trees

    MBG Madagascar’s Chris Birkinshaw and Dinasoa Tahirinirainy describe exciting, preliminary results from a forest restoration experiment in highland Madagascar.

     

    Ankafobe Forest on Malagasy highlands - experiment located on grassy ridges
    This sliver of riparian forest is one of the last vestiges of Madagascar’s highland forests. Decades of Missouri Botanical Garden research in Madagascar have shown that more than 80% of all plant species on the island exist nowhere else. Many are threatened with extinction due to habitat loss. Several previous posts have described forest restoration efforts at this site, home to the largest population of the endemic sohisika tree (Schizolaena tampoketsana) – a species that belongs to a family (Sarcolanaceae) that only exists on Madagascar.

    A small number of forest restoration projects in Madagascar routinely inoculate the tree seedlings in their nurseries with a homemade mycorrhizal inoculum. While the nurserymen are convinced that this technique promotes growth and survival of tree seedlings, there seems to be no published data objectively demonstrating these positive outcomes. In an effort to provide the evidence to justify investment in this technique, we designed a simple experiment that will compare the survival and growth under four treatments of young plants of six native trees planted in grassland adjacent to the Ankafobe Forest on the central Malagasy highlands.

    Table – Four experimental treatments to test the effects of mulch and mycorrhizal inoculum on native tree seedling growth in highland Madagascar

      Inoculated Not inoculated
    Mulched Treatment 1 Treatment 2
    Not mulched Treatment 3 Treatment 4 (control)

    In our experiment, fifteen seedlings of each of six native tree species will be grown under each of the four treatments listed above. The mycorrhizal inoculum was made by filling a pit (150 cm long × 50 cm wide × 30 cm deep) lined with sacks with topsoil collected from around the roots of three native tree species, then growing maize and beans in this soil for three months before cutting these plants down and letting the substrate dry out for two weeks. The substrate remaining in the pit is the inoculum and was used by adding one tablespoon to each seedling container.

    Making the inoculum
    Beans and maize are grown in topsoil collected from a remnant forest to amplify local mycorrhizae populations. This enriched soil (i.e., inoculum) is then added to seedling containers.

    The tree seedlings that received mycorrhizal enrichment were inoculated in November 2017, and all of the seedlings were otherwise grown under the same conditions in the nursery until January 2018 when they were planted out into an experimental plot at Ankafobe. Half of the tree seedlings were surrounded by a thick layer of grass-based mulch (~30-cm deep). The comparison of seedling performance with and without the addition of mulch is interesting because of the possibility that mulch helps to maintain a relatively cool and moist environment in which the mycorrhizae can flourish.

    Table – Mean difference in tree seedling height (cm) between seedlings inoculated versus not inoculated with homemade mycorrhizae, after two months in the nursery (N = 30 seedlings per species).

    Species Inoculated seedling height Non-inoculated seedling height t p1
    Aphloia theiformis 29.5 ± 10.2 33.4 ± 6.5 -1.75 1.0000
    Baronia tarantana 18.1 ± 6.1 11.4 ± 3.5 5.21 <0.0001
    Brachylaena ramiflora 27.2 ± 6.0 31.8 ± 6.5 -2.87 1.0000
    Craspidospermum verticillatum 43.0 ± 5.9 42.6 ± 3.7 0.37 1.0000
    Macaranga alnifolia 34.8 ± 8.6 39.2 ± 5.2 -2.43 1.0000
    Uapaca densifolia 23.0 ± 7.9 11.5 ± 2.6 7.58 <0.0001

    1 t and p values are from a one-tailed student’s t-test asking whether inoculated seedling height was greater than non-inoculated seedling height. P values are adjusted for multiple comparisons with Bonferroni correction.

    Although we plan to measure seedling survival and growth 12 months from the time when they were planted (i.e., in January 2019), we were interested to see that for two of the species the height of inoculated seedlings was significantly greater than the height of non-inoculated seedlings after a mere two months in the nursery. On average, inoculated seedlings of Baronia tarantana are 1.6× taller than non-inoculated seedlings; while the seedlings of Uapaca densifolia are a full 2× taller. For the other species there was no significant difference between the height of the inoculated and non-inoculated plants.

    Experiment showing line of seedlings some with and some without mulch (1)
    Tree seedlings are planted out in a field experiment at Ankafobe in January 2018. These seedlings are planted adjacent to a line of “green manure” (i.e., nitrogen-fixing Tephrosia shrubs planted to improve the degraded highland soil prior to planting native tree seedlings).

     

  • Can fungus help grow trees in Madagascar?

    Can fungus help grow trees in Madagascar?

    Thomas Timberlake and Cyprien Miandrimanana write from Madagascar about a field experiment using fungus to help tree seedlings survive.

    One of the problems that has long bedeviled ecological restoration efforts in Madagascar is persuading young seedlings to grow at a pace of more than just a few centimetres per year. The site of Ankafobe in the central highlands is a prime example, with many five year old individuals, planted in the anthropogenic grassland surrounding the remaining forest fragments, still no taller than waist height. Clearly, the environment into which the seedlings are planted is in some way inhospitable.  One hypothesis to explain seedling underperformance  is that they are not managing to establish their normal symbiotic relationships with vesicular arbuscular mycorrhizae (VAM) fungi on which most higher plants depend.

    Scaled visual comparison of VAM and VAM-less seedlings at Mitsinjo in Andasibe, Madagascar.
    Scaled visual comparison of VAM and VAM-less seedlings at Mitsinjo in Andasibe, Madagascar.

    In a VAM symbiosis, plants exchange a significant carbohydrate donation to the fungus in return for important nutrients, particularly phosphorus, and often increased drought tolerance. So if mycorrhizae propagules are absent in the savanna soil, this could well explain the slow growth rates and high mortality observed among planted tree seedlings at sites like Ankafobe.

    In response to concern about poor seedling performance, various restoration projects in Madagascar have begun inoculating their nursery seedlings with VAM using a simple protocol pioneered by Mitsinjo, a restoration project in the eastern rain forest of Andasibe. Soil (presumed to contain mycorrhizal fungus) is gathered from underneath forest trees, mixed with sand in a sack-lined pit and then sown with rice and beans to act as hosts for the developing VAM. After three months of maturation, you have a sack-full of VAM inoculum, ready to be applied to the young germinating seedlings – one teaspoon per plant.

    Many groups in Madagascar swear by the VAM protocol and the visual results can be compelling, but as yet there have been no experiments in the country to rigorously test whether this method is actually effective. This lack of clear evidence is what prompted us to work on a series of experiments testing and perhaps refining the VAM protocol.

    We planted 480 native tree seedlings with and without VAM inoculation to test whether this method increases seedling survival and growth in the degraded savanna around Ankafobe. Digging into the solid laterite and planting the experimental seedlings was hard work but our efforts were rewarded one day with the sighting of a family of 10 young Tenrecs (Tenrec ecaudatus) who ventured bravely out of the security of the forest to observe the progress.

    Planting complete, we took our “Time Zero” measurements and then a small sample of roots from both VAM and control seedlings to return to Antananarivo and check for the presence of mycorrhizae vesicles. The process of staining involved cooking up some rather nasty chemicals in our improvised laboratory – the kitchen – back in Tana.

    Our next project will be to replicate our VAM study in Ananalava, a humid site on the east coast that contrasts with the drier climate of the Malagasy Highlands. Repeating our study in different environments will help generalize our results and recommendations for people working across this heterogeneous island.

    Cyprien in our kitchen laboratory preparing an improvised stain to look for VAM vesicles.
    Cyprien in our kitchen laboratory preparing an improvised stain to look for VAM vesicles.