SLP Habitat Restoration

Background

Field stations are observatories to the living world, providing centers for scientific research of local and international importance. They are places where rapid environmental change can be studied, relevant to many major societal challenges such as threats posed by climate change, biodiversity loss, natural resource extraction, fire ecology, invasive species and pollution. The management plan must therefore balance the needs of research, stewardship and fire management.

Stengl Lost Pines (SLP) provides the capacity for long-term ecological research in the largest patch of old-growth pine-oak forest remaining in the Lost Pines region. This formation itself is of great interest as the most westerly and driest relict of the great southeastern pine hardwood forests of south east US. In the future under climate change, protected areas such as SLP on the drier western margin of pine woodlands may be of further importance as source populations for drought-resistant genotypes. Additionally, because much of the flora and fauna at SLP are at the extremes of their ranges and climate tolerances, even mild changes in temperatures or rainfall can dramatically impact the species composition and densities. For this reason, SLP is particularly well suited to monitor and capture these changes as they naturally occur.

With so much of the area’s forest recently burned (2009, 2011, 2015) and habitat lost to development, SLP may provide rare refuges for several species dependent on large interconnected tracts of low disturbance habitat. These species include the flying squirrel (Glaucomys volans), pileated woodpecker (Dryocopus pileatus), the Houston toad (Bufo houstonensis), and the Navasota ladies' tresses orchid (Spiranthes parksii). The importance of SLP is not dependent on having survived these recent burns, but that the property provides additional capacity for at least some part of the ecoregion to survive any particular burn and act as source populations for many organisms.

Management Objectives: Stewardship, Research and Fire Mitigation

Central to the goals of this field station is the commitment to exemplary land stewardship relevant to the ecoregion. This serves to protect the habitat diversity and natural communities while being a teaching tool for students and visitors interested in stewardship. Research opportunities also arise from the implementation of habitat stewardship. A variety of long term management techniques (mowing, understory clearing, patch creation and prescribed burns) can provide diverse habitats capable of sustaining a broad range of fauna and flora.

Many ecological and environmental studies require independent, well-spaced plots in similar habitats to provide replication. Allowable manipulations would include small to large animal exclosures with fencing materials to compare community responses in the presence or absence of study species. Other ecological research is dependent on small-scale habitat manipulations, and these would be allowed if considered to have minimal long-term impacts. The forested area of SLP provides one of the only templates to study this ecoregion after a long interval of no fire and with very limited anthropogenic changes. As such, the management strategy is to continue a conservative approach within the forests of the original SLP tract. However, the inclusion of additional acreage in 2016 has opened new opportunities for such habitat-dependent studies. Furthermore, a large sector of the new tract includes old pasture and cropland that could be allocated to experimental and cultivation plots.

Fire is an important feature of the Lost Pines ecoregion, serving to maintain woodland/grassland interfaces in a dynamic plant community. Long-term fire suppression has likely increased the risk of high-intensity fires and SLP has large stands of forest that did not burn during the 2011 and 2015 fires. The historic landscape had more frequent fire return intervals, and the landscape will likely return to this pattern over time. In cases where current land use allows, then TFS suggests increased fire frequency, at smaller spatial scales to develop a regional mosaic of burn patches, with SLP currently serving as an unburned patch for the region. Active fires may be allowed to burn in areas away from WUI zones, depending on fire frequency goals, or when the scope of a particular fire and likelihood of suppression is balanced against resources available. Recent fires have been more intense, in part due to long-term suppression and also from flash drought conditions with increased weather variance.

Land Use History and Environmental Features

Overall, the primary resources of any field station are the habitats, organisms and ecosystems. Field stations with diverse habitats provide the greatest opportunities to explore natural systems. Habitat differences are often driven by the interplay of biotic and abiotic factors such as soil types, topography, hydrology, land use history, fire frequency, disturbance, and climate. At SLP, these factors have been extensively documented both to provide an understanding of the ecosystem and as a template on which a large variety of ecological studies occur.

Historically, this region was logged for timber and the open areas were used to graze cattle. Though there has been no logging on the original 208-acre property since the early 1900's the oldest pines are roughly 60 years old. Natural senescence thins the forest of its oldest trees with replacement from the seedling and sapling pool. By inspection of old air photos and examining the age structure of different stands of trees, we can infer where several areas were logged at different past times.

To help maintain a diversity of habitats, the meadows along the western boundary are routinely mechanically mowed, with a mosaic of differing mowing intervals. The meadows were historically used for row crops and as cattle pastures. Evidence of contours in the old crop fields can still be seen. The expansion of SLP to include the North tract adds five extra soil types to those found on the existing field station. The land use history also differs considerably from the Stengl tract with large areas of old farm land, recent cattle grazing, and different patterns of forestry management and fire history. Fire has always been a part of this ecosystem, but no major fires have occurred on either block for over 50 years. These combinations of soil types and land use history form templates for biotic communities not found on the existing field station, despite their immediate proximity.

The perennial pools, springs and wetlands along JD Creek are some of the most significant features of SLP. These pools contain diverse fish and aquatic invertebrate communities that attract key research. However, the drainages are entirely dependent on upstream watersheds situated on the adjacent properties and the acquisition of the northern tract in 2017 helped to secure the major portion of the watershed.

Many of the mammals, birds, plants and insects that occur on the SLP require territory and habitat sizes that exceed the spatial extent of SLP to maintain viable populations. With habitat loss to development in the adjacent properties, some of these breeding populations are expected to be ever more dependent on SLP. On the east, the Luecke ranch has been extensively cleared for pastures, while to the south and west SLP is surrounded by 15 properties of 3-5 acres in size, with associated construction and development. This habitat fragmentation and loss is likely to have major impacts on several species. To the north is a cattle ranch with relatively undisturbed woodland habitat. Through careful habitat management, SLP maintains populations of several rare plants such as the endangered Navasota ladies' tress orchid, (Spiranthes parksii). While no Houston Toads (Bufo houstonensis) have been encountered to date, SLP is within the likely range and contains suitable habitat.

Given the remote nature of SLP, only a limited number of invasive species occur. In an effort to maintain native species and natural systems, some actions have been taken. SLP has been a release site for the biological control used against the red imported fire ant, a small phorid fly. There are ongoing efforts to remove all Chinaberry trees (Melia azedarach) found in the riparian areas, while vehicle access is restricted to help slow the introduction of invasive grasses such as KR Bluestem (Bothriochloa ischaemum).

Habitats at SLP

SLP falls within the Post Oak Savanna ecoregion and is part of the charismatic Lost Pines block with stands of Loblolly Pine (Pinus taeda) disjunct from the eastern populations of this pine species. The habitats of SLP are primarily plant communities established through decades of natural succession with little recent anthropogenic or fire disturbance. The variance in the current habitats is greatly influenced by the topography and local soil types. Natural disturbances tend to be small in scale, such as tree fall gaps, or flood events in the water courses. The richness of habitats and overall site-wide diversity is one of SLP’s greatest features.

Primary habitat types have been assigned based on a tree survey, aerial photography, and soils maps. Habitats arise from combinations of different age classes of dominant trees such as Blackjack Oak (Quercus marilandica), Loblolly Pine (Pinus taeda), Post Oak (Quercus stellata), Eastern Juniper (Juniperus virginiana). Along the riparian corridors, we find Water Oak (Quercus nigra), Black Hickory (Carya texana), Red Mulberry (Morus rubra), and American Sycamore (Plantanus occidentalis). 

The habitats of SLP are noticeably dynamic when viewed across decades of air photos. Beginning in the mid-1990s longer dry periods began to dramatically shift the vegetation makeup of much of the area. The “Lost Pine” plant communities depend heavily on underground water resources to sustain plants typically associated with areas that receive greater annual rainfall. These underground reservoirs are maintained by the general soil structure of the area, a rapidly draining sandy surface with a watertight clay pan beneath. For many years this captured and held sufficient rainfall, allowing these plants to survive as relics in this region. However, during the current extended dry periods these underground reservoirs are becoming depleted or are no longer accessible to these plants. Therefore, in the past decades we have seen a rapid change in much of the habitat of SLP. Many areas have lost close to half of the pine trees. Mortality is greatest among those trees typically associated with a more eastern system (loblolly pines, black jack oak, farkleberry, etc.). Areas exhibiting this high mortality appear to be transforming into post-oak savannahs. Documenting this large-scale habitat change is a long-term goal of SLP.

Another effect the soil structure has on habitat diversity at SLP is the overall patchiness of the forest. This diversity is often related to the depth of the clay layer beneath the sandy soil, which creates areas with larger and smaller water deposits. These differences affect the makeup of the plant community in general, as well as their ability to sustain drier times. 

Fire Mitigation Plan

Fire mitigation must be incorporated into the overall habitat stewardship and research plan for SLP 

Goals

1. Research goals for SLP habitat. The first goal is achieved by protecting and maintaining the multiple existing habitats which include stands that have had little disturbance for decades. It is understood that at some future point these habitats may be subject to fire penetration, which would reset the system. At present SLP includes large stands of some of the only remaining mature forest in the area and may serve as a source population and refuge for a wide variety of organisms that reside in these older stands with large trunks, dead limbs and structural complexity. After any future burn, then other parts of the region will provide alternate source populations for such species. The ongoing studies at SLP help to define the pre-fire status of the system, especially of plant and insect communities. Because of these needs, the current management strategy will avoid habitat manipulations or introduction of fire into the study areas. 
2. Safety of personnel and property using WUI guidelines around facilities. The area around the facilities is considered a Wildfire Urban Interface zone and appropriate guidelines are followed to mitigate fire risk around the facilities:
   • 30 ft defensible space around buildings
   • Tree trimming in facilities area
   • Minimize use of gutters on buildings
   • Irrigation sprinklers installed around buildings
   • Maintain underpinning to prevent leaf accumulation under raised decks and floors
   • Well installed with a 2500-gallon tank
   • Large tank/pond near buildings kept filled with well water
   • Boundary maintained with road and 30 ft shaded fuel break, dozed then mowed regularly since 2012
   • Understory fuel reduction maintained between facilities and adjacent forest
   • Emergency plans in the event of high-risk days, or active fire on the property
   • Monitor KBDI and other drought indices for risk patterns and plan activities accordingly
      
3. Implement cost-efficient mitigation activities linked to proven outcomes.
   • Critical activities such as boundary roads and shaded fuel breaks are justified to allow access during fire operations and to minimize passage of fire between properties with low flame height. 
   • Crown fires are rare events (<3% event conditions) capable of crossing 100-foot fire lines, and little can be done preemptively to prevent passage of crown fires.
   • Extensive clearing of understory in habitat research area may decrease fire intensity, but is costly to implement annually and would cause major habitat modification, counter to Goal 1. Such clearing is not necessary to achieve Goals 2-5. In fire emergency conditions, then TFS/VFD would cut bulldozer lines as needed to control fire path.
   • Onsite ignition events by human action are extremely unlikely given the nature of activities. Lightning ignition is rare, almost all county ignition events have occurred from human activities. Accidental fires are most likely around buildings, already protected by WUI activities. All personnel to monitor county fire alert status. 
      
4. Ensure ease of fire fighting activities in the event of a fire.
   • Ensure well-maintained access and egress to property (along Old Antioch) and within property, along boundary roads and by foot along cut transect lines.
   • Offer use of station facilities area for fire crew staging.
   • Offer use of well and large tank/pond for fire fighting.
   • Host regular familiarization meetings with local fire first responders.
   • Train staff to act as READ (Resource Advisor) as needed for future events.
      
5. Integration with neighbors’ fire mitigation plans.
   • Annual review of fire mitigation measures and risks on all neighboring properties.
   • East boundary needs a wide shaded break to remove fuel ladder and slow fire speed once it enters understory. Fire can spread rapidly across substantial grass pastures.
   • South boundary has several small holdings and residences, which pose risks for ignition and low WUI status. Maintain shaded fuel break and engage neighbors to improve WUI.
   • West boundary: Old Antioch Road needs shaded fuel breaks on neighbors’ properties. Maintain a mowed fire break along road.
   • Maintain shaded break on north boundary to reduce fuel levels and slow advancing fire at ground level.