RET Summer 2013 Field Trip to Greenbelt Corridor

Transcription

1 RET Summer 2013 Field Trip to Greenbelt Corridor of Ray Roberts Lake State Park WELCOME TO THE GREENBELT CORRIDOR (GBC) A STATE PARK A FLOOD CONTROL AREA A RESEARCH FOREST The GBC extends between two lakes: Ray Roberts to the North and Lewisville to the South TEXAS ENVIRONMENTAL OBSERVATORY (TEO) GBC: dynamic and diverse vegetation mosaic. Includes successional forest stages on fallow farmland, wetland forest, and grassland Weather and Soil Station Soil Moisture Network Vegetation Forest Ecology Inventory Species Age Birds Survey Habitat University of North Texas & Texas Parks and Wildlife Department 1

2 Some facts about the GBC GBC was mostly farmland, which was left fallow in three phases: Dallas dam in 1927 Lewisville dam in 1957 State Park in Succession on fallow land results in three forest stages (up to 1927, up 1957, and up 1980). Additionally, there are some patches of older forest that were not used for agriculture probably because of periodic flooding. Forest succession has been influenced by flooding frecuency, soil properties, seed trees left by farmers, and seed from the old forest. The south sector, affected by long term flooding in wet years, has become a wetland forest. There is also grass vegetation and grass wetland. GBC: 20 mile multiuse trail system and thousand of acres of a diverse forest mosaic Over 5500 birds from 91 species were observed during breeding season in 2009/ % were local breeding birds and 10% migratory flyovers. Most are insectivory, and some frugivory or omnivory. Bird Communities Cardinal cardinal, a truth North Texan. COTTONWOOD FOREST AT THE RIVER LEVEE E W TRANSECT TOPOGRAPHY Cottonwood (Populus deltoides L.) is one of the largest North American hardwood trees, although the wood is rather soft. It can grow quite large and fast (up to 5 feet of growth per year!). They are always found by a permanent water source, usually by rivers in riparian zones. The age of the biggest Cottonwoods in GBC is estimated around years. They may have established shortly after American elm (Ulmus americana), Sugarberry or Hackberry (Celtis laevigata ), Mulberry (Morus nigra L.), Green ash (Fraxinus pennsylvanica) and Box elder (Acer negundo) are also present in these forests. They occur frequently at the river banks along streams and in loamy soils on floodplains. deltoides comes from the leaf shape, similar to the Greek letter delta Over the subjacent Pilot Point Alluvium, a Clay rich material 4,500 to 1,400 year old, a recent sediment was deposited by the Elm Fork Trinity River and the Clear Creek. Since 1957 the Elm Fork flows into the backwaters of Lewisville lake, thus sedimentation on the levee and adjacent areas is accelerated. Sedimentation may have increased already in 1927, when Dallas lake was built, and again in 1989, when the lake level was changed from 517 to 522 feet 2

3 SOIL PROFILE AT THE RIVER LEVEE (0-2 m) Highest position on the floodplain, mostly sandy and well-drained soil 0-10 cm Fresh sediment, silty Clay (2007 flooding sediment) A IIAC III AC IV AC V AC Silty clay Loam (7 micro-layers); weak structure; dark reddish gray (2.5YR 4/1); abundant fine roots. From 27 to 40 cm visible compression effect of flood. Bulk density (Bd) 1,28 to 1,38; ph 7.9. Sandy Loam (7 micro-layers and imbedded sand lens); three different A1. No structure; good drainage; decreasing root development downwards. Bd: ; ph 8.2. Loam, 70% pale brown (10YR 6/3), 30% very pale brown (10YR7/4), compact, incipient structure; few medium & fine roots; abrupt boundary; good drainage; ph 8.1. Fossil horizon A1 at the top 10 cm. Clay Loam, dark grayish brown (5YR 4/2); weak blocky structure; few medium & fine roots; abundant 5 mm small shale at 180 cm; moderate drainage (seasonal fluctuating ground water). Clay Loam, dark gray (7.5YR 4/1); moderate fine angular blocky structure, with shiny pressure faces on peds; very few fine & medium roots; moderate drainage as in the upper horizon. Corresponds to Pilot Point Alluvium. BOX ELDER (Plot 1 at the River levee) Box elder (Acer negundo) is a pioneer species that needs bright sunlight and often grows on flood plains (river levee) and disturbed areas with ample water supply. In the GBC, box elder have frequently colonized fallow farm areas on sandy loam soils. Some midaged Cottonwoods (Populus deltoides L.) may have arrived before Box elder (probably shortly after 1980). The soil profile is formed by a 6 ft deep sandy loam layer on the subjacent 4,500 year old clayloam Pilot Point Alluvium Typical leaf, with 5 leaflets SOIL PROFILE AT THE WEATHER STATION (0-2,0 m) Middle position on the Flood Plain, top soil sandy over the Pilot Point Alluvium (silty clay) TEXTURE PROFILE AT THE WEATHER STATION 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% A cm IIAC Silty Loam; dark gray (5YR4/1); fine subangular blocky structure; good drainage; abundant fine and medium roots; bulk density: 1.2; ph 7.7. Clear smooth boundary. Sandy Loam; 50% weak red (2.5YR5/2), 48% reddish gray (2.5YR5/1), and 2% reddish yellow (5YR7/6); (colors identify micro layers with different organic matter content); no structure; non sticky non plastic; abundant fine and very fine roots; clear smooth boundary; good drainage; Bd 1.5; ph %Clay %Silt % Sand IIAC Sandy Loam; 60% light brown (7.5YR6/3), 40% light grey (7.5YR7/1); no structure; friable, non plastic; frequent fine and medium roots (less than 5 mm thick); clear boundary; Bd 1.4; ph SAND III AB1g Silty Clay; dark gray (7,5YR 4/1); moderate, fine, sub angular blocky structure; no mottle; frequent fine roots, few medium roots (1-1,5 cm); some dead roots 2-4 cm; diffuse boundary. Moderate drainage (fluctuating groundwater table 50% of the year); ph 8.0. Visible fossil A1 on the top. Corresponds to Pilot Point Alluvium. 5 6 CLAY SILT IIIAB2g Silty Clay; brown (7,5YR5/2), no mottle; moderate medium blocky structure; frequent fine and very fine roots; diffuse wavy boundary. Moderate slow internal drainage as in upper horizon. ph

4 PORE VOLUME IN SOIL PROFILE (Weather Station) SOIL WATER DYNAMICS % 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% MICRO MESO MACROPORE Texture and structure determine pore volume. Compact clay produces micropores Silt generates mesopores Sand and good structured clay generates macropores. Organic matter and calcium promote strong structure. Continuous macropores favor infiltration at the soil surface and water percolation. Micropores, usually saturated, reduce water movement. Mesopores mean water availability for plants. Soil water changes after rain events. See next. Weather and Soil Station (2004) SOIL WATER DYNAMICS AS MESURED BY SENSORS (GBC- Soil and Weather Station) Sensors for: Rain Relative Humidity Temperature Solar radiation Wind speed & direction Soil moisture Soil water tension 4

5 SOIL SITE WATER DYNAMIC The weather station site belongs to the best drained sites in the GBC. In the wetland (long term soil saturation) only few species, likeswam privet (Forestiera acuminata) and Black willow (Salix nigra) are competitive (physiologic and reproduction strategies). In between both extremes many GBC Species are successful (about 20), especially Cedar elm (Ulmus crassifolia) Expansion WSN Wireless Sensor Network (WSN) Aims to generate information to compare soil water dynamics between four different soil sites: 1. River levee 2. Meander levee (Box elder plot) 3. Poorly drained clay soil under grass/scattered tree vegetation 4. Poorly drained clay soil under Cedar elm forest. CEDAR ELM The most abundant tree in the GBC Cedar Elm (Ulmus crassifolia) is intolerant to fire and tolerant to anoxia. Adapted to all kind of soil textures. The leaves are thicker than in other elms (crassifoliate) thus the epithet crassifolia. Unlike other Ulmus, its fruit/seed period begins in summer and ends in the fall. 5

6 SOIL PROFILE AT THE SLOUGH POSITION 0-2,0 m) Lowest position on the Flood Plain, top soil fine textured over the Pilot Point Alluvium (silty clay) A cm A A AB Silty Clay (Pilot Point Alluvium); dark grayish (2.5YR3/1); moderate medium and fine granular and blocky structure; abundant fine roots; smooth boundary; moderate drainage; ph 7.7 Silty Clay; dark reddish gray (2.5YR3/1); moderate fine blocky structure, shiny pressure faces on peds; frequent shale; calcareous; frequent fine roots; moderate drainage. ph 7.9. Silty Clay; dark grayish brown (10YR4/2) with 5% reddish yellow mottle on fossil A1 in the top 12 cm, which going downwards becomes brown; moderate medium and fine blocky structure; common fine roots; moderate drainage. ph 8.1. Silty Clay; very dark gray (10YR3/1) with reddish yellow mottle (5%); moderate medium blocky structure which forms a prismatic macrostructure; generalized slickenside; some fine quartz gravel; few roots. Slow water movement. ph 7.9 Swamp Privet a wetland forest species Swamp privet (Forestiera acuminata) is a very competitive species under anaerobic conditions, thus, it has been able to colonize extense soil water saturated areas or periodical flooded areas at the Greenbelt Corridor. AB Silty Clay; dark gray; weak and tight medium blocky structure; few roots. Very slow water movement. ph 7.9 SUMMER yr FLOOD WHAT INFLUENCES GBC FOREST DYNAMICS? The Weather Station is at 520 feet elevation Flooding extended over large areas. Even after the lake level droppped to 529 feet Duration and depth of flooding during wet years. Soil water dynamics during normal years (no flooding) including drought intensity, which depends on soil physical properties. Seed dispersion, which depends on seed trees (preexisting forests and trees), and dispersal vectors (wind, waterflows, birds, bats, and mammals). Soil chemical properties (fertility, organic matter content, ph, nutrients) Tree species competition. 6