![Graphical cross-sectional rendering Resh and Rosenberg's [14] and Orghidan's [22] Hyporheic Zone in the rithron region of a freshwater stream showing the lifecycle of various stream macroinvertebrates. As senescing riparian leaves fall, they drop to the ground and are washed off the banks into the stream where shredders feed on the leaves and disperse CPOM into the water column. Through the interstices of the hyporheic zone transferred via gravity, vertical capillary action, and horizontal water flow, grazers and collectors break CPOM down into FPOM, whereby it is further vertically transferred down into the groundwater layer. Here, migrating grazers break FPOM down into DOM, which stream zooplankton feed on.](https://www.researchgate.net/profile/David-Rolbiecki-2/publication/388001006/figure/fig1/AS:11431281303613482@1736876837583/Graphical-cross-sectional-rendering-Resh-and-Rosenbergs-14-and-Orghidans-22_Q320.jpg)
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Ecology and Evolutionary Biology
2025, Vol. 10, No. 1, pp. 1-21
https://doi.org/10.11648/j.eeb.20251001.11
*Corresponding author:
Received: 8 December 2024; Accepted: 23 December 2024; Published: 9 January 2025
Copyright: © The Author(s), 2025. Published by Science Publishing Group. This is an Open Access article, distributed
under the terms of the Creative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0/), which
permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.
Research Article
Diversity and Community Structure of a Riparian Forest
Community on Denton Creek, City of Grapevine, Tarrant
County, Texas (U.S.A.)
David Alan Rolbiecki*
Texas Military Department, Texas National Guard, Camp Mabry, Austin, The United States
Abstract
Data comprising the location, size, and frequency of occurrence of 1,300 bottomland riparian trees along a 4,300 ft (1,311 m)
stretch of Denton Creek in Grapevine, Texas, was captured. Twenty-five separate species were determined from fourteen
different families whose diameter at breast height (DBH) was three inches (7.62 cm) or greater. Elms were the most frequently
occurring trees, with Hackberry and American Elm the predominant species. Most occurrences of trees were between 3-12
inches (7.62-30.48 cm) DBH. Brillouin's index of diversity (H) was 1.00 out of a maximum possible diversity (H max) of 1.29,
indicating that this community has high species diversity, in spite of the fact that trees less than 3 inches DBH were not included
in the survey. Relative diversity according to the evenness (J) ratio of H and H max was 0.78, suggesting that this community is
nearly 80% at its maximum possible diversity. In terms of ecological importance, this riparian community is rich in habitat
diversity and provides vegetative and protective cover for both flora and fauna, habitat niche, breeding sites and plant
distribution. In terms of human importance, the site has economic importance, both as a source of crop and domestic animal
production, erosion control, water conservation, and land value.
Keywords
Diversity, Riparian, River Continuum, Allochthonous, Autochthonous, Hyporheic Zone, Trophic Pyramid
1. Introduction
Riparian zones are vegetational areas of an ecotone that
separates upland and aquatic ecosystems. They typically
occur along freshwater stream banks and serve as a buffer
zone for sediment and nutrient runoff from uplands and
floodplains draining into streams and rivers. By slowing down
surface runoff, riparian vegetation serves as a vector for re-
charging groundwater and aquifers. Riparian vegetation fea-
tures an abundant amount of compositional and structural
biodiversity, occupying one of the most productive areas of
the environment, increasing regional diversity by 50% [1].
In our current era (CE), competition for wildlife habitat
space in the United States is in a precipitous situation due to
increasing demands for land development. Human population
growth is in a steep, upward trend, with a projected 25.5
percent increase from 2016 to 2026—an increase of 81.4
million people just in the United States [50]. With this popu-
lation growth comes the need to locate and shelter these peo-
ple, and land development is right in step with demands for
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housing. The cause and effect of land development is loss of
habitat, and the direct and indirect anthropogenic effects (e.g.,
erosion and excessive nutrient loading [2, 3]) on the earth’s
ecosystems; namely, riparian habitats, which are one of the
most biologically diverse and sensitive habitats on earth [2, 4].
Introduction of exotic species into an ecosystem creates
competition with the existing biota, resulting in loss of the
native species. The effect from the introduction of exotic
species adversely alters the way an ecosystem works, creating
a more homogenous species dominance which directly alters
the heterogeneity of species and consequent loss of biodiver-
sity that alters the way an ecosystem was intended to work [5].
The local extinction of native and diverse species in an eco-
system caused by anthropogenically introduced exotic species
is more common than global extinction, and this effect be-
comes irreversible [5].
Diversity may be described as the variety of species and
their relative abundance in an ecosystem [6]. Particularly, the
highly diverse structure of bottomland trees, shrubs, and
vegetation found in riparian habitats, as they serve as a buffer
zone by reducing sediment loads from surface runoff going
into the stream [3]. Methods for quantifying ecological di-
versity have been well-documented (e.g. [7-9, 37-41]). Ways
to measure diversity of a community is species richness,
which is a measure of the health of an ecosystem, as well as
maintaining the balance of hydrological cycles, energy input
into freshwater ecosystems, and balancing the trophic pyra-
mid [10].
In the United States, Texas is the second most biologically
diverse state in the country [11, 12]. A large number of Texas’
deciduous hardwood communities are found along riparian
watercourses where there is an abundant supply of water. The
increasing demand for land and water (which are limited
resources) has raised the importance of riparian forests in
terms of economic, aesthetic, and ecological factors. Eco-
nomically, riparian forests maintain water quality by acting as
a buffer zone for nutrient runoff into the watershed from farms
and developed areas [2]. They also provide stability along the
banks of streams and rivers and help prevent soil erosion [13].
Aesthetically, riparian forests are often scenic environments,
providing an opportunity for people to enjoy unique species
and habitat features (e.g. ecotourism [5]). Ecologically, these
forests are complex communities, playing a vital role in the
transfer of energy (trophic). They are often rich in habitat
diversity, providing a niche for many plant and animal species
[14].
1.1. Denton Creek
Denton Creek is a third-order stream and a tributary of the
Elm Fork of the Trinity River. From its headwaters, Denton
Creek flows down to an impoundment, Grapevine Lake. From
its spillway, Denton Creek flows past the study area in the
City of Grapevine to its mouth at the confluence of the Trinity
River. The study area lies within the Blackland Prairie Region
of the Eastern Cross Timbers of north central Texas [26, 27].
Vegetation along the banks of Denton Creek consists of fac-
ultative riparian (FAC) grasses, forbs, and hardwood trees that
grow larger in height near the Transition Zone. The floodplain
in this study consisted of grasses, woody shrubs, and a sparse
mixture of honey mesquite and black willow that divided the
study area into two separate stands of hardwood trees. The
Transition Zone is where riparian trees transition to upland,
i.e., from FAC riparian to facultative upland (FACU) and
upland (UPL) trees and shade-tolerant grasses and forbs (Ta-
ble 1).
1.2. Facultative and Obligate Riparian Trees
Along the riparian corridor exists biologically rich inter-
stices of woodlands separating stream and river ecosystems
from upland ecosystems. Floodplains are associated with
riparian watercourses and contain woody shrubs and trees
that are classified as being both “obligate-riparian” and
“facultative riparian.” Both categories play a significant role
in stream bank stabilization, sediment and erosion control,
assimilation of nutrients and pollutants, and provide a di-
verse habitat for specialized flora and fauna living within
riparian habitats [15]. The ecological term ‘obligate’ sug-
gests this category of woody shrubs and trees are restricted
to wet soils in bottomland riparian zones. However, ‘facul-
tative’ allows this category to exist in both riparian and
upland areas. In bottomland riparian hardwood forests, the
association of elms, ashes, and cottonwoods (a willow fam-
ily tree) are typically found to exist in well-drained soils of
the floodplain. In wetter soils along stream banks, the oak,
gum, and cypress associations are usually found [16]. Ex-
amples of woody shrubs and trees found in Texas are shown
in Table 1.
Table 1. Some woody shrubs and trees found in Texas riparian zones. Under the Wetland Indicator Categories are: Obligate Wetland (OBL),
Facultative Wetland (FACW), Facultative Upland (FACU), and Obligate Wetland (UPL). Modification of Common Plants of Riparian Areas
[17].
Woody
WI
Woody
WI
Legend
WI - Wetland Indicator Categories
Buttonbush
OBL
Pecan
FAC
Bald Cypress
OBL
Little Walnut
FAC
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Woody
WI
Woody
WI
OBL Obligate Wetland Requires wet soil condi-
tions and/or a high-water table.
FACW Facultative Wetland Found in wet and
seasonally moist soils
FAC Facultative Can tolerate wet soil conditions
as well as periodically dry conditions.
FACU Facultative Upland Do not tolerate very
wet soil conditions and are indicative of dry
locations.
UPL Obligate Upland Do not tolerate wet soil
conditions and found away from riparian areas.
False Indigo Amorpha sp.
OBL
Roosevelt Weed Baccharis sp.
FAC
Black Willow
FACW
American Elder
FAC
Arroyo Willow
FACW
Roughleaf Dogwood
FAC
Green Ash
FACW
Pecan
FAC
Spiny Aster
FACW
Red Mulberry
FACU
Box Elder
FACW
Mesquite
FACU
Possumhaw Ilex sp.
FACW
Black Walnut
FACU
Salt Cedar
FACW
Netleaf Hackberry
FACU
Sycamore
FAC
Mesquite
FACU
Eastern Cottonwood
FAC
Western Soapberry
FACU
American Elm
FAC
Bumelia
FACU
Cedar Elm
FAC
Osage Orange
UPL
Oaks
FAC
Juniper
UPL
1.3. The River Continuum Concept and Sources
of Nutrients in a Stream Ecosystem
Within a river ecosystem, the gradient of the drainage
basin causes physical and biological dynamics driven by the
topography and fluvial geomorphic processes; effectively
regulating the energy / trophic input entering the stream [7].
The narrow headwaters of freshwater streams contain coarse
sand, gravel, and cobble substrates and are shaded by ri-
parian vegetation, supplying allochthonous input from se-
nescing leaves. Due to the shading by trees, sunlight cannot
provide the necessary photosynthetically available radiation
(PAR) to induce primary production, i.e., chlorophyll-a and
phytoplankton [18]. Here the macroinvertebrates are pri-
marily shredders and feed on the leaves and deposit coarse
particulate organic matter (CPOM) for collector and grazer
macroinvertebrates [19]. At midstream, it widens to a point
that allows some PAR for primary production, and in this
area, CPOM is reduced to fine organic particulate matter
(FPOM) where collector macroinvertebrate dominate the
fauna. Along the widest part of the stream near its mouth,
PAR is more prevalent to induce primary production of
nutrients, whereby allochthonous input size is reduced and
replaced by autochthonous organic matter in the form of
dissolved organic matter (DOM) [40]; e.g., benthic chloro-
phyll-a, where the dominant macroinvertebrates are collec-
tors and filterers [19-21] (Figure 1).
Among the fauna affected by the input of organic matter
made up from allochthonous deposits (e.g., seasonal fall se-
nescing leaves), are the macroinvertebrates, which are a crit-
ical source of food resources for tertiary consumers at the
apex of the trophic food pyramid [7, 14]. Macroinvertebrates
have evolved into specialized species adapted to feeding on
CPOM, FPOM, and DOM. According to Vannote et al. [7],
riparian watercourses may be classified as 1) headwaters
(First, Second, and Third Order), medium-sized streams
(Fourth and Fifth Order), and large rivers (Sixth Order and
greater). The primary food source input into First, Second,
and Third-Order streams comes from allochthonous organic
matter, e.g., leaf and grass litter [20], which makes the diverse
riparian areas of low-order streams extremely important,
ecologically, in the overall trophic pyramid of freshwater
streams (Figure 1).
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Figure 1. Graphical rendering of Vannote et al. [7] “The river continuum” showing energy input and the trophic pyramid [19].
1.4. The Hyporheic Zone
Freshwater lakes and streams contain interstitial spaces
where trophic transfer of energy takes place. In lentic (lake)
systems, the interstices in the littoral zones are termed
psammon, which are various-sized sands and gravel sur-
rounded by water spaces which allow benthic animals to
thrive and feed on nutrients via gravitational and capillary
action through these spaces. The types of benthos one would
find include zooplankton feeding on phytoplankton, a primary
producer in the trophic pyramid. In lotic (stream) systems, the
mixture of coarse sand, gravel, and cobble substrate found in
running water are located in the rithron region of the stream.
The heterotrophic input through the interstitial environment is
known as the hyporheic zone [14, 23] (Figure 2).
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Figure 2. Graphical cross-sectional rendering Resh and Rosenberg’s [14] and Orghidan’s [22] Hyporheic Zone in the rithron region of a
freshwater stream showing the lifecycle of various stream macroinvertebrates. As senescing riparian leaves fall, they drop to the ground and
are washed off the banks into the stream where shredders feed on the leaves and disperse CPOM into the water column. Through the interstices
of the hyporheic zone transferred via gravity, vertical capillary action, and horizontal water flow, grazers and collectors break CPOM down
into FPOM, whereby it is further vertically transferred down into the groundwater layer. Here, migrating grazers break FPOM down into DOM,
which stream zooplankton feed on.
1.5. Trophic Pyramid and Food Resources in
Freshwater Streams
According to Resh and Rosenberg [14] and in a similar
fashion from Lindman [24], trophic relations in freshwater
systems may be looked at as being five levels in a trophic
pyramid: 1) primary producers (plants), 2) primary consumers
(herbivores), 3) secondary consumers, 4) tertiary consumers,
and 5) detritivores (decomposers) (Table 2).
As illustrated in Figure 1 and Figure 2, allochthonous
trophic inputs determined by stream order, riparian vegetation
type and density, stream hydraulics and hydrology, and lon-
gitudinal stream gradient directly influence aquatic ma-
croinvertebrates. Therefore, stream morphology and vegeta-
tion can predict the trophic status of freshwater streams [14].
Table 3 summarizes the utilization of organic food resources
by macroinvertebrates.
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Table 2. Trophic pyramid of aquatic macroinvertebrate functional feeding groups and trophic relations (modification of Resh and Rosenberg’s
Table 6.2 [14]). Freshwater stream macroinvertebrates are influenced by allochthonous inputs of energy, which are directly associated with the
density of riparian vegetation, stream morphology (discharge, width, gradient). These factors change as stream order increases, and the spatial
temporal location and identity of stream macroinvertebrates are a good indicator of the trophic status in a particular reach of the stream [14].
Macroinvertebrate
Functional Feeding
Group
Food and Feeding Mechanisms
Approximate Range of Food
Particle Size (microns)
Food
Feeding Mechanism
Shredders
Living vascular hydrophyte tissue
Herbivores (chewers & miners)
> 103
Decomposing leaves and wood
(CPOM)
Detritivores (chewers, wood borers,
gougers)
Collectors
Detritivores (filterers & suspension
feeders
Decomposing FPOM
< 103
Detritivores (gatherers & sediment
feeders (incudes surface film feeders
Scrapers
Periphyton (attached to substrate
cobble & wood)
Herbivores (grazers/scrapers off
cobble and wood)
< 103
Living vascular hydrophyte cell &
tissue fluids / macroscopic algal cell
fluids (DOM)
Herbivores (piercing tissue cells,
sucks fluids
> 103—103
Piercers
Living animal tissue
Carnivores (attacks prey, pierces
tissue & sucks fluids)
> 103
Predators
Living animal tissue
Carnivores (whole animals or parts)
> 103
1.6. Conservation and Management Best
Practices
Due to the increased human population of North America
and the large migration of out-of-state residents into the State
of Texas, it is essential for programs of wildlife conservation
practices to be on the forefront of local, state, and national
authorities to implement more stringent regulations on land
development in sensitive areas of rich biodiversity such as
riparian ecosystems.
These practices would involve establishing the “protected
status” of riparian corridors which would target land devel-
opers to abide by law restricting alteration of floodplains and
bottomland habitats. A unified approach in ecological
preservation can be the best way to achieving sustainable
resources for the existing flora and fauna with the chance of
preserving trophic input into riparian ecosystems which will
continue to preserve species and biodiversity.
In urban areas such as the City of Grapevine where Denton
Creek runs its course down to the Trinity River, urban con-
servation ordinances can be introduced to enable best prac-
tices in the sustainment of natural resources. One method
would be the establishment of irrevocable and perpetual
“Conservation Easements” of sensitive riparian ecosystems
between their landowners and the local government. This
would forever restrict land development in these biologically
rich and diverse ecosystems. In doing so, benefits to the local
economy may be achieved by establishing local or state
wildlife parks, offering ecotourism, regulation of the har-
vesting of natural resources, and the enhancement of the
commercial fishing guide industry, to name a few.
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Table 3. Food resources used by aquatic macroinvertebrates in headwater, mid-reach, and large rivers. (modification of Resh and Rosenberg’s
Table 6.1 [14]. In a given stream reach, nutrients in the particulates and dissolved organic matter are fundamental in the downstream flow of
lotic ecosystems as they enter lentic ecosystems. Table legend: Nutrient resource type relative dominance: C = Common; S = Sparse; A =
Absent. * = Conceptualized range of macroinvertebrate species richness.
Nutrient Resource Type
Stream Order
Algae
Vascular plants
FPOM
Leaf litter CPOM)
Wood
Headwater streams
(orders 1-3)
(100 – 250 species)*
S; some scraper
species:
Ephemeroptera
Plecoptera
Tricoptera
Coleoptera
Diptera
A (mosses & liv-
erworts not in-
cluded, but species
using mosses:
Ephemeroptera
Tricoptera
C; many collector
species:
Ephemeroptera
Tricoptera
Diptera
C; many shredder
species:
Tricoptera
Coleoptera
Diptera
C; few shredder
species:
Tricoptera
Coleoptera
Diptera
Mid-reach rivers
(orders 3-6)
(200-500 species)*
C; many species:
Ephemeroptera
Tricoptera
Diptera
C; few species:
Tricoptera
Lepidoptera
Coleoptera
Diptera
C; many collector
species:
Ephemeroptera
Tricoptera
Coleoptera
Diptera
S; few shredder
species in protected
areas
seasonally or
localized at en-
trance of low-order
streams:
Tricoptera
Diptera
S to C; clumped
distribution; few
species:
Diptera
Large rivers
(orders > 6)
(10-50 species)*
S; very few species:
Ephemeroptera
Diptera
S to A; few if any;
species:
Diptera
C (during transport)
(mostly Annelida,
Mollusca); few
species at high
densities:
Ephemeroptera
Tricoptera
Coleoptera
Diptera
A (S in protected
areas); shredders
Rare or absent in
Mid-reach rivers:
Tricoptera
Diptera
S to A; very clumped
distribution; few if
any species:
wood burrowing
Povilla spp.
(Ephemeroptera)
Downstream transport of nutrients into lentic systems is by
hydrochory, the process of dispersing organisms, plants and
seeds by water [37], and is often associated with ecological
drift [38]. Through hydrochory, plant propagules are moved
downstream in rivers—either by or long-distance dispersal,
natural flooding, or anthropogenically-altered means such as
damming or channelization—and deposited in riparian zones,
whereby increasing species richness and plant colonization
[37]. Ecological drift can be part of a stochastic, temporal
change in a species or variation in fitness of a small popula-
tion of organisms in an area or region, increasing the proba-
bility of niche differentiation, extinction, reproduction, and
maturity. Ecological drift can also be a behavioral method of
freshwater macroinvertebrates releasing themselves from the
substrate to move downstream in order to avoid predation, or
by dispersion of their offspring downstream. Flood disturb-
ances (catastrophic drift) can also dislodge stream fauna fur-
ther downstream [48].
Thus, from the aforementioned literature review, we can
see that freshwater stream ecosystems are one of the most
highly diverse biological communities on earth, amongst the
equatorial tropical rainforests, marine coral reefs and estu-
aries, and coastal mangrove forests. They are extremely
susceptible to natural disturbances—principally from ab-
normal flooding, as well as from anthropogenic influences
through land development (followed by loss of habitat)
which, in turn, natural pervious soils have now been paved,
allowing for faster impervious surface runoff and the in-
troduction of siltation and pollutants into this fragile eco-
system. There are also intentional (albeit without under-
standing the consequences thereof) anthropogenic stream
and river alteration through channelization and damming.
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Other anthropogenic effects include the introduction of
exotic flora and fauna (again, well-intended, but ignorant of
the consequences), which, over time, outcompetes the native
species and the eventual local extinction of these indigenous
biota [5]. Since the introduction of the River Continuum
Concept [7], studies and research of lotic systems has pre-
dominantly been focused on the ecology and diversity of
benthic macroinvertebrates near the headwaters (the most
diverse area of the order of streams), and the local abiotic
effects [5] from changes in stream hydrology (both natural
and anthropogenic) affects the biodiversity of that site.
However, there appears to be sparse research in regional
patterns of biodiversity of the same and suggests a larger
scale study (consider regional and larger areas) of lotic
communities connected together (from upstream and
downstream) and seeing the bigger picture of how they
operate [8, 25] and develop better practices for land use near
riparian watercourses [3].
2. Materials and Methods
This study was inspired following the completion of a
boundary, topographical, and tree survey I performed by
McCullah Surveying, Inc., in Addison, Texas from Ju-
ly-August 1999. The survey was under a contract with a civil
engineering firm whose client was a land developer wanting to
turn this ecologically sensitive area into a multi-family resi-
dential site along the south bank of Denton Creek. In addition to
the other survey requirements, I recorded the location, descrip-
tion, and size of trees along the south bank of Denton Creek and
provided our client the necessary information for planning
purposes. The local regulatory authority, the City of Grapevine,
Texas, required us to locate trees with a diameter at breast
height (DBH) of three inches (7.62 cm) and above. The meth-
ods for quantifying diversity and community structure follows
Unit 5 in Brower et al. [9] Analysis of Communities, Commu-
nity Structure, and Measures of Species Diversity.
2.1. Study Area
Figure 3. Location of the study site as the topography appeared in 1999. 2-ft (0.609 6 m) contour intervals shown. 1 ft = 0.304 8 m. Following
the construction of the multifamily apartment complex, significant changes in topography and upland/riparian habitat loss has occurred (see
Figure 4 and Figure 8).
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Figure 4. Study area shown in the floodplain, City of Grapevine, Tarrant County, Texas, CE 2024. In order for the City of Grapevine to allow
the construction of the multifamily apartment complex, the civil engineer of this construction project was required to perform a flood study to
determine if the base flood elevation (BFE) in the 100-year floodplain would be raised by 1 ft (0.304 8 m) or above. In this case, it was de-
termined the BFE would be raised by over 1 ft, and the civil engineer was required to file a Conditional Letter of Map Revision (CLOMR) and
submit it to the Federal Emergency Management Agency (FEMA) for review. Once the CLOMR was accepted, the City of Grapevine authorized
the construction. Anthropogenic alterations of the natural floodplain tends to disrupt the river continuity. It was in 2020 when FEMA published
a Letter of Map Revision (LOMR) as seen in Figure 4: “LOMR-19-06-2895P eff. 7/20/2020”. Source: Federal Emergency Management
Agency Flood Insurance Rate Map Letter of Map Revision (LOMR 19 06 28959P eff. 7/20/2020), Community Panel Number 48439C0110K,
City of Grapevine, Tarrant County, Texas. https://msc.fema.gov/portal/search?AddressQuery=City%20of%20Grapevine%20Texas.
The study area is a stretch of bottomland riparian hardwood
community in a floodplain located along the south bank of
Denton Creek (centroid: 32°58'41.37"N // 097°02'21.25"W;
elevation: 146m, see Figure 3, Figure 4), in the City of Grape-
vine, Tarrant County Texas, beginning at the west end of the
F.M. 2499 (Grapevine Mills Parkway) bridge crossing, and
extending west approximately 4,300 feet.
Drainage to the site comes from the south, running off a
two-tiered plateau, beginning with a steeply sloped bank
approximately 100 ft high (30.48 m), flattening out to a wide
(200 - 1000 ft [61 – 305 m]) floodplain, and depositing off
25-foot (7.62 m)-high banks into Denton Creek. A typical
cross section of a stream or river consists of the “Toe Zone,”
“Bank Zone,” Overbank Zone,” and the Transition Zone” [31].
The Toe Zone is located between the bed of the stream and the
normal height of the surface of the stream. “The bed is kept
practically bare of upland vegetation by the wash of the wa-
ters of the rivers and is composed of light loose sand” [32]. It
is the area usually devoid of upland vegetation when there is
water, but in cases of drought conditions when the water level
is low, grasses and sedges will grow above the low level of the
water. The Bank Zone begins at the lowest qualifying bank
(key bank) where bank full conditions of the stream first
overtops the key bank [32]. There are usually backwashes at
this location separating the key bank from higher ground [32].
Vegetation consists of grasses and short woody shrubs, and
occasional willows, cottonwoods, and dogwoods. The Over-
bank Zone is located between the normal bank full level and
the overbank elevation. This is normally the location of the
floodplain.
Tree location was part of our client's requirements for a
topographical survey to determine suitability for development
of the site. Identification of trees was by learned knowledge of
the species, or consulting Audubon’s “Field Guide to North
American Trees” [28]. Specific requirements for locating
trees were horizontal location, elevation, diameter at breast
height DBH (3 inches [7.62 cm] and above), and common
name. If possible, their generic and specific names were noted.
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A “Spectra Precision Geodimeter 610” electronic total station
theodolite was used to measure the location of trees and
ground topography. DBH of trees was measured using a
“Spencer Pro Tape” steel diameter tape measure read in
inches.
The land surveying methodology required the establish-
ment of local survey control by setting up the Geodimeter 610
on a tripod over a station whose three-dimensional coordi-
nates have been previously established by Global Positioning
System (GPS) static observations under an open, unobstructed
sky, and precisely back sighting another previously estab-
lished GPS station of known coordinates using a tripod with a
prism set up over the back sight station. Distances were
checked between the two survey control stations using a
built-in electronic distance measuring (EDM) device via in-
frared readings to the back sight station. A traverse was
started by fore sighting to another tripod with prism set up
over a new survey control station inside the forest tree canopy
and measuring the horizontal and zenith distance angles and
EDM distances (GPS technology in 1999 did not have mul-
tipath error mitigation capability and was incapable of satel-
lite observations under tree canopy). Then the Geodimeter
610 was carried forward and set up over the new control sta-
tion and back sighting the previous survey control station;
fore sighting to another survey control station set up under the
tree canopy, and so on. The process of traversing through the
tree canopy was carried out to allow enough survey control
network densification to survey the topography and identified
trees within the project area and was run all the way back to
the initial GPS-derived back sight station, and the horizontal
and zenith distance angles were turned to close back into the
initial GPS-derived control station. The field traverse data
was then downloaded into Trimble Terramodel software
(Trimble, Inc., Westminster, Colorado), post-processed, and
underwent a network adjustment. Following the traverse
adjustment, field work in collecting topographical data and
tying in identified trees was carried out using the station set up
and back sight method, and fore sighting to a survey rod with
prism attached whose rod height was known. This process is
commonly known as a “radial survey.”
2.2. Analysis of Data
Data analysis consisted of enumeration, and placing species
counts by their DBH on an ordinal scale into eleven size
classes: 3-5, 6-8, 9-12, 13-15, 16-18, 19-21, 22-24, 25-28,
29-36, 37-44-, and forty-five-inches DBH and above, respec-
tively (7.62-12.7, 15.24-20.32, 22.86-30.48, 33.02-38.1,
40.64-45.72, 48.26-53.34, 55.88-60.96, 63.5-71.12,
73.66-91.44, 93.98-111.76, and 114.3 cm DBH ↑). Species
counts were totaled and ranked according to their abundance
and relative importance in terms of its presence among the
community. The most abundant species was assigned rank 1,
the second most abundant assigned rank 2, and so on.
Measures of species diversity and community structure was
done using Brillouin's index [9]:
H =
log ! log !N n
N
i
(1)
where ni is the total count for species i and N is the grand total
of all individuals.
Brillouin's index was chosen because tree samples were not
random, but in effect the entire population of the community
(sans < 3 inches (7.62 cm) DBH). Species diversity is often
used by ecologists as a measure of community stability [8].
High diversity indicates a complex community, with a variety
of interactions among organisms to include energy transfer,
competition, and niche partitioning [8]. The more diverse a
community is, the more stable it becomes and resists envi-
ronmental stresses [5, 8]. A community is said to have high
diversity if many species of equal abundance are present. On
the other hand, a community having low diversity has very
few species, or only a few species are abundant [5, 8].
Next, I compared my calculated index to a maximum value
for diversity in the riparian community. The maximum pos-
sible diversity (H max) for N individuals in a total of s species
occurs when the N individuals are distributed evenly among s
species; i.e., when each ni = N ÷ s:
H max =
log ! log ! log !N s r c r c
N
1
(2)
where c = N ÷ s, r = the remainder, i.e., the quotient of N ÷ s is
c, and r is the remainder [9].
Using H and H max, the relative diversity of the community
was determined by measuring evenness among species. Spe-
cies evenness (J) of the individuals' distribution among spe-
cies is how close a set of recorded species abundances are
from a collection of N species having H max [8]:
J =
H
Hmax
(3)
Measures of dominance may be expressed by the quantity 1
– J. Communities with low dominance will have low values
with zero being the minimum; conversely, high dominance
will approach 1, the maximum value for dominance [9].
3. Results
25 species out of 14 families of trees were found in the
Denton Creek study site. A total of 1,300 trees were located
and recorded (See Figure 5 and Appendix 1 and 2). The most
abundant trees came from the elm family with a total of 769.
Most species of elms live in water-rich soils and are often
found in floodplains and riparian watercourses [29, 30].
Hackberry was the most abundant species of the elms fol-
lowed by American Elm and Cedar Elm, respectively. Green
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11
Ash, the only species out of the olive family that was found at
this site was third in order of species abundance (182 trees)
and the second most dominant family. Elms and ashes are
usually found together in bottomland riparian and floodplain
habitats [28-31]. The third most abundant family of trees was
legumes (Redbud, Honey Mesquite, Honey Locust). Mesquite
was found primarily in the open floodplain, and Locust was
found on the bottom of the bank on the south tier, mostly in
the lower, outer fringes of the tree stand. Mulberries (Red
Mulberry and Osage Orange—vernacular Bois d' arc) were
found in near-equal abundance, mostly along Denton Creek.
Oak and Box Elder (beech and maple family, respectively)
were found throughout both hardwood stands. The dominant
oak species was Post Oak. There were 11 mature Post Oaks
with a DBH between 22-24 inches (55.88-60.96 cm). Oaks,
ashes, and mulberries are well adapted to moist soil conditions
and are typically found in riparian and floodplain communi-
ties [16, 28]; see Appendix 1, Table 5). Willows (Cottonwood
and Black Willow) were found both in the floodplain and
along the slopes of Denton Creek, where Cottonwood often
exceeded 24 inches (60.96 cm) DBH. The largest recorded
Cottonwood at the site was 60 inches (152.4 cm) DBH.
Members of the walnut family (Pecan, Black Walnut) were
found along the south side of Denton Creek. The majority of
Pecan were mature specimens whose DBH was over 22
inches (55.88 cm). Only one 16-inch (40.64 cm) Black Walnut
was found. By quick visual observation, many Black Walnuts
and some Black Hickory (Carya texana) were less than 3
inches (7.62 cm) DBH—mostly as reproductive saplings,
which were not surveyed. Sycamores (total 8 trees) were not
plentiful as would be expected in a mixed, bottomland forest
community, but one mature Sycamore was surveyed on the
bank of Denton Creek whose DBH was 60 inches (152.4 cm).
A small number of non-dominating trees were found scattered
throughout the community (Wooly Buckthorn, Hercules-club,
Chinaberry, and Plum).
Figure 5. Number of trees by family surveyed at the 1999 Denton Creek study site (see Table 4 and Appendix 1).
Table 4. Abundance and rank structure of the trees by their common
name that were surveyed in 1999.
Species
Number of trees in
each species
Rank
Hackberry
331
1
American Elm
237
2
Ash
182
3
Species
Number of trees in
each species
Rank
Cedar Elm
166
4
Box Elder
47
5
Honey Mesquite
46
6
Slippery Elm
35
7
Red Mulberry
34
8
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Species
Number of trees in
each species
Rank
Honey Locust
34
9
Eastern Cottonwood
31
10
Post Oak
30
11
Osage Orange (Bois d' arc)
28
12
Pecan
24
13
Wooly Buckthorn
11
14
Black Willow
10
15
White Oak
9
16
Hercules-club
9
17
Sycamore
8
18
Chinaberry
8
19
Cedar (Ash Juniper)
6
20
Plum
6
21
Burr Oak
5
22
Black Walnut
1
23
Shumard (red) Oak
1
24
Eastern Redbud
1
25
Ranking species abundance among the community is
shown in Table 4. Hackberry was assigned rank 1 according
to its dominance and its relative importance and influence
among the community. Many birds including quail, wood-
pecker, and cedar waxwing eat its sweetish fruit [28]. Amer-
ican Elm, Green Ash, and Cedar Elm were assigned ranks
2,3,4, respectively. Red Mulberry, Post Oak, Osage Orange,
and Pecan (ranks 8, 11, 12, 13, respectively) were of medium
dominance and relative importance, however, their fruit pro-
vides food for birds and terrestrial animals. The least domi-
nant species were Black Walnut, Shumard Oak, and Eastern
Redbud (ranks 23, 24, 25, respectively). With the exception of
the one Shumard Oak found, there were numerous sprigs of
Walnut and Redbud under 1 inch (2.54 cm) DBH found
throughout the community.
Frequencies of trees in their respective family are presented
in Figure 6. Elms dominate all size classes, especially in the
3-5-, 6-8-, and 9–12-inch DBH classes (235, 255, 141, re-
spectively). Green Ash was mostly found in the 3-5-, 6-8-, and
9–12-inch classes (44,33, 35, respectively). Mulberry and
Osage Orange were found in the 3-5-, 6-8-, 9-12-, and 13–
15-inch classes (23,23,14,2, respectively). Legumes (mes-
quite, locust, and redbud) were only found in the 3-5- and
6-8-inch classes (66, 14, respectively). Cumulative frequency
curves of the most abundant tree families are presented in
Appendix 2, Figure 9.
Figure 6. Frequencies of trees by family with their DBH found at the
Denton Creek study site.
Diversity among the 25 species found at Denton Creek was
high (Figure 7). Curve A in Figure 7 takes on a horizontal
aspect and shows relatively even abundance of each species in
three rank groups: rank 1-4, rank 5-13, and rank 14-22. A
community with high diversity will tend to have more species
and an even abundance [5, 6, 8]. Curve B depicts a hypo-
thetical community rich with species, and a perfectly even
abundance, representing the highest diversity and lowest
dominance. The chance of finding a situation such as Curve B
in nature is virtually impossible.
Quantitative analysis of data of species diversity in this
community supports the Curve B in Figure 6. The value of
Brillouin's index of diversity (H) was 1.00 out of a maximum
possible diversity (H max) of 1.29. Relative diversity according
to the evenness (J) ratio of H and H max was 0.78, suggesting
that this community is nearly 80% at its maximum possible
diversity. Although the sample size of this community was
large and considered being the sample population universe,
the values of H and H max are probably underestimates since
the survey was limited to sampling trees 3 inches (7.62 cm)
DBH and above. Therefore, the value for evenness becomes
an overestimate [8]. The quantity of 1 – J for measuring spe-
cies dominance was low (0.22). This suggests that there is no
one species in the Denton Creek study area exerting influence
over the other species of trees from this study and is another
indicator of the rich biodiversity within this community [8].
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Figure 7. Species importance curves in accordance with ranking of abundance of trees in three rank groups: Rank 1-4, Rank 5-13, and Rank
14-22. The most abundant tree species are assigned rank 1, followed by the second most abundant species, and so on. The y-axis was Log10
transformed in order to conveniently place a large range of values on the chart. A community with high diversity means there are many species
and evenness versus a community of low diversity [8, 9]. Curve A represents species found in this study. Curve B represents the highest diversity
and lowest dominance. Curve C represents a theoretically ideal situation of species abundance. Curve A has a near linear fit to Curve C (r 2 =
0.922 9) and tends to take on a more horizontal aspect indicating high species diversity and/or low dominance. Communities with low species
diversity and/or high dominance will take on a steep curve.
4. Discussion
This study provided a pre-versus post-construction com-
parison of a sensitive and highly diverse riparian woodland
community. It is now a multifamily apartment complex
(Figure 8). When the survey in 1999 was carried out, the study
site—visually—appeared to be in near-pristine condition and
representative of a model riparian habitat. The later construc-
tion of the apartments altered the natural floodplain topog-
raphy, adding impervious surfaces such as asphalt and con-
crete pavement, and asphalt-shingled roofing. All of which
increases surface runoff of rainwater, especially during un-
seasonal and abnormal flooding, which increases sediment
loading into streams and rivers [4, 15, 18] like Denton Creek.
The anthropogenic effect from loss of habitat contributes to
negative impacts on native riparian plants and trees from
deleterious modification of hydrogeomorphology and sedi-
ment substrate [4, 15, 33].
In the research by Thornwall et al. [25], it was reported that
studies in turnover and regional diversity (β- or γ-diversity)
were sparse. Beta (β) diversity is the ratio between regional
and local diversity. Gamma (γ) diversity represents the overall
biodiversity of a larger geographic region. Specifically, the
proportion of large-scale studies (i.e. “metacommunities”)
which link the movement of “local” species from different
communities together to influence population dynamics and
community structure. Studies of stream diversity appear to be
local-centric (e.g. local stream habitat, stream morphology,
hydrological and disturbance variables), and intra- and in-
ter-specific species interactions—when considered—are un-
der reported in ecological literature. More studies aimed to-
wards effective use of riparian buffer zones for the reduction
of non-point source pollution into freshwater streams are
needed to develop best management practices for land use
near riparian watercourses.
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Figure 8. Current Era post construction of this study of riparian tree biodiversity done in this study in 1999. The arrows point to the outer
boundary of the area of the tree survey. The multifamily apartments and road networks have been constructed in the floodplain. Map image
made from Google Earth aerial imagery.
Out of the most abundant tree family in this study, the
hackberry was found to be the most dominant of the elms
(Table 1). Within the dense stand of the bottomland trees, the
hackberry is a robust facultative riparian tree and has been
reported to proliferate in this environment and can withstand
periods of drought and fluvial disturbances [15]. The common
misconception by the layperson that the hackberry is a
so-called “trash tree,” nothing could be further from the truth.
In fact, the common hackberry (Celtis occidentalis) and its
related family member the sugarberry (C. laevigata) is a
major food source for birds and provide habitat for other
wildlife [46]. It is reported that the sugarberry-cedar
elm-pecan forest is the most widely distributed makeup of
bottomland trees in Texas [47]. The elm-ash-maple-mulberry
presence along the south bank of Denton Creek is indicative
of co-dominant species tolerant of seasonal flooding in ri-
parian bottomlands [16, 28, 30].
The high presence of facultative riparian trees in this study
plays a significant role in stream bank stabilization, a critical
function of the floodplain, where this study took place [3, 4,
16, 17, 30, 31] (Figure 8). Riparian flora allows for bank
stabilization of streams and rivers by providing a buffer zone
against erosion, sediment and nutrient loading into the water.
The average bank-to-bank width of Denton Creek at this study
site is 30 m, which can trap about 85% of sediments from
polluting the water [3, 34, 35, 36]. Sweeney and Newbold [35]
found in their review of the literature, protection of the
physical, chemical, and biological integrity of small streams,
buffer zones ≥ 30 m wide are needed. Although stream mor-
phology was not the predominant requirement for the tree
survey, its top banks on both sides were surveyed. In com-
parison to other study locations on Denton Creek [19], this
stream width in this study site is wider (averaging 30 m) and
appears to have significant allochthonous energy input and
ability for PAR to take place in the production of phyto-
plankton.
The allochthonous and autochthonous trophic input of
Denton Creek in the form of nutrients consisting of CPOM,
FPOM, and DOM [7] is critical for food intake of primary,
secondary, tertiary, and quaternary (detritivores) [14, 24].
These nutrients are transported downstream into lentic sys-
tems via hydrochory, an important source of species coloni-
zation of recruitment-limited riparian–wetland communities
which allows for the maintenance of the rich biodiversity of
the communities’ biota [39]. This action also allows new
communities of species to be established downstream far from
the headwaters of streams and rivers. However, this does not
account for the recruitment of riparian species at the head-
waters since there is no dispersal mechanism from the
stream’s beginning point. Dispersal of many plant species at
the upstream (headwaters and tributaries) intercatchment via
groundwater and rainfall runoff is made possible by guano
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from birds, soil and vegetation disturbances by large animals
(e.g., livestock, deer), wind, and other means, and are thereby
carried downstream to propagate [39]. Riparian communities
are considered to be ‘local’ and distinct ecosystems amongst
the landscape of larger, regional ecosystems, whereby the
headwaters may have relatively high dominance of endemic
plants (low diversity) due to fast-moving water, rocky sub-
strate, lower plant nutrients, and colonized with specialized
species of flora and aquatic fauna [42]. But through down-
stream ecological drift, plant species diversity increases
within the community [38]. Within the riparian zone, the flow
of water is cyclic, in that it reaches peak flow and peak ex-
changes during the rainy or monsoon seasons of spring, and
decreases during the summer during low precipitation, and
then in autumn when precipitation increases. Different species
and functional feeding groups are contributors to downstream
ecological drift—from headwaters and first and second-order
tributaries—to higher-order mainstem streams by which in the
vegetation and seed bank, species richness contributes to
higher biodiversity [37-41, 42]. Therefore, this study supports
the theory that hydrochory plays a significant role in plant
colonization and species richness and diversity in riparian
plant communities [37].
The relatively high species diversity amongst the ranked
groups of trees (Figure 6) is consistent with other research
[5-9, 15, 16, 37-41]. The study site at Denton Creek had an
abundance of facultative wetland, facultative riparian, and
facultative upland trees [17], making this a functional creek in
terms of dissipating the energy of stream flow and reducing
floodwater flow, stabilizing banks, reducing erosion, trapping
sediments that pollute waters downstream, creating flood-
plains and floodplain retention, and providing groundwater
recharge. All of whom providing diverse wildlife habitats and
increased water quality [2-7, 10, 17, 21, 23, 43]. However, as
shown in this study, anthropogenic changes to freshwater
streams and rivers makes them highly vulnerable through the
alteration of floodplains, reducing the natural composition of
the stream ecosystem by isolating flora and fauna populations
and their habitats in the riparian community [44].
If we evaluate Denton Creek as a valuable resource for both
human and ecological uses, these data suggest this community
to be of high quality and a valuable and important asset to this
geographical region. In terms of ecological importance, this
riparian hardwood community is rich in habitat diversity that
provides vegetative and protective cover for both flora and
fauna, habitat niche, breeding sites and plant distribution, to
name a few. During the 1999 survey, a family of about 12
North American Wild Turkey (Meleagris gallopavo, a native
upland bird of Texas) were seen along the outer fringes of the
upland tree line. Texas boasts the greatest population of these
upland birds; however, some research has shown that the
American Wild Turkey population is declining due to habitat
loss, e.g. [45]. In terms of human importance, the site has
economic importance, both as a source of crop and domestic
animal production, erosion control, water conservation, and
land value. Human legal factors to consider in the develop-
ment of this tract of land are regulations concerning water
quality, wetland mitigation, endangered and protected species,
and applicable zoning laws. In terms of aesthetic value, one
might consider this site to be priceless, having unique features
such as a scenic environment, diverse plant and animal spe-
cies, or historical importance.
5. Conclusions
In this study, It is shown how the riparian community plays
an important role in the ecological functions of flood control,
bank stabilization, filters and buffers of pollution into the
water, provisions for wildlife habitat, nutrient cycling by way
of capturing and storing nutrients from the surrounding to-
pography, and as a corridor for movement between different
ecosystems. The River Continuum Concept was discussed in
detail as the important link between lotic and lentic systems.
The etymology of lentic comes from the Latin word Lentus,
meaning “calm” or “still”. The Latin word for lotic is Lotus,
which means “to wash”, e.g. fast-moving freshwater. Lotic
systems include rivers, streams and creeks and unlike lentic
systems, lotic systems contain higher species diversity in their
communities. The trees that were surveyed along Denton
Creek in 1999 were aggregated into taxonomical and diameter
size classes, demonstrating that this area was found to be a
highly diverse community of riparian woodlands. Since this
study in 1999, the area has been developed into a multi-family
apartment complex that threatens the ecological structure of
Denton Creek; and is likely to have negatively impacted
downstream community ecosystems, causing irreversible
changes in land use, biodiversity, and the entire health of the
river system of the Elm Fork of the Trinity River. Although it
has been 25 years since the 1999 tree survey, it is not known if
any field studies have been done on the urban affects on this
riparian community directly related to best management
practices of riparian aquatic flora and fauna [50]. As land
continues to become urbanized, profound effects on biodi-
versity, community structure, and species richness. Urban
landscapes tend to have lower biodiversity than pristine eco-
systems [49]. This study is concluded to bring about aware-
ness of land development affecting the sensitive riparian
ecosystem by implementing conservation and management
best practices such as Streamside Management Zones (SMZ)
to buffer forestland adjacent to stream in the way of bank
stabilization and the restriction of sediment and other pollu-
tion loads [51-53] into sensitive riparian ecosystems in hopes
of fostering proper land stewardship by promoting sustainable
land strategies through the implementation of best manage-
ment practices at the local, county, and state levels of natural
resources regulation.
Abbreviations
DBH
Diameter at Breast Height
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16
CE
Current Era
CPOM
Coarse Particulate Organic Matter
FPOM
Fine Particulate Organic Matter
DOM
Dissolved Organic Matter
cm
Centimeters
ft
Foot / Feet
m
Meter / Meters
1 inch
2.54 Centimeters
1 foot
0.304 8 Meter
1 mile
1.609 34 Kilometers
1 acre
0.4046 86 Hectare
Acknowledgments
I want to thank David F. McCullah and Philip E. Adams,
President and Vice President, respectively, of McCullah
Surveying, Inc. and both Registered Professional Land Sur-
veyors in the State of Texas, for supporting my research after
completion of the land survey in 1999. The tree data collected
gave me the idea for putting this manuscript together for
publication.
Author Contributions
David Alan Rolbiecki is the sole author. The author read
and approved the final manuscript.
Funding
This work is not supported by any external funding.
Data Availability Statement
The data supporting the outcome of this research work has
been reported in this manuscript.
Conflicts of Interest
The author declares no conflicts of interest.
Appendix
Appendix 1. Tabular Data of Trees Found Within the Denton Creek Survey
Table 5. Tree count by family, generic and specific epithet, and by diameter at breast height (DBH).
DBH (inches):
3-5"
6-8"
9-12"
13-15"
16-18"
19-21"
22-24"
25-28"
29-36"
37-44"
46"and
above
Total
Elm Family (Ulmaceae)
American Elm
Ulmus americana
40
61
57
16
16
12
13
8
12
2
237
Cedar Elm
U. crassifolia
69
70
18
4
1
1
2
1
166
Slippery Elm
U. rubra
17
12
4
2
35
Winged Elm
U. alata
0
Hackberry
Celtis occidentalis
126
107
54
18
10
4
6
4
2
331
Total Elms:
235
255
141
42
27
19
21
12
15
2
0
769
Beech Family (Fagaceae)
Post Oak
Quercus stellata
6
1
5
1
5
1
11
30
Burr Oak
Q. macrocarpa
2
1
1
1
5
White Oak
Q. alba
3
3
1
1
1
9
Shumard Oak
Q. shumardii
1
1
Blackjack Oak
Q. marilandica
0
Total Oaks:
11
5
7
1
5
1
11
0
1
1
2
45
Walnut Family (Juglandaceae)
Pecan
Carya illinoensis
7
6
1
4
6
24
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DBH (inches):
3-5"
6-8"
9-12"
13-15"
16-18"
19-21"
22-24"
25-28"
29-36"
37-44"
46"and
above
Total
Black Walnut
Juglans nigra
1
1
Total Pecans and Walnuts:
7
6
1
0
1
0
4
0
6
0
0
25
Willow Family (Salicaceae)
Eastern Cot-
tonwood
Populus deltoides
7
1
2
1
2
7
7
4
31
Black Willow
Salix nigra
3
2
3
1
1
10
Total Willows:
10
3
3
1
2
0
1
2
7
7
5
41
Mulberry Family (Moraceae)
Red Mulberry
Morus rubra
13
14
7
34
Osage Orange
(Osage Orange)
Maclura pomifera
10
9
7
2
28
Total Mulberries:
23
23
14
2
0
0
0
0
0
0
0
62
Olive Family (Oleaceae)
Ash
Fraxinus sp.
44
33
35
19
13
10
12
2
9
4
1
182
Total Ashes:
44
33
35
19
13
10
12
2
9
4
1
182
Maple Family (Aceraceae)
Box Elder
Acer negundo
7
15
18
2
2
2
1
47
Total Maples:
7
15
18
2
2
2
1
47
Rose Family (Rosaceae)
Plum
Prunus spp.
3
3
6
Total Roses:
3
3
6
Cypress Family (Cupressaceae)
Cedar (Ash
Juniper)
Juniperus ashei
1
2
2
1
6
Total Cedars:
1
2
2
1
6
Plane-tree Family (Platanaceae)
Sycamore
Platanus occidentalis
1
2
3
1
1
8
Total Sycamores:
1
2
3
1
1
8
Mahogany Family (Meliaceae)
Chinaberry
Melia azedarach
7
1
8
Total Chinaberries:
7
1
8
Rue (citrus) Family (Rutaceae)
Hercules-Club
Zanthoxylum cla-
va-herculis
5
4
9
Total Hercules-club:
5
4
9
Legume Family (Leguminosae)
Eastern Redbud
Cercis canadensis
1
1
Honey Locust
Gleditsia triacanthos
23
11
34
Honey Mesquite
Prosopis glandulosa
43
3
46
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DBH (inches):
3-5"
6-8"
9-12"
13-15"
16-18"
19-21"
22-24"
25-28"
29-36"
37-44"
46"and
above
Total
Total Legumes:
66
15
0
0
0
0
0
0
0
0
0
81
Sapodilla Family (Sapotaceae)
Wooly Buck-
thorn
Bumelia lanuginosa
5
6
11
Total Buckthorns:
5
6
11
Tree Grand Total:
1,300
Appendix 2. Graphical plots of the Most Abundant Tree Families That Were Located in the Denton
Creek survey [Figure 9(a) to Figure 9(h)]
Figure 9. Cumulative frequency curves of the most abundant tree families. Figure 9(a). Elms. Figure 9(b). Ashes. Figure 9(c). Mulberries.
Figure 9(d). Maples. Figure 9(e). Oaks. Figure 9(f). Willows. Figure 9(g). Pecans & Walnuts. Figure 9(h). Cedars and Wooly Buckthorns.
Ecology and Evolutionary Biology http://www.sciencepg.com/journal/eeb
19
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