Northern Sandy Drainageway

Description

This ecological site occurs on some of the most actively forming and aggrading landforms of the floodplain environment: the point bars and natural levees. Accordingly, reference conditions of this ecological site are mainly defined by pioneer species that can tolerate excessively drained soils and periodic flooding of varying durations. A minor but often secondary position and occurrence of the soils of this site pertain to overwash channels immediately behind natural levees that were breached during flood events. The coarse sediments often drop out quickly as flood waters enter the forested floodplain, creating complex soil textures.

Natural vegetation of this site is somewhat variable and highly dependent upon landform, stage of development, and/or frequency of flood disturbance and deposition. Newly and actively forming depositional zones (e.g., point bars) generally consists of pioneer species such as black willow, river birch, cottonwood, boxelder, sweetgum, and sycamore (Community Phase 1.1). Older and more stable sites may consist of larger representatives of the former in addition to silver maple, red maple, water oak, willow oak, elm, and ash (Community Phase 1.2). To the south in Mississippi, loblolly pine may enter the community.

By the time that a more mature and diverse plant community develops, soil forming processes may have led to greater soil development and the natural transition toward a different floodplain ecological site (e.g., Northern Alluvial Flat). This older community is often more typical of relict levee and point bar ridges, the latter becoming part of the ridge and swale complex with drier communities occurring on the relict ridges and wetter associations occupying the intervening swales.

Submodel

Description

This state represents the breadth of forest management activities on this site. Various management or silvicultural methods can lead to very different structural and compositional results within a managed stand. The range of methods are diverse and include even-aged (e.g., clearcut and shelterwood) and uneven-aged (single tree, diameter-limit, basal area, group selection, etc.) approaches. Included within these approaches is an option to use disturbance mechanisms (e.g., fire, TSI, etc.) to reduce competition and achieve maximum growth potential of the desired species. Inherently, these various approaches result in different community or “management phases” and possibly alternate states. The decision to represent these varying approaches and management strategies into a single state and phase at this time hinges on the need for additional information in order to formulate definitive pathways, management actions, and community responses. Forthcoming inventories and description iterations of this site will provide more detail on this state and associated management phases.

There are moderate limitations concerning management of this site. This site occurs within floodplain environments and seasonal or periodic flooding will require management activities to occur during drier times of the year. Additionally, the soils of this site are excessively drained, which may cause drought-induced stress to desirable trees and increase seedling mortality.

Submodel

Description

This state is representative of sites that have been converted to and maintained in pasture and forage cropland, typically a grass – legume mixture. However, the excessively drained, sandy soils of this site are generally considered poorly adapted or suited for pasture (Capability Class IIIs). The droughty, nutrient poor soils can lead to severe plant stress during drier periods of the year (USDA-SCS, 1990). If pastureland is pursued on this site, then planning or prescribing the intensity, frequency, timing, and duration of grazing to help maintain desirable forage mixtures at sufficient density and vigor is a necessity (USDA-NRCS, 2010; Green et al., 2006).

Establishing an effective pasture management program can help minimize the rate of weed establishment and assist in maintaining vigorous growth of desired forage. An effective pasture management program includes: selecting well-adapted grass and/or legume species that will grow and establish rapidly; maintaining proper soil pH and fertility levels; using controlled grazing practices; mowing at proper timing and stage of maturity; allowing new seedings to become well established before use; and renovating pastures when needed (Rhodes et al., 2005; Green et al., 2006). It is strongly advised that consultation with State Grazing Land Specialists and District Conservationists at local NRCS Service Centers be sought when assistance is needed in developing management recommendations or prescribed grazing practices.

An additional limitation of this site is seasonal or periodic flooding, especially within unprotected floodplains.

Submodel

Description

This state is representative of sites that have been converted to and maintained in cropland. However, the excessively drained, sandy soils of this site are generally considered poorly suited to unsuited for cropland (Capability Class IIIs). The droughtiness and nutrient leaching of the soils are management concerns. Also, seasonal flooding can limit the production and harvests of some crops. Because of the hazard of flooding in spring, planting short-season annuals such as soybeans or grain sorghum is recommended. Applications of lime and fertilizer are needed to maintain productivity (USDA-NRCS, 1997). However, where this site occurs along stream and riverfronts, fertilizer applications should be appropriately applied and measures implemented to avoid runoff in the adjoining stream system.

Submodel

Description

The inclusion and representation of this altered state, as illustrated in the accompanied STM, is unconventional. The dashed arrow (labeled T1D) of that diagram is meant to emphasize the similarity of the sandy soils and the corresponding vegetation community to that of the reference state. However, the processes leading to the creation and formation of this state is very different and typically associated with an altered or modified environment. Many of these situations are the result of stream modifications, primarily channelization, that have become completely filled with coarse sediments and debris. These channel obstructions are aptly termed “valley plugs”, and they tend to develop where channelized streams lose their gradient profile as the stream approaches the flat, broad floodplains of the receiving stream or river. These obstructions cause stream flow to split and braid around the plugs, which transports floodwater and sediments onto floodplain surfaces. During particularly powerful food events, the channel obstruction can be blown out of the obstructed channel causing tremendous sand splays across portions of the receiving floodplain (Pierce and King, 2007). The impacts of excessive sand deposition onto these areas can alter the functions of the affected site, kill the standing bottomland hardwoods, and alter forest composition (Pierce, 2005).

The model illustrating this state is intended to serve as a feedback loop for other floodplain ecological sites (e.g., Northern Alluvial Flat, Moderately Wet Alluvial Flat, Wet Alluvial Flat, and Backswamp) that have become impacted by excessive sand depositions. These depositional events and the associated “valley plug sand splay” state can and often occurs on all floodplain ecological sites. For each of the floodplain sites, an illustration of this altered state should be provided on the respective STMs along with appropriate discussion in the site narratives. References should be made to this particular site, the Northern Sandy Drainageway, to emphasize the relationship of the valley plug altered state to the remaining three altered states of this site (i.e., the Timber Management - State 2; Pastureland - State 3; and Agriculture Production - State 4).

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