Primary production in an impounded baldcypress swamp (Taxodium distichum) at the northern limit of the range

Abstract

The ability of baldcypress (Taxodium distichum) swamps to maintain themselves near the northern limit of their range depends on their levels of production, which is not only a response to climate but also to local environmental factors (e.g., impoundment). We asked if primary production was reduced under impounded conditions and if species' responses to impoundment were individualistic or more generalized. To examine long-term production trends in a permanently impounded baldcypress swamp, a 6-year study of leaf litterfall was conducted in Buttonland Swamp, Illinois, which had been impounded for 10 years before the beginning of the study. Buttonland Swamp is at the northern boundary of the baldcypress swamp region along the Cache River, Illinois, in the Mississippi River Alluvial Valley of the United States. When the litter production of impounded sites was compared to those with natural hydrology in the same region, impounded sites had about half of the total litterfall of natural sites. Overall, leaf litterfall rates declined during the study (201 vs. 113 g m À2 yr À1 ), but the pattern was negatively correlated with water depth, which explained 97% of the variation in the data. Along the transect with the lowest mean minimum water depth (<0.5 cm), leaf litterfall decreased linearly over 6 years from 377 to 154 g m À2 yr À1 . Total leaf litterfall rates were lower at the other three depths (5, 43, and 49 cm mean minimum water depths) and remained below 200 g m À2 yr À1 throughout the study. Acer saccharinum, Nyssa aquatica, and Salix nigra were most responsible for the decline in total leaf litterfall. Amounts of leaf litterfall of T. distichum and Liquidambar styraciflua also generally decreased, while that of Cephalanthus occidentalis increased over time. Because species' responses to environmental factors such as impoundment are individualistic, models should be based on the responses of individual species, rather than on communities. Our study further suggests that the effects of climate change on impounded swamps may differ from those with natural hydrology, since impounded swamps already have reduced production levels. This finding is particularly relevant since the hydrology of the majority of the world's riverine ecosystems has been altered.

Heterogeneous oxygenation of wetland soils with increasing inundation: Redox potential, water depth, and preferential flow paths

“…Results from previous work on the relationship between bald cypress growth and surface‐water depth have been equivocal, with some reporting a negative relationship (Dicke & Toliver, ; Middleton & McKee, ) and some positive (Stahle, VanArsdale, & Cleaveland, ; Young, Keeland, & Sharitz, ). It has been suggested that where wetlands lie above the local water table, increases in surface‐water level may enhance downward delivery of oxygen to the root zone and facilitate growth (Davidson et al, ; Stahle & Cleaveland, ).…”

Restoration of a coastal swamp forest in southeast Brazil

“…Flooded prairies and marshes (Galatowitsch and van der Valk 1996;Pezeshki et al 2000), riparian and gallery forests (Sweeney et al 2002), mangroves (Feller et al 2003) and swamp forests (Keeland et al 1997;McLeod 2000;Middleton and McKee 2005;Raulings et al 2007) have several examples of such initiatives. In the tropical world, similarly, restoration experience accumulates fast.…”

Functional integrity of freshwater forested wetlands, hydrologic alteration, and climate change

“…According to the serial discontinuity concept, the extent to which a dam alters the river floodplain depends on the position of the dam with respect to the floodplain (Ward and Stanford ). Upstream of dams, wetland tree production declines over time if permanently flooded, so that tree regeneration may be relegated to an elevation‐specific ring in the driest part of the impoundment, e.g., Taxodium distichum forests in Buttonland Swamp, Cache River, Illinois (Middleton and Middleton and McKee , respectively). Freshwater tree species have different tolerances to flooding, so that species compositions may “adjust” to flooding over time depending on flooding depth and seasonality.…”