Plant distribution, stature, rarity, and diversity in a patterned calcareous fen: tests of geochemical and leaf‐height models

Abstract

Premise In patterned fens, patches of short, sparse, species‐rich vegetation often occur on substrates rich in precipitated carbonates near calcareous springheads, with taller, denser vegetation farther away. Boyer and Wheeler (1989) hypothesized that phosphorus co‐precipitation near springheads limits plant productivity and coverage, and Givnish (1982) proposed that aggregations of rare, short‐statured plant species might reflect their competitive restriction to sparsely covered microsites. Methods We tested these hypotheses by quantifying species distributions, leaf heights, plant coverage, community composition, and substrate and leaf chemistry of Eupatorium perfoliatum along a gradient of hydrology and geochemistry in a wetland complex in southeastern Wisconsin, USA, ranging from marl flats and fens on peat mounds near springheads to surrounding sedge meadows. Results Community composition was strongly correlated with a one‐dimensional environmental gradient along which coverage and height increased moving downslope from marl flats, while soil carbonate, phosphorus immobilization capacity, and local species richness decreased, consistent with theory. Regionally rare species were short and restricted to sparsely covered microsites; within and among species, leaf height increased with local coverage. NPK tissue stoichiometry did not entirely support the Boyer‐Wheeler hypothesis, although nitrogen limitation appeared strongest in sedge meadows. Shifts in stature and tissue chemistry of E. perfoliatum along the marl flat–sedge meadow gradient suggested that zinc toxicity may help limit coverage near springheads despite no significant change in soil zinc content. Conclusions We propose a modified Boyer‐Wheeler hypothesis to account for cascading effects of phosphorus co‐precipitation near springheads on nitrogen fixation, nitrogen+phosphorus co‐limitation, and zinc mobility.

Functional traits mediate individualistic species‐environment distributions at broad spatial scales while fine‐scale species associations remain unpredictable

“…Many of these responses are consistent with economic theory and previous studies of plant ecophysiology, supporting our hypothesis that traits would predictably mediate species‐environment distributions (H1). For example, we find taller plants at sites with higher soil fertility (Figure 4E ), as expected given that optimal leaf height increases in sites where higher soil fertility supports denser plant coverage (Givnish, 1982 , 1995 ; Leach and Givnish, 1999 ; Wernerehl and Givnish, 2015 ; Stockmeier and Givnish, 2019 ). Greater soil fertility also generally increases photosynthetic capacity, favoring plants with greater leaf N and SLA (Givnish, 1979 ; Mooney and Gulmon, 1982 ).…”

A new carnivorous plant lineage (Triantha) with a unique sticky-inflorescence trap

“…Triantha occur not only in nutrient-poor bogs but also in highly calcareous fens, where P and N are also likely to be limiting (26,27). Is carnivory found elsewhere in Triantha?…”

Leaf NPK stoichiometry, δ15N, and apparent nutrient limitation of co‐occurring carnivorous and noncarnivorous plants

“…Despite the low leaf percentage P in sedges, sedges are N limited, not P limited at Fallison Bog. The minerotrophic, moderately to highly productive wet meadows that sedges frequently dominate are generally N limited (unless they have Ca‐ or Fe‐rich flows), presumably because cold, wet, anoxic conditions often work against N fixation but allow denitrification to proceed (Olde Venterink et al, 2003; Stockmeier & Givnish, 2019; Van Buren & Pegtel, 2000). The low N:K ratio in sedges is puzzling but appears to reflect higher leaf concentrations of K more than low N concentrations (Table 1).…”

“…The stoichiometric mismatch between consumers and their prey-and especially between high N, high P herbivores and low N, low P plants-has shed light on dietary constraints, food web structure, and limits on productivity. The mismatch between the stoichiometry of soil nutrient supplies and plant requirements has been the basis of important ecological models for plant distribution, form, and diversity (Diekmann & Falkengren-Grerup, 2002;Tilman, 1982Tilman, , 1988 and the limitation of plant productivity by N versus P (Chadwick et al, 1999;Olde Venterink et al, 2003;Stockmeier & Givnish, 2019;Vitousek, 2004;Vitousek & Farrington, 1997). Stable isotope analyses have played a complementary role in helping trace C and N flows through food webs (Post, 2002) and quantifying the sources of Ca and P during primary succession (Chadwick et al, 1999;Vitousek, 2004).…”