NatureServe ecologists lead efforts to develop internationally standardized classifications for terrestrial ecosystems and vegetation. One classification approach is terrestrial ecological systems, mid- to local- scale ecological units useful for standardized mapping and conservation assessments of habitat diversity and landscape conditions. Each ecological system type describes complexes of plant communities influenced by similar physical environments and dynamic ecological processes (like fire or flooding). The classification defines some 800 units across the United States and has provided an effective means of mapping ecological concepts at regional/national scales in greater detail than was previously possible.
Terrestrial Plant Ecology Pdf
NatureServe ecologists have combined results of these efforts into a national map depicting distributions as of 2003. Since terrestrial ecological systems are linked to the US National Vegetation Classification, this national map information may be displayed at multiple levels of the National Vegetation Classification hierarchy. Ongoing efforts are resulting in maps of these types across the Americas. Updates are planned for 2015 by federal agencies in the United States.
This phylogenetic tree is based on 164 vascular plant species (consisting of both gymnosperms and angiosperms), which were included to estimate the weighted response ratio of root:shoot ratio, plant total biomass, above- and belowground biomass to warming. Plants in the phylogenetic tree are shown with their mycorrhizal association (AMF arbuscular mycorrhizal fungi, EMF ectomycorrhizal fungi), life form (woody or herb), and growth form (annual or perennial).
We suspect that a stronger association of warming effects on biomass allocation with MAP and mycorrhizal associations could potentially lead to a redistribution of R/S in the horizontal dimension with more homogenization and lower variability of biomass allocation patterns among diverse biomes (Fig. 1)58. Although we found some clear signals in how warming effects were observed through a greater allocation of root biomass in terrestrial plants relative to shoot biomass, we caution readers about the variability in effect sizes, which could be caused by the distinct effect of warming magnitude and warming duration in a given biome (Supplementary Table 3). For example, warming magnitude might negatively affect the response of R/S for biomes with EMF, while warming duration could induce negative and positive effects for biomes with woody and herbaceous plants, respectively, as revealed in our analysis (Supplementary Table 3).
The biome types (including cropland, desert, forest, grassland, tundra, and wetland, Supplementary Table 5), plant functional types (PFTs, including woody plant vs. herb, tree vs. shrub, grass vs. forb, Supplementary Fig. 1), other taxonomy categories (evergreen vs. deciduous tree, broad vs. coniferous leaf tree, annual vs. perennial plant, angiosperm vs. gymnosperm, monoculture vs. mixed plant community, Figs. 2 and 3, Supplementary Table 4) and mycorrhizal fungi types (MFTs, Supplementary Fig. 1 and Supplementary Table 5) for dominant plants in each case study were confirmed based on the original publications and the latest FungalRoot database ( -grin.gov/fungaldatabases/)45. The MFTs of biomes were labeled as AMF, EMF, or AM-EMF if the root symbiosis of dominant plants were arbuscular mycorrhizal fungi (AMF), ectomycorrhizal fungi (EMF), or mixed AMF and EMF (AM-EMF). Most analyses in this study focused on AMF, EMF, and AM-EMF, as biomes with non-mycorrhizal fungi (NMF) were too few to conduct any meta-analysis (Supplementary Fig. 1).
The weighted response ratio (RR++, Eq. (2)), and the standard error of RR++ [s(RR++), Eq. (3)] in each subgroup [e.g., different MFTs (AMF, EMF, or AM-EMF) or PFTs (woody plants or herbs)] were calculated using individual RR(RRij) and its weight (wij), which is the reciprocal of the variance (vij, Eq. (4), Fig. 4).
Plants have evolved a number of mechanisms that are considered to reduce the negative effects of submergence, and which include both metabolical and morphological plasticity (Armstrong et al., 1994a; Vartapetian and Jackson, 1997). Many of the traits of flood-tolerant plants are directed to amelioration of oxygen availability. A well-described example is elongation of the shoot (reviewed in Voesenek et al., 2004), either by increased growth of petioles and lamina (e.g. in Rumex palustris; Voesenek et al., 2003) or by stem elongation (e.g. in rice; Oryza sativa; Kende et al., 1998), which can ultimately restore the contact of the plant with the atmosphere. Once oxygen enters the shoot, within-plant diffusion is enhanced by longitudinal air channels (aerenchyma) in shoot and roots (Visser et al., 1996; Jackson and Armstrong, 1999; Colmer, 2003) and by development of a gas-tight barrier in the roots to prevent oxygen from diffusing into the anaerobic soil (Armstrong 1979; Colmer et al., 1998; Visser et al., 2000). Voesenek et al. (2004) showed, however, that only a subset of flooding-tolerant plant species was capable of significant shoot elongation. These species generally inhabit poorly drained habitats, where floodwater may remain stagnant for a substantial period of the growing season, and shoot elongation is at these sites an efficient solution to avoid oxygen deficiency. Many species, on the other hand, experience submerged conditions that are too deep for the shoot to reach the surface. A straightforward way to reduce shortage of both oxygen and carbohydrates under such conditions would be the continuation of photosynthesis under water. As photosynthesis produces both oxygen and carbohydrates, it might alleviate stress considerably in completely submerged plants.
Our aim is to provide an overview of current knowledge on the importance of underwater photosynthesis for the survival of submerged terrestrial plants. The main factors that change in the underwater environment will be briefly discussed, after which we will summarize the effects of photosynthesis on internal oxygen concentrations.
Many aquatic plants not only rely on their highly specialized growth forms, but have also developed additional carbon dioxide-concentrating mechanisms, which enhance carbon gain under water (Bowes and Salvucci, 1989; Keeley and Santamaria, 1992; Maberly and Madsen, 2002). The most widespread mechanism to increase carbon dioxide availability is the ability to use in photosynthesis (Allen and Spence, 1981; Prins and Elzenga, 1989; Madsen, 1993). This may be achieved by proton extrusion at one side of the leaf, thereby lowering the pH and thus shifting the inorganic carbon equilibrium in favour of carbon dioxide over (Prins et al., 1982; Lara et al., 2002). Alternatively, itself may also be actively taken up (Elzenga and Prins, 1989; Lara et al., 2002). The use of is a carbon-concentrating mechanism, and often coupled to a C4 metabolism, as has been reported for Hydrilla verticillata (Holaday and Bowes, 1980; Spencer et al., 1996; Magnin et al., 1997; Reiskind et al., 1997), Elodea canadensis (Elzenga and Prins, 1989) and Egeria densa (Browse et al., 1979; Casati et al., 2000). This type of metabolism generally relies on a spatial separation between the C3 and C4 carboxylating enzymes, but the characteristic Kranz or bundle sheath anatomy observed in terrestrial plants (Lambers et al., 1998) is most often lacking in aquatic species (Magnin et al., 1997; Reiskind et al., 1997). Separation between the C3 and C4 carboxylating enzymes in aquatic species appears to occur at the cellular level at the chloroplasts (Reiskind et al., 1997; Casati et al., 2000; Rao et al., 2002).
As mentioned above, typical aquatic-like leaves have a specialized leaf form with filamentous, dissected leaves with few or no stomata, which is entirely different from the terrestrial form (Sculthorpe, 1967). Most aquatic leaves of amphibious plants, however, are simply more elongated and thinner and have a higher specific leaf area (SLA) than terrestrial leaves (Nielsen, 1993; Frost-Christensen and Sand-Jensen, 1995). Measurements on the terrestrial plant R. palustris also showed elongated leaves (Fig. 2) and an increased SLA (Mommer et al., 2005), indicating decreased thickness and a relatively increased gas exchange area (Mommer et al., 2004).
The degree to which plants are able to conduct underwater photosynthesis largely depends on the gas exchange capacity of their leaves under water. The development of new, acclimated leaves may therefore be crucial for survival under water. We observed that flooding-tolerant species generally continued to develop new leaves during complete submergence, whereas flooding-intolerant species, such as Daucus carota, were hardly able to develop new leaves under water (Fig. 3A). This inability of flooding-intolerant species to produce new leaves is probably related to shortage of energy, as illustrated by van Eck et al. (2005), who showed that intolerant species such as D. carota were unable to access stored carbohydrates in the taproot. Furthermore, internal aeration in these species may be poor and thus limits underwater plant performance. Flooding-tolerant species had different patterns of leaf formation under water. Rumex palustris showed a continuous turnover of leaves, compensating the loss of older leaves by formation of new acclimated leaves (Fig. 3B), whereas other species, such as Mentha aquatica, had much lower turnover rates, but also continued leaf development (Fig. 3C). Another flood-tolerant species, Oenanthe aquatica, even developed highly dissected leaves under water (L. Mommer unpubl. res.), strongly resembling the submerged leaves of some aquatic heterophyllous Ranunculus species (Bruni et al., 1996; Rascio et al., 1999; Germ and Gaberscik, 2003; Garbey et al., 2004).
The amount of data on the effect of leaf acclimation on the internal gas concentration is very limited. Experiments with microelectrodes measuring internal oxygen concentrations within the petioles of submerged R. palustris plants showed that, even in the dark when the only source of oxygen is uptake from the floodwater, the internal oxygen concentrations were considerably higher in submergence-acclimated plants than in non-acclimated plants (Mommer et al., 2004). This passive diffusion of oxygen from the water column into the plant has been observed previously for aquatic macrophytes such as L. uniflora and L. dortmanna (Sand-Jensen et al., 1982) and seagrasses (Pedersen et al., 1998; Greve et al., 2003; Pedersen et al., 2004). It was remarkable that the internal oxygen concentrations of petioles of submergence-acclimated Rumex plants were almost similar to the oxygen concentrations of the water column (Mommer et al., 2004). This shows clearly that shoot acclimation to submergence is particularly functional with respect to gas exchange capacity between the water column and the plant. 2ff7e9595c
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