Effect of climate change over the past half century on the distribution,extent and NPP of ecosystems of Inner Mongolia

The response of natural vegetation to climate change is of global concern. In this research, changes in the spatial pattern of major terrestrial ecosystems from 1956 to 2006 in Inner Mongolia of China were analyzed with the Holdridge Life Zone (HLZ) model in a GIS environment, and net primary production (NPP) of natural vegetation was evaluated with the Synthetic model, to determine the effect of climate change on the ecosystem. The results showed that climate warming and drying strongly influenced ecosystems. Decreased precipitation and the subsequent increase in temperature and potential evapotranspiration caused a severe water deficiency, and hence decreased ecosystem productivity. Climate change also influenced the spatial distribution of HLZs. In particular, new HLZs began to appear, such as Warm temperate desert scrub in 1981 and Warm temperate thorn steppe in 2001. The relative area of desert (Cool temperate desert scrub, Warm temperate thorn steppe, Warm temperate desert scrub, Cool temperate desert and Warm temperate desert) increased by 50.2% over the last half century, whereas the relative area of forest (Boreal moist forest and Cool moist forest) decreased by 36.5%. Furthermore, the area of Cool temperate steppe has continuously decreased at a rate of 5.7% per decade; if the current rate of decrease continues, this HLZ could disappear in 173 years. The HLZs had a large shift range with the mean center of the relative life zones of desert shifting northeast, resulting a decrease in the steppe and forest area and an increase in the desert area. In general, a strong effect of climate change on ecosystems was indicated. Therefore, the important role of climate change must be integrated into rehabilitation strategies of ecosystem degradation of Inner Mongolia.     

Genetic variation in productivity of foundation riparian species at the edge of their distribution: implications for restoration and assisted migration in a warming climate

We examined the hypothesis that genotypic variation among populations of commonly co‐occurring phreatophytic trees (Populus fremontii, Salix gooddingii) and the shrub (Salix exigua) regulates aboveground net primary productivity (ANPP) at a hot site at the edge of the species’ distribution. We used a provenance trial in which replicated genotypes from populations varying in mean annual temperature were transplanted to a common garden adjacent to the Lower Colorado River in southeastern California. The garden environment represented an extreme maximum temperature for the study species. Four major findings emerged: (1) Genotypic variation in ANPP was significant for all species with broad‐sense heritability (H²) across populations of 0.11, 0.13, and 0.10 for P. fremontii, S. gooddingii, and S. exigua, respectively, and within‐population H² ranging from 0.00 to 0.25, 0.00 to 0.44, and 0.02 to 0.21, respectively. (2) Population ANPP decreased linearly as mean annual maximum temperature (MAMT) transfer distance increased for both P. fremontii (r² = 0.64) and S. gooddingii (r² = 0.37), whereas it did not change for S. exigua; (3) Populations with similar MAMT to that of the common garden were 1.5 and 1.2 times more productive than populations with 5.0 °C MAMT transfer distances for P. fremontii and S. gooddingii, respectively; and (4) Variation in regression slopes among species for the relationship between ANPP and MAMT indicate species‐specific responses to temperature. As these plant species characterize a threatened habitat type and support a diverse community that includes endangered species, ecosystem restoration programs should consider using both local genotypes and productive genotypes from warmer environments to maximize productivity of riparian ecosystems in the face of global climate change.     

Wind Power Compensation is not for the Birds: An Opinion from an Environmental Economist

This article advocates for better implementation of the Environmental Impact Assessment (EIA) framework as applied to wind power development, with a particular focus on improving compensatory restoration scaling. If properly enforced, the environmental impacts hierarchy “avoid‐minimize‐compensate” provides the regulated community with incentives to prevent wildlife and habitat impacts in sensitive areas and, if necessary, compensate for residual impacts through restoration or conservation projects. Given the increase in legislation requiring resource‐based environmental compensation, methods for scaling an appropriate quantity and quality of resources are of increasing relevance. I argue that Equivalency Analysis (EA) represents a transparent and quantitative approach for scaling compensation in the case of wind power development. Herein, I identify the economic underpinnings of environmental compensation legislation and identify weaknesses in current scaling approaches within wind power development. I demonstrate how the recently completed REMEDE toolkit, which provides guidance on EA, can inform an improved scaling approach and summarize a case study involving raptor collisions with turbines that illustrates the EA approach. Finally, I stress the need for further contributions from the field of restoration ecology. The success of ex ante compensation in internalizing the environmental costs of wind development depends on the effective implementation of the environmental impacts hierarchy, which must effectively encourage avoidance and minimization over environmental restoration and repair.     

Simulated long‐term effects of harvest and biomass residue removal on soil carbon and nitrogen content and productivity for two Upper Great Lakes forest ecosystems

We used the ecosystem process model Biome‐BGC to simulate the effects of harvest and residue removal management scenarios on soil carbon (C), available soil nitrogen (N), net primary production (NPP), and net ecosystem production (NEP) in jack pine (Pinus banksiana Lamb.) and sugar maple (Acer saccharum Marsh) ecosystems in northern Wisconsin, USA. To assess harvest effects, we simulated short (50‐year) and long (100‐year) harvest intervals, high (clear‐cut) and low (selective) harvest intensities, and three levels of residue retention (15%, 25%, and 35%) over a 500‐year period. The model simulation of NPP, soil C accumulation, and NEP agreed reasonably well with biometric and eddy‐covariance measurements of these two ecosystems. The more intensive (50‐year rotation clear‐cuts with low residue retention) harvest scenarios tended to have the greatest NEP (420 and 678 t C ha^?1 for the 500‐year interval for jack pine and sugar maple, respectively). All the harvest scenarios decreased mineral soil C and available mineral soil N content relative to the no‐harvest scenario for jack pine and sugar maple. The rate of change in mineral soil C decreased the greatest in the most intensive biomass removal scenarios (?0.012 and ?0.072 t C ha^?1 yr^?1 relative to no‐harvest for jack pine and sugar maple, respectively) and the smallest decrease was observed in the least intensive biomass removal scenarios (?0.002 and ?0.009 t C ha^?1 yr^?1 relative to no‐harvest for jack pine and sugar maple, respectively). The more intensive biomass removal harvest scenarios in sugar maple significantly decreased peak productivity (NPP) in the simulation period.     

Water and energy footprints of bioenergy crop production on marginal lands

Water and energy demands associated with bioenergy crop production on marginal lands are inextricably linked with land quality and land use history. To illustrate the effect of land marginality on bioenergy crop yield and associated water and energy footprints, we analyzed seven large‐scale sites (9–21 ha) converted from either Conservation Reserve Program (CRP) or conventional agricultural land use to no‐till soybean for biofuel production. Unmanaged CRP grassland at the same location was used as a reference site. Sites were rated using a land marginality index (LMI) based on land capability classes, slope, soil erodibility, soil hydraulic conductivity, and soil tolerance factors extracted from a soil survey (SSURGO) database. Principal components analysis was used to develop a soil quality index (SQI) for the study sites based on 12 soil physical and chemical properties. The water and energy footprints on these sites were estimated using eddy‐covariance flux techniques. Aboveground net primary productivity was inversely related to LMI and positively related to SQI. Water and energy footprints increased with LMI and decreased with SQI. The water footprints for grain, biomass and energy production were higher on lands converted from agricultural land use compared with those converted from the CRP land. The sites which were previously in the CRP had higher SQI than those under agricultural land use, showing that land management affects water footprints through soil quality effects. The analysis of biophysical characteristics of the sites in relation to water and energy use suggests that crops and management systems similar to CRP grasslands may provide a potential strategy to grow biofuels that would minimize environmental degradation while improving the productivity of marginal lands.     

Seasonal CO<Subscript>2</Subscript>-exchange variations of temperate semi-desert grassland in Hungary

CO₂ exchange components of a temperate semi-desert sand grassland ecosystem in Hungary were measured 21 times in 2000–2001 using a closed IRGA system. Stand CO₂ uptake and release, soil respiration rate (R _s), and micrometeorological values were determined with two types of closed system chambers to investigate the daily courses of gas exchange. The maximum CO₂ uptake and release were –3.240 and 1.903 mol m^–2 s^–1, respectively, indicating a relatively low carbon sequestration potential. The maximum and the minimum R _s were 1.470 and 0.226 mol(CO₂) m^–2 s^–1, respectively. Water shortage was probably more effective in decreasing photosynthetic rates than R _s, indicating water supply as the primary driving variable for the sink-source relations in this ecosystem type.     

Role of changing environmental parameters in leaf gas exchange of <Emphasis Type="Italic">Arbutus unedo</Emphasis> L. assessed by field and laboratory measurements

In the frame of the foreseen climate global changes we analysed the physiological responses of Arbutus unedo L. to the variations of carbon dioxide concentration, leaf temperature, and irradiance by measurements of leaf gas exchange and leaf water potential performed both in field and in the laboratory. Stomatal conductance was not affected by increase of leaf temperature. The growth conditions of potted plants likely made stomata more sensitive to the variation of external parameters than naturally growing plants. The interaction between high CO₂ concentration and temperature involved important down-regulation mechanisms in the metabolic pathway of the carbon fixation. From an ecological point of view, the ability of A. unedo to adapt to the field stress makes it highly competitive in the Mediterranean plant community.     

Effects of grazing on photosynthetic characteristics of major steppe species in the Xilin River Basin,Inner Mongolia,China

Species composition and photosynthetic characteristics of dominant species of ungrazed plot (UG), overgrazed plot (OG), and restored grazed plot (RG) were determined in the Xilin River Basin, Inner Mongolia, China. Both heavily grazing and restoration significantly affected the composition of different species and life forms. Leymus chinensis, Stipa grandis, and Cleistogenes polyphylla, three dominant perennial grasses in UG plot, contributed 58.9 % aboveground biomass to that of whole community, and showed higher net photosynthetic rate (P _N), transpiration rate (E), and intrinsic water-use efficiency (WUE). In OG plot, relative biomass of L. chinensis and S. grandis significantly decreased, while relative biomass of three shrubs/sub-shrubs, Caragana microphylla, Artemisia frigida, and Kochia prostrata, obviously increased. Heavy grazing significantly decreased P _N, E, and WUE of L. chinensis and S. grandis, while shrubs/sub-shrubs showed significantly higher photosynthetic activity and WUE than the grasses. After 18-year restoration, photosynthetic activities of L. chinensis and S. grandis were significantly higher than those in the OG plot. The proportion of L. chinensis, S. grandis, and C. microphylla significantly increased, and relative biomass of C. polyphylla, A. frigida, and K. prostrata markedly declined in RG plot. We found close relationships between physiological properties of species and their competitive advantage in different land use types. Higher photosynthetic capability means more contribution to total biomass. The variations in physiological characteristics of plants could partly explain the changes in species composition during degrading and restoring processes of Inner Mongolia typical steppes.     

Water relations,chlorophyll <Emphasis Type="Italic">a</Emphasis> fluorescence,and contents of saccharides in tree species of a tropical forest in response to flood

We studied the seasonal changes in water relations, chlorophyll a fluorescence, and leaf saccharide contents of the tropical flood-tolerant trees Acosmium nitens, Campsiandra laurifolia, Eschweilera tenuifolia, Symmeria paniculata, and Psidium ovatifolium. Xylem water potential increased with flooding to a larger extent than leaf sap osmotic potential in all the species, and soluble sugars contributed up to 66 % of osmotic potential at maximum flooding. Starch was accumulated in leaves. Maximum quantum yield of photosystem 2 decreased in emerged leaves, values being always higher than 0.76. Daily maximum net photosynthetic rate and leaf conductance decreased in all the species. This reduction was associated in all the species but S. paniculata with the absence of a compensatory increase in non-photochemical quenching.This research was financially supported by CONICIT grant S1-96001345. E. Rengifo was funded by a CONICIT scholarship.     

Leaf development and photosynthetic properties of three tropical tree species with delayed greening

Leaf developmental patterns were characterized for three tropical tree species with delayed greening. Changes in the pigment contents, photosynthetic capacity, stomata development, photosystem 2 efficiency, rate of energy dissipation, and the activity of partial protective enzymes were followed in developing leaves in an attempt to elucidate the relative importance of various photoprotective mechanisms during leaf ontogeny. Big leaves of Anthocephalus chinensis, a fast-growing light demanding species, expanded following an exponential pattern, while relatively small leaves of two shade-tolerant species Litsea pierrei and Litsea dilleniifolia followed a sigmoidal pattern. The juvenile leaves of A. chinensis and L. pierrei contained anthocyanin located below the upper epidermis, while L. dilleniifolia did not contain anthocyanin. Leaves of A. chinensis required about 12 d for full leaf expansion (FLE) and photosynthetic development was delayed 4 d, while L. pierrei and L. dilleniifolia required 18 or 25 d for FLE and photosynthetic development was delayed 10 or 15 d, respectively. During the leaf development the increase in maximum net photosynthetic rate was significantly related to changes in stomatal conductance and the leaf maturation period was positively related to the steady-state leaf dry mass per area for the three studied species. Dark respiration rate of leaves at developing stages was greater, and pre-dawn initial photochemical efficiency was lower than that of mature leaves. Young leaves displayed greater energy dissipation than mature leaves, but nevertheless, the diurnal photoinhibition of young L. dilleniifolia leaves was higher than that of mature leaves. The young red leaves of A. chinensis and L. pierrei with high anthocyanin contents and similar diurnal photoinhibition contained more protective enzymes (superoxide dismutase, ascorbate peroxidase) than mature leaves. Consequently, red leaves may have higher antioxidant ability.