Grassland Mixtures Research Articles

The effect of drought and interspecific interactions on depth of water uptake in deep- and shallow-rooting grassland species as determined by δ<sup>18</sup>O natural abundance

Abstract. Increased incidence of drought, as predicted under climate change, has the potential to negatively affect grassland production. Compared to monocultures, vertical belowground niche complementarity between shallow- and deep-rooting species may be an important mechanism resulting in higher yields and higher resistance to drought in grassland mixtures. However, very little is known about the belowground responses in grassland systems and increased insight into these processes may yield important information both to predict the effect of future climate change and better design agricultural systems to cope with this. This study assessed the effect of a 9-week experimental summer drought on the depth of water uptake of two shallow-rooting species (Lolium perenne L. and Trifolium repens L.) and two deep-rooting species (Cichorium intybus L. and Trifolium pratense L.) in grassland monocultures and four-species mixtures by using the natural abundance δ18O isotope method. We tested the following three hypotheses: (1) drought results in a shift of water uptake to deeper soil layers, (2) deep-rooting species take up a higher proportion of water from deeper soil layers relative to shallow-rooting species, and (3) as a result of interspecific interactions in mixtures, the water uptake of shallow-rooting species becomes shallower when grown together with deep-rooting species and vice versa, resulting in reduced niche overlap. The natural abundance δ18O technique provided novel insights into the depth of water uptake of deep- and shallow- rooting grassland species and revealed large shifts in depth of water uptake in response to drought and interspecific interactions. Compared to control conditions, drought reduced the proportional water uptake from 0–10 cm soil depth (PCWU0–10) of L. perenne, T. repens and C. intybus in monocultures by on average 54%. In contrast, the PCWU0–10 of T. pratense in monoculture increased by 44%, and only when grown in mixture did the PCWU0–10 of T. pratense decrease under drought conditions. In line with hypothesis (2), in monoculture, the PCWU0–10 of shallow-rooting species L. perenne and T. repens was 0.53 averaged over the two drought treatments, compared to 0.16 for the deep-rooting C. intybus. Surprisingly, in monoculture, water uptake by T. pratense was shallower than for the shallow-rooting species (PCWU0–10 = 0.68). Interspecific interactions in mixtures resulted in a shift in the depth of water uptake by the different species. As hypothesised, the shallow-rooting species L. perenne and T. repens tended to become shallower, and the deep-rooting T. pratense made a dramatic shift to deeper soil layers (reduction in PCWU0–10 of 58% on average) in mixture compared to monoculture. However, these shifts did not result in a reduction in the proportional similarity of the proportional water uptake from different soil depth intervals (niche overlap) in mixtures compared to monocultures. There was no clear link between interspecific differences in depth of water uptake and the reduction of biomass production under drought compared to control conditions (drought resistance). Cichorium intybus, the species with water uptake from the deepest soil layers was one of the species most affected by drought. Interestingly, T. pratense, which was least affected by drought, also had the greatest plasticity in depth of water uptake. This suggests that there may be an indirect effect of rooting depth on drought resistance, as it determines the potential plasticity in the depth of water uptake.

Soil biochar amendment in a nature restoration area: effects on plant productivity and community composition.

Biochar (pyrolyzed biomass) amendment to soils has been shown to have a multitude of positive effects, e.g., on crop yield, soil quality, nutrient cycling, and carbon sequestration. So far the majority of studies have focused on agricultural systems, typically with relatively low species diversity and annual cropping schemes. How biochar amendment affects plant communities in more complex and diverse ecosystems that can evolve over time is largely unknown. We investigated such effects in a field experiment at a Dutch nature restoration area. In April 2011, we set up an experiment using biochar produced from cuttings collected from a local natural grassland. The material was pyrolyzed at 400 degrees C or at 600 degrees C. After biochar or residue (non-pyrolyzed cuttings) application (10 Mg/ha), all plots, including control (0 Mg/ ha) plots, were sown with an 18-species grassland mixture. In August 2011, we determined characteristics of the developed plant community, as well as soil nutrient status. Biochar amendment did not alter total plant productivity, but it had a strong and significant effect on plant community composition. Legumes were three times as abundant and individual legume plants increased four times in biomass in plots that received biochar as compared to the control treatment. Biomass of the most abundant forb (Plantago lanceolata) was not affected by biochar addition. Available phosphorous, potassium, and pH were significantly higher in soils that received biochar than in Control soils. The rate of biological nitrogen fixation and seed germination were not altered by biochar amendment, but the total amount of biological N fixed per Trifolium pratense (red clover) plant was more than four times greater in biochar-amended soil. This study demonstrates that biochar amendment has a strong and rapid effect on plant communities and soil nutrients. Over time these changes may cascade up to other trophic groups, including above- and belowground organisms. Our results emphasize the need for long-term studies that examine not only the short-term effects of biochar amendment, but also follow how these effects evolve over time and affect ecosystem functioning.

Winter warming pulses differently affect plant performance in temperate heathland and grassland communities

AbstractWinter air temperature variability is projected to increase in the temperate zone whereas snow cover is projected to decrease, leading to more variable soil temperatures. In a field experiment winter warming pulses were applied and aboveground biomass and root length of four plant species were quantified over two subsequent growing seasons in monocultures and mixtures of two species. The experiment was replicated at two sites, a colder upland site with more snow and a warmer, dryer lowland site. Aboveground biomass of Holcus lanatus declined (−29 %) in the growing season after the warming pulse treatment. Its competitor in the grassland mixture, Plantago lanceolata, profited from this decline by increased biomass production (+18 %). These effects disappeared in the second year. There was a strong decline in biomass for P. lanceolata at the lowland site in the second year. These two species also showed a decline in leaf carbohydrate content during the manipulation. Aboveground productivity and carbohydrate content of the heathland species was not affected by the treatment. The aboveground effects of the treatment did not differ significantly between the two sites, thereby implying some generality for different temperate ecosystems with little and significant amount of snowfall. Root length increased directly after the treatment for H. lanatus and for Calluna vulgaris with a peak at the end of the first growing season. The observed species‐specific effects emphasize the ecological importance of winter temperature variability in the temperate zone and appear important for potential shifts in community composition and ecosystem productivity.

Late Pleistocene mammalian fauna from Wulanmulan Paleolithic Site, Nei Mongol, China

Discovered in 2010 with the construction of Landscape Park on the left bank of Wulanmulun River in Kangbashi District of Nei Mongol, Wulanmulun Paleolithic Site yielded large quantities of mammalian specimens during 2010–2012 rescue excavations. Identified fossil materials include Myospalax sp., Cricetulus sp., Microtus sp., Apodemus sp., Arvicola sp.?, Dipodidae gen. et sp. indet., Lepus sp., Mustelidae gen. et sp. indet., Coelodonta antiquitatis, Equus przewalskii, Camelus cf. C. knoblochi Megaloceros ordosianus and Gazella sp. The fauna analyses show that the paleoenvironment in Wulanmulun Site area might have been a mixture or mosaic of grassland and forest with some small streams and swamps. The fluctuation of annual temperature might have been high, with the winter very cold and the summer relatively warm. The Wulanmulun fauna is in the same paleozoogeographic sub-province as Baotou, Shiyu, Salawusu and Loufangzi faunas, different from that of the Xiaogushan and Yanjiagang faunas of Northeast China, and more different from that of the Dantu fauna of East China. The Wulanmulun area was suitable for the habitation of the late Paleolithic humans, and Wulanmulun fauna were their main hunting prey.

VEGETATION COVERAGE AND MONSOON VARIATION RECORDED BY STABLE CARBON ISOTOPE OF LOES SINCE 2.5MA

The organic carbon isotopes of the Luochuan section show that the δ13C values vary from-18.7‰ to-23.5‰,and the downcore distribution of organic carbon isotope could be divided into three stages with similar trends with the magnetic susceptibility in the glacial-interglacial scales.The results demonstrate that 1) the vegetation coverage in the Luochuan area was mainly a mixture of C3 and C4 grassland,2) the δ13C value of loess sequence better recorded the summer monsoon change in the glacial-interglacial scales just as magnetic susceptibility trend.Comparing with the organic carbon isotope of the Duanjiapo and Weinan sections,two times of evident transition on tectonic time scales are recognized since 2.5 Ma.

Effect of four plant species on soil 15N-access and herbage yield in temporary agricultural grasslands

Background and aims We carried out field experiments to investigate if an agricultural grassland mixture comprising shallow- (perennial ryegrass: Lolium perenne L.; white clover: Trifolium repens L.) and deep- (chicory: Cichorium intybus L.; Lucerne: Medicago sativa L.) rooting grassland species has greater herbage yields than a shallowrooting two-species mixture and pure stands, if deep-rooting grassland species are superior in accessing soil 15 N from 1.2 m soil depth compared with shallow-rooting plant species and vice versa, if a mixture of deep- and shallow-rooting plant species has access to greater amounts of soil 15 N

N2 fixation, N transfer, and yield in grassland communities including a deep-rooted legume or non-legume species

Legumes are important components of grassland mixtures due to their ability to sustain high yields with moderate nitrogen inputs. This study investigates nitrogen relationships in mixtures of Trifolium pratense and grasses into which a deep-rooted forb was included, and particularly whether these realtionships differ when the forb is a legume or a non-legume species. A field experiment in which mixtures of T. pratense, Phleum pratense, Lolium perenne, and Medicago sativa or Cichorium intybus, and monocropped stands of all species was established in 2007 and harvested in 2008 and 2009. The experiment received a total input of 100 kg ha−1 N yearly. Yield and botanical composition were determined in seven harvests. Species were analysed for 15N abundance, and N2 fixation and N transfer were calculated. Soil samples were analysed twice for inorganic N. Non-legumes benefitted from the presence of legumes in terms of N concentration, and the yield of mixtures exceeded that of monocropped non-legumes but not monocropped legumes. The mixture containing M. sativa did not yield more DM or N than did the mixture containing C. intybus. A total of 17.08 kg N ha−1 was transferred from T. pratense to the non-legumes in the mixture in which it was the sole legume species. It is concluded that there was a synergy effect in species mixtures, but the effect did not differ between the two deep-rooted species.

Ecosystem function enhanced by combining four functional types of plant species in intensively managed grassland mixtures: a 3‐year continental‐scale field experiment

SummaryA coordinated continental‐scale field experiment across 31 sites was used to compare the biomass yield of monocultures and four species mixtures associated with intensively managed agricultural grassland systems. To increase complementarity in resource use, each of the four species in the experimental design represented a distinct functional type derived from two levels of each of two functional traits, nitrogen acquisition (N2‐fixing legume or nonfixing grass) crossed with temporal development (fast‐establishing or temporally persistent). Relative abundances of the four functional types in mixtures were systematically varied at sowing to vary the evenness of the same four species in mixture communities at each site and sown at two levels of seed density.Across multiple years, the total yield (including weed biomass) of the mixtures exceeded that of the average monoculture in >97% of comparisons. It also exceeded that of the best monoculture (transgressive overyielding) in about 60% of sites, with a mean yield ratio of mixture to best‐performing monoculture of 1·07 across all sites. Analyses based on yield of sown species only (excluding weed biomass) demonstrated considerably greater transgressive overyielding (significant at about 70% of sites, ratio of mixture to best‐performing monoculture = 1·18).Mixtures maintained a resistance to weed invasion over at least 3 years. In mixtures, median values indicate <4% of weed biomass in total yield, whereas the median percentage of weeds in monocultures increased from 15% in year 1 to 32% in year 3.Within each year, there was a highly significant relationship (P < 0·0001) between sward evenness and the diversity effect (excess of mixture performance over that predicted from the monoculture performances of component species). At lower evenness values, increases in community evenness resulted in an increased diversity effect, but the diversity effect was not significantly different from the maximum diversity effect across a wide range of higher evenness values. The latter indicates the robustness of the diversity effect to changes in species' relative abundances.Across sites with three complete years of data (24 of the 31 sites), the effect of interactions between the fast‐establishing and temporal persistent trait levels of temporal development was highly significant and comparable in magnitude to effects of interactions betweenN2‐fixing and nonfixing trait levels of nitrogen acquisition.Synthesis and applications. The design of grassland mixtures is relevant to farm‐level strategies to achieve sustainable intensification. Experimental evidence indicated significant yield benefits of four species agronomic mixtures which yielded more than the highest‐yielding monoculture at most sites. The results are relevant for agricultural practice and show how grassland mixtures can be designed to improve resource complementarity, increase yields and reduce weed invasion. The yield benefits were robust to considerable changes in the relative proportions of the four species, which is extremely useful for practical management of grassland swards.

What happens to the sown species if a biodiversity experiment is not weeded?

Studies in experimental grasslands have extensively documented the effects of sown plant diversity on the colonization of new species, but the responses of the sown plant combinations themselves have rarely been investigated. We established experimental grasslands differing in species richness (1, 2, 4, 8, and 16) and functional group number and composition (1–4; legumes, grasses, small herbs, tall herbs), and we studied the changes in the abundance of sown species (residents) in both weeded and non-weeded subplots over a period of five years after sowing. The accumulation of new species through spontaneous colonization in the non-weeded treatment did not affect the number of resident species, but had increasingly negative effects over time on the cover of resident species and their aboveground biomass production at community level. Temporal stability of resident populations was lower and year-to-year changes in resident species composition were larger in non-weeded than in weeded subplots. Compositional dissimilarity between weeded and non-weeded treatments increased through time. These negative effects of the colonization of new species on the abundances and stability of resident populations depended on resident species identity and not on additional variation between different functional groups. The colonization of new species did not change the number of resident species emerging from seeds, but reduced seedling densities of residents. Colonization did not affect the structure of resident communities as measured by species evenness, functional trait diversity and mean trait values suggesting that colonization can destabilize the species composition of residents in terms of abundance while leaving them unchanged in terms of functional characteristics. Generally, negative impacts of colonizing species on residents which accelerated through time decreased with an increasing number of sown species. Sowing more diverse grassland mixtures increases their predictability in terms of ecosystem characteristics, which is important for ecological restoration and sustainable agriculture.

Seasonal Habitat Partitioning between Sympatric Terrestrial and Semi-Arboreal Japanese Wood Mice,Apodemus speciosusandA. argenteusin Spatially Heterogeneous Environment

Abstract. Habitat partitioning can maintain the coexistence of species with very similar ecological traits. We studied habitat partitioning between terrestrial and semi-arboreal congeneric rodents (Apodemus speciosus and A. argenteus) that often coexist despite asymmetry in their competitive abilities. To understand seasonal and habitat variation in their partitioning, we evaluated seasonal variation in food resources, habitat use, and habitat similarity between the species in a site comprising a mixture of grassland, pine forest, and mixed forest. Food resources were available on the ground in all vegetation types in spring and autumn, but were severe in summer. Apodemus speciosus was observed in all types of vegetation on the ground. In contrast, A. argenteus was observed on the ground and on trees in pine forest, especially areas where the understory is covered by dwarf bamboo. Habitat similarity tests revealed that habitat partitioning between two Apodemus species may vary seasonally, and the relation...

Reintroduction of grazing management after deforestation of formerly abandoned grassland and its effect on early vegetation changes in the Western Carpathians (Slovakia)

AbstractAlthough the process of reforestation of grassland has been widely studied in Europe, little is known about the effect of deforestation on grassland development. Thus, the specific objective of this study was to evaluate early changes in plant species composition, functional group, yield and biomass quality after deforestation of long‐term abandoned pastures. The experiment was established immediately after deforestation on sparse herbaceous vegetation (mean initial cover 27%) with the following treatments: grazing management only (G0), cutting and grazing aftermath (CG), grazing after seeding of grassland mixture (GS), grazing after a burning treatment in which branches were burned after deforestation (GB) and unmanaged control (U). Very rapid recovery of bare ground by germination and/or sprouting of grassland species was similar under all types of grazing management. Total plant species richness increased in all managed treatments except GB. Similarities according to redundancy analyses in plant species composition were found among G0, CG and GB treatments, especially for forbs with correlated rosette or creeping growth. The woody species, tall grasses and tall forbs had higher abundance in the U treatment. The restoration of grassland following deforestation of formerly reforested grassland area by grazing management was a relatively fast process, and swards were created after 3 years. The highest biomass yield was observed under treatments GS and GB. Forage quality of all managed treatments was sufficient for the demands of beef cattle grazing. However, for subsequent grassland preservation, some type of grazing management is necessary to prevent reforestation, which can occur immediately after deforestation in unmanaged places.

The role of roots in the resource economics spectrum

The role of roots in the resource economics spectrum

High value of short rotation coppice plantations for phytodiversity in rural landscapes

AbstractThe demand for wood from short rotation coppice (SRC) plantations as a renewable energy source is currently increasing and could affect biodiversity in agricultural areas. The objective was to evaluate the contribution of SRC plantations to phytodiversity in agricultural landscapes assessed as species richness, species–area relationships, Shannon indices, detrended correspondence analysis on species composition, Sørensen similarities, habitat preference proportions, and species proportions found in only one land use. Vegetation surveys were conducted on 12 willow (Salix spp.) and three poplar (Populus spp.) coppice sites as well as on surrounding arable lands, grasslands and forests in central Sweden and northern Germany. SRC plantations were richer in plant species (mean: 30 species per 100 m²) than arable land (10), coniferous forests (13) and mixed forests in Germany (12). Comparing SRC plantations with other land uses, we found lowest similarities in species composition with arable lands, coniferous forests and German mixed forests and highest similarities with marginal grassland strips, grasslands and Swedish mixed forests. Similarity depended on the SRC tree cover: at increased tree cover, SRC plantations became less similar to grasslands but more similar to forests. The SRC plantations were composed of a mixture of grassland (33%), ruderal (24%) and woodland (15%) species. Species abundance in SRC plantations was more heterogeneous than in arable lands. We conclude that SRC plantations form novel habitats leading to different plant species composition compared to conventional land uses. Their landscape‐scale value for phytodiversity changes depending on harvest cycles and over time. As a structural landscape element, SRC plantations contribute positively to phytodiversity in rural areas, especially in land use mosaics where these plantations are admixed to other land uses with dissimilar plant species composition such as arable land, coniferous forest and, at the German sites, also mixed forest.

Net ammonification as influenced by plant diversity in experimental grasslands

Previous plant diversity experiments have mainly reported positive correlations between diversity and N mineralization. We tested whether this relationship can be explained by plant diversity-induced changes i) in the quantity or quality of organic matter or ii) in microclimatic conditions of central European grassland mixtures.We measured ex-situ net ammonification in a laboratory incubation of aboveground plant material and soil sampled in differently diverse plant mixtures. Secondly, in-situ net ammonification was assessed in a field incubation with mineralization cores containing standardized material in four treatments: soil only (control), and soil mixed with field-fresh plant tissue (grass, legume, or tall herb). We used 82 plots with varying species numbers (1, 2, 4, 8, 16, and 60) and numbers of functional groups (1–4; grasses, short herbs, tall herbs, and legumes). We determined the soil water content, total N concentrations of plant and soil, and NH4–N release rates.In the ex-situ incubation under constant climatic conditions, functional group or plant species richness did not influence net ammonification rate constants (k) or the proportion of the organic N pool involved in ammonification (NH4–N0). The presence of legumes in plant mixtures significantly increased NH4–N0 and decreased k indicating elevated N leaching risks in legume-containing grassland mixtures. Mean in-situ net ammonification rates in the mineralization cores decreased in the following order: mixtures of soil with grasses (0.30 ± standard error 0.01 mg NH4–N (g Ninitial)−1 d−1) > tall herbs (0.25 ± 0.01) > legumes (0.22 ± 0.01) > control (0.07 ± 0.00). The type of incubated plant tissue also influenced the soil water content in the mineralization cores at the end of field incubation, likely because of different water retention capacities of the different plant tissue/soil mixtures. Significant plant functional group and species richness effects explained up to 13% of the variance of in-situ net ammonification rates. Because the effect of plant species richness disappeared if the type of incubated plant tissue and the soil water content were accounted for in a sequential ANCOVA, we infer that the soil water content was the main driver underlying the plant species richness effect.

珠三角城市绿地CO2通量的季节特征

Urban green space plays a significant role on carbon cycling in urban areas.Accurate estimation of CO2 fluxes above urban green space using the long-term field observation method provides critical information about climate change reactions and regional carbon sequestration evaluations.Continuous eddy-covariance measurements of CO2 fluxes were conducted to analyze the carbon exchange status in 2009 and 2010.The analyses included daily variations in the CO2 fluxes during different seasons,annual variations in light response parameters,including apparent light use efficiency(α) and maximum photosynthetic productivity(Pmax).Annual variations in the net ecosystem CO2 exchange(NEE) and the ecosystem respiration(Reco) were also studied. A tower located in the botanical garden of Dongguan with 4 levels and a total height of 20 m was used for the measurements.The CO2 flux at a height of 20 m was analyzed to study the CO2 exchange between an urban green space and the atmosphere interface.According to the eddy-covariance method and the detection limits of the instrument,abnormal data were removed to ensure accuracy.The daytime NEE and the photosynthetic active radiation(PAR) were used to formulate the Michaelis-Menten model as the gap-filling model during the daytime,while the night respiration(Reco) and soil temperature at 5 cm depth(Ts) were used to calculate the exponential equation as the gap-filling model at night. The major results were:(1) the NEE was-91.9 gC·m-2·a-1 in 2009 and-116.5 gC·m-2·a-1 in 2010,indicating that urban green space was a net carbon sink.The NEE varied seasonally with environmental factors.Urban green space was a carbon source from December-March and a carbon sink from April-November each year.(2) The daily total CO2 flux(Fc) was negative during the winter,but positive during the other seasons.CO2 storage(Fs) occupied a larger proportion during winter than during the other seasons.Daily CO2 concentrations(Cc) were highest before sunrise and lowest after sunset.Cc was highest in the winter and lowest in the summer.(3) The annual average α was(0.00134±0.00035) mgCO2·μmol-1Photons and Pmax was(1.006±0.283) mgCO2·m-2·s-1.(4) The annual Reco was 1370.4 gC·m-2·a-1 in 2009 and 1384.8 gC·m-2·a-1 in 2010.Reco varied with changes in the soil temperature during the year.The simulated Reco during the night was less than the daytime result produced by the Michaelis-Menten model at the same temperature.(5) Because the urban green space was a mixture of forest and grassland,the NEE of the urban green space was smaller than that of a forest ecosystem,but larger than a grassland ecosystem.Compared with other urban green spaces,the NEE in Dongguan was lower than northern urban forests due to the high Reco caused by high temperatures.(6) Correlation analyses between the NEE and meteorological factors like the PAR,air temperature(Ta) and saturation vapor pressure differential(VPD) were performed.The partial correlation coefficient of the PAR was larger than the others,indicating that the PAR was the most important factor to the NEE.The partial correlation coefficient of Ta was negative during the winter and positive during the summer.The partial correlation coefficient of VPD was positive year-round and was higher under high VPD conditions.

Roedores y Marsupiales en Torno Al Límite Pleistoceno/Holoceno en Catamarca, Argentina: Extinciones y Evolución Ambiental

RODENTS AND MARSUPIALS AT THE PLEISTOCENE—HOLOCENE BOUNDARY IN CATAMARCA, ARGENTINA: EXTINCTIONS AND ENVIRONMENTAL EVOLUTION. A fossil small-mammal assemblage from the neighborhood Las Juntas, Catamarca, Argentina (28°06′36″S–65°53′54″W, 1562 m) was studied. A radiocarbon dating on a sample of long bones referred them to late Pleistocene (13.4–13.0 cal ky). The assemblage includes twelve species, dominated by the sigmodontine rodents Reithrodon auritus (Fischer) and Phyllotis sp., followed by Akodon spegazzinii Thomas and Andinomys edax Thomas. The presence of the caviomorph Abrocoma cinerea Thomas, and the sigmodontines Akodon simulator Thoma s and Tafimys powelli Ortiz, Pardiñas and Steppan is remarkable. A Didelphimorphia, Thylamys sp., is also present. The surface of the bones and teeth shows microscopical evidences of corrosion, indicating that the sample was generated by the predatory activity of owls. The identified species correspond to elements of high-altitude open environments, a mixture of cloud highland-grasslands, high-Andean grasslands, and scarce elements of upper montane forest. Most of them are currently sympatric at an altitude of approximately 2500 m in the same mountain range, in a colder and drier environment than that recorded at the studied site. It is suggested that paleoenvironmental conditions during deposition of the assemblage were colder and drier. It is not possible to extrapolate these data to other areas because of the great orographic and environmental variation in the region, which determines different small-mammal assemblages across relatively reduced geographic areas.

Sustainable, low‐input, warm‐season, grass–legume grassland mixtures: mission (nearly) impossible?

AbstractGrazing lands in warm‐temperate and subtropical North America have become less diverse. Pastures are typically grass monocultures, while rangelands are generally managed for the grass components. Overstocking, selective herbicides, fire exclusion and heavy rates of nitrogen fertilizer have contributed to near exclusion of native, warm‐season legumes. The simplicity of managing grass monocultures, pasture production responses to nitrogen fertilizer and profitability of grass‐only systems have limited interest in legume‐based approaches. Changing economics and ecological concerns with ecosystem accumulation of industrial inputs contribute to an increasing interest in legumes. Unlike the development of temperate pasture legumes and recent research in the tropics, legumes tolerant of both freezing temperatures and hot weather have received less attention. Poor establishment, limited persistence and potential invasiveness limit currently available introduced species. Native, herbaceous, warm‐season legume species occur throughout warm‐temperate North America, but little attention has been directed to these plants as potential forage species. Some success with a few native legume species, primarily in the genus Desmanthus, suggests potential for expanded assessment of forage value of the many species available. Current assessments of native legumes, primarily for conservation purposes, provide an opportunity to expand evaluations of these species for pasture and rangeland potential while economics of livestock production and public interest in ecosystem health are supportive. Experiences with legumes of warm‐temperate origin in North America, along with results with temperate and tropical pasture legumes globally, provide a starting point for future efforts at incorporating greater legume diversity in pastures and rangelands of subtropical and warm‐temperate regions around the world.

Aesthetic preference for a Swiss alpine landscape: The impact of different agricultural land-use with different biodiversity

To counter the loss of agro-biodiversity, Swiss farmers can qualify for area-related direct payments by managing part of their utilized land (at least 7%) as so-called ecological compensation areas (ECAs). However, little is know how changing farming practices influence the scenic beauty of a landscape in view of the public. Such knowledge is especially valuable in regions that are significant tourist destinations and places of recreation. This paper investigates, with the help of 16 simulated colour images of a typical landscape in the Eastern Central Alps, the impact of different agricultural land-use (grassland, arable land), grassland management intensity (high, low, mixed), and abundance of ECAs on perceived scenic beauty by 202 non-alpine Swiss residents. Respondents rated each landscape by attractiveness, and characterized their most liked and disliked landscape. Landscapes covered with low-intensively managed, species-rich grassland and further ECAs such as single locally adapted tree species and hedges were rated highest, most often selected as best liked, and characterized as diverse, species-rich and worthy of preservation. Mere production landscapes with a mixture of high-intensity, species-poor grassland and arable land, and few ECAs were rated lowest, most often selected as disliked, and characterized as boring, although productive. The presence of arable land, once a typical element in Swiss alpine landscapes, generally reduced scenic beauty, although older people and environmental organisation members responded more positive to its presence. The results indicate that agro-environment schemes can positively influence the aesthetic quality of a region which, in consequence, might have a positive impact on tourism.

Aboveground overyielding in grassland mixtures is associated with reduced biomass partitioning to belowground organs

We investigated effects of plant species richness in experimental grassland plots on annual above- and belowground biomass production estimated from repeated harvests and ingrowth cores, respectively. Aboveground and total biomass production increased with increasing plant species richness while belowground production remained constant. Root to shoot biomass production ratios (R/S) in mixtures were lower than expected from monoculture performance of the species present in the mixtures, showing that interactions among species led to reduced biomass partitioning to belowground organs. This change in partitioning to belowground organs was not confined to mixtures with legumes, but also measured in mixtures without legumes, and correlated with aboveground overyielding in mixtures. It is suggested that species-rich communities invest less in belowground biomass than do monocultures to extract soil resources, thus leading to increased investment into aboveground organs and overyielding.

Effects of Tropical Deforestation on Global Hydroclimate: A Multimodel Ensemble Analysis

Abstract Two multimodel ensembles (MME) were produced with the GISS Model II (GM II), the GISS Atmosphere Model (AM), and the NCAR Community Climate System Model (CCSM) to evaluate the effects of tropical deforestation on the global hydroclimate. Each MME used the same 48-yr period but the two were differentiated by their land-cover types. In the “control” case, current vegetation was used, and in the “deforested” case, all tropical rain forests were converted to a mixture of shrubs and grassland. Globally, the control simulations produced with the three GCMs compared well to observations, both in the time mean and in the temporal variability, although various biases exist in the different tropical rain forests. The local precipitation response to deforestation is very strong. The remote effect in the tropics (away from the deforested tropical areas) is strong as well, but the effects at midlatitudes are weaker. In the MME, the impacts tend to be attenuated relative to the individual models. The significance of the geopotential and precipitation responses was evaluated with a bootstrap method, and results varied during the year. Tropical deforestation also produced anomalous fluxes in potential energy that were a direct response to the deforestation. These different analyses confirmed the existence of a teleconnection mechanism due to deforestation.