The effects of the farming system (conventional-organic-abandoned) and soil management (native cover crop vs tillage) on vascular plant species were analyzed in sloping olive groves (>20%) in 20 different locations in Andalusia, SE Spain. The soil management techniques included Organic Tillage (OT), Organic Cover Crops (OC), Conventional Tillage (CT), Conventional Non-Tillage (CNT), Abandoned Cover Crops (AC) and Abandoned Woody (AW). Data for the vascular plant species were recorded through three line transects of 30 m with a bar perpendicularly touching every 1 m of the measuring tape. Environmental variables were also recorded at plot level to assess their influence. Dependent variables, such as species abundance, richness and diversity indexes were studied using univariate analysis (one-way ANOVA, Kruskal–Wallis test) while multivariate statistics (ANOSIM, SIMPER, DCA) were used for analyzing the data matrices. We found that the different combinations of farming system and soil management affect biological diversity in terms of individual abundance, plant cover, species richness and diversity, species and family composition. Life forms and species distribution patterns are also affected. The main environmental variables affecting the plant taxa were those related with soil and climate characteristics, slope, olive age and intensive land uses at landscape level, including the percentage of artificial surfaces. The lowest levels of biodiversity (e.g., species richness) were found in the tilled olive groves (CT = 8.1 sp. ± 2.2, OT = 10.0 sp. ± 5.4). Surprisingly, the organic tilled groves (OT) were very poor in species compared to those with native plant cover (OC = 27.9 sp. ± 3.0). The latter, however, showed similar species richness to the abandoned olive groves (AC = 21.2 sp. ± 3.7, AW = 27.2 sp. ± 3.0). Possible solutions for increasingly uncompetitive sloping olive groves include conversion to organic with native plant cover or abandonment for rewilding.

Positive relationships between plant species diversity, soil microbial function and nutrient cycling have been well documented in natural systems, and these relationships have the potential to improve the production and sustainability of agroecosystems. Our objectives were to study the long-term effects of planted species composition and nitrogen (N) fertilization on soil microbial biomass C, extracellular enzyme activity, changes in total soil C, soil fertility and aboveground biomass yield in mixtures of native prairie species managed with and without N fertilizer for bioenergy production at four sites in Minnesota (MN), USA. Species were sown into mixture treatments and composition was not maintained (i.e., no weeding) throughout the duration of the study. Species mixture treatments at establishment included a switchgrass (Panicum virgatum L.) monoculture (SG), a four-species grass mixture (GM), an eight-species legume/grass mixture (LG) and a 24-species high diversity forb/legume/grass mixture (HD). Species diversity and aboveground productivity were similar for most mixture treatments at final sampling after 11 or 12 years of succession. Despite this homogenization of productivity and diversity throughout the study, the effects of planted species diversity and a decade of succession resulted in some differences in soil variables across species mixture treatments. On a peat soil in Roseau, MN, soil enzyme activities including β-glucosidase (BG), cellobiohydrolase (CBH) and phosphatase (PHOS) were highest in HD compared to GM treatments. On a sandy soil at Becker, MN, total soil C increased in all treatment combinations at the 0–15 and 15–30 cm depth intervals, with SG showing greater increases than HD at the 15–30 cm depth. Final soil pH also varied by species mixture at the Becker and Roseau sites, but differences in treatment comparisons varied by location. Nitrogen fertilization did not affect any response variable alone, but interacted with species mixture treatment to influence PHOS and total soil C at Becker. The inconsistent effects of species mixture and N fertilization on soil biological and chemical properties observed across sites highlight the importance of local soil and climate conditions on bioenergy and ecosystem service provisioning of perennial bioenergy cropping systems.

Aminopyralid is the most commonly used herbicide for the control of yellow starthistle and other invasive thistles in annual grasslands of California. Although the effects of aminopyralid on native plant communities over a 2-yr period have been evaluated in prairies dominated by perennial species in the northern central states, similar evaluations have not been conducted in grassland communities of California, which are generally composed of a high diversity of native and nonnative annual species. In this study we monitored the effects of 53 and 123 g ae aminopyralid ha−1 on individual species cover and species richness over three growing seasons in two locations on California annual grassland. Treated plots were compared to untreated plots in randomized complete-block designs. Results were largely consistent between the two trials. In the first season after treatment, both rates of aminopyralid reduced dicot cover significantly, particularly members of the Asteraceae and Fabaceae. Treated plots also showed reduced species richness. However, these differences were less pronounced in the second season after treatment, particularly at the low rate. By the third season after treatment in both sites, there were no longer any significant effects on cover or species richness at the low herbicide rate. On California annual grasslands, winter applications of low rates of aminopyralid have been shown to give excellent control of yellow starthistle, providing long-term benefits to grassland ecosystems. Results of the current study suggest that negative impacts of aminopyralid on the desirable native forb community are transitory.

The ability of arbuscular mycorrhizal fungi (AMF) to influence the performance of nonnative invasive plants in their introduced range has received increasing attention. The dependence of the invasive nonnative vine pale swallow-wort on AMF was studied in three greenhouse experiments. The aims of the present work were to (1) determine AMF colonization levels of field-collected pale swallow-wort plants and several co-occurring native and nonnative plant species, (2) evaluate the growth response of pale swallow-wort to different components of the soil microbial community from an infested site, and (3) determine the growth response of pale swallow-wort when grown with a nonlocal AMF species. AMF root colonization was greater in pale swallow-wort (85, 98, and 50% arbuscules, hyphae, and vesicles, respectively) than in leek (72, 80, and 25%), a species that has been frequently used as a predictor of AMF density in soil. Root colonization of pale swallow-wort in the field was also greater than root colonization of common milkweed, a native herbaceous species often co-occurring in the same habitats, as well as two other herbaceous species, Canada goldenrod and blueweed. Survival of pale swallow-wort plants was significantly greater in soil collected underneath dense monospecific stands of pale swallow-wort in a Henderson Harbor, NY, field site than in sterilized soil. After 12 wk, plants grown in sterilized soil had a 33% survival rate, whereas all plants grown in the unamended soil, with an intact microbial community, were alive. Moreover, plants grown in the unamended soil were 130% taller, had 50% more leaves, and had 83% greater total biomass compared with plants grown in sterile soil. Plants grown in soil containing a Glomus intraradices isolate collected in Troy, AL, were 50% shorter and had 15% lower total biomass than plants grown in the unamended New York field soil. These pale swallow-wort seedlings also had a high mycorrhizal dependency of 93%. Plants grown in a sterilized soil that was reamended with an AMF-free microbial wash had significantly lower belowground and total biomass than plants grown in the unamended soil with the resident AMF community. There was a trend of decreasing height and biomass for plants grown in sterile soil relative to the unamended controls treatment. Plants grown in sterilized soil had significantly (28%) greater total biomass than plants reamended with the AMF-free microbial wash. These findings suggest that AMF occurring in invaded habitats have beneficial effects on pale swallow-wort survival and growth.

Several weed species have been reported to have allelopathic activities. However, most of these studies indicate the probable involvement of allelochemicals but are not conducted in field settings. In addition to their adverse effects on growth and yield of many crop species, many troublesome weeds such as mugwort and lantana influence biodiversity. More studies on the ecological, physiological, and molecular aspects of weed allelopathy should be conducted in order to better understand community structure and declining biodiversity.

Reducing emissions from deforestation and forest degradation, the sustainable management of forests and the conservation and enhancement of forest carbon stocks in developing countries (‘REDD+’) aims to improve local livelihoods and conserve plant diversity while limiting carbon emissions. Yet trade-offs and synergies that exist between supporting livelihoods, protecting plant diversity and maintaining forest ecosystem services are poorly documented. We used forest inventory data and community-group records to assess trade-offs and synergies between carbon, plant diversity and forest products in 19 community forests managed under REDD+ in Nepal. Trade-offs were prevalent for carbon, whereby community forests with relatively high carbon values had relatively low values for plant diversity or forest products provision, and vice versa. Synergies occurred between plant diversity and forest products provision (fuelwood and fodder), suggesting that forests with relatively high plant diversity values were also important for providing critical forest products to local communities. This study shows that conserving forests for carbon should not impinge greatly on the flow of forest resources to at least some local communities; however, promoting carbon storage will not necessarily protect plant diversity. These findings should help guide future REDD+ policy for community forests.

This work synthesises information about plant diversity of 37 sites of coastal and inland swamp forests of southeast and southern Brazil and investigates floristic similarities and differences among them. Swamp forests often show low species richness, diversity and evenness, which are associated with the selective character of oxygen deprivation caused by soil waterlogging. However, our results pointed out some degree of site-level variation (Sobs = 5 to 110; Sjack1 = 6 to 151; H′ = 0.82 to 3.98; J′ = 0.51 to 0.87) related to local ecological conditions. Two major phytogeographical patterns emerged from our work: the strong influence of the neighbouring non-flooded vegetation on the flora of swamp forests and its high spatial heterogeneity. At least 85.9% of the 518 species sampled are found in neighbouring non-flooded vegetation. A correspondence analysis consistently separated swamp forests of the coastal plain from those of the plateau. A Mantel test indicated a significant correlation between floristic and geographical distances among sites (r = 0.45; p = 0.001), and highlighted the main effect of regional-scale changes in the flora of swamp forests. We conclude that swamp forests of southeast and southern Brazil cannot be considered a distinguishable floristic unit.

A megafossil plant assemblage containing three zosterophyll plants (Gen. nov. A, aff. Huia sp. and a unnamed spike) is described from the Lower Devonian Xitun Formation (Lochkovian) of Qujing, Yunnan Province, China, providing new data on the diversity of plant types during the Lochkovian, a time poorly represented by fossil vascular plants. Gen. nov. A has a character combination of naked axes, a diagnostic branching pattern (i.e. K-type branching as well as small lateral branches scattered along the axes) and lateral stalked sporangia. Aff. Huia sp. has ovate and stalked sporangia which are arranged in loose spirals and are reflexed adaxially. Combining the plants previously reported from the Xitun Formation (i.e. Xitunia spinitheca, Zosterophyllum shengfengense and Z. minorstachyum), the Xitun flora is dominated by zosterophylls and exhibits varied vegetative and fertile morphologies. Unlike the coeval plant assemblages in many localities of Laurussia and western Gondwana, which are mainly composed of plants with isotomous branching and terminal sporangia, the Lochkovian flora of South China is dominated by zosterophylls, documenting the existence of a distinct Northwest Gondwanan phytogeographic unit in the Lochkovian and a strong effect of phytogeographical isolation.

The Millennium Ecosystem Assessment estimates that between 60,000 and 100,000 plant species are threatened with extinction–equivalent to around one-quarter of the total number of known plant species. Why should we care? There are a number of reasons. The first is that these plants may be useful to us in unknown ways. Secondly, ecology has taught us that resilience is found in diversity. Thirdly, we should be saving plant species from extinction because we can–there is no technological reason why any plant species should become extinct. Where we can't protect and manage plant diversity in situ, we should be employing ex situ conservation techniques, ranging from seed banks to habitat restoration. The Millennium Ecosystem Assessment describes such interventions as ‘techno-gardening’. This is not an abstract concept–it is already a reality in the majority of man-managed landscapes. In this context the perception of ex situ conservation as simply a back-up strategy for in situ conservation is mistaken. We are all involved in ex situ conservation to some degree, from cultivating our back gardens, to farming, to management of protected areas. Ex situ conservation should be seen as a complementary approach to in situ conservation and on the same spectrum. Kew's Millennium Seed Bank Partnership, comprising more than 120 plant science institutions in 50 countries, epitomizes this philosophy in action. We work actively on every seed collection we bank, finding out how useful it is and how we can grow it to enable human innovation, adaptation and resilience. Challenges remain at the policy level; for example, the need to factor-in the value of natural capital to development decision making, and better defining a role for public-sector science. At the technical level, also, there is much to do. Perhaps the greatest technical challenges relate to the restoration and management of complex, self-sustaining habitats or species assemblages. If we are to techno-garden effectively, in order to maintain ecosystem services and sustain biodiversity, then a multidisciplinary approach will be required. Many plant science institutions have recognized this and are becoming engaged increasingly in restoration activities and in situ management. Ultimately, humanity's ability to innovate and adapt is dependent on our having access to the full range of plant species and the alleles they contain.

Tropical forest vegetation occurs within a narrow corridor along the semi-arid lower floodplain of the Tana River, Kenya. An inventory of the woody flora and ecological study of 12 forest areas in the Tana River National Primate Reserve (TRNPR) describe the composition and structure of this riverine forest ecosystem and identify patterns of regional and local diversity. Only 175 species in 49 families are recorded in the woody flora, but the geographic affinities of 98 species are from four major floristic regions in Africa: Zanzibar-Inhambane (31%), Somalia-Masai (16%), Guinea-Congolian (12%), and Zambezian (1%). Ten species are rare and/or disjunct. Forests have a disturbed physiognomy characterized by a low mean height (14.4 m), high species importance attributable to a few trees, low density (409 ha−1) and coverage (23.1 m2 ha−1) of trees > 10 cm dbh, and an abundance of palms and lianes. Changes along the river in sediment deposition and hydrology explain the high diversity of landforms and corresponding forest types in the TRNPR vicinity, but the absence of trees which are most important near Bura, Acacia elalior, and near Wema, Barringtonia racemosa, suggests that the regional diversity of the ecosystem is inadequately protected. Preservation of key resources, such as the endangered primates, should be coupled with protection of the forest heterogeneity that characterizes this dynamic landscape.

Field experiments and survival analysis were used to test whether the Janzen-Connell model operated for two common Amazonian tree species in Peru: the midstorey palm, Astrocaryum murumuru, and the canopy-emergent legume, Dipteryx micrantha. Seed and seedling survival patterns of these species partially supported the model, depending on tree species, type of predator, spatial scale and the particular year. At a small scale of a 2.5-ha plot, Astrocaryum seed predation by insects and mammals was density-dependent. At a larger scale of 100 ha, Dipteryx seed survival increased with distance from conspecific adults, but for Astrocaryum seeds there was no distance dependence. At the scale of 200–400 ha Dipteryx seed survival was negatively related to the number of individuals present in groups of conspecific adult trees. In 1992 a higher proportion of Astrocaryum seedlings survived far from, compared with close to, conspecific adult trees, whilst in 1993 more Dipteryx seedlings survived beneath conspecific adult trees than farther away.

Advances in genomics have provided technologies for high throughput analysis of plant genomes with potential for use in gene discovery in germplasm collections. The establishment of DNA banks facilitates this screening by making DNA from large numbers of plant accessions widely available. DNA banks require the development of appropriate policies for access and benefit sharing. Tools for automating sample and data handling are essential. Standard molecular methods for fingerprinting DNA accessions for international comparisons need to be determined. New screening technologies are required to take advantage of the emerging availability of large DNA collections. The Australian Plant DNA Bank aims to collect DNA from all Australian plant species and to sample the diversity within each species. DNA from all individuals of the species is being stored for rare species. Domesticated or economically important species from all countries are also being collected and stored. International networking of DNA banks will be a key step in linking genomics tools to global plant diversity.