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Slash‐and‐burn agriculture followed by tillage and western style agriculture often lead to loss of soil organic matter and soil degradation. Traditional slash‐and‐burn agriculture affects large areas of land across the tropical zone. However, there are few detailed studies about this practice. To evaluate the effect of traditional slash‐and‐burn agriculture on soil properties (total C, N, P, and C fractions of soil and available P, Ca, Mg, K, NO3, pH, and microbial community biomass and composition), we studied a chronosequence represented by active gardens, abandoned gardens (5–10 years old), secondary forest in abandoned garden sites (20–40 years old), and primary forest with no evidence of cultivation for at least 60 years. No significant differences between individual succession stages were found in total C, N, and P and in C fractions, pH, conductivity, and microbial biomass. In addition, stocks of C, N, and P in the soil did not differ between succession stages. By contrast, the concentration of available P, Ca, Mg, K, and NO3 was highest in active gardens. Litter was absent in active gardens, and the highest amount of litter on the soil surface was found in primary forest. Our results show that traditional slash‐and‐burn agriculture had a strong effect on nutrient availability but no effect on the total CNP stocks and soil C fractions. [ABSTRACT FROM AUTHOR]

Questions: Predicting which newly arrived species will establish and become invasive is a problem that has long vexed researchers. In a study of cold temperate oak forest stands, we examined two contrasting hypotheses regarding plant functional traits to explain the success of certain non-native species. Under the "join the locals" hypothesis, successful invaders are expected to share traits with resident species because they employ successful growth strategies under light-limited understorey conditions. Instead, under the "try harder" hypothesis, successful invaders are expected to have traits different from native species in order to take advantage of unused niche space. Location: Minnesota, USA. Methods: We examined these two theories using 109 native and 11 non-native plants in 68 oak forest stands. We focused on traits related to plant establishment and growth, including specific leaf area (SLA), leaf carbon-to-nitrogen ratio (C:N), wood density, plant maximum height, mycorrhizal type, seed mass and growth form. We compared traits of native and non-native species using ordinations in multidimensional trait space and compared community-weighted mean (CWM) trait values across sites. Results: We found few differences between trait spaces occupied by native and nonnative species. Non-native species occupied smaller areas of trait space than natives, yet were within that of the native species, indicating similar growth strategies. We observed a higher proportion of non-native species in sites with higher native woody species CWM SLA and lower CWM C:N. Higher woody CWM SLA was observed in sites with higher soil pH, while lower CWM C:N was found in sites with higher light levels. Conclusions: Non-native plants in this system have functional traits similar to natives and are therefore "joining the locals." However, non-native plants may possess traits toward the acquisitive end of the native plant trait range, as evidenced by higher nonnative plant abundance in high-resource environments. [ABSTRACT FROM AUTHOR]

Abstract: Short‐term experiments cannot characterize how long‐lived, invasive shrubs influence ecological properties that can be slow to change, including native diversity and soil fertility. Observational studies are thus necessary, but often suffer from methodological issues. To highlight ways of improving the design and interpretation of observational studies that assess the impacts of invasive plants, we compare two studies of nutrient cycling and earthworms along two separate gradients of invasive shrub abundance. By considering the divergent sampling strategies and statistical analyses of these two studies, and interpreting their contradictory results in the context of other studies, we also aim to better describe the impacts of the focal invader, Rhamnus cathartica. In a new study of a single site in Minnesota, we observed positive correlations between buckthorn abundance and soil pH, soil nutrient pools, nutrient fluxes through leaf litterfall, earthworm abundance and root biomass. Multiple regression models showed these relationships persisted after accounting for variability in soil texture and tree species composition. For a separate, more expansive study in Illinois, other authors reported little to no correlation between buckthorn abundance and 10 soil properties, including earthworm abundance, pH and nutrient concentrations. However, like many other studies, their regression models only assessed predictors related to invader abundance. R2‐values for models of ecosystem properties ranged from 0 to .79 (adjusted‐R2) for our study in Minnesota and from <.05 to .16 (unadjusted) for the prior study in Illinois. Differences in sampling error and use of predictor variables between the two studies likely explain the contrasting results. Synthesis and applications. To reduce the uncertainty of conclusions from observational studies of invasive plants, future studies must ensure that heterogeneity of soils and vegetation is adequately accounted for in the sampling strategy and statistical analyses (e.g. analysis of covariance, multiple regression). Particular attention should be given to ecosystem properties with variability that likely pre‐dates the invader (e.g. geophysical features and tree community composition). In our study, effects of buckthorn on ecosystem properties were not only robust to the inclusion of potentially confounding predictors, but also consistent with expectations based on ecological stoichiometry and mass balance of element flow. [ABSTRACT FROM AUTHOR]

* Nonrandom collecting practices may bias conclusions drawn from analyses of herbarium records. Recent efforts to fully digitize and mobilize regional floras online offer a timely opportunity to assess commonalities and differences in herbarium sampling biases. * We determined spatial, temporal, trait, phylogenetic, and collector biases in c. 5 million herbarium records, representing three of the most complete digitized floras of the world: Australia (AU), South Africa (SA), and New England, USA (NE). * We identified numerous shared and unique biases among these regions. Shared biases included specimens collected close to roads and herbaria; specimens collected more frequently during biological spring and summer; specimens of threatened species collected less frequently; and specimens of close relatives collected in similar numbers. Regional differences included overrepresentation of graminoids in SA and AU and of annuals in AU; and peak collection during the 1910s in NE, 1980s in SA, and 1990s in AU. Finally, in all regions, a disproportionately large percentage of specimens were collected by very few individuals. We hypothesize that these mega-collectors, with their associated preferences and idiosyncrasies, shaped patterns of collection bias via 'founder effects'. * Studies using herbarium collections should account for sampling biases, and future collecting efforts should avoid compounding these biases to the extent possible. [ABSTRACT FROM AUTHOR]

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Phylogenetic ecology has identified patterns of diversity in communities that may find explanation in trophic interactions, and yet there have been few attempts to directly relate such patterns among trophic levels. Density-dependent processes involving pests and pathogens, for example, have been invoked to account for plant community phylogenetic patterns, but relatively little is known about how plant relatedness might affect community structure at other trophic levels. We examined the degree to which the abundance of herbivores in a rain forest community is explained by the phylogeny and functional traits of host plants. We destructively sampled all stems ≥5 cm diameter in two 1-ha plots of New Guinea primary and secondary lowland forest to test predicted relationships between herbivore abundance and plant resources. We analyzed per-tree caterpillar and leaf miner abundance, total leaf biomass (kg), percentage of immature foliage, specific leaf area (cm2/g), leaf nitrogen content (percentage of dry mass), and presence of exudates in the context of a plant community phylogeny estimated from DNA barcodes. Apart from nitrogen content and exudates, neither plant resources nor herbivore abundance showed evidence of phylogenetic signal in our community sample. The plant traits we measured could account for only 30% and 16% of variation in caterpillar and leaf miner abundance, respectively, among individual trees. Leaf biomass was a stronger predictor of herbivore abundance than either resource quality (leaf nitrogen content) or palatability (percentage of immature foliage, specific leaf area). The primary importance of resource quantity was also observed at the plant species level in analyses of species means and phylogenetic generalized least-squares regression. Plant relatedness did not account for much variation in herbivore abundance, but significant effects of exudates and leaf nitrogen content on caterpillar abundance illustrate how conserved traits at one trophic level may influence community-wide patterns at another. [ABSTRACT FROM AUTHOR]

The cover image is based on the Research Article The effect of traditional slash‐and‐burn agriculture on soil organic matter, nutrient content, and microbiota in tropical ecosystems of Papua New Guinea, by Jaroslav Kukla et al., https://doi.org/10.1002/ldr.3203. [ABSTRACT FROM AUTHOR]