Field-Based Analysis of Runoff Generation Processes in Humid Lowlands of the Taihu Basin, China

In the flat lowland agricultural areas of subtropical climate zones, the runoff process has a great influence on the regional water quantity and quality. In this study, field data about rainfall, evapotranspiration, soil moisture, groundwater table, and surface water dynamics were collected in two different experimental sites in the Taihu Basin, China. Results showed that densely distributed ditches contributed to shallow groundwater depths and persistent near-saturation soil. A correlation analysis was conducted to improve the understandings of runoff generation in humid lowland areas of the Taihu Basin. It was found that a Dunne overland flow was the dominant mechanism responsible for the rapid runoff generation. The total rainfall and runoff expressed a good linear relationship with an R2 of 0.95 in the Hongqiwei test site. The initial groundwater depth was considered as the indicator of the antecedent soil moisture estimation for the close relationship. The depression storage was suggested in a range from 4.72 to 8.03 mm for an estimation based on the water balance analysis for each rainfall event, which proves that the depression storage should not be neglected when calculating the runoff generation process in humid lowlands.

Native Species Valuable timber plantations in Northern Guatemalan Humid Lowlands: ecological features and silvicultural feasibility

The North Humid Guatemalan Lowlands contains a significant diversity of tree species, incluiding some valuable-timber producers; these species are threatened by commercial overexploitation and habitat loss due to deforestation. The cultivation of these species in forest and agroforest plantations is a potentially viable optiontheir conservation and commercial harvesting, something that has been promoted with Government Incetemala during the past two decades. However, these species have not been widely planted, among othebecause knowledge on their ecological requirements and silviculture is scarce. A characterization of momixed plantations with 14 native valuable-timber species was made in the Humid Lowlands of Northeranalyzing for each species frequency of association and accompanying species, planted area, the main etures and growth rates. To gather information, we combined field observation and measurements with iliterature review. Based on our survey, main management challenges for cultivation of the species were described. Valuable-timber native trees could potentially be sustainably cultivated in the study zone in diffforest plantations and agroforestry schemes of coffee, cacao, cardamom and cattle; considering their suitdiversified systems, growth performance and farmer’s preferences, Swietenia macrophylla, Cedrela odordonnell-smithii, Calophyllum brasiliense and Cordia alliodora were the species with the higher potentiain plantations. However, several unsolved problems continue restricting the cultivation of these species itherefore, is essential a careful design and management.

Invasão biológica por Cryptostegia madagascariensis: uma abordagem voltada para estresses abióticos

<p style="text-align: justify;">A introdução, acidental ou deliberada, de espécies exóticas por diferentes vetores é atualmente uma das principais mudanças globais, resultando em uma série de problemas. Embora nem todas as introduções de espécies não nativas possuam efeitos negativos, muitos desses táxons podem desencadear efeitos indesejáveis sobre a biodiversidade, desde o nível genético até o nível de paisagens. Este trabalho visou apresentar o conhecimento atual sobre as invasões biológicas por espécies vegetais, particularmente, sobre a invasora <em>Cryptostegia madagascariensis</em> Bojer ex Decne. Novas introduções são feitas anualmente em todo o mundo e apenas uma pequena parte desses táxons se tornam invasores, mesmo assim, causam sérios danos aos ecossistemas invadidos. O sucesso das plantas infestantes deve-se às características intrínsecas dessas espécies, que garantem as mesmas vantagens competitivas com as espécies nativas e ao nível de perturbação dos novos nichos, que torna os ambientes totalmente favoráveis ao estabelecimento de novas espécies e ao surgimento de áreas monodominadas. Nesse contexto, encontra-se <em>C. madagascariensis</em>, trepadeira de origem da ilha de Madagascar, na África, que foi introduzida no Brasil com fins ornamentais, tornando-se invasora de ecossistemas naturais, principalmente em ambientes de mata ciliar e baixadas úmidas, no domínio da Caatinga e ecossitemas associados.</p><p style="text-align: justify;"><strong>Palavras chave</strong>: Espécies exóticas, Caatinga, salinização, déficit hídrico.</p><p style="text-align: justify;"><strong>Abstract</strong>: The introduction, accidental or deliberate, of exotic species by different vectors is currently a major global changes, resulting in a number of local and global problems. Although not all introductions of non-native species have negative effects, many of the non-native species can have undesirable effects on biodiversity from the genetic level to the landscape. This work aimed to present the current knowledge on biological invasions by species and particularly on invasive <em>Cryptostegia madagascariensis</em> Bojer ex Decne. New introductions are made every year around the world and only a small part of these taxa become invasive, yet cause serious damage to ecosystems invaded. The success of weed plants is due to the intrinsic characteristics of these species that ensures the same competitive advantages with native species and the level of disruption in new niches which makes them totally supportive environments to establish new species and the emergence of monodominadas areas. In this context is <em>C. madagascariensis</em>, origin of climbing on the island of Madagascar in Africa, which was introduced in Brazil with ornamental purposes, becoming invasive in natural ecosystems, especially in riparian environments and humid lowlands, in the field of savanna and associated ecosystems.</p><p style="text-align: justify;"><strong>Key words</strong>: Exotic species, Caatinga, salination, deficit hydride.</p>

SWIDDEN AGRICULTURE IN THETIERRA FRÍA? EVIDENCE FROM SEDIMENTARY RECORDS IN TLAXCALA

Swidden agriculture in Mesoamerica is commonly associated with the hot and humid lowlands and with small isolated communities. Charcoal-rich sediments discovered in Tlaxcala, however, suggest that it was practiced in the cold highlands in the Formative and Classic periods. The headwaters of the Xilomantla drainage incised a nine-meter deep channel shortly before 200b.c., in response to increased runoff from slopes degraded by agriculture. It was filled back within a few hundred years with sands and muds containing recurrent laminae of charred plant matter that reflect the annual burning of secondary scrub in fallowed fields. A gully in the La Ladera drainage received high inputs of charcoal from the surroundings of a nearby settlement between ca.a.d.400 and 900. The farming practices inferred from these deposits have no exact ethnographic analog. They inflicted lasting environmental damage, but were upheld for several centuries despite changes in settlement patterns.

Distribution, host range, and climatic constraints on Centistes gasseni (Hymenoptera: Braconidae), a South American parasitoid of cucumber beetles, Diabrotica spp. (Coleoptera: Chrysomelidae)

The genus Diabrotica includes a large number of pest species, including some of the most important crop pests of the Americas. The parasitoid Centistes gasseni Shaw is the first braconid to be described parasitizing Diabrotica in South America, and high natural infestations are reported. Field and experimental observations on the host range, distribution and biology of this parasitoid are described. Centistes gasseni was collected in southern Brazil, eastern Paraguay and northeastern Argentina, in a region comprising humid lowlands and highlands, and cool temperate to warm subtropical climates, with regular rainfall in excess of 1300 mm. Three Diabrotica species, D. limitata (Sahlberg), D. speciosa (Germar) and D. viridula (Fabricius) were found to host the parasitoid, with mean percent parasitism of 5.4, 2.0 and 1.0%, respectively. Diabrotica speciosa and D. viridula are the two most important pest Diabrotica species in South America. Laboratory experiments with field-collected beetles and parasitoid cocoons indicated that C. gasseni overwinters in adult host beetles, remaining dormant in its live host below developmental temperatures. A potential distribution of C. gasseni in North America is proposed based on its known climatic range and the distribution of the main pest species of adult overwintering North American Diabrotica.