Soil Microbial Activity and Biomass in Semiarid Agroforestry Systems Integrating Forage Cactus and Tree Legumes

Vegetation cover affects soil organic matter and activity of soil microorganisms. We investigated the intercropping effect of forage cactus with tree legumes on soil microbial biomass and organic matter in the semi-arid tropic, state of Pernambuco, Brazil. We assessed the following cropping systems: (i) Gliricidia sepium intercropped with cactus cv. IPA-Sertânia; (ii) Leucaena leucocephala intercropped with cactus cv. IPA-Sertânia; and (iii) Cactus cv. IPA-Sertânia in monoculture. Samples were collected during the dry and rainy seasons in the 0- to 0.10- and 0.10- to 0.20-m soil layers at 0, 1.5, 3.0, and 4.5 m in a perpendicular gradient from tree legume rows. The following responses were determined: δ13C and δ15N, C and N, microbial activity and biomass, and metabolic, microbial, and mineralization quotient. δ13C and δ15N varied with the distance from the trees. In the dry season and beginning of the rainy season, the cropping systems showed similar values for C, N, microbial activity, carbon, and nitrogen in the microbial biomass. The presence of tree legumes at the end of the rainy season favored soil microbiota, which showed a reduced loss of C-CO2, with no indication of metabolic stress and greater microbial biomass and microbial quotient in relation to forage cactus in monoculture.

Seedling Emergence of the Tree Legume Clathrotropis brunnea Amshoff, Endemic from a Colombian Tropical Rainforest

Seedling emergence is the main propagation method of forest species. Thus, we aimed to evaluate emergence aspects of the tree legume Clathrotropis brunnea Amshoff (sapán or blackheart sapán), a Fabaceae of high economic value endemic to the Colombian rainforest. We characterized the biometry of legumes and seeds and assessed seedling emergence in three experiments: (1) effect of fruit color and substrate, (2) seed conservation in storage, and (3) presoaking and seed position. Our results showed that seeds of green-yellow fruits have greater length and weight and a water content of up to 53%. Seedling emergence did not differ between green-yellow and dark-brown fruits but did differ with substrate type; nearly 80% of seedlings emerged in the sand substrate (S1), but only 62% emerged in the mixed substrate (S3). Fresh sapán seeds are nondormant, showing a recalcitrant behavior in which seedling emergence decreased after storage in all tested conditions. Both seed-sowing positions allowed an emergence of >80% with a small benefit of the hilum downward, regardless of presoaking treatments. However, these differences did not affect seedling height or biomass after emergence. Our results provide basic knowledge on production of tropical seedlings, seeking species conservation, and use in restoration projects. Study Implications Our study provides information on seedling emergence of a legume tree endemic to the Colombian rainforest, Clathrotropis brunnea Amshoff. Because the species has a high economic value, it has been overexploited in the Middle Magdalena Valley. We have found that C. brunnea seeds are not dormant, and thus fresh seeds could easily germinate and form seedlings in the nursery, but such seeds are sensitive to desiccation during storage (recalcitrant). Therefore, other factors such as deforestation and climatic changes may threaten its regeneration from seeds and propagation techniques are urgently needed for its conservation.

Data on the effects of fertilization on growth rates, biomass allocation, carbohydrates and nutrients of nitrogen-fixing and non-nitrogen-fixing tree legumes during tropical forest restoration

Objectives Tree legume species play an important role in forest restoration in the tropics. Understanding how different species adjust carbohydrate allocation and growth under distinct nutrient availability will enhance the success of restoring degraded areas. Data description A 2-year tropical forest plantation of the Forest Restoration Program of the Balbina Hydropower Dam was evaluated. Three non-N-fixing (Cenostigma tocantinum, Dipteryx odorata and Senna reticulata) and three N-fixing (Clitoria fairchildiana, Inga edulis and Acacia spp.) tree legume species were either fertilized or not fertilized. Growth rates and biomass allocation were calculated, and carbon (C) fractions and nitrogen (N), phosphorus (P) and nonstructural carbohydrate (NSC) concentrations were determined. Multiple nutrient additions increased the growth rates and aboveground biomass production of fertilized plants. According to the results presented, different species and N- fixers respond differently to fertilization regimes. The authors encourage the use of the presented data in meta-analysis studies that consider the fertilization or nutrient deficiency effects on growth, carbohydrate and nutrient responses. N-fixing species with high biomass growth and foliar N are important for restoring N and C cycles in nutrient-limited soils. Fertilization treatments are fundamental during the early stages of forest plantation development.

Calliandra houstoniana var. calothyrsus (calliandra).

C. houstoniana var. calothyrsus is a nitrogen-fixing tree legume which has recently become popular for use in small-scale tropical agroforestry due largely to its provision of fuelwood and animal fodder, and its tolerance of acidic soils. Genetic variation within the species has been the subject of widespread international evaluation and has revealed variation in productivity amongst provenances. A problem with poor seed production has been reported in a number of countries where C. houstoniana var. calothyrsus is planted.

Nutrient and anti-nutritional constituents of Penisetum purpureum and four indigenous tree legume of South-Western Nigeria: A potential ruminant feed

A study was carried out to investigate the nutrient composition as well as anti-nutritional constituents of some tree plants (Ficus sur, Bridelia macarrantii, Gmelina arborea and Albizia saman) and forage grass (Penisetum purpureum) in south- western Nigeria. Results indicated significant (P<0.05) variability in values of percentage crude protein (9.71 - 23.67%) where Penisetum purpureum recorded the least value and highest value observed in Ficus sur. Dry matter (DM), Crude fiber (CF), Organic matter (OM) and Ash contents varied significantly (p<0.05) from (23.52-46.23%, 8.45 - 30.22%, 64.01 - 96.95% and 2.66 – 8.44%) respectively. Albizia saman recorded significantly (p<0.05) higher ADF value (35.39%) with intermediate value (4.14%) of NDF. Penisetum purpureum had most ADL value (17.19%) while the least value was recorded in Gmelina arborea. Hemicellulose value ranged between (4.45 - 22.23%) with least value recorded by Ficus sur and highest by Penisetum purpureum plants. The concentrations of anti-nutritional factor was generally low, tannin content significantly (p<0.05) ranged from (0.75 - 3.56%) in Ficus sur and Albizia saman respectively. Penisetum purpureum had the least phytate (0.94 %) while Bridelia macarrantii recorded the most phytate value (2.65%). Saponin, Alkaloid and Oxalate level ranged from (0.10 - 1.51%, 0.36 - 1.58% and 0.34- 1.41%) respectively. The results show that the investigated plants seem to have good nutrient composition as well as low level of anti-nutritional factors and therefore can best be incorporated into ruminant feeding systems.

PHYSICAL-HYDRICAL ATTRIBUTES AND CO2 EFFLUX FROM THE SOIL AS INDICATORS OF ENVIRONMENTAL SUSTAINABILITY IN PASTORAL SYSTEMS IN THE BRAZILIAN SEMI-ARID

Soil degradation imposes significant environmental and economic impacts on the pastures of drylands worldwide, making livestock grazing systems often unsustainable under the present climate conditions. In this study, we aimed to compare the attributes of the soil of different grazing areas (pastures) using sensitive indicators of changes in the management of these areas, such as the physical-hydric properties and the CO efflux (ECO) from the soil. The study was carried out in three areas of exclosure grazing, understood by three land uses: a pasture of sabi grass (LU1), a silvopastoral system with sabi grass and tree legume (LU2), and an area with sabi grass and a herbaceous native legume (LU3). The measurements were undertaken over nine months and then grouped into three seasons (dry, transition, and rainy). The ECO and the ten indicators of soil physical-hydric quality were measured: macroporosity, aeration capacity, plant-available water capacity (PAWC), relative field capacity (RFC), characteristic pore radius, quantity of hydraulically active pores, sorptivity, saturated hydraulic conductivity, soil density, and soil resistance to penetration. The soils in the LU1 and LU3 areas showed limited plant available water capacity (0.10 PAWC < 0.15 cm cm) and was soil water-limited (RFC < 0.6). The advantages of using silvopastoral systems in semi-arid environments for environmental sustainability are not limited to improvements in the properties of soils, as these areas are also important carbon sinks.

Drying and storage of Melanoxylon brauna Schott. seeds

The objective of this work was to evaluate the sensitivity of Melanoxylon brauna Schott. tree legume seeds to desiccation and storage. In the drying experiment, the Melanoxylon brauna seeds were submitted to two drying conditions: a forced air circulation chamber (40.18 °C ± 0.13 and 28.48% ± 3.95 RH) and a silica gel desiccator (27.19 °C ± 1.28 and 26.19% ± 0.94 RH) for different times (0, 12, 24, 36, 72, and 144 hours). A completely randomized design in a 2 (drying methods) × 5 (drying times) factorial scheme plus control and 4 replications of 25 seeds was used. The following variables were evaluated before and after drying: seed moisture content, percentage of germinated seeds, germination speed index, percentage of mortality, normal and abnormal seedlings. In the storage experiment the seeds were divided into two batches: pre-dried (at 5.0% humidity) and without drying (control at 8.9% humidity). The seeds were then stored in plastic bags in three environments: refrigerator at 5 °C, freezer at –20 °C and room temperature (29 °C). The seeds were removed every four months and submitted to the humidity and germination test for 24 months. Data from this storage experiment were analyzed considering a randomized block design in a 2 (drying levels: presence and absence) × 3 (storage environments: refrigerator, freezer or room temperature) factorial scheme + 2 controls (with and without drying at baseline) and 4 repetitions of 25 seeds. Drying reduced initial seed water content from 8.9% to 5.0%, without loss of viability. Drying in the chamber at 40 °C was faster and more efficient than in silica gel. The results enable classifying the seeds of this species as orthodox, i.e. tolerant to desiccation. The fridge and freezer were efficient for storing the Melanoxylon brauna seeds up to 24 months, independent of previous drying, while storing the seeds at room temperature with previous drying makes them last longer than without drying, as the seeds can last up to 16 months with drying, or 12 months without drying.

Notes on the extended distribution of Humboldtia bourdillonii (Fabales: Fabaceae), an Endangered tree legume in the Western Ghats, India

Humboldtia bourdillonii is an Endangered tree legume; considered endemic to its type locality in the Periyar Tiger Reserve in Idukki District of Kerala State. A new population of this highly threatened endemic species is located in the Vagamon Hills of Kottayam District which is about 70km away from its original locality. The newly located population is drastically affected by the severe floods and landslides that occurred in Kerala state during August 2018. Urgent conservation measures are needed to protect the population from further loss.