Carlos Alberto Vettorazzi

The distribution and abundance of small mammals in agroecosystems of southeastern Brazil

Abstract The conservation of biodiversity in agricultural landscapes depends on information about the ways in which species are affected by the conversion of native habitats into novel anthropogenic environments and the strategies that the species use to persist in these altered ecosystems. Here, we investigate how small mammals occupy the different agroecosystems of an agricultural landscape in the state of São Paulo, Brazil. From August 2003 through January 2005, we surveyed small mammals using Sherman traps at 16 sampling sites in each of the four predominant environments of the local agricultural landscape: remnant fragments of semideciduous forest, Eucalyptus plantations, sugarcane plantations, and pastures. With a total effort of 23,040 trap-nights and a capture success of 0.8%, we captured 177 rodents and marsupials belonging to eight species. The assemblage represented by these mammals is essentially composed of generalist species, which are common in degraded areas. Sugarcane plantations had the highest abundance, whereas pastures had the lowest species richness. Our results suggest that the loss of forest species can be related to the loss of native forest. The results also indicate that to improve the conservation value of agricultural landscapes, native forest fragments should be conserved, extensive monocultures should be avoided and agricultural impacts should be mitigated.

Simulação da produção de sedimentos para a microbacia hidrográfica do Ribeirão dos Marins (SP)

The SWAT (Soil and Water Assessment Tool) model was applied to simulate the sediment yield in the watershed Ribeirao dos Marins, in Piracicaba, Brazil, for the biennial period of 1999/2000. The application of this model requires georeferenced input data, provided by an interface between the model and a Geographic Information System (GIS). The watershed was divided into sub-basins, and parameters were separately determined for each area. The simulated sediment yields were compared to the observed data of a gauge station located in the upper third of the watershed, using the Nash and Sutcliffe Coefficient (COE) and the deviation between simulated and measured data (Dv). After calibration the simulation results of the sediment yield showed a COE of 0,83 and a Dv of -3,2%, indicating that the simulated and observed data tally basically.

DISTRIBUTION OF CAPYBARAS IN AN AGROECOSYSTEM, SOUTHEASTERN BRAZIL, BASED ON ECOLOGICAL NICHE MODELING

Abstract Southeastern Brazil has seen dramatic landscape modifications in recent decades, due to expansion of agriculture and urban areas; these changes have influenced the distribution and abundance of vertebrates. We developed predictive models of ecological and spatial distributions of capybaras (Hydrochoerus hydrochaeris) using ecological niche modeling. Most occurrences of capybaras were in flat areas with water bodies surrounded by sugarcane and pasture. More than 75% of the Piracicaba River basin was estimated as potentially habitable by capybara. The models had low omission error (2.3–3.4%), but higher commission error (91.0–98.5%); these “model failures” seem to be more related to local habitat characteristics than to spatial ones. The potential distribution of capybaras in the basin is associated with anthropogenic habitats, particularly with intensive land use for agriculture.

Monitoring leaf area index at watershed level through NDVI from Landsat-7/ETM+ data

O Indice de Area Foliar (IAF) e um importante parâmetro do dossel da vegetacao, sendo utilizado, por exemplo, para estimar a evapotranspiracao, um importante componente do ciclo hidrologico. Analisou-se a relacao entre o IAF, medido em campo, e o indice de vegetacao NDVI, de quatro datas (a partir de dados Landsat-7/ETM+) e, com este indice, foram gerados e analisados mapas de IAF da area de estudo para as diferentes datas. O IAF foi coletado mensalmente em campo, com o equipamento LAI-2000, em areas de cana-de-acucar, pastagem, milho, eucalipto e floresta riparia. A relacao entre o IAF e o NDVI foi melhor ajustada por um modelo potencial, sendo que de 57% a 72% da variacao do NDVI puderam ser explicados pelo IAF. Os mapas de IAF gerados por modelos empiricos da relacao entre o IAF e NDVI mostraram razoavel precisao (o erro padrao da estimativa de IAF variou de 0,42 a 0,87 m2 m-2). O valor medio de IAF para cada mapa mensal mostrou-se relacionado com a precipitacao total dos tres meses anteriores.

Large Woody Debris Input and Its Influence on Channel Structure in Agricultural Lands of Southeast Brazil

Riparian forests are important for the structure and functioning of stream ecosystems, providing structural components such as large woody debris (LWD). Changes in these forests will cause modifications in the LWD input to streams, affecting their structure. In order to assess the influence of riparian forests changes in LWD supply, 15 catchments (third and fourth order) with riparian forests at different conservation levels were selected for sampling. In each catchment we quantified the abundance, volume and diameter of LWD in stream channels; the number, area and volume of pools formed by LWD and basal area and tree diameter of riparian forest. We found that riparian forests were at a secondary successional stage with predominantly young trees (diameter at breast height <10xa0cm) in all studied streams. Results showed that basal area and diameter of riparian forest differed between the stream groups (forested and non-forested), but tree density did not differ between groups. Differences were also observed in LWD abundance, volume, frequency of LWD pools with subunits and area and volume of LWD pools. LWD diameter, LWD that form pools diameter and frequency of LWD pools without subunits did not differ between stream groups. Regression analyses showed that LWD abundance and volume, and frequency of LWD pools (with and without subunits) were positively related with the proportion of riparian forest. LWD diameter was not correlated to riparian tree diameter. The frequency of LWD pools was correlated to the abundance and volume of LWD, but characteristics of these pools (area and volume) were not correlated to the diameter of LWD that formed the pools. These results show that alterations in riparian forest cause modifications in the LWD abundance and volume in the stream channel, affecting mainly the structural complexity of these ecosystems (reduction in the number and structural characteristics of LWD pools). Our results also demonstrate that riparian forest conservation actions must consider not only its extension, but also successional stage to guarantee the quantity and quality of LWD necessary to enable the structuring of stream channels.

Leaf area index of ground covers in a subtropical watershed

Leaf Area Index (LAI), an important structural variable descriptive of vegetation, is directly related to evapotranspiration and productivity. The objective of this work was to measure and analyze monthly LAI of different ground covers in a subtropical watershed. A field campaign to collect monthly LAI data was carried out during the year 2001, with a LAI-2000 (plant canopy analyzer) device, in sugarcane, pasture, corn, eucalypt, and riparian forest patches. Riparian forest presented a maximum LAI of 4.90; LAI values decreased as precipitation decreased, as it is a characteristic of this type of semideciduous vegetation. LAI for sugar cane presented the greatest variability throughout the year, related to plant characteristics and crop management in the study area. Results represent an initial step for the understanding of LAI dynamics in the study area and areas under similar conditions.

Temporal scale and spatial resolution effects on Amazon forest fragmentation assessment in Rondônia

The Amazon has been under an intense deforestation process for the last 30 years, causing landscape fragmentation in many different regions and at distinct stages. The fragmentation process is commonly assessed by land‐use maps derived from satellite sensor data and analysed at a landscape context. The analysis of fragmentation depends on an adequate choice of spatial resolution of land‐use maps, and temporal scale in landscape dynamics studies. In this study, spatial–temporal resolution variation effects on fragmentation assessment were analysed in the Quatro Cachoeiras watershed, located at central Rondônia, Brazilian Amazon. Land‐use maps derived from 1984 to 2002 satellite sensor data at 2‐year intervals were used for landscape structure analysis on 12 samples randomly distributed along the watershed. In the spatial resolution variation analysis, landscape metrics obtained at 30 m resolution were compared with those obtained at coarser spatial resolutions. Effects of temporal scale variation were tested by comparison of landscape metrics calculated at 2‐, 4‐ and 6‐year intervals in the studied period. Results show that fragmentation stage influences sensitivity of landscape metrics for spatial resolution and at initial stages of fragmentation finer spatial resolution is required. Also, coarser resolutions up to 100 m could be used to assess landscape fragmentation at regions and the adequate time interval for landscape dynamics studies should be between 3 and 4 years.

Simulação de cenários alternativos de uso da terra em uma microbacia utilizando técnicas de modelagem e geoprocessamento

The model SWAT (Soil and Water Assessment Tool) was used to simulate alternative scenarios of land use in Ribeirao dos Marins watershed, in Piracicaba, State of Sao Paulo, Brazil, for the biennial period 1999/2000. Two scenarios were simulated. The first one (scenario 1) was based on the current land use except for the introduction of a continuous riparian buffer of 30 m along the drainage network and of 50 m around the springs, in accordance to Brazils environmental legislation. In the second (scenario 2) the steepest slopes (30.9 % of the watershed area) with high erosive potential, covered by pasture, were substituted by native forest. The two simulated scenarios were compared to the current one in relation to sediment yield. The scenarios brought forth different spatial patterns of sediment yield. A reduction of 94,0 % in sediment yield was obtained by the substitution of pasture with native vegetation (scenario 2), and of 10.8 % in scenario 1. These results showed that it is necessary to manage landscape aspects of watersheds comprehensively, identifying the environmentally most sensitive areas, mainly in relation to erosion, instead of protecting only the riparian areas.

Relative reduction in annual soil loss in micro watersheds due to the relief and forest cover

With the intense debate, in Brazil, between landowners and public agencies about the amount of area with forest cover needed in different regions, there is an increase of the need for provision of technical data used as a basis for decision making. One of the criteria to evaluate the effect of forest cover in protecting water resources is the soil loss, which leads to several consequences on the environment, including the silting of the rivers. Therefore, this study aimed to evaluate the reduction in the soil loss in micro watersheds with different reliefs, size and location of forest cover, in the Corumbatai River watershed, in the state of Sao Paulo, using the Revised Universal Soil Loss Equation (RUSLE) in a GIS environment. For this study, 18 watersheds in three degrees of slope were selected, and 20 scenarios for land-use were established, by analyzing the influence of the PPA size, and the size and the location of the Legal Reserve. The results showed that: a) the effect of forest cover in reducing annual soil loss varies depending on the average slope of the watershed; b) the PPA width must be determined taking into account the slope of the watershed; c) the Legal Reserve must be located along the PPA. These provide better results in reducing annual soil loss.

Influence of forest cover on in-stream large wood in an agricultural landscape of southeastern Brazil: a multi-scale analysis

Large wood (LW) is critical to the structure and function of streams and forests are the main LW source to stream channels. To assess the influence of forest cover changes at different spatial scales on in-stream LW quantity, we selected eighteen catchments (2nd–4th order) in Southeastern Brazil with forests at different levels of alterations. In each catchment we quantified the pattern of forest cover (% cover and relative catchment position), the physical characteristics of catchments (elevation and slope), the characteristics of channels (wetted channel width and depth), the abundance and volume of in-stream LW, and the frequency of LW pools. We used simple and multiple linear regression to assess the response of LW variables to landscape and stream reach variables. Most of the LW was relatively small; 72xa0% had a diameter <20xa0cm, and 66xa0% had a length <5xa0m. Although percent forest cover at reach scale had substantial support to explain LW variables, the best predictors of LW variables were forest cover at broader scales (LW abundance and LW pool frequency were best predicted by forest at intermediate distance at the catchment scale and LW volume was best predicted by forest cover at the drainage network scale), suggesting that downstream transport is an important process in addition to local processes in our study area. These findings have important management implications because although low forested reaches receive less LW from local forests (or no LW in the case of deforested stream reaches), they are receiving LW from upstream forested reaches. However, the material is generally small, unstable and likely to be easily flushed. This suggests that not only should riparian forest conservation encompass the full drainage network, but forests should also be allowed to regenerate to later successional stages to provide larger, higher quality LW for natural structuring of streams.