The effects of fire on vegetation in the upper encinal woodlands, Santa Catalina Mountains, southeastern Arizona, were studied following a wildfire in July 1995. Similar unburned and burned sites were compared to determine differences (alpha = .05) for frequency, density, and percent cover of herbs, shrubs, and trees through observations made during early June of 1997 and 1998 (two and three years postfire). For herbs, which showed their opportunistic characters, differences existed for frequency and percent cover each year and density in the third year. For shrubs, due to the ability of the dominant species, Arctostaphylos pungens (pointleaf manzanita), to rapidly reseed itself, no differences existed for frequency or density each year; but total mortality of mature A. pungens resulted in differences for percent cover each year. For trees, due to the ability of Quercus spp. to vigorously stump sprout, no differences existed for frequency, density, or percent cover each year.

Tree-ring records were used to reconstruct the spatial and temporal patterns of western spruce budworm (Choristoneura occidentalis Freeman) outbreaks in the Rio Grande National Forest (RGNF) of southern Colorado. Reconstructions at 11 host stands showed a synchronous pattern of outbreaks with a peak in the number of trees recording outbreaks over the entire RGNF on average every 24 years. These synchronous periods of outbreaks coincided with periods of increased moisture as indicated by an independently reconstructed summer Palmer Drought Severity Index, while relatively few trees recorded outbreaks during dry periods. The reconstruction on the RGNF does not support the hypothesis that human land use has significantly altered outbreak patterns. Tree response to outbreaks in the RGNF was different from prior studies as reductions in growth were typically detectable only when growth was compared to that of nonhost tree species.

No description available.

No description available.

Forestry is an important industry in Sweden, with clear-cut as the most commonly used method for harvesting. Here the long-term impact of clear-cut on lake water quality (dissolved organic carbon (DOC), nitrogen, phosphorus and pH) has been investigated, based on 23 lakes sampled during autumn. Data for additional 15 lakes sampled for the Swedish monitoring program were also used. Lakes were classified as 5, 25, 40 and 60 year based on data of the forest age in the catchment, gathered from the Swedish national forest inventory. Clear-cut lakes were classified as 5 years (>20% of the catchment clear-cut during the last 10 years). The results showed that DOC and total nitrogen (TN) concentrations decreased with increasing age of the forests. In clear-cut lakes (5 year) average DOC- (20.5 mg/L) and TN concentrations (477 µg/L) were higher than the average concentration in lakes with older forests (25, 40 and 60 year) (i.e. DOC 13.5 mg/L and TN 351 µg/L). Also the quality of DOC were changing (measured as changes in absorbance at 254) with forest age, with more bioavailable (low molecular weight) DOC in clear-cut lakes. A greater clear-cut area compared to the catchment area did not significantly result in higher concentrations of DOC and TN in clear-cut lakes. In conclusion, the concentration of TN, and the concentration and quality of DOC, in small boreal lakes are affected by clear-cutting and are changing with the age of the forest stand. Thus, highest concentrations and more bioavailable carbon compounds are found in clear-cut lakes where forests recently has been removed (<10 year).

The work reported here aimed to provide a comprehensive database of core information to support the development and validation of process-based models of resource capture and growth in semi-arid overstorey agroforestry systems. Intensive field studies were carried out in Kenya over a 30 month period and the results obtained were combined with data from a previous project to produce a dataset spanning a 4.5 year period. This dataset was then used to verify output from the HyPAR model. Allometric procedures developed from the pipe model theory (Lott et al., 1998) were used to estimate tree growth non-destructively throughout the observation period. Significant differences in tree size between the sole (Td) and dispersed agroforestry (CTd) treatments were established during the first 130 days after planting, probably because of competition with the associated crops. The above-ground biomass and trunk length and taper characteristics of the CTd trees remained inferior to those of Td trees throughout the observation period, seriously undermining the economic potential of this agroforestry system. The biomass and grain yield of CTd understorey crops were similar to the corresponding sole crops during the first three seasons, but were negligible in three of the final four seasons, with maize yields reaching 50 % of the equivalent sole crop values only when seasonal rainfall was well above average. This observation suggests that water availability was the primary limitation for CTd maize during the final seasons of the trial, a conclusion supported by the superior performance of maize grown under net enclosures which simulated tree shade in the absence of below-ground competition. Cowpea and maize were grown concurrently in two seasons to examine the impact of grevillea on C4 and C3 crops with contrasting responses to shade; biomass and grain yield were less affected in cowpea than in maize. The tree canopy in the dispersed agroforestry (CTd) treatment reduced the daily mean quantity of radiation incident upon the understorey crops by c.30 % during the final four growing seasons, although the discontinuous nature of the tree canopy caused substantial local variation in shading intensity. Seasonal mean fractional interception was greater for the combined canopies of the CTd treatment when soil moisture status was relatively high than for either of the sole canopies, suggesting the occurrence of spatial complementarity. Tree shade had a substantial moderating influence on meristem temperature since the mean diurnal temperature range was reduced from a maximum of 20°C in sole maize to 13 °C under the trees, and maximum meristem temperature was decreased by up to 6 °C relative to sole maize. However, the non-uniform shading provided by the trees caused substantial spatial variation in thermal time accumulation and hence crop development. Grevillea continued to grow during dry seasons and was therefore able to capture off-season rainfall which might otherwise have been lost from productive use. In addition, adaptation of heat balance gauges for use on grevillea roots (Lott et al., 1996) showed that substantial quantities of water could be extracted from deep-seated reserves below the crop rooting zone during dry periods, indicating the potential for spatial and temporal complementarity. However, transpiration by grevillea greatly exceeded rainfall during the dry season, rapidly depleting residual water supplies which might otherwise have been available for crop growth. In addition, approximately two thirds of the water used by the trees during cropping seasons was extracted from the soil surface horizons by lateral roots at distances of up to 2 m from the trunk. Thus, the potential for above and below-ground complementarity may be seriously undermined by the extensive capture of water by tree roots from the crop rooting zone. Comparison of output from the HyPAR model against the observed results provided information pertinent to future model development. The model proved to be insufficiently flexible for end-users wishing to simulate the growth of different crops during the same simulation cycle, or to use model output to aid management decisions such as the timing of pruning. The allometric procedures used by the model to estimate canopy size from trunk diameter at breast height also proved incapable of accounting for reductions in canopy size resulting from pruning. Estimates of tree height are rounded to the nearest metre within the model, representing a potentially serious loss of resolution when annual increments often do not exceed 2 m. In addition, the numerous parameters required by the model would force most end-users to rely heavily on published information, potentially undermining the reliability of simulations.

I assessed forest dynamics, stand structure and composition using repeated measurements of permanent plots over twelve years, in areas logged according to RIL guidelines and areas logged conventionally (CL) in Sabah, Malaysia. I compared successful pathways between treatments and used stand dynamics data to estimate carbon fluxes and pools over twelve years. Matrix models were used to generate projections of carbon emissions, sequestration and storage over a thirty-year logging cycle. Stem density (439 stems ha^-1 (95% CI = 358 – 477), basal area (32 m² ha^-1 (95% CI = 23-44) ) and carbon stored in above ground biomass (AGB, 1160 Mg C ha^-1 (95% CI = 97 – 232)) did not differ from prelogging levels twelve years after RIL. There was no recovery of these years variables after CL (246 stems ha^-1 (95% CI = 200 – 303), basal area 20 m² ha^-1 (95% CI = 13-28), carbon in AGB 101 Mg C ha^-1 (95% CI = 58 – 157)). Mortality, growth and recruitment rates remained elevated throughout the study. Both damaged and undamaged trees experiencing high mortality, especially after CL. Stalled, tree-less gaps and vine-covered building phase forest covered 54% of the CL area and appeared to have increased over time. Closed canopy and tree-dominated building phase forest dominated the RIL areas (81%). Total carbon storage over a thirty year logging cycle after RIL is projected to be 40% higher than after CL and result in reduced emissions of 88 Mg C ha^-1 and increased sequestration of 27 Mg C ha^-1. The total carbon benefit of using RIL instead of CL in lowland dipterocarp forest is projected to be 196 Mg C ha^-1 over a cutting cycle. My comparisons and projections of emissions, sequestration and storage in above-ground biomass show that the carbon benefit of reduced-impact logging exceeds previous projections. RIL areas are likely to provide substantial co-benefits in timber stocking, biodiversity conservation and resilience to climate change compared with CL areas.

Spatial competition indices for Scots pine and birch growing in heterogeneous Caledonian forest in Glen Affric were developed. Competition indices (CIs) have frequently been used in empirical models of individual tree growth. However, the contribution of CIs to the predictive ability of growth models is often very small. The poor performance of CIs may relate to the choice of spatial descriptors and functional form of the index. To improve CI performance a novel approach utilising neural networks and simulated annealing for the optimisation of CIs was developed.

Este trabalho trata dos aspectos geográficos e históricos dos eucaliptos, na Austrália e no Brasil, com atenção especial para a situação no Vale do Paraíba, estado de São Paulo. O trabalho possui três capítulos, nos quais são tratados temas pertinentes à questão dos eucaliptos no Brasil. Existem diferentes tipos de plantios de eucaliptos, em áreas urbanas e rurais, com finalidades comerciais e não-comerciais. Focou-se principalmente os extensos plantios em áreas rurais, com finalidade comercial. Os resultados das medições e informações coletadas demonstram que no Vale do Paraíba paulista ocorrem impactos ambientais positivos e negativos a partir do cultivo de eucaliptos, exigindo medidas para minimizar os impactos negativos e recuperar as áreas rurais da região. / This work deals of geographics and historic aspects of eucalyptus, in Australia and Brazil, with particular emphasis for the situation in the region of Vale do Paraíba, São Paulo state. The work have three chapters, where are treated the relevant themes related to the eucalyptus in Brazil. There are different types of eucalyptus plantations, in urban and rural areas, for commercial and not commercial purposes. Focused mainly the extensive plantations in rural areas, for commercial purposes. The results of the measures and informations collected show that in the Vale do Paraíba region, occurring positive and negative environmental impacts, from the cultivation of eucalyptus, requiring measures to minimize negative impacts and recover the rural areas of the Region.

Este trabalho teve como objetivo geral avaliar o uso da geoestatística aplicada ao inventário florestal. Especificamente avaliaram-se: a estrutura de continuidade espacial de quatro características dendrométricas, os métodos de ajuste e seleção de modelos da função de semivariância, o comportamento dos intervalos de confiança clássico e geoestatístico e o potencial da krigagem de bloco para a predição volumétrica por talhão. Os dados para realização do presente estudo foram obtidos num povoamento de 987 hectares de Eucalyptus grandis, com sete anos de idade, localizados no município de Itapetininga, São Paulo, pertencente à Votorantin Celulose e Papel (VCP). Pelos semivariogramas anisotrópico e isotrópico avaliou-se a estrutura de continuidade espacial das características: volume, diâmetro médio quadrático, área basal e altura média dominante. Dois modelos da função de semivariância foram ajustados para o volume, por meio de quatro métodos de ajuste e a seleção do melhor modelo foi efetuada a partir do critério de Akaike (AIC) e por meio das técnicas de validação cruzada e preditiva. Quanto às simulações estocásticas com o modelo geoestatístico, verificou-se o desempenho da cobertura do intervalo de confiança clássico e geoestatístico em relação à cobertura nominal. A predição volumétrica por talhão foi obtida da krigagem com simulação em cada um dos talhões do povoamento. Verificouse que as características dendrométricas mensuradas no inventário florestal apresentaram-se estruturadas espacialmente. Este resultado sugeriu que no processamento do inventário florestal deve-se considerar a componente espacial, ou seja, as parcelas não devem ser tratadas de forma independente. Sugere-se o uso conjugado do critério de Akaike e da validação cruzada para seleção de modelos da função de semivariância. Detectou-se que os intervalos de confiança clássico e geoestatístico apresentaram cobertura inferior à cobertura nominal, para uma população espacialmente contínua. Porém, a cobertura do intervalo de confiança do estimador clássico foi bem inferior à cobertura nominal, mostrando viés substancial na estimativa da variância da média quando há estrutura de continuidade espacial. Para populações fixas o estimador clássico proporcionou cobertura observada igual à cobertura nominal. Este resultado comprova a validade da aleatorização para uso do Teorema Central do Limite, na definição do intervalo de confiança, independente da estrutura de continuidade espacial. Na presença de continuidade espacial, o uso do estimador geoestatístico (krigagem de bloco), para estimativa do volume por talhão, é preferido por duas razões: proporciona estimativa da precisão sem viés e é de baixo custo quando comparado ao estimador clássico. / This research evaluated the use of applied geostatistic forestry inventory. Specifically, it evaluated: the continuity of spatial structure of four dendrometric characteristics, the adjustment methods and model selection of the semi variance function, the behavior of classic and geostatístic confidence intervals and the potential of the block krigage for the stand volumetric prediction. Data were obtained in a 987 ha of Eucalyptus grandis forest plantation aged 7 years, located in Itapetininga county- São Paulo State, belonging to Votorantim Pulp and Paper (VCP). The spatial continuity structure of volume, quadratic average diameter, basal area and dominant average height was evaluated through the anisotropic and isotropic semi variogrammes. Two semi variance function models were adjusted for volume, through four adjustment methods. The selection of the best model was made starting from the Akaike information criterion (AIC) and through the crossed validation and prediction techniques. Departing from stochastic simulations, using geostatistic model the performa nce of the classic and geoestatístic confidence interval covering was verified, in relation to the nominal covering. The stands volumetric prediction was obtained from the krigage with simulation in each plantation stand. It was verified that the dendrométric characteristics measured in the forestry inventory presented spatially structured. This result suggested that, in the forestry inventory processing, spatial component should be considered, i.e., the plots should not be treated separately. It seems tha t the AIC and the cross validation for semi variance function model selection must be associated. It was detected that both classic and geostatistic confidence intervals presented lower covering than that of the nominal covering, for a spatial continuous population. However, the confidence covering interval of the classic estimator was much lower than the nominal covering, showing substantial bias in the estimate of the average variance, when there is structure of spatial continuity. For fixed populations, the classic estimator provided observed covering equal to the nominal covering. Thus, proving that the validity of the randomization for use of the Central Limit Theorem, in the definition of the confidence interval, independently of the structure of space continuity. The use of the geoestatístic estimator (block krigage) for estimating stand volume, in the presence of spatial continuity, is preferred because it provides unbiased and precise estimate at lower cost as compared to the classic estimator.