Comparison of Water Dynamics in Aspen and Conifer: Implications for Ecology Water Yield Augmentation

Differences in water dynamics between deciduous aspen (Populus tremuloides) and co-occurring evergreen conifer species in the Northern Rocky Mountains result from complex physical and biological interactions. A comprehensive evaluation of individual water transfer mechanisms was used to elucidate the relative importance of several components of the hydro logic cycles of aspen and conifer, and determine which water transfer mechanisms have potential to cause differences in net water yield. Adjacent aspen and conifer stands were monitored to determine snow accumulation and ablation (snow survey), soil moisture recharge (capacitance probes), snowpack sublimation (sublimation pan), transpiration period (thermal dissipation probes), and evapotranspiration (soil water content). Snow accumulation was 34 and 44% higher in aspen during springs of 2005 and 2006, respectively. Ablation rates in aspen (9.58 mm day-1 ) were nearly double that of conifer (4.9 mm day-1). When changes in soil moisture (due to over winter snowmelt) were combined with snow accumulation in 2006, aspen had greater potential (42-83%) for runoff and groundwater recharge. Snowpack sublimation during the ablation period was not different between open, aspen, and conifer sites and comprised -1). Summertime ET rate was higher in an aspen stand (3.6 mm day-1) than in an adjacent conifer stand (2.7 mm day-1) amounting to ~126 mm more water lost over the growing season, but largely reflected post-ablation differences in stored soil water. The net effects of these water transfer processes could result in more watershed water yield from aspen than conifer forests. However, the difference in water yield between these two forests will largely depend on the fate of snow lost from the conifer canopy. Snow intercepted by conifer branches can be removed by the processes of sublimation (reduces water yield) and redistribution (does not affect water yield). Future studies should focus on partitioning the ratio of sublimation to redistribution to predict hydro logic response of vegetation conversions for water yield augmentation in snow-dominated watersheds

Fire - Herbivory Interactions in an East African Savanna: Effects on Acacia Drepanolobium Trees

Globally, changes in plant community structure have occurred in ecosystems where humans have altered natural disturbance regimes. Many plants have adaptive life histories and morphological traits that have coevolved with fire and herbivory, which allows them to thrive despite repeated tissue losses. Therefore, altering the type, frequency, or severity of disturbance affects individual plant growth and competition among species. When these changes benefit or disadvantage different plant functional groups (i.e., grasses, shrubs, trees) it alters ecosystem structure and function. Understanding and predicting these vegetation changes, is critical for conservation and management of biodiversity, wildlife habitat, livestock forage, and water. Savannas are characterized by the codominance of grasses and trees, but the proportion of tree cover responds dynamically to changes in precipitation, fire, and herbivory. These factors often cause a ‘demographic bottleneck,’ which delays transitions from sapling size (1 m). In this dissertation, I investigated several fire × herbivory interactions to gain a mechanistic understanding of sapling recruitment processes that ultimately affect savanna structure. I made use of a long-term experiment that used semi-permeable fencing to manipulate presence and absence of different types of herbivores, to explore how fire and different combinations of domestic cattle, meso-wildlife, and megaherbivores (elephant and giraffe) affect sapling recruitment. First, I found clear evidence that a wide range of tree height classes resprout after being top-killed by fire, but they were all subsequently kept short by meso-wildlife browsing. Elephants played a key role in suppressing the largest resprouts after fire possibly because fire had reduced the presence of ant mutualists that defend the trees. Second, I found that in the absence of fire, cattle and wildlife indirectly affected saplings by altering competition with neighboring vegetation. Saplings competed with grass and trees during above-average rainfall years. Bare ground—a condition often caused by overgrazing—was positively associated with sapling growth. The highest sapling growth, however, occurred where large neighbor trees were absent, a condition maintained primarily by elephants browsing and damaging large neighbor trees. Finally, I found that saplings conditioned by pre-fire wildlife “browsing legacies” had high tolerance to combined fire and wildlife browsing. These results help explain how saplings tolerate repeated tissue loss to disturbance. Understanding how interactions between fire and herbivory affect sapling recruitment will help managers effectively use natural disturbance processes to manage savanna structure and function

Proyecto de Ordenación Silvopastoral del Monte “Los Hoyos”, en el término municipal de Berzosilla (Palencia)

[ES] Se ha realizado la ordenación silvopastoral del monte perteneciente a la entidad local menor de Olleros de Paredes Rubias, situado en el municipio de Berzosilla (Palencia), para un periodo de vigencia de 20 años. Además del estudio y planificación de ciertos aprovechamientos en el monte, el hecho de constituir su primera ordenación ha supuesto la necesidad de satisfacer cuestiones relativas a su historia y límites administrativos. El proyecto pretende integrar diversos objetivos, tanto de gestión como de compilación y puesta a disposición de los propietarios y gestores, de una información referente al monte lo más completa y conveniente posible. El monte, de 188,6 hectáreas, parte de una situación inicial derivada del aprovechamiento inmemorial de los pastos y la extracción continuada de leñas, y en el que el peso de los distintos aprovechamientos silvopastorales ha disminuido exponencialmente en los últimos 100 años. Destacan las masas arboladas provenientes de un tratamiento en monte medio o monte bajo con 108,2 ha, los pastos herbáceos y matorrales con 60,1 ha, y los cultivos agrícolas con 15,6 ha. Los objetivos de gestión se basan en la organización de la masa arbolada y la estimación de una carga ganadera sustentable por las comunidades pascícolas del monte. Desde el punto de vista selvícola, el monte requiere la reconstrucción progresiva de masas maduras, estando muy desprovisto de madera gruesa y muy gruesa. Por otra parte, las condiciones socioeconómicas y silvopastorales del monte han llevado a priorizar e intensificar las actuaciones selvícolas sobre las masas arboladas menos degradadas, situadas en las mejores estaciones y con buena accesibilidad, dejando actuar a los procesos naturales en el resto de masas. La carga ganadera sustentable por el conjunto de comunidades pascícolas del monte, mediante un pastoreo correctamente articulado en el tiempo y en el espacio, resulta de 55 – 91 unidades de ganado mayor (UGM). El periodo vegetativo de los pastos herbáceos, estimado a partir del periodo de pastoreo, va desde mediados de marzo o principios de abril, hasta finales de septiembre o mediados de octubre, variando de unos años a otros. En cuanto al aprovechamiento leñoso, la ordenación planifica intervenciones sobre 7 unidades de gestión, interviniéndose cada año sobre una de ellas. En 6 de dichas unidades predomina el haya (Fagus sylvatica), mientras que en la otra lo hace el roble marojo (Quercus pyrenaica). Se ha fijado un “estado objetivo” o “estado de equilibrio” hacia el que se pretende dirigir las masas, consistiendo la selvicultura en la irregularización o conversión de las mismas, de una situación inicial de monte medio a una de monte alto irregular con un nivel de existencias moderado.La estructura actual de las masas requiere diferenciar dos tipos de intervenciones selvícolas, que se realizarán al mismo tiempo con una rotación de 7 años: claras fuertes por lo alto en el estrato inferior (latizales y pies menores), cuyo peso durante la primera rotación será del 40% del volumen; cortas por entresaca a favor de los pies de mejor calidad de todas las especies, cuyo peso durante la primera rotación varía entre el 10% y el 25%. Las cortas por entresaca se centran en las categorías diamétricas de madera pequeña y media, conservándose por lo general la totalidad de madera gruesa existente. Antes de la segunda y tercera rotación, será necesario medir el crecimiento de las masas para ajustar la posibilidad y el peso de las cortas. Para ello se planifica la realización de inventarios dasométricos de bajo coste, que permitirán evaluar el comportamiento de las masas tras las intervenciones selvícolas. La extracción de leñas ha sido el único aprovechamiento maderero que se realiza en el monte desde hace décadas, y se estima una demanda inferior a 300 estéreos anuales. Las actuaciones planificadas permitirán extraer anualmente una cantidad de leñas que varía entre 300 y 800 estéreos. Debido a la lejanía de las masas respecto al “estado de equilibrio” o “estado objetivo” definido, los productos extraídos durante la vigencia de esta ordenación serán destinados a leñas vecinales. La mejora de composición en especies y en pies de calidad, así como la capitalización gradual de la masa, permitirán alcanzar en el futuro una situación favorable a la venta de madera de calidad. La selvicultura propuesta promueve la producción continuada de madera de alta calidad, aumentando y regularizando los ingresos que aportará este uso a medio y largo plazo. La mezcla de especies y de categorías diamétricas dotará a las masas arbóreas de una gran flexibilidad de gestión y de una excelente capacidad de respuesta a las exigencias del mercado maderero, la evolución del clima, la resistencia a insectos y enfermedades o a los accidentes meteorológicos.Lamalfa Díaz, M. (2014). Proyecto de Ordenación Silvopastoral del Monte “Los Hoyos”, en el término municipal de Berzosilla (Palencia). http://hdl.handle.net/10251/46767.Archivo delegad

Use of Prescribed Fire in Rangeland Management: A Training Manual

Course Outcomes Learn about the role of fire in rangeland ecosystems. Learn how to plan and implement a prescribed fire. Learn how to monitor fire effects to assist management decision-making. Make progress towards conceptualizing a community-based, fire management program on the Borana Plateau

Unraveling Fire and Herbivore Interactions to Manage Tree Cover in an African Savanna

Savanna ecologist continue to debate the relative importance of fire and herbivory disturbances in affecting local savanna tree cover and applied issues such as bush encroachment . Contemporary grass-tree co-existence models and a large body of literature emphasize the importance of both top-down disturbance types. However, no fully replicated experiments have simultaneously manipulated fire and herbivore regimes to directly examine potentially synergistic interactions controlling tree demography. We hypothesized that the “fire trap” wherein trees are repeatedly top-killed by fire and prevented from transitioning to taller fire resistant height classes, is further reinforced by the negative effects of ungulate browsing on tree height. Conversely, grazing by livestock or the absence of all herbivory was expected to increase height and biomass of re-sprouting trees after fire. We used the Kenya Long Term Exclosure Experiment (KLEE), which for the past 20 years has restricted access by six different combinations of mega-herbivores (i.e., elephant and giraffe), meso-wildlife (e.g. gazelle, oryx, cape buffalo), and cattle. Within each of 18 four-ha KLEE plots a 30 X 30 meter prescribed burn was implemented in 2013. We used linear regression models to compare pre-fire tree height and post-fire tree re-sprout height and morphology relationships among the six different herbivore treatments. One and a half years after the fires, the relationship between pre-fire tree height and post-fire tree height was dependent upon both the herbivore treatment and colonization by ant mutualists that defend trees against browsing. In the presence of wildlife (i.e. browsers) trees compensated for lost tissue by increasing the number of lateral basal stems. We expect that these shorter multi-stemmed growth forms will have prolonged susceptibility to future fires reinforcing the negative effects of fire on tree cover. These results highlight that long term changes in tree cover may be dependent upon the stocking rate/ density of both wild and domestic herbivores following disturbance

Fire Herbivore Trap: Effects Herbivory on Post-Fire Tree Re-sprout Size and Morphology in Acacia drepanolobium Savanna.

In savanna ecology, grass-tree co-existence models emphasize the importance of two top-down disturbances herbivory and fire in controlling tree cover. However, no fully replicated experiments have simultaneously manipulated both fire and herbivory regimes to examine potentially synergistic interactions controlling tree demography. We hypothesized that a fire trap wherein trees are repeatedly top-killed by fire and prevented from transitioning to taller fire resistant height classes, is further reinforced by the negative effects of ungulate browsing on tree height. Conversely, grazing by livestock or the absence of all herbivory was expected to increase height and biomass of trees top-killed by fire. The Kenya Long Term Exclosure Experiment (KLEE) is a replicated factorial experiment that manipulates access by six different combinations of mega-herbivores (i.e., elephant and giraffe), wildlife (e.g. gazelle, oryx, cape buffalo), and cattle. Within each of 18 four-ha KLEE plots 30 X 30 meter prescribed burns were implemented in 2013. We used a generalized linear models to compare pre-fire tree height and post-fire tree re-sprout height and morphology relationships among six different herbivore assemblages. One and a half years after fire, the relationship of pre-fire tree size to post fire total stem length (biomass proxy) did not depend on herbivore treatment, however the relationship between pre-fire tree size and post-fire tree height did vary with treatment. Browsed trees compensated for lost tissue by growing laterally and increasing branch length. These shorter growth forms are more susceptible to future fires reinforcing the negative effects of fire on tree height. These results highlight that post fire vegetation responses are highly dependent upon the type and stocking rate/ density of both wild and domestic herbivores. Understanding how fire and herbivory interact to affect tree cover (i.e. bush encroachment) has important applications for wildlife habitat management, livestock production, and pastoral livelihoods in East Africa

Differential snowpack accumulation and water dynamics in aspen and conifer communities: implications for water yield and function

Early succession aspen and late succession conifer forests have different architecture and physiology affecting hydrologic transfer processes. An evaluation of water pools and fluxes was used to determine differences in the hydrologic dynamics between stands of quaking aspen (Populus tremuloides) and associated stands of mixed conifer consisting of white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii) and Engelmann spruce (Picea engelmannii). In 2005 and 2006, measurements of snow water accumulation (SWE), snow ablation (melt), soil water content, snowpack sublimation, and evapotranspiration (ET) were measured in adjacent aspen and conifer stands. Peak (snow water equivalent) SWE averaged 34 to 44% higher in aspen in 2005 (average snow pack) and 2006 (above average snowpack), respectively, while snow ablation rates were greater in aspen stands (21 mm day-1) compared to conifer stands (11 mm day-1). When changes in soil water content (due to over winter snowmelt) were combined with peak snow accumulation in 2006, aspen had greater potential (42-83%) water yield for runoff and groundwater recharge. Snowpack sublimation during the ablation period was not significantly different between meadow, aspen, and conifer sites and comprise