Resource-use,body condition and parasite load metrics indicate contrasting health of stocked and native game fishes in Canadian prairie lakes

This study evaluated the status of native and stocked fish species in 13 prairie lakes in central Canada over eight years (2007–14) using three metrics: resource-use (benthic versus pelagic carbon via stable isotopes); body condition (relative weight index W_r); and parasite load (cestode gut enumerations). Analyses included game and non-game fishes, like naturally occurring northern pike, Esox lucius L., and yellow perch, Perca flavescens Mitchill, but focused on stocked walleye, Sander vitreus (Mitchill) because it supports a robust recreational fishery. Walleye and northern pike were significantly more reliant on benthic carbon than yellow perch or forage fishes (p < 0.05), but this reliance was not associated with any measured environmental variables for any species. In lakes with game fishes, forage fishes exhibited higher reliance on benthic energy, possibly due to predator avoidance strategy, particularly yellow perch. Walleye body condition index was consistently lower (<95–105) than values exhibited by the other two game fishes (81–139), and parasites were only common in walleye and associated with lake-water salinity (r² = 0.93, p < 0.05) and sex (p < 0.05). Based on the results, the most desirable game fish, walleye, appears less resilient to environmental variability than northern pike and yellow perch, making this species more susceptible to impacts of future climate change.     

An assessment of the benefits and limitations of the shamba agroforestry system in Kenya and of management and policy requirements for its successful and sustainable reintroduction

The shamba system involves farmers tending tree saplings on state-owned forest land in return for being permitted to intercrop perennial food crops until canopy closure. At one time the system was used throughout all state-owned forest lands in Kenya, accounting for a large proportion of some 160,000 ha. The system should theoretically be mutually beneficial to both local people and the government. However the system has had a chequered past in Kenya due to widespread malpractice and associated environmental degradation. It was last banned in 2003 but in early 2008 field trials were initiated for its reintroduction. This study aimed to: assess the benefits and limitations of the shamba system in Kenya; assess the main influences on the extent to which the limitations and benefits are realised and; consider the management and policy requirements for the system’s successful and sustainable operation. Information was obtained from 133 questionnaires using mainly open ended questions and six participatory workshops carried out in forest-adjacent communities on the western slopes of Mount Kenya in Nyeri district. In addition interviews were conducted with key informants from communities and organisations. There was strong desire amongst local people for the system’s reintroduction given that it had provided significant food, income and employment. Local perceptions of the failings of the system included firstly mismanagement by government or forest authorities and secondly abuse of the system by shamba farmers and outsiders. Improvements local people considered necessary for the shamba system to work included more accountability and transparency in administration and better rules with respect to plot allocation and stewardship. Ninety-seven percent of respondents said they would like to be more involved in management of the forest and 80% that they were willing to pay for the use of a plot. The study concludes that the structural framework laid down by the 2005 Forests Act, which includes provision for the reimplementation of the shamba system under the new plantation establishment and livelihood improvement scheme (PELIS) [It should be noted that whilst the shamba system was re-branded in 2008 under the acronym PELIS, for the sake of simplicity the authors continue to refer to the ‘shamba system’ and ‘shamba farmers’ throughout this paper.], is weakened because insufficient power is likely to be devolved to local people, casting them merely as ‘forest users’ and the shamba system as a ‘forest user right’. In so doing the system’s potential to both facilitate and embody the participation of local people in forest management is limited and the long-term sustainability of the new system is questionable. Suggested instruments to address this include some degree of sharing of profits from forest timber, performance related guarantees for farmers to gain a new plot and use of joint committees consisting of local people and the forest authorities for long term management of forests.

Analysis of information used in the management of plant genetic resources: a case study from northwestern Mato Grosso,Brazil

Evaluation and monitoring are critical to agroforestry (AFS) project management, especially if they aim to contribute to use and conservation of biodiversity and plant genetic resources. A methodology to analyze information used in decision-making processes was developed and applied in a biodiversity conservation project in the Brazilian Amazon. Quality of information gathered at landscape, AFS, species (Bactris gasipaes Kunth, both wild and cultivated varieties) and genetic diversity levels in three dimensions was analyzed. The information at the landscape level was good, while that in the organizational-institutional and socio-economic dimensions was acceptable; information gaps were serious in the genetic-ecological dimension. Ecological and economic functionality assessment based on indicators built upon reported administrative actions suggests that information related to conservation played a greater role in decision-making and management than information associated with use and development. The application of the methodology proved instrumental for enhancing efficacy of decision-making within an adaptive management approach to plant genetic resources use and conservation.     

Invasion and management of a woody plant, Lantana camara L., alters vegetation diversity within wet sclerophyll forest in southeastern Australia

Plant invasions of natural communities are commonly associated with reduced species diversity and altered ecosystem structure and function. This study investigated the effects of invasion and management of the woody shrub Lantana camara (lantana) in wet sclerophyll forest on the south-east coast of Australia. The effects of L. camara invasion and management on resident vegetation diversity and recruitment were determined as well as if invader management initiated community recovery. Vascular plant species richness, abundance and composition were surveyed and compared across L. camara invaded, non-invaded and managed sites following L. camara removal during a previous control event by land managers. Native tree juvenile and adult densities were compared between sites to investigate the potential effects of L. camara on species recruitment. Invasion of L. camara led to a reduction in species richness and compositions that diverged from non-invaded vegetation. Species richness was lower for fern, herb, tree and vine species, highlighting the pervasive threat of L. camara. For many common tree species, juvenile densities were lower within invaded sites than non-invaded sites, yet adult densities were similar across all invasion categories. This indicates that reduced species diversity is driven in part by recruitment limitation mechanisms, which may include allelopathy and resource competition, rather than displacement of adult vegetation. Management of L. camara initiated community recovery by increasing species richness, abundance and recruitment. While community composition following L. camara management diverged from non-invaded vegetation, vigorous tree and shrub recruitment signals that long-term community reinstatement will occur. However, secondary weed invasion occurred following L. camara control. Follow-up weed control may be necessary to prevent secondary plant invasion following invader management and facilitate long-term community recovery.     

Slit-shaped gaps are a successful silvicultural technique to promote Picea abies regeneration in mountain forests of the Swiss Alps

Many mountain forests in the Swiss Alps are dense and overmature. The resulting lack of tree regeneration threatens their future ability to provide products and services for humans, e.g., protecting settlements and infrastructure against avalanches. To promote natural regeneration, slit-shaped gaps have been cut since the 1980s in many of Switzerland's Alpine forests dominated by Norway spruce (Picea abies). However, little is known about the success of this silvicultural technique. We sampled 38 gaps in 2001 and 2006 and analysed the density and vitality of P. abies seedlings in these gaps, and monitored the growth and survival of selected seedlings between the two inventories. The gaps analysed were located in upper montane and subalpine P. abies dominated forests in the Vorderrhein valley in the Grisons. The density and vitality of large (10–129 cm tall) and small (<10 cm tall) P. abies seedlings were assessed in three parallel transects running perpendicular to the longitudinal axis of each gap. The mean density of large seedlings increased significantly between 2001 and 2006 from 0.1 to 0.3 seedlings/m², whereas that of small seedlings stayed constant at 0.7 seedlings/m², even though it shifted locally between inventories. Significantly higher regeneration densities were found for gaps with NE–SW orientation (afternoon sun) and for those located at lower altitudes. While in gaps on North-facing slopes large P. abies seedlings were more frequent on the middle transect, in gaps on South-facing slopes they were denser near the lower gap edge which is usually less exposed to direct radiation. As expected regeneration density was significantly higher within the gaps than just outside underneath the adjacent stands for all P. abies seedlings. Damage caused by browsing did not turn out to be problematic in this study site. From the selected 280 small seedlings monitored in 2001, 53% died until 2006, 33% became large seedlings and 14% remained small (<10 cm). Our results suggest that creating slit-shaped gaps is a successful procedure to promote P. abies regeneration in the upper montane and subalpine belt of the northern intermediate Alps and helps to preserve protection forests and their goods and services for the coming generations.     

Spatial patterns of litter-dwelling taxa in relation to the amounts of coarse woody debris in European temperate deciduous forests

We studied the leaf litter-dwelling fauna of managed deciduous forests and primeval reference sites in Western and Central Europe and addressed the questions if the higher overall species richness close to downed coarse woody debris (CWD) is related to intra-specific or inter-specific aggregation, if the aggregation pattern changes with the amount of CWD on the forest floor, and how much CWD is needed for different taxa. The analysis is based on shelled Gastropoda, Diplopoda/Isopoda, Chilopoda and Coleoptera. Among-sample heterogeneity was lower close to CWD than distant from CWD. This was most pronounced in Diplopoda/Isopoda and Gastropoda. Diplopoda/Isopoda are comparatively mobile and assemblages were already quite homogenous close to CWD at levels above 5 m³ downed deadwood ha⁻¹. Gastropoda have a low mobility, and more than 20 m³ downed deadwood ha⁻¹ is needed for assemblage homogeneity. We further focused on the Gastropoda as sensitive indicators. Enhanced densities and species richness close to CWD were not a simple function of leaf litter weight, thus effects of densities on heterogeneity are not solely driven by leaf litter accumulation close to CWD. In contrast to euryecious litter-dwellers such as the Punctidae, stenecious slow active dispersers such as the Clausiliidae clearly require more than 20 m³ CWD ha⁻¹ for an even distribution. Specialists depending on CWD even seem to have gone extinct in some managed forests. For conserving the litter-dwelling fauna, we propose a target of at least 20 m³ downed CWD ha⁻¹ in already managed forests and rigorous restrictions for deadwood removal from still (almost) pristine systems.     

Partitioning of soil respiration into its autotrophic and heterotrophic components by means of tree-girdling in old boreal spruce forest

Forests accumulate much less carbon than the amount fixed through photosynthesis because of an almost equally large opposing flux of CO₂ from the ecosystem. Most of the return flux to the atmosphere is through soil respiration, which has two major sources, one heterotrophic (organisms decomposing organic matter) and one autotrophic (roots, mycorrhizal fungi and other root-associated microbes dependent on recent photosynthate). We used tree-girdling to stop the flow of photosynthate to the belowground system, hence, blocking autotrophic soil activity in a 120-yr-old boreal Picea abies forest. We found that at the end of the summer, two months after girdling, the treatment had reduced soil respiration by up to 53%. This figure adds to a growing body of evidence indicating (t-test, d.f. = 7, p < 0.05) that autotrophic respiration may contribute more to total soil respiration in boreal (mean 53 ± 2%) as compared to temperate forests (mean 44 ± 3%). Our data also suggests that there is a seasonal hysteresis in the response of total soil respiration to changes in temperature. We propose that this reflects seasonality in the tree below-ground carbon allocation.     

Calibrating the self-thinning frontier

Calibration of the self-thinning frontier in even-aged monocultures is hampered by scarce data and by subjective decisions about the proximity of data to the frontier. We present a simple model that applies to observations of the full trajectory of stand mean diameter across a range of densities not necessarily close to the frontier. Development of the model is based on a consideration of the slope s = ln(N_t/N_t−1)/ln(D_t/D_t−1) of a log-transformed plot of stocking N_t and mean stem diameter D_t at time t. This avoids the need for subjective decisions about limiting density and allows the use of abundant data further from the self-thinning frontier. The model can be solved analytically and yields equations for the stocking and the stand basal area as an explicit function of stem diameter. It predicts that self-thinning may be regulated by the maximum basal area with a slope of −2. The significance of other predictor variables offers an effective test of competing self-thinning theories such Yoda's −3/2 power rule and Reineke's stand density index.     

The use of historical range and variability (HRV) in landscape management

This paper examines the past, present, and future use of the concept of historical range and variability (HRV) in land management. The history, central concepts, benefits, and limitations of HRV are presented along with a discussion on the value of HRV in a changing world with rapid climate warming, exotic species invasions, and increased land development. This paper is meant as a reference on the strengths and limitations of applying HRV in land management. Applications of the HRV concept have specific contexts, constraints, and conditions that are relevant to any application and are influential to the extent to which the concept is applied. These conditions notwithstanding, we suggest that the HRV concept offers an objective reference for many applications, and it still offers a comprehensive reference for the short-term and possible long-term management of our nation's landscapes until advances in technology and ecological research provide more suitable and viable approaches in theory and application.