Forests2015, 6(7), 2345-2370; doi:10.3390/f6072345 (registering DOI) - published 7 July 2015 Show/Hide Abstract
Abstract: Penang National Park (PNP), as Malaysia’s smallest national park, is one of the few naturally forested areas left on Penang Island, in Peninsular Malaysia. The main objective was to analyse users’ preferences and willingness to pay to enhance improved management of PNP for the dual aim of conservation and recreation. Structural equation modelling (SEM) was used to analyse the formation of attitudes towards different aspects of PNP. Results showed that implementing enforcements with rules and regulations and imposing permits and charges on certain activities were the most influential variables of PNPs’ perceptions. The results of a random parameter logit model (RPL) demonstrated that visitors placed the highest value on having adequate information about PNP, and the second-highest value on improvements in the park’s ecological management. The welfare measure for improvement in management of PNP against status quo is estimated at about MYR 9. Results also showed that demand for better conservation and management of PNP is relatively price-inelastic. Simulations of the results showed, under a MYR10 admission fee, that improvement in management would have 96% of market share compared with status quo. This study concluded that visitor entrance fees can and ought to be introduced as a means of financing conservation initiatives and possibly preventing congestion.
Forests2015, 6(7), 2324-2344; doi:10.3390/f6072324 - published 6 July 2015 Show/Hide Abstract
Abstract: A mycological supply function of wild edible fungi is determined by a set of forest and economic variables, among which climate variables stand out. Focusing on wild mushroom picking with commercial value (Lactarius deliciosus (L.) Gray) as an example, the main objective of this paper is to obtain empirical evidence about the impact of meteorological and economic variables on the mushroom supply. A multidisciplinary vector error correction (VEC) model for mushroom supply is estimated. Coefficients for the Error Correction Term (ECT) are all significant, at the 0.01 significance level, both in the model for prices and for collected mushrooms. The value of the ECT coefficient in the equation for prices is −0.086 (t-value: −9.321), and for the collected mushroom equation is 0.499 (t-value: 3.913). The impact of precipitation on price changes is −0.104 (t-value: −1.66), and the impact of temperature on mushroom harvest picking is 0.605 (t-value: 3.07). We find that including climate factors to explain mushroom supply considerably strengthens the explanatory power of the model, and in some cases greatly changes the results.
Forests2015, 6(7), 2307-2323; doi:10.3390/f6072307 - published 1 July 2015 Show/Hide Abstract
Abstract: Soil carbon (C) in three Ginkgo (Ginkgo biloba L.) agroforestry systems, afforestation (Ginkgo alone; G), and an agricultural cropping system were compared over a five-year period. The agroforestry systems were Ginkgo + Wheat (Triticum aestivum L.) + Peanut (Arachis hypogaea L.; GWP); Ginkgo+ Mulberry (Morus alba L.; GM); and Ginkgo + Rapa (Brassica napus L.) + Peanut (GRP). The agricultural system consisted of wheat and peanut (WP). Total soil carbon (TSC), soil organic (SOC) and inorganic carbon (SIC), and the pools of five SOC chemical fractions were measured. TSC and SOC were always lower under WP than the G-based planting systems, and TSC in the latter increased significantly across years in the top 20 cm. Stocks of SIC under WP were significantly greater than the G-based systems, whereas SOC fractions tended to be lower. Most fractions increased across years but not in WP.
Forests2015, 6(7), 2296-2306; doi:10.3390/f6072296 - published 30 June 2015 Show/Hide Abstract
Abstract: The concentration of the carbon-13 isotope (leaf δ13C) in leaves is negatively correlated with the mean annual precipitation (MAP) atlarge geographical scales. In this paper, we explain the spatial pattern of leaf δ13C variation for deciduous oriental oak (Quercus variabilis Bl.) across temperate and subtropical biomes and its sensitivity to climate factors such as MAP. There was a 6‰ variation in the leaf δ13C values of oak with a significant positive correlation with latitude and negative correlations with the mean annual temperature (MAT) and MAP. There was no correlation between leaf δ13C and altitude or longitude. Stepwise multiple regression analyses showed that leaf δ13C decreased 0.3‰ per 100 mm increase in MAP. MAP alone could account for 68% of the observed variation in leaf δ13C. These results can be used to improve predictions for plant responses to climate change and particularly lower rainfall.
Forests2015, 6(7), 2281-2295; doi:10.3390/f6072281 - published 30 June 2015 Show/Hide Abstract
Abstract: Successful management of forest systems requires a deeper understanding of the role of ecophysiological traits in enabling adaptation to high temperature and water deficit under current and anticipated changes in climate. A key attribute of leaf water relations is the water potential at zero turgor (πtlp), because it defines the operating water potentials over which plants actively control growth and gas exchange. This study examines the drivers of variation in πtlp with respect to species climate of origin and habitat water availability. We compiled a water relations database for 174 woody species occupying clearly delineated gradients in temperature and precipitation across the Australian continent. A significant proportion of the variability in πtlp (~35%) could be explained by climatic water deficit and its interaction with summertime maximum temperature, demonstrating the strong selective pressure of aridity and high temperature in shaping leaf water relations among Australian species. Habitat water availability (midday leaf water potential), was also a significant predictor of πtlp (R2 = 0.43), highlighting the importance of species ecohydrologic niche under a set of climatic conditions. Shifts in πtlp in response to both climatic and site-based drivers of water availability emphasises its adaptive significance and its suitability as a predictor of plant performance under future climatic change.
Forests2015, 6(6), 2261-2280; doi:10.3390/f6062261 - published 23 June 2015 Show/Hide Abstract
Abstract: A nonlinear equation system for individual tree diameter growth and mortality of natural Mongolian oak forests was developed based on 13,360 observations from 195 permanent sample plots in Northeast China. Weighted regression was used in a distance-independent diameter growth equation for dealing with heterocedasticity. Since diameter growth and mortality models have common predictors including the diameter at breast height (DBH), stand basal area (BA), basal-area-in-larger trees (BAL), and site index (SI), parameters were estimated using nonlinear three-stage least squares (N3SLS) and seemingly unrelated regression (SUR) which accounts for correlations of errors across models. The system equation provided better projection than individual fitting of the equation based on maximum likelihood estimation. Compared with the separate tree growth model, the simultaneous equations using N3SLS and SUR produced more efficient parameter estimation and smaller bias. Furthermore, N3SLS had more accurate projection. Overall, the simultaneous model will facilitate the growth and yield projection for better management of Mongolian oak forests in the region.