Effects Of Forest Changes Research Articles

Effects of Forest Changes on Summer Surface Temperature in Changbai Mountain, China

The area and vegetation coverage of forests in Changbai Mountain of China have changed significantly during the past decades. Understanding the effects of forests and forest coverage change on regional climate is important for predicting climate change in Changbai Mountain. Based on the satellite-derived land surface temperature (LST), albedo, evapotranspiration, leaf area index, and land-use data, this study analyzed the influences of forests and forest coverage changes on summer LST in Changbai Mountain. Results showed that the area and vegetation coverage of forests increased in Changbai Mountain from 2003 to 2017. Compared with open land, forests could decrease the summer daytime LST (LSTD) and nighttime LST (LSTN) by 1.10 °C and 0.07 °C, respectively. The increase in forest coverage could decrease the summer LSTD and LSTN by 0.66 °C and 0.04 °C, respectively. The forests and increasing forest coverage had cooling effects on summer temperature, mainly by decreasing daytime temperature in Changbai Mountain. The daytime cooling effect is mainly related to the increased latent heat flux caused by increasing evapotranspiration. Our results suggest that the effects of forest coverage change on climate should be considered in climate models for accurately simulating regional climate change in Changbai Mountain of China.

Assessing hydrological responses to reforestation and fruit tree planting in a sub-tropical forested watershed using a combined research approach

Fruit tree planting is often considered as one of reforestation practices in the past decades in many parts of China because it increases forest coverage while gaining short-term economic benefits. However, the effects of large-scale fruit tree planting on water resources at the watershed scale are rarely assessed, especially in subtropical China. In this study, the forested watershed (Jiujushui watershed, 261.4 km2), located in Southeastern China, was selected to examine the responses of major flow components including baseflow, surface runoff, and total streamflow to both reforestation (e.g., Cunninghamia lanceolata (Lamb.) Hook and Pinus massoniana Lamb.) and fruit tree planting (e.g., Citrus reticulate Blanco) practices. The study period (1961–2016) was split into three sub-periods including reference, reforestation and fruit tree planting. The combined approach including pair-wise method and separation of relative contributions was adopted in this study. The former was used to test the statistical relations between forest changes and flow components, while the latter (sensitivity-based and time trend methods) was applied to quantitatively separate the relative contributions of forest changes and climatic variability to each flow component so that the effects of forest changes (reforestation and fruit tree planting) on flow components can be quantified and compared. Results from the pair-wise technique showed that reforestation and fruit tree planting had no significant effects on total streamflow. However, reforestation significantly increased base flow by 15% (p = 0.03), while fruit tree planting did not. In contrast, surface runoff was significantly increased by fruit tree planting (p = 0.048), while it was not by reforestation. The results from the separation technique showed that in the reforestation period, the relative contributions of reforestation to surface runoff, baseflow and total streamflow were 23.9%, 67.3% and 50.9%, respectively, in comparison with 76.1%, 32.7% and 49.1% from climate variability, highlighting that reforestation had greater effects on base flow. However, fruit tree planting accounted for 54.4%, 48.8% and 57.3% of total streamflow, baseflow and surface runoff variations, while climatic variability were responsible for 45.6%, 51.3% and 42.7%, respectively in the fruit tree planting period, demonstrating that fruit tree planting had greater effects on surface runoff. Thus, the results from both techniques clearly demonstrated that forest recovery through reforestation effectively increased baseflow, while fruit tree planting caused increasing of surface runoff. We also conclude that the combination approach provides a robust and complementary research framework for assessing the hydrological effects of reforestation in a single watershed.

Replacement of native forests by conifer plantations affects fungal decomposer community structure but not litter decomposition in Atlantic island streams

Forest change occurs worldwide, especially on islands where space is a limiting factor for human activities. The replacement of diverse native forests by tree monocultures and subsequent changes in litter input characteristics can have strong effects on stream communities and processes. Aquatic decomposers and litter decomposition can be particularly sensitive to forest change due to their dependence on terrestrial litter supply and on litter characteristics. However, studies addressing the effects of forest changes, and conifer plantations in particular, on stream litter decomposition and associated decomposers are scarce. Here, we assessed the effects of the replacement of native laurel forests in São Miguel island, Azores archipelago, by commercial conifer plantations (Cryptomeria japonica (L. f.) D. Don) on litter decomposition and associated fungal decomposers. Leaves of the native broadleaf tree Ilex perado Aiton and conifer needles were enclosed in mesh bags and incubated in three streams flowing through conifer plantations and three streams flowing through native laurel forests in winter 2015 for determination of litter decomposition rates, and aquatic hyphomycete community structure and reproductive activity (one stream per type). Aquatic hyphomycete communities’ structure strongly differed between native and conifer streams as a result from differences in the total number of species recorded (higher in the native stream), species identity (only 10 species, out of 26, were common to both streams) and species evenness (higher in the native stream). These differences in communities between streams likely result from changes in litter inputs characteristics between native and conifer streams and from aquatic hyphomycetes having substrate preferences. Differences in aquatic hyphomycete communities were not accompanied by differences in litter decomposition rates between native and conifer streams, which likely results from functional redundancy between decomposer communities and suggests that community structure and function may not always be tightly coupled. Litter decomposition rates did not differ between native and conifer species because I. perado leaves were tough and had a tick waxy cuticle, which may have limited microbial development, as for the conifer needles. Thus, the replacement of native laurel forests by conifer plantations did not affect litter decomposition in Azorean streams likely because litter is recalcitrant and decomposition is driven by microbes. However, changes in aquatic hyphomycete communities arriving from forest change may have unpredictable effects in case of additional environmental change. Hence, to prevent unwanted effects of changes in microbial communities, a riparian buffer of native vegetation should be maintained in conifer plantations.

Indirect Effects of Emerald Ash Borer-Induced Ash Mortality and Canopy Gap Formation on Epigaeic Beetles

Exotic herbivorous insects have drastically and irreversibly altered forest structure and composition of North American forests. For example, emerald ash borer (Agrilus planipennis Fairmaire) from Asia has caused wide-scale mortality of ash trees (Fraxinus spp.) in eastern United States and Canada. We studied the effects of forest changes resulting from emerald ash borer invasion on epigaeic or ground beetles (Coleoptera: Carabidae) along a gradient of ash dieback and gap sizes in southeastern Michigan. Ground beetles were sampled in hydric, mesic, and xeric habitats in which black (Fraxinus nigra Marshall), green (Fraxinus pennsylvanica Marshall), and white (Fraxinus americana L.) ash were the most common species, respectively. During 2006-2007, we trapped 2,545 adult ground beetles comprising 52 species. There was a negative correlation between percent ash tree mortality in 2006 and catches of all beetles. Catches of Agonum melanarium Dejean (in 2006) and Pterostichus mutus (Say) (in 2006-2007) were negatively correlated with tree mortality and gap size, respectively. However, catches of Pterostichus corvinus Dejean were positively correlated with gap size in 2006. As ash mortality and average gap size increased from 2006 to 2007, catches of all beetles as well as P. mutus and Pterostichus stygicus (Say) increased (1.3-3.9 times), while species diversity decreased, especially in mesic and xeric stands. Cluster analysis revealed that beetle assemblages in hydric and mesic stand diverged (25 and 40%, respectively) in their composition from 2006 to 2007, and that hydric stands had the most unique beetle assemblages. Overall, epigaeic beetle assemblages were altered in ash stands impacted by emerald ash borer; however, these impacts may dissipate as canopy gaps close.

How do climate and forest changes affect long‐term streamflow dynamics? A case study in the upper reach of Poyang River basin

AbstractIn forested watersheds, forest changes and climatic variability have been commonly recognized as two major drivers for streamflow variations. Previous research has separated their relative contributions but mainly focused on either deforestation and climate or reforestation and climate, but rarely with single studies on both. This study used the Meijiang watershed (6983·2 km2), situated in the upper reach of the Poyang Lake basin, as an example to quantify how climate and forest changes (both deforestation and reforestation) consecutively affect streamflow dynamics. Two methods, namely modified double‐mass curves and sensitivity‐based approach, were used in this study. Two breakpoints (years 1968 and 1985) with significant annual streamflow changes were detected, and together with the control period, they were then used to define three distinct periods: the control (1957–1967), deforestation (1968–1984) and reforestation (1985–2006) periods. Our results show that in the deforestation period, the average annual streamflow increment attributed to deforestation was 112·78 mm year−1, while the annual streamflow variation attributed to climate variability was −111·39 mm year−1. In the reforestation period, the average annual streamflow decrease caused by reforestation was −51·04 mm year−1, while the annual streamflow variation attributed to climate variability was 52·52 mm year−1. The sensitivity‐based approach also provided similar results. The positive and negative values in the streamflow changes suggest offsetting effects between forest changes and climate variability in both deforestation and reforestation periods. The similar magnitudes of streamflow changes demonstrate that the hydrological effects of forest changes can be as great as those caused by climate change. Copyright © 2014 John Wiley & Sons, Ltd.

Quantifying the Relative Contributions of Forest Change and Climatic Variability to Hydrology in Large Watersheds: A Critical Review of Research Methods

Forest change and climatic variability are two major drivers for influencing change in watershed hydrology in forest–dominated watersheds. Quantifying their relative contributions is important to fully understand their individual effects. This review paper summarizes the progress on quantifying the relative contributions of forest or land cover change and climatic variability to hydrology in large watersheds using available case studies. It compared pros and cons of various research methods, identified research challenges and proposed future research priorities. Our synthesis shows that the relative hydrological effects of forest changes and climatic variability are largely dependent on their own change magnitudes and watershed characteristics. In some severely disturbed watersheds, impacts of forest changes or land use changes can be as important as those from climatic variability. This paper provides a brief review on eight selected research methods for this type of research. Because each method or technique has its own strengths and weaknesses, combining two or more methods is a more robust approach than using any single method alone. Future research priorities include conducting more case studies, refining research methods, and considering mechanism-based research using landscape ecology and geochemistry approaches.

Impacts of forest changes on hydrology: a case study of large watersheds in the upper reaches of Minjiang River watershed in China

Abstract. Quantifying the effects of forest changes on hydrology in large watersheds is important for designing forest or land management and adaptation strategies for watershed ecosystem sustainability. Minjiang River watershed, located in the upper reach of the Yangtze River basin, plays a strategic role in the environmental protection and economic and social well-being for both the watershed and the entire Yangtze River basin. The watershed lies in the transition zone from Sichuan Basin to Qinghai-Tibet Plateau with a size of 24 000 km2. Due to its strategic significance, severe historic deforestation and high sensitivity to climate change, the watershed has long been recognized as one of the highest priority watersheds in China for scientific research and resource management. The purpose of this review paper is to provide a state-of-the-art summary on what we have learned from several recently completed research programs (one of them known as "973 of the China National Major Fundamental Science" from 2002 to 2008). This summary paper focused on how land cover or forest change affected hydrology at both forest stand and watershed scales in this large watershed. Inclusion of two different spatial scales is useful, because the results from a small spatial scale (e.g. forest stand level) can help interpret the findings on a large spatial scale. Our review suggests that historic forest harvesting or land cover change has caused significant water yield increase due to reduction of forest canopy interception and evapotranspiration caused by removal of forest vegetation on both spatial scales. The impact magnitude caused by forest harvesting indicates that the hydrological effects of forest or land cover changes can be as important as those caused by climate change, while the opposite impact directions suggest their offsetting effects on water yield in the Minjiang River watershed. In addition, different types of forests have different magnitudes of evapotranspiration (ET), with the lowest in old-growth natural coniferous forests (Abies faxoniana Rehd. et Wils.) and the highest in coniferous plantations (e.g. Picea asperata Mast.) among major forest types in the study watershed. This suggests that selection of different types of forests can have an important role in ET and consequently water yield. Our synthesis indicates that future reforestation and climate change would likely produce the hydrological effects in the same direction and thus place double the pressure on water resource as both key drivers may lead to water yield reduction. The findings can support designing management strategies for protection of watershed ecological functions in the context of future land cover and climate changes.