Chapter 1 Foliar Habit and Leaf Longevity Chapter 2 Leaves: Evolution, ontogeny and death Chapter 3 Quantifying Leaf Longevity Chapter 4 Theories of Leaf Longevity Chapter 5 Phylogenetic Variation in Leaf Longevity Chapter 6 Key Elements of Foliar Function Chapter 7 Endogenous Influences on Leaf Longevity Chapter 8 Exogenous Influences on Leaf Longevity Chapter 9 Biogeography of Leaf Longevity and Foliar habit Chapter 10 Ecosystem perspectives on leaf longevity References Index

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Ecology of Leaf Longevity

Questions: How can we understand the limitations to plant growth at high altitudes? Our aimwas to test the hypotheses that for alpine grasslands along a large altitudinal gradient in semi-arid regions, plant growth is mainly limited by drought at low altitudes but by low temperature at high altitudes, resulting in a
unimodal pattern of biomass and productivity associated with an optimal combination of temperature and precipitation. Such knowledge is important to understanding the response of alpine ecosystems to climate change.
Location: We conducted a 5-yr livestock exclosure experiment along the southfacing slope of the Nyaiqentanglha Mountains, central Tibetan Plateau.
Methods: We measured above- and below-ground biomass, species richness, leaf d13C and water potential, and related climate and soil variables across 42 fenced and unfenced quadrats near seven HOBO weather stations along the slope. The vegetation changed from alpine steppe-meadow at 4390–4500 m to alpinemeadow at 4600–5210 m.
Results: Total above- and below-ground biomass across fenced and unfenced quadrats increased with increasing altitude up to 4950–5100 m, and then decreased above 5100 m. Altitudinal trends in leaf d13C and water potential of dominant species also showed a unimodal pattern corresponding to that of vegetation biomass. Total above- and below-ground biomass as well as sedge above-ground biomass all showed a quadratic relationship with mean temperatures and the ratio of growing season precipitation (GSP) to 5 °C accumulated
temperature (AccT; R2 = 0.830.88, P < 0.001). In general, above- and below-ground biomass increased with increasing water availability when the GSP/AccT ratio was lower than the threshold level of 0.80–0.84, but
decreased when the GSP/AccT ratio was higher than this threshold level. No significant relationship was found between residuals of above-ground biomass and species richness after removing the effects of climate factors on both stand variables.
Conclusions: The results support our hypotheses, further suggesting a threshold ofwater limitation that is consistent with themodel prediction over the Tibetan Plateau. Species richness per se appears to weakly affect community-level productivity. The response of alpine grasslands to climate warming may vary with altitude because of altitudinal shifts in factors limiting plant growth.

Keywords: Alpine grassland; Biomass; Functional groups; Leaf water potential; Net primary productivity;
Plant–climate interactions; Species richness

Causes for the unimodal pattern of biomass and productivity in alpine grasslands along a large altitudinal gradient in semi-arid regions

Biomass and net primary productivity (NPP) are important factors for studying terrestrial carbon storage and the carbon cycle. Using data from existing literature, this study synthesized and analyzed a comprehensive database of direct field observations of forest biomass and NPP for Southwestern China. The biomass of mature natural forests and mature planted forests range from 81.2 Mg·ha−1 to 692.6 Mg·ha−1 (mean = 288.1 Mg·ha−1) and from 76.8 Mg·ha−1 to 670.1 Mg·ha−1 (mean = 181.5 Mg·ha−1), respectively. Mature natural forests have higher biomass than mature planted ones. The NPP values of natural and planted forests range from 1.4 Mg·ha−1·year−1 to 29.6 Mg·ha−1·year−1 (mean = 13.6 Mg·ha−1·year−1) and from 0.6 Mg·ha−1·year−1 to 26.5 Mg·ha−1·year−1 (mean = 9.9 Mg·ha−1·year−1), respectively. Correlations among biomass, NPP, and environmental factors show that NPP significantly decreases with latitude and increases with mean annual temperature, mean annual precipitation, growing degree-days on a 0 °C base, and mean annual drought index, whereas biomass positively correlates with stand age and leaf area index strongly. Karst forests exhibit almost the same NPP as non-karst forests, but the former have significantly lower biomass compared to the latter. Comprehensive regional data synthesis and analysis based on direct field observations of forest biomass and NPP are important for benchmarking global and regional vegetation and carbon models, estimating regional carbon content, restoring vegetation, and mitigating climate change.

https://www.mdpi.com/1999-4907/7/8/173/pdf

Forest Biomass and Net Primary Productivity in Southwestern China: A Meta-Analysis Focusing on Environmental Driving Factors

Observation and simulation of net primary productivity in Qilian Mountain, western China.

Forest ecosystems play an important role in the global cycling of mercury (Hg). In this study, we characterized the Hg cycling at a remote evergreen broadleaf (EB) forest site in southwest China (Mount Ailao). The annual Hg input via litterfall is estimated to be 75.0 ± 24.2 µg m−2 yr−1 at Mount Ailao. Such a quantity is up to 1 order of magnitude greater than those observed at remote temperate/boreal (T/B) forest sites. Production of litter biomass is found to be the most influential factor causing the high Hg input to the EB forest. Given their large areal coverage, Hg deposition through litterfall in EB forests is appropriately 9 ± 5 Mg yr−1 in China and 1086 ± 775 Mg yr−1 globally. The observed wet Hg deposition at Mount Ailao is 4.9 ± 4.5 µg m−2 yr−1, falling in the lower range of those observed at 49 T/B forest sites in North America and Europe. Given the data, the Hg deposition flux through litterfall is approximately 15 times higher than the wet Hg deposition at Mount Ailao. Steady Hg accumulation in decomposing litter biomass and Hg uptake from the environment were observed during 25 months of litter decomposition. The size of the Hg pool in the organic horizon of EB forest floors is estimated to be up to 2–10 times the typical pool size in T/B forests. This study highlights the importance of EB forest ecosystems in global Hg cycling, which requires further assessment when more data become available in tropical forests.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016JG003446

Enhanced accumulation and storage of mercury on subtropical evergreen forest floor: Implications on mercury budget in global forest ecosystems

Aim Our aim was to investigate how the average life span of canopy leaves might be used to predict the geographical distribution of natural forests at large geographical scales, and to explore the link between leaf characteristics and ecosystem functioning. We examine whether there is a general relationship between canopy mean leaf life span and climate (i.e. temperature and precipitation) that can be used to predict evergreen forest zonation in China. Location Forest areas in China. Methods During July and August of 2002-2004, we conducted a latitudinal forest transect spanning about 30 degrees of latitude in eastern China. The canopy mean leaf life span was calculated to include all tree species (groups) in each forest plot through weighted averages scaled up from branch-level measurements. Data from our previous work conducted in the Tibetan Alpine Vegetation Transects (TAVT) and from other investigators were compiled to supplement our results. Based on regression equations developed on the pooled data, and using gridded temperature and precipitation datasets, we simulated the distribution of canopy mean leaf life span for forests in China. The predicted leaf life span zonation was compared with a map of Chinese forest vegetation divisions published in 1980. Results Canopy mean leaf life span across 10 evergreen forest plots in eastern China showed a decreasing trend as mean annual temperature increased, following a common logistic pattern consistent with the data from the TAVT and other investigators. In pooled data for 40 evergreen forest plots across tropical and boreal regions, canopy mean leaf life span generally showed a negative relationship with mean annual temperature (r2 = 0.72, P 8 degrees C (r2 = 0.45, P < 0.01). The climate-based simulations of leaf life span zonation compared well with the previously published boundaries of forest vegetation divisions in eastern China. Main conclusions Our results reveal that mean leaf life span in evergreen forests follows a common logistic pattern associated with mean annual temperature and precipitation, which can in turn be used to predict evergreen forest zonation in eastern China.

Leaf life span as a simple predictor of evergreen forest zonation in China.

By the methods of sampling plot harvesting method and allometric dimension analysis, we measured the belowground and aboveground standing biomass and net primary productivity (NPP) of the secondary evergreen broadleaved forest in Huangmian Forest farm of Guangxi, southern China, with the location of 24 degrees 51'N and 109 degrees 51'E and an altitude of about 315 m. The total biomass was 99.96 t x hm(-2), aboveground and belowground biomasses accounted for 69.41% and 30.59%, respectively. The leaf area index of trees and undergrowth shrubs was 6.50, and the total annual NPP was 24.65 t x hm(-2) x yr(-1) by estimate, aboveground and belowground NPP accounted for 44.54% and 55.46%, respectively. The NPP of fine roots was 11.79 t x hm(-2) x yr(-1), being 86.24% of the belowground NPP.

[Biomass and net primary productivity of secondary evergreen broadleaved forest in Huangmian Forest Farm, Guangxi].

With average-tree-specific sampling method, the authors measured the root biomass of Pinus yunnanensis forests with different stand ages in Yongren County, Yunnan Province. The results indicated that total root biomass increased from 8.50 t x hm(-2) in young stand (15-17 yr) to 11.70 t x hm(-2) in middle-aged stand (30-32 yr), and to 18.91 t x hm(-2) in mature stand (60-130 yr). Among different stand age classes, the biomass of coarse roots (>10 mm) varied greatly (1.5-12.3 t x hm(-2)), whereas those of medium (5-10 mm) and fine (<5 mm) roots showed less variation (medium roots 1.4-1.6 t x hm(-2), fine roots 5.3-6.2 t x hm(-2)). The root biomass of mature stand decreased with soil depth, approximately 93% of total underground biomass being distributed in surface layer (0-30 cm), and only 7% in deeper layer (30-115 cm).

[Root biomass of different stand-age Pinus yunnanensis forests and its distribution pattern in different soil depths].

In the new power environment, it is necessary to consider both the power supply reliability of the urban medium-voltage distribution network, and also to maintain the robustness of the distribution network to the operation risks. This paper proposes a “N-1+1” model for the reliability analysis of medium voltage distribution network. And this paper solves the “N-1+1” problem with the improved discrete monkey algorithm (DMA). Finally, the conclusion proves that the N-1+1 ” model can guarantee the power supply reliability and provide the robustness to risk.

Kunmei Deng

Papers

Leaf life span as a simple predictor of evergreen forest zonation in China.

[Biomass and net primary productivity of secondary evergreen broadleaved forest in Huangmian Forest Farm, Guangxi].

[Root biomass of different stand-age Pinus yunnanensis forests and its distribution pattern in different soil depths].

The “N-1+1” Distribution Reconstruction Method Based on the Discrete Monkey Algorithm