Aging Mongolian pine plantations face high risks of drought-induced growth decline:evidence from both individual tree and forest stand measurements

Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas.An important species for afforestation in dry environments of northern China,Mongolian pine(Pinus sylvestris var.mongolica Litv.)has recently exhibited growth decline and dieback on many sites,particularly pronounced in old-growth plantations.However,changes in response to drought stress by this species with age as well as the underlying mechanisms are poorly understood.In this study,tree-ring data and remotely sensed vegetation data were combined to investigate variations in growth at individual tree and stand scales for young(9-13 years)and aging(35-52 years)plantations of Mongolian pine in a water-limited area of northern China.A recent decline in tree-ring width in the older plantation also had lower values in satellited-derived normalized difference vegetation indices and normalized difference water indices relative to the younger plantations.In addition,all measured growth-related metrics were strongly correlated with the self-calibrating Palmer drought severity index during the growing season in the older plantation.Sensitivity of growth to drought of the older plantation might be attributed to more severe hydraulic limitations,as reflected by their lower sapwood-and leaf-specific hydraulic conductivities.Our study presents a comprehensive view on changes of growth with age by integrating multiple methods and provides an explanation from the perspective of plant hydraulics for growth decline with age.The results indicate that old-growth Mongolian pine plantations in water-limited environments may face increased growth declines under the context of climate warming and drying.

Growth simulation and yield prediction for perennial jujube fruit tree by integrating age into the WOFOST model

Mathematical models have been widely employed for the simulation of growth dynamics of annual crops,thereby performing yield prediction,but not for fruit tree species such as jujube tree(Zizyphus jujuba).The objectives of this study were to investigate the potential use of a modified WOFOST model for predicting jujube yield by introducing tree age as a key parameter.The model was established using data collected from dedicated field experiments performed in 2016-2018.Simulated growth dynamics of dry weights of leaves,stems,fruits,total biomass and leaf area index(LAI) agreed well with measured values,showing root mean square error(RMSE) values of 0.143,0.333,0.366,0.624 t ha^-1 and 0.19,and R2 values of 0.947,0.976,0.985,0.986 and 0.95,respectively.Simulated phenological development stages for emergence,anthesis and maturity were 2,3 and 3 days earlier than the observed values,respectively.In addition,in order to predict the yields of trees with different ages,the weight of new organs(initial buds and roots) in each growing season was introduced as the initial total dry weight(TDWI),which was calculated as averaged,fitted and optimized values of trees with the same age.The results showed the evolution of the simulated LAI and yields profiled in response to the changes in TDWI.The modelling performance was significantly improved when it considered TDWI integrated with tree age,showing good global(R2≥0.856,RMSE≤0.68 t ha^-1) and local accuracies(mean R2≥0.43,RMSE≤0.70 t ha^-1).Furthermore,the optimized TDWI exhibited the highest precision,with globally validated R2 of 0.891 and RMSE of 0.591 t ha^-1,and local mean R2 of 0.57 and RMSE of 0.66 t ha^-1,respectively.The proposed model was not only verified with the confidence to accurately predict yields of jujube,but it can also provide a fundamental strategy for simulating the growth of other fruit trees.

Tree Age Affects Postharvest Attributes and Mineral Content in Amrapali Mango(Mangifera indica) Fruits

The study was carried out to investigate the effect of tree age on postharvest attributes and mineral content of Amrapali mango fruits. Effect of 3 different tree ages(6, 18 and 30 years) on functional components, including the antioxidant activity(AOX), total phenols, total carotenoids,ascorbic acid and minerals like Ca, K, Mg, Fe, Zn, Cu, Mn and B along with total sugars, total soluble solids(TSS) and titratable acidity(TA),respiration rate, polygalacturonase(PG) and pectin methylesterase(PME) activities in Amrapali cultivar were studied. With tree ageing total phenols, ascorbic acid and antioxidant activity decreased whereas total carotenoids increased. Ca diminished and K elevated with the tree age progression while, B, Fe, Cu, Zn, and Mn showed an indefinite pattern. Total soluble solids and total sugars were recorded higher in 18 year old tree fruits. Fruit respiration rate, polygalacturonase and pectin methylesterase activities showed an upward trend with tree ageing. The study indicates that fruit produced from middle age group mango orchard(18 year old) suits to the requirement of consumers as well as industry.

Assessment of tree-ring mercury radial translocation and age effect in Masson pine:Implications for historical atmospheric mercury reconstruction

The tree ring has been regarded as an emerging archive to reconstruct historical atmospheric mercury(Hg)trends,but with the large knowledge gaps in the reliability.In this study,we comprehensively evaluated the Hg source,radial translocation and age effect of Masson pine(Pinus massoniana)tree ring at Mt.Jinyun in Chongqing,to assess the suitability of such tree ring as the archive of atmospheric Hg.Results showed that distinct variabilities among Masson pine tree-ring Hg concentration profiles.The Hg concentration significantly increased along with stem height(P<0.05),indicating the Hg in tree rings mainly derived from foliage uptake atmospheric Hg.We found a distinct age effect that the tree ring of young trees had the higher Hg concentration.Besides,we used the advection-diffusion model to demonstrate how Hg concentration shifted by the advection or/and diffusion in tree rings.The modeling results showed that the advection induced radial translocation during the young growth period of tree was a plausible mechanism to result in the tree-ring Hg record largely different from the trend of anthropogenic Hg emissions in Chongqing.We finally suggest that in further Hg dendrochemistry,better discarding the tree-ring Hg profile of the young growth period to reduce impacts of the radial translocation and age effect.

Stability evaluation of radial growth of Picea schrenkiana in different age groups in response to climate change in the eastern Tianshan Mountains

Global warming causes an unstable response in tree radial growth at high latitudes in the Northern Hemisphere.Additionally,different climatic responses of different age groups of trees have been found due to their different physiological mechanisms.In this study,the response stability and growth trend of three age groups(young<100 a,middle 100-200 a,old≥200 a)of Picea schrenkiana(Schrenk spruce)to climate change and the causes of the different responses in different age groups were analyzed in the relatively dry climate of the eastern Tianshan Mountains.The results showed that:(1)With the abrupt increase in temperature in 1989,the annual mean minimum temperature became the dominant radial growth-limiting factor of the three age groups of Schrenk spruce.(2)The radial growth of the middle and young groups was more sensitive than that of the old group based on growth-climate correlation analysis.(3)The radial growth of the different age groups had different responses to climate factors,and all age groups were unstable on time scales.(4)The trend of the linear regression simulation of the basal area increment(BAI)indicated that the Schrenk spruce had the same growth trends in different age groups with growth first increased and then decreased;however,the decreased growth rate was higher in the middle and young age groups than in the old age group after the abrupt increase in temperature.Therefore,we should pay active attention to the impact of drought on Schrenk spruce in the eastern Tianshan Mountains and should particularly strengthen the conservation and management of the middle and young age groups.

Activities of some defense proteins associated with age or plant family in larch needles of Larix olgensis and L. kaempferi× L. gmelinii

Defence proteins are a kind of chemical defence compounds. They play a key role in plant restraining biotic and abiotic harm. To illuminate activities of some defense proteins associated with age or plant family of larch, the larch needles were collected from two different families of Korean larch, Larix olgensis and a hybrid larch, L. kaempferi × L. gmelinii, respectively, and then the activities of defence proteins in those were tested using a UV spectrophotometry. The results showed that the activities of protective enzymes at thel6-/17- and 19-year-age groups were higher than those at the other age groups in the both larch species. While the activities of polyphenol oxidase （PPO） at the 16-/17-year-age group and phenylalanine ammonia-lyase （PAL） and protease inhibitors at the 19-year-age group were the highest among all age groups. Then, compared with L. olgensis, the hybrid larch had significant effects on the activities of protective enzymes. The effects of plant family on the activities of PAL and chymotrypsin inhibitor were significantly different, and then those on the activities of PPO were not significantly different. The effects of the two families in L. olgensis on the activities of trypsin inhibitor （TI） were significantly different, while those in the hybrid larch on the activities of TI were contrary. To conclusions showed that the different age and plant family significantly affected the activities of defence proteins in the needles of two larch species, and then enhanced the larch resistance to pests. These could play a key function in forestry tree genetic improvement and management in future.

CPSDv0: a forest stand structure database for plantation forests in China

Forest stand structure is not only a crucial factor for regulating forest functioning but also an important indicator for sustainable forest management and ecosystem services.Although there exists a few national/global structure databases for natural forests,a country-wide synthetic structure database for plantation forests over China,the world’s largest player in plantation forests,has not been achieved.In this study,we built a country-wide synthetic stand structure database by surveying more than 600 peer-reviewed literature.The database covers tree species,mean stand age,mean tree height,stand density,canopy coverage,diameter at breast height,as well as the associated ancillary in-situ topographical and soil properties.A total of 594 pub-lished studies concerning diverse forest stand structure parameters were compiled for 46 tree species.This first synthesis for stand structure of plantation forests over China supports studies on the evolution/health of plantation forests in response to rapid climate change and intensified disturbances,and benefits country-wide sustainable forest management,future afforestation or reforestation planning.Potential users include those studying forest community dynamics,regional tree growth,ecosystem stability,and health,as well as those working with conservation and sustainable management.This dataset is freely acces-sible at http://www.doi.org/10.11922/sciencedb.j00076.00091.

Ontogenetic transition in leaf traits: a new cost associated with the increase in leaf longevity

Aims Recent work has identified a worldwide‘economics’spectrum of correlated leaf traits that mainly reflects the compromises between maximizing leaf longevity and short-term productivity.However,during the early stages of tree growth different species tend to exhibit a common strategy,because competition for soil water and nutrients forces the maximization of short-term productivity owing to the need for rapid growth during the most vulnerable part of the tree’s life cycle.Accordingly,our aim here was to compare the variations that occur during ontogeny in the different leaf traits(morphology and leaf chemical composition)of several coexisting Mediterranean woody species differing in their leaf life spans and to test our hypothesis that tree species with a long leaf life span should exhibit larger shifts in leaf characteristics along ontogeny.Methods Six Mediterranean tree species differing in leaf life span,selected from three plots located in central-western Spain,were studied during three growth stages:seedlings,juveniles and mature trees.Leaf life span,leaf morphology(leaf area,dry weight,thickness and mass per unit area)and chemical composition(N and fibre con-centrations)were measured in all six species.The magnitude of the ontogenetic changes in the different traits was estimated and related to the mean leaf longevity of the different species.Important Findings Along ontogeny,strong changes were observed in all variables analysed.The early growth stages showed lower leaf thickness,leaf thickness and mass per unit area and N,cellulose and hemi-cellulose concentrations than mature trees,but a higher lignin content.However,these changes were especially marked in species with a longer leaf life span at maturity.Interspecific dif-ferences in leaf life span,leaf morphology and chemical com-position were stronger at the mature stage than at the seedling stage.We conclude that greater plasticity and more intense strat-egy shifts along ontogeny are necessarily associated with long leaf life span.Our results thus provide a new aspect that should be incorporated into the analysis of the costs and benefits associ-ated with the different strategies related to leaf persistence dis-played by the different species.Accordingly,the intensity of the alterations in leaf traits among different growth stages should be added to the suite of traits that change along the leaf economics spectrum.