Drought has been one of the most important limiting factors for crop production, which deleteriously affects food security worldwide. The main objective of the present study was to quantitatively assess the effect of drought on the agronomic traits (e.g., plant height, biomass, yield, and yield components) of rice and wheat in combination with several moderators (e.g., drought stress intensity, rooting environment, and growth stage) using a meta-analysis study. The database was created from 55 published studies on rice and 60 published studies on wheat. The results demonstrated that drought decreased the agronomic traits differently between rice and wheat among varying growth stages. Wheat and rice yields decreased by 27.5% and 25.4%, respectively. Wheat grown in pots showed greater decreases in agronomic traits than those grown in the field. Rice showed opposite growing patterns when compared to wheat in rooting environments. The effect of drought on rice increased with plant growth and drought had larger detrimental influences during the reproductive phase (e.g., blooming stage, filling stage, and maturity). However, an exception was found in wheat, which had similar decreased performance during the complete growth cycle. Based on these results, future droughts could produce lower yields of rice and wheat when compared to the current drought.

Persistent drought severely inhibits plant growth and productivity, which negatively affects terrestrial primary productivity worldwide. Therefore, it is important to investigate the impacts of drought on plant leaf CO₂/H₂O exchange and water use efficiency. This study assessed the responses of net photosynthesis (Pn), stomatal conductance (Gs), transpiration (Tr), and instantaneous water use efficiency (WUE) to drought based on a worldwide meta-analysis of 112 published studies. The results demonstrated that drought decreased Pn, Tr, and Gs significantly and differently among different moderators. C₄ plants had smaller Pn reduction than C₃ plants, which gives C₄ plants an advantage in Pn. But their WUE decreased under drought conditions, indicating a great flexibility in C₄ WUE. Annual herbs sacrificed WUE (−6.2%) to maintain efficient Pn. Perennial herbs took a different strategy in response to drought with an increased WUE (25.1%). Deciduous tree species displayed a greater increase in WUE than conifers and evergreen species. Additionally, Gs had a significant correlation with Pn and Tr, but an insignificant correlation with WUE, which could be because WUE is affected by other factors (e.g., air flow, CO₂ concentration, and relative humidity). These findings have significant implications for understanding the worldwide effects of drought on plant leaf CO₂/H₂O exchange and water use efficiency.

The Laoshan forest is the largest forest in Nanjing, and it plays an important role in water resource management in Nanjing. The objectives of this study are to determine if the temperature vegetation dryness index (TVDI) is suitable to estimate the soil moisture and if soil moisture is significantly affected by tree species in the Laoshan forest. This paper calculated the spatial distribution of TVDI using LANDSAT-5 TM data. Sixty-two observation points of in situ soil moisture measurements were selected to validate the effectiveness of the TVDI as an index for assessing soil moisture in the Laoshan forest. With the aid of the three different temporal patterns, which are 10 January 2011, 18 May 2011 and 23 September 2011, this paper used the TVDI to investigate the differences of soil moisture under four kinds of mono-species forests and two kinds of mixed forests. The results showed that there is a strong and significant negative correlation between the TVDI and the in situ measured soil moisture (R² = 0.15–0.8, SE = 0.015–0.041 cm³/cm³). This means that the TVDI can reflect the soil moisture status under different tree species in the Laoshan forest. The soil moisture under these six types of land cover from low to high is listed in the following order: Eucommia ulmoides, Quercus acutissima, broadleaf mixed forest, Cunninghamia lanceolata, coniferous and broadleaf mixed forest and Pinus massoniana.

The present work aims to detect bamboo expansion and its impact on carbon storage in a thick forest in the most recent 30 years. The research area is the national nature reserve of Tianmushan, Zhejiang Province, China, and the present paper monitored bamboo expansion from 1984 to 2015. Multi-spectral band and vegetation indices from Landsat images in summer and winter are used combined to improve the accuracy of detection using a support vector machine (SVM) classifier. Expansion of bamboo over this period is evident. Total expansion is 161%, the fastest annual rate being 11.6%. However, over recent decades the growth of bamboo has been inhibited by human activity and the total area has decreased by 21%. Evergreen broadleaf forest is the most vulnerable to invasion by bamboo at a ratio of about 65%, and this expanding trend has been brought under effective control. Carbon storage was estimated using sample plot surveys and modelling based on key ecological forests. According to our estimation using carbon storage models, the total carbon storage of Tianmushan has declined by circa 4.7% due to bamboo expansion in the past three decades.

Frequent flash droughts can rapidly lead to water shortage, which affects the stability of ecosystems. This study determines the water-use characteristics and physiological mechanisms underlying Moso bamboo response to flash-drought events, and estimates changes to water budgets caused by extreme drought. We analyzed the variability in forest canopy transpiration versus precipitation from 2011–2013. Evapotranspiration reached 730 mm during flash drought years. When the vapor pressure deficit > 2 kPa and evapotranspiration > 4.27 mm·day⁻¹, evapotranspiration was mainly controlled through stomatal opening and closing to reduce water loss. However, water exchange mainly occurred in the upper 0–50 cm of the soil. When soil volumetric water content of 50 cm was lower than 0.17 m³·m⁻³, physiological dehydration occurred in Moso bamboo to reduce transpiration by defoliation, which leads to water-use efficiency decrease. When mean stand density was <3500 trees·ha⁻¹, the bamboo forest can safely survive the flash drought. Therefore, we recommend thinning Moso bamboo as a management strategy to reduce transpiration in response to future extreme drought events. Additionally, the response function of soil volumetric water content should be used to better simulate evapotranspiration, especially when soil water is limited.

Accurate and timely information describing wetland resources and their changes over time, especially in coastal urban areas, is becoming more important. In this study, we mapped and monitored land-cover change in an urban wetland using high spatial resolution IKONOS images acquired in June 2003 and January 2006. An optimal iterative unsupervised classification (OIUC) method was used to overcome the limitations of unsupervised classification. The images were categorized into six classes, and an accuracy assessment was conducted using error matrices and the Kappa coefficient. The overall accuracies were 83.2% and 86.3% for the 2003 and 2006 images, respectively. A post-classification comparison method was used to detect the wetland change by calculating a detailed land-cover type transformation matrix. The results indicated a decrease in the area of water bodies and an increase in the area of vegetation in the wetland. This paper shows that high spatial resolution remote sensing data is advanced in studying an urban wetland at a local scale. An OIUC method, combined with visual interpretation, could yield high classification accuracy. A post-classification comparison method is also efficient in wetland change detection.