Qinglong County in Guizhou, China is a typical karst canyon area. Using quadrat methods and a land use transfer matrix we studied the carbon storage spatial distribution pattern and evolution process over three independent periods (1988, 1999 and 2009) in this area. Based on the results we estimated the carbon pool capacity of the entire karst canyon area in Guizhou and contribution ratios. Carbon storage and average carbon density of the karst area in Qinglong decreased at first, and then increased over the sampling period. The actual carbon storage of the karst canyon area in Guizhou was estimated to be 42.55 Tg. The average carbon intensity of the karst canyon area in Guizhou is far higher than that of national terrestrial ecosystems, especially in vegetation areas. Through cross comparison, we found that karst canyon areas have great carbon sequestration potential and we suggest that it is necessary to control and prevent rocky desertification in karst areas in China.

Natural karst forests can support very high level of biodiversity, but difference of species diversity between the natural karst forests and non-karst forests is still less concerned. To analyze the difference of species diversity of the natural karst forests and non-karst forests in subtropics, we made a census of all woody species with diameter at breast height (dbh)≥1 cm in a 1-ha plot in Mulun subtropical karst forests and a 1-ha plot in Maoershan subtropical non-karst forests, Guangxi of south-western China. Species richness in Mulun plot (120 species) was higher than that in Maoershan plot (116 species). Mulun plot contained more families and genera, more stems and a larger proportion of rare species (species of individuals less than or equal to 1 ha^-1). At smaller scale (<4000 m²), species accumulation rate in Mulun plot was lower than that in Maoershan plot, and it was reversed at larger scale (>5000 m²). Total basal area in Mulun plot (18.47 m²) was smaller than that in Maoershan plot (30.74 m²). Size structure distribution of all woody species in the two plots showed insignificant difference. The ten most dominant species, families and genera were quite different in the two plots. In Mulun plot, the most important species and family were Sinosideroxylon wightianum and Sapindaceae, while in Maoershan plot, Castanopsis carlesii and Fagaceae were the most important species and family. All these results suggest that middle subtropical natural karst forest in Mulun supports diverse species with high spatial variability, and their species composition are quite different with non-karst forests. This study implies that special attention is needed on selecting suitable species in karst forest restoration and vegetation management strategies.

Limestone soil is a poor quality soil with a low rate of nutrient supply due to the accumulation of organic carbon. Here, we examined the degradation of maize straw in limestone soil and red soil using indoor simulation. Dynamic testing was conducted on soil chemical properties and soil fertility. We found that the degradation rate of straw in karst soil is higher than for non-karst soil. The highest degradation rate of straw occurred during the first 60 d, after which it rose slowly and balanced out at 98 d. The peak value of degradation of straw in karst soil was found at 28 d, while that in non-karst soil occurred at 42 d. The total period of degradation lasted 160 d; the degradation rate of straw in karst soil and non-karst soil was 77% and 75%, respectively. During the period of straw degradation, the pH of soil tended to decrease in the early stage and rise slowly in later stages and this is consistent with the pattern of degradation products during different stages of straw degradation. Straw return to fields can increase soil fertility, and the growth rate of available N and K content is significant. Compared to karst soil, the content of various fertility indicators in non-karst areas were lower according to total content tests, although the increase (percentage) in nonkarst area was higher; available P and K content were found to be higher in non-karst areas according to availability tests. Some available nutrients in straw return can be more readily released in non-karst soil, while karst soil can contribute to the accumulation of total nutrient content due to its special soil texture features, the firm binding of many nutrients with clay minerals and the slow supply of nutrients.

Limestone soil in karst areas is the product of weathering and carbonate rock dissolution in tropical and subtropical regions. Limestone soil in karst regions has a Ca-rich alkaline geochemical environment, but the characteristics of calcium speciation in limestone soil remain unclear. Here, to study changes in calcium speciation in soil across seasons in a karst area, different geomorphological positions and soil samples were collected from the Yaji karst experimental site. Using European Community Bureau of Reference (BCR) methods, we analyzed and discuss soil calcium speciation and seasonal migration characteristics. We found that total soil Ca content was 2.80–11.75 g kg^-1, with an average of 5.25±0.68 g kg^-1 (mean±SE). The order of content of each Ca speciation is extractable-Ca>reducible-Ca>residual-Ca>oxidizable-Ca. In addition to oxidizable-Ca, other Ca species had a positive correlation with total calcium. The calcium content and various forms of calcium content decreased gradually with changing season, but in addition to differences in residual calcium across seasons, total calcium and other forms of calcium across seasons were not different. Total calcium and different forms of calcium content were highest at sloped areas; slopes and other landforms were different but differences between plain, saddle and depression areas were not significant.

Thirty-four sampling sites for surface water and twenty-seven sampling sites for ground water in areas of different land use were selected in the Wujiang River Basin, upstream section in Guizhou Province, China. Carbonic anhydrase (CA) activity in surface and ground water was analyzed and compared. The results show that CA activity was detected in all surface and ground water samples. In general, average CA activity in surface and ground water was highest from samples in arbor lands, followed by shrub lands, shrub and grass lands, agricultural lands, and residential areas. The average CA activity in ground water from arbor lands, shrub lands, and shrub and grass lands was higher than that in surface water. Water CA activity was positively correlated with HCO₃^- concentration in surface water and ground water. These results imply that the contribution of CA in water to the karst carbon sink potential of river basins warrants further extensive and in-depth research.

The darkness, humidity and constant temperature of subterranean karst caves have produced specialized populations of animals with, unique behaviors and characteristics. Based on living habits, troglofauna can be divided into troglobites, troglophiles and trogloxenes. Since the beginning of research on karst troglofauna in China in the late 1970s, 131 new species of troglofauna have been discovered. A large amount of research has been conducted on the behavior and characteristics of troglofauna, and good progress has been made over the last few decades. Nevertheless, in view of the wide distribution and large quantity of karst caves throughout China, there remains much potential for futher research on Chinese troglofauna.

Karst areas in Southwest China, with Guizhou as the focal center, are confronted with ecological deterioration and large areas of rocky desertification. Human activities are defined as the driving force behind the soil erosion. Further, local farmers in the area suffer from poverty due to a lack of drinking water, food and a weak living environment. Over one-third of national poverty-stricken counties occur in this part of China. To balance ecological protection and economic development in the region and help local farmers out of poverty we propose integrated controls and discuss on ground water exploration and sustainable use, soil conservation and remediation, and vegetation restoration (especially economic plant species) in this paper.

Dendrogeomorphological method was used to study soil erosion in two typical karst sites (Puding and Zhengfeng) in Guizhou Province, China. Eleven pairs of exposed and unexposed tree roots were measured in the field and sampled for anatomical characteristics. The results showed that the exposed roots recorded karst soil erosion. Significant changes were shown in the anatomical characteristics of the exposed tree roots when soil erosion occurred, such as suddenly narrower tree rings, smaller cells, and fewer earlywood cells. Meanwhile, the fabre lumen and vessel lumen areas markedly declined to the range of 39.20% to 70.66%, which only slightly implies soil erosion. The accurate time period during which soil erosion occurred was identified and combined with the age of the tree roots. Dynamics of soil erosion were calculated and soil erosion recorded by the exposed roots from 2002 to 2007 at an average rate of 0.484 t y^-1 at Puding, and from 2005 to 2007 at an average rate of 0.051 t y^-1 at Zhenfeng. Karst soil erosion was recorded by not only one species but by multi species of broadleaf tree roots, which can significantly enhance the study of karst soil erosion through the use of Dendrogeomorphological method. The quantity of eroded soil was found to be extremely large when records from the exposed tree roots were compared with estimates from site measurements of runoff. The major type of karst soil erosion was underground soil loss and this comprised approximately 2/3 of total erosion.

In this paper, responses of germination physiology of pigeon pea (Cajanus cajan) seeds to drought stress in karst water environment and non-karst (allogenic) water environment were studied to explore the adaptability of pigeon pea to karst environment. The results showed that: (i) Under drought stress of 20% PEG-6000, the germination rate, vigor index, germination index and biomass of pigeon pea seeds on day 7 cultivated with karst water were all greater than that of the allogenic water treatment group, while the seed germination stress index was significantly smaller than that of the allogenic water treatment group, suggesting that karst water environment was more favorable to pigeon pea seed germination, (ii) Without drought stress, the malondialdehyde (MDA) and superoxide dismutase (SOD) activities of pigeon pea seeds cultivated with karst water were all smaller than that of the allogenic water group. However, under drought stress, the SOD activity was significantly higher than that of allogenic water group, suggesting pigeon pea SOD in karst water was able to more rapidly respond to external drought stress, and increase its own activity to reduce the damage to the plants. And (iii) with and without drought stress, the soluble protein level of the karst water group was higher than that of the allogenic water group, while the free amino acid level was lower than that of the allogenic water group. This difference was more significant with the presence of drought stress, suggesting that the karst water environment was more favorable to the accumulation of soluble proteins and thus produced larger biomass. Hence, pigeon pea is a tree species that is adapted to high-calcium, alkaline environments in karst areas, and is of great significance for the revegetation and rocky desertification control in mountainous karst areas.

Dragon fruit (Hylocereus undulates) was planted in a large area of karst region in recent years. To understand whether karst drought may impact on its physiological process is important and useful for planning and management of this fruit. In this study, we contrasted with a relative species Hylocereus undatus, and set up experiment to study physiological and biochemical trait and its response to different karst soil water level deficiency, so as to understand the mechanism of H. undulates and H. undatus in adaptation to karst drought condition. The results showed that, trends of physiological and biochemical response to drought was similar between two species. With the intensive of soil water deficiency, such toxin substance as malonaldehyde (MDA) increased, but meanwhile, two protective enzymes superoxide dismutase (SOD) and peroxidases (POD) and osmotic adjustment Proline (Pro) increase as well. Under relative water content (RWC) >50% condition, the enzyme can effectively protect the cells from toxin MDA injure, and Pro can also maintain the water needs through osmotic adjustment. However, under RWC < 40% condition, protective enzymes were not enough for cleaning MDA. Biomass was largest under RWC=70%–80%, with low root shoot ratio and high aboveground biomass. Biomass significantly decreased under RWC 30%–40%, which decline by 73.28% and 73.56% in H. undulates and H. undatus respectively. Therefore, RWC=70%–80% would be an optimal soil moisture while developing dragon fruit in karst, which is favor to fruit production. Under moderate drought e.g. RWC=50%-60%, plants may regulate by metabolic process and balance unfavorable substance, but it allocated much more biomass to root, reduced the aboveground biomass, which is not advance for fruit production.

Due to the unique environment of karst landscapes, there are many uncertainties regarding the recovery of vegetation following human disturbance. Through standard wood parsing and growth ring investigation in Puding county in Guizhou province, China, we studied the process of vegetation restoration in karst areas. According to our results, during the recovery of karst vegetation height increases and ground diameter enlargement of tree layers occurred. Increases in the height and ground diameter followed logarithmic and growth curves, respectively. The development time of trees showed continuity, and growth points were randomly distributed. However, with large propagule quantities, vegetation can be directly restored and developed into a secondary high forest without a grass filling stage, and the recovery time is shortened.